sd-ipv4acd: introduce new library split out from sd-ipv4ll

This splits the Address Conflict Detection out of the Link Local
library so that we can reuse it for DHCP and static addresses in
the future.

Implements RFC5227.

1 files changed, 529 insertions, 0 deletions

diff --git a/src/libsystemd-network/sd-ipv4acd.c b/src/libsystemd-network/sd-ipv4acd.c
new file mode 100644
index 0000000000..ee5d13c030
--- /dev/null
+++ b/src/libsystemd-network/sd-ipv4acd.c
@@ -0,0 +1,529 @@
+/***
+  This file is part of systemd.
+
+  Copyright (C) 2014 Axis Communications AB. All rights reserved.
+  Copyright (C) 2015 Tom Gundersen
+
+  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 <arpa/inet.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "event-util.h"
+#include "in-addr-util.h"
+#include "list.h"
+#include "refcnt.h"
+#include "random-util.h"
+#include "siphash24.h"
+#include "util.h"
+
+#include "arp-util.h"
+#include "sd-ipv4acd.h"
+
+/* Constants from the RFC */
+#define PROBE_WAIT 1
+#define PROBE_NUM 3
+#define PROBE_MIN 1
+#define PROBE_MAX 2
+#define ANNOUNCE_WAIT 2
+#define ANNOUNCE_NUM 2
+#define ANNOUNCE_INTERVAL 2
+#define MAX_CONFLICTS 10
+#define RATE_LIMIT_INTERVAL 60
+#define DEFEND_INTERVAL 10
+
+#define IPV4ACD_NETWORK 0xA9FE0000L
+#define IPV4ACD_NETMASK 0xFFFF0000L
+
+#define log_ipv4acd_full(ll, level, error, fmt, ...) log_internal(level, error, __FILE__, __LINE__, __func__, "ACD: " fmt, ##__VA_ARGS__)
+
+#define log_ipv4acd_debug(ll, ...)   log_ipv4acd_full(ll, LOG_DEBUG, 0, ##__VA_ARGS__)
+#define log_ipv4acd_info(ll, ...)    log_ipv4acd_full(ll, LOG_INFO, 0, ##__VA_ARGS__)
+#define log_ipv4acd_notice(ll, ...)  log_ipv4acd_full(ll, LOG_NOTICE, 0, ##__VA_ARGS__)
+#define log_ipv4acd_warning(ll, ...) log_ipv4acd_full(ll, LOG_WARNING, 0, ##__VA_ARGS__)
+#define log_ipv4acd_error(ll, ...)   log_ipv4acd_full(ll, LOG_ERR, 0, ##__VA_ARGS__)
+
+#define log_ipv4acd_debug_errno(ll, error, ...)   log_ipv4acd_full(ll, LOG_DEBUG, error, ##__VA_ARGS__)
+#define log_ipv4acd_info_errno(ll, error, ...)    log_ipv4acd_full(ll, LOG_INFO, error, ##__VA_ARGS__)
+#define log_ipv4acd_notice_errno(ll, error, ...)  log_ipv4acd_full(ll, LOG_NOTICE, error, ##__VA_ARGS__)
+#define log_ipv4acd_warning_errno(ll, error, ...) log_ipv4acd_full(ll, LOG_WARNING, error, ##__VA_ARGS__)
+#define log_ipv4acd_error_errno(ll, error, ...)   log_ipv4acd_full(ll, LOG_ERR, error, ##__VA_ARGS__)
+
+typedef enum IPv4ACDState {
+        IPV4ACD_STATE_INIT,
+        IPV4ACD_STATE_WAITING_PROBE,
+        IPV4ACD_STATE_PROBING,
+        IPV4ACD_STATE_WAITING_ANNOUNCE,
+        IPV4ACD_STATE_ANNOUNCING,
+        IPV4ACD_STATE_RUNNING,
+        _IPV4ACD_STATE_MAX,
+        _IPV4ACD_STATE_INVALID = -1
+} IPv4ACDState;
+
+struct sd_ipv4acd {
+        RefCount n_ref;
+
+        IPv4ACDState state;
+        int index;
+        int fd;
+        int iteration;
+        int conflict;
+        sd_event_source *receive_message;
+        sd_event_source *timer;
+        usec_t defend_window;
+        be32_t address;
+        /* External */
+        struct ether_addr mac_addr;
+        sd_event *event;
+        int event_priority;
+        sd_ipv4acd_cb_t cb;
+        void* userdata;
+};
+
+sd_ipv4acd *sd_ipv4acd_ref(sd_ipv4acd *ll) {
+        if (ll)
+                assert_se(REFCNT_INC(ll->n_ref) >= 2);
+
