Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

16 files changed, 7455 insertions, 0 deletions

diff --git a/src/libsystemd/sd-device/device-enumerator-private.h b/src/libsystemd/sd-device/device-enumerator-private.h
new file mode 100644
index 0000000..cf62fab
--- /dev/null
+++ b/src/libsystemd/sd-device/device-enumerator-private.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <stdbool.h>
+
+#include "sd-device.h"
+
+typedef enum MatchInitializedType {
+        MATCH_INITIALIZED_NO,     /* only devices without a db entry */
+        MATCH_INITIALIZED_YES,    /* only devices with a db entry */
+        MATCH_INITIALIZED_ALL,    /* all devices */
+        MATCH_INITIALIZED_COMPAT, /* only devices that have no devnode/ifindex or have a db entry */
+        _MATCH_INITIALIZED_MAX,
+        _MATCH_INITIALIZED_INVALID = -EINVAL,
+} MatchInitializedType;
+
+int device_enumerator_scan_devices(sd_device_enumerator *enumerator);
+int device_enumerator_scan_subsystems(sd_device_enumerator *enumerator);
+int device_enumerator_scan_devices_and_subsystems(sd_device_enumerator *enumerator);
+int device_enumerator_add_device(sd_device_enumerator *enumerator, sd_device *device);
+int device_enumerator_add_parent_devices(sd_device_enumerator *enumerator, sd_device *device);
+int device_enumerator_add_match_is_initialized(sd_device_enumerator *enumerator, MatchInitializedType type);
+int device_enumerator_add_match_parent_incremental(sd_device_enumerator *enumerator, sd_device *parent);
+int device_enumerator_add_prioritized_subsystem(sd_device_enumerator *enumerator, const char *subsystem);
+sd_device *device_enumerator_get_first(sd_device_enumerator *enumerator);
+sd_device *device_enumerator_get_next(sd_device_enumerator *enumerator);
+sd_device **device_enumerator_get_devices(sd_device_enumerator *enumerator, size_t *ret_n_devices);
+
+#define FOREACH_DEVICE_AND_SUBSYSTEM(enumerator, device)       \
+        for (device = device_enumerator_get_first(enumerator); \
+             device;                                           \
+             device = device_enumerator_get_next(enumerator))
diff --git a/src/libsystemd/sd-device/device-enumerator.c b/src/libsystemd/sd-device/device-enumerator.c
new file mode 100644
index 0000000..15c5c42
--- /dev/null
+++ b/src/libsystemd/sd-device/device-enumerator.c
@@ -0,0 +1,1194 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "sd-device.h"
+
+#include "alloc-util.h"
+#include "device-enumerator-private.h"
+#include "device-filter.h"
+#include "device-util.h"
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "set.h"
+#include "sort-util.h"
+#include "string-util.h"
+#include "strv.h"
+
+typedef enum DeviceEnumerationType {
+        DEVICE_ENUMERATION_TYPE_DEVICES,
+        DEVICE_ENUMERATION_TYPE_SUBSYSTEMS,
+        DEVICE_ENUMERATION_TYPE_ALL,
+        _DEVICE_ENUMERATION_TYPE_MAX,
+        _DEVICE_ENUMERATION_TYPE_INVALID = -EINVAL,
+} DeviceEnumerationType;
+
+struct sd_device_enumerator {
+        unsigned n_ref;
+
+        DeviceEnumerationType type;
+        Hashmap *devices_by_syspath;
+        sd_device **devices;
+        size_t n_devices, current_device_index;
+        bool scan_uptodate;
+        bool sorted;
+
+        char **prioritized_subsystems;
+        Set *match_subsystem;
+        Set *nomatch_subsystem;
+        Hashmap *match_sysattr;
+        Hashmap *nomatch_sysattr;
+        Hashmap *match_property;
+        Hashmap *match_property_required;
+        Set *match_sysname;
+        Set *nomatch_sysname;
+        Set *match_tag;
+        Set *match_parent;
+        MatchInitializedType match_initialized;
+};
+
+_public_ int sd_device_enumerator_new(sd_device_enumerator **ret) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *enumerator = NULL;
+
+        assert(ret);
+
+        enumerator = new(sd_device_enumerator, 1);
+        if (!enumerator)
+                return -ENOMEM;
+
+        *enumerator = (sd_device_enumerator) {
+                .n_ref = 1,
+                .type = _DEVICE_ENUMERATION_TYPE_INVALID,
+                .match_initialized = MATCH_INITIALIZED_COMPAT,
+        };
+
+        *ret = TAKE_PTR(enumerator);
+
+        return 0;
+}
+
+static void device_unref_many(sd_device **devices, size_t n) {
+        assert(devices || n == 0);
+
+        for (size_t i = 0; i < n; i++)
+                sd_device_unref(devices[i]);
+}
+
+static void device_enumerator_unref_devices(sd_device_enumerator *enumerator) {
+        assert(enumerator);
+
+        hashmap_clear_with_destructor(enumerator->devices_by_syspath, sd_device_unref);
+        device_unref_many(enumerator->devices, enumerator->n_devices);
+        enumerator->devices = mfree(enumerator->devices);
+        enumerator->n_devices = 0;
+}
+
+static sd_device_enumerator *device_enumerator_free(sd_device_enumerator *enumerator) {
+        assert(enumerator);
+
+        device_enumerator_unref_devices(enumerator);
+
+        hashmap_free(enumerator->devices_by_syspath);
+        strv_free(enumerator->prioritized_subsystems);
+        set_free(enumerator->match_subsystem);
+        set_free(enumerator->nomatch_subsystem);
+        hashmap_free(enumerator->match_sysattr);
+        hashmap_free(enumerator->nomatch_sysattr);
+        hashmap_free(enumerator->match_property);
+        hashmap_free(enumerator->match_property_required);
+        set_free(enumerator->match_sysname);
+        set_free(enumerator->nomatch_sysname);
+        set_free(enumerator->match_tag);
+        set_free(enumerator->match_parent);
+
+        return mfree(enumerator);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_device_enumerator, sd_device_enumerator, device_enumerator_free);
+
+int device_enumerator_add_prioritized_subsystem(sd_device_enumerator *enumerator, const char *subsystem) {
+        int r;
+
+        assert(enumerator);
+        assert(subsystem);
+
+        if (strv_contains(enumerator->prioritized_subsystems, subsystem))
+                return 0;
+
+        r = strv_extend(&enumerator->prioritized_subsystems, subsystem);
+        if (r < 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+_public_ int sd_device_enumerator_add_match_subsystem(sd_device_enumerator *enumerator, const char *subsystem, int match) {
+        Set **set;
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(subsystem, -EINVAL);
+
+        if (match)
+                set = &enumerator->match_subsystem;
+        else
+                set = &enumerator->nomatch_subsystem;
+
+        r = set_put_strdup(set, subsystem);
+        if (r <= 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+_public_ int sd_device_enumerator_add_match_sysattr(sd_device_enumerator *enumerator, const char *sysattr, const char *value, int match) {
+        Hashmap **hashmap;
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(sysattr, -EINVAL);
+
+        if (match)
+                hashmap = &enumerator->match_sysattr;
+        else
+                hashmap = &enumerator->nomatch_sysattr;
+
+        r = update_match_strv(hashmap, sysattr, value, /* clear_on_null = */ true);
+        if (r <= 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+_public_ int sd_device_enumerator_add_match_property(sd_device_enumerator *enumerator, const char *property, const char *value) {
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(property, -EINVAL);
+
+        r = update_match_strv(&enumerator->match_property, property, value, /* clear_on_null = */ false);
+        if (r <= 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+_public_ int sd_device_enumerator_add_match_property_required(sd_device_enumerator *enumerator, const char *property, const char *value) {
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(property, -EINVAL);
+
+        r = update_match_strv(&enumerator->match_property_required, property, value, /* clear_on_null = */ false);
+        if (r <= 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+static int device_enumerator_add_match_sysname(sd_device_enumerator *enumerator, const char *sysname, bool match) {
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(sysname, -EINVAL);
+
+        r = set_put_strdup(match ? &enumerator->match_sysname : &enumerator->nomatch_sysname, sysname);
+        if (r <= 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+_public_ int sd_device_enumerator_add_match_sysname(sd_device_enumerator *enumerator, const char *sysname) {
+        return device_enumerator_add_match_sysname(enumerator, sysname, true);
+}
+
+_public_ int sd_device_enumerator_add_nomatch_sysname(sd_device_enumerator *enumerator, const char *sysname) {
+        return device_enumerator_add_match_sysname(enumerator, sysname, false);
+}
+
+_public_ int sd_device_enumerator_add_match_tag(sd_device_enumerator *enumerator, const char *tag) {
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(tag, -EINVAL);
+
+        r = set_put_strdup(&enumerator->match_tag, tag);
+        if (r <= 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+int device_enumerator_add_match_parent_incremental(sd_device_enumerator *enumerator, sd_device *parent) {
+        const char *path;
+        int r;
+
+        assert(enumerator);
+        assert(parent);
+
+        r = sd_device_get_syspath(parent, &path);
+        if (r < 0)
+                return r;
+
+        r = set_put_strdup(&enumerator->match_parent, path);
+        if (r <= 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+_public_ int sd_device_enumerator_add_match_parent(sd_device_enumerator *enumerator, sd_device *parent) {
+        assert_return(enumerator, -EINVAL);
+        assert_return(parent, -EINVAL);
+
+        set_clear(enumerator->match_parent);
+
+        return device_enumerator_add_match_parent_incremental(enumerator, parent);
+}
+
+_public_ int sd_device_enumerator_allow_uninitialized(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, -EINVAL);
+
+        enumerator->match_initialized = MATCH_INITIALIZED_ALL;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+int device_enumerator_add_match_is_initialized(sd_device_enumerator *enumerator, MatchInitializedType type) {
+        assert_return(enumerator, -EINVAL);
+        assert_return(type >= 0 && type < _MATCH_INITIALIZED_MAX, -EINVAL);
+
+        enumerator->match_initialized = type;
+
+        enumerator->scan_uptodate = false;
+
+        return 1;
+}
+
+static int sound_device_compare(const char *devpath_a, const char *devpath_b) {
+        const char *sound_a, *sound_b;
+        size_t prefix_len;
+
+        assert(devpath_a);
+        assert(devpath_b);
+
+        /* For sound cards the control device must be enumerated last to make sure it's the final
+         * device node that gets ACLs applied. Applications rely on this fact and use ACL changes on
+         * the control node as an indicator that the ACL change of the entire sound card completed. The
+         * kernel makes this guarantee when creating those devices, and hence we should too when
+         * enumerating them. */
+
+        sound_a = strstrafter(devpath_a, "/sound/card");
+        if (!sound_a)
+                return 0;
+
+        sound_a = strchr(devpath_a, '/');
+        if (!sound_a)
+                return 0;
+
+        prefix_len = sound_a - devpath_a;
+
+        if (!strneq(devpath_a, devpath_b, prefix_len))
+                return 0;
+
+        sound_b = devpath_b + prefix_len;
+
+        return CMP(!!startswith(sound_a, "/controlC"),
+                   !!startswith(sound_b, "/controlC"));
+}
+
+static bool devpath_is_late_block(const char *devpath) {
+        assert(devpath);
+
+        return strstr(devpath, "/block/md") || strstr(devpath, "/block/dm-");
+}
+
+static int device_compare(sd_device * const *a, sd_device * const *b) {
+        const char *devpath_a, *devpath_b;
+        int r;
+
+        assert(a);
+        assert(b);
+        assert(*a);
+        assert(*b);
+
+        assert_se(sd_device_get_devpath(*(sd_device**) a, &devpath_a) >= 0);
+        assert_se(sd_device_get_devpath(*(sd_device**) b, &devpath_b) >= 0);
+
+        r = sound_device_compare(devpath_a, devpath_b);
+        if (r != 0)
+                return r;
+
+        /* md and dm devices are enumerated after all other devices */
+        r = CMP(devpath_is_late_block(devpath_a), devpath_is_late_block(devpath_b));
+        if (r != 0)
+                return r;
+
+        return path_compare(devpath_a, devpath_b);
+}
+
+static int enumerator_sort_devices(sd_device_enumerator *enumerator) {
+        size_t n_sorted = 0, n = 0;
+        sd_device **devices;
+        sd_device *device;
+        int r;
+
+        assert(enumerator);
+
+        if (enumerator->sorted)
+                return 0;
+
+        devices = new(sd_device*, hashmap_size(enumerator->devices_by_syspath));
+        if (!devices)
+                return -ENOMEM;
+
+        STRV_FOREACH(prioritized_subsystem, enumerator->prioritized_subsystems) {
+
+                for (;;) {
+                        const char *syspath;
+                        size_t m = n;
+
+                        HASHMAP_FOREACH_KEY(device, syspath, enumerator->devices_by_syspath) {
+                                _cleanup_free_ char *p = NULL;
+                                const char *subsys;
+
+                                if (sd_device_get_subsystem(device, &subsys) < 0)
+                                        continue;
+
+                                if (!streq(subsys, *prioritized_subsystem))
+                                        continue;
+
+                                devices[n++] = sd_device_ref(device);
+
+                                for (;;) {
+                                        _cleanup_free_ char *q = NULL;
+
+                                        r = path_extract_directory(p ?: syspath, &q);
+                                        if (r == -EADDRNOTAVAIL)
+                                                break;
+                                        if (r < 0)
+                                                goto failed;
+
+                                        device = hashmap_get(enumerator->devices_by_syspath, q);
+                                        if (device)
+                                                devices[n++] = sd_device_ref(device);
+
+                                        free_and_replace(p, q);
+                                }
+
+                                break;
+                        }
+
+                        /* We cannot remove multiple entries in the loop HASHMAP_FOREACH_KEY() above. */
+                        for (size_t i = m; i < n; i++) {
+                                r = sd_device_get_syspath(devices[i], &syspath);
+                                if (r < 0)
+                                        goto failed;
+
+                                assert_se(hashmap_remove(enumerator->devices_by_syspath, syspath) == devices[i]);
+                                sd_device_unref(devices[i]);
+                        }
+
+                        if (m == n)
+                                break;
+                }
+
+                typesafe_qsort(devices + n_sorted, n - n_sorted, device_compare);
+                n_sorted = n;
+        }
+
+        HASHMAP_FOREACH(device, enumerator->devices_by_syspath)
+                devices[n++] = sd_device_ref(device);
+
+        /* Move all devices back to the hashmap. Otherwise, devices added by
+         * udev_enumerate_add_syspath() -> device_enumerator_add_device() may not be listed. */
+        for (size_t i = 0; i < n_sorted; i++) {
+                const char *syspath;
+
+                r = sd_device_get_syspath(devices[i], &syspath);
+                if (r < 0)
+                        goto failed;
+
+                r = hashmap_put(enumerator->devices_by_syspath, syspath, devices[i]);
+                if (r < 0)
+                        goto failed;
+                assert(r > 0);
+
+                sd_device_ref(devices[i]);
+        }
+
+        typesafe_qsort(devices + n_sorted, n - n_sorted, device_compare);
+
+        device_unref_many(enumerator->devices, enumerator->n_devices);
+
+        enumerator->n_devices = n;
+        free_and_replace(enumerator->devices, devices);
+
+        enumerator->sorted = true;
+        return 0;
+
+failed:
+        device_unref_many(devices, n);
+        free(devices);
+        return r;
+}
+
+int device_enumerator_add_device(sd_device_enumerator *enumerator, sd_device *device) {
+        const char *syspath;
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(device, -EINVAL);
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        r = hashmap_ensure_put(&enumerator->devices_by_syspath, &string_hash_ops, syspath, device);
+        if (IN_SET(r, -EEXIST, 0))
+                return 0;
+        if (r < 0)
+                return r;
+
+        sd_device_ref(device);
+
+        enumerator->sorted = false;
+        return 1;
+}
+
+static bool match_property(Hashmap *properties, sd_device *device, bool match_all) {
+        const char *property_pattern;
+        char * const *value_patterns;
+
+        assert(device);
+
+        /* Unlike device_match_sysattr(), this accepts device that has at least one matching property. */
+
+        if (hashmap_isempty(properties))
+                return true;
+
+        HASHMAP_FOREACH_KEY(value_patterns, property_pattern, properties) {
+                bool match = false;
+
+                FOREACH_DEVICE_PROPERTY(device, property, value) {
+                        if (fnmatch(property_pattern, property, 0) != 0)
+                                continue;
+
+                        match = strv_fnmatch(value_patterns, value);
+                        if (match) {
+                                if (!match_all)
+                                        return true;
+
+                                break;
+                        }
+                }
+
+                if (!match && match_all)
+                        return false;
+        }
+
+        return match_all;
+}
+
+static bool match_tag(sd_device_enumerator *enumerator, sd_device *device) {
+        const char *tag;
+
+        assert(enumerator);
+        assert(device);
+
+        SET_FOREACH(tag, enumerator->match_tag)
+                if (!sd_device_has_tag(device, tag))
+                        return false;
+
+        return true;
+}
+
+static bool match_sysname(sd_device_enumerator *enumerator, const char *sysname) {
+        assert(enumerator);
+        assert(sysname);
+
+        return set_fnmatch(enumerator->match_sysname, enumerator->nomatch_sysname, sysname);
+}
+
+static int match_initialized(sd_device_enumerator *enumerator, sd_device *device) {
+        int r;
+
+        assert(enumerator);
+        assert(device);
+
+        if (enumerator->match_initialized == MATCH_INITIALIZED_ALL)
+                return true;
+
+        r = sd_device_get_is_initialized(device);
+        if (r == -ENOENT) /* this is necessarily racey, so ignore missing devices */
+                return false;
+        if (r < 0)
+                return r;
+
+        if (enumerator->match_initialized == MATCH_INITIALIZED_COMPAT) {
+                /* only devices that have no devnode/ifindex or have a db entry are accepted. */
+                if (r > 0)
+                        return true;
+
+                if (sd_device_get_devnum(device, NULL) >= 0)
+                        return false;
+
+                if (sd_device_get_ifindex(device, NULL) >= 0)
+                        return false;
+
+                return true;
+        }
+
+        return (enumerator->match_initialized == MATCH_INITIALIZED_NO) == (r == 0);
+}
+
+static bool match_subsystem(sd_device_enumerator *enumerator, const char *subsystem) {
+        assert(enumerator);
+
+        if (!subsystem)
+                return false;
+
+        return set_fnmatch(enumerator->match_subsystem, enumerator->nomatch_subsystem, subsystem);
+}
+
+typedef enum MatchFlag {
+        MATCH_SYSNAME     = 1u << 0,
+        MATCH_SUBSYSTEM   = 1u << 1,
+        MATCH_PARENT      = 1u << 2,
+        MATCH_TAG         = 1u << 3,
+
+        MATCH_ALL         = (1u << 4) - 1,
+} MatchFlag;
+
+static int test_matches(
+                sd_device_enumerator *enumerator,
+                sd_device *device,
+                MatchFlag flags) {
+
+        int r;
+
+        assert(enumerator);
+        assert(device);
+
+        if (FLAGS_SET(flags, MATCH_SYSNAME)) {
+                const char *sysname;
+
+                r = sd_device_get_sysname(device, &sysname);
+                if (r < 0)
+                        return r;
+
+                if (!match_sysname(enumerator, sysname))
+                        return false;
+        }
+
+        if (FLAGS_SET(flags, MATCH_SUBSYSTEM)) {
+                const char *subsystem;
+
+                r = sd_device_get_subsystem(device, &subsystem);
+                if (r == -ENOENT)
+                        return false;
+                if (r < 0)
+                        return r;
+
+                if (!match_subsystem(enumerator, subsystem))
+                        return false;
+        }
+
+        if (FLAGS_SET(flags, MATCH_PARENT) &&
+            !device_match_parent(device, enumerator->match_parent, NULL))
+                return false;
+
+        if (FLAGS_SET(flags, MATCH_TAG) &&
+            !match_tag(enumerator, device))
+                return false;
+
+        r = match_initialized(enumerator, device);
+        if (r <= 0)
+                return r;
+
+        if (!match_property(enumerator->match_property, device, /* match_all = */ false))
+                return false;
+
+        if (!match_property(enumerator->match_property_required, device, /* match_all = */ true))
+                return false;
+
+        if (!device_match_sysattr(device, enumerator->match_sysattr, enumerator->nomatch_sysattr))
+                return false;
+
+        return true;
+}
+
+static int enumerator_add_parent_devices(
+                sd_device_enumerator *enumerator,
+                sd_device *device,
+                MatchFlag flags) {
+
+        int r;
+
+        assert(enumerator);
+        assert(device);
+
+        for (;;) {
+                r = sd_device_get_parent(device, &device);
+                if (r == -ENOENT) /* Reached the top? */
+                        return 0;
+                if (r < 0)
+                        return r;
+
+                r = test_matches(enumerator, device, flags);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        continue;
+
+                r = device_enumerator_add_device(enumerator, device);
+                if (r < 0)
+                        return r;
+                if (r == 0) /* Exists already? Then no need to go further up. */
+                        return 0;
+        }
+}
+
+int device_enumerator_add_parent_devices(sd_device_enumerator *enumerator, sd_device *device) {
+        return enumerator_add_parent_devices(enumerator, device, MATCH_ALL & (~MATCH_PARENT));
+}
+
+static bool relevant_sysfs_subdir(const struct dirent *de) {
+        assert(de);
+
+        if (de->d_name[0] == '.')
+                return false;
+
+        /* Also filter out regular files and such, i.e. stuff that definitely isn't a kobject path. (Note
+         * that we rely on the fact that sysfs fills in d_type here, i.e. doesn't do DT_UNKNOWN) */
+        return IN_SET(de->d_type, DT_DIR, DT_LNK);
+}
+
+static int enumerator_scan_dir_and_add_devices(
+                sd_device_enumerator *enumerator,
+                const char *basedir,
+                const char *subdir1,
+                const char *subdir2) {
+
+        _cleanup_closedir_ DIR *dir = NULL;
+        char *path;
+        int k, r = 0;
+
+        assert(enumerator);
+        assert(basedir);
+
+        path = strjoina("/sys/", basedir, "/");
+
+        if (subdir1)
+                path = strjoina(path, subdir1, "/");
+
+        if (subdir2)
+                path = strjoina(path, subdir2, "/");
+
+        dir = opendir(path);
+        if (!dir) {
+                bool ignore = errno == ENOENT;
+
+                /* this is necessarily racey, so ignore missing directories */
+                log_debug_errno(errno,
+                                "sd-device-enumerator: Failed to open directory %s%s: %m",
+                                path, ignore ? ", ignoring" : "");
+                return ignore ? 0 : -errno;
+        }
+
+        FOREACH_DIRENT_ALL(de, dir, return -errno) {
+                _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+                char syspath[strlen(path) + 1 + strlen(de->d_name) + 1];
+
+                if (!relevant_sysfs_subdir(de))
+                        continue;
+
+                if (!match_sysname(enumerator, de->d_name))
+                        continue;
+
+                (void) sprintf(syspath, "%s%s", path, de->d_name);
+
+                k = sd_device_new_from_syspath(&device, syspath);
+                if (k < 0) {
+                        if (k != -ENODEV)
+                                /* this is necessarily racey, so ignore missing devices */
+                                r = k;
+
+                        continue;
+                }
+
+                k = test_matches(enumerator, device, MATCH_ALL & (~MATCH_SYSNAME)); /* sysname is already tested. */
+                if (k <= 0) {
+                        if (k < 0)
+                                r = k;
+                        continue;
+                }
+
+                k = device_enumerator_add_device(enumerator, device);
+                if (k < 0)
+                        r = k;
+
+                /* Also include all potentially matching parent devices in the enumeration. These are things
+                 * like root busses — e.g. /sys/devices/pci0000:00/ or /sys/devices/pnp0/, which ar not
+                 * linked from /sys/class/ or /sys/bus/, hence pick them up explicitly here. */
+                k = enumerator_add_parent_devices(enumerator, device, MATCH_ALL);
+                if (k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static int enumerator_scan_dir(
+                sd_device_enumerator *enumerator,
+                const char *basedir,
+                const char *subdir,
+                const char *subsystem) {
+
+        _cleanup_closedir_ DIR *dir = NULL;
+        char *path;
+        int r = 0;
+
+        path = strjoina("/sys/", basedir);
+
+        dir = opendir(path);
+        if (!dir) {
+                bool ignore = errno == ENOENT;
+
+                log_debug_errno(errno,
+                                "sd-device-enumerator: Failed to open directory %s%s: %m",
+                                path, ignore ? ", ignoring" : "");
+                return ignore ? 0 : -errno;
+        }
+
+        FOREACH_DIRENT_ALL(de, dir, return -errno) {
+                int k;
+
+                if (!relevant_sysfs_subdir(de))
+                        continue;
+
+                if (!match_subsystem(enumerator, subsystem ?: de->d_name))
+                        continue;
+
+                k = enumerator_scan_dir_and_add_devices(enumerator, basedir, de->d_name, subdir);
+                if (k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static int enumerator_scan_devices_tag(sd_device_enumerator *enumerator, const char *tag) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        char *path;
+        int r = 0;
+
+        assert(enumerator);
+        assert(tag);
+
+        path = strjoina("/run/udev/tags/", tag);
+
+        dir = opendir(path);
+        if (!dir) {
+                bool ignore = errno == ENOENT;
+
+                log_debug_errno(errno,
+                                "sd-device-enumerator: Failed to open directory %s%s: %m",
+                                path, ignore ? ", ignoring" : "");
+                return ignore ? 0 : -errno;
+        }
+
+        /* TODO: filter away subsystems? */
+
+        FOREACH_DIRENT_ALL(de, dir, return -errno) {
+                _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+                int k;
+
+                if (de->d_name[0] == '.')
+                        continue;
+
+                k = sd_device_new_from_device_id(&device, de->d_name);
+                if (k < 0) {
+                        if (k != -ENODEV)
+                                /* this is necessarily racy, so ignore missing devices */
+                                r = k;
+
+                        continue;
+                }
+
+                /* Generated from tag, hence not necessary to check tag again. */
+                k = test_matches(enumerator, device, MATCH_ALL & (~MATCH_TAG));
+                if (k < 0)
+                        r = k;
+                if (k <= 0)
+                        continue;
+
+                k = device_enumerator_add_device(enumerator, device);
+                if (k < 0) {
+                        r = k;
+                        continue;
+                }
+        }
+
+        return r;
+}
+
+static int enumerator_scan_devices_tags(sd_device_enumerator *enumerator) {
+        const char *tag;
+        int r = 0;
+
+        assert(enumerator);
+
+        SET_FOREACH(tag, enumerator->match_tag) {
+                int k;
+
+                k = enumerator_scan_devices_tag(enumerator, tag);
+                if (k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static int parent_add_child(sd_device_enumerator *enumerator, const char *path, MatchFlag flags) {
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+        int r;
+
+        r = sd_device_new_from_syspath(&device, path);
+        if (r == -ENODEV)
+                /* this is necessarily racy, so ignore missing devices */
+                return 0;
+        else if (r < 0)
+                return r;
+
+        r = test_matches(enumerator, device, flags);
+        if (r <= 0)
+                return r;
+
+        return device_enumerator_add_device(enumerator, device);
+}
+
+static int parent_crawl_children(sd_device_enumerator *enumerator, const char *path, Set **stack) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        int r = 0;
+
+        assert(enumerator);
+        assert(path);
+        assert(stack);
+
+        dir = opendir(path);
+        if (!dir) {
+                bool ignore = errno == ENOENT;
+
+                log_debug_errno(errno,
+                                "sd-device-enumerator: Failed to open directory %s%s: %m",
+                                path, ignore ? ", ignoring" : "");
+                return ignore ? 0 : -errno;
+        }
+
+        FOREACH_DIRENT_ALL(de, dir, return -errno) {
+                _cleanup_free_ char *child = NULL;
+                int k;
+
+                if (de->d_name[0] == '.')
