Adding upstream version 255.4.upstream/255.4

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

3 files changed, 1446 insertions, 0 deletions

diff --git a/src/libsystemd/sd-resolve/resolve-private.h b/src/libsystemd/sd-resolve/resolve-private.h
new file mode 100644
index 0000000..7a339f7
--- /dev/null
+++ b/src/libsystemd/sd-resolve/resolve-private.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-resolve.h"
+
+int resolve_getaddrinfo_with_destroy_callback(
+                sd_resolve *resolve, sd_resolve_query **q,
+                const char *node, const char *service, const struct addrinfo *hints,
+                sd_resolve_getaddrinfo_handler_t callback,
+                sd_resolve_destroy_t destroy_callback, void *userdata);
+int resolve_getnameinfo_with_destroy_callback(
+                sd_resolve *resolve, sd_resolve_query **q,
+                const struct sockaddr *sa, socklen_t salen, int flags, uint64_t get,
+                sd_resolve_getnameinfo_handler_t callback,
+                sd_resolve_destroy_t destroy_callback, void *userdata);
+
+#define resolve_getaddrinfo(resolve, ret_query, node, service, hints, callback, destroy_callback, userdata) \
+        ({                                                              \
+                int (*_callback_)(sd_resolve_query*, int, const struct addrinfo*, typeof(userdata)) = callback; \
+                void (*_destroy_)(typeof(userdata)) = destroy_callback; \
+                resolve_getaddrinfo_with_destroy_callback(              \
+                        resolve, ret_query,                             \
+                        node, service, hints,                           \
+                        (sd_resolve_getaddrinfo_handler_t) _callback_,  \
+                        (sd_resolve_destroy_t) _destroy_,               \
+                        userdata);                                      \
+        })
+
+#define resolve_getnameinfo(resolve, ret_query, sa, salen, flags, get, callback, destroy_callback, userdata) \
+        ({                                                              \
+                int (*_callback_)(sd_resolve_query*, int, const char*, const char*, typeof(userdata)) = callback; \
+                void (*_destroy_)(typeof(userdata)) = destroy_callback; \
+                resolve_getaddrinfo_with_destroy_callback(              \
+                        resolve, ret_query,                             \
+                        sa, salen, flags, get,                          \
+                        (sd_resolve_getnameinfo_handler_t) _callback_,  \
+                        (sd_resolve_destroy_t) _destroy_,               \
+                        userdata);                                      \
+        })
diff --git a/src/libsystemd/sd-resolve/sd-resolve.c b/src/libsystemd/sd-resolve/sd-resolve.c
new file mode 100644
index 0000000..2000f86
--- /dev/null
+++ b/src/libsystemd/sd-resolve/sd-resolve.c
@@ -0,0 +1,1296 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <poll.h>
+#include <pthread.h>
+#include <resolv.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#include "sd-resolve.h"
+
+#include "alloc-util.h"
+#include "dns-def.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "io-util.h"
+#include "iovec-util.h"
+#include "list.h"
+#include "memory-util.h"
+#include "missing_syscall.h"
+#include "missing_threads.h"
+#include "process-util.h"
+#include "resolve-private.h"
+#include "socket-util.h"
+
+#define WORKERS_MIN 1U
+#define WORKERS_MAX 16U
+#define QUERIES_MAX 256U
+#define BUFSIZE 10240U
+
+typedef enum {
+        REQUEST_ADDRINFO,
+        RESPONSE_ADDRINFO,
+        REQUEST_NAMEINFO,
+        RESPONSE_NAMEINFO,
+        REQUEST_TERMINATE,
+        RESPONSE_DIED
+} QueryType;
+
+enum {
+        REQUEST_RECV_FD,
+        REQUEST_SEND_FD,
+        RESPONSE_RECV_FD,
+        RESPONSE_SEND_FD,
+        _FD_MAX
+};
+
+struct sd_resolve {
+        unsigned n_ref;
+
+        bool dead:1;
+        pid_t original_pid;
+
+        int fds[_FD_MAX];
+
+        pthread_t workers[WORKERS_MAX];
+        unsigned n_valid_workers;
+
+        unsigned current_id;
+        sd_resolve_query* query_array[QUERIES_MAX];
+        unsigned n_queries, n_done, n_outstanding;
+
+        sd_event_source *event_source;
+        sd_event *event;
+
+        sd_resolve_query *current;
+
+        sd_resolve **default_resolve_ptr;
+        pid_t tid;
+
+        LIST_HEAD(sd_resolve_query, queries);
+};
+
+struct sd_resolve_query {
+        unsigned n_ref;
+
+        sd_resolve *resolve;
+
+        QueryType type:4;
+        bool done:1;
+        bool floating:1;
+        unsigned id;
+
+        int ret;
+        int _errno;
+        int _h_errno;
+        struct addrinfo *addrinfo;
+        char *serv, *host;
+
+        union {
+                sd_resolve_getaddrinfo_handler_t getaddrinfo_handler;
+                sd_resolve_getnameinfo_handler_t getnameinfo_handler;
+        };
+
+        void *userdata;
+        sd_resolve_destroy_t destroy_callback;
+
+        LIST_FIELDS(sd_resolve_query, queries);
+};
+
+typedef struct RHeader {
+        QueryType type;
+        unsigned id;
+        size_t length;
+} RHeader;
+
+typedef struct AddrInfoRequest {
+        struct RHeader header;
+        bool hints_valid;
+        int ai_flags;
+        int ai_family;
+        int ai_socktype;
+        int ai_protocol;
+        size_t node_len, service_len;
+} AddrInfoRequest;
+
+typedef struct AddrInfoResponse {
+        struct RHeader header;
+        int ret;
+        int _errno;
+        int _h_errno;
+        /* followed by addrinfo_serialization[] */
+} AddrInfoResponse;
