Adding upstream version 255.4.upstream/255.4

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

1 files changed, 799 insertions, 0 deletions

diff --git a/src/journal/journald-context.c b/src/journal/journald-context.c
new file mode 100644
index 0000000..f5f6ec5
--- /dev/null
+++ b/src/journal/journald-context.c
@@ -0,0 +1,799 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#if HAVE_SELINUX
+#include <selinux/selinux.h>
+#endif
+
+#include "alloc-util.h"
+#include "audit-util.h"
+#include "cgroup-util.h"
+#include "env-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "iovec-util.h"
+#include "journal-internal.h"
+#include "journal-util.h"
+#include "journald-client.h"
+#include "journald-context.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "process-util.h"
+#include "procfs-util.h"
+#include "string-util.h"
+#include "syslog-util.h"
+#include "unaligned.h"
+#include "user-util.h"
+
+/* This implements a metadata cache for clients, which are identified by their PID. Requesting metadata through /proc
+ * is expensive, hence let's cache the data if we can. Note that this means the metadata might be out-of-date when we
+ * store it, but it might already be anyway, as we request the data asynchronously from /proc at a different time the
+ * log entry was originally created. We hence just increase the "window of inaccuracy" a bit.
+ *
+ * The cache is indexed by the PID. Entries may be "pinned" in the cache, in which case the entries are not removed
+ * until they are unpinned. Unpinned entries are kept around until cache pressure is seen. Cache entries older than 5s
+ * are never used (a sad attempt to deal with the UNIX weakness of PIDs reuse), cache entries older than 1s are
+ * refreshed in an incremental way (meaning: data is reread from /proc, but any old data we can't refresh is not
+ * flushed out). Data newer than 1s is used immediately without refresh.
+ *
+ * Log stream clients (i.e. all clients using the AF_UNIX/SOCK_STREAM stdout/stderr transport) will pin a cache entry
+ * as long as their socket is connected. Note that cache entries are shared between different transports. That means a
+ * cache entry pinned for the stream connection logic may be reused for the syslog or native protocols.
+ *
+ * Caching metadata like this has two major benefits:
+ *
+ * 1. Reading metadata is expensive, and we can thus substantially speed up log processing under flood.
+ *
+ * 2. Because metadata caching is shared between stream and datagram transports and stream connections pin a cache
+ *    entry there's a good chance we can properly map a substantial set of datagram log messages to their originating
+ *    service, as all services (unless explicitly configured otherwise) will have their stdout/stderr connected to a
+ *    stream connection. This should improve cases where a service process logs immediately before exiting and we
+ *    previously had trouble associating the log message with the service.
+ *
+ * NB: With and without the metadata cache: the implicitly added entry metadata in the journal (with the exception of
+ *     UID/PID/GID and SELinux label) must be understood as possibly slightly out of sync (i.e. sometimes slightly older
+ *     and sometimes slightly newer than what was current at the log event).
+ */
+
+/* We refresh every 1s */
+#define REFRESH_USEC (1*USEC_PER_SEC)
+
+/* Data older than 5s we flush out */
+#define MAX_USEC (5*USEC_PER_SEC)
+
+/* Keep at most 16K entries in the cache. (Note though that this limit may be violated if enough streams pin entries in
+ * the cache, in which case we *do* permit this limit to be breached. That's safe however, as the number of stream
+ * clients itself is limited.) */
+#define CACHE_MAX_FALLBACK 128U
+#define CACHE_MAX_MAX (16*1024U)
+#define CACHE_MAX_MIN 64U
+
+static size_t cache_max(void) {
+        static size_t cached = -1;
+
+        if (cached == SIZE_MAX) {
+                uint64_t mem_total;
+                int r;
+
+                r = procfs_memory_get(&mem_total, NULL);
+                if (r < 0) {
+                        log_warning_errno(r, "Cannot query /proc/meminfo for MemTotal: %m");
+                        cached = CACHE_MAX_FALLBACK;
+                } else
+                        /* Cache entries are usually a few kB, but the process cmdline is controlled by the
+                         * user and can be up to _SC_ARG_MAX, usually 2MB. Let's say that approximately up to
+                         * 1/8th of memory may be used by the cache.