+                        continue;
+
+                if (de->d_type != DT_DIR)
+                        continue;
+
+                child = path_join(path, de->d_name);
+                if (!child)
+                        return -ENOMEM;
+
+                /* Let's check sysname filter earlier. The other tests require the sd-device object created
+                 * from the path, thus much costly. */
+                if (match_sysname(enumerator, de->d_name)) {
+                        k = parent_add_child(enumerator, child, MATCH_ALL & (~(MATCH_SYSNAME|MATCH_PARENT)));
+                        if (k < 0)
+                                r = k;
+                }
+
+                k = set_ensure_consume(stack, &path_hash_ops_free, TAKE_PTR(child));
+                if (k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static int enumerator_scan_devices_children(sd_device_enumerator *enumerator) {
+        _cleanup_set_free_ Set *stack = NULL;
+        const char *path;
+        int r = 0, k;
+
+        assert(enumerator);
+
+        SET_FOREACH(path, enumerator->match_parent) {
+                k = parent_add_child(enumerator, path, MATCH_ALL & (~MATCH_PARENT));
+                if (k < 0)
+                        r = k;
+
+                k = parent_crawl_children(enumerator, path, &stack);
+                if (k < 0)
+                        r = k;
+        }
+
+        for (;;) {
+                _cleanup_free_ char *p = NULL;
+
+                p = set_steal_first(stack);
+                if (!p)
+                        return r;
+
+                k = parent_crawl_children(enumerator, p, &stack);
+                if (k < 0)
+                        r = k;
+        }
+}
+
+static int enumerator_scan_devices_all(sd_device_enumerator *enumerator) {
+        int k, r = 0;
+
+        k = enumerator_scan_dir(enumerator, "bus", "devices", NULL);
+        if (k < 0)
+                r = log_debug_errno(k, "sd-device-enumerator: Failed to scan /sys/bus: %m");
+
+        k = enumerator_scan_dir(enumerator, "class", NULL, NULL);
+        if (k < 0)
+                r = log_debug_errno(k, "sd-device-enumerator: Failed to scan /sys/class: %m");
+
+        return r;
+}
+
+int device_enumerator_scan_devices(sd_device_enumerator *enumerator) {
+        int r = 0, k;
+
+        assert(enumerator);
+
+        if (enumerator->scan_uptodate &&
+            enumerator->type == DEVICE_ENUMERATION_TYPE_DEVICES)
+                return 0;
+
+        device_enumerator_unref_devices(enumerator);
+
+        if (!set_isempty(enumerator->match_tag)) {
+                k = enumerator_scan_devices_tags(enumerator);
+                if (k < 0)
+                        r = k;
+        } else if (enumerator->match_parent) {
+                k = enumerator_scan_devices_children(enumerator);
+                if (k < 0)
+                        r = k;
+        } else {
+                k = enumerator_scan_devices_all(enumerator);
+                if (k < 0)
+                        r = k;
+        }
+
+        enumerator->scan_uptodate = true;
+        enumerator->type = DEVICE_ENUMERATION_TYPE_DEVICES;
+
+        return r;
+}
+
+_public_ sd_device *sd_device_enumerator_get_device_first(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (device_enumerator_scan_devices(enumerator) < 0)
+                return NULL;
+
+        if (enumerator_sort_devices(enumerator) < 0)
+                return NULL;
+
+        enumerator->current_device_index = 0;
+
+        if (enumerator->n_devices == 0)
+                return NULL;
+
+        return enumerator->devices[0];
+}
+
+_public_ sd_device *sd_device_enumerator_get_device_next(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (!enumerator->scan_uptodate ||
+            !enumerator->sorted ||
+            enumerator->type != DEVICE_ENUMERATION_TYPE_DEVICES ||
+            enumerator->current_device_index + 1 >= enumerator->n_devices)
+                return NULL;
+
+        return enumerator->devices[++enumerator->current_device_index];
+}
+
+int device_enumerator_scan_subsystems(sd_device_enumerator *enumerator) {
+        int r = 0, k;
+
+        assert(enumerator);
+
+        if (enumerator->scan_uptodate &&
+            enumerator->type == DEVICE_ENUMERATION_TYPE_SUBSYSTEMS)
+                return 0;
+
+        device_enumerator_unref_devices(enumerator);
+
+        /* modules */
+        if (match_subsystem(enumerator, "module")) {
+                k = enumerator_scan_dir_and_add_devices(enumerator, "module", NULL, NULL);
+                if (k < 0)
+                        r = log_debug_errno(k, "sd-device-enumerator: Failed to scan modules: %m");
+        }
+
+        /* subsystems (only buses support coldplug) */
+        if (match_subsystem(enumerator, "subsystem")) {
+                k = enumerator_scan_dir_and_add_devices(enumerator, "bus", NULL, NULL);
+                if (k < 0)
+                        r = log_debug_errno(k, "sd-device-enumerator: Failed to scan subsystems: %m");
+        }
+
+        /* subsystem drivers */
+        if (match_subsystem(enumerator, "drivers")) {
+                k = enumerator_scan_dir(enumerator, "bus", "drivers", "drivers");
+                if (k < 0)
+                        r = log_debug_errno(k, "sd-device-enumerator: Failed to scan drivers: %m");
+        }
+
+        enumerator->scan_uptodate = true;
+        enumerator->type = DEVICE_ENUMERATION_TYPE_SUBSYSTEMS;
+
+        return r;
+}
+
+_public_ sd_device *sd_device_enumerator_get_subsystem_first(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (device_enumerator_scan_subsystems(enumerator) < 0)
+                return NULL;
+
+        if (enumerator_sort_devices(enumerator) < 0)
+                return NULL;
+
+        enumerator->current_device_index = 0;
+
+        if (enumerator->n_devices == 0)
+                return NULL;
+
+        return enumerator->devices[0];
+}
+
+_public_ sd_device *sd_device_enumerator_get_subsystem_next(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (!enumerator->scan_uptodate ||
+            !enumerator->sorted ||
+            enumerator->type != DEVICE_ENUMERATION_TYPE_SUBSYSTEMS ||
+            enumerator->current_device_index + 1 >= enumerator->n_devices)
+                return NULL;
+
+        return enumerator->devices[++enumerator->current_device_index];
+}
+
+int device_enumerator_scan_devices_and_subsystems(sd_device_enumerator *enumerator) {
+        int r;
+
+        assert(enumerator);
+
+        if (enumerator->scan_uptodate &&
+            enumerator->type == DEVICE_ENUMERATION_TYPE_ALL)
+                return 0;
+
+        device_enumerator_unref_devices(enumerator);
+
+        if (!set_isempty(enumerator->match_tag))
+                r = enumerator_scan_devices_tags(enumerator);
+        else if (enumerator->match_parent)
+                r = enumerator_scan_devices_children(enumerator);
+        else {
+                int k;
+
+                r = enumerator_scan_devices_all(enumerator);
+
+                if (match_subsystem(enumerator, "module")) {
+                        k = enumerator_scan_dir_and_add_devices(enumerator, "module", NULL, NULL);
+                        if (k < 0)
+                                r = log_debug_errno(k, "sd-device-enumerator: Failed to scan modules: %m");
+                }
+                if (match_subsystem(enumerator, "subsystem")) {
+                        k = enumerator_scan_dir_and_add_devices(enumerator, "bus", NULL, NULL);
+                        if (k < 0)
+                                r = log_debug_errno(k, "sd-device-enumerator: Failed to scan subsystems: %m");
+                }
+
+                if (match_subsystem(enumerator, "drivers")) {
+                        k = enumerator_scan_dir(enumerator, "bus", "drivers", "drivers");
+                        if (k < 0)
+                                r = log_debug_errno(k, "sd-device-enumerator: Failed to scan drivers: %m");
+                }
+        }
+
+        enumerator->scan_uptodate = true;
+        enumerator->type = DEVICE_ENUMERATION_TYPE_ALL;
+
+        return r;
+}
+
+sd_device *device_enumerator_get_first(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (!enumerator->scan_uptodate)
+                return NULL;
+
+        if (enumerator_sort_devices(enumerator) < 0)
+                return NULL;
+
+        enumerator->current_device_index = 0;
+
+        if (enumerator->n_devices == 0)
+                return NULL;
+
+        return enumerator->devices[0];
+}
+
+sd_device *device_enumerator_get_next(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (!enumerator->scan_uptodate ||
+            !enumerator->sorted ||
+            enumerator->current_device_index + 1 >= enumerator->n_devices)
+                return NULL;
+
+        return enumerator->devices[++enumerator->current_device_index];
+}
+
+sd_device **device_enumerator_get_devices(sd_device_enumerator *enumerator, size_t *ret_n_devices) {
+        assert(enumerator);
+        assert(ret_n_devices);
+
+        if (!enumerator->scan_uptodate)
+                return NULL;
+
+        if (enumerator_sort_devices(enumerator) < 0)
+                return NULL;
+
+        *ret_n_devices = enumerator->n_devices;
+        return enumerator->devices;
+}
diff --git a/src/libsystemd/sd-device/device-filter.c b/src/libsystemd/sd-device/device-filter.c
new file mode 100644
index 0000000..4101e7d
--- /dev/null
+++ b/src/libsystemd/sd-device/device-filter.c
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fnmatch.h>
+
+#include "device-filter.h"
+#include "path-util.h"
+
+int update_match_strv(Hashmap **match_strv, const char *key, const char *value, bool clear_on_null) {
+        char **strv;
+        int r;
+
+        assert(match_strv);
+        assert(key);
+
+        strv = hashmap_get(*match_strv, key);
+        if (strv) {
+                if (!value) {
+                        char **v;
+
+                        if (strv_isempty(strv) || !clear_on_null)
+                                return 0;
+
+                        /* Accept all value. Clear previous assignment. */
+
+                        v = new0(char*, 1);
+                        if (!v)
+                                return -ENOMEM;
+
+                        strv_free_and_replace(strv, v);
+                } else {
+                        if (strv_contains(strv, value))
+                                return 0;
+
+                        r = strv_extend(&strv, value);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = hashmap_update(*match_strv, key, strv);
+                if (r < 0)
+                        return r;
+
+        } else {
+                _cleanup_strv_free_ char **strv_alloc = NULL;
+                _cleanup_free_ char *key_alloc = NULL;
+
+                key_alloc = strdup(key);
+                if (!key_alloc)
+                        return -ENOMEM;
+
+                strv_alloc = strv_new(value);
+                if (!strv_alloc)
+                        return -ENOMEM;
+
+                r = hashmap_ensure_put(match_strv, &string_hash_ops_free_strv_free, key_alloc, strv_alloc);
+                if (r < 0)
+                        return r;
+
+                TAKE_PTR(key_alloc);
+                TAKE_PTR(strv_alloc);
+        }
+
+        return 1;
+}
+
+static bool device_match_sysattr_value(sd_device *device, const char *sysattr, char * const *patterns) {
+        const char *value;
+
+        assert(device);
+        assert(sysattr);
+
+        if (sd_device_get_sysattr_value(device, sysattr, &value) < 0)
+                return false;
+
+        return strv_fnmatch_or_empty(patterns, value, 0);
+}
+
+bool device_match_sysattr(sd_device *device, Hashmap *match_sysattr, Hashmap *nomatch_sysattr) {
+        char * const *patterns;
+        const char *sysattr;
+
+        assert(device);
+
+        HASHMAP_FOREACH_KEY(patterns, sysattr, match_sysattr)
+                if (!device_match_sysattr_value(device, sysattr, patterns))
+                        return false;
+
+        HASHMAP_FOREACH_KEY(patterns, sysattr, nomatch_sysattr)
+                if (device_match_sysattr_value(device, sysattr, patterns))
+                        return false;
+
+        return true;
+}
+
+bool device_match_parent(sd_device *device, Set *match_parent, Set *nomatch_parent) {
+        const char *syspath_parent, *syspath;
+
+        assert(device);
+
+        if (sd_device_get_syspath(device, &syspath) < 0)
+                return false;
+
+        SET_FOREACH(syspath_parent, nomatch_parent)
+                if (path_startswith(syspath, syspath_parent))
+                        return false;
+
+        if (set_isempty(match_parent))
+                return true;
+
+        SET_FOREACH(syspath_parent, match_parent)
+                if (path_startswith(syspath, syspath_parent))
+                        return true;
+
+        return false;
+}
diff --git a/src/libsystemd/sd-device/device-filter.h b/src/libsystemd/sd-device/device-filter.h
new file mode 100644
index 0000000..0c5f34e
--- /dev/null
+++ b/src/libsystemd/sd-device/device-filter.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <stdbool.h>
+
+#include "sd-device.h"
+
+#include "hashmap.h"
+#include "set.h"
+
+int update_match_strv(Hashmap **match_strv, const char *key, const char *value, bool clear_on_null);
+bool device_match_sysattr(sd_device *device, Hashmap *match_sysattr, Hashmap *nomatch_sysattr);
+bool device_match_parent(sd_device *device, Set *match_parent, Set *nomatch_parent);
diff --git a/src/libsystemd/sd-device/device-internal.h b/src/libsystemd/sd-device/device-internal.h
new file mode 100644
index 0000000..a465eb2
--- /dev/null
+++ b/src/libsystemd/sd-device/device-internal.h
@@ -0,0 +1,117 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-device.h"
+
+#include "device-private.h"
+#include "hashmap.h"
+#include "set.h"
+#include "time-util.h"
+
+#define LATEST_UDEV_DATABASE_VERSION 1
+
+struct sd_device {
+        unsigned n_ref;
+
+        /* The database version indicates the supported features by the udev database.
+         * This is saved and parsed in V field.
+         *
+         * 0: None of the following features are supported (systemd version <= 246).
+         * 1: The current tags (Q) and the database version (V) features are implemented (>= 247).
+         */
+        unsigned database_version;
+
+        sd_device *parent;
+
+        OrderedHashmap *properties;
+        Iterator properties_iterator;
+        uint64_t properties_generation; /* changes whenever the properties are changed */
+        uint64_t properties_iterator_generation; /* generation when iteration was started */
+
+        /* the subset of the properties that should be written to the db */
+        OrderedHashmap *properties_db;
+
+        Hashmap *sysattr_values; /* cached sysattr values */
+
+        Set *sysattrs; /* names of sysattrs */
+        Iterator sysattrs_iterator;
+
+        Set *all_tags, *current_tags;
+        Iterator all_tags_iterator, current_tags_iterator;
+        uint64_t all_tags_iterator_generation, current_tags_iterator_generation; /* generation when iteration was started */
+        uint64_t tags_generation; /* changes whenever the tags are changed */
+
+        Set *devlinks;
+        Iterator devlinks_iterator;
+        uint64_t devlinks_generation; /* changes whenever the devlinks are changed */
+        uint64_t devlinks_iterator_generation; /* generation when iteration was started */
+        int devlink_priority;
+
+        Hashmap *children;
+        Iterator children_iterator;
+        bool children_enumerated;
+
+        int ifindex;
+        char *devtype;
+        char *devname;
+        dev_t devnum;
+
+        char **properties_strv; /* the properties hashmap as a strv */
+        char *properties_nulstr; /* the same as a nulstr */
+        size_t properties_nulstr_len;
+
+        char *syspath;
+        const char *devpath;
+        const char *sysnum;
+        char *sysname;
+
+        char *subsystem;
+        char *driver_subsystem; /* only set for the 'drivers' subsystem */
+        char *driver;
+
+        char *device_id;
+
+        usec_t usec_initialized;
+
+        mode_t devmode;
+        uid_t devuid;
+        gid_t devgid;
+
+        uint64_t diskseq; /* Block device sequence number, monothonically incremented by the kernel on create/attach */
+
+        /* only set when device is passed through netlink */
+        sd_device_action_t action;
+        uint64_t seqnum;
+
+        bool parent_set:1; /* no need to try to reload parent */
+        bool sysattrs_read:1; /* don't try to re-read sysattrs once read */
+        bool property_tags_outdated:1; /* need to update TAGS= or CURRENT_TAGS= property */
+        bool property_devlinks_outdated:1; /* need to update DEVLINKS= property */
+        bool properties_buf_outdated:1; /* need to reread hashmap */
+        bool subsystem_set:1; /* don't reread subsystem */
+        bool driver_set:1; /* don't reread driver */
+        bool uevent_loaded:1; /* don't reread uevent */
+        bool db_loaded; /* don't reread db */
+
+        bool is_initialized:1;
+        bool sealed:1; /* don't read more information from uevent/db */
+        bool db_persist:1; /* don't clean up the db when switching from initrd to real root */
+};
+
+int device_new_aux(sd_device **ret);
+int device_add_property_aux(sd_device *device, const char *key, const char *value, bool db);
+static inline int device_add_property_internal(sd_device *device, const char *key, const char *value) {
+        return device_add_property_aux(device, key, value, false);
+}
+
+int device_set_syspath(sd_device *device, const char *_syspath, bool verify);
+int device_set_ifindex(sd_device *device, const char *ifindex);
+int device_set_devmode(sd_device *device, const char *devmode);
+int device_set_devname(sd_device *device, const char *devname);
+int device_set_devtype(sd_device *device, const char *devtype);
+int device_set_devnum(sd_device *device, const char *major, const char *minor);
+int device_set_subsystem(sd_device *device, const char *subsystem);
+int device_set_diskseq(sd_device *device, const char *str);
+int device_set_drivers_subsystem(sd_device *device);
+int device_set_driver(sd_device *device, const char *driver);
+int device_set_usec_initialized(sd_device *device, usec_t when);
diff --git a/src/libsystemd/sd-device/device-monitor-private.h b/src/libsystemd/sd-device/device-monitor-private.h
new file mode 100644
index 0000000..33e2714
--- /dev/null
+++ b/src/libsystemd/sd-device/device-monitor-private.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <errno.h>
+
+#include "sd-device.h"
+
+typedef enum MonitorNetlinkGroup {
+        MONITOR_GROUP_NONE,
+        MONITOR_GROUP_KERNEL,
+        MONITOR_GROUP_UDEV,
+        _MONITOR_NETLINK_GROUP_MAX,
+        _MONITOR_NETLINK_GROUP_INVALID = -EINVAL,
+} MonitorNetlinkGroup;
+
+int device_monitor_new_full(sd_device_monitor **ret, MonitorNetlinkGroup group, int fd);
+int device_monitor_disconnect(sd_device_monitor *m);
+int device_monitor_allow_unicast_sender(sd_device_monitor *m, sd_device_monitor *sender);
+int device_monitor_enable_receiving(sd_device_monitor *m);
+int device_monitor_get_fd(sd_device_monitor *m);
+int device_monitor_send_device(sd_device_monitor *m, sd_device_monitor *destination, sd_device *device);
+int device_monitor_receive_device(sd_device_monitor *m, sd_device **ret);
diff --git a/src/libsystemd/sd-device/device-monitor.c b/src/libsystemd/sd-device/device-monitor.c
new file mode 100644
index 0000000..bb4f9bd
--- /dev/null
+++ b/src/libsystemd/sd-device/device-monitor.c
@@ -0,0 +1,929 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <linux/filter.h>
+#include <linux/netlink.h>
+#include <linux/sockios.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+#include "sd-device.h"
+#include "sd-event.h"
+
+#include "MurmurHash2.h"
+#include "alloc-util.h"
+#include "device-filter.h"
+#include "device-monitor-private.h"
+#include "device-private.h"
+#include "device-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "format-util.h"
+#include "hashmap.h"
+#include "iovec-util.h"
+#include "missing_socket.h"
+#include "mountpoint-util.h"
+#include "set.h"
+#include "socket-util.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "uid-range.h"
+
+#define log_monitor(m, format, ...)                                     \
+        log_debug("sd-device-monitor(%s): " format, strna(m ? m->description : NULL), ##__VA_ARGS__)
+#define log_monitor_errno(m, r, format, ...)                            \
+        log_debug_errno(r, "sd-device-monitor(%s): " format, strna(m ? m->description : NULL), ##__VA_ARGS__)
+#define log_device_monitor(d, m, format, ...)                           \
+        log_device_debug(d, "sd-device-monitor(%s): " format, strna(m ? m->description : NULL), ##__VA_ARGS__)
+#define log_device_monitor_errno(d, m, r, format, ...)                  \
+        log_device_debug_errno(d, r, "sd-device-monitor(%s): " format, strna(m ? m->description : NULL), ##__VA_ARGS__)
+
+struct sd_device_monitor {
+        unsigned n_ref;
+
+        int sock;
+        union sockaddr_union snl;
+        union sockaddr_union snl_trusted_sender;
+        bool bound;
+
+        UidRange *mapped_userns_uid_range;
+
+        Hashmap *subsystem_filter;
+        Set *tag_filter;
+        Hashmap *match_sysattr_filter;
+        Hashmap *nomatch_sysattr_filter;
+        Set *match_parent_filter;
+        Set *nomatch_parent_filter;
+        bool filter_uptodate;
+
+        sd_event *event;
+        sd_event_source *event_source;
+        char *description;
+        sd_device_monitor_handler_t callback;
+        void *userdata;
+};
+
+#define UDEV_MONITOR_MAGIC                0xfeedcafe
+
+typedef struct monitor_netlink_header {
+        /* "libudev" prefix to distinguish libudev and kernel messages */
+        char prefix[8];
+        /* Magic to protect against daemon <-> Library message format mismatch
+         * Used in the kernel from socket filter rules; needs to be stored in network order */
+        unsigned magic;
+        /* Total length of header structure known to the sender */
+        unsigned header_size;
+        /* Properties string buffer */
+        unsigned properties_off;
+        unsigned properties_len;
+        /* Hashes of primary device properties strings, to let libudev subscribers
+         * use in-kernel socket filters; values need to be stored in network order */
+        unsigned filter_subsystem_hash;
+        unsigned filter_devtype_hash;
+        unsigned filter_tag_bloom_hi;
+        unsigned filter_tag_bloom_lo;
+} monitor_netlink_header;
+
+static int monitor_set_nl_address(sd_device_monitor *m) {
+        union sockaddr_union snl;
+        socklen_t addrlen;
+
+        assert(m);
+
+        /* Get the address the kernel has assigned us.
+         * It is usually, but not necessarily the pid. */
+        addrlen = sizeof(struct sockaddr_nl);
+        if (getsockname(m->sock, &snl.sa, &addrlen) < 0)
+                return -errno;
+
+        m->snl.nl.nl_pid = snl.nl.nl_pid;
+        return 0;
+}
+
+int device_monitor_allow_unicast_sender(sd_device_monitor *m, sd_device_monitor *sender) {
+        assert(m);
+        assert(sender);
+
+        m->snl_trusted_sender.nl.nl_pid = sender->snl.nl.nl_pid;
+        return 0;
+}
+
+_public_ int sd_device_monitor_set_receive_buffer_size(sd_device_monitor *m, size_t size) {
+        assert_return(m, -EINVAL);
+
+        return fd_set_rcvbuf(m->sock, size, false);
+}
+
+int device_monitor_disconnect(sd_device_monitor *m) {
+        assert(m);
+
+        m->sock = safe_close(m->sock);
+        return 0;
+}
+
+int device_monitor_get_fd(sd_device_monitor *m) {
+        assert(m);
+
+        return m->sock;
+}
+
+int device_monitor_new_full(sd_device_monitor **ret, MonitorNetlinkGroup group, int fd) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *m = NULL;
+        _cleanup_close_ int sock = -EBADF;
+        int r;
+
+        assert(group >= 0 && group < _MONITOR_NETLINK_GROUP_MAX);
+        assert_return(ret, -EINVAL);
+
+        if (group == MONITOR_GROUP_UDEV &&
+            access("/run/udev/control", F_OK) < 0 &&
+            dev_is_devtmpfs() <= 0) {
+
+                /*
+                 * We do not support subscribing to uevents if no instance of
+                 * udev is running. Uevents would otherwise broadcast the
+                 * processing data of the host into containers, which is not
+                 * desired.
+                 *
+                 * Containers will currently not get any udev uevents, until
+                 * a supporting infrastructure is available.
+                 *
+                 * We do not set a netlink multicast group here, so the socket
+                 * will not receive any messages.