+
+typedef struct AddrInfoSerialization {
+        int ai_flags;
+        int ai_family;
+        int ai_socktype;
+        int ai_protocol;
+        size_t ai_addrlen;
+        size_t canonname_len;
+        /* Followed by ai_addr amd ai_canonname with variable lengths */
+} AddrInfoSerialization;
+
+typedef struct NameInfoRequest {
+        struct RHeader header;
+        int flags;
+        socklen_t sockaddr_len;
+        bool gethost:1, getserv:1;
+} NameInfoRequest;
+
+typedef struct NameInfoResponse {
+        struct RHeader header;
+        size_t hostlen, servlen;
+        int ret;
+        int _errno;
+        int _h_errno;
+} NameInfoResponse;
+
+typedef union Packet {
+        RHeader rheader;
+        AddrInfoRequest addrinfo_request;
+        AddrInfoResponse addrinfo_response;
+        NameInfoRequest nameinfo_request;
+        NameInfoResponse nameinfo_response;
+} Packet;
+
+static int getaddrinfo_done(sd_resolve_query* q);
+static int getnameinfo_done(sd_resolve_query *q);
+
+static void resolve_query_disconnect(sd_resolve_query *q);
+
+#define RESOLVE_DONT_DESTROY(resolve) \
+        _cleanup_(sd_resolve_unrefp) _unused_ sd_resolve *_dont_destroy_##resolve = sd_resolve_ref(resolve)
+
+static void query_assign_errno(sd_resolve_query *q, int ret, int error, int h_error) {
+        assert(q);
+
+        q->ret = ret;
+        q->_errno = abs(error);
+        q->_h_errno = h_error;
+}
+
+static int send_died(int out_fd) {
+        RHeader rh = {
+                .type = RESPONSE_DIED,
+                .length = sizeof(RHeader),
+        };
+
+        assert(out_fd >= 0);
+
+        if (send(out_fd, &rh, rh.length, MSG_NOSIGNAL) < 0)
+                return -errno;
+
+        return 0;
+}
+
+static void *serialize_addrinfo(void *p, const struct addrinfo *ai, size_t *length, size_t maxlength) {
+        AddrInfoSerialization s;
+        size_t cnl, l;
+
+        assert(p);
+        assert(ai);
+        assert(length);
+        assert(*length <= maxlength);
+
+        cnl = ai->ai_canonname ? strlen(ai->ai_canonname)+1 : 0;
+        l = sizeof(AddrInfoSerialization) + ai->ai_addrlen + cnl;
+
+        if (*length + l > maxlength)
+                return NULL;
+
+        s = (AddrInfoSerialization) {
+                .ai_flags = ai->ai_flags,
+                .ai_family = ai->ai_family,
+                .ai_socktype = ai->ai_socktype,
+                .ai_protocol = ai->ai_protocol,
+                .ai_addrlen = ai->ai_addrlen,
+                .canonname_len = cnl,
+        };
+
+        memcpy((uint8_t*) p, &s, sizeof(AddrInfoSerialization));
+        memcpy((uint8_t*) p + sizeof(AddrInfoSerialization), ai->ai_addr, ai->ai_addrlen);
+        memcpy_safe((char*) p + sizeof(AddrInfoSerialization) + ai->ai_addrlen,
+                    ai->ai_canonname, cnl);
+
+        *length += l;
+        return (uint8_t*) p + l;
+}
+
+static int send_addrinfo_reply(
+                int out_fd,
+                unsigned id,
+                int ret,
+                struct addrinfo *ai,
+                int _errno,
+                int _h_errno) {
+
+        AddrInfoResponse resp = {};
+        union {
+                AddrInfoSerialization ais;
+                uint8_t space[BUFSIZE];
+        } buffer;
+        struct iovec iov[2];
+        struct msghdr mh;
+
+        assert(out_fd >= 0);
+
+        resp = (AddrInfoResponse) {
+                .header.type = RESPONSE_ADDRINFO,
+                .header.id = id,
+                .header.length = sizeof(AddrInfoResponse),
+                .ret = ret,
+                ._errno = _errno,
+                ._h_errno = _h_errno,
+        };
+
+        msan_unpoison(&resp, sizeof(resp));
+
+        if (ret == 0 && ai) {
+                void *p = &buffer;
+                struct addrinfo *k;
+
+                for (k = ai; k; k = k->ai_next) {
+                        p = serialize_addrinfo(p, k, &resp.header.length, (uint8_t*) &buffer + BUFSIZE - (uint8_t*) p);
+                        if (!p) {
+                                freeaddrinfo(ai);
+                                return -ENOBUFS;
+                        }
+                }
+        }
+
+        if (ai)
+                freeaddrinfo(ai);
+
+        iov[0] = IOVEC_MAKE(&resp, sizeof(AddrInfoResponse));
+        iov[1] = IOVEC_MAKE(&buffer, resp.header.length - sizeof(AddrInfoResponse));
+
+        mh = (struct msghdr) {
+                .msg_iov = iov,
+                .msg_iovlen = ELEMENTSOF(iov)
+        };
+
+        if (sendmsg(out_fd, &mh, MSG_NOSIGNAL) < 0)
+                return -errno;
+
+        return 0;
+}
+
+static int send_nameinfo_reply(
+                int out_fd,
+                unsigned id,
+                int ret,
+                const char *host,
+                const char *serv,
+                int _errno,
+                int _h_errno) {
+
+        NameInfoResponse resp = {};
+        struct iovec iov[3];
+        struct msghdr mh;
+        size_t hl, sl;
+
+        assert(out_fd >= 0);
+
+        sl = serv ? strlen(serv)+1 : 0;
+        hl = host ? strlen(host)+1 : 0;
+
+        resp = (NameInfoResponse) {
+                .header.type = RESPONSE_NAMEINFO,
+                .header.id = id,
+                .header.length = sizeof(NameInfoResponse) + hl + sl,
+                .hostlen = hl,
+                .servlen = sl,
+                .ret = ret,
+                ._errno = _errno,
+                ._h_errno = _h_errno,
+        };
+
+        msan_unpoison(&resp, sizeof(resp));
+
+        iov[0] = IOVEC_MAKE(&resp, sizeof(NameInfoResponse));
+        iov[1] = IOVEC_MAKE((void*) host, hl);