+                         *
+                         * In the common case, this formula gives 64 cache entries for each GB of RAM.
+                         */
+                        cached = CLAMP(mem_total / 8 / sc_arg_max(), CACHE_MAX_MIN, CACHE_MAX_MAX);
+        }
+
+        return cached;
+}
+
+static int client_context_compare(const void *a, const void *b) {
+        const ClientContext *x = a, *y = b;
+        int r;
+
+        r = CMP(x->timestamp, y->timestamp);
+        if (r != 0)
+                return r;
+
+        return CMP(x->pid, y->pid);
+}
+
+static int client_context_new(Server *s, pid_t pid, ClientContext **ret) {
+        _cleanup_free_ ClientContext *c = NULL;
+        int r;
+
+        assert(s);
+        assert(pid_is_valid(pid));
+        assert(ret);
+
+        r = prioq_ensure_allocated(&s->client_contexts_lru, client_context_compare);
+        if (r < 0)
+                return r;
+
+        c = new(ClientContext, 1);
+        if (!c)
+                return -ENOMEM;
+
+        *c = (ClientContext) {
+                .pid = pid,
+                .uid = UID_INVALID,
+                .gid = GID_INVALID,
+                .auditid = AUDIT_SESSION_INVALID,
+                .loginuid = UID_INVALID,
+                .owner_uid = UID_INVALID,
+                .lru_index = PRIOQ_IDX_NULL,
+                .timestamp = USEC_INFINITY,
+                .extra_fields_mtime = NSEC_INFINITY,
+                .log_level_max = -1,
+                .log_ratelimit_interval = s->ratelimit_interval,
+                .log_ratelimit_burst = s->ratelimit_burst,
+        };
+
+        r = hashmap_ensure_put(&s->client_contexts, NULL, PID_TO_PTR(pid), c);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(c);
+        return 0;
+}
+
+static void client_context_reset(Server *s, ClientContext *c) {
+        assert(s);
+        assert(c);
+
+        c->timestamp = USEC_INFINITY;
+
+        c->uid = UID_INVALID;
+        c->gid = GID_INVALID;
+
+        c->comm = mfree(c->comm);
+        c->exe = mfree(c->exe);
+        c->cmdline = mfree(c->cmdline);
+        c->capeff = mfree(c->capeff);
+
+        c->auditid = AUDIT_SESSION_INVALID;
+        c->loginuid = UID_INVALID;
+
+        c->cgroup = mfree(c->cgroup);
+        c->session = mfree(c->session);
+        c->owner_uid = UID_INVALID;
+        c->unit = mfree(c->unit);
+        c->user_unit = mfree(c->user_unit);
+        c->slice = mfree(c->slice);
+        c->user_slice = mfree(c->user_slice);
+
+        c->invocation_id = SD_ID128_NULL;
+
+        c->label = mfree(c->label);
+        c->label_size = 0;
+
+        c->extra_fields_iovec = mfree(c->extra_fields_iovec);
+        c->extra_fields_n_iovec = 0;
+        c->extra_fields_data = mfree(c->extra_fields_data);
+        c->extra_fields_mtime = NSEC_INFINITY;
+
+        c->log_level_max = -1;
+
+        c->log_ratelimit_interval = s->ratelimit_interval;
+        c->log_ratelimit_burst = s->ratelimit_burst;
+
+        c->log_filter_allowed_patterns = set_free_free(c->log_filter_allowed_patterns);
+        c->log_filter_denied_patterns = set_free_free(c->log_filter_denied_patterns);
+}
+
+static ClientContext* client_context_free(Server *s, ClientContext *c) {
+        assert(s);
+
+        if (!c)
+                return NULL;
+
+        assert_se(hashmap_remove(s->client_contexts, PID_TO_PTR(c->pid)) == c);
+
+        if (c->in_lru)
+                assert_se(prioq_remove(s->client_contexts_lru, c, &c->lru_index) >= 0);
+
+        client_context_reset(s, c);
+
+        return mfree(c);
+}
+
+static void client_context_read_uid_gid(ClientContext *c, const struct ucred *ucred) {
+        assert(c);
+        assert(pid_is_valid(c->pid));
+
+        /* The ucred data passed in is always the most current and accurate, if we have any. Use it. */
+        if (ucred && uid_is_valid(ucred->uid))