+                 */
+
+                log_monitor(m, "The udev service seems not to be active, disabling the monitor.");
+                group = MONITOR_GROUP_NONE;
+        }
+
+        if (fd < 0) {
+                sock = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_KOBJECT_UEVENT);
+                if (sock < 0)
+                        return log_monitor_errno(m, errno, "Failed to create socket: %m");
+        }
+
+        m = new(sd_device_monitor, 1);
+        if (!m)
+                return -ENOMEM;
+
+        *m = (sd_device_monitor) {
+                .n_ref = 1,
+                .sock = fd >= 0 ? fd : TAKE_FD(sock),
+                .bound = fd >= 0,
+                .snl.nl.nl_family = AF_NETLINK,
+                .snl.nl.nl_groups = group,
+        };
+
+        if (fd >= 0) {
+                r = monitor_set_nl_address(m);
+                if (r < 0) {
+                        log_monitor_errno(m, r, "Failed to set netlink address: %m");
+                        goto fail;
+                }
+        }
+
+        if (DEBUG_LOGGING) {
+                _cleanup_close_ int netns = -EBADF;
+
+                /* So here's the thing: only AF_NETLINK sockets from the main network namespace will get
+                 * hardware events. Let's check if ours is from there, and if not generate a debug message,
+                 * since we cannot possibly work correctly otherwise. This is just a safety check to make
+                 * things easier to debug. */
+
+                netns = ioctl(m->sock, SIOCGSKNS);
+                if (netns < 0)
+                        log_monitor_errno(m, errno, "Unable to get network namespace of udev netlink socket, unable to determine if we are in host netns, ignoring: %m");
+                else {
+                        struct stat a, b;
+
+                        if (fstat(netns, &a) < 0) {
+                                r = log_monitor_errno(m, errno, "Failed to stat netns of udev netlink socket: %m");
+                                goto fail;
+                        }
+
+                        if (stat("/proc/1/ns/net", &b) < 0) {
+                                if (ERRNO_IS_PRIVILEGE(errno))
+                                        /* If we can't access PID1's netns info due to permissions, it's fine, this is a
+                                         * safety check only after all. */
+                                        log_monitor_errno(m, errno, "No permission to stat PID1's netns, unable to determine if we are in host netns, ignoring: %m");
+                                else
+                                        log_monitor_errno(m, errno, "Failed to stat PID1's netns, ignoring: %m");
+
+                        } else if (!stat_inode_same(&a, &b))
+                                log_monitor(m, "Netlink socket we listen on is not from host netns, we won't see device events.");
+                }
+        }
+
+        /* Let's bump the receive buffer size, but only if we are not called via socket activation, as in
+         * that case the service manager sets the receive buffer size for us, and the value in the .socket
+         * unit should take full effect. */
+        if (fd < 0) {
+                r = sd_device_monitor_set_receive_buffer_size(m, 128*1024*1024);
+                if (r < 0)
+                        log_monitor_errno(m, r, "Failed to increase receive buffer size, ignoring: %m");
+        }
+
+        *ret = TAKE_PTR(m);
+        return 0;
+
+fail:
+        /* Let's unset the socket fd in the monitor object before we destroy it so that the fd passed in is
+         * not closed on failure. */
+        if (fd >= 0)
+                m->sock = -1;
+
+        return r;
+}
+
+_public_ int sd_device_monitor_new(sd_device_monitor **ret) {
+        return device_monitor_new_full(ret, MONITOR_GROUP_UDEV, -1);
+}
+
+_public_ int sd_device_monitor_stop(sd_device_monitor *m) {
+        assert_return(m, -EINVAL);
+
+        m->event_source = sd_event_source_unref(m->event_source);
+        (void) device_monitor_disconnect(m);
+
+        return 0;
+}
+
+static int device_monitor_event_handler(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+        _unused_ _cleanup_(log_context_unrefp) LogContext *c = NULL;
+        sd_device_monitor *m = ASSERT_PTR(userdata);
+
+        if (device_monitor_receive_device(m, &device) <= 0)
+                return 0;
+
+        if (log_context_enabled())
+                c = log_context_new_strv_consume(device_make_log_fields(device));
+
+        if (m->callback)
+                return m->callback(m, device, m->userdata);
+
+        return 0;
+}
+
+_public_ int sd_device_monitor_start(sd_device_monitor *m, sd_device_monitor_handler_t callback, void *userdata) {
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        if (!m->event) {
+                r = sd_device_monitor_attach_event(m, NULL);
+                if (r < 0)
+                        return r;
+        }
+
+        r = device_monitor_enable_receiving(m);
+        if (r < 0)
+                return r;
+
+        m->callback = callback;
+        m->userdata = userdata;
+
+        r = sd_event_add_io(m->event, &m->event_source, m->sock, EPOLLIN, device_monitor_event_handler, m);
+        if (r < 0)
+                return r;
+
+        (void) sd_event_source_set_description(m->event_source, m->description ?: "sd-device-monitor");
+
+        return 0;
+}
+
+_public_ int sd_device_monitor_detach_event(sd_device_monitor *m) {
+        assert_return(m, -EINVAL);
+
+        (void) sd_device_monitor_stop(m);
+        m->event = sd_event_unref(m->event);
+
+        return 0;
+}
+
+_public_ int sd_device_monitor_attach_event(sd_device_monitor *m, sd_event *event) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->event, -EBUSY);
+
+        if (event)
+                m->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&m->event);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+_public_ sd_event *sd_device_monitor_get_event(sd_device_monitor *m) {
+        assert_return(m, NULL);
+
+        return m->event;
+}
+
+_public_ sd_event_source *sd_device_monitor_get_event_source(sd_device_monitor *m) {
+        assert_return(m, NULL);
+
+        return m->event_source;
+}
+
+_public_ int sd_device_monitor_set_description(sd_device_monitor *m, const char *description) {
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = free_and_strdup(&m->description, description);
+        if (r <= 0)
+                return r;
+
+        if (m->event_source)
+                (void) sd_event_source_set_description(m->event_source, description);
+
+        return r;
+}
+
+_public_ int sd_device_monitor_get_description(sd_device_monitor *m, const char **ret) {
+        assert_return(m, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        *ret = m->description;
+        return 0;
+}
+
+int device_monitor_enable_receiving(sd_device_monitor *m) {
+        int r;
+
+        assert(m);
+
+        r = sd_device_monitor_filter_update(m);
+        if (r < 0)
+                return log_monitor_errno(m, r, "Failed to update filter: %m");
+
+        if (!m->bound) {
+                /* enable receiving of sender credentials */
+                r = setsockopt_int(m->sock, SOL_SOCKET, SO_PASSCRED, true);
+                if (r < 0)
+                        return log_monitor_errno(m, r, "Failed to set socket option SO_PASSCRED: %m");
+
+                if (bind(m->sock, &m->snl.sa, sizeof(struct sockaddr_nl)) < 0)
+                        return log_monitor_errno(m, errno, "Failed to bind monitoring socket: %m");
+
+                m->bound = true;
+
+                r = monitor_set_nl_address(m);
+                if (r < 0)
+                        return log_monitor_errno(m, r, "Failed to set address: %m");
+        }
+
+        return 0;
+}
+
+static sd_device_monitor *device_monitor_free(sd_device_monitor *m) {
+        assert(m);
+
+        (void) sd_device_monitor_detach_event(m);
+
+        uid_range_free(m->mapped_userns_uid_range);
+        free(m->description);
+        hashmap_free(m->subsystem_filter);
+        set_free(m->tag_filter);
+        hashmap_free(m->match_sysattr_filter);
+        hashmap_free(m->nomatch_sysattr_filter);
+        set_free(m->match_parent_filter);
+        set_free(m->nomatch_parent_filter);
+
+        return mfree(m);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_device_monitor, sd_device_monitor, device_monitor_free);
+
+static int check_subsystem_filter(sd_device_monitor *m, sd_device *device) {
+        const char *s, *subsystem, *d, *devtype = NULL;
+        int r;
+
+        assert(m);
+        assert(device);
+
+        if (hashmap_isempty(m->subsystem_filter))
+                return true;
+
+        r = sd_device_get_subsystem(device, &subsystem);
+        if (r < 0)
+                return r;
+
+        r = sd_device_get_devtype(device, &devtype);
+        if (r < 0 && r != -ENOENT)
+                return r;
+
+        HASHMAP_FOREACH_KEY(d, s, m->subsystem_filter) {
+                if (!streq(s, subsystem))
+                        continue;
+
+                if (!d || streq_ptr(d, devtype))
+                        return true;
+        }
+
+        return false;
+}
+
+static bool check_tag_filter(sd_device_monitor *m, sd_device *device) {
+        const char *tag;
+
+        assert(m);
+        assert(device);
+
+        if (set_isempty(m->tag_filter))
+                return true;
+
+        SET_FOREACH(tag, m->tag_filter)
+                if (sd_device_has_tag(device, tag) > 0)
+                        return true;
+
+        return false;
+}
+
+static int passes_filter(sd_device_monitor *m, sd_device *device) {
+        int r;
+
+        assert(m);
+        assert(device);
+
+        r = check_subsystem_filter(m, device);
+        if (r <= 0)
+                return r;
+
+        if (!check_tag_filter(m, device))
+                return false;
+
+        if (!device_match_sysattr(device, m->match_sysattr_filter, m->nomatch_sysattr_filter))
+                return false;
+
+        return device_match_parent(device, m->match_parent_filter, m->nomatch_parent_filter);
+}
+
+static bool check_sender_uid(sd_device_monitor *m, uid_t uid) {
+        int r;
+
+        assert(m);
+
+        /* Always trust messages from uid 0. */
+        if (uid == 0)
+                return true;
+
+        /* Trust messages sent by the same UID we are running. Currently, such situation happens only for
+         * unicast messages. */
+        if (uid == getuid() || uid == geteuid())
+                return true;
+
+        if (!m->mapped_userns_uid_range) {
+                r = uid_range_load_userns(&m->mapped_userns_uid_range, NULL);
+                if (r < 0)
+                        log_monitor_errno(m, r, "Failed to load UID ranges mapped to the current user namespace, ignoring: %m");
+        }
+
+        /* Trust messages come from outside of the current user namespace. */
+        if (!uid_range_contains(m->mapped_userns_uid_range, uid))
+                return true;
+
+        /* Otherwise, refuse messages. */
+        return false;
+}
+
+int device_monitor_receive_device(sd_device_monitor *m, sd_device **ret) {
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+        _cleanup_free_ uint8_t *buf_alloc = NULL;
+        union {
+                monitor_netlink_header *nlh;
+                char *nulstr;
+                uint8_t *buf;
+        } message;
+        struct iovec iov;
+        CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct ucred))) control;
+        union sockaddr_union snl;
+        struct msghdr smsg = {
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
+                .msg_name = &snl,
+                .msg_namelen = sizeof(snl),
+        };
+        struct ucred *cred;
+        size_t offset;
+        ssize_t n;
+        bool is_initialized = false;
+        int r;
+
+        assert(m);
+        assert(ret);
+
+        n = next_datagram_size_fd(m->sock);
+        if (n < 0) {
+                if (!ERRNO_IS_TRANSIENT(n))
+                        log_monitor_errno(m, n, "Failed to get the received message size: %m");
+                return n;
+        }
+
+        if ((size_t) n < ALLOCA_MAX / sizeof(uint8_t) / 2)
+                message.buf = newa(uint8_t, n);
+        else {
+                buf_alloc = new(uint8_t, n);
+                if (!buf_alloc)
+                        return log_oom_debug();
+
+                message.buf = buf_alloc;
+        }
+
+        iov = IOVEC_MAKE(message.buf, n);
+
+        n = recvmsg(m->sock, &smsg, 0);
+        if (n < 0) {
+                if (!ERRNO_IS_TRANSIENT(errno))
+                        log_monitor_errno(m, errno, "Failed to receive message: %m");
+                return -errno;
+        }
+
+        if (smsg.msg_flags & MSG_TRUNC)
+                return log_monitor_errno(m, SYNTHETIC_ERRNO(EINVAL), "Received truncated message, ignoring message.");
+
+        if (n < 32)
+                return log_monitor_errno(m, SYNTHETIC_ERRNO(EINVAL), "Invalid message length (%zi), ignoring message.", n);
+
+        if (snl.nl.nl_groups == MONITOR_GROUP_NONE) {
+                /* unicast message, check if we trust the sender */
+                if (m->snl_trusted_sender.nl.nl_pid == 0 ||
+                    snl.nl.nl_pid != m->snl_trusted_sender.nl.nl_pid)
+                        return log_monitor_errno(m, SYNTHETIC_ERRNO(EAGAIN),
+                                                 "Unicast netlink message ignored.");
+
+        } else if (snl.nl.nl_groups == MONITOR_GROUP_KERNEL) {
+                if (snl.nl.nl_pid > 0)
+                        return log_monitor_errno(m, SYNTHETIC_ERRNO(EAGAIN),
+                                                 "Multicast kernel netlink message from PID %"PRIu32" ignored.",
+                                                 snl.nl.nl_pid);
+        }
+
+        cred = CMSG_FIND_DATA(&smsg, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
+        if (!cred)
+                return log_monitor_errno(m, SYNTHETIC_ERRNO(EAGAIN),
+                                         "No sender credentials received, ignoring message.");
+
+        if (!check_sender_uid(m, cred->uid))
+                return log_monitor_errno(m, SYNTHETIC_ERRNO(EAGAIN),
+                                         "Sender uid="UID_FMT", message ignored.", cred->uid);
+
+        if (!memchr(message.buf, 0, n))
+                return log_monitor_errno(m, SYNTHETIC_ERRNO(EAGAIN), "Received message without NUL, ignoring message.");
+
+        if (streq(message.nulstr, "libudev")) {
+                /* udev message needs proper version magic */
+                if (message.nlh->magic != htobe32(UDEV_MONITOR_MAGIC))
+                        return log_monitor_errno(m, SYNTHETIC_ERRNO(EAGAIN),
+                                                 "Invalid message signature (%x != %x).",
+                                                 message.nlh->magic, htobe32(UDEV_MONITOR_MAGIC));
+
+                if (message.nlh->properties_off + 32 > (size_t) n)
+                        return log_monitor_errno(m, SYNTHETIC_ERRNO(EAGAIN),
+                                                 "Invalid offset for properties (%u > %zi).",
+                                                 message.nlh->properties_off + 32, n);
+
+                offset = message.nlh->properties_off;
+
+                /* devices received from udev are always initialized */
+                is_initialized = true;
+
+        } else {
+                /* check kernel message header */
+                if (!strstr(message.nulstr, "@/"))
+                        return log_monitor_errno(m, SYNTHETIC_ERRNO(EAGAIN), "Invalid message header.");
+
+                offset = strlen(message.nulstr) + 1;
+                if (offset >= (size_t) n)
+                        return log_monitor_errno(m, SYNTHETIC_ERRNO(EAGAIN), "Invalid message length.");
+        }
+
+        r = device_new_from_nulstr(&device, message.nulstr + offset, n - offset);
+        if (r < 0)
+                return log_monitor_errno(m, r, "Failed to create device from received message: %m");
+
+        if (is_initialized)
+                device_set_is_initialized(device);
+
+        /* Skip device, if it does not pass the current filter */
+        r = passes_filter(m, device);
+        if (r < 0)
+                return log_device_monitor_errno(device, m, r, "Failed to check received device passing filter: %m");
+        if (r == 0)
+                log_device_monitor(device, m, "Received device does not pass filter, ignoring.");
+        else
+                *ret = TAKE_PTR(device);
+
+        return r;
+}
+
+static uint32_t string_hash32(const char *str) {
+        return MurmurHash2(str, strlen(str), 0);
+}
+
+/* Get a bunch of bit numbers out of the hash, and set the bits in our bit field */
+static uint64_t string_bloom64(const char *str) {
+        uint64_t bits = 0;
+        uint32_t hash = string_hash32(str);
+
+        bits |= UINT64_C(1) << (hash & 63);
+        bits |= UINT64_C(1) << ((hash >> 6) & 63);
+        bits |= UINT64_C(1) << ((hash >> 12) & 63);
+        bits |= UINT64_C(1) << ((hash >> 18) & 63);
+        return bits;
+}
+
+int device_monitor_send_device(
+                sd_device_monitor *m,
+                sd_device_monitor *destination,
+                sd_device *device) {
+
+        monitor_netlink_header nlh = {
+                .prefix = "libudev",
+                .magic = htobe32(UDEV_MONITOR_MAGIC),
+                .header_size = sizeof nlh,
+        };
+        struct iovec iov[2] = {
+                { .iov_base = &nlh, .iov_len = sizeof nlh },
+        };
+        struct msghdr smsg = {
+                .msg_iov = iov,
+                .msg_iovlen = 2,
+        };
+        /* default destination for sending */
+        union sockaddr_union default_destination = {
+                .nl.nl_family = AF_NETLINK,
+                .nl.nl_groups = MONITOR_GROUP_UDEV,
+        };
+        uint64_t tag_bloom_bits;
+        const char *buf, *val;
+        ssize_t count;
+        size_t blen;
+        int r;
+
+        assert(m);
+        assert(device);
+
+        r = device_get_properties_nulstr(device, &buf, &blen);
+        if (r < 0)
+                return log_device_monitor_errno(device, m, r, "Failed to get device properties: %m");
+        if (blen < 32)
+                return log_device_monitor_errno(device, m, SYNTHETIC_ERRNO(EINVAL),
+                                                "Length of device property nulstr is too small to contain valid device information.");
+
+        /* fill in versioned header */
+        r = sd_device_get_subsystem(device, &val);
+        if (r < 0)
+                return log_device_monitor_errno(device, m, r, "Failed to get device subsystem: %m");
+        nlh.filter_subsystem_hash = htobe32(string_hash32(val));
+
+        if (sd_device_get_devtype(device, &val) >= 0)
+                nlh.filter_devtype_hash = htobe32(string_hash32(val));
+
+        /* add tag bloom filter */
+        tag_bloom_bits = 0;
+        FOREACH_DEVICE_TAG(device, tag)
+                tag_bloom_bits |= string_bloom64(tag);
+
+        if (tag_bloom_bits > 0) {
+                nlh.filter_tag_bloom_hi = htobe32(tag_bloom_bits >> 32);
+                nlh.filter_tag_bloom_lo = htobe32(tag_bloom_bits & 0xffffffff);
+        }
+
+        /* add properties list */
+        nlh.properties_off = iov[0].iov_len;
+        nlh.properties_len = blen;
+        iov[1] = IOVEC_MAKE((char*) buf, blen);
+
+        /*
+         * Use custom address for target, or the default one.
+         *
+         * If we send to a multicast group, we will get
+         * ECONNREFUSED, which is expected.
+         */
+        smsg.msg_name = destination ? &destination->snl : &default_destination;
+        smsg.msg_namelen = sizeof(struct sockaddr_nl);
+        count = sendmsg(m->sock, &smsg, 0);
+        if (count < 0) {
+                if (!destination && errno == ECONNREFUSED) {
+                        log_device_monitor(device, m, "Passed to netlink monitor.");
+                        return 0;
+                } else
+                        return log_device_monitor_errno(device, m, errno, "Failed to send device to netlink monitor: %m");
+        }
+
+        log_device_monitor(device, m, "Passed %zi byte to netlink monitor.", count);
+        return count;
+}
+
+static void bpf_stmt(struct sock_filter *ins, unsigned *i,
+                     unsigned short code, unsigned data) {
+        ins[(*i)++] = (struct sock_filter) {
+                .code = code,
+                .k = data,
+        };
+}
+
+static void bpf_jmp(struct sock_filter *ins, unsigned *i,
+                    unsigned short code, unsigned data,
+                    unsigned short jt, unsigned short jf) {
+        ins[(*i)++] = (struct sock_filter) {
+                .code = code,
+                .jt = jt,
+                .jf = jf,
+                .k = data,
+        };
+}
+
+_public_ int sd_device_monitor_filter_update(sd_device_monitor *m) {
+        struct sock_filter ins[512] = {};
+        struct sock_fprog filter;
+        const char *subsystem, *devtype, *tag;
+        unsigned i = 0;
+
+        assert_return(m, -EINVAL);
+
+        if (m->filter_uptodate)
+                return 0;
+
+        if (m->snl.nl.nl_groups == MONITOR_GROUP_KERNEL ||
+            (hashmap_isempty(m->subsystem_filter) &&
+             set_isempty(m->tag_filter))) {
+                m->filter_uptodate = true;
+                return 0;
+        }
+
+        /* load magic in A */
+        bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, magic));
+        /* jump if magic matches */
+        bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, UDEV_MONITOR_MAGIC, 1, 0);
+        /* wrong magic, pass packet */
+        bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
+
+        if (!set_isempty(m->tag_filter)) {
+                int tag_matches = set_size(m->tag_filter);
+
+                /* add all tags matches */
+                SET_FOREACH(tag, m->tag_filter) {
+                        uint64_t tag_bloom_bits = string_bloom64(tag);
+                        uint32_t tag_bloom_hi = tag_bloom_bits >> 32;
+                        uint32_t tag_bloom_lo = tag_bloom_bits & 0xffffffff;
+
+                        /* load device bloom bits in A */
+                        bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_tag_bloom_hi));
+                        /* clear bits (tag bits & bloom bits) */
+                        bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_hi);
+                        /* jump to next tag if it does not match */
+                        bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_hi, 0, 3);
+
+                        /* load device bloom bits in A */
+                        bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_tag_bloom_lo));
+                        /* clear bits (tag bits & bloom bits) */
+                        bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_lo);
+                        /* jump behind end of tag match block if tag matches */
+                        tag_matches--;
+                        bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_lo, 1 + (tag_matches * 6), 0);
+                }
+
+                /* nothing matched, drop packet */
+                bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
+        }
+
+        /* add all subsystem matches */
+        if (!hashmap_isempty(m->subsystem_filter)) {
+                HASHMAP_FOREACH_KEY(devtype, subsystem, m->subsystem_filter) {
+                        uint32_t hash = string_hash32(subsystem);
+
+                        /* load device subsystem value in A */
+                        bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_subsystem_hash));
+                        if (!devtype) {
+                                /* jump if subsystem does not match */
+                                bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
+                        } else {
+                                /* jump if subsystem does not match */
+                                bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 3);
+                                /* load device devtype value in A */
+                                bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_devtype_hash));
+                                /* jump if value does not match */
+                                hash = string_hash32(devtype);
+                                bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
+                        }
+
+                        /* matched, pass packet */
+                        bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
+
+                        if (i+1 >= ELEMENTSOF(ins))
+                                return -E2BIG;
+                }
+
+                /* nothing matched, drop packet */
+                bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
+        }
+
+        /* matched, pass packet */
+        bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
+
+        /* install filter */
+        filter = (struct sock_fprog) {
+                .len = i,
+                .filter = ins,
+        };
+        if (setsockopt(m->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) < 0)
+                return -errno;
+
+        m->filter_uptodate = true;
+        return 0;
+}
+
+_public_ int sd_device_monitor_filter_add_match_subsystem_devtype(sd_device_monitor *m, const char *subsystem, const char *devtype) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(subsystem, -EINVAL);
+
+        /* Do not use string_has_ops_free_free or hashmap_put_strdup() here, as this may be called
+         * multiple times with the same subsystem but different devtypes. */
+        r = hashmap_put_strdup_full(&m->subsystem_filter, &trivial_hash_ops_free_free, subsystem, devtype);
+        if (r <= 0)
+                return r;
+
+        m->filter_uptodate = false;
+        return r;
+}
+
+_public_ int sd_device_monitor_filter_add_match_tag(sd_device_monitor *m, const char *tag) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(tag, -EINVAL);
+
+        r = set_put_strdup(&m->tag_filter, tag);
+        if (r <= 0)
+                return r;
+
+        m->filter_uptodate = false;
+        return r;
+}
+
+_public_ int sd_device_monitor_filter_add_match_sysattr(sd_device_monitor *m, const char *sysattr, const char *value, int match) {
+        Hashmap **hashmap;
+
+        assert_return(m, -EINVAL);
+        assert_return(sysattr, -EINVAL);
+
+        if (match)
+                hashmap = &m->match_sysattr_filter;
+        else
+                hashmap = &m->nomatch_sysattr_filter;
+
+        /* TODO: unset m->filter_uptodate on success when we support this filter on BPF. */
+        return update_match_strv(hashmap, sysattr, value, /* clear_on_null = */ true);
+}
+
+_public_ int sd_device_monitor_filter_add_match_parent(sd_device_monitor *m, sd_device *device, int match) {
+        const char *syspath;
+        Set **set;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(device, -EINVAL);
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        if (match)
+                set = &m->match_parent_filter;
+        else
+                set = &m->nomatch_parent_filter;
+
+        /* TODO: unset m->filter_uptodate on success when we support this filter on BPF. */
+        return set_put_strdup(set, syspath);
+}
+
+_public_ int sd_device_monitor_filter_remove(sd_device_monitor *m) {
+        static const struct sock_fprog filter = { 0, NULL };
+
+        assert_return(m, -EINVAL);
+
+        m->subsystem_filter = hashmap_free(m->subsystem_filter);
+        m->tag_filter = set_free(m->tag_filter);
+        m->match_sysattr_filter = hashmap_free(m->match_sysattr_filter);
+        m->nomatch_sysattr_filter = hashmap_free(m->nomatch_sysattr_filter);
+        m->match_parent_filter = set_free(m->match_parent_filter);
+        m->nomatch_parent_filter = set_free(m->nomatch_parent_filter);
+
+        if (setsockopt(m->sock, SOL_SOCKET, SO_DETACH_FILTER, &filter, sizeof(filter)) < 0)
+                return -errno;
+
+        m->filter_uptodate = true;
+        return 0;
+}
diff --git a/src/libsystemd/sd-device/device-private.c b/src/libsystemd/sd-device/device-private.c
new file mode 100644
index 0000000..0edabfb
--- /dev/null
+++ b/src/libsystemd/sd-device/device-private.c
@@ -0,0 +1,903 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <ctype.h>
+#include <net/if.h>
+#include <sys/types.h>
+
+#include "sd-device.h"
+
+#include "alloc-util.h"
+#include "device-internal.h"
+#include "device-private.h"
+#include "device-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "hashmap.h"
+#include "macro.h"
+#include "mkdir.h"
+#include "nulstr-util.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "set.h"
+#include "stdio-util.h"
+#include "string-table.h"
+#include "string-util.h"
+#include "strv.h"
+#include "strxcpyx.h"
+#include "tmpfile-util.h"
+#include "user-util.h"
+
+int device_add_property(sd_device *device, const char *key, const char *value) {
+        int r;
+
+        assert(device);
+        assert(key);
+
+        r = device_add_property_aux(device, key, value, false);
+        if (r < 0)
+                return r;
+
+        if (key[0] != '.') {
+                r = device_add_property_aux(device, key, value, true);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int device_add_propertyf(sd_device *device, const char *key, const char *format, ...) {
+        _cleanup_free_ char *value = NULL;
+        va_list ap;
+        int r;
+
+        assert(device);
+        assert(key);
+
+        if (!format)
+                return device_add_property(device, key, NULL);
+
+        va_start(ap, format);
+        r = vasprintf(&value, format, ap);
+        va_end(ap);
+
+        if (r < 0)
+                return -ENOMEM;
+
+        return device_add_property(device, key, value);
+}
+
+void device_set_devlink_priority(sd_device *device, int priority) {
+        assert(device);
+
+        device->devlink_priority = priority;
+}
+
+void device_set_is_initialized(sd_device *device) {
+        assert(device);
+
+        device->is_initialized = true;
+}
+
+int device_ensure_usec_initialized(sd_device *device, sd_device *device_old) {
+        usec_t when;
+
+        assert(device);
+
+        if (device_old && device_old->usec_initialized > 0)
+                when = device_old->usec_initialized;
+        else
+                when = now(CLOCK_MONOTONIC);
+
+        return device_set_usec_initialized(device, when);
+}
+
+uint64_t device_get_properties_generation(sd_device *device) {
+        assert(device);
+
+        return device->properties_generation;
+}
+
+uint64_t device_get_tags_generation(sd_device *device) {
+        assert(device);
+
+        return device->tags_generation;
+}
+
+uint64_t device_get_devlinks_generation(sd_device *device) {
+        assert(device);
+
+        return device->devlinks_generation;
+}
+
+int device_get_devnode_mode(sd_device *device, mode_t *ret) {
+        int r;
+
+        assert(device);
+
+        r = device_read_db(device);
+        if (r < 0)
+                return r;
+
+        if (device->devmode == MODE_INVALID)
+                return -ENOENT;
+
+        if (ret)
+                *ret = device->devmode;
+
+        return 0;
+}
+
+int device_get_devnode_uid(sd_device *device, uid_t *ret) {
+        int r;
+
+        assert(device);
+
+        r = device_read_db(device);
+        if (r < 0)
+                return r;
+
+        if (device->devuid == UID_INVALID)
+                return -ENOENT;
+
+        if (ret)
+                *ret = device->devuid;
+
+        return 0;
+}
+
+static int device_set_devuid(sd_device *device, const char *uid) {
+        uid_t u;
+        int r;
+
+        assert(device);
+        assert(uid);
+
+        r = parse_uid(uid, &u);
+        if (r < 0)
+                return r;
+
+        r = device_add_property_internal(device, "DEVUID", uid);
+        if (r < 0)
+                return r;
+
+        device->devuid = u;
+
+        return 0;
+}
+
+int device_get_devnode_gid(sd_device *device, gid_t *ret) {
+        int r;
+
+        assert(device);
+
+        r = device_read_db(device);
+        if (r < 0)
+                return r;
+
+        if (device->devgid == GID_INVALID)
+                return -ENOENT;
+
+        if (ret)
+                *ret = device->devgid;
+
+        return 0;
+}
+
+static int device_set_devgid(sd_device *device, const char *gid) {
+        gid_t g;
+        int r;
+
+        assert(device);
+        assert(gid);
+
+        r = parse_gid(gid, &g);
+        if (r < 0)
+                return r;
+
+        r = device_add_property_internal(device, "DEVGID", gid);
+        if (r < 0)
+                return r;
+
+        device->devgid = g;
+
+        return 0;
+}
+
+int device_set_action(sd_device *device, sd_device_action_t a) {
+        int r;
+
+        assert(device);
+        assert(a >= 0 && a < _SD_DEVICE_ACTION_MAX);
+
+        r = device_add_property_internal(device, "ACTION", device_action_to_string(a));
+        if (r < 0)
+                return r;
+
+        device->action = a;
+
+        return 0;
+}
+
+static int device_set_action_from_string(sd_device *device, const char *action) {
+        sd_device_action_t a;
+
+        assert(device);
+        assert(action);
+
+        a = device_action_from_string(action);
+        if (a < 0)
+                return a;
+
+        return device_set_action(device, a);
+}
+
+static int device_set_seqnum(sd_device *device, const char *str) {
+        uint64_t seqnum;
+        int r;
+
+        assert(device);
+        assert(str);
+
+        r = safe_atou64(str, &seqnum);
+        if (r < 0)
+                return r;
+        if (seqnum == 0)
+                return -EINVAL;
+
+        r = device_add_property_internal(device, "SEQNUM", str);
+        if (r < 0)
+                return r;
+
+        device->seqnum = seqnum;
+
+        return 0;
+}
+
+static int device_amend(sd_device *device, const char *key, const char *value) {
+        int r;
+
+        assert(device);
+        assert(key);
+        assert(value);
+
+        if (streq(key, "DEVPATH")) {
+                char *path;
+
+                path = strjoina("/sys", value);
+
+                /* the caller must verify or trust this data (e.g., if it comes from the kernel) */
+                r = device_set_syspath(device, path, false);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set syspath to '%s': %m", path);
+        } else if (streq(key, "SUBSYSTEM")) {
+                r = device_set_subsystem(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set subsystem to '%s': %m", value);
+        } else if (streq(key, "DEVTYPE")) {
+                r = device_set_devtype(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set devtype to '%s': %m", value);
+        } else if (streq(key, "DEVNAME")) {
+                r = device_set_devname(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set devname to '%s': %m", value);
+        } else if (streq(key, "USEC_INITIALIZED")) {
+                usec_t t;
+
+                r = safe_atou64(value, &t);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to parse timestamp '%s': %m", value);
+
+                r = device_set_usec_initialized(device, t);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set usec-initialized to '%s': %m", value);
+        } else if (streq(key, "DRIVER")) {
+                r = device_set_driver(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set driver to '%s': %m", value);
+        } else if (streq(key, "IFINDEX")) {
+                r = device_set_ifindex(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set ifindex to '%s': %m", value);
+        } else if (streq(key, "DEVMODE")) {
+                r = device_set_devmode(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set devmode to '%s': %m", value);
+        } else if (streq(key, "DEVUID")) {
+                r = device_set_devuid(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set devuid to '%s': %m", value);
+        } else if (streq(key, "DEVGID")) {
+                r = device_set_devgid(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set devgid to '%s': %m", value);
+        } else if (streq(key, "ACTION")) {
+                r = device_set_action_from_string(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set action to '%s': %m", value);
+        } else if (streq(key, "SEQNUM")) {
+                r = device_set_seqnum(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set SEQNUM to '%s': %m", value);
+        } else if (streq(key, "DISKSEQ")) {
+                r = device_set_diskseq(device, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set DISKSEQ to '%s': %m", value);
+        } else if (streq(key, "DEVLINKS")) {
+                for (const char *p = value;;) {
+                        _cleanup_free_ char *word = NULL;
+
+                        /* udev rules may set escaped strings, and sd-device does not modify the input
+                         * strings. So, it is also necessary to keep the strings received through
+                         * sd-device-monitor. */
+                        r = extract_first_word(&p, &word, NULL, EXTRACT_RETAIN_ESCAPE);
+                        if (r < 0)
+                                return r;
+                        if (r == 0)
+                                break;
+
+                        r = device_add_devlink(device, word);
+                        if (r < 0)
+                                return log_device_debug_errno(device, r, "sd-device: Failed to add devlink '%s': %m", word);
+                }
+        } else if (STR_IN_SET(key, "TAGS", "CURRENT_TAGS")) {
+                for (const char *p = value;;) {
+                        _cleanup_free_ char *word = NULL;
+
+                        r = extract_first_word(&p, &word, ":", EXTRACT_DONT_COALESCE_SEPARATORS);
+                        if (r < 0)
+                                return r;
+                        if (r == 0)
+                                break;
+                        if (isempty(word))
+                                continue;
+
+                        r = device_add_tag(device, word, streq(key, "CURRENT_TAGS"));
+                        if (r < 0)
+                                return log_device_debug_errno(device, r, "sd-device: Failed to add tag '%s': %m", word);
+                }
+        } else if (streq(key, "UDEV_DATABASE_VERSION")) {
+                r = safe_atou(value, &device->database_version);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to parse udev database version '%s': %m", value);
+        } else {
+                r = device_add_property_internal(device, key, value);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to add property '%s=%s': %m", key, value);
+        }
+
+        return 0;
+}
+
+static int device_append(
+                sd_device *device,
+                char *key,
+                const char **_major,
+                const char **_minor) {
+
+        const char *major = NULL, *minor = NULL;
+        char *value;
+        int r;
+
+        assert(device);
+        assert(key);
+        assert(_major);
+        assert(_minor);
+
+        value = strchr(key, '=');
+        if (!value)
+                return log_device_debug_errno(device, SYNTHETIC_ERRNO(EINVAL),
+                                              "sd-device: Not a key-value pair: '%s'", key);
+
+        *value = '\0';
+
+        value++;
+
+        if (streq(key, "MAJOR"))
+                major = value;
+        else if (streq(key, "MINOR"))
+                minor = value;
+        else {
+                r = device_amend(device, key, value);
+                if (r < 0)
+                        return r;
+        }
+
+        if (major)
+                *_major = major;
+
+        if (minor)
+                *_minor = minor;
+
+        return 0;
+}
+
+void device_seal(sd_device *device) {
+        assert(device);
+
+        device->sealed = true;
+}
+
+static int device_verify(sd_device *device) {
+        int r;
+
+        assert(device);
+
+        if (!device->devpath || !device->subsystem || device->action < 0 || device->seqnum == 0)
+                return log_device_debug_errno(device, SYNTHETIC_ERRNO(EINVAL),
+                                              "sd-device: Device created from strv or nulstr lacks devpath, subsystem, action or seqnum.");
+
+        if (streq(device->subsystem, "drivers")) {
+                r = device_set_drivers_subsystem(device);
+                if (r < 0)
+                        return r;
+        }
+
+        device->sealed = true;
+
+        return 0;
+}
+
+int device_new_from_strv(sd_device **ret, char **strv) {
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+        const char *major = NULL, *minor = NULL;
+        int r;
+
+        assert(ret);
+        assert(strv);
+
+        r = device_new_aux(&device);
+        if (r < 0)
+                return r;
+
+        STRV_FOREACH(key, strv) {
+                r = device_append(device, *key, &major, &minor);
+                if (r < 0)
+                        return r;
+        }
+
+        if (major) {
+                r = device_set_devnum(device, major, minor);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set devnum %s:%s: %m", major, minor);
+        }
+
+        r = device_verify(device);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(device);
+
+        return 0;
+}
+
+int device_new_from_nulstr(sd_device **ret, char *nulstr, size_t len) {
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+        const char *major = NULL, *minor = NULL;
+        int r;
+
+        assert(ret);
+        assert(nulstr);
+        assert(len);
+
+        r = device_new_aux(&device);
+        if (r < 0)
+                return r;
+
+        for (size_t i = 0; i < len; ) {
+                char *key;
+                const char *end;
+
+                key = nulstr + i;
+                end = memchr(key, '\0', len - i);
+                if (!end)
+                        return log_device_debug_errno(device, SYNTHETIC_ERRNO(EINVAL),
+                                                      "sd-device: Failed to parse nulstr");
+
+                i += end - key + 1;
+
+                /* netlink messages for some devices contain an unwanted newline at the end of value.