+        iov[2] = IOVEC_MAKE((void*) serv, sl);
+
+        mh = (struct msghdr) {
+                .msg_iov = iov,
+                .msg_iovlen = ELEMENTSOF(iov)
+        };
+
+        if (sendmsg(out_fd, &mh, MSG_NOSIGNAL) < 0)
+                return -errno;
+
+        return 0;
+}
+
+static int handle_request(int out_fd, const Packet *packet, size_t length) {
+        const RHeader *req;
+
+        assert(out_fd >= 0);
+        assert(packet);
+
+        req = &packet->rheader;
+
+        assert_return(length >= sizeof(RHeader), -EIO);
+        assert_return(length == req->length, -EIO);
+
+        switch (req->type) {
+
+        case REQUEST_ADDRINFO: {
+               const AddrInfoRequest *ai_req = &packet->addrinfo_request;
+               struct addrinfo hints, *result = NULL;
+               const char *node, *service;
+               int ret;
+
+               assert_return(length >= sizeof(AddrInfoRequest), -EBADMSG);
+               assert_return(length == sizeof(AddrInfoRequest) + ai_req->node_len + ai_req->service_len, -EBADMSG);
+
+               hints = (struct addrinfo) {
+                       .ai_flags = ai_req->ai_flags,
+                       .ai_family = ai_req->ai_family,
+                       .ai_socktype = ai_req->ai_socktype,
+                       .ai_protocol = ai_req->ai_protocol,
+               };
+
+               msan_unpoison(&hints, sizeof(hints));
+
+               node = ai_req->node_len ? (const char*) ai_req + sizeof(AddrInfoRequest) : NULL;
+               service = ai_req->service_len ? (const char*) ai_req + sizeof(AddrInfoRequest) + ai_req->node_len : NULL;
+
+               ret = getaddrinfo(node, service,
+                                 ai_req->hints_valid ? &hints : NULL,
+                                 &result);
+
+               /* send_addrinfo_reply() frees result */
+               return send_addrinfo_reply(out_fd, req->id, ret, result, errno, h_errno);
+        }
+
+        case REQUEST_NAMEINFO: {
+               const NameInfoRequest *ni_req = &packet->nameinfo_request;
+               char hostbuf[NI_MAXHOST], servbuf[NI_MAXSERV];
+               union sockaddr_union sa;
+               int ret;
+
+               assert_return(length >= sizeof(NameInfoRequest), -EBADMSG);
+               assert_return(length == sizeof(NameInfoRequest) + ni_req->sockaddr_len, -EBADMSG);
+               assert_return(ni_req->sockaddr_len <= sizeof(sa), -EBADMSG);
+
+               memcpy(&sa, (const uint8_t *) ni_req + sizeof(NameInfoRequest), ni_req->sockaddr_len);
+
+               ret = getnameinfo(&sa.sa, ni_req->sockaddr_len,
+                                 ni_req->gethost ? hostbuf : NULL, ni_req->gethost ? sizeof(hostbuf) : 0,
+                                 ni_req->getserv ? servbuf : NULL, ni_req->getserv ? sizeof(servbuf) : 0,
+                                 ni_req->flags);
+
+               return send_nameinfo_reply(out_fd, req->id, ret,
+                                          ret == 0 && ni_req->gethost ? hostbuf : NULL,
+                                          ret == 0 && ni_req->getserv ? servbuf : NULL,
+                                          errno, h_errno);
+        }
+
+        case REQUEST_TERMINATE:
+                 /* Quit */
+                 return -ECONNRESET;
+
+        default:
+                assert_not_reached();
+        }
+
+        return 0;
+}
+
+static void* thread_worker(void *p) {
+        sd_resolve *resolve = p;
+
+        /* Assign a pretty name to this thread */
+        (void) pthread_setname_np(pthread_self(), "sd-resolve");
+
+        while (!resolve->dead) {
+                union {
+                        Packet packet;
+                        uint8_t space[BUFSIZE];
+                } buf;
+                ssize_t length;
+
+                length = recv(resolve->fds[REQUEST_RECV_FD], &buf, sizeof buf, 0);
+                if (length < 0) {
+                        if (ERRNO_IS_TRANSIENT(errno))
+                                continue;
+
+                        break;
+                }
+                if (length == 0)
+                        break;
+
+                if (handle_request(resolve->fds[RESPONSE_SEND_FD], &buf.packet, (size_t) length) < 0)
+                        break;
+        }
+
+        send_died(resolve->fds[RESPONSE_SEND_FD]);
+
+        return NULL;
+}
+
+static int start_threads(sd_resolve *resolve, unsigned extra) {
+        sigset_t ss, saved_ss;
+        unsigned n;
+        int r, k;
+
+        assert_se(sigfillset(&ss) >= 0);
+
+        /* No signals in forked off threads please. We set the mask before forking, so that the threads never exist
+         * with a different mask than a fully blocked one */
+        r = pthread_sigmask(SIG_BLOCK, &ss, &saved_ss);
+        if (r > 0)
+                return -r;
+
+        n = resolve->n_outstanding + extra;
+        n = CLAMP(n, WORKERS_MIN, WORKERS_MAX);
+
+        while (resolve->n_valid_workers < n) {
+                r = pthread_create(&resolve->workers[resolve->n_valid_workers], NULL, thread_worker, resolve);
+                if (r > 0) {
+                        r = -r;
+                        goto finish;
+                }
+
+                resolve->n_valid_workers++;
+        }
+
+        r = 0;
+
+finish:
+        k = pthread_sigmask(SIG_SETMASK, &saved_ss, NULL);
+        if (k > 0 && r >= 0)
+                r = -k;
+
+        return r;
+}
+
+static bool resolve_pid_changed(sd_resolve *r) {
+        assert(r);
+
+        /* We don't support people creating a resolver and keeping it
+         * around after fork(). Let's complain. */
+