+                c->uid = ucred->uid;
+        else
+                (void) pid_get_uid(c->pid, &c->uid);
+
+        if (ucred && gid_is_valid(ucred->gid))
+                c->gid = ucred->gid;
+        else
+                (void) get_process_gid(c->pid, &c->gid);
+}
+
+static void client_context_read_basic(ClientContext *c) {
+        char *t;
+
+        assert(c);
+        assert(pid_is_valid(c->pid));
+
+        if (pid_get_comm(c->pid, &t) >= 0)
+                free_and_replace(c->comm, t);
+
+        if (get_process_exe(c->pid, &t) >= 0)
+                free_and_replace(c->exe, t);
+
+        if (pid_get_cmdline(c->pid, SIZE_MAX, PROCESS_CMDLINE_QUOTE, &t) >= 0)
+                free_and_replace(c->cmdline, t);
+
+        if (get_process_capeff(c->pid, &t) >= 0)
+                free_and_replace(c->capeff, t);
+}
+
+static int client_context_read_label(
+                ClientContext *c,
+                const char *label, size_t label_size) {
+
+        assert(c);
+        assert(pid_is_valid(c->pid));
+        assert(label_size == 0 || label);
+
+        if (label_size > 0) {
+                char *l;
+
+                /* If we got an SELinux label passed in it counts. */
+
+                l = newdup_suffix0(char, label, label_size);
+                if (!l)
+                        return -ENOMEM;
+
+                free_and_replace(c->label, l);
+                c->label_size = label_size;
+        }
+#if HAVE_SELINUX
+        else {
+                char *con;
+
+                /* If we got no SELinux label passed in, let's try to acquire one */
+
+                if (getpidcon(c->pid, &con) >= 0 && con) {
+                        free_and_replace(c->label, con);
+                        c->label_size = strlen(c->label);
+                }
+        }
+#endif
+
+        return 0;
+}
+
+static int client_context_read_cgroup(Server *s, ClientContext *c, const char *unit_id) {
+        _cleanup_free_ char *t = NULL;
+        int r;
+
+        assert(c);
+
+        /* Try to acquire the current cgroup path */
+        r = cg_pid_get_path_shifted(c->pid, s->cgroup_root, &t);
+        if (r < 0 || empty_or_root(t)) {
+                /* We use the unit ID passed in as fallback if we have nothing cached yet and cg_pid_get_path_shifted()
+                 * failed or process is running in a root cgroup. Zombie processes are automatically migrated to root cgroup
+                 * on cgroup v1 and we want to be able to map log messages from them too. */
+                if (unit_id && !c->unit) {
+                        c->unit = strdup(unit_id);
+                        if (c->unit)
+                                return 0;
+                }
+
+                return r;
+        }
+
+        (void) client_context_read_log_filter_patterns(c, t);
+
+        /* Let's shortcut this if the cgroup path didn't change */
+        if (streq_ptr(c->cgroup, t))
+                return 0;
+
+        free_and_replace(c->cgroup, t);
+
+        (void) cg_path_get_session(c->cgroup, &t);
+        free_and_replace(c->session, t);
+
+        if (cg_path_get_owner_uid(c->cgroup, &c->owner_uid) < 0)
+                c->owner_uid = UID_INVALID;
+
+        (void) cg_path_get_unit(c->cgroup, &t);
+        free_and_replace(c->unit, t);
+
+        (void) cg_path_get_user_unit(c->cgroup, &t);
+        free_and_replace(c->user_unit, t);
+
+        (void) cg_path_get_slice(c->cgroup, &t);
+        free_and_replace(c->slice, t);
+
+        (void) cg_path_get_user_slice(c->cgroup, &t);
+        free_and_replace(c->user_slice, t);
+
+        return 0;
+}
+
+static int client_context_read_invocation_id(
+                Server *s,
+                ClientContext *c) {
+
+        _cleanup_free_ char *p = NULL, *value = NULL;
+        int r;
+
+        assert(s);
+        assert(c);
+
+        /* Read the invocation ID of a unit off a unit.