+                 * Let's drop the newline and remaining characters after the newline. */
+                truncate_nl(key);
+
+                r = device_append(device, key, &major, &minor);
+                if (r < 0)
+                        return r;
+        }
+
+        if (major) {
+                r = device_set_devnum(device, major, minor);
+                if (r < 0)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set devnum %s:%s: %m", major, minor);
+        }
+
+        r = device_verify(device);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(device);
+
+        return 0;
+}
+
+static int device_update_properties_bufs(sd_device *device) {
+        _cleanup_free_ char **buf_strv = NULL, *buf_nulstr = NULL;
+        size_t nulstr_len = 0, num = 0;
+
+        assert(device);
+
+        if (!device->properties_buf_outdated)
+                return 0;
+
+        /* append udev database version */
+        buf_nulstr = newdup(char, "UDEV_DATABASE_VERSION=" STRINGIFY(LATEST_UDEV_DATABASE_VERSION) "\0",
+                            STRLEN("UDEV_DATABASE_VERSION=" STRINGIFY(LATEST_UDEV_DATABASE_VERSION)) + 2);
+        if (!buf_nulstr)
+                return -ENOMEM;
+
+        nulstr_len += STRLEN("UDEV_DATABASE_VERSION=" STRINGIFY(LATEST_UDEV_DATABASE_VERSION)) + 1;
+        num++;
+
+        FOREACH_DEVICE_PROPERTY(device, prop, val) {
+                size_t len = 0;
+
+                len = strlen(prop) + 1 + strlen(val);
+
+                buf_nulstr = GREEDY_REALLOC0(buf_nulstr, nulstr_len + len + 2);
+                if (!buf_nulstr)
+                        return -ENOMEM;
+
+                strscpyl(buf_nulstr + nulstr_len, len + 1, prop, "=", val, NULL);
+                nulstr_len += len + 1;
+                num++;
+        }
+
+        /* build buf_strv from buf_nulstr */
+        buf_strv = new0(char*, num + 1);
+        if (!buf_strv)
+                return -ENOMEM;
+
+        size_t i = 0;
+        NULSTR_FOREACH(p, buf_nulstr)
+                buf_strv[i++] = p;
+        assert(i == num);
+
+        free_and_replace(device->properties_nulstr, buf_nulstr);
+        device->properties_nulstr_len = nulstr_len;
+        free_and_replace(device->properties_strv, buf_strv);
+
+        device->properties_buf_outdated = false;
+        return 0;
+}
+
+int device_get_properties_nulstr(sd_device *device, const char **ret_nulstr, size_t *ret_len) {
+        int r;
+
+        assert(device);
+
+        r = device_update_properties_bufs(device);
+        if (r < 0)
+                return r;
+
+        if (ret_nulstr)
+                *ret_nulstr = device->properties_nulstr;
+        if (ret_len)
+                *ret_len = device->properties_nulstr_len;
+
+        return 0;
+}
+
+int device_get_properties_strv(sd_device *device, char ***ret) {
+        int r;
+
+        assert(device);
+
+        r = device_update_properties_bufs(device);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = device->properties_strv;
+
+        return 0;
+}
+
+int device_get_devlink_priority(sd_device *device, int *ret) {
+        int r;
+
+        assert(device);
+
+        r = device_read_db(device);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = device->devlink_priority;
+
+        return 0;
+}
+
+int device_clone_with_db(sd_device *device, sd_device **ret) {
+        _cleanup_(sd_device_unrefp) sd_device *dest = NULL;
+        const char *key, *val;
+        int r;
+
+        assert(device);
+        assert(ret);
+
+        /* The device may be already removed. Let's copy minimal set of information that was obtained through
+         * netlink socket. */
+
+        r = device_new_aux(&dest);
+        if (r < 0)
+                return r;
+
+        /* Seal device to prevent reading the uevent file, as the device may have been already removed. */
+        dest->sealed = true;
+
+        /* Copy syspath, then also devname, sysname or sysnum can be obtained. */
+        r = device_set_syspath(dest, device->syspath, false);
+        if (r < 0)
+                return r;
+
+        /* Copy other information stored in database. Here, do not use FOREACH_DEVICE_PROPERTY() and
+         * sd_device_get_property_value(), as they calls device_properties_prepare() ->
+         * device_read_uevent_file(), but as commented in the above, the device may be already removed and
+         * reading uevent file may fail. */
+        ORDERED_HASHMAP_FOREACH_KEY(val, key, device->properties) {
+                if (streq(key, "MINOR"))
+                        continue;
+
+                if (streq(key, "MAJOR")) {
+                        const char *minor = NULL;
+
+                        minor = ordered_hashmap_get(device->properties, "MINOR");
+                        r = device_set_devnum(dest, val, minor);
+                } else
+                        r = device_amend(dest, key, val);
+                if (r < 0)
+                        return r;
+
+                if (streq(key, "SUBSYSTEM") && streq(val, "drivers")) {
+                        r = free_and_strdup(&dest->driver_subsystem, device->driver_subsystem);
+                        if (r < 0)
+                                return r;
+                }
+        }
+
+        /* Finally, read the udev database. */
+        r = device_read_db_internal(dest, /* force = */ true);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(dest);
+        return 0;
+}
+
+void device_cleanup_tags(sd_device *device) {
+        assert(device);
+
+        device->all_tags = set_free_free(device->all_tags);
+        device->current_tags = set_free_free(device->current_tags);
+        device->property_tags_outdated = true;
+        device->tags_generation++;
+}
+
+void device_cleanup_devlinks(sd_device *device) {
+        assert(device);
+
+        set_free_free(device->devlinks);
+        device->devlinks = NULL;
+        device->property_devlinks_outdated = true;
+        device->devlinks_generation++;
+}
+
+void device_remove_tag(sd_device *device, const char *tag) {
+        assert(device);
+        assert(tag);
+
+        free(set_remove(device->current_tags, tag));
+        device->property_tags_outdated = true;
+        device->tags_generation++;
+}
+
+static int device_tag(sd_device *device, const char *tag, bool add) {
+        const char *id;
+        char *path;
+        int r;
+
+        assert(device);
+        assert(tag);
+
+        r = device_get_device_id(device, &id);
+        if (r < 0)
+                return r;
+
+        path = strjoina("/run/udev/tags/", tag, "/", id);
+
+        if (add)
+                return touch_file(path, true, USEC_INFINITY, UID_INVALID, GID_INVALID, 0444);
+
+        if (unlink(path) < 0 && errno != ENOENT)
+                return -errno;
+
+        return 0;
+}
+
+int device_tag_index(sd_device *device, sd_device *device_old, bool add) {
+        int r = 0, k;
+
+        if (add && device_old)
+                /* delete possible left-over tags */
+                FOREACH_DEVICE_TAG(device_old, tag)
+                        if (!sd_device_has_tag(device, tag)) {
+                                k = device_tag(device_old, tag, false);
+                                if (r >= 0 && k < 0)
+                                        r = k;
+                        }
+
+        FOREACH_DEVICE_TAG(device, tag) {
+                k = device_tag(device, tag, add);
+                if (r >= 0 && k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static bool device_has_info(sd_device *device) {
+        assert(device);
+
+        if (!set_isempty(device->devlinks))
+                return true;
+
+        if (device->devlink_priority != 0)
+                return true;
+
+        if (!ordered_hashmap_isempty(device->properties_db))
+                return true;
+
+        if (!set_isempty(device->all_tags))
+                return true;
+
+        if (!set_isempty(device->current_tags))
+                return true;
+
+        return false;
+}
+
+void device_set_db_persist(sd_device *device) {
+        assert(device);
+
+        device->db_persist = true;
+}
+
+int device_update_db(sd_device *device) {
+        const char *id;
+        char *path;
+        _cleanup_fclose_ FILE *f = NULL;
+        _cleanup_(unlink_and_freep) char *path_tmp = NULL;
+        bool has_info;
+        int r;
+
+        assert(device);
+
+        has_info = device_has_info(device);
+
+        r = device_get_device_id(device, &id);
+        if (r < 0)
+                return r;
+
+        path = strjoina("/run/udev/data/", id);
+
+        /* do not store anything for otherwise empty devices */
+        if (!has_info && major(device->devnum) == 0 && device->ifindex == 0) {
+                if (unlink(path) < 0 && errno != ENOENT)
+                        return -errno;
+
+                return 0;
+        }
+
+        /* write a database file */
+        r = mkdir_parents(path, 0755);
+        if (r < 0)
+                return r;
+
+        r = fopen_temporary(path, &f, &path_tmp);
+        if (r < 0)
+                return r;
+
+        /* set 'sticky' bit to indicate that we should not clean the database when we transition from initrd
+         * to the real root */
+        if (fchmod(fileno(f), device->db_persist ? 01644 : 0644) < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        if (has_info) {
+                const char *property, *value, *ct;
+
+                if (major(device->devnum) > 0) {
+                        FOREACH_DEVICE_DEVLINK(device, devlink)
+                                fprintf(f, "S:%s\n", devlink + STRLEN("/dev/"));
+
+                        if (device->devlink_priority != 0)
+                                fprintf(f, "L:%i\n", device->devlink_priority);
+                }
+
+                if (device->usec_initialized > 0)
+                        fprintf(f, "I:"USEC_FMT"\n", device->usec_initialized);
+
+                ORDERED_HASHMAP_FOREACH_KEY(value, property, device->properties_db)
+                        fprintf(f, "E:%s=%s\n", property, value);
+
+                FOREACH_DEVICE_TAG(device, tag)
+                        fprintf(f, "G:%s\n", tag); /* Any tag */
+
+                SET_FOREACH(ct, device->current_tags)
+                        fprintf(f, "Q:%s\n", ct); /* Current tag */
+
+                /* Always write the latest database version here, instead of the value stored in
+                 * device->database_version, as which may be 0. */
+                fputs("V:" STRINGIFY(LATEST_UDEV_DATABASE_VERSION) "\n", f);
+        }
+
+        r = fflush_and_check(f);
+        if (r < 0)
+                goto fail;
+
+        if (rename(path_tmp, path) < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        path_tmp = mfree(path_tmp);
+
+        log_device_debug(device, "sd-device: Created %s file '%s' for '%s'", has_info ? "db" : "empty",
+                         path, device->devpath);
+
+        return 0;
+
+fail:
+        (void) unlink(path);
+
+        return log_device_debug_errno(device, r, "sd-device: Failed to create %s file '%s' for '%s'", has_info ? "db" : "empty", path, device->devpath);
+}
+
+int device_delete_db(sd_device *device) {
+        const char *id;
+        char *path;
+        int r;
+
+        assert(device);
+
+        r = device_get_device_id(device, &id);
+        if (r < 0)
+                return r;
+
+        path = strjoina("/run/udev/data/", id);
+
+        if (unlink(path) < 0 && errno != ENOENT)
+                return -errno;
+
+        return 0;
+}
+
+static const char* const device_action_table[_SD_DEVICE_ACTION_MAX] = {
+        [SD_DEVICE_ADD]     = "add",
+        [SD_DEVICE_REMOVE]  = "remove",
+        [SD_DEVICE_CHANGE]  = "change",
+        [SD_DEVICE_MOVE]    = "move",
+        [SD_DEVICE_ONLINE]  = "online",
+        [SD_DEVICE_OFFLINE] = "offline",
+        [SD_DEVICE_BIND]    = "bind",
+        [SD_DEVICE_UNBIND]  = "unbind",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(device_action, sd_device_action_t);
+
+void dump_device_action_table(void) {
+        DUMP_STRING_TABLE(device_action, sd_device_action_t, _SD_DEVICE_ACTION_MAX);
+}
diff --git a/src/libsystemd/sd-device/device-private.h b/src/libsystemd/sd-device/device-private.h
new file mode 100644
index 0000000..b903d1a
--- /dev/null
+++ b/src/libsystemd/sd-device/device-private.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <dirent.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "sd-device.h"
+
+#include "macro.h"
+
+int device_new_from_mode_and_devnum(sd_device **ret, mode_t mode, dev_t devnum);
+int device_new_from_nulstr(sd_device **ret, char *nulstr, size_t len);
+int device_new_from_strv(sd_device **ret, char **strv);
+
+int device_opendir(sd_device *device, const char *subdir, DIR **ret);
+
+int device_get_property_bool(sd_device *device, const char *key);
+int device_get_property_int(sd_device *device, const char *key, int *ret);
+int device_get_sysattr_int(sd_device *device, const char *sysattr, int *ret_value);
+int device_get_sysattr_unsigned(sd_device *device, const char *sysattr, unsigned *ret_value);
+int device_get_sysattr_bool(sd_device *device, const char *sysattr);
+int device_get_device_id(sd_device *device, const char **ret);
+int device_get_devlink_priority(sd_device *device, int *ret);
+int device_get_devnode_mode(sd_device *device, mode_t *ret);
+int device_get_devnode_uid(sd_device *device, uid_t *ret);
+int device_get_devnode_gid(sd_device *device, gid_t *ret);
+
+void device_clear_sysattr_cache(sd_device *device);
+int device_cache_sysattr_value(sd_device *device, const char *key, char *value);
+int device_get_cached_sysattr_value(sd_device *device, const char *key, const char **ret_value);
+
+void device_seal(sd_device *device);
+void device_set_is_initialized(sd_device *device);
+void device_set_db_persist(sd_device *device);
+void device_set_devlink_priority(sd_device *device, int priority);
+int device_ensure_usec_initialized(sd_device *device, sd_device *device_old);
+int device_add_devlink(sd_device *device, const char *devlink);
+int device_remove_devlink(sd_device *device, const char *devlink);
+bool device_has_devlink(sd_device *device, const char *devlink);
+int device_add_property(sd_device *device, const char *property, const char *value);
+int device_add_propertyf(sd_device *device, const char *key, const char *format, ...) _printf_(3, 4);
+int device_add_tag(sd_device *device, const char *tag, bool both);
+void device_remove_tag(sd_device *device, const char *tag);
+void device_cleanup_tags(sd_device *device);
+void device_cleanup_devlinks(sd_device *device);
+
+uint64_t device_get_properties_generation(sd_device *device);
+uint64_t device_get_tags_generation(sd_device *device);
+uint64_t device_get_devlinks_generation(sd_device *device);
+
+int device_properties_prepare(sd_device *device);
+int device_get_properties_nulstr(sd_device *device, const char **ret_nulstr, size_t *ret_len);
+int device_get_properties_strv(sd_device *device, char ***ret);
+
+int device_clone_with_db(sd_device *device, sd_device **ret);
+
+int device_tag_index(sd_device *dev, sd_device *dev_old, bool add);
+int device_update_db(sd_device *device);
+int device_delete_db(sd_device *device);
+int device_read_db_internal_filename(sd_device *device, const char *filename); /* For fuzzer */
+int device_read_db_internal(sd_device *device, bool force);
+static inline int device_read_db(sd_device *device) {
+        return device_read_db_internal(device, false);
+}
+
+int device_read_uevent_file(sd_device *device);
+
+int device_set_action(sd_device *device, sd_device_action_t a);
+sd_device_action_t device_action_from_string(const char *s) _pure_;
+const char *device_action_to_string(sd_device_action_t a) _const_;
+void dump_device_action_table(void);
diff --git a/src/libsystemd/sd-device/device-util.c b/src/libsystemd/sd-device/device-util.c
new file mode 100644
index 0000000..529eff2
--- /dev/null
+++ b/src/libsystemd/sd-device/device-util.c
@@ -0,0 +1,141 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "device-private.h"
+#include "device-util.h"
+#include "devnum-util.h"
+#include "fd-util.h"
+#include "string-util.h"
+#include "strv.h"
+
+int devname_from_devnum(mode_t mode, dev_t devnum, char **ret) {
+        _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
+        _cleanup_free_ char *s = NULL;
+        const char *devname;
+        int r;
+
+        assert(ret);
+
+        if (devnum_is_zero(devnum))
+                return device_path_make_inaccessible(mode, ret);
+
+        r = device_new_from_mode_and_devnum(&dev, mode, devnum);
+        if (r < 0)
+                return r;
+
+        r = sd_device_get_devname(dev, &devname);
+        if (r < 0)
+                return r;
+
+        s = strdup(devname);
+        if (!s)
+                return -ENOMEM;
+
+        *ret = TAKE_PTR(s);
+        return 0;
+}
+
+int device_open_from_devnum(mode_t mode, dev_t devnum, int flags, char **ret) {
+        _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
+        _cleanup_close_ int fd = -EBADF;
+        int r;
+
+        r = device_new_from_mode_and_devnum(&dev, mode, devnum);
+        if (r < 0)
+                return r;
+
+        fd = sd_device_open(dev, flags);
+        if (fd < 0)
+                return fd;
+
+        if (ret) {
+                const char *devname;
+                char *s;
+
+                r = sd_device_get_devname(dev, &devname);
+                if (r < 0)
+                        return r;
+
+                s = strdup(devname);
+                if (!s)
+                        return -ENOMEM;
+
+                *ret = s;
+        }
+
+        return TAKE_FD(fd);
+}
+
+static int add_string_field(
+                sd_device *device,
+                const char *field,
+                int (*func)(sd_device *dev, const char **s),
+                char ***strv) {
+
+        const char *s;
+        int r;
+
+        assert(device);
+        assert(field);
+        assert(func);
+        assert(strv);
+
+        r = func(device, &s);
+        if (r < 0 && r != -ENOENT)
+                log_device_debug_errno(device, r, "Failed to get device \"%s\" property, ignoring: %m", field);
+        if (r >= 0)
+                (void) strv_extend_assignment(strv, field, s);
+
+        return 0;
+}
+
+char** device_make_log_fields(sd_device *device) {
+        _cleanup_strv_free_ char **strv = NULL;
+        dev_t devnum;
+        int ifindex;
+        sd_device_action_t action;
+        uint64_t seqnum, diskseq;
+        int r;
+
+        assert(device);
+
+        (void) add_string_field(device, "SYSPATH", sd_device_get_syspath, &strv);
+        (void) add_string_field(device, "SUBSYSTEM", sd_device_get_subsystem, &strv);
+        (void) add_string_field(device, "DEVTYPE", sd_device_get_devtype, &strv);
+        (void) add_string_field(device, "DRIVER", sd_device_get_driver, &strv);
+        (void) add_string_field(device, "DEVPATH", sd_device_get_devpath, &strv);
+        (void) add_string_field(device, "DEVNAME", sd_device_get_devname, &strv);
+        (void) add_string_field(device, "SYSNAME", sd_device_get_sysname, &strv);
+        (void) add_string_field(device, "SYSNUM", sd_device_get_sysnum, &strv);
+
+        r = sd_device_get_devnum(device, &devnum);
+        if (r < 0 && r != -ENOENT)
+                log_device_debug_errno(device, r, "Failed to get device \"DEVNUM\" property, ignoring: %m");
+        if (r >= 0)
+                (void) strv_extendf(&strv, "DEVNUM="DEVNUM_FORMAT_STR, DEVNUM_FORMAT_VAL(devnum));
+
+        r = sd_device_get_ifindex(device, &ifindex);
+        if (r < 0 && r != -ENOENT)
+                log_device_debug_errno(device, r, "Failed to get device \"IFINDEX\" property, ignoring: %m");
+        if (r >= 0)
+                (void) strv_extendf(&strv, "IFINDEX=%i", ifindex);
+
+        r = sd_device_get_action(device, &action);
+        if (r < 0 && r != -ENOENT)
+                log_device_debug_errno(device, r, "Failed to get device \"ACTION\" property, ignoring: %m");
+        if (r >= 0)
+                (void) strv_extendf(&strv, "ACTION=%s", device_action_to_string(action));
+
+        r = sd_device_get_seqnum(device, &seqnum);
+        if (r < 0 && r != -ENOENT)
+                log_device_debug_errno(device, r, "Failed to get device \"SEQNUM\" property, ignoring: %m");
+        if (r >= 0)
+                (void) strv_extendf(&strv, "SEQNUM=%"PRIu64, seqnum);
+
+        r = sd_device_get_diskseq(device, &diskseq);
+        if (r < 0 && r != -ENOENT)
+                log_device_debug_errno(device, r, "Failed to get device \"DISKSEQ\" property, ignoring: %m");
+        if (r >= 0)
+                (void) strv_extendf(&strv, "DISKSEQ=%"PRIu64, diskseq);
+
+        return TAKE_PTR(strv);
+}
diff --git a/src/libsystemd/sd-device/device-util.h b/src/libsystemd/sd-device/device-util.h
new file mode 100644
index 0000000..bf86ddc
--- /dev/null
+++ b/src/libsystemd/sd-device/device-util.h
@@ -0,0 +1,104 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <stdbool.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "sd-device.h"
+
+#include "alloc-util.h"
+#include "log.h"
+#include "macro.h"
+
+#define device_unref_and_replace(a, b)                                  \
+        unref_and_replace_full(a, b, sd_device_ref, sd_device_unref)
+
+#define FOREACH_DEVICE_PROPERTY(device, key, value)                     \
+        for (const char *value, *key = sd_device_get_property_first(device, &value); \
+             key;                                                       \
+             key = sd_device_get_property_next(device, &value))
+
+#define FOREACH_DEVICE_TAG(device, tag)                                 \
+        for (const char *tag = sd_device_get_tag_first(device);         \
+             tag;                                                       \
+             tag = sd_device_get_tag_next(device))
+
+#define FOREACH_DEVICE_CURRENT_TAG(device, tag)                         \
+        for (const char *tag = sd_device_get_current_tag_first(device); \
+             tag;                                                       \
+             tag = sd_device_get_current_tag_next(device))
+
+#define FOREACH_DEVICE_SYSATTR(device, attr)                            \
+        for (const char *attr = sd_device_get_sysattr_first(device);    \
+             attr;                                                      \
+             attr = sd_device_get_sysattr_next(device))
+
+#define FOREACH_DEVICE_DEVLINK(device, devlink)                         \
+        for (const char *devlink = sd_device_get_devlink_first(device); \
+             devlink;                                                   \
+             devlink = sd_device_get_devlink_next(device))
+
+#define _FOREACH_DEVICE_CHILD(device, child, suffix_ptr)                \
+        for (sd_device *child = sd_device_get_child_first(device, suffix_ptr); \
+             child;                                                     \
+             child = sd_device_get_child_next(device, suffix_ptr))
+
+#define FOREACH_DEVICE_CHILD(device, child)                             \
+        _FOREACH_DEVICE_CHILD(device, child, NULL)
+
+#define FOREACH_DEVICE_CHILD_WITH_SUFFIX(device, child, suffix)         \
+        _FOREACH_DEVICE_CHILD(device, child, &suffix)
+
+#define FOREACH_DEVICE(enumerator, device)                              \
+        for (sd_device *device = sd_device_enumerator_get_device_first(enumerator); \
+             device;                                                    \
+             device = sd_device_enumerator_get_device_next(enumerator))
+
+#define FOREACH_SUBSYSTEM(enumerator, device)                           \
+        for (sd_device *device = sd_device_enumerator_get_subsystem_first(enumerator); \
+             device;                                                    \
+             device = sd_device_enumerator_get_subsystem_next(enumerator))
+
+#define log_device_full_errno_zerook(device, level, error, ...)         \
+        ({                                                              \
+                const char *_sysname = NULL;                            \
+                sd_device *_d = (device);                               \
+                int _level = (level), _e = (error);                     \
+                                                                        \
+                if (_d && _unlikely_(log_get_max_level() >= LOG_PRI(_level))) \
+                        (void) sd_device_get_sysname(_d, &_sysname);    \
+                log_object_internal(_level, _e, PROJECT_FILE, __LINE__, __func__, \
+                                    _sysname ? "DEVICE=" : NULL, _sysname, \
+                                    NULL, NULL, __VA_ARGS__);           \
+        })
+
+#define log_device_full_errno(device, level, error, ...)                \
+        ({                                                              \
+                int _error = (error);                                   \
+                ASSERT_NON_ZERO(_error);                                \
+                log_device_full_errno_zerook(device, level, _error, __VA_ARGS__); \
+        })
+
+#define log_device_full(device, level, ...) (void) log_device_full_errno_zerook(device, level, 0, __VA_ARGS__)
+
+#define log_device_debug(device, ...)   log_device_full(device, LOG_DEBUG,   __VA_ARGS__)
+#define log_device_info(device, ...)    log_device_full(device, LOG_INFO,    __VA_ARGS__)
+#define log_device_notice(device, ...)  log_device_full(device, LOG_NOTICE,  __VA_ARGS__)
+#define log_device_warning(device, ...) log_device_full(device, LOG_WARNING, __VA_ARGS__)
+#define log_device_error(device, ...)   log_device_full(device, LOG_ERR,     __VA_ARGS__)
+
+#define log_device_debug_errno(device, error, ...)   log_device_full_errno(device, LOG_DEBUG,   error, __VA_ARGS__)
+#define log_device_info_errno(device, error, ...)    log_device_full_errno(device, LOG_INFO,    error, __VA_ARGS__)
+#define log_device_notice_errno(device, error, ...)  log_device_full_errno(device, LOG_NOTICE,  error, __VA_ARGS__)
+#define log_device_warning_errno(device, error, ...) log_device_full_errno(device, LOG_WARNING, error, __VA_ARGS__)
+#define log_device_error_errno(device, error, ...)   log_device_full_errno(device, LOG_ERR,     error, __VA_ARGS__)
+
+int devname_from_devnum(mode_t mode, dev_t devnum, char **ret);
+static inline int devname_from_stat_rdev(const struct stat *st, char **ret) {
+        assert(st);
+        return devname_from_devnum(st->st_mode, st->st_rdev, ret);
+}
+int device_open_from_devnum(mode_t mode, dev_t devnum, int flags, char **ret);
+
+char** device_make_log_fields(sd_device *device);
diff --git a/src/libsystemd/sd-device/sd-device.c b/src/libsystemd/sd-device/sd-device.c
new file mode 100644
index 0000000..2fbc619
--- /dev/null
+++ b/src/libsystemd/sd-device/sd-device.c
@@ -0,0 +1,2715 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <ctype.h>
+#include <net/if.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+
+#include "sd-device.h"
+
+#include "alloc-util.h"
+#include "chase.h"
+#include "device-internal.h"
+#include "device-private.h"
+#include "device-util.h"
+#include "devnum-util.h"
+#include "dirent-util.h"
+#include "env-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "format-util.h"
+#include "fs-util.h"
+#include "hashmap.h"
+#include "id128-util.h"
+#include "macro.h"
+#include "missing_magic.h"
+#include "netlink-util.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "set.h"
+#include "socket-util.h"
+#include "stdio-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "strxcpyx.h"
+#include "user-util.h"
+
+int device_new_aux(sd_device **ret) {
+        sd_device *device;
+
+        assert(ret);
+
+        device = new(sd_device, 1);
+        if (!device)
+                return -ENOMEM;
+
+        *device = (sd_device) {
+                .n_ref = 1,
+                .devmode = MODE_INVALID,
+                .devuid = UID_INVALID,
+                .devgid = GID_INVALID,
+                .action = _SD_DEVICE_ACTION_INVALID,
+        };
+
+        *ret = device;
+        return 0;
+}
+
+static sd_device *device_free(sd_device *device) {
+        assert(device);
+
+        sd_device_unref(device->parent);
+        free(device->syspath);
+        free(device->sysname);
+        free(device->devtype);
+        free(device->devname);
+        free(device->subsystem);
+        free(device->driver_subsystem);
+        free(device->driver);
+        free(device->device_id);
+        free(device->properties_strv);
+        free(device->properties_nulstr);
+
+        ordered_hashmap_free(device->properties);
+        ordered_hashmap_free(device->properties_db);
+        hashmap_free(device->sysattr_values);
+        set_free(device->sysattrs);
+        set_free(device->all_tags);
+        set_free(device->current_tags);
+        set_free(device->devlinks);
+        hashmap_free(device->children);
+
+        return mfree(device);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_device, sd_device, device_free);
+
+int device_add_property_aux(sd_device *device, const char *key, const char *value, bool db) {
+        OrderedHashmap **properties;
+
+        assert(device);
+        assert(key);
+
+        if (db)
+                properties = &device->properties_db;
+        else
+                properties = &device->properties;
+
+        if (value) {
+                _unused_ _cleanup_free_ char *old_value = NULL;
+                _cleanup_free_ char *new_key = NULL, *new_value = NULL, *old_key = NULL;
+                int r;
+
+                r = ordered_hashmap_ensure_allocated(properties, &string_hash_ops_free_free);
+                if (r < 0)
+                        return r;
+
+                new_key = strdup(key);
+                if (!new_key)
+                        return -ENOMEM;
+
+                new_value = strdup(value);
+                if (!new_value)
+                        return -ENOMEM;
+
+                old_value = ordered_hashmap_get2(*properties, key, (void**) &old_key);
+
+                /* ordered_hashmap_replace() does not fail when the hashmap already has the entry. */
+                r = ordered_hashmap_replace(*properties, new_key, new_value);
+                if (r < 0)
+                        return r;
+
+                TAKE_PTR(new_key);
+                TAKE_PTR(new_value);
+        } else {
+                _unused_ _cleanup_free_ char *old_value = NULL;
+                _cleanup_free_ char *old_key = NULL;
+
+                old_value = ordered_hashmap_remove2(*properties, key, (void**) &old_key);
+        }
+
+        if (!db) {
+                device->properties_generation++;
+                device->properties_buf_outdated = true;
+        }
+
+        return 0;
+}
+
+int device_set_syspath(sd_device *device, const char *_syspath, bool verify) {
+        _cleanup_free_ char *syspath = NULL;
+        const char *devpath;
+        int r;
+
+        assert(device);
+        assert(_syspath);
+
+        if (verify) {
+                _cleanup_close_ int fd = -EBADF;
+
+                /* The input path maybe a symlink located outside of /sys. Let's try to chase the symlink at first.