+        return r->original_pid != getpid_cached();
+}
+
+int sd_resolve_new(sd_resolve **ret) {
+        _cleanup_(sd_resolve_unrefp) sd_resolve *resolve = NULL;
+        int i;
+
+        assert_return(ret, -EINVAL);
+
+        resolve = new0(sd_resolve, 1);
+        if (!resolve)
+                return -ENOMEM;
+
+        resolve->n_ref = 1;
+        resolve->original_pid = getpid_cached();
+
+        for (i = 0; i < _FD_MAX; i++)
+                resolve->fds[i] = -EBADF;
+
+        if (socketpair(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0, resolve->fds + REQUEST_RECV_FD) < 0)
+                return -errno;
+
+        if (socketpair(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0, resolve->fds + RESPONSE_RECV_FD) < 0)
+                return -errno;
+
+        for (i = 0; i < _FD_MAX; i++)
+                resolve->fds[i] = fd_move_above_stdio(resolve->fds[i]);
+
+        (void) fd_inc_sndbuf(resolve->fds[REQUEST_SEND_FD], QUERIES_MAX * BUFSIZE);
+        (void) fd_increase_rxbuf(resolve->fds[REQUEST_RECV_FD], QUERIES_MAX * BUFSIZE);
+        (void) fd_inc_sndbuf(resolve->fds[RESPONSE_SEND_FD], QUERIES_MAX * BUFSIZE);
+        (void) fd_increase_rxbuf(resolve->fds[RESPONSE_RECV_FD], QUERIES_MAX * BUFSIZE);
+
+        (void) fd_nonblock(resolve->fds[RESPONSE_RECV_FD], true);
+
+        *ret = TAKE_PTR(resolve);
+        return 0;
+}
+
+int sd_resolve_default(sd_resolve **ret) {
+        static thread_local sd_resolve *default_resolve = NULL;
+        sd_resolve *e = NULL;
+        int r;
+
+        if (!ret)
+                return !!default_resolve;
+
+        if (default_resolve) {
+                *ret = sd_resolve_ref(default_resolve);
+                return 0;
+        }
+
+        r = sd_resolve_new(&e);
+        if (r < 0)
+                return r;
+
+        e->default_resolve_ptr = &default_resolve;
+        e->tid = gettid();
+        default_resolve = e;
+
+        *ret = e;
+        return 1;
+}
+
+int sd_resolve_get_tid(sd_resolve *resolve, pid_t *tid) {
+        assert_return(resolve, -EINVAL);
+        assert_return(tid, -EINVAL);
+        assert_return(!resolve_pid_changed(resolve), -ECHILD);
+
+        if (resolve->tid != 0) {
+                *tid = resolve->tid;
+                return 0;
+        }
+
+        if (resolve->event)
+                return sd_event_get_tid(resolve->event, tid);
+
+        return -ENXIO;
+}
+
+static sd_resolve *resolve_free(sd_resolve *resolve) {
+        PROTECT_ERRNO;
+        sd_resolve_query *q;
+        unsigned i;
+
+        assert(resolve);
+
+        while ((q = resolve->queries)) {
+                assert(q->floating);
+                resolve_query_disconnect(q);
+                sd_resolve_query_unref(q);
+        }
+
+        if (resolve->default_resolve_ptr)
+                *(resolve->default_resolve_ptr) = NULL;
+
+        resolve->dead = true;
+
+        sd_resolve_detach_event(resolve);
+
+        if (resolve->fds[REQUEST_SEND_FD] >= 0) {
+
+                RHeader req = {
+                        .type = REQUEST_TERMINATE,
+                        .length = sizeof req,
+                };
+
+                /* Send one termination packet for each worker */
+                for (i = 0; i < resolve->n_valid_workers; i++)
+                        (void) send(resolve->fds[REQUEST_SEND_FD], &req, req.length, MSG_NOSIGNAL);
+        }
+
+        /* Now terminate them and wait until they are gone.
+           If we get an error than most likely the thread already exited. */
+        for (i = 0; i < resolve->n_valid_workers; i++)
+                (void) pthread_join(resolve->workers[i], NULL);
+
+        /* Close all communication channels */
+        close_many(resolve->fds, _FD_MAX);
+
+        return mfree(resolve);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_resolve, sd_resolve, resolve_free);
+
+int sd_resolve_get_fd(sd_resolve *resolve) {
+        assert_return(resolve, -EINVAL);
+        assert_return(!resolve_pid_changed(resolve), -ECHILD);
+
+        return resolve->fds[RESPONSE_RECV_FD];
+}
+
+int sd_resolve_get_events(sd_resolve *resolve) {
+        assert_return(resolve, -EINVAL);
+        assert_return(!resolve_pid_changed(resolve), -ECHILD);
+
+        return resolve->n_queries > resolve->n_done ? POLLIN : 0;
+}
+
+int sd_resolve_get_timeout(sd_resolve *resolve, uint64_t *usec) {
+        assert_return(resolve, -EINVAL);
+        assert_return(usec, -EINVAL);
+        assert_return(!resolve_pid_changed(resolve), -ECHILD);
+
+        *usec = UINT64_MAX;
+        return 0;
+}
+
+static sd_resolve_query *lookup_query(sd_resolve *resolve, unsigned id) {
+        sd_resolve_query *q;
+
+        assert(resolve);
+
+        q = resolve->query_array[id % QUERIES_MAX];
+        if (q)
+                if (q->id == id)
+                        return q;
+
+        return NULL;
+}
+
+static int complete_query(sd_resolve *resolve, sd_resolve_query *q) {
+        int r;
+
+        assert(q);
+        assert(!q->done);
+        assert(q->resolve == resolve);
+
+        q->done = true;
+        resolve->n_done++;
+
+        resolve->current = sd_resolve_query_ref(q);
+
+        switch (q->type) {
+
+        case REQUEST_ADDRINFO:
+                r = getaddrinfo_done(q);
+                break;
+
+        case REQUEST_NAMEINFO:
+                r = getnameinfo_done(q);
+                break;
+
+        default:
+                assert_not_reached();
+        }
+
+        resolve->current = NULL;
+
+        if (q->floating) {
+                resolve_query_disconnect(q);
+                sd_resolve_query_unref(q);
+        }
+
+        sd_resolve_query_unref(q);
+