+         * PID 1 stores it in a per-unit symlink in /run/systemd/units/
+         * User managers store it in a per-unit symlink under /run/user/<uid>/systemd/units/ */
+
+        if (!c->unit)
+                return 0;
+
+        if (c->user_unit) {
+                r = asprintf(&p, "/run/user/" UID_FMT "/systemd/units/invocation:%s", c->owner_uid, c->user_unit);
+                if (r < 0)
+                        return r;
+        } else {
+                p = strjoin("/run/systemd/units/invocation:", c->unit);
+                if (!p)
+                        return -ENOMEM;
+        }
+
+        r = readlink_malloc(p, &value);
+        if (r < 0)
+                return r;
+
+        return sd_id128_from_string(value, &c->invocation_id);
+}
+
+static int client_context_read_log_level_max(
+                Server *s,
+                ClientContext *c) {
+
+        _cleanup_free_ char *value = NULL;
+        const char *p;
+        int r, ll;
+
+        if (!c->unit)
+                return 0;
+
+        p = strjoina("/run/systemd/units/log-level-max:", c->unit);
+        r = readlink_malloc(p, &value);
+        if (r < 0)
+                return r;
+
+        ll = log_level_from_string(value);
+        if (ll < 0)
+                return ll;
+
+        c->log_level_max = ll;
+        return 0;
+}
+
+static int client_context_read_extra_fields(
+                Server *s,
+                ClientContext *c) {
+
+        _cleanup_free_ struct iovec *iovec = NULL;
+        size_t size = 0, n_iovec = 0, left;
+        _cleanup_free_ void *data = NULL;
+        _cleanup_fclose_ FILE *f = NULL;
+        struct stat st;
+        const char *p;
+        uint8_t *q;
+        int r;
+
+        if (!c->unit)
+                return 0;
+
+        p = strjoina("/run/systemd/units/log-extra-fields:", c->unit);
+
+        if (c->extra_fields_mtime != NSEC_INFINITY) {
+                if (stat(p, &st) < 0) {
+                        if (errno == ENOENT)
+                                return 0;
+
+                        return -errno;
+                }
+
+                if (timespec_load_nsec(&st.st_mtim) == c->extra_fields_mtime)
+                        return 0;
+        }
+
+        f = fopen(p, "re");
+        if (!f) {
+                if (errno == ENOENT)
+                        return 0;
+
+                return -errno;
+        }
+
+        if (fstat(fileno(f), &st) < 0) /* The file might have been replaced since the stat() above, let's get a new
+                                        * one, that matches the stuff we are reading */
+                return -errno;
+
+        r = read_full_stream(f, (char**) &data, &size);
+        if (r < 0)
+                return r;
+
+        q = data, left = size;
+        while (left > 0) {
+                uint8_t *field, *eq;
+                uint64_t v, n;
+
+                if (left < sizeof(uint64_t))
+                        return -EBADMSG;
+
+                v = unaligned_read_le64(q);
+                if (v < 2)
+                        return -EBADMSG;
+
+                n = sizeof(uint64_t) + v;
+                if (left < n)
+                        return -EBADMSG;
+
+                field = q + sizeof(uint64_t);
+
+                eq = memchr(field, '=', v);
+                if (!eq)
+                        return -EBADMSG;
+
+                if (!journal_field_valid((const char *) field, eq - field, false))
+                        return -EBADMSG;
+
+                if (!GREEDY_REALLOC(iovec, n_iovec+1))
+                        return -ENOMEM;
+
+                iovec[n_iovec++] = IOVEC_MAKE(field, v);
+
+                left -= n, q += n;
+        }
+
+        free(c->extra_fields_iovec);
+        free(c->extra_fields_data);