+                 * The primary use case is that e.g. /proc/device-tree is a symlink to /sys/firmware/devicetree/base.
+                 * By chasing symlinks in the path at first, we can call sd_device_new_from_path() with such path. */
+                r = chase(_syspath, NULL, 0, &syspath, &fd);
+                if (r == -ENOENT)
+                         /* the device does not exist (any more?) */
+                        return log_debug_errno(SYNTHETIC_ERRNO(ENODEV),
+                                               "sd-device: Failed to chase symlinks in \"%s\".", _syspath);
+                if (r < 0)
+                        return log_debug_errno(r, "sd-device: Failed to get target of '%s': %m", _syspath);
+
+                if (!path_startswith(syspath, "/sys")) {
+                        _cleanup_free_ char *real_sys = NULL, *new_syspath = NULL;
+                        char *p;
+
+                        /* /sys is a symlink to somewhere sysfs is mounted on? In that case, we convert the path to real sysfs to "/sys". */
+                        r = chase("/sys", NULL, 0, &real_sys, NULL);
+                        if (r < 0)
+                                return log_debug_errno(r, "sd-device: Failed to chase symlink /sys: %m");
+
+                        p = path_startswith(syspath, real_sys);
+                        if (!p)
+                                return log_debug_errno(SYNTHETIC_ERRNO(ENODEV),
+                                                       "sd-device: Canonicalized path '%s' does not starts with sysfs mount point '%s'",
+                                                       syspath, real_sys);
+
+                        new_syspath = path_join("/sys", p);
+                        if (!new_syspath)
+                                return log_oom_debug();
+
+                        free_and_replace(syspath, new_syspath);
+                        path_simplify(syspath);
+                }
+
+                if (path_startswith(syspath, "/sys/devices/")) {
+                        /* For proper devices, stricter rules apply: they must have a 'uevent' file,
+                         * otherwise we won't allow them */
+
+                        if (faccessat(fd, "uevent", F_OK, 0) < 0) {
+                                if (errno == ENOENT)
+                                        /* This is not a valid device.  Note, this condition is quite often
+                                         * satisfied when enumerating devices or finding a parent device.
+                                         * Hence, use log_trace_errno() here. */
+                                        return log_trace_errno(SYNTHETIC_ERRNO(ENODEV),
+                                                               "sd-device: the uevent file \"%s/uevent\" does not exist.", syspath);
+                                if (errno == ENOTDIR)
+                                        /* Not actually a directory. */
+                                        return log_debug_errno(SYNTHETIC_ERRNO(ENODEV),
+                                                               "sd-device: the syspath \"%s\" is not a directory.", syspath);
+
+                                return log_debug_errno(errno, "sd-device: cannot find uevent file for %s: %m", syspath);
+                        }
+                } else {
+                        struct stat st;
+
+                        /* For everything else lax rules apply: they just need to be a directory */
+
+                        if (fstat(fd, &st) < 0)
+                                return log_debug_errno(errno, "sd-device: failed to check if syspath \"%s\" is a directory: %m", syspath);
+                        if (!S_ISDIR(st.st_mode))
+                                return log_debug_errno(SYNTHETIC_ERRNO(ENODEV),
+                                                       "sd-device: the syspath \"%s\" is not a directory.", syspath);
+                }
+
+                /* Only operate on sysfs, i.e. refuse going down into /sys/fs/cgroup/ or similar places where
+                 * things are not arranged as kobjects in kernel, and hence don't necessarily have
+                 * kobject/attribute structure. */
+                r = getenv_bool_secure("SYSTEMD_DEVICE_VERIFY_SYSFS");
+                if (r < 0 && r != -ENXIO)
+                        log_debug_errno(r, "Failed to parse $SYSTEMD_DEVICE_VERIFY_SYSFS value: %m");
+                if (r != 0) {
+                        r = fd_is_fs_type(fd, SYSFS_MAGIC);
+                        if (r < 0)
+                                return log_debug_errno(r, "sd-device: failed to check if syspath \"%s\" is backed by sysfs.", syspath);
+                        if (r == 0)
+                                return log_debug_errno(SYNTHETIC_ERRNO(ENODEV),
+                                                       "sd-device: the syspath \"%s\" is outside of sysfs, refusing.", syspath);
+                }
+        } else {
+                /* must be a subdirectory of /sys */
+                if (!path_startswith(_syspath, "/sys/"))
+                        return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "sd-device: Syspath '%s' is not a subdirectory of /sys",
+                                               _syspath);
+
+                r = path_simplify_alloc(_syspath, &syspath);
+                if (r < 0)
+                        return r;
+        }
+
+        assert_se(devpath = startswith(syspath, "/sys"));
+        if (devpath[0] != '/')
+                return log_debug_errno(SYNTHETIC_ERRNO(ENODEV), "sd-device: \"/sys\" alone is not a valid device path.");
+
+        r = device_add_property_internal(device, "DEVPATH", devpath);
+        if (r < 0)
+                return log_debug_errno(r, "sd-device: Failed to add \"DEVPATH\" property for device \"%s\": %m", syspath);
+
+        free_and_replace(device->syspath, syspath);
+        device->devpath = devpath;
+
+        /* Unset sysname and sysnum, they will be assigned when requested. */
+        device->sysnum = NULL;
+        device->sysname = mfree(device->sysname);
+        return 0;
+}
+
+static int device_new_from_syspath(sd_device **ret, const char *syspath, bool strict) {
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+        int r;
+
+        assert_return(ret, -EINVAL);
+        assert_return(syspath, -EINVAL);
+
+        if (strict && !path_startswith(syspath, "/sys/"))
+                return -EINVAL;
+
+        r = device_new_aux(&device);
+        if (r < 0)
+                return r;
+
+        r = device_set_syspath(device, syspath, /* verify= */ true);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(device);
+        return 0;
+}
+
+_public_ int sd_device_new_from_syspath(sd_device **ret, const char *syspath) {
+        return device_new_from_syspath(ret, syspath, /* strict = */ true);
+}
+
+int device_new_from_mode_and_devnum(sd_device **ret, mode_t mode, dev_t devnum) {
+        _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
+        _cleanup_free_ char *syspath = NULL;
+        const char *t, *subsystem = NULL;
+        dev_t n;
+        int r;
+
+        assert(ret);
+
+        if (S_ISCHR(mode))
+                t = "char";
+        else if (S_ISBLK(mode))
+                t = "block";
+        else
+                return -ENOTTY;
+
+        if (major(devnum) == 0)
+                return -ENODEV;
+
+        if (asprintf(&syspath, "/sys/dev/%s/" DEVNUM_FORMAT_STR, t, DEVNUM_FORMAT_VAL(devnum)) < 0)
+                return -ENOMEM;
+
+        r = sd_device_new_from_syspath(&dev, syspath);
+        if (r < 0)
+                return r;
+
+        r = sd_device_get_devnum(dev, &n);
+        if (r == -ENOENT)
+                return -ENXIO;
+        if (r < 0)
+                return r;
+        if (n != devnum)
+                return -ENXIO;
+
+        r = sd_device_get_subsystem(dev, &subsystem);
+        if (r < 0 && r != -ENOENT)
+                return r;
+        if (streq_ptr(subsystem, "block") != !!S_ISBLK(mode))
+                return -ENXIO;
+
+        *ret = TAKE_PTR(dev);
+        return 0;
+}
+
+_public_ int sd_device_new_from_devnum(sd_device **ret, char type, dev_t devnum) {
+        assert_return(ret, -EINVAL);
+        assert_return(IN_SET(type, 'b', 'c'), -EINVAL);
+
+        return device_new_from_mode_and_devnum(ret, type == 'b' ? S_IFBLK : S_IFCHR, devnum);
+}
+
+static int device_new_from_main_ifname(sd_device **ret, const char *ifname) {
+        const char *syspath;
+
+        assert(ret);
+        assert(ifname);
+
+        syspath = strjoina("/sys/class/net/", ifname);
+        return sd_device_new_from_syspath(ret, syspath);
+}
+
+_public_ int sd_device_new_from_ifname(sd_device **ret, const char *ifname) {
+        _cleanup_free_ char *main_name = NULL;
+        int r;
+
+        assert_return(ret, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        r = parse_ifindex(ifname);
+        if (r > 0)
+                return sd_device_new_from_ifindex(ret, r);
+
+        if (ifname_valid(ifname)) {
+                r = device_new_from_main_ifname(ret, ifname);
+                if (r >= 0)
+                        return r;
+        }
+
+        r = rtnl_resolve_link_alternative_name(NULL, ifname, &main_name);
+        if (r < 0)
+                return r;
+
+        return device_new_from_main_ifname(ret, main_name);
+}
+
+_public_ int sd_device_new_from_ifindex(sd_device **ret, int ifindex) {
+        _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
+        char ifname[IF_NAMESIZE];
+        int r, i;
+
+        assert_return(ret, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
+
+        if (format_ifname(ifindex, ifname) < 0)
+                return -ENODEV;
+
+        r = device_new_from_main_ifname(&dev, ifname);
+        if (r < 0)
+                return r;
+
+        r = sd_device_get_ifindex(dev, &i);
+        if (r == -ENOENT)
+                return -ENXIO;
+        if (r < 0)
+                return r;
+        if (i != ifindex)
+                return -ENXIO;
+
+        *ret = TAKE_PTR(dev);
+        return 0;
+}
+
+static int device_strjoin_new(
+                const char *a,
+                const char *b,
+                const char *c,
+                const char *d,
+                sd_device **ret) {
+
+        const char *p;
+        int r;
+
+        p = strjoina(a, b, c, d);
+        if (access(p, F_OK) < 0)
+                return IN_SET(errno, ENOENT, ENAMETOOLONG) ? 0 : -errno; /* If this sysfs is too long then it doesn't exist either */
+
+        r = sd_device_new_from_syspath(ret, p);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+_public_ int sd_device_new_from_subsystem_sysname(
+                sd_device **ret,
+                const char *subsystem,
+                const char *sysname) {
+
+        char *name;
+        int r;
+
+        assert_return(ret, -EINVAL);
+        assert_return(subsystem, -EINVAL);
+        assert_return(sysname, -EINVAL);
+
+        if (!path_is_normalized(subsystem))
+                return -EINVAL;
+        if (!path_is_normalized(sysname))
+                return -EINVAL;
+
+        /* translate sysname back to sysfs filename */
+        name = strdupa_safe(sysname);
+        string_replace_char(name, '/', '!');
+
+        if (streq(subsystem, "subsystem")) {
+                FOREACH_STRING(s, "/sys/bus/", "/sys/class/") {
+                        r = device_strjoin_new(s, name, NULL, NULL, ret);
+                        if (r < 0)
+                                return r;
+                        if (r > 0)
+                                return 0;
+                }
+
+        } else if (streq(subsystem, "module")) {
+                r = device_strjoin_new("/sys/module/", name, NULL, NULL, ret);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        return 0;
+
+        } else if (streq(subsystem, "drivers")) {
+                const char *sep;
+
+                sep = strchr(name, ':');
+                if (sep && sep[1] != '\0') { /* Require ":" and something non-empty after that. */
+
+                        const char *subsys = memdupa_suffix0(name, sep - name);
+                        sep++;
+
+                        if (streq(sep, "drivers")) /* If the sysname is "drivers", then it's the drivers directory itself that is meant. */
+                                r = device_strjoin_new("/sys/bus/", subsys, "/drivers", NULL, ret);
+                        else
+                                r = device_strjoin_new("/sys/bus/", subsys, "/drivers/", sep, ret);
+                        if (r < 0)
+                                return r;
+                        if (r > 0)
+                                return 0;
+                }
+        }
+
+        r = device_strjoin_new("/sys/bus/", subsystem, "/devices/", name, ret);
+        if (r < 0)
+                return r;
+        if (r > 0)
+                return 0;
+
+        r = device_strjoin_new("/sys/class/", subsystem, "/", name, ret);
+        if (r < 0)
+                return r;
+        if (r > 0)
+                return 0;
+
+        r = device_strjoin_new("/sys/firmware/", subsystem, "/", name, ret);
+        if (r < 0)
+                return r;
+        if (r > 0)
+                return 0;
+
+        return -ENODEV;
+}
+
+_public_ int sd_device_new_from_stat_rdev(sd_device **ret, const struct stat *st) {
+        assert_return(ret, -EINVAL);
+        assert_return(st, -EINVAL);
+
+        return device_new_from_mode_and_devnum(ret, st->st_mode, st->st_rdev);
+}
+
+_public_ int sd_device_new_from_devname(sd_device **ret, const char *devname) {
+        struct stat st;
+        dev_t devnum;
+        mode_t mode;
+
+        assert_return(ret, -EINVAL);
+        assert_return(devname, -EINVAL);
+
+        /* This function actually accepts both devlinks and devnames, i.e. both symlinks and device
+         * nodes below /dev/. */
+
+        /* Also ignore when the specified path is "/dev". */
+        if (isempty(path_startswith(devname, "/dev")))
+                return -EINVAL;
+
+        if (device_path_parse_major_minor(devname, &mode, &devnum) >= 0)
+                /* Let's shortcut when "/dev/block/maj:min" or "/dev/char/maj:min" is specified.
+                 * In that case, we can directly convert the path to syspath, hence it is not necessary
+                 * that the specified path exists. So, this works fine without udevd being running. */
+                return device_new_from_mode_and_devnum(ret, mode, devnum);
+
+        if (stat(devname, &st) < 0)
+                return ERRNO_IS_DEVICE_ABSENT(errno) ? -ENODEV : -errno;
+
+        return sd_device_new_from_stat_rdev(ret, &st);
+}
+
+_public_ int sd_device_new_from_path(sd_device **ret, const char *path) {
+        assert_return(ret, -EINVAL);
+        assert_return(path, -EINVAL);
+
+        if (path_startswith(path, "/dev"))
+                return sd_device_new_from_devname(ret, path);
+
+        return device_new_from_syspath(ret, path, /* strict = */ false);
+}
+
+int device_set_devtype(sd_device *device, const char *devtype) {
+        _cleanup_free_ char *t = NULL;
+        int r;
+
+        assert(device);
+        assert(devtype);
+
+        t = strdup(devtype);
+        if (!t)
+                return -ENOMEM;
+
+        r = device_add_property_internal(device, "DEVTYPE", t);
+        if (r < 0)
+                return r;
+
+        return free_and_replace(device->devtype, t);
+}
+
+int device_set_ifindex(sd_device *device, const char *name) {
+        int r, ifindex;
+
+        assert(device);
+        assert(name);
+
+        ifindex = parse_ifindex(name);
+        if (ifindex < 0)
+                return ifindex;
+
+        r = device_add_property_internal(device, "IFINDEX", name);
+        if (r < 0)
+                return r;
+
+        device->ifindex = ifindex;
+
+        return 0;
+}
+
+static int mangle_devname(const char *p, char **ret) {
+        char *q;
+
+        assert(p);
+        assert(ret);
+
+        if (!path_is_safe(p))
+                return -EINVAL;
+
+        /* When the path is absolute, it must start with "/dev/", but ignore "/dev/" itself. */
+        if (path_is_absolute(p)) {
+                if (isempty(path_startswith(p, "/dev/")))
+                        return -EINVAL;
+
+                q = strdup(p);
+        } else
+                q = path_join("/dev/", p);
+        if (!q)
+                return -ENOMEM;
+
+        path_simplify(q);
+
+        *ret = q;
+        return 0;
+}
+
+int device_set_devname(sd_device *device, const char *devname) {
+        _cleanup_free_ char *t = NULL;
+        int r;
+
+        assert(device);
+        assert(devname);
+
+        r = mangle_devname(devname, &t);
+        if (r < 0)
+                return r;
+
+        r = device_add_property_internal(device, "DEVNAME", t);
+        if (r < 0)
+                return r;
+
+        return free_and_replace(device->devname, t);
+}
+
+int device_set_devmode(sd_device *device, const char *_devmode) {
+        unsigned devmode;
+        int r;
+
+        assert(device);
+        assert(_devmode);
+
+        r = safe_atou(_devmode, &devmode);
+        if (r < 0)
+                return r;
+
+        if (devmode > 07777)
+                return -EINVAL;
+
+        r = device_add_property_internal(device, "DEVMODE", _devmode);
+        if (r < 0)
+                return r;
+
+        device->devmode = devmode;
+
+        return 0;
+}
+
+int device_set_devnum(sd_device *device, const char *major, const char *minor) {
+        unsigned maj, min = 0;
+        int r;
+
+        assert(device);
+        assert(major);
+
+        r = safe_atou(major, &maj);
+        if (r < 0)
+                return r;
+        if (maj == 0)
+                return 0;
+        if (!DEVICE_MAJOR_VALID(maj))
+                return -EINVAL;
+
+        if (minor) {
+                r = safe_atou(minor, &min);
+                if (r < 0)
+                        return r;
+                if (!DEVICE_MINOR_VALID(min))
+                        return -EINVAL;
+        }
+
+        r = device_add_property_internal(device, "MAJOR", major);
+        if (r < 0)
+                return r;
+
+        if (minor) {
+                r = device_add_property_internal(device, "MINOR", minor);
+                if (r < 0)
+                        return r;
+        }
+
+        device->devnum = makedev(maj, min);
+
+        return 0;
+}
+
+int device_set_diskseq(sd_device *device, const char *str) {
+        uint64_t diskseq;
+        int r;
+
+        assert(device);
+        assert(str);
+
+        r = safe_atou64(str, &diskseq);
+        if (r < 0)
+                return r;
+        if (diskseq == 0)
+                return -EINVAL;
+
+        r = device_add_property_internal(device, "DISKSEQ", str);
+        if (r < 0)
+                return r;
+
+        device->diskseq = diskseq;
+
+        return 0;
+}
+
+static int handle_uevent_line(
+                sd_device *device,
+                const char *key,
+                const char *value,
+                const char **major,
+                const char **minor) {
+
+        assert(device);
+        assert(key);
+        assert(value);
+        assert(major);
+        assert(minor);
+
+        if (streq(key, "DEVTYPE"))
+                return device_set_devtype(device, value);
+        if (streq(key, "IFINDEX"))
+                return device_set_ifindex(device, value);
+        if (streq(key, "DEVNAME"))
+                return device_set_devname(device, value);
+        if (streq(key, "DEVMODE"))
+                return device_set_devmode(device, value);
+        if (streq(key, "DISKSEQ"))
+                return device_set_diskseq(device, value);
+        if (streq(key, "MAJOR"))
+                *major = value;
+        else if (streq(key, "MINOR"))
+                *minor = value;
+        else
+                return device_add_property_internal(device, key, value);
+
+        return 0;
+}
+
+int device_read_uevent_file(sd_device *device) {
+        _cleanup_free_ char *uevent = NULL;
+        const char *syspath, *key = NULL, *value = NULL, *major = NULL, *minor = NULL;
+        char *path;
+        size_t uevent_len;
+        int r;
+
+        enum {
+                PRE_KEY,
+                KEY,
+                PRE_VALUE,
+                VALUE,
+                INVALID_LINE,
+        } state = PRE_KEY;
+
+        assert(device);
+
+        if (device->uevent_loaded || device->sealed)
+                return 0;
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        device->uevent_loaded = true;
+
+        path = strjoina(syspath, "/uevent");
+
+        r = read_full_virtual_file(path, &uevent, &uevent_len);
+        if (r == -EACCES || ERRNO_IS_NEG_DEVICE_ABSENT(r))
+                /* The uevent files may be write-only, the device may be already removed, or the device
+                 * may not have the uevent file. */
+                return 0;
+        if (r < 0)
+                return log_device_debug_errno(device, r, "sd-device: Failed to read uevent file '%s': %m", path);
+
+        for (size_t i = 0; i < uevent_len; i++)
+                switch (state) {
+                case PRE_KEY:
+                        if (!strchr(NEWLINE, uevent[i])) {
+                                key = &uevent[i];
+
+                                state = KEY;
+                        }
+
+                        break;
+                case KEY:
+                        if (uevent[i] == '=') {
+                                uevent[i] = '\0';
+
+                                state = PRE_VALUE;
+                        } else if (strchr(NEWLINE, uevent[i])) {
+                                uevent[i] = '\0';
+                                log_device_debug(device, "sd-device: Invalid uevent line '%s', ignoring", key);
+
+                                state = PRE_KEY;
+                        }
+
+                        break;
+                case PRE_VALUE:
+                        value = &uevent[i];
+                        state = VALUE;
+
+                        _fallthrough_; /* to handle empty property */
+                case VALUE:
+                        if (strchr(NEWLINE, uevent[i])) {
+                                uevent[i] = '\0';
+
+                                r = handle_uevent_line(device, key, value, &major, &minor);
+                                if (r < 0)
+                                        log_device_debug_errno(device, r, "sd-device: Failed to handle uevent entry '%s=%s', ignoring: %m", key, value);
+
+                                state = PRE_KEY;
+                        }
+
+                        break;
+                default:
+                        assert_not_reached();
+                }
+
+        if (major) {
+                r = device_set_devnum(device, major, minor);
+                if (r < 0)
+                        log_device_debug_errno(device, r, "sd-device: Failed to set 'MAJOR=%s' or 'MINOR=%s' from '%s', ignoring: %m", major, strna(minor), path);
+        }
+
+        return 0;
+}
+
+_public_ int sd_device_get_ifindex(sd_device *device, int *ifindex) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        if (device->ifindex <= 0)
+                return -ENOENT;
+
+        if (ifindex)
+                *ifindex = device->ifindex;
+
+        return 0;
+}
+
+_public_ int sd_device_new_from_device_id(sd_device **ret, const char *id) {
+        int r;
+
+        assert_return(ret, -EINVAL);
+        assert_return(id, -EINVAL);
+
+        switch (id[0]) {
+        case 'b':
+        case 'c': {
+                dev_t devt;
+
+                if (isempty(id))
+                        return -EINVAL;
+
+                r = parse_devnum(id + 1, &devt);
+                if (r < 0)
+                        return r;
+
+                return sd_device_new_from_devnum(ret, id[0], devt);
+        }
+
+        case 'n': {
+                int ifindex;
+
+                ifindex = parse_ifindex(id + 1);
+                if (ifindex < 0)
+                        return ifindex;
+
+                return sd_device_new_from_ifindex(ret, ifindex);
+        }
+
+        case '+': {
+                const char *subsys, *sep;
+
+                sep = strchr(id + 1, ':');
+                if (!sep || sep - id - 1 > NAME_MAX)
+                        return -EINVAL;
+
+                subsys = memdupa_suffix0(id + 1, sep - id - 1);
+
+                return sd_device_new_from_subsystem_sysname(ret, subsys, sep + 1);
+        }
+
+        default:
+                return -EINVAL;
+        }
+}
+
+_public_ int sd_device_get_syspath(sd_device *device, const char **ret) {
+        assert_return(device, -EINVAL);
+
+        assert(path_startswith(device->syspath, "/sys/"));
+
+        if (ret)
+                *ret = device->syspath;
+
+        return 0;
+}
+
+DEFINE_PRIVATE_HASH_OPS_FULL(
+        device_by_path_hash_ops,
+        char, path_hash_func, path_compare, free,
+        sd_device, sd_device_unref);
+
+static int device_enumerate_children_internal(sd_device *device, const char *subdir, Set **stack, Hashmap **children) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        int r;
+
+        assert(device);
+        assert(stack);
+        assert(children);
+
+        r = device_opendir(device, subdir, &dir);
+        if (r < 0)
+                return r;
+
+        FOREACH_DIRENT_ALL(de, dir, return -errno) {
+                _cleanup_(sd_device_unrefp) sd_device *child = NULL;
+                _cleanup_free_ char *p = NULL;
+
+                if (dot_or_dot_dot(de->d_name))
+                        continue;
+
+                if (!IN_SET(de->d_type, DT_LNK, DT_DIR))
+                        continue;
+
+                if (subdir)
+                        p = path_join(subdir, de->d_name);
+                else
+                        p = strdup(de->d_name);
+                if (!p)
+                        return -ENOMEM;
+
+                /* Try to create child device. */
+                r = sd_device_new_child(&child, device, p);
+                if (r >= 0) {
+                        /* OK, this is a child device, saving it. */
+                        r = hashmap_ensure_put(children, &device_by_path_hash_ops, p, child);
+                        if (r < 0)
+                                return r;
+
+                        TAKE_PTR(p);
+                        TAKE_PTR(child);
+                } else if (r == -ENODEV) {
+                        /* This is not a child device. Push the sub-directory into stack, and read it later. */
+
+                        if (de->d_type == DT_LNK)
+                                /* Do not follow symlinks, otherwise, we will enter an infinite loop, e.g.,
+                                 * /sys/class/block/nvme0n1/subsystem/nvme0n1/subsystem/nvme0n1/subsystem/… */
+                                continue;
+
+                        r = set_ensure_consume(stack, &path_hash_ops_free, TAKE_PTR(p));
+                        if (r < 0)
+                                return r;
+                } else
+                        return r;
+        }
+
+        return 0;
+}
+
+static int device_enumerate_children(sd_device *device) {
+        _cleanup_hashmap_free_ Hashmap *children = NULL;
+        _cleanup_set_free_ Set *stack = NULL;
+        int r;
+
+        assert(device);
+
+        if (device->children_enumerated)
+                return 0; /* Already enumerated. */
+
+        r = device_enumerate_children_internal(device, NULL, &stack, &children);
+        if (r < 0)
+                return r;
+
+        for (;;) {
+                _cleanup_free_ char *subdir = NULL;
+
+                subdir = set_steal_first(stack);
+                if (!subdir)
+                        break;
+
+                r = device_enumerate_children_internal(device, subdir, &stack, &children);
+                if (r < 0)
+                        return r;
+        }
+
+        device->children_enumerated = true;
+        device->children = TAKE_PTR(children);
+        return 1; /* Enumerated. */
+}
+
+_public_ sd_device *sd_device_get_child_first(sd_device *device, const char **ret_suffix) {
+        int r;
+
+        assert(device);
+
+        r = device_enumerate_children(device);
+        if (r < 0) {
+                log_device_debug_errno(device, r, "sd-device: failed to enumerate child devices: %m");
+                if (ret_suffix)
+                        *ret_suffix = NULL;
+                return NULL;
+        }
+
+        device->children_iterator = ITERATOR_FIRST;
+
+        return sd_device_get_child_next(device, ret_suffix);
+}
+
+_public_ sd_device *sd_device_get_child_next(sd_device *device, const char **ret_suffix) {
+        sd_device *child;
+
+        assert(device);
+
+        (void) hashmap_iterate(device->children, &device->children_iterator, (void**) &child, (const void**) ret_suffix);
+        return child;
+}
+
+_public_ int sd_device_new_child(sd_device **ret, sd_device *device, const char *suffix) {
+        _cleanup_free_ char *path = NULL;
+        sd_device *child;
+        const char *s;
+        int r;
+
+        assert_return(ret, -EINVAL);
+        assert_return(device, -EINVAL);
+        assert_return(suffix, -EINVAL);
+
+        if (!path_is_safe(suffix))
+                return -EINVAL;
+
+        /* If we have already enumerated children, try to find the child from the cache. */
+        child = hashmap_get(device->children, suffix);
+        if (child) {
+                *ret = sd_device_ref(child);
+                return 0;
+        }
+
+        r = sd_device_get_syspath(device, &s);
+        if (r < 0)
+                return r;
+
+        path = path_join(s, suffix);
+        if (!path)
+                return -ENOMEM;
+
+        return sd_device_new_from_syspath(ret, path);
+}
+
+static int device_new_from_child(sd_device **ret, sd_device *child) {
+        _cleanup_free_ char *path = NULL;
+        const char *syspath;
+        int r;
+
+        assert(ret);
+        assert(child);
+
+        r = sd_device_get_syspath(child, &syspath);
+        if (r < 0)
+                return r;
+
+        for (;;) {
+                _cleanup_free_ char *p = NULL;
+
+                r = path_extract_directory(path ?: syspath, &p);
+                if (r < 0)
+                        return r;
+
+                if (path_equal(p, "/sys"))
+                        return -ENODEV;
+
+                r = sd_device_new_from_syspath(ret, p);
+                if (r != -ENODEV)
+                        return r;
+
+                free_and_replace(path, p);
+        }
+}
+
+_public_ int sd_device_get_parent(sd_device *child, sd_device **ret) {
+        int r;
+
+        assert_return(child, -EINVAL);
+
+        if (!child->parent_set) {
+                r = device_new_from_child(&child->parent, child);
+                if (r < 0 && r != -ENODEV)
+                        return r;
+
+                child->parent_set = true;
+        }
+
+        if (!child->parent)
+                return -ENOENT;
+
+        if (ret)
+                *ret = child->parent;
+        return 0;
+}
+
+int device_set_subsystem(sd_device *device, const char *subsystem) {
+        _cleanup_free_ char *s = NULL;
+        int r;
+
+        assert(device);
+
+        if (subsystem) {
+                s = strdup(subsystem);
+                if (!s)
+                        return -ENOMEM;
+        }
+
+        r = device_add_property_internal(device, "SUBSYSTEM", s);
+        if (r < 0)
+                return r;
+
+        device->subsystem_set = true;
+        return free_and_replace(device->subsystem, s);
+}
+
+int device_set_drivers_subsystem(sd_device *device) {
+        _cleanup_free_ char *subsystem = NULL;
+        const char *devpath, *drivers, *p;
+        int r;
+
+        assert(device);
+
+        r = sd_device_get_devpath(device, &devpath);
+        if (r < 0)
+                return r;
+
+        drivers = strstr(devpath, "/drivers/");
+        if (!drivers)
+                drivers = endswith(devpath, "/drivers");
+        if (!drivers)
+                return -EINVAL;
+
+        /* Find the path component immediately before the "/drivers/" string */
+        r = path_find_last_component(devpath, /* accept_dot_dot= */ false, &drivers, &p);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -EINVAL;
+
+        subsystem = strndup(p, r);
+        if (!subsystem)
+                return -ENOMEM;
+
+        r = device_set_subsystem(device, "drivers");
+        if (r < 0)
+                return r;
+
+        return free_and_replace(device->driver_subsystem, subsystem);
+}
+
+_public_ int sd_device_get_subsystem(sd_device *device, const char **ret) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        if (!device->subsystem_set) {
+                _cleanup_free_ char *subsystem = NULL;
+                const char *syspath;
+                char *path;
+
+                r = sd_device_get_syspath(device, &syspath);
+                if (r < 0)
+                        return r;