+        return r;
+}
+
+static int unserialize_addrinfo(const void **p, size_t *length, struct addrinfo **ret_ai) {
+        AddrInfoSerialization s;
+        struct addrinfo *ai;
+        size_t l;
+
+        assert(p);
+        assert(*p);
+        assert(ret_ai);
+        assert(length);
+
+        if (*length < sizeof(AddrInfoSerialization))
+                return -EBADMSG;
+
+        memcpy(&s, *p, sizeof(s));
+
+        l = sizeof(AddrInfoSerialization) + s.ai_addrlen + s.canonname_len;
+        if (*length < l)
+                return -EBADMSG;
+
+        ai = new(struct addrinfo, 1);
+        if (!ai)
+                return -ENOMEM;
+
+        *ai = (struct addrinfo) {
+                .ai_flags = s.ai_flags,
+                .ai_family = s.ai_family,
+                .ai_socktype = s.ai_socktype,
+                .ai_protocol = s.ai_protocol,
+                .ai_addrlen = s.ai_addrlen,
+        };
+
+        if (s.ai_addrlen > 0) {
+                ai->ai_addr = memdup((const uint8_t*) *p + sizeof(AddrInfoSerialization), s.ai_addrlen);
+                if (!ai->ai_addr) {
+                        free(ai);
+                        return -ENOMEM;
+                }
+        }
+
+        if (s.canonname_len > 0) {
+                ai->ai_canonname = memdup((const uint8_t*) *p + sizeof(AddrInfoSerialization) + s.ai_addrlen, s.canonname_len);
+                if (!ai->ai_canonname) {
+                        free(ai->ai_addr);
+                        free(ai);
+                        return -ENOMEM;
+                }
+        }
+
+        *length -= l;
+        *ret_ai = ai;
+        *p = ((const uint8_t*) *p) + l;
+
+        return 0;
+}
+
+static int handle_response(sd_resolve *resolve, const Packet *packet, size_t length) {
+        const RHeader *resp;
+        sd_resolve_query *q;
+        int r;
+
+        assert(resolve);
+        assert(packet);
+
+        resp = &packet->rheader;
+        assert_return(length >= sizeof(RHeader), -EIO);
+        assert_return(length == resp->length, -EIO);
+
+        if (resp->type == RESPONSE_DIED) {
+                resolve->dead = true;
+                return 0;
+        }
+
+        assert(resolve->n_outstanding > 0);
+        resolve->n_outstanding--;
+
+        q = lookup_query(resolve, resp->id);
+        if (!q)
+                return 0;
+
+        switch (resp->type) {
+
+        case RESPONSE_ADDRINFO: {
+                const AddrInfoResponse *ai_resp = &packet->addrinfo_response;
+                const void *p;
+                size_t l;
+                struct addrinfo *prev = NULL;
+
+                assert_return(length >= sizeof(AddrInfoResponse), -EBADMSG);
+                assert_return(q->type == REQUEST_ADDRINFO, -EBADMSG);
+
+                query_assign_errno(q, ai_resp->ret, ai_resp->_errno, ai_resp->_h_errno);
+
+                l = length - sizeof(AddrInfoResponse);
+                p = (const uint8_t*) resp + sizeof(AddrInfoResponse);
+
+                while (l > 0 && p) {
+                        struct addrinfo *ai = NULL;
+
+                        r = unserialize_addrinfo(&p, &l, &ai);
+                        if (r < 0) {
+                                query_assign_errno(q, EAI_SYSTEM, r, 0);
+                                freeaddrinfo(q->addrinfo);
+                                q->addrinfo = NULL;
+                                break;
+                        }
+
+                        if (prev)
+                                prev->ai_next = ai;
+                        else
+                                q->addrinfo = ai;
+
+                        prev = ai;
+                }
+
+                return complete_query(resolve, q);
+        }
+
+        case RESPONSE_NAMEINFO: {
+                const NameInfoResponse *ni_resp = &packet->nameinfo_response;
+
+                assert_return(length >= sizeof(NameInfoResponse), -EBADMSG);
+                assert_return(q->type == REQUEST_NAMEINFO, -EBADMSG);
+
+                if (ni_resp->hostlen > DNS_HOSTNAME_MAX ||
+                    ni_resp->servlen > DNS_HOSTNAME_MAX ||
+                    sizeof(NameInfoResponse) + ni_resp->hostlen + ni_resp->servlen > length)
+                        query_assign_errno(q, EAI_SYSTEM, EIO, 0);
+                else {
+                        query_assign_errno(q, ni_resp->ret, ni_resp->_errno, ni_resp->_h_errno);
+
+                        if (ni_resp->hostlen > 0) {
+                                q->host = strndup((const char*) ni_resp + sizeof(NameInfoResponse),
+                                                  ni_resp->hostlen-1);
+                                if (!q->host)
+                                        query_assign_errno(q, EAI_MEMORY, ENOMEM, 0);
+                        }
+
+                        if (ni_resp->servlen > 0) {
+                                q->serv = strndup((const char*) ni_resp + sizeof(NameInfoResponse) + ni_resp->hostlen,
+                                                  ni_resp->servlen-1);
+                                if (!q->serv)
+                                        query_assign_errno(q, EAI_MEMORY, ENOMEM, 0);
+                        }
+                }
+
+                return complete_query(resolve, q);
+        }
+
+        default:
+                return 0;
+        }
+}
+
+int sd_resolve_process(sd_resolve *resolve) {
+        RESOLVE_DONT_DESTROY(resolve);
+
+        union {
+                Packet packet;
+                uint8_t space[BUFSIZE];
+        } buf;
+        ssize_t l;
+        int r;
+
+        assert_return(resolve, -EINVAL);
+        assert_return(!resolve_pid_changed(resolve), -ECHILD);
