libsystemd-rtnl: merge into libsystemd

1 files changed, 870 insertions, 0 deletions

diff --git a/src/libsystemd/sd-rtnl.c b/src/libsystemd/sd-rtnl.c
new file mode 100644
index 0000000000..08b82ab2a9
--- /dev/null
+++ b/src/libsystemd/sd-rtnl.c
@@ -0,0 +1,870 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2013 Tom Gundersen <teg@jklm.no>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/socket.h>
+#include <poll.h>
+
+#include "macro.h"
+#include "util.h"
+#include "hashmap.h"
+
+#include "sd-rtnl.h"
+#include "rtnl-internal.h"
+#include "rtnl-util.h"
+
+static int sd_rtnl_new(sd_rtnl **ret) {
+        sd_rtnl *rtnl;
+
+        assert_return(ret, -EINVAL);
+
+        rtnl = new0(sd_rtnl, 1);
+        if (!rtnl)
+                return -ENOMEM;
+
+        rtnl->n_ref = REFCNT_INIT;
+
+        rtnl->fd = -1;
+
+        rtnl->sockaddr.nl.nl_family = AF_NETLINK;
+
+        rtnl->original_pid = getpid();
+
+        LIST_HEAD_INIT(rtnl->match_callbacks);
+
+        /* We guarantee that wqueue always has space for at least
+         * one entry */
+        rtnl->wqueue = new(sd_rtnl_message*, 1);
+        if (!rtnl->wqueue) {
+                free(rtnl);
+                return -ENOMEM;
+        }
+
+        *ret = rtnl;
+        return 0;
+}
+
+static bool rtnl_pid_changed(sd_rtnl *rtnl) {
+        assert(rtnl);
+
+        /* We don't support people creating an rtnl connection and
+         * keeping it around over a fork(). Let's complain. */
+
+        return rtnl->original_pid != getpid();
+}
+
+int sd_rtnl_open(uint32_t groups, sd_rtnl **ret) {
+        _cleanup_sd_rtnl_unref_ sd_rtnl *rtnl = NULL;
+        socklen_t addrlen;
+        int r;
+
+        assert_return(ret, -EINVAL);
+
+        r = sd_rtnl_new(&rtnl);
+        if (r < 0)
+                return r;
+
+        rtnl->fd = socket(PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_ROUTE);
+        if (rtnl->fd < 0)
+                return -errno;
+
+        rtnl->sockaddr.nl.nl_groups = groups;
+
+        addrlen = sizeof(rtnl->sockaddr);
+
+        r = bind(rtnl->fd, &rtnl->sockaddr.sa, addrlen);
+        if (r < 0)
+                return -errno;
+
+        r = getsockname(rtnl->fd, &rtnl->sockaddr.sa, &addrlen);
+        if (r < 0)
+                return r;
+
+        *ret = rtnl;
+        rtnl = NULL;
+
+        return 0;
+}
+
+sd_rtnl *sd_rtnl_ref(sd_rtnl *rtnl) {
+        if (rtnl)
+                assert_se(REFCNT_INC(rtnl->n_ref) >= 2);
+
+        return rtnl;
+}
+
+sd_rtnl *sd_rtnl_unref(sd_rtnl *rtnl) {
+
+        if (rtnl && REFCNT_DEC(rtnl->n_ref) <= 0) {
+                struct match_callback *f;
+                unsigned i;
+
+                for (i = 0; i < rtnl->rqueue_size; i++)
+                        sd_rtnl_message_unref(rtnl->rqueue[i]);
+                free(rtnl->rqueue);
+
+                for (i = 0; i < rtnl->wqueue_size; i++)
+                        sd_rtnl_message_unref(rtnl->wqueue[i]);
+                free(rtnl->wqueue);
+
+                hashmap_free_free(rtnl->reply_callbacks);
+                prioq_free(rtnl->reply_callbacks_prioq);
+
+                while ((f = rtnl->match_callbacks)) {
+                        LIST_REMOVE(match_callbacks, rtnl->match_callbacks, f);
+                        free(f);
+                }
+
+                if (rtnl->fd >= 0)
+                        close_nointr_nofail(rtnl->fd);
+
+                free(rtnl);
+        }
+
+        return NULL;
+}
+
+int sd_rtnl_send(sd_rtnl *nl,
+                 sd_rtnl_message *message,
+                 uint32_t *serial) {
+        int r;
+
+        assert_return(nl, -EINVAL);
+        assert_return(!rtnl_pid_changed(nl), -ECHILD);
+        assert_return(message, -EINVAL);
+
+        r = message_seal(nl, message);
+        if (r < 0)
+                return r;
+
+        if (nl->wqueue_size <= 0) {
+                /* send directly */