+
+                /* read 'subsystem' link */
+                path = strjoina(syspath, "/subsystem");
+                r = readlink_value(path, &subsystem);
+                if (r < 0 && r != -ENOENT)
+                        return log_device_debug_errno(device, r,
+                                                      "sd-device: Failed to read subsystem for %s: %m",
+                                                      device->devpath);
+
+                if (subsystem)
+                        r = device_set_subsystem(device, subsystem);
+                /* use implicit names */
+                else if (!isempty(path_startswith(device->devpath, "/module/")))
+                        r = device_set_subsystem(device, "module");
+                else if (strstr(syspath, "/drivers/") || endswith(syspath, "/drivers"))
+                        r = device_set_drivers_subsystem(device);
+                else if (!isempty(PATH_STARTSWITH_SET(device->devpath, "/class/", "/bus/")))
+                        r = device_set_subsystem(device, "subsystem");
+                else {
+                        device->subsystem_set = true;
+                        r = 0;
+                }
+                if (r < 0)
+                        return log_device_debug_errno(device, r,
+                                                      "sd-device: Failed to set subsystem for %s: %m",
+                                                      device->devpath);
+        }
+
+        if (!device->subsystem)
+                return -ENOENT;
+
+        if (ret)
+                *ret = device->subsystem;
+        return 0;
+}
+
+_public_ int sd_device_get_devtype(sd_device *device, const char **devtype) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        if (!device->devtype)
+                return -ENOENT;
+
+        if (devtype)
+                *devtype = device->devtype;
+
+        return !!device->devtype;
+}
+
+_public_ int sd_device_get_parent_with_subsystem_devtype(sd_device *child, const char *subsystem, const char *devtype, sd_device **ret) {
+        sd_device *parent = NULL;
+        int r;
+
+        assert_return(child, -EINVAL);
+        assert_return(subsystem, -EINVAL);
+
+        r = sd_device_get_parent(child, &parent);
+        while (r >= 0) {
+                const char *parent_subsystem = NULL;
+
+                (void) sd_device_get_subsystem(parent, &parent_subsystem);
+                if (streq_ptr(parent_subsystem, subsystem)) {
+                        const char *parent_devtype = NULL;
+
+                        if (!devtype)
+                                break;
+
+                        (void) sd_device_get_devtype(parent, &parent_devtype);
+                        if (streq_ptr(parent_devtype, devtype))
+                                break;
+                }
+                r = sd_device_get_parent(parent, &parent);
+        }
+
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = parent;
+        return 0;
+}
+
+_public_ int sd_device_get_devnum(sd_device *device, dev_t *devnum) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        if (major(device->devnum) <= 0)
+                return -ENOENT;
+
+        if (devnum)
+                *devnum = device->devnum;
+
+        return 0;
+}
+
+int device_set_driver(sd_device *device, const char *driver) {
+        _cleanup_free_ char *d = NULL;
+        int r;
+
+        assert(device);
+
+        if (driver) {
+                d = strdup(driver);
+                if (!d)
+                        return -ENOMEM;
+        }
+
+        r = device_add_property_internal(device, "DRIVER", d);
+        if (r < 0)
+                return r;
+
+        device->driver_set = true;
+        return free_and_replace(device->driver, d);
+}
+
+_public_ int sd_device_get_driver(sd_device *device, const char **ret) {
+        assert_return(device, -EINVAL);
+
+        if (!device->driver_set) {
+                _cleanup_free_ char *driver = NULL;
+                const char *syspath;
+                char *path;
+                int r;
+
+                r = sd_device_get_syspath(device, &syspath);
+                if (r < 0)
+                        return r;
+
+                path = strjoina(syspath, "/driver");
+                r = readlink_value(path, &driver);
+                if (r < 0 && r != -ENOENT)
+                        return log_device_debug_errno(device, r,
+                                                      "sd-device: readlink(\"%s\") failed: %m", path);
+
+                r = device_set_driver(device, driver);
+                if (r < 0)
+                        return log_device_debug_errno(device, r,
+                                                      "sd-device: Failed to set driver \"%s\": %m", driver);
+        }
+
+        if (!device->driver)
+                return -ENOENT;
+
+        if (ret)
+                *ret = device->driver;
+        return 0;
+}
+
+_public_ int sd_device_get_devpath(sd_device *device, const char **ret) {
+        assert_return(device, -EINVAL);
+
+        assert(device->devpath);
+        assert(device->devpath[0] == '/');
+
+        if (ret)
+                *ret = device->devpath;
+
+        return 0;
+}
+
+_public_ int sd_device_get_devname(sd_device *device, const char **devname) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        if (!device->devname)
+                return -ENOENT;
+
+        assert(!isempty(path_startswith(device->devname, "/dev/")));
+
+        if (devname)
+                *devname = device->devname;
+        return 0;
+}
+
+static int device_set_sysname_and_sysnum(sd_device *device) {
+        _cleanup_free_ char *sysname = NULL;
+        size_t len, n;
+        int r;
+
+        assert(device);
+
+        r = path_extract_filename(device->devpath, &sysname);
+        if (r < 0)
+                return r;
+        if (r == O_DIRECTORY)
+                return -EINVAL;
+
+        /* some devices have '!' in their name, change that to '/' */
+        string_replace_char(sysname, '!', '/');
+
+        n = strspn_from_end(sysname, DIGITS);
+        len = strlen(sysname);
+        assert(n <= len);
+        if (n == len)
+                n = 0; /* Do not set sysnum for number only sysname. */
+
+        device->sysnum = n > 0 ? sysname + len - n : NULL;
+        return free_and_replace(device->sysname, sysname);
+}
+
+_public_ int sd_device_get_sysname(sd_device *device, const char **ret) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        if (!device->sysname) {
+                r = device_set_sysname_and_sysnum(device);
+                if (r < 0)
+                        return r;
+        }
+
+        if (ret)
+                *ret = device->sysname;
+        return 0;
+}
+
+_public_ int sd_device_get_sysnum(sd_device *device, const char **ret) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        if (!device->sysname) {
+                r = device_set_sysname_and_sysnum(device);
+                if (r < 0)
+                        return r;
+        }
+
+        if (!device->sysnum)
+                return -ENOENT;
+
+        if (ret)
+                *ret = device->sysnum;
+        return 0;
+}
+
+_public_ int sd_device_get_action(sd_device *device, sd_device_action_t *ret) {
+        assert_return(device, -EINVAL);
+
+        if (device->action < 0)
+                return -ENOENT;
+
+        if (ret)
+                *ret = device->action;
+
+        return 0;
+}
+
+_public_ int sd_device_get_seqnum(sd_device *device, uint64_t *ret) {
+        assert_return(device, -EINVAL);
+
+        if (device->seqnum == 0)
+                return -ENOENT;
+
+        if (ret)
+                *ret = device->seqnum;
+
+        return 0;
+}
+
+_public_ int sd_device_get_diskseq(sd_device *device, uint64_t *ret) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        if (device->diskseq == 0)
+                return -ENOENT;
+
+        if (ret)
+                *ret = device->diskseq;
+
+        return 0;
+}
+
+static bool is_valid_tag(const char *tag) {
+        assert(tag);
+
+        return in_charset(tag, ALPHANUMERICAL "-_") && filename_is_valid(tag);
+}
+
+int device_add_tag(sd_device *device, const char *tag, bool both) {
+        int r, added;
+
+        assert(device);
+        assert(tag);
+
+        if (!is_valid_tag(tag))
+                return -EINVAL;
+
+        /* Definitely add to the "all" list of tags (i.e. the sticky list) */
+        added = set_put_strdup(&device->all_tags, tag);
+        if (added < 0)
+                return added;
+
+        /* And optionally, also add it to the current list of tags */
+        if (both) {
+                r = set_put_strdup(&device->current_tags, tag);
+                if (r < 0) {
+                        if (added > 0)
+                                (void) set_remove(device->all_tags, tag);
+
+                        return r;
+                }
+        }
+
+        device->tags_generation++;
+        device->property_tags_outdated = true;
+
+        return 0;
+}
+
+int device_add_devlink(sd_device *device, const char *devlink) {
+        char *p;
+        int r;
+
+        assert(device);
+        assert(devlink);
+
+        r = mangle_devname(devlink, &p);
+        if (r < 0)
+                return r;
+
+        r = set_ensure_consume(&device->devlinks, &path_hash_ops_free, p);
+        if (r < 0)
+                return r;
+
+        device->devlinks_generation++;
+        device->property_devlinks_outdated = true;
+
+        return r; /* return 1 when newly added, 0 when already exists */
+}
+
+int device_remove_devlink(sd_device *device, const char *devlink) {
+        _cleanup_free_ char *p = NULL, *s = NULL;
+        int r;
+
+        assert(device);
+        assert(devlink);
+
+        r = mangle_devname(devlink, &p);
+        if (r < 0)
+                return r;
+
+        s = set_remove(device->devlinks, p);
+        if (!s)
+                return 0; /* does not exist */
+
+        device->devlinks_generation++;
+        device->property_devlinks_outdated = true;
+        return 1; /* removed */
+}
+
+bool device_has_devlink(sd_device *device, const char *devlink) {
+        assert(device);
+        assert(devlink);
+
+        return set_contains(device->devlinks, devlink);
+}
+
+static int device_add_property_internal_from_string(sd_device *device, const char *str) {
+        _cleanup_free_ char *key = NULL;
+        char *value;
+        int r;
+
+        assert(device);
+        assert(str);
+
+        key = strdup(str);
+        if (!key)
+                return -ENOMEM;
+
+        value = strchr(key, '=');
+        if (!value)
+                return -EINVAL;
+
+        *value = '\0';
+
+        if (isempty(++value))
+                value = NULL;
+
+        /* Add the property to both sd_device::properties and sd_device::properties_db,
+         * as this is called by only handle_db_line(). */
+        r = device_add_property_aux(device, key, value, false);
+        if (r < 0)
+                return r;
+
+        return device_add_property_aux(device, key, value, true);
+}
+
+int device_set_usec_initialized(sd_device *device, usec_t when) {
+        char s[DECIMAL_STR_MAX(usec_t)];
+        int r;
+
+        assert(device);
+
+        xsprintf(s, USEC_FMT, when);
+
+        r = device_add_property_internal(device, "USEC_INITIALIZED", s);
+        if (r < 0)
+                return r;
+
+        device->usec_initialized = when;
+        return 0;
+}
+
+static int handle_db_line(sd_device *device, char key, const char *value) {
+        int r;
+
+        assert(device);
+        assert(value);
+
+        switch (key) {
+        case 'G': /* Any tag */
+        case 'Q': /* Current tag */
+                return device_add_tag(device, value, key == 'Q');
+
+        case 'S': {
+                const char *path;
+
+                path = strjoina("/dev/", value);
+                return device_add_devlink(device, path);
+        }
+        case 'E':
+                return device_add_property_internal_from_string(device, value);
+
+        case 'I': {
+                usec_t t;
+
+                r = safe_atou64(value, &t);
+                if (r < 0)
+                        return r;
+
+                return device_set_usec_initialized(device, t);
+        }
+        case 'L':
+                return safe_atoi(value, &device->devlink_priority);
+
+        case 'W':
+                /* Deprecated. Previously, watch handle is both saved in database and /run/udev/watch.
+                 * However, the handle saved in database may not be updated when the handle is updated
+                 * or removed. Moreover, it is not necessary to store the handle within the database,
+                 * as its value becomes meaningless when udevd is restarted. */
+                return 0;
+
+        case 'V':
+                return safe_atou(value, &device->database_version);
+
+        default:
+                log_device_debug(device, "sd-device: Unknown key '%c' in device db, ignoring", key);
+                return 0;
+        }
+}
+
+int device_get_device_id(sd_device *device, const char **ret) {
+        assert(device);
+        assert(ret);
+
+        if (!device->device_id) {
+                _cleanup_free_ char *id = NULL;
+                const char *subsystem;
+                dev_t devnum;
+                int ifindex, r;
+
+                r = sd_device_get_subsystem(device, &subsystem);
+                if (r < 0)
+                        return r;
+
+                if (sd_device_get_devnum(device, &devnum) >= 0) {
+                        /* use dev_t — b259:131072, c254:0 */
+                        if (asprintf(&id, "%c" DEVNUM_FORMAT_STR,
+                                     streq(subsystem, "block") ? 'b' : 'c',
+                                     DEVNUM_FORMAT_VAL(devnum)) < 0)
+                                return -ENOMEM;
+                } else if (sd_device_get_ifindex(device, &ifindex) >= 0) {
+                        /* use netdev ifindex — n3 */
+                        if (asprintf(&id, "n%u", (unsigned) ifindex) < 0)
+                                return -ENOMEM;
+                } else {
+                        _cleanup_free_ char *sysname = NULL;
+
+                        /* use $subsys:$sysname — pci:0000:00:1f.2
+                         * sd_device_get_sysname() has '!' translated, get it from devpath */
+                        r = path_extract_filename(device->devpath, &sysname);
+                        if (r < 0)
+                                return r;
+                        if (r == O_DIRECTORY)
+                                return -EINVAL;
+
+                        if (streq(subsystem, "drivers")) {
+                                /* the 'drivers' pseudo-subsystem is special, and needs the real
+                                 * subsystem encoded as well */
+                                assert(device->driver_subsystem);
+                                id = strjoin("+drivers:", device->driver_subsystem, ":", sysname);
+                        } else
+                                id = strjoin("+", subsystem, ":", sysname);
+                        if (!id)
+                                return -ENOMEM;
+                }
+
+                if (!filename_is_valid(id))
+                        return -EINVAL;
+
+                device->device_id = TAKE_PTR(id);
+        }
+
+        *ret = device->device_id;
+        return 0;
+}
+
+int device_read_db_internal_filename(sd_device *device, const char *filename) {
+        _cleanup_free_ char *db = NULL;
+        const char *value;
+        size_t db_len;
+        char key = '\0';  /* Unnecessary initialization to appease gcc-12.0.0-0.4.fc36 */
+        int r;
+
+        enum {
+                PRE_KEY,
+                KEY,
+                PRE_VALUE,
+                VALUE,
+                INVALID_LINE,
+        } state = PRE_KEY;
+
+        assert(device);
+        assert(filename);
+
+        r = read_full_file(filename, &db, &db_len);
+        if (r < 0) {
+                if (r == -ENOENT)
+                        return 0;
+
+                return log_device_debug_errno(device, r, "sd-device: Failed to read db '%s': %m", filename);
+        }
+
+        /* devices with a database entry are initialized */
+        device->is_initialized = true;
+
+        device->db_loaded = true;
+
+        for (size_t i = 0; i < db_len; i++)
+                switch (state) {
+                case PRE_KEY:
+                        if (!strchr(NEWLINE, db[i])) {
+                                key = db[i];
+
+                                state = KEY;
+                        }
+
+                        break;
+                case KEY:
+                        if (db[i] != ':') {
+                                log_device_debug(device, "sd-device: Invalid db entry with key '%c', ignoring", key);
+
+                                state = INVALID_LINE;
+                        } else {
+                                db[i] = '\0';
+
+                                state = PRE_VALUE;
+                        }
+
+                        break;
+                case PRE_VALUE:
+                        value = &db[i];
+
+                        state = VALUE;
+
+                        break;
+                case INVALID_LINE:
+                        if (strchr(NEWLINE, db[i]))
+                                state = PRE_KEY;
+
+                        break;
+                case VALUE:
+                        if (strchr(NEWLINE, db[i])) {
+                                db[i] = '\0';
+                                r = handle_db_line(device, key, value);
+                                if (r < 0)
+                                        log_device_debug_errno(device, r, "sd-device: Failed to handle db entry '%c:%s', ignoring: %m",
+                                                               key, value);
+
+                                state = PRE_KEY;
+                        }
+
+                        break;
+                default:
+                        return log_device_debug_errno(device, SYNTHETIC_ERRNO(EINVAL), "sd-device: invalid db syntax.");
+                }
+
+        return 0;
+}
+
+int device_read_db_internal(sd_device *device, bool force) {
+        const char *id, *path;
+        int r;
+
+        assert(device);
+
+        if (device->db_loaded || (!force && device->sealed))
+                return 0;
+
+        r = device_get_device_id(device, &id);
+        if (r < 0)
+                return r;
+
+        path = strjoina("/run/udev/data/", id);
+
+        return device_read_db_internal_filename(device, path);
+}
+
+_public_ int sd_device_get_is_initialized(sd_device *device) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = device_read_db(device);
+        if (r == -ENOENT)
+                /* The device may be already removed or renamed. */
+                return false;
+        if (r < 0)
+                return r;
+
+        return device->is_initialized;
+}
+
+_public_ int sd_device_get_usec_initialized(sd_device *device, uint64_t *ret) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = sd_device_get_is_initialized(device);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -EBUSY;
+
+        if (device->usec_initialized == 0)
+                return -ENODATA;
+
+        if (ret)
+                *ret = device->usec_initialized;
+
+        return 0;
+}
+
+_public_ int sd_device_get_usec_since_initialized(sd_device *device, uint64_t *ret) {
+        usec_t now_ts, ts;
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = sd_device_get_usec_initialized(device, &ts);
+        if (r < 0)
+                return r;
+
+        now_ts = now(CLOCK_MONOTONIC);
+
+        if (now_ts < ts)
+                return -EIO;
+
+        if (ret)
+                *ret = usec_sub_unsigned(now_ts, ts);
+
+        return 0;
+}
+
+_public_ const char *sd_device_get_tag_first(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        (void) device_read_db(device);
+
+        device->all_tags_iterator_generation = device->tags_generation;
+        device->all_tags_iterator = ITERATOR_FIRST;
+
+        (void) set_iterate(device->all_tags, &device->all_tags_iterator, &v);
+        return v;
+}
+
+_public_ const char *sd_device_get_tag_next(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        (void) device_read_db(device);
+
+        if (device->all_tags_iterator_generation != device->tags_generation)
+                return NULL;
+
+        (void) set_iterate(device->all_tags, &device->all_tags_iterator, &v);
+        return v;
+}
+
+static bool device_database_supports_current_tags(sd_device *device) {
+        assert(device);
+
+        (void) device_read_db(device);
+
+        /* The current tags (saved in Q field) feature is implemented in database version 1.
+         * If the database version is 0, then the tags (NOT current tags, saved in G field) are not
+         * sticky. Thus, we can safely bypass the operations for the current tags (Q) to tags (G). */
+
+        return device->database_version >= 1;
+}
+
+_public_ const char *sd_device_get_current_tag_first(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        if (!device_database_supports_current_tags(device))
+                return sd_device_get_tag_first(device);
+
+        (void) device_read_db(device);
+
+        device->current_tags_iterator_generation = device->tags_generation;
+        device->current_tags_iterator = ITERATOR_FIRST;
+
+        (void) set_iterate(device->current_tags, &device->current_tags_iterator, &v);
+        return v;
+}
+
+_public_ const char *sd_device_get_current_tag_next(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        if (!device_database_supports_current_tags(device))
+                return sd_device_get_tag_next(device);
+
+        (void) device_read_db(device);
+
+        if (device->current_tags_iterator_generation != device->tags_generation)
+                return NULL;
+
+        (void) set_iterate(device->current_tags, &device->current_tags_iterator, &v);
+        return v;
+}
+
+_public_ const char *sd_device_get_devlink_first(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        (void) device_read_db(device);
+
+        device->devlinks_iterator_generation = device->devlinks_generation;
+        device->devlinks_iterator = ITERATOR_FIRST;
+
+        (void) set_iterate(device->devlinks, &device->devlinks_iterator, &v);
+        return v;
+}
+
+_public_ const char *sd_device_get_devlink_next(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        (void) device_read_db(device);
+
+        if (device->devlinks_iterator_generation != device->devlinks_generation)
+                return NULL;
+
+        (void) set_iterate(device->devlinks, &device->devlinks_iterator, &v);
+        return v;
+}
+
+int device_properties_prepare(sd_device *device) {
+        int r;
+
+        assert(device);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        r = device_read_db(device);
+        if (r < 0)
+                return r;
+
+        if (device->property_devlinks_outdated) {
+                _cleanup_free_ char *devlinks = NULL;
+
+                r = set_strjoin(device->devlinks, " ", false, &devlinks);
+                if (r < 0)
+                        return r;
+
+                if (!isempty(devlinks)) {
+                        r = device_add_property_internal(device, "DEVLINKS", devlinks);
+                        if (r < 0)
+                                return r;
+                }
+
+                device->property_devlinks_outdated = false;
+        }
+
+        if (device->property_tags_outdated) {
+                _cleanup_free_ char *tags = NULL;
+
+                r = set_strjoin(device->all_tags, ":", true, &tags);
+                if (r < 0)
+                        return r;
+
+                if (!isempty(tags)) {
+                        r = device_add_property_internal(device, "TAGS", tags);
+                        if (r < 0)
+                                return r;
+                }
+
+                tags = mfree(tags);
+                r = set_strjoin(device->current_tags, ":", true, &tags);
+                if (r < 0)
+                        return r;
+
+                if (!isempty(tags)) {
+                        r = device_add_property_internal(device, "CURRENT_TAGS", tags);
+                        if (r < 0)
+                                return r;
+                }
+
+                device->property_tags_outdated = false;
+        }
+
+        return 0;
+}
+
+_public_ const char *sd_device_get_property_first(sd_device *device, const char **_value) {
+        const char *key;
+        int r;
+
+        assert_return(device, NULL);
+
+        r = device_properties_prepare(device);
+        if (r < 0)
+                return NULL;
+
+        device->properties_iterator_generation = device->properties_generation;
+        device->properties_iterator = ITERATOR_FIRST;
+
+        (void) ordered_hashmap_iterate(device->properties, &device->properties_iterator, (void**)_value, (const void**)&key);
+        return key;
+}
+
+_public_ const char *sd_device_get_property_next(sd_device *device, const char **_value) {
+        const char *key;
+        int r;
+
+        assert_return(device, NULL);
+
+        r = device_properties_prepare(device);
+        if (r < 0)
+                return NULL;
+
+        if (device->properties_iterator_generation != device->properties_generation)
+                return NULL;
+
+        (void) ordered_hashmap_iterate(device->properties, &device->properties_iterator, (void**)_value, (const void**)&key);
+        return key;
+}
+
+static int device_sysattrs_read_all_internal(sd_device *device, const char *subdir, Set **stack) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        int r;
+
+        assert(device);
+        assert(stack);
+
+        r = device_opendir(device, subdir, &dir);
+        if (r == -ENOENT && subdir)
+                return 0; /* Maybe, this is a child device, and is already removed. */
+        if (r < 0)
+                return r;
+
+        if (subdir) {
+                if (faccessat(dirfd(dir), "uevent", F_OK, 0) >= 0)
+                        return 0; /* this is a child device, skipping */
+                if (errno != ENOENT) {
+                        log_device_debug_errno(device, errno,
+                                               "sd-device: Failed to access %s/uevent, ignoring sub-directory %s: %m",
+                                               subdir, subdir);
+                        return 0;
+                }
+        }
+
+        FOREACH_DIRENT_ALL(de, dir, return -errno) {
+                _cleanup_free_ char *p = NULL;
+                struct stat statbuf;
+
+                if (dot_or_dot_dot(de->d_name))
+                        continue;
+
+                /* only handle symlinks, regular files, and directories */
+                if (!IN_SET(de->d_type, DT_LNK, DT_REG, DT_DIR))
+                        continue;
+
+                if (subdir) {
+                        p = path_join(subdir, de->d_name);
+                        if (!p)
+                                return -ENOMEM;
+                }
+
+                if (de->d_type == DT_DIR) {
+                        /* push the sub-directory into the stack, and read it later. */
+                        if (p)
+                                r = set_ensure_consume(stack, &path_hash_ops_free, TAKE_PTR(p));
+                        else
+                                r = set_put_strdup_full(stack, &path_hash_ops_free, de->d_name);
+                        if (r < 0)
+                                return r;
+
+                        continue;
+                }
+
+                if (fstatat(dirfd(dir), de->d_name, &statbuf, AT_SYMLINK_NOFOLLOW) < 0)
+                        continue;
+
+                if ((statbuf.st_mode & (S_IRUSR | S_IWUSR)) == 0)
+                        continue;
+
+                if (p)
+                        r = set_ensure_consume(&device->sysattrs, &path_hash_ops_free, TAKE_PTR(p));
+                else
+                        r = set_put_strdup_full(&device->sysattrs, &path_hash_ops_free, de->d_name);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static int device_sysattrs_read_all(sd_device *device) {
+        _cleanup_set_free_ Set *stack = NULL;
+        int r;
+
+        assert(device);
+
+        if (device->sysattrs_read)
+                return 0;
+
+        r = device_sysattrs_read_all_internal(device, NULL, &stack);
+        if (r < 0)
+                return r;
+
+        for (;;) {
+                _cleanup_free_ char *subdir = NULL;
+
+                subdir = set_steal_first(stack);
+                if (!subdir)
+                        break;
+
+                r = device_sysattrs_read_all_internal(device, subdir, &stack);
+                if (r < 0)
+                        return r;
+        }
+
+        device->sysattrs_read = true;
+
+        return 0;
+}
+
+_public_ const char *sd_device_get_sysattr_first(sd_device *device) {
+        void *v;
+        int r;
+
+        assert_return(device, NULL);
+
+        if (!device->sysattrs_read) {
+                r = device_sysattrs_read_all(device);
+                if (r < 0) {
+                        errno = -r;
+                        return NULL;
+                }
+        }
+
+        device->sysattrs_iterator = ITERATOR_FIRST;
+
+        (void) set_iterate(device->sysattrs, &device->sysattrs_iterator, &v);
+        return v;
+}
+
+_public_ const char *sd_device_get_sysattr_next(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        if (!device->sysattrs_read)
+                return NULL;
+
+        (void) set_iterate(device->sysattrs, &device->sysattrs_iterator, &v);
+        return v;
+}
+
+_public_ int sd_device_has_tag(sd_device *device, const char *tag) {
+        assert_return(device, -EINVAL);
+        assert_return(tag, -EINVAL);
+
+        (void) device_read_db(device);
+
+        return set_contains(device->all_tags, tag);
+}
+
+_public_ int sd_device_has_current_tag(sd_device *device, const char *tag) {
+        assert_return(device, -EINVAL);
+        assert_return(tag, -EINVAL);
+
+        if (!device_database_supports_current_tags(device))
+                return sd_device_has_tag(device, tag);
+
+        (void) device_read_db(device);
+
+        return set_contains(device->current_tags, tag);
+}
+
+_public_ int sd_device_get_property_value(sd_device *device, const char *key, const char **ret_value) {
+        const char *value;
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(key, -EINVAL);
+
+        r = device_properties_prepare(device);
+        if (r < 0)
+                return r;
+
+        value = ordered_hashmap_get(device->properties, key);
+        if (!value)
+                return -ENOENT;
+
+        if (ret_value)
+                *ret_value = value;
+        return 0;
+}
+
+int device_get_property_bool(sd_device *device, const char *key) {
+        const char *value;
+        int r;
+
+        assert(device);
+        assert(key);
+
+        r = sd_device_get_property_value(device, key, &value);
+        if (r < 0)
+                return r;
+
+        return parse_boolean(value);
+}
+
+int device_get_property_int(sd_device *device, const char *key, int *ret) {
+        const char *value;
+        int r, v;
+
+        assert(device);
+        assert(key);
+
+        r = sd_device_get_property_value(device, key, &value);
+        if (r < 0)
+                return r;
+
+        r = safe_atoi(value, &v);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = v;
+        return 0;
+}
+
+_public_ int sd_device_get_trigger_uuid(sd_device *device, sd_id128_t *ret) {
+        const char *s;
+        sd_id128_t id;
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        /* Retrieves the UUID attached to a uevent when triggering it from userspace via
+         * sd_device_trigger_with_uuid() or an equivalent interface. Returns -ENOENT if the record is not
+         * caused by a synthetic event and -ENODATA if it was but no UUID was specified */
+
+        r = sd_device_get_property_value(device, "SYNTH_UUID", &s);
+        if (r < 0)
+                return r;
+
+        if (streq(s, "0")) /* SYNTH_UUID=0 is set whenever a device is triggered by userspace without specifying a UUID */
+                return -ENODATA;
+
+        r = sd_id128_from_string(s, &id);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = id;
+
+        return 0;
+}
+
+void device_clear_sysattr_cache(sd_device *device) {
+        device->sysattr_values = hashmap_free(device->sysattr_values);
+}
+
+int device_cache_sysattr_value(sd_device *device, const char *key, char *value) {
+        _unused_ _cleanup_free_ char *old_value = NULL;
+        _cleanup_free_ char *new_key = NULL;
+        int r;
+
+        assert(device);
+        assert(key);
+
+        /* This takes the reference of the input value. The input value may be NULL.