+
+        c->extra_fields_iovec = TAKE_PTR(iovec);
+        c->extra_fields_n_iovec = n_iovec;
+        c->extra_fields_data = TAKE_PTR(data);
+        c->extra_fields_mtime = timespec_load_nsec(&st.st_mtim);
+
+        return 0;
+}
+
+static int client_context_read_log_ratelimit_interval(ClientContext *c) {
+        _cleanup_free_ char *value = NULL;
+        const char *p;
+        int r;
+
+        assert(c);
+
+        if (!c->unit)
+                return 0;
+
+        p = strjoina("/run/systemd/units/log-rate-limit-interval:", c->unit);
+        r = readlink_malloc(p, &value);
+        if (r < 0)
+                return r;
+
+        return safe_atou64(value, &c->log_ratelimit_interval);
+}
+
+static int client_context_read_log_ratelimit_burst(ClientContext *c) {
+        _cleanup_free_ char *value = NULL;
+        const char *p;
+        int r;
+
+        assert(c);
+
+        if (!c->unit)
+                return 0;
+
+        p = strjoina("/run/systemd/units/log-rate-limit-burst:", c->unit);
+        r = readlink_malloc(p, &value);
+        if (r < 0)
+                return r;
+
+        return safe_atou(value, &c->log_ratelimit_burst);
+}
+
+static void client_context_really_refresh(
+                Server *s,
+                ClientContext *c,
+                const struct ucred *ucred,
+                const char *label, size_t label_size,
+                const char *unit_id,
+                usec_t timestamp) {
+
+        assert(s);
+        assert(c);
+        assert(pid_is_valid(c->pid));
+
+        if (timestamp == USEC_INFINITY)
+                timestamp = now(CLOCK_MONOTONIC);
+
+        client_context_read_uid_gid(c, ucred);
+        client_context_read_basic(c);
+        (void) client_context_read_label(c, label, label_size);
+
+        (void) audit_session_from_pid(c->pid, &c->auditid);
+        (void) audit_loginuid_from_pid(c->pid, &c->loginuid);
+
+        (void) client_context_read_cgroup(s, c, unit_id);
+        (void) client_context_read_invocation_id(s, c);
+        (void) client_context_read_log_level_max(s, c);
+        (void) client_context_read_extra_fields(s, c);
+        (void) client_context_read_log_ratelimit_interval(c);
+        (void) client_context_read_log_ratelimit_burst(c);
+
+        c->timestamp = timestamp;
+
+        if (c->in_lru) {
+                assert(c->n_ref == 0);
+                prioq_reshuffle(s->client_contexts_lru, c, &c->lru_index);
+        }
+}
+
+void client_context_maybe_refresh(
+                Server *s,
+                ClientContext *c,
+                const struct ucred *ucred,
+                const char *label, size_t label_size,
+                const char *unit_id,
+                usec_t timestamp) {
+
+        assert(s);
+        assert(c);
+
+        if (timestamp == USEC_INFINITY)
+                timestamp = now(CLOCK_MONOTONIC);
+
+        /* No cached data so far? Let's fill it up */
+        if (c->timestamp == USEC_INFINITY)
+                goto refresh;
+
+        /* If the data isn't pinned and if the cashed data is older than the upper limit, we flush it out
+         * entirely. This follows the logic that as long as an entry is pinned the PID reuse is unlikely. */
+        if (c->n_ref == 0 && c->timestamp + MAX_USEC < timestamp) {
+                client_context_reset(s, c);
+                goto refresh;
+        }
+
+        /* If the data is older than the lower limit, we refresh, but keep the old data for all we can't update */
+        if (c->timestamp + REFRESH_USEC < timestamp)
+                goto refresh;
+
+        /* If the data passed along doesn't match the cached data we also do a refresh */
+        if (ucred && uid_is_valid(ucred->uid) && c->uid != ucred->uid)