+                r = socket_write_message(nl, message);
+                if (r < 0)
+                        return r;
+                else if (r == 0) {
+                        /* nothing was sent, so let's put it on
+                         * the queue */
+                        nl->wqueue[0] = sd_rtnl_message_ref(message);
+                        nl->wqueue_size = 1;
+                }
+        } else {
+                sd_rtnl_message **q;
+
+                /* append to queue */
+                if (nl->wqueue_size >= RTNL_WQUEUE_MAX)
+                        return -ENOBUFS;
+
+                q = realloc(nl->wqueue, sizeof(sd_rtnl_message*) * (nl->wqueue_size + 1));
+                if (!q)
+                        return -ENOMEM;
+
+                nl->wqueue = q;
+                q[nl->wqueue_size ++] = sd_rtnl_message_ref(message);
+        }
+
+        if (serial)
+                *serial = message_get_serial(message);
+
+        return 1;
+}
+
+static int dispatch_rqueue(sd_rtnl *rtnl, sd_rtnl_message **message) {
+        sd_rtnl_message *z = NULL;
+        int r;
+
+        assert(rtnl);
+        assert(message);
+
+        if (rtnl->rqueue_size > 0) {
+                /* Dispatch a queued message */
+
+                *message = rtnl->rqueue[0];
+                rtnl->rqueue_size --;
+                memmove(rtnl->rqueue, rtnl->rqueue + 1, sizeof(sd_rtnl_message*) * rtnl->rqueue_size);
+
+                return 1;
+        }
+
+        /* Try to read a new message */
+        r = socket_read_message(rtnl, &z);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return 0;
+
+        *message = z;
+
+        return 1;
+}
+
+static int dispatch_wqueue(sd_rtnl *rtnl) {
+        int r, ret = 0;
+
+        assert(rtnl);
+
+        while (rtnl->wqueue_size > 0) {
+                r = socket_write_message(rtnl, rtnl->wqueue[0]);
+                if (r < 0)
+                        return r;
+                else if (r == 0)
+                        /* Didn't do anything this time */
+                        return ret;
+                else {
+                        /* see equivalent in sd-bus.c */
+                        sd_rtnl_message_unref(rtnl->wqueue[0]);
+                        rtnl->wqueue_size --;
+                        memmove(rtnl->wqueue, rtnl->wqueue + 1, sizeof(sd_rtnl_message*) * rtnl->wqueue_size);
+
+                        ret = 1;
+                }
+        }
+
+        return ret;
+}
+
+static int process_timeout(sd_rtnl *rtnl) {
+        _cleanup_sd_rtnl_message_unref_ sd_rtnl_message *m = NULL;
+        struct reply_callback *c;
+        usec_t n;
+        int r;
+
+        assert(rtnl);
+
+        c = prioq_peek(rtnl->reply_callbacks_prioq);
+        if (!c)
+                return 0;
+
+        n = now(CLOCK_MONOTONIC);
+        if (c->timeout > n)
+                return 0;
+
+        r = message_new_synthetic_error(-ETIMEDOUT, c->serial, &m);
+        if (r < 0)
+                return r;
+
+        assert_se(prioq_pop(rtnl->reply_callbacks_prioq) == c);
+        hashmap_remove(rtnl->reply_callbacks, &c->serial);
+
+        r = c->callback(rtnl, m, c->userdata);
+        free(c);
+
+        return r < 0 ? r : 1;
+}
+
+static int process_reply(sd_rtnl *rtnl, sd_rtnl_message *m) {
+        struct reply_callback *c;
+        uint64_t serial;
+        int r;
+
+        assert(rtnl);
+        assert(m);
+
+        serial = message_get_serial(m);
+        c = hashmap_remove(rtnl->reply_callbacks, &serial);
+        if (!c)
+                return 0;
+
+        if (c->timeout != 0)
+                prioq_remove(rtnl->reply_callbacks_prioq, c, &c->prioq_idx);
+
+        r = c->callback(rtnl, m, c->userdata);
+        free(c);
+
+        return r;
+}
+
+static int process_match(sd_rtnl *rtnl, sd_rtnl_message *m) {
+        struct match_callback *c;
+        uint16_t type;
+        int r;
+
+        assert(rtnl);
+        assert(m);