+         * This replaces the value if it already exists. */
+
+        /* First, remove the old cache entry. So, we do not need to clear cache on error. */
+        old_value = hashmap_remove2(device->sysattr_values, key, (void **) &new_key);
+        if (!new_key) {
+                new_key = strdup(key);
+                if (!new_key)
+                        return -ENOMEM;
+        }
+
+        r = hashmap_ensure_put(&device->sysattr_values, &path_hash_ops_free_free, new_key, value);
+        if (r < 0)
+                return r;
+
+        TAKE_PTR(new_key);
+
+        return 0;
+}
+
+int device_get_cached_sysattr_value(sd_device *device, const char *key, const char **ret_value) {
+        const char *k = NULL, *value;
+
+        assert(device);
+        assert(key);
+
+        value = hashmap_get2(device->sysattr_values, key, (void **) &k);
+        if (!k)
+                return -ESTALE; /* We have not read the attribute. */
+        if (!value)
+                return -ENOENT; /* We have looked up the attribute before and it did not exist. */
+        if (ret_value)
+                *ret_value = value;
+        return 0;
+}
+
+/* We cache all sysattr lookups. If an attribute does not exist, it is stored
+ * with a NULL value in the cache, otherwise the returned string is stored */
+_public_ int sd_device_get_sysattr_value(sd_device *device, const char *sysattr, const char **ret_value) {
+        _cleanup_free_ char *value = NULL, *path = NULL;
+        const char *syspath;
+        struct stat statbuf;
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(sysattr, -EINVAL);
+
+        /* look for possibly already cached result */
+        r = device_get_cached_sysattr_value(device, sysattr, ret_value);
+        if (r != -ESTALE)
+                return r;
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        path = path_join(syspath, sysattr);
+        if (!path)
+                return -ENOMEM;
+
+        if (lstat(path, &statbuf) < 0) {
+                int k;
+
+                r = -errno;
+
+                /* remember that we could not access the sysattr */
+                k = device_cache_sysattr_value(device, sysattr, NULL);
+                if (k < 0)
+                        log_device_debug_errno(device, k,
+                                               "sd-device: failed to cache attribute '%s' with NULL, ignoring: %m",
+                                               sysattr);
+
+                return r;
+        } else if (S_ISLNK(statbuf.st_mode)) {
+                /* Some core links return only the last element of the target path,
+                 * these are just values, the paths should not be exposed. */
+                if (STR_IN_SET(sysattr, "driver", "subsystem", "module")) {
+                        r = readlink_value(path, &value);
+                        if (r < 0)
+                                return r;
+                } else
+                        return -EINVAL;
+        } else if (S_ISDIR(statbuf.st_mode))
+                /* skip directories */
+                return -EISDIR;
+        else if (!(statbuf.st_mode & S_IRUSR))
+                /* skip non-readable files */
+                return -EPERM;
+        else {
+                size_t size;
+
+                /* Read attribute value, Some attributes contain embedded '\0'. So, it is necessary to
+                 * also get the size of the result. See issue #20025. */
+                r = read_full_virtual_file(path, &value, &size);
+                if (r < 0)
+                        return r;
+
+                /* drop trailing newlines */
+                while (size > 0 && strchr(NEWLINE, value[--size]))
+                        value[size] = '\0';
+        }
+
+        /* Unfortunately, we need to return 'const char*' instead of 'char*'. Hence, failure in caching
+         * sysattr value is critical unlike the other places. */
+        r = device_cache_sysattr_value(device, sysattr, value);
+        if (r < 0) {
+                log_device_debug_errno(device, r,
+                                       "sd-device: failed to cache attribute '%s' with '%s'%s: %m",
+                                       sysattr, value, ret_value ? "" : ", ignoring");
+                if (ret_value)
+                        return r;
+
+                return 0;
+        }
+
+        if (ret_value)
+                *ret_value = value;
+
+        TAKE_PTR(value);
+        return 0;
+}
+
+int device_get_sysattr_int(sd_device *device, const char *sysattr, int *ret_value) {
+        const char *value;
+        int r;
+
+        r = sd_device_get_sysattr_value(device, sysattr, &value);
+        if (r < 0)
+                return r;
+
+        int v;
+        r = safe_atoi(value, &v);
+        if (r < 0)
+                return log_device_debug_errno(device, r, "Failed to parse '%s' attribute: %m", sysattr);
+
+        if (ret_value)
+                *ret_value = v;
+        /* We return "true" if the value is positive. */
+        return v > 0;
+}
+
+int device_get_sysattr_unsigned(sd_device *device, const char *sysattr, unsigned *ret_value) {
+        const char *value;
+        int r;
+
+        r = sd_device_get_sysattr_value(device, sysattr, &value);
+        if (r < 0)
+                return r;
+
+        unsigned v;
+        r = safe_atou(value, &v);
+        if (r < 0)
+                return log_device_debug_errno(device, r, "Failed to parse '%s' attribute: %m", sysattr);
+
+        if (ret_value)
+                *ret_value = v;
+        /* We return "true" if the value is positive. */
+        return v > 0;
+}
+
+int device_get_sysattr_bool(sd_device *device, const char *sysattr) {
+        const char *value;
+        int r;
+
+        assert(device);
+        assert(sysattr);
+
+        r = sd_device_get_sysattr_value(device, sysattr, &value);
+        if (r < 0)
+                return r;
+
+        return parse_boolean(value);
+}
+
+static void device_remove_cached_sysattr_value(sd_device *device, const char *_key) {
+        _cleanup_free_ char *key = NULL;
+
+        assert(device);
+        assert(_key);
+
+        free(hashmap_remove2(device->sysattr_values, _key, (void **) &key));
+}
+
+_public_ int sd_device_set_sysattr_value(sd_device *device, const char *sysattr, const char *_value) {
+        _cleanup_free_ char *value = NULL, *path = NULL;
+        const char *syspath;
+        size_t len;
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(sysattr, -EINVAL);
+
+        /* Set the attribute and save it in the cache. */
+
+        if (!_value) {
+                /* If input value is NULL, then clear cache and not write anything. */
+                device_remove_cached_sysattr_value(device, sysattr);
+                return 0;
+        }
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        path = path_join(syspath, sysattr);
+        if (!path)
+                return -ENOMEM;
+
+        len = strlen(_value);
+
+        /* drop trailing newlines */
+        while (len > 0 && strchr(NEWLINE, _value[len - 1]))
+                len --;
+
+        /* value length is limited to 4k */
+        if (len > 4096)
+                return -EINVAL;
+
+        value = strndup(_value, len);
+        if (!value)
+                return -ENOMEM;
+
+        r = write_string_file(path, value, WRITE_STRING_FILE_DISABLE_BUFFER | WRITE_STRING_FILE_NOFOLLOW);
+        if (r < 0) {
+                /* On failure, clear cache entry, as we do not know how it fails. */
+                device_remove_cached_sysattr_value(device, sysattr);
+                return r;
+        }
+
+        /* Do not cache action string written into uevent file. */
+        if (streq(sysattr, "uevent"))
+                return 0;
+
+        r = device_cache_sysattr_value(device, sysattr, value);
+        if (r < 0)
+                log_device_debug_errno(device, r,
+                                       "sd-device: failed to cache attribute '%s' with '%s', ignoring: %m",
+                                       sysattr, value);
+        else
+                TAKE_PTR(value);
+
+        return 0;
+}
+
+_public_ int sd_device_set_sysattr_valuef(sd_device *device, const char *sysattr, const char *format, ...) {
+        _cleanup_free_ char *value = NULL;
+        va_list ap;
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(sysattr, -EINVAL);
+
+        if (!format) {
+                device_remove_cached_sysattr_value(device, sysattr);
+                return 0;
+        }
+
+        va_start(ap, format);
+        r = vasprintf(&value, format, ap);
+        va_end(ap);
+
+        if (r < 0)
+                return -ENOMEM;
+
+        return sd_device_set_sysattr_value(device, sysattr, value);
+}
+
+_public_ int sd_device_trigger(sd_device *device, sd_device_action_t action) {
+        const char *s;
+
+        assert_return(device, -EINVAL);
+
+        s = device_action_to_string(action);
+        if (!s)
+                return -EINVAL;
+
+        /* This uses the simple no-UUID interface of kernel < 4.13 */
+        return sd_device_set_sysattr_value(device, "uevent", s);
+}
+
+_public_ int sd_device_trigger_with_uuid(
+                sd_device *device,
+                sd_device_action_t action,
+                sd_id128_t *ret_uuid) {
+
+        const char *s, *j;
+        sd_id128_t u;
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        /* If no one wants to know the UUID, use the simple interface from pre-4.13 times */
+        if (!ret_uuid)
+                return sd_device_trigger(device, action);
+
+        s = device_action_to_string(action);
+        if (!s)
+                return -EINVAL;
+
+        r = sd_id128_randomize(&u);
+        if (r < 0)
+                return r;
+
+        j = strjoina(s, " ", SD_ID128_TO_UUID_STRING(u));
+
+        r = sd_device_set_sysattr_value(device, "uevent", j);
+        if (r < 0)
+                return r;
+
+        *ret_uuid = u;
+        return 0;
+}
+
+_public_ int sd_device_open(sd_device *device, int flags) {
+        _cleanup_close_ int fd = -EBADF, fd2 = -EBADF;
+        const char *devname, *subsystem = NULL;
+        uint64_t q, diskseq = 0;
+        struct stat st;
+        dev_t devnum;
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(FLAGS_SET(flags, O_PATH) || !FLAGS_SET(flags, O_NOFOLLOW), -EINVAL);
+
+        r = sd_device_get_devname(device, &devname);
+        if (r == -ENOENT)
+                return -ENOEXEC;
+        if (r < 0)
+                return r;
+
+        r = sd_device_get_devnum(device, &devnum);
+        if (r == -ENOENT)
+                return -ENOEXEC;
+        if (r < 0)
+                return r;
+
+        r = sd_device_get_subsystem(device, &subsystem);
+        if (r < 0 && r != -ENOENT)
+                return r;
+
+        fd = open(devname, FLAGS_SET(flags, O_PATH) ? flags : O_CLOEXEC|O_NOFOLLOW|O_PATH);
+        if (fd < 0)
+                return -errno;
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        if (st.st_rdev != devnum)
+                return -ENXIO;
+
+        if (streq_ptr(subsystem, "block") ? !S_ISBLK(st.st_mode) : !S_ISCHR(st.st_mode))
+                return -ENXIO;
+
+        /* If flags has O_PATH, then we cannot check diskseq. Let's return earlier. */
+        if (FLAGS_SET(flags, O_PATH))
+                return TAKE_FD(fd);
+
+        /* If the device is not initialized, then we cannot determine if we should check diskseq through
+         * ID_IGNORE_DISKSEQ property. Let's skip to check diskseq in that case. */
+        r = sd_device_get_is_initialized(device);
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                r = device_get_property_bool(device, "ID_IGNORE_DISKSEQ");
+                if (r < 0 && r != -ENOENT)
+                        return r;
+                if (r <= 0) {
+                        r = sd_device_get_diskseq(device, &diskseq);
+                        if (r < 0 && r != -ENOENT)
+                                return r;
+                }
+        }
+
+        fd2 = fd_reopen(fd, flags);
+        if (fd2 < 0)
+                return fd2;
+
+        if (diskseq == 0)
+                return TAKE_FD(fd2);
+
+        r = fd_get_diskseq(fd2, &q);
+        if (r < 0)
+                return r;
+
+        if (q != diskseq)
+                return -ENXIO;
+
+        return TAKE_FD(fd2);
+}
+
+int device_opendir(sd_device *device, const char *subdir, DIR **ret) {
+        _cleanup_closedir_ DIR *d = NULL;
+        _cleanup_free_ char *path = NULL;
+        const char *syspath;
+        int r;
+
+        assert(device);
+        assert(ret);
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        if (subdir) {
+                if (!path_is_safe(subdir))
+                        return -EINVAL;
+
+                path = path_join(syspath, subdir);
+                if (!path)
+                        return -ENOMEM;
+        }
+
+        d = opendir(path ?: syspath);
+        if (!d)
+                return -errno;
+
+        *ret = TAKE_PTR(d);
+        return 0;
+}
diff --git a/src/libsystemd/sd-device/test-device-util.c b/src/libsystemd/sd-device/test-device-util.c
new file mode 100644
index 0000000..bc8ab66
--- /dev/null
+++ b/src/libsystemd/sd-device/test-device-util.c
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "device-util.h"
+#include "tests.h"
+
+TEST(log_device_full) {
+        int r;
+
+        for (int level = LOG_ERR; level <= LOG_DEBUG; level++) {
+                log_device_full(NULL, level, "test level=%d: %m", level);
+
+                r = log_device_full_errno(NULL, level, EUCLEAN, "test level=%d errno=EUCLEAN: %m", level);
+                assert_se(r == -EUCLEAN);
+
+                r = log_device_full_errno(NULL, level, 0, "test level=%d errno=0: %m", level);
+                assert_se(r == 0);
+
+                r = log_device_full_errno(NULL, level, SYNTHETIC_ERRNO(ENODATA), "test level=%d errno=S(ENODATA): %m", level);
+                assert_se(r == -ENODATA);
+        }
+}
+
+DEFINE_TEST_MAIN(LOG_INFO);
diff --git a/src/libsystemd/sd-device/test-sd-device-monitor.c b/src/libsystemd/sd-device/test-sd-device-monitor.c
new file mode 100644
index 0000000..e124e00
--- /dev/null
+++ b/src/libsystemd/sd-device/test-sd-device-monitor.c
@@ -0,0 +1,344 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <stdbool.h>
+#include <unistd.h>
+
+#include "sd-device.h"
+#include "sd-event.h"
+
+#include "device-monitor-private.h"
+#include "device-private.h"
+#include "device-util.h"
+#include "macro.h"
+#include "path-util.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "tests.h"
+#include "virt.h"
+
+static int monitor_handler(sd_device_monitor *m, sd_device *d, void *userdata) {
+        const char *s, *syspath = userdata;
+
+        assert_se(sd_device_get_syspath(d, &s) >= 0);
+        assert_se(streq(s, syspath));
+
+        return sd_event_exit(sd_device_monitor_get_event(m), 100);
+}
+
+static void test_receive_device_fail(void) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *monitor_server = NULL, *monitor_client = NULL;
+        _cleanup_(sd_device_unrefp) sd_device *loopback = NULL;
+        const char *syspath;
+
+        log_info("/* %s */", __func__);
+
+        /* Try to send device with invalid action and without seqnum. */
+        assert_se(sd_device_new_from_syspath(&loopback, "/sys/class/net/lo") >= 0);
+        assert_se(device_add_property(loopback, "ACTION", "hoge") >= 0);
+
+        assert_se(sd_device_get_syspath(loopback, &syspath) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_server, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_server, "sender") >= 0);
+        assert_se(sd_device_monitor_start(monitor_server, NULL, NULL) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_client, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_client, "receiver") >= 0);
+        assert_se(device_monitor_allow_unicast_sender(monitor_client, monitor_server) >= 0);
+        assert_se(sd_device_monitor_start(monitor_client, monitor_handler, (void *) syspath) >= 0);
+
+        assert_se(device_monitor_send_device(monitor_server, monitor_client, loopback) >= 0);
+        assert_se(sd_event_run(sd_device_monitor_get_event(monitor_client), 0) >= 0);
+}
+
+static void test_send_receive_one(sd_device *device, bool subsystem_filter, bool tag_filter, bool use_bpf) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *monitor_server = NULL, *monitor_client = NULL;
+        const char *syspath, *subsystem, *devtype = NULL;
+
+        log_device_info(device, "/* %s(subsystem_filter=%s, tag_filter=%s, use_bpf=%s) */", __func__,
+                        true_false(subsystem_filter), true_false(tag_filter), true_false(use_bpf));
+
+        assert_se(sd_device_get_syspath(device, &syspath) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_server, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_server, "sender") >= 0);
+        assert_se(sd_device_monitor_start(monitor_server, NULL, NULL) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_client, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_client, "receiver") >= 0);
+        assert_se(device_monitor_allow_unicast_sender(monitor_client, monitor_server) >= 0);
+        assert_se(sd_device_monitor_start(monitor_client, monitor_handler, (void *) syspath) >= 0);
+
+        if (subsystem_filter) {
+                assert_se(sd_device_get_subsystem(device, &subsystem) >= 0);
+                (void) sd_device_get_devtype(device, &devtype);
+                assert_se(sd_device_monitor_filter_add_match_subsystem_devtype(monitor_client, subsystem, devtype) >= 0);
+        }
+
+        if (tag_filter)
+                FOREACH_DEVICE_TAG(device, tag)
+                        assert_se(sd_device_monitor_filter_add_match_tag(monitor_client, tag) >= 0);
+
+        if ((subsystem_filter || tag_filter) && use_bpf)
+                assert_se(sd_device_monitor_filter_update(monitor_client) >= 0);
+
+        assert_se(device_monitor_send_device(monitor_server, monitor_client, device) >= 0);
+        assert_se(sd_event_loop(sd_device_monitor_get_event(monitor_client)) == 100);
+}
+
+static void test_subsystem_filter(sd_device *device) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *monitor_server = NULL, *monitor_client = NULL;
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        const char *syspath, *subsystem;
+
+        log_device_info(device, "/* %s */", __func__);
+
+        assert_se(sd_device_get_syspath(device, &syspath) >= 0);
+        assert_se(sd_device_get_subsystem(device, &subsystem) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_server, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_server, "sender") >= 0);
+        assert_se(sd_device_monitor_start(monitor_server, NULL, NULL) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_client, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_client, "receiver") >= 0);
+        assert_se(device_monitor_allow_unicast_sender(monitor_client, monitor_server) >= 0);
+        assert_se(sd_device_monitor_filter_add_match_subsystem_devtype(monitor_client, subsystem, NULL) >= 0);
+        assert_se(sd_device_monitor_start(monitor_client, monitor_handler, (void *) syspath) >= 0);
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_add_match_subsystem(e, subsystem, false) >= 0);
+        FOREACH_DEVICE(e, d) {
+                const char *p, *s;
+
+                assert_se(sd_device_get_syspath(d, &p) >= 0);
+                assert_se(sd_device_get_subsystem(d, &s) >= 0);
+
+                assert_se(device_add_property(d, "ACTION", "add") >= 0);
+                assert_se(device_add_property(d, "SEQNUM", "10") >= 0);
+
+                log_device_debug(d, "Sending device subsystem:%s syspath:%s", s, p);
+                assert_se(device_monitor_send_device(monitor_server, monitor_client, d) >= 0);
+        }
+
+        log_device_info(device, "Sending device subsystem:%s syspath:%s", subsystem, syspath);
+        assert_se(device_monitor_send_device(monitor_server, monitor_client, device) >= 0);
+        assert_se(sd_event_loop(sd_device_monitor_get_event(monitor_client)) == 100);
+}
+
+static void test_tag_filter(sd_device *device) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *monitor_server = NULL, *monitor_client = NULL;
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        const char *syspath;
+
+        log_device_info(device, "/* %s */", __func__);
+
+        assert_se(sd_device_get_syspath(device, &syspath) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_server, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_server, "sender") >= 0);
+        assert_se(sd_device_monitor_start(monitor_server, NULL, NULL) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_client, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_client, "receiver") >= 0);
+        assert_se(device_monitor_allow_unicast_sender(monitor_client, monitor_server) >= 0);
+        assert_se(sd_device_monitor_filter_add_match_tag(monitor_client, "TEST_SD_DEVICE_MONITOR") >= 0);
+        assert_se(sd_device_monitor_start(monitor_client, monitor_handler, (void *) syspath) >= 0);
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        FOREACH_DEVICE(e, d) {
+                const char *p;
+
+                assert_se(sd_device_get_syspath(d, &p) >= 0);
+
+                assert_se(device_add_property(d, "ACTION", "add") >= 0);
+                assert_se(device_add_property(d, "SEQNUM", "10") >= 0);
+
+                log_device_debug(d, "Sending device syspath:%s", p);
+                assert_se(device_monitor_send_device(monitor_server, monitor_client, d) >= 0);
+        }
+
+        log_device_info(device, "Sending device syspath:%s", syspath);
+        assert_se(device_monitor_send_device(monitor_server, monitor_client, device) >= 0);
+        assert_se(sd_event_loop(sd_device_monitor_get_event(monitor_client)) == 100);
+
+}
+
+static void test_sysattr_filter(sd_device *device, const char *sysattr) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *monitor_server = NULL, *monitor_client = NULL;
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        const char *syspath, *sysattr_value;
+
+        log_device_info(device, "/* %s(%s) */", __func__, sysattr);
+
+        assert_se(sd_device_get_syspath(device, &syspath) >= 0);
+        assert_se(sd_device_get_sysattr_value(device, sysattr, &sysattr_value) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_server, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_server, "sender") >= 0);
+        assert_se(sd_device_monitor_start(monitor_server, NULL, NULL) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_client, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_client, "receiver") >= 0);
+        assert_se(device_monitor_allow_unicast_sender(monitor_client, monitor_server) >= 0);
+        assert_se(sd_device_monitor_filter_add_match_sysattr(monitor_client, sysattr, sysattr_value, true) >= 0);
+        assert_se(sd_device_monitor_start(monitor_client, monitor_handler, (void *) syspath) >= 0);
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_add_match_sysattr(e, sysattr, sysattr_value, false) >= 0);
+        FOREACH_DEVICE(e, d) {
+                const char *p;
+
+                assert_se(sd_device_get_syspath(d, &p) >= 0);
+
+                assert_se(device_add_property(d, "ACTION", "add") >= 0);
+                assert_se(device_add_property(d, "SEQNUM", "10") >= 0);
+
+                log_device_debug(d, "Sending device syspath:%s", p);
+                assert_se(device_monitor_send_device(monitor_server, monitor_client, d) >= 0);
+
+                /* The sysattr filter is not implemented in BPF yet. So, sending multiple devices may fills up
+                 * buffer and device_monitor_send_device() may return EAGAIN. Let's send one device here,
+                 * which should be filtered out by the receiver. */
+                break;
+        }
+
+        log_device_info(device, "Sending device syspath:%s", syspath);
+        assert_se(device_monitor_send_device(monitor_server, monitor_client, device) >= 0);
+        assert_se(sd_event_loop(sd_device_monitor_get_event(monitor_client)) == 100);
+
+}
+
+static void test_parent_filter(sd_device *device) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *monitor_server = NULL, *monitor_client = NULL;
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        const char *syspath, *parent_syspath;
+        sd_device *parent;
+        int r;
+
+        log_device_info(device, "/* %s */", __func__);
+
+        assert_se(sd_device_get_syspath(device, &syspath) >= 0);
+        r = sd_device_get_parent(device, &parent);
+        if (r < 0)
+                return (void) log_device_info(device, "Device does not have parent, skipping.");
+        assert_se(sd_device_get_syspath(parent, &parent_syspath) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_server, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_server, "sender") >= 0);
+        assert_se(sd_device_monitor_start(monitor_server, NULL, NULL) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_client, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_client, "receiver") >= 0);
+        assert_se(device_monitor_allow_unicast_sender(monitor_client, monitor_server) >= 0);
+        assert_se(sd_device_monitor_filter_add_match_parent(monitor_client, parent, true) >= 0);
+        assert_se(sd_device_monitor_start(monitor_client, monitor_handler, (void *) syspath) >= 0);
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        FOREACH_DEVICE(e, d) {
+                const char *p;
+
+                assert_se(sd_device_get_syspath(d, &p) >= 0);
+                if (path_startswith(p, parent_syspath))
+                        continue;
+
+                assert_se(device_add_property(d, "ACTION", "add") >= 0);
+                assert_se(device_add_property(d, "SEQNUM", "10") >= 0);
+
+                log_device_debug(d, "Sending device syspath:%s", p);
+                assert_se(device_monitor_send_device(monitor_server, monitor_client, d) >= 0);
+
+                /* The parent filter is not implemented in BPF yet. So, sending multiple devices may fills up
+                 * buffer and device_monitor_send_device() may return EAGAIN. Let's send one device here,
+                 * which should be filtered out by the receiver. */
+                break;
+        }
+
+        log_device_info(device, "Sending device syspath:%s", syspath);
+        assert_se(device_monitor_send_device(monitor_server, monitor_client, device) >= 0);
+        assert_se(sd_event_loop(sd_device_monitor_get_event(monitor_client)) == 100);
+
+}
+
+static void test_sd_device_monitor_filter_remove(sd_device *device) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *monitor_server = NULL, *monitor_client = NULL;
+        const char *syspath;
+
+        log_device_info(device, "/* %s */", __func__);
+
+        assert_se(sd_device_get_syspath(device, &syspath) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_server, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_server, "sender") >= 0);
+        assert_se(sd_device_monitor_start(monitor_server, NULL, NULL) >= 0);
+
+        assert_se(device_monitor_new_full(&monitor_client, MONITOR_GROUP_NONE, -1) >= 0);
+        assert_se(sd_device_monitor_set_description(monitor_client, "receiver") >= 0);
+        assert_se(device_monitor_allow_unicast_sender(monitor_client, monitor_server) >= 0);
+        assert_se(sd_device_monitor_start(monitor_client, monitor_handler, (void *) syspath) >= 0);
+
+        assert_se(sd_device_monitor_filter_add_match_subsystem_devtype(monitor_client, "hoge", NULL) >= 0);
+        assert_se(sd_device_monitor_filter_update(monitor_client) >= 0);
+
+        assert_se(device_monitor_send_device(monitor_server, monitor_client, device) >= 0);
+        assert_se(sd_event_run(sd_device_monitor_get_event(monitor_client), 0) >= 0);
+
+        assert_se(sd_device_monitor_filter_remove(monitor_client) >= 0);
+
+        assert_se(device_monitor_send_device(monitor_server, monitor_client, device) >= 0);
+        assert_se(sd_event_loop(sd_device_monitor_get_event(monitor_client)) == 100);
+}
+
+int main(int argc, char *argv[]) {
+        _cleanup_(sd_device_unrefp) sd_device *loopback = NULL, *sda = NULL;
+        int r;
+
+        test_setup_logging(LOG_INFO);
+
+        if (getuid() != 0)
+                return log_tests_skipped("not root");
+
+        if (path_is_read_only_fs("/sys") > 0)
+                return log_tests_skipped("Running in container");
+
+        test_receive_device_fail();
+
+        assert_se(sd_device_new_from_syspath(&loopback, "/sys/class/net/lo") >= 0);
+        assert_se(device_add_property(loopback, "ACTION", "add") >= 0);
+        assert_se(device_add_property(loopback, "SEQNUM", "10") >= 0);
+        assert_se(device_add_tag(loopback, "TEST_SD_DEVICE_MONITOR", true) >= 0);
+
+        test_send_receive_one(loopback, false, false, false);
+        test_send_receive_one(loopback,  true, false, false);
+        test_send_receive_one(loopback, false,  true, false);
+        test_send_receive_one(loopback,  true,  true, false);
+        test_send_receive_one(loopback,  true, false,  true);
+        test_send_receive_one(loopback, false,  true,  true);
+        test_send_receive_one(loopback,  true,  true,  true);
+
+        test_subsystem_filter(loopback);
+        test_tag_filter(loopback);
+        test_sysattr_filter(loopback, "ifindex");
+        test_sd_device_monitor_filter_remove(loopback);
+
+        r = sd_device_new_from_subsystem_sysname(&sda, "block", "sda");
+        if (r < 0) {
+                log_info_errno(r, "Failed to create sd_device for sda, skipping remaining tests: %m");
+                return 0;
+        }
+
+        assert_se(device_add_property(sda, "ACTION", "change") >= 0);
+        assert_se(device_add_property(sda, "SEQNUM", "11") >= 0);
+
+        test_send_receive_one(sda, false, false, false);
+        test_send_receive_one(sda,  true, false, false);
+        test_send_receive_one(sda, false,  true, false);
+        test_send_receive_one(sda,  true,  true, false);
+        test_send_receive_one(sda,  true, false,  true);
+        test_send_receive_one(sda, false,  true,  true);
+        test_send_receive_one(sda,  true,  true,  true);
+
+        test_parent_filter(sda);
+
+        return 0;
+}
diff --git a/src/libsystemd/sd-device/test-sd-device-thread.c b/src/libsystemd/sd-device/test-sd-device-thread.c
new file mode 100644
index 0000000..c99d179
--- /dev/null
+++ b/src/libsystemd/sd-device/test-sd-device-thread.c
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "sd-device.h"
+
+#include "device-util.h"
+
+#define handle_error_errno(error, msg)                          \
+        ({                                                      \
+                errno = abs(error);                             \
+                perror(msg);                                    \
+                EXIT_FAILURE;                                   \
+        })
+
+static void* thread(void *p) {
+        sd_device **d = p;
+
+        *d = sd_device_unref(*d);
+
+        return NULL;
+}
+
+int main(int argc, char *argv[]) {
+        sd_device *loopback;
+        pthread_t t;
+        int r;
+
+        r = sd_device_new_from_syspath(&loopback, "/sys/class/net/lo");
+        if (r < 0)
+                return handle_error_errno(r, "Failed to create loopback device object");
+
+        FOREACH_DEVICE_PROPERTY(loopback, key, value)
+                printf("%s=%s\n", key, value);
+
+        r = pthread_create(&t, NULL, thread, &loopback);
+        if (r != 0)
+                return handle_error_errno(r, "Failed to create thread");
+
+        r = pthread_join(t, NULL);
+        if (r != 0)
+                return handle_error_errno(r, "Failed to wait thread finished");
+
+        if (loopback)
+                return handle_error_errno(r, "loopback device is not unref()ed");
+
+        return 0;
+}
diff --git a/src/libsystemd/sd-device/test-sd-device.c b/src/libsystemd/sd-device/test-sd-device.c
new file mode 100644
index 0000000..bce99b5
--- /dev/null
+++ b/src/libsystemd/sd-device/test-sd-device.c
@@ -0,0 +1,678 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <ctype.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "device-enumerator-private.h"
+#include "device-internal.h"
+#include "device-private.h"
+#include "device-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "hashmap.h"
+#include "nulstr-util.h"
+#include "path-util.h"
+#include "rm-rf.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "tests.h"
+#include "time-util.h"
+#include "tmpfile-util.h"
+#include "udev-util.h"
+
+static void test_sd_device_one(sd_device *d) {
+        _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
+        const char *syspath, *sysname, *subsystem = NULL, *devname, *val;
+        bool is_block = false;
+        dev_t devnum;
+        usec_t usec;
+        int ifindex, r;
+
+        assert_se(sd_device_get_syspath(d, &syspath) >= 0);
+        assert_se(path_startswith(syspath, "/sys"));
+        assert_se(sd_device_get_sysname(d, &sysname) >= 0);
+
+        log_info("%s(%s)", __func__, syspath);
+
+        assert_se(sd_device_new_from_syspath(&dev, syspath) >= 0);
+        assert_se(sd_device_get_syspath(dev, &val) >= 0);
+        assert_se(streq(syspath, val));
+        dev = sd_device_unref(dev);
+
+        assert_se(sd_device_new_from_path(&dev, syspath) >= 0);
+        assert_se(sd_device_get_syspath(dev, &val) >= 0);
+        assert_se(streq(syspath, val));
+        dev = sd_device_unref(dev);
+
+        r = sd_device_get_ifindex(d, &ifindex);
+        if (r >= 0) {
+                assert_se(ifindex > 0);
+
+                r = sd_device_new_from_ifindex(&dev, ifindex);
+                if (r == -ENODEV)
+                        log_device_warning_errno(d, r,
+                                                 "Failed to create sd-device object from ifindex %i. "
+                                                 "Maybe running on a non-host network namespace.", ifindex);
+                else {
+                        assert_se(r >= 0);
+                        assert_se(sd_device_get_syspath(dev, &val) >= 0);
+                        assert_se(streq(syspath, val));
+                        dev = sd_device_unref(dev);
+                }
+
+                /* This does not require the interface really exists on the network namespace.