+                goto refresh;
+
+        if (ucred && gid_is_valid(ucred->gid) && c->gid != ucred->gid)
+                goto refresh;
+
+        if (label_size > 0 && (label_size != c->label_size || memcmp(label, c->label, label_size) != 0))
+                goto refresh;
+
+        return;
+
+refresh:
+        client_context_really_refresh(s, c, ucred, label, label_size, unit_id, timestamp);
+}
+
+static void client_context_try_shrink_to(Server *s, size_t limit) {
+        ClientContext *c;
+        usec_t t;
+
+        assert(s);
+
+        /* Flush any cache entries for PIDs that have already moved on. Don't do this
+         * too often, since it's a slow process. */
+        t = now(CLOCK_MONOTONIC);
+        if (s->last_cache_pid_flush + MAX_USEC < t) {
+                unsigned n = prioq_size(s->client_contexts_lru), idx = 0;
+
+                /* We do a number of iterations based on the initial size of the prioq.  When we remove an
+                 * item, a new item is moved into its places, and items to the right might be reshuffled.
+                 */
+                for (unsigned i = 0; i < n; i++) {
+                        c = prioq_peek_by_index(s->client_contexts_lru, idx);
+
+                        assert(c->n_ref == 0);
+
+                        if (pid_is_unwaited(c->pid) == 0)
+                                client_context_free(s, c);
+                        else
+                                idx ++;
+                }
+
+                s->last_cache_pid_flush = t;
+        }
+
+        /* Bring the number of cache entries below the indicated limit, so that we can create a new entry without
+         * breaching the limit. Note that we only flush out entries that aren't pinned here. This means the number of
+         * cache entries may very well grow beyond the limit, if all entries stored remain pinned. */
+
+        while (hashmap_size(s->client_contexts) > limit) {
+                c = prioq_pop(s->client_contexts_lru);
+                if (!c)
+                        break; /* All remaining entries are pinned, give up */
+
+                assert(c->in_lru);
+                assert(c->n_ref == 0);
+
+                c->in_lru = false;
+
+                client_context_free(s, c);
+        }
+}
+
+void client_context_flush_regular(Server *s) {
+        client_context_try_shrink_to(s, 0);
+}
+
+void client_context_flush_all(Server *s) {
+        assert(s);
+
+        /* Flush out all remaining entries. This assumes all references are already dropped. */
+
+        s->my_context = client_context_release(s, s->my_context);
+        s->pid1_context = client_context_release(s, s->pid1_context);
+
+        client_context_flush_regular(s);
+
+        assert(prioq_size(s->client_contexts_lru) == 0);
+        assert(hashmap_size(s->client_contexts) == 0);
+
+        s->client_contexts_lru = prioq_free(s->client_contexts_lru);
+        s->client_contexts = hashmap_free(s->client_contexts);
+}
+
+static int client_context_get_internal(
+                Server *s,
+                pid_t pid,
+                const struct ucred *ucred,
+                const char *label, size_t label_len,
+                const char *unit_id,
+                bool add_ref,
+                ClientContext **ret) {
+
+        ClientContext *c;
+        int r;
+
+        assert(s);
+        assert(ret);
+
+        if (!pid_is_valid(pid))
+                return -EINVAL;
+
+        c = hashmap_get(s->client_contexts, PID_TO_PTR(pid));
+        if (c) {
+
+                if (add_ref) {
+                        if (c->in_lru) {
+                                /* The entry wasn't pinned so far, let's remove it from the LRU list then */
+                                assert(c->n_ref == 0);