+
+        /* We don't allow recursively invoking sd_resolve_process(). */
+        assert_return(!resolve->current, -EBUSY);
+
+        l = recv(resolve->fds[RESPONSE_RECV_FD], &buf, sizeof buf, 0);
+        if (l < 0) {
+                if (ERRNO_IS_TRANSIENT(errno))
+                        return 0;
+
+                return -errno;
+        }
+        if (l == 0)
+                return -ECONNREFUSED;
+
+        r = handle_response(resolve, &buf.packet, (size_t) l);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+int sd_resolve_wait(sd_resolve *resolve, uint64_t timeout_usec) {
+        int r;
+
+        assert_return(resolve, -EINVAL);
+        assert_return(!resolve_pid_changed(resolve), -ECHILD);
+
+        if (resolve->n_done >= resolve->n_queries)
+                return 0;
+
+        do {
+                r = fd_wait_for_event(resolve->fds[RESPONSE_RECV_FD], POLLIN, timeout_usec);
+        } while (r == -EINTR);
+
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ETIMEDOUT;
+
+        return sd_resolve_process(resolve);
+}
+
+static int alloc_query(sd_resolve *resolve, bool floating, sd_resolve_query **_q) {
+        sd_resolve_query *q;
+        int r;
+
+        assert(resolve);
+        assert(_q);
+
+        if (resolve->n_queries >= QUERIES_MAX)
+                return -ENOBUFS;
+
+        r = start_threads(resolve, 1);
+        if (r < 0)
+                return r;
+
+        while (resolve->query_array[resolve->current_id % QUERIES_MAX])
+                resolve->current_id++;
+
+        q = resolve->query_array[resolve->current_id % QUERIES_MAX] = new0(sd_resolve_query, 1);
+        if (!q)
+                return -ENOMEM;
+
+        q->n_ref = 1;
+        q->resolve = resolve;
+        q->floating = floating;
+        q->id = resolve->current_id++;
+
+        if (!floating)
+                sd_resolve_ref(resolve);
+
+        LIST_PREPEND(queries, resolve->queries, q);
+        resolve->n_queries++;
+
+        *_q = q;
+        return 0;
+}
+
+int resolve_getaddrinfo_with_destroy_callback(
+                sd_resolve *resolve,
+                sd_resolve_query **ret_query,
+                const char *node, const char *service,
+                const struct addrinfo *hints,
+                sd_resolve_getaddrinfo_handler_t callback,
+                sd_resolve_destroy_t destroy_callback,
+                void *userdata) {
+
+        _cleanup_(sd_resolve_query_unrefp) sd_resolve_query *q = NULL;
+        size_t node_len, service_len;
+        AddrInfoRequest req = {};
+        struct iovec iov[3];
+        struct msghdr mh = {};
+        int r;
+
+        assert_return(resolve, -EINVAL);
+        assert_return(node || service, -EINVAL);
+        assert_return(callback, -EINVAL);
+        assert_return(!resolve_pid_changed(resolve), -ECHILD);
+
+        r = alloc_query(resolve, !ret_query, &q);
+        if (r < 0)
+                return r;
+
+        q->type = REQUEST_ADDRINFO;
+        q->getaddrinfo_handler = callback;
+        q->userdata = userdata;
+
+        node_len = node ? strlen(node) + 1 : 0;
+        service_len = service ? strlen(service) + 1 : 0;
+
+        req = (AddrInfoRequest) {
+                .node_len = node_len,
+                .service_len = service_len,
+
+                .header.id = q->id,
+                .header.type = REQUEST_ADDRINFO,
+                .header.length = sizeof(AddrInfoRequest) + node_len + service_len,
+
+                .hints_valid = hints,
+                .ai_flags = hints ? hints->ai_flags : 0,
+                .ai_family = hints ? hints->ai_family : 0,
+                .ai_socktype = hints ? hints->ai_socktype : 0,
+                .ai_protocol = hints ? hints->ai_protocol : 0,
+        };
+
+        msan_unpoison(&req, sizeof(req));
+
+        iov[mh.msg_iovlen++] = IOVEC_MAKE(&req, sizeof(AddrInfoRequest));
+        if (node)
+                iov[mh.msg_iovlen++] = IOVEC_MAKE((void*) node, req.node_len);
+        if (service)
+                iov[mh.msg_iovlen++] = IOVEC_MAKE((void*) service, req.service_len);
+        mh.msg_iov = iov;
+
+        if (sendmsg(resolve->fds[REQUEST_SEND_FD], &mh, MSG_NOSIGNAL) < 0)
+                return -errno;
+
+        resolve->n_outstanding++;
+        q->destroy_callback = destroy_callback;
+
+        if (ret_query)
+                *ret_query = q;
+
+        TAKE_PTR(q);
+
+        return 0;
+}
+
+int sd_resolve_getaddrinfo(
+                sd_resolve *resolve,
+                sd_resolve_query **ret_query,
+                const char *node, const char *service,
+                const struct addrinfo *hints,
+                sd_resolve_getaddrinfo_handler_t callback,
+                void *userdata) {
+
+        return resolve_getaddrinfo_with_destroy_callback(resolve, ret_query, node, service, hints, callback, NULL, userdata);
+}
+
+static int getaddrinfo_done(sd_resolve_query* q) {
+        assert(q);
+        assert(q->done);
+        assert(q->getaddrinfo_handler);
+
+        errno = q->_errno;
+        h_errno = q->_h_errno;
+
+        return q->getaddrinfo_handler(q, q->ret, q->addrinfo, q->userdata);
+}
+
+int resolve_getnameinfo_with_destroy_callback(
+                sd_resolve *resolve,
+                sd_resolve_query **ret_query,
+                const struct sockaddr *sa, socklen_t salen,
+                int flags,
+                uint64_t get,
+                sd_resolve_getnameinfo_handler_t callback,
+                sd_resolve_destroy_t destroy_callback,
+                void *userdata) {
+
+        _cleanup_(sd_resolve_query_unrefp) sd_resolve_query *q = NULL;
+        NameInfoRequest req = {};