+                 * Hence, this should always succeed. */
+                assert_se(sd_device_new_from_ifname(&dev, sysname) >= 0);
+                assert_se(sd_device_get_syspath(dev, &val) >= 0);
+                assert_se(streq(syspath, val));
+                dev = sd_device_unref(dev);
+        } else
+                assert_se(r == -ENOENT);
+
+        r = sd_device_get_subsystem(d, &subsystem);
+        if (r < 0)
+                assert_se(r == -ENOENT);
+        else if (!streq(subsystem, "gpio")) { /* Unfortunately, there exist /sys/class/gpio and /sys/bus/gpio.
+                                               * Hence, sd_device_new_from_subsystem_sysname() and
+                                               * sd_device_new_from_device_id() may not work as expected. */
+                const char *name, *id;
+
+                if (streq(subsystem, "drivers"))
+                        name = strjoina(d->driver_subsystem, ":", sysname);
+                else
+                        name = sysname;
+                assert_se(sd_device_new_from_subsystem_sysname(&dev, subsystem, name) >= 0);
+                assert_se(sd_device_get_syspath(dev, &val) >= 0);
+                assert_se(streq(syspath, val));
+                dev = sd_device_unref(dev);
+
+                /* The device ID depends on subsystem. */
+                assert_se(device_get_device_id(d, &id) >= 0);
+                r = sd_device_new_from_device_id(&dev, id);
+                if (r == -ENODEV && ifindex > 0)
+                        log_device_warning_errno(d, r,
+                                                 "Failed to create sd-device object from device ID \"%s\". "
+                                                 "Maybe running on a non-host network namespace.", id);
+                else {
+                        assert_se(r >= 0);
+                        assert_se(sd_device_get_syspath(dev, &val) >= 0);
+                        assert_se(streq(syspath, val));
+                        dev = sd_device_unref(dev);
+                }
+
+                /* These require udev database, and reading database requires device ID. */
+                r = sd_device_get_is_initialized(d);
+                if (r > 0) {
+                        r = sd_device_get_usec_since_initialized(d, &usec);
+                        assert_se((r >= 0 && usec > 0) || r == -ENODATA);
+                } else
+                        assert(r == 0);
+
+                r = sd_device_get_property_value(d, "ID_NET_DRIVER", &val);
+                assert_se(r >= 0 || r == -ENOENT);
+        }
+
+        is_block = streq_ptr(subsystem, "block");
+
+        r = sd_device_get_devname(d, &devname);
+        if (r >= 0) {
+                r = sd_device_new_from_devname(&dev, devname);
+                if (r >= 0) {
+                        assert_se(sd_device_get_syspath(dev, &val) >= 0);
+                        assert_se(streq(syspath, val));
+                        dev = sd_device_unref(dev);
+                } else
+                        assert_se(r == -ENODEV || ERRNO_IS_PRIVILEGE(r));
+
+                r = sd_device_new_from_path(&dev, devname);
+                if (r >= 0) {
+                        assert_se(sd_device_get_syspath(dev, &val) >= 0);
+                        assert_se(streq(syspath, val));
+                        dev = sd_device_unref(dev);
+
+                        _cleanup_close_ int fd = -EBADF;
+                        fd = sd_device_open(d, O_CLOEXEC| O_NONBLOCK | (is_block ? O_RDONLY : O_NOCTTY | O_PATH));
+                        assert_se(fd >= 0 || ERRNO_IS_PRIVILEGE(fd));
+                } else
+                        assert_se(r == -ENODEV || ERRNO_IS_PRIVILEGE(r));
+        } else
+                assert_se(r == -ENOENT);
+
+        r = sd_device_get_devnum(d, &devnum);
+        if (r >= 0) {
+                _cleanup_free_ char *p = NULL;
+
+                assert_se(major(devnum) > 0);
+
+                assert_se(sd_device_new_from_devnum(&dev, is_block ? 'b' : 'c', devnum) >= 0);
+                assert_se(sd_device_get_syspath(dev, &val) >= 0);
+                assert_se(streq(syspath, val));
+                dev = sd_device_unref(dev);
+
+                assert_se(asprintf(&p, "/dev/%s/%u:%u", is_block ? "block" : "char", major(devnum), minor(devnum)) >= 0);
+                assert_se(sd_device_new_from_devname(&dev, p) >= 0);
+                assert_se(sd_device_get_syspath(dev, &val) >= 0);
+                assert_se(streq(syspath, val));
+                dev = sd_device_unref(dev);
+
+                assert_se(sd_device_new_from_path(&dev, p) >= 0);
+                assert_se(sd_device_get_syspath(dev, &val) >= 0);
+                assert_se(streq(syspath, val));
+                dev = sd_device_unref(dev);
+        } else
+                assert_se(r == -ENOENT);
+
+        assert_se(sd_device_get_devpath(d, &val) >= 0);
+
+        r = sd_device_get_devtype(d, &val);
+        assert_se(r >= 0 || r == -ENOENT);
+
+        r = sd_device_get_driver(d, &val);
+        assert_se(r >= 0 || r == -ENOENT);
+
+        r = sd_device_get_sysnum(d, &val);
+        if (r >= 0) {
+                assert_se(val > sysname);
+                assert_se(val < sysname + strlen(sysname));
+                assert_se(in_charset(val, DIGITS));
+                assert_se(!ascii_isdigit(val[-1]));
+        } else
+                assert_se(r == -ENOENT);
+
+        r = sd_device_get_sysattr_value(d, "nsid", NULL);
+        if (r >= 0) {
+                unsigned x;
+
+                assert_se(device_get_sysattr_unsigned(d, "nsid", NULL) >= 0);
+                r = device_get_sysattr_unsigned(d, "nsid", &x);
+                assert_se(r >= 0);
+                assert_se((x > 0) == (r > 0));
+        } else
+                assert_se(ERRNO_IS_PRIVILEGE(r) || IN_SET(r, -ENOENT, -EINVAL));
+}
+
+TEST(sd_device_enumerator_devices) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_allow_uninitialized(e) >= 0);
+        /* On some CI environments, it seems some loop block devices and corresponding bdi devices sometimes
+         * disappear during running this test. Let's exclude them here for stability. */
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "bdi", false) >= 0);
+        assert_se(sd_device_enumerator_add_nomatch_sysname(e, "loop*") >= 0);
+        /* On CentOS CI, systemd-networkd-tests.py may be running when this test is invoked. The networkd
+         * test creates and removes many network interfaces, and may interfere with this test. */
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "net", false) >= 0);
+        FOREACH_DEVICE(e, d)
+                test_sd_device_one(d);
+}
+
+TEST(sd_device_enumerator_subsystems) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_allow_uninitialized(e) >= 0);
+        FOREACH_SUBSYSTEM(e, d)
+                test_sd_device_one(d);
+}
+
+static void test_sd_device_enumerator_filter_subsystem_one(
+                const char *subsystem,
+                Hashmap *h,
+                unsigned *ret_n_new_dev,
+                unsigned *ret_n_removed_dev) {
+
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        unsigned n_new_dev = 0, n_removed_dev = 0;
+        sd_device *dev;
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_add_match_subsystem(e, subsystem, true) >= 0);
+        assert_se(sd_device_enumerator_add_nomatch_sysname(e, "loop*") >= 0);
+
+        FOREACH_DEVICE(e, d) {
+                const char *syspath;
+                sd_device *t;
+
+                assert_se(sd_device_get_syspath(d, &syspath) >= 0);
+                t = hashmap_remove(h, syspath);
+
+                if (!t) {
+                        log_warning("New device found: subsystem:%s syspath:%s", subsystem, syspath);
+                        n_new_dev++;
+                }
+
+                assert_se(!sd_device_unref(t));
+        }
+
+        HASHMAP_FOREACH(dev, h) {
+                const char *syspath;
+
+                assert_se(sd_device_get_syspath(dev, &syspath) >= 0);
+                log_warning("Device removed: subsystem:%s syspath:%s", subsystem, syspath);
+                n_removed_dev++;
+
+                assert_se(!sd_device_unref(dev));
+        }
+
+        hashmap_free(h);
+
+        *ret_n_new_dev = n_new_dev;
+        *ret_n_removed_dev = n_removed_dev;
+}
+
+static bool test_sd_device_enumerator_filter_subsystem_trial(void) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        _cleanup_hashmap_free_ Hashmap *subsystems = NULL;
+        unsigned n_new_dev = 0, n_removed_dev = 0;
+        Hashmap *h;
+        char *s;
+
+        assert_se(subsystems = hashmap_new(&string_hash_ops));
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        /* See comments in TEST(sd_device_enumerator_devices). */
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "bdi", false) >= 0);
+        assert_se(sd_device_enumerator_add_nomatch_sysname(e, "loop*") >= 0);
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "net", false) >= 0);
+
+        FOREACH_DEVICE(e, d) {
+                const char *syspath, *subsystem;
+                int r;
+
+                assert_se(sd_device_get_syspath(d, &syspath) >= 0);
+
+                r = sd_device_get_subsystem(d, &subsystem);
+                assert_se(r >= 0 || r == -ENOENT);
+                if (r < 0)
+                        continue;
+
+                h = hashmap_get(subsystems, subsystem);
+                if (!h) {
+                        char *str;
+                        assert_se(str = strdup(subsystem));
+                        assert_se(h = hashmap_new(&string_hash_ops));
+                        assert_se(hashmap_put(subsystems, str, h) >= 0);
+                }
+
+                assert_se(hashmap_put(h, syspath, d) >= 0);
+                assert_se(sd_device_ref(d));
+
+                log_debug("Added subsystem:%s syspath:%s", subsystem, syspath);
+        }
+
+        while ((h = hashmap_steal_first_key_and_value(subsystems, (void**) &s))) {
+                unsigned n, m;
+
+                test_sd_device_enumerator_filter_subsystem_one(s, TAKE_PTR(h), &n, &m);
+                free(s);
+
+                n_new_dev += n;
+                n_removed_dev += m;
+        }
+
+        if (n_new_dev > 0)
+                log_warning("%u new devices are found in re-scan", n_new_dev);
+        if (n_removed_dev > 0)
+                log_warning("%u devices removed in re-scan", n_removed_dev);
+
+        return n_new_dev + n_removed_dev == 0;
+}
+
+static bool test_sd_device_enumerator_filter_subsystem_trial_many(void) {
+        for (unsigned i = 0; i < 20; i++) {
+                log_debug("%s(): trial %u", __func__, i);
+                if (test_sd_device_enumerator_filter_subsystem_trial())
+                        return true;
+        }
+
+        return false;
+}
+
+static int on_inotify(sd_event_source *s, const struct inotify_event *event, void *userdata) {
+        if (test_sd_device_enumerator_filter_subsystem_trial_many())
+                return sd_event_exit(sd_event_source_get_event(s), 0);
+
+        return sd_event_exit(sd_event_source_get_event(s), -EBUSY);
+}
+
+TEST(sd_device_enumerator_filter_subsystem) {
+        /* The test test_sd_device_enumerator_filter_subsystem_trial() is quite racy. Let's run the function
+         * several times after the udev queue becomes empty. */
+
+        if (!udev_available() || (access("/run/udev", F_OK) < 0 && errno == ENOENT)) {
+                assert_se(test_sd_device_enumerator_filter_subsystem_trial_many());
+                return;
+        }
+
+        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
+        assert_se(sd_event_default(&event) >= 0);
+        assert_se(sd_event_add_inotify(event, NULL, "/run/udev" , IN_DELETE, on_inotify, NULL) >= 0);
+
+        if (udev_queue_is_empty() == 0) {
+                log_debug("udev queue is not empty, waiting for all queued events to be processed.");
+                assert_se(sd_event_loop(event) >= 0);
+        } else
+                assert_se(test_sd_device_enumerator_filter_subsystem_trial_many());
+}
+
+TEST(sd_device_enumerator_add_match_sysattr) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        sd_device *dev;
+        int ifindex;
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_allow_uninitialized(e) >= 0);
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "net", true) >= 0);
+        assert_se(sd_device_enumerator_add_match_sysattr(e, "ifindex", "1", true) >= 0);
+        assert_se(sd_device_enumerator_add_match_sysattr(e, "ifindex", "hoge", true) >= 0);
+        assert_se(sd_device_enumerator_add_match_sysattr(e, "ifindex", "foo", true) >= 0);
+        assert_se(sd_device_enumerator_add_match_sysattr(e, "ifindex", "bar", false) >= 0);
+        assert_se(sd_device_enumerator_add_match_sysattr(e, "ifindex", "baz", false) >= 0);
+
+        dev = sd_device_enumerator_get_device_first(e);
+        assert_se(dev);
+        assert_se(sd_device_get_ifindex(dev, &ifindex) >= 0);
+        assert_se(ifindex == 1);
+
+        assert_se(!sd_device_enumerator_get_device_next(e));
+}
+
+TEST(sd_device_enumerator_add_match_property) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        sd_device *dev;
+        int ifindex;
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_allow_uninitialized(e) >= 0);
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "net", true) >= 0);
+        assert_se(sd_device_enumerator_add_match_sysattr(e, "ifindex", "1", true) >= 0);
+        assert_se(sd_device_enumerator_add_match_property(e, "IFINDE*", "1*") >= 0);
+        assert_se(sd_device_enumerator_add_match_property(e, "IFINDE*", "hoge") >= 0);
+        assert_se(sd_device_enumerator_add_match_property(e, "IFINDE*", NULL) >= 0);
+        assert_se(sd_device_enumerator_add_match_property(e, "AAAAA", "BBBB") >= 0);
+        assert_se(sd_device_enumerator_add_match_property(e, "FOOOO", NULL) >= 0);
+
+        dev = sd_device_enumerator_get_device_first(e);
+        assert_se(dev);
+        assert_se(sd_device_get_ifindex(dev, &ifindex) >= 0);
+        assert_se(ifindex == 1);
+}
+
+TEST(sd_device_enumerator_add_match_property_required) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        sd_device *dev;
+        int ifindex;
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_allow_uninitialized(e) >= 0);
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "net", true) >= 0);
+        assert_se(sd_device_enumerator_add_match_sysattr(e, "ifindex", "1", true) >= 0);
+        assert_se(sd_device_enumerator_add_match_property_required(e, "IFINDE*", "1*") >= 0);
+
+        /* Only one required match which should be satisfied. */
+        dev = sd_device_enumerator_get_device_first(e);
+        assert_se(dev);
+        assert_se(sd_device_get_ifindex(dev, &ifindex) >= 0);
+        assert_se(ifindex == 1);
+
+        /* Now let's add a bunch of garbage properties which should not be satisfied. */
+        assert_se(sd_device_enumerator_add_match_property_required(e, "IFINDE*", "hoge") >= 0);
+        assert_se(sd_device_enumerator_add_match_property_required(e, "IFINDE*", NULL) >= 0);
+        assert_se(sd_device_enumerator_add_match_property_required(e, "AAAAA", "BBBB") >= 0);
+        assert_se(sd_device_enumerator_add_match_property_required(e, "FOOOO", NULL) >= 0);
+
+        assert_se(!sd_device_enumerator_get_device_first(e));
+}
+
+static void check_parent_match(sd_device_enumerator *e, sd_device *dev) {
+        const char *syspath;
+        bool found = false;
+
+        assert_se(sd_device_get_syspath(dev, &syspath) >= 0);
+
+        FOREACH_DEVICE(e, d) {
+                const char *s;
+
+                assert_se(sd_device_get_syspath(d, &s) >= 0);
+                if (streq(s, syspath)) {
+                        found = true;
+                        break;
+                }
+        }
+
+        if (!found) {
+                log_device_debug(dev, "not enumerated, already removed??");
+                /* If the original device not found, then the device should be already removed. */
+                assert_se(access(syspath, F_OK) < 0);
+                assert_se(errno == ENOENT);
+        }
+}
+
+TEST(sd_device_enumerator_add_match_parent) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        int r;
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_allow_uninitialized(e) >= 0);
+        /* See comments in TEST(sd_device_enumerator_devices). */
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "bdi", false) >= 0);
+        assert_se(sd_device_enumerator_add_nomatch_sysname(e, "loop*") >= 0);
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "net", false) >= 0);
+
+        if (!slow_tests_enabled())
+                assert_se(sd_device_enumerator_add_match_subsystem(e, "block", true) >= 0);
+
+        FOREACH_DEVICE(e, dev) {
+                _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *p = NULL;
+                const char *syspath;
+                sd_device *parent;
+
+                assert_se(sd_device_get_syspath(dev, &syspath) >= 0);
+
+                r = sd_device_get_parent(dev, &parent);
+                if (r < 0) {
+                        assert_se(ERRNO_IS_DEVICE_ABSENT(r));
+                        continue;
+                }
+
+                log_debug("> %s", syspath);
+
+                assert_se(sd_device_enumerator_new(&p) >= 0);
+                assert_se(sd_device_enumerator_allow_uninitialized(p) >= 0);
+                assert_se(sd_device_enumerator_add_match_parent(p, parent) >= 0);
+
+                check_parent_match(p, dev);
+
+                /* If the device does not have subsystem, then it is not enumerated. */
+                r = sd_device_get_subsystem(parent, NULL);
+                if (r < 0) {
+                        assert_se(r == -ENOENT);
+                        continue;
+                }
+                check_parent_match(p, parent);
+        }
+}
+
+TEST(sd_device_get_child) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        int r;
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_allow_uninitialized(e) >= 0);
+        /* See comments in TEST(sd_device_enumerator_devices). */
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "bdi", false) >= 0);
+        assert_se(sd_device_enumerator_add_nomatch_sysname(e, "loop*") >= 0);
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "net", false) >= 0);
+
+        if (!slow_tests_enabled())
+                assert_se(sd_device_enumerator_add_match_subsystem(e, "block", true) >= 0);
+
+        FOREACH_DEVICE(e, dev) {
+                const char *syspath, *parent_syspath, *expected_suffix, *suffix;
+                sd_device *parent;
+                bool found = false;
+
+                assert_se(sd_device_get_syspath(dev, &syspath) >= 0);
+
+                r = sd_device_get_parent(dev, &parent);
+                if (r < 0) {
+                        assert_se(ERRNO_IS_DEVICE_ABSENT(r));
+                        continue;
+                }
+
+                assert_se(sd_device_get_syspath(parent, &parent_syspath) >= 0);
+                assert_se(expected_suffix = path_startswith(syspath, parent_syspath));
+
+                log_debug("> %s", syspath);
+
+                FOREACH_DEVICE_CHILD_WITH_SUFFIX(parent, child, suffix) {
+                        const char *s;
+
+                        assert_se(child);
+                        assert_se(suffix);
+
+                        if (!streq(suffix, expected_suffix))
+                                continue;
+
+                        assert_se(sd_device_get_syspath(child, &s) >= 0);
+                        assert_se(streq(s, syspath));
+                        found = true;
+                        break;
+                }
+                assert_se(found);
+        }
+}
+
+TEST(sd_device_new_from_nulstr) {
+        const char *devlinks =
+                "/dev/disk/by-partuuid/1290d63a-42cc-4c71-b87c-xxxxxxxxxxxx\0"
+                "/dev/disk/by-path/pci-0000:00:0f.0-scsi-0:0:0:0-part3\0"
+                "/dev/disk/by-label/Arch\\x20Linux\0"
+                "/dev/disk/by-uuid/a07b87e5-4af5-4a59-bde9-yyyyyyyyyyyy\0"
+                "/dev/disk/by-partlabel/Arch\\x20Linux\0"
+                "\0";
+
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL, *from_nulstr = NULL;
+        _cleanup_free_ char *nulstr_copy = NULL;
+        const char *nulstr;
+        size_t len;
+
+        assert_se(sd_device_new_from_syspath(&device, "/sys/class/net/lo") >= 0);
+
+        /* Yeah, of course, setting devlink to the loopback interface is nonsense. But this is just a
+         * test for generating and parsing nulstr. For issue #17772. */
+        NULSTR_FOREACH(devlink, devlinks) {
+                log_device_info(device, "setting devlink: %s", devlink);
+                assert_se(device_add_devlink(device, devlink) >= 0);
+                assert_se(set_contains(device->devlinks, devlink));
+        }
+
+        /* For issue #23799 */
+        assert_se(device_add_tag(device, "tag1", false) >= 0);
+        assert_se(device_add_tag(device, "tag2", false) >= 0);
+        assert_se(device_add_tag(device, "current-tag1", true) >= 0);
+        assert_se(device_add_tag(device, "current-tag2", true) >= 0);
+
+        /* These properties are necessary for device_new_from_nulstr(). See device_verify(). */
+        assert_se(device_add_property_internal(device, "SEQNUM", "1") >= 0);
+        assert_se(device_add_property_internal(device, "ACTION", "change") >= 0);
+
+        assert_se(device_get_properties_nulstr(device, &nulstr, &len) >= 0);
+        assert_se(nulstr_copy = newdup(char, nulstr, len));
+        assert_se(device_new_from_nulstr(&from_nulstr, nulstr_copy, len) >= 0);
+
+        assert_se(sd_device_has_tag(from_nulstr, "tag1") == 1);
+        assert_se(sd_device_has_tag(from_nulstr, "tag2") == 1);
+        assert_se(sd_device_has_tag(from_nulstr, "current-tag1") == 1);
+        assert_se(sd_device_has_tag(from_nulstr, "current-tag2") == 1);
+        assert_se(sd_device_has_current_tag(from_nulstr, "tag1") == 0);
+        assert_se(sd_device_has_current_tag(from_nulstr, "tag2") == 0);
+        assert_se(sd_device_has_current_tag(from_nulstr, "current-tag1") == 1);
+        assert_se(sd_device_has_current_tag(from_nulstr, "current-tag2") == 1);
+
+        NULSTR_FOREACH(devlink, devlinks) {
+                log_device_info(from_nulstr, "checking devlink: %s", devlink);
+                assert_se(set_contains(from_nulstr->devlinks, devlink));
+        }
+}
+
+TEST(sd_device_new_from_path) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        _cleanup_(rm_rf_physical_and_freep) char *tmpdir = NULL;
+        int r;
+
+        assert_se(mkdtemp_malloc("/tmp/test-sd-device.XXXXXXX", &tmpdir) >= 0);
+
+        assert_se(sd_device_enumerator_new(&e) >= 0);
+        assert_se(sd_device_enumerator_allow_uninitialized(e) >= 0);
+        assert_se(sd_device_enumerator_add_match_subsystem(e, "block", true) >= 0);
+        assert_se(sd_device_enumerator_add_nomatch_sysname(e, "loop*") >= 0);
+        assert_se(sd_device_enumerator_add_match_property(e, "DEVNAME", "*") >= 0);
+
+        FOREACH_DEVICE(e, dev) {
+                _cleanup_(sd_device_unrefp) sd_device *d = NULL;
+                const char *syspath, *devpath, *sysname, *s;
+                _cleanup_free_ char *path = NULL;
+
+                assert_se(sd_device_get_sysname(dev, &sysname) >= 0);
+
+                log_debug("%s(%s)", __func__, sysname);
+
+                assert_se(sd_device_get_syspath(dev, &syspath) >= 0);
+                assert_se(sd_device_new_from_path(&d, syspath) >= 0);
+                assert_se(sd_device_get_syspath(d, &s) >= 0);
+                assert_se(streq(s, syspath));
+                d = sd_device_unref(d);
+
+                assert_se(sd_device_get_devname(dev, &devpath) >= 0);
+                r = sd_device_new_from_path(&d, devpath);
+                if (r >= 0) {
+                        assert_se(sd_device_get_syspath(d, &s) >= 0);
+                        assert_se(streq(s, syspath));
+                        d = sd_device_unref(d);
+                } else
+                        assert_se(r == -ENODEV || ERRNO_IS_PRIVILEGE(r));
+
+                assert_se(path = path_join(tmpdir, sysname));
+                assert_se(symlink(syspath, path) >= 0);
+                assert_se(sd_device_new_from_path(&d, path) >= 0);
+                assert_se(sd_device_get_syspath(d, &s) >= 0);
+                assert_se(streq(s, syspath));
+        }
+}
+
+static void test_devname_from_devnum_one(const char *path) {
+        _cleanup_free_ char *resolved = NULL;
+        struct stat st;
+
+        log_debug("> %s", path);
+
+        if (stat(path, &st) < 0) {
+                assert_se(errno == ENOENT);
+                log_notice("Path %s not found, skipping test", path);
+                return;
+        }
+
+        assert_se(devname_from_devnum(st.st_mode, st.st_rdev, &resolved) >= 0);
+        assert_se(path_equal(path, resolved));
+        resolved = mfree(resolved);
+        assert_se(devname_from_stat_rdev(&st, &resolved) >= 0);
+        assert_se(path_equal(path, resolved));
+}
+
+TEST(devname_from_devnum) {
+        test_devname_from_devnum_one("/dev/null");
+        test_devname_from_devnum_one("/dev/zero");
+        test_devname_from_devnum_one("/dev/full");
+        test_devname_from_devnum_one("/dev/random");
+        test_devname_from_devnum_one("/dev/urandom");
+        test_devname_from_devnum_one("/dev/tty");
+
+        if (is_device_node("/run/systemd/inaccessible/blk") > 0) {
+                test_devname_from_devnum_one("/run/systemd/inaccessible/chr");
+                test_devname_from_devnum_one("/run/systemd/inaccessible/blk");
+        }
+}
+
+DEFINE_TEST_MAIN(LOG_INFO);