+
+        r = sd_rtnl_message_get_type(m, &type);
+        if (r < 0)
+                return r;
+
+        LIST_FOREACH(match_callbacks, c, rtnl->match_callbacks) {
+                if (type == c->type) {
+                        r = c->callback(rtnl, m, c->userdata);
+                        if (r != 0)
+                                return r;
+                }
+        }
+
+        return 0;
+}
+
+static int process_running(sd_rtnl *rtnl, sd_rtnl_message **ret) {
+        _cleanup_sd_rtnl_message_unref_ sd_rtnl_message *m = NULL;
+        int r;
+
+        assert(rtnl);
+
+        r = process_timeout(rtnl);
+        if (r != 0)
+                goto null_message;
+
+        r = dispatch_wqueue(rtnl);
+        if (r != 0)
+                goto null_message;
+
+        r = dispatch_rqueue(rtnl, &m);
+        if (r < 0)
+                return r;
+        if (!m)
+                goto null_message;
+
+        r = process_reply(rtnl, m);
+        if (r != 0)
+                goto null_message;
+
+        r = process_match(rtnl, m);
+        if (r != 0)
+                goto null_message;
+
+        if (ret) {
+                *ret = m;
+                m = NULL;
+
+                return 1;
+        }
+
+        return 1;
+
+null_message:
+        if (r >= 0 && ret)
+                *ret = NULL;
+
+        return r;
+}
+
+int sd_rtnl_process(sd_rtnl *rtnl, sd_rtnl_message **ret) {
+        RTNL_DONT_DESTROY(rtnl);
+        int r;
+
+        assert_return(rtnl, -EINVAL);
+        assert_return(!rtnl_pid_changed(rtnl), -ECHILD);
+        assert_return(!rtnl->processing, -EBUSY);
+
+        rtnl->processing = true;
+        r = process_running(rtnl, ret);
+        rtnl->processing = false;
+
+        return r;
+}
+
+static usec_t calc_elapse(uint64_t usec) {
+        if (usec == (uint64_t) -1)
+                return 0;
+
+        if (usec == 0)
+                usec = RTNL_DEFAULT_TIMEOUT;
+
+        return now(CLOCK_MONOTONIC) + usec;
+}
+
+static int rtnl_poll(sd_rtnl *rtnl, bool need_more, uint64_t timeout_usec) {
+        struct pollfd p[1] = {};
+        struct timespec ts;
+        usec_t m = (usec_t) -1;
+        int r, e;
+
+        assert(rtnl);
+
+        e = sd_rtnl_get_events(rtnl);
+        if (e < 0)
+                return e;
+
+        if (need_more)
+                /* Caller wants more data, and doesn't care about
+                 * what's been read or any other timeouts. */
+                return e |= POLLIN;
+        else {
+                usec_t until;
+                /* Caller wants to process if there is something to
+                 * process, but doesn't care otherwise */
+
+                r = sd_rtnl_get_timeout(rtnl, &until);
+                if (r < 0)
+                        return r;
+                if (r > 0) {
+                        usec_t nw;
+                        nw = now(CLOCK_MONOTONIC);
+                        m = until > nw ? until - nw : 0;
+                }
+        }
+
+        if (timeout_usec != (uint64_t) -1 && (m == (uint64_t) -1 || timeout_usec < m))
+                m = timeout_usec;
+
+        p[0].fd = rtnl->fd;
+        p[0].events = e;
+
+        r = ppoll(p, 1, m == (uint64_t) -1 ? NULL : timespec_store(&ts, m), NULL);
+        if (r < 0)
+                return -errno;
+
+        return r > 0 ? 1 : 0;
+}
+
+int sd_rtnl_wait(sd_rtnl *nl, uint64_t timeout_usec) {
+        assert_return(nl, -EINVAL);
+        assert_return(!rtnl_pid_changed(nl), -ECHILD);
+
+        if (nl->rqueue_size > 0)
+                return 0;
+
+        return rtnl_poll(nl, false, timeout_usec);
+}
+
+static int timeout_compare(const void *a, const void *b) {
+        const struct reply_callback *x = a, *y = b;
+
+        if (x->timeout != 0 && y->timeout == 0)
+                return -1;
+
+        if (x->timeout == 0 && y->timeout != 0)
+                return 1;
+
+        if (x->timeout < y->timeout)