+        struct iovec iov[2];
+        struct msghdr mh;
+        int r;
+
+        assert_return(resolve, -EINVAL);
+        assert_return(sa, -EINVAL);
+        assert_return(salen >= sizeof(struct sockaddr), -EINVAL);
+        assert_return(salen <= sizeof(union sockaddr_union), -EINVAL);
+        assert_return((get & ~SD_RESOLVE_GET_BOTH) == 0, -EINVAL);
+        assert_return(callback, -EINVAL);
+        assert_return(!resolve_pid_changed(resolve), -ECHILD);
+
+        r = alloc_query(resolve, !ret_query, &q);
+        if (r < 0)
+                return r;
+
+        q->type = REQUEST_NAMEINFO;
+        q->getnameinfo_handler = callback;
+        q->userdata = userdata;
+
+        req = (NameInfoRequest) {
+                .header.id = q->id,
+                .header.type = REQUEST_NAMEINFO,
+                .header.length = sizeof(NameInfoRequest) + salen,
+
+                .flags = flags,
+                .sockaddr_len = salen,
+                .gethost = !!(get & SD_RESOLVE_GET_HOST),
+                .getserv = !!(get & SD_RESOLVE_GET_SERVICE),
+        };
+
+        msan_unpoison(&req, sizeof(req));
+
+        iov[0] = IOVEC_MAKE(&req, sizeof(NameInfoRequest));
+        iov[1] = IOVEC_MAKE((void*) sa, salen);
+
+        mh = (struct msghdr) {
+                .msg_iov = iov,
+                .msg_iovlen = ELEMENTSOF(iov)
+        };
+
+        if (sendmsg(resolve->fds[REQUEST_SEND_FD], &mh, MSG_NOSIGNAL) < 0)
+                return -errno;
+
+        resolve->n_outstanding++;
+        q->destroy_callback = destroy_callback;
+
+        if (ret_query)
+                *ret_query = q;
+
+        TAKE_PTR(q);
+
+        return 0;
+}
+
+int sd_resolve_getnameinfo(
+                sd_resolve *resolve,
+                sd_resolve_query **ret_query,
+                const struct sockaddr *sa, socklen_t salen,
+                int flags,
+                uint64_t get,
+                sd_resolve_getnameinfo_handler_t callback,
+                void *userdata) {
+
+        return resolve_getnameinfo_with_destroy_callback(resolve, ret_query, sa, salen, flags, get, callback, NULL, userdata);
+}
+
+static int getnameinfo_done(sd_resolve_query *q) {
+
+        assert(q);
+        assert(q->done);
+        assert(q->getnameinfo_handler);
+
+        errno = q->_errno;
+        h_errno = q->_h_errno;
+
+        return q->getnameinfo_handler(q, q->ret, q->host, q->serv, q->userdata);
+}
+
+static void resolve_freeaddrinfo(struct addrinfo *ai) {
+        while (ai) {
+                struct addrinfo *next = ai->ai_next;
+
+                free(ai->ai_addr);
+                free(ai->ai_canonname);
+                free_and_replace(ai, next);
+        }
+}
+
+static void resolve_query_disconnect(sd_resolve_query *q) {
+        sd_resolve *resolve;
+        unsigned i;
+
+        assert(q);
+
+        if (!q->resolve)
+                return;
+
+        resolve = q->resolve;
+        assert(resolve->n_queries > 0);
+
+        if (q->done) {
+                assert(resolve->n_done > 0);
+                resolve->n_done--;
+        }
+
+        i = q->id % QUERIES_MAX;
+        assert(resolve->query_array[i] == q);
+        resolve->query_array[i] = NULL;
+        LIST_REMOVE(queries, resolve->queries, q);
+        resolve->n_queries--;
+
+        q->resolve = NULL;
+        if (!q->floating)
+                sd_resolve_unref(resolve);
+}
+
+static sd_resolve_query *resolve_query_free(sd_resolve_query *q) {
+        assert(q);
+
+        resolve_query_disconnect(q);
+
+        if (q->destroy_callback)
+                q->destroy_callback(q->userdata);
+
+        resolve_freeaddrinfo(q->addrinfo);
+        free(q->host);
+        free(q->serv);
+
+        return mfree(q);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_resolve_query, sd_resolve_query, resolve_query_free);
+
+int sd_resolve_query_is_done(sd_resolve_query *q) {
+        assert_return(q, -EINVAL);
+        assert_return(!resolve_pid_changed(q->resolve), -ECHILD);
+
+        return q->done;
+}
+
+void* sd_resolve_query_set_userdata(sd_resolve_query *q, void *userdata) {
+        void *ret;
+
+        assert_return(q, NULL);
+        assert_return(!resolve_pid_changed(q->resolve), NULL);
+
+        ret = q->userdata;
+        q->userdata = userdata;
+
+        return ret;
+}
+
+void* sd_resolve_query_get_userdata(sd_resolve_query *q) {
+        assert_return(q, NULL);
+        assert_return(!resolve_pid_changed(q->resolve), NULL);
+
+        return q->userdata;
+}
+
+sd_resolve *sd_resolve_query_get_resolve(sd_resolve_query *q) {
+        assert_return(q, NULL);
+        assert_return(!resolve_pid_changed(q->resolve), NULL);
+
+        return q->resolve;
+}
+
+int sd_resolve_query_get_destroy_callback(sd_resolve_query *q, sd_resolve_destroy_t *destroy_callback) {
+        assert_return(q, -EINVAL);
+
+        if (destroy_callback)
+                *destroy_callback = q->destroy_callback;
+
+        return !!q->destroy_callback;
+}
+
+int sd_resolve_query_set_destroy_callback(sd_resolve_query *q, sd_resolve_destroy_t destroy_callback) {
+        assert_return(q, -EINVAL);
+
+        q->destroy_callback = destroy_callback;
+        return 0;
+}
+
+int sd_resolve_query_get_floating(sd_resolve_query *q) {
+        assert_return(q, -EINVAL);
+
+        return q->floating;
+}
+
+int sd_resolve_query_set_floating(sd_resolve_query *q, int b) {
+        assert_return(q, -EINVAL);
+
+        if (q->floating == !!b)
+                return 0;
+
+        if (!q->resolve) /* Already disconnected */
+                return -ESTALE;
+
+        q->floating = b;
+
+        if (b) {