+                                assert_se(prioq_remove(s->client_contexts_lru, c, &c->lru_index) >= 0);
+                                c->in_lru = false;
+                        }
+
+                        c->n_ref++;
+                }
+
+                client_context_maybe_refresh(s, c, ucred, label, label_len, unit_id, USEC_INFINITY);
+
+                *ret = c;
+                return 0;
+        }
+
+        client_context_try_shrink_to(s, cache_max()-1);
+
+        r = client_context_new(s, pid, &c);
+        if (r < 0)
+                return r;
+
+        if (add_ref)
+                c->n_ref++;
+        else {
+                r = prioq_put(s->client_contexts_lru, c, &c->lru_index);
+                if (r < 0) {
+                        client_context_free(s, c);
+                        return r;
+                }
+
+                c->in_lru = true;
+        }
+
+        client_context_really_refresh(s, c, ucred, label, label_len, unit_id, USEC_INFINITY);
+
+        *ret = c;
+        return 0;
+}
+
+int client_context_get(
+                Server *s,
+                pid_t pid,
+                const struct ucred *ucred,
+                const char *label, size_t label_len,
+                const char *unit_id,
+                ClientContext **ret) {
+
+        return client_context_get_internal(s, pid, ucred, label, label_len, unit_id, false, ret);
+}
+
+int client_context_acquire(
+                Server *s,
+                pid_t pid,
+                const struct ucred *ucred,
+                const char *label, size_t label_len,
+                const char *unit_id,
+                ClientContext **ret) {
+
+        return client_context_get_internal(s, pid, ucred, label, label_len, unit_id, true, ret);
+};
+
+ClientContext *client_context_release(Server *s, ClientContext *c) {
+        assert(s);
+
+        if (!c)
+                return NULL;
+
+        assert(c->n_ref > 0);
+        assert(!c->in_lru);
+
+        c->n_ref--;
+        if (c->n_ref > 0)
+                return NULL;
+
+        /* The entry is not pinned anymore, let's add it to the LRU prioq if we can. If we can't we'll drop it
+         * right-away */
+
+        if (prioq_put(s->client_contexts_lru, c, &c->lru_index) < 0)
+                client_context_free(s, c);
+        else
+                c->in_lru = true;
+
+        return NULL;
+}
+
+void client_context_acquire_default(Server *s) {
+        int r;
+
+        assert(s);
+
+        /* Ensure that our own and PID1's contexts are always pinned. Our own context is particularly useful to
+         * generate driver messages. */
+
+        if (!s->my_context) {
+                struct ucred ucred = {
+                        .pid = getpid_cached(),
+                        .uid = getuid(),
+                        .gid = getgid(),
+                };
+
+                r = client_context_acquire(s, ucred.pid, &ucred, NULL, 0, NULL, &s->my_context);
+                if (r < 0)
+                        log_ratelimit_warning_errno(r, JOURNAL_LOG_RATELIMIT,
+                                                    "Failed to acquire our own context, ignoring: %m");
+        }
+
+        if (!s->namespace && !s->pid1_context) {
+                /* Acquire PID1's context, but only if we are in non-namespaced mode, since PID 1 is only
+                 * going to log to the non-namespaced journal instance. */
+
+                r = client_context_acquire(s, 1, NULL, NULL, 0, NULL, &s->pid1_context);
+                if (r < 0)
+                        log_ratelimit_warning_errno(r, JOURNAL_LOG_RATELIMIT,
+                                                    "Failed to acquire PID1's context, ignoring: %m");
+
+        }
+}