+                return -1;
+
+        if (x->timeout > y->timeout)
+                return 1;
+
+        return 0;
+}
+
+int sd_rtnl_call_async(sd_rtnl *nl,
+                       sd_rtnl_message *m,
+                       sd_rtnl_message_handler_t callback,
+                       void *userdata,
+                       uint64_t usec,
+                       uint32_t *serial) {
+        struct reply_callback *c;
+        uint32_t s;
+        int r, k;
+
+        assert_return(nl, -EINVAL);
+        assert_return(m, -EINVAL);
+        assert_return(callback, -EINVAL);
+        assert_return(!rtnl_pid_changed(nl), -ECHILD);
+
+        r = hashmap_ensure_allocated(&nl->reply_callbacks, uint64_hash_func, uint64_compare_func);
+        if (r < 0)
+                return r;
+
+        if (usec != (uint64_t) -1) {
+                r = prioq_ensure_allocated(&nl->reply_callbacks_prioq, timeout_compare);
+                if (r < 0)
+                        return r;
+        }
+
+        c = new0(struct reply_callback, 1);
+        if (!c)
+                return -ENOMEM;
+
+        c->callback = callback;
+        c->userdata = userdata;
+        c->timeout = calc_elapse(usec);
+
+        k = sd_rtnl_send(nl, m, &s);
+        if (k < 0) {
+                free(c);
+                return k;
+        }
+
+        c->serial = s;
+
+        r = hashmap_put(nl->reply_callbacks, &c->serial, c);
+        if (r < 0) {
+                free(c);
+                return r;
+        }
+
+        if (c->timeout != 0) {
+                r = prioq_put(nl->reply_callbacks_prioq, c, &c->prioq_idx);
+                if (r > 0) {
+                        c->timeout = 0;
+                        sd_rtnl_call_async_cancel(nl, c->serial);
+                        return r;
+                }
+        }
+
+        if (serial)
+                *serial = s;
+
+        return k;
+}
+
+int sd_rtnl_call_async_cancel(sd_rtnl *nl, uint32_t serial) {
+        struct reply_callback *c;
+        uint64_t s = serial;
+
+        assert_return(nl, -EINVAL);
+        assert_return(serial != 0, -EINVAL);
+        assert_return(!rtnl_pid_changed(nl), -ECHILD);
+
+        c = hashmap_remove(nl->reply_callbacks, &s);
+        if (!c)
+                return 0;
+
+        if (c->timeout != 0)
+                prioq_remove(nl->reply_callbacks_prioq, c, &c->prioq_idx);
+
+        free(c);
+        return 1;
+}
+
+int sd_rtnl_call(sd_rtnl *nl,
+                sd_rtnl_message *message,
+                uint64_t usec,
+                sd_rtnl_message **ret) {
+        usec_t timeout;
+        uint32_t serial;
+        bool room = false;
+        int r;
+
+        assert_return(nl, -EINVAL);
+        assert_return(!rtnl_pid_changed(nl), -ECHILD);
+        assert_return(message, -EINVAL);
+
+        r = sd_rtnl_send(nl, message, &serial);
+        if (r < 0)
+                return r;
+
+        timeout = calc_elapse(usec);
+
+        for (;;) {
+                usec_t left;
+                _cleanup_sd_rtnl_message_unref_ sd_rtnl_message *incoming = NULL;
+
+                if (!room) {
+                        sd_rtnl_message **q;
+
+                        if (nl->rqueue_size >= RTNL_RQUEUE_MAX)
+                                return -ENOBUFS;
+
+                        /* Make sure there's room for queueing this
+                         * locally, before we read the message */
+
+                        q = realloc(nl->rqueue, (nl->rqueue_size + 1) * sizeof(sd_rtnl_message*));
+                        if (!q)
+                                return -ENOMEM;
+
+                        nl->rqueue = q;
+                        room = true;
+                }
+
+                r = socket_read_message(nl, &incoming);
+                if (r < 0)
+                        return r;
+                if (incoming) {
+                        uint32_t received_serial = message_get_serial(incoming);