+                sd_resolve_query_ref(q);
+                sd_resolve_unref(q->resolve);
+        } else {
+                sd_resolve_ref(q->resolve);
+                sd_resolve_query_unref(q);
+        }
+
+        return 1;
+}
+
+static int io_callback(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        sd_resolve *resolve = ASSERT_PTR(userdata);
+        int r;
+
+        r = sd_resolve_process(resolve);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+int sd_resolve_attach_event(sd_resolve *resolve, sd_event *event, int64_t priority) {
+        int r;
+
+        assert_return(resolve, -EINVAL);
+        assert_return(!resolve->event, -EBUSY);
+
+        assert(!resolve->event_source);
+
+        if (event)
+                resolve->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&resolve->event);
+                if (r < 0)
+                        return r;
+        }
+
+        r = sd_event_add_io(resolve->event, &resolve->event_source, resolve->fds[RESPONSE_RECV_FD], POLLIN, io_callback, resolve);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_source_set_priority(resolve->event_source, priority);
+        if (r < 0)
+                goto fail;
+
+        return 0;
+
+fail:
+        sd_resolve_detach_event(resolve);
+        return r;
+}
+
+ int sd_resolve_detach_event(sd_resolve *resolve) {
+        assert_return(resolve, -EINVAL);
+
+        if (!resolve->event)
+                return 0;
+
+        resolve->event_source = sd_event_source_disable_unref(resolve->event_source);
+        resolve->event = sd_event_unref(resolve->event);
+        return 1;
+}
+
+sd_event *sd_resolve_get_event(sd_resolve *resolve) {
+        assert_return(resolve, NULL);
+
+        return resolve->event;
+}
diff --git a/src/libsystemd/sd-resolve/test-resolve.c b/src/libsystemd/sd-resolve/test-resolve.c
new file mode 100644
index 0000000..829e13e
--- /dev/null
+++ b/src/libsystemd/sd-resolve/test-resolve.c
@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <net/if_arp.h>
+#include <netinet/in.h>
+#include <resolv.h>
+#include <stdio.h>
+
+#include "sd-resolve.h"
+
+#include "alloc-util.h"
+#include "macro.h"
+#include "socket-util.h"
+#include "string-util.h"
+#include "tests.h"
+#include "time-util.h"
+
+#define TEST_TIMEOUT_USEC (20*USEC_PER_SEC)
+
+static int getaddrinfo_handler(sd_resolve_query *q, int ret, const struct addrinfo *ai, void *userdata) {
+        const struct addrinfo *i;
+
+        assert_se(q);
+
+        if (ret != 0) {
+                log_error("getaddrinfo error: %s %i", gai_strerror(ret), ret);
+                return 0;
+        }
+
+        for (i = ai; i; i = i->ai_next) {
+                _cleanup_free_ char *addr = NULL;
+
+                assert_se(sockaddr_pretty(i->ai_addr, i->ai_addrlen, false, true, &addr) == 0);
+                puts(addr);
+        }
+
+        printf("canonical name: %s\n", strna(ai->ai_canonname));
+
+        return 0;
+}
+
+static int getnameinfo_handler(sd_resolve_query *q, int ret, const char *host, const char *serv, void *userdata) {
+        assert_se(q);
+
+        if (ret != 0) {
+                log_error("getnameinfo error: %s %i", gai_strerror(ret), ret);
+                return 0;
+        }
+
+        printf("Host: %s — Serv: %s\n", strna(host), strna(serv));
+        return 0;
+}
+
+int main(int argc, char *argv[]) {
+        _cleanup_(sd_resolve_query_unrefp) sd_resolve_query *q1 = NULL, *q2 = NULL;
+        _cleanup_(sd_resolve_unrefp) sd_resolve *resolve = NULL;
+        int r;
+
+        struct addrinfo hints = {
+                .ai_family = AF_UNSPEC,
+                .ai_socktype = SOCK_STREAM,
+                .ai_flags = AI_CANONNAME,
+        };
+
+        union sockaddr_union sa = {
+                .in.sin_family = AF_INET,
+                .in.sin_port = htobe16(80),
+        };
+
+        test_setup_logging(LOG_DEBUG);
+
+        assert_se(sd_resolve_default(&resolve) >= 0);
+
+        /* Test a floating resolver query */
+        r = sd_resolve_getaddrinfo(resolve, NULL, "redhat.com", "http", NULL, getaddrinfo_handler, NULL);
+        if (r < 0)
+                log_error_errno(r, "sd_resolve_getaddrinfo(): %m");
+
+        /* Make a name -> address query */
+        r = sd_resolve_getaddrinfo(resolve, &q1, argc >= 2 ? argv[1] : "www.heise.de", NULL, &hints, getaddrinfo_handler, NULL);
+        if (r < 0)
+                log_error_errno(r, "sd_resolve_getaddrinfo(): %m");
+
+        /* Make an address -> name query */
+        sa.in.sin_addr.s_addr = inet_addr(argc >= 3 ? argv[2] : "193.99.144.71");
+        r = sd_resolve_getnameinfo(resolve, &q2, &sa.sa, SOCKADDR_LEN(sa), 0, SD_RESOLVE_GET_BOTH, getnameinfo_handler, NULL);
+        if (r < 0)
+                log_error_errno(r, "sd_resolve_getnameinfo(): %m");
+
+        /* Wait until all queries are completed */
+        for (;;) {
+                r = sd_resolve_wait(resolve, TEST_TIMEOUT_USEC);
+                if (r == 0)
+                        break;
+                if (r == -ETIMEDOUT) {
+                        /* Let's catch timeouts here, so that we can run safely in a CI that has no reliable DNS. Note
+                         * that we invoke exit() directly here, as the stuck NSS call will not allow us to exit
+                         * cleanly. */
+
+                        log_notice_errno(r, "sd_resolve_wait() timed out, but that's OK");
+                        exit(EXIT_SUCCESS);
+                }
+                if (r < 0) {
+                        log_error_errno(r, "sd_resolve_wait(): %m");
+                        assert_not_reached();
+                }
+        }
+
+        return 0;
+}