+
+                        if (received_serial == serial) {
+                                r = sd_rtnl_message_get_errno(incoming);
+                                if (r < 0)
+                                        return r;
+
+                                if (ret) {
+                                        *ret = incoming;
+                                        incoming = NULL;
+                                }
+
+                                return 1;
+                        }
+
+                        /* Room was allocated on the queue above */
+                        nl->rqueue[nl->rqueue_size ++] = incoming;
+                        incoming = NULL;
+                        room = false;
+
+                        /* Try to read more, right away */
+                        continue;
+                }
+                if (r != 0)
+                        continue;
+
+                if (timeout > 0) {
+                        usec_t n;
+
+                        n = now(CLOCK_MONOTONIC);
+                        if (n >= timeout)
+                                return -ETIMEDOUT;
+
+                        left = timeout - n;
+                } else
+                        left = (uint64_t) -1;
+
+                r = rtnl_poll(nl, true, left);
+                if (r < 0)
+                        return r;
+
+                r = dispatch_wqueue(nl);
+                if (r < 0)
+                        return r;
+        }
+}
+
+int sd_rtnl_flush(sd_rtnl *rtnl) {
+        int r;
+
+        assert_return(rtnl, -EINVAL);
+        assert_return(!rtnl_pid_changed(rtnl), -ECHILD);
+
+        if (rtnl->wqueue_size <= 0)
+                return 0;
+
+        for (;;) {
+                r = dispatch_wqueue(rtnl);
+                if (r < 0)
+                        return r;
+
+                if (rtnl->wqueue_size <= 0)
+                        return 0;
+
+                r = rtnl_poll(rtnl, false, (uint64_t) -1);
+                if (r < 0)
+                        return r;
+        }
+}
+
+int sd_rtnl_get_events(sd_rtnl *rtnl) {
+        int flags = 0;
+
+        assert_return(rtnl, -EINVAL);
+        assert_return(!rtnl_pid_changed(rtnl), -ECHILD);
+
+        if (rtnl->rqueue_size <= 0)
+                flags |= POLLIN;
+        if (rtnl->wqueue_size > 0)
+                flags |= POLLOUT;
+
+        return flags;
+}
+
+int sd_rtnl_get_timeout(sd_rtnl *rtnl, uint64_t *timeout_usec) {
+        struct reply_callback *c;
+
+        assert_return(rtnl, -EINVAL);
+        assert_return(timeout_usec, -EINVAL);
+        assert_return(!rtnl_pid_changed(rtnl), -ECHILD);
+
+        if (rtnl->rqueue_size > 0) {
+                *timeout_usec = 0;
+                return 1;
+        }
+
+        c = prioq_peek(rtnl->reply_callbacks_prioq);
+        if (!c) {
+                *timeout_usec = (uint64_t) -1;
+                return 0;
+        }
+
+        *timeout_usec = c->timeout;
+
+        return 1;
+}
+
+static int io_callback(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        sd_rtnl *rtnl = userdata;
+        int r;
+
+        assert(rtnl);
+
+        r = sd_rtnl_process(rtnl, NULL);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static int time_callback(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_rtnl *rtnl = userdata;
+        int r;
+
+        assert(rtnl);
+
+        r = sd_rtnl_process(rtnl, NULL);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static int prepare_callback(sd_event_source *s, void *userdata) {
+        sd_rtnl *rtnl = userdata;
+        int r, e;
+        usec_t until;
+
+        assert(s);
+        assert(rtnl);
+
+        e = sd_rtnl_get_events(rtnl);
+        if (e < 0)
+                return e;
+
+        r = sd_event_source_set_io_events(rtnl->io_event_source, e);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_get_timeout(rtnl, &until);
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                int j;
+
+                j = sd_event_source_set_time(rtnl->time_event_source, until);
+                if (j < 0)
+                        return j;
+        }
+
+        r = sd_event_source_set_enabled(rtnl->time_event_source, r > 0);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static int exit_callback(sd_event_source *event, void *userdata) {
+        sd_rtnl *rtnl = userdata;
+
+        assert(event);
+
+        sd_rtnl_flush(rtnl);
+
+        return 1;
+}
+
+int sd_rtnl_attach_event(sd_rtnl *rtnl, sd_event *event, int priority) {
+        int r;
+
+        assert_return(rtnl, -EINVAL);
+        assert_return(!rtnl->event, -EBUSY);
+
+        assert(!rtnl->io_event_source);
+        assert(!rtnl->time_event_source);
+
+        if (event)
+                rtnl->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&rtnl->event);
+                if (r < 0)
+                        return r;
+        }
+
+        r = sd_event_add_io(rtnl->event, rtnl->fd, 0, io_callback, rtnl, &rtnl->io_event_source);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_source_set_priority(rtnl->io_event_source, priority);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_source_set_prepare(rtnl->io_event_source, prepare_callback);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_add_monotonic(rtnl->event, 0, 0, time_callback, rtnl, &rtnl->time_event_source);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_source_set_priority(rtnl->time_event_source, priority);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_add_exit(rtnl->event, exit_callback, rtnl, &rtnl->exit_event_source);
+        if (r < 0)
+                goto fail;
+
+        return 0;
+
+fail:
+        sd_rtnl_detach_event(rtnl);
+        return r;
+}
+
+int sd_rtnl_detach_event(sd_rtnl *rtnl) {
+        assert_return(rtnl, -EINVAL);
+        assert_return(rtnl->event, -ENXIO);
+
+        if (rtnl->io_event_source)
+                rtnl->io_event_source = sd_event_source_unref(rtnl->io_event_source);
+
+        if (rtnl->time_event_source)
+                rtnl->time_event_source = sd_event_source_unref(rtnl->time_event_source);
+
+        if (rtnl->exit_event_source)
+                rtnl->exit_event_source = sd_event_source_unref(rtnl->exit_event_source);
+
+        if (rtnl->event)
+                rtnl->event = sd_event_unref(rtnl->event);
+
+        return 0;
+}
+
+int sd_rtnl_add_match(sd_rtnl *rtnl,
+                      uint16_t type,
+                      sd_rtnl_message_handler_t callback,
+                      void *userdata) {
+        struct match_callback *c;
+
+        assert_return(rtnl, -EINVAL);
+        assert_return(callback, -EINVAL);
+        assert_return(!rtnl_pid_changed(rtnl), -ECHILD);
+        assert_return(message_type_is_link(type) || message_type_is_addr(type) || message_type_is_route(type), -ENOTSUP);
+
+        c = new0(struct match_callback, 1);
+        if (!c)
+                return -ENOMEM;
+
+        c->callback = callback;
+        c->type = type;
+        c->userdata = userdata;
+
+        LIST_PREPEND(match_callbacks, rtnl->match_callbacks, c);
+
+        return 0;
+}
+
+int sd_rtnl_remove_match(sd_rtnl *rtnl,
+                         uint16_t type,
+                         sd_rtnl_message_handler_t callback,
+                         void *userdata) {
+        struct match_callback *c;
+
+        assert_return(rtnl, -EINVAL);
+        assert_return(callback, -EINVAL);
+        assert_return(!rtnl_pid_changed(rtnl), -ECHILD);
+
+        LIST_FOREACH(match_callbacks, c, rtnl->match_callbacks)
+                if (c->callback == callback && c->type == type && c->userdata == userdata) {
+                        LIST_REMOVE(match_callbacks, rtnl->match_callbacks, c);
+                        free(c);
+
+                        return 1;
+                }
+
+        return 0;
+}