+        return ll;
+}
+
+sd_ipv4acd *sd_ipv4acd_unref(sd_ipv4acd *ll) {
+        if (!ll || REFCNT_DEC(ll->n_ref) > 0)
+                return NULL;
+
+        ll->receive_message = sd_event_source_unref(ll->receive_message);
+        ll->fd = safe_close(ll->fd);
+
+        ll->timer = sd_event_source_unref(ll->timer);
+
+        sd_ipv4acd_detach_event(ll);
+
+        free(ll);
+
+        return NULL;
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(sd_ipv4acd*, sd_ipv4acd_unref);
+#define _cleanup_ipv4acd_unref_ _cleanup_(sd_ipv4acd_unrefp)
+
+int sd_ipv4acd_new(sd_ipv4acd **ret) {
+        _cleanup_ipv4acd_unref_ sd_ipv4acd *ll = NULL;
+
+        assert_return(ret, -EINVAL);
+
+        ll = new0(sd_ipv4acd, 1);
+        if (!ll)
+                return -ENOMEM;
+
+        ll->n_ref = REFCNT_INIT;
+        ll->state = IPV4ACD_STATE_INIT;
+        ll->index = -1;
+        ll->fd = -1;
+
+        *ret = ll;
+        ll = NULL;
+
+        return 0;
+}
+
+static void ipv4acd_set_state(sd_ipv4acd *ll, IPv4ACDState st, bool reset_counter) {
+
+        assert(ll);
+        assert(st < _IPV4ACD_STATE_MAX);
+
+        if (st == ll->state && !reset_counter)
+                ll->iteration++;
+        else {
+                ll->state = st;
+                ll->iteration = 0;
+        }
+}
+
+static void ipv4acd_client_notify(sd_ipv4acd *ll, int event) {
+        assert(ll);
+
+        if (ll->cb)
+                ll->cb(ll, event, ll->userdata);
+}
+
+static void ipv4acd_stop(sd_ipv4acd *ll) {
+        assert(ll);
+
+        ll->receive_message = sd_event_source_unref(ll->receive_message);
+        ll->fd = safe_close(ll->fd);
+
+        ll->timer = sd_event_source_unref(ll->timer);
+
+        log_ipv4acd_debug(ll, "STOPPED");
+
+        ipv4acd_set_state (ll, IPV4ACD_STATE_INIT, true);
+}
+
+int sd_ipv4acd_stop(sd_ipv4acd *ll) {
+        assert_return(ll, -EINVAL);
+
+        ipv4acd_stop(ll);
+
+        ipv4acd_client_notify(ll, IPV4ACD_EVENT_STOP);
+
+        return 0;
+}
+
+static int ipv4acd_on_timeout(sd_event_source *s, uint64_t usec, void *userdata);
+
+static int ipv4acd_set_next_wakeup(sd_ipv4acd *ll, int sec, int random_sec) {
+        _cleanup_event_source_unref_ sd_event_source *timer = NULL;
+        usec_t next_timeout;
+        usec_t time_now;
+        int r;
+
+        assert(sec >= 0);
+        assert(random_sec >= 0);
+        assert(ll);
+
+        next_timeout = sec * USEC_PER_SEC;
+
+        if (random_sec)
+                next_timeout += random_u32() % (random_sec * USEC_PER_SEC);
+
+        assert_se(sd_event_now(ll->event, clock_boottime_or_monotonic(), &time_now) >= 0);
+
+        r = sd_event_add_time(ll->event, &timer, clock_boottime_or_monotonic(),
+                              time_now + next_timeout, 0, ipv4acd_on_timeout, ll);
+        if (r < 0)
+                return r;
+
+        r = sd_event_source_set_priority(timer, ll->event_priority);
+        if (r < 0)
+                return r;
+
+        r = sd_event_source_set_description(timer, "ipv4acd-timer");
+        if (r < 0)
+                return r;
+
+        ll->timer = sd_event_source_unref(ll->timer);
+        ll->timer = timer;
+        timer = NULL;
+
+        return 0;
+}
+
+static bool ipv4acd_arp_conflict(sd_ipv4acd *ll, struct ether_arp *arp) {
+        assert(ll);
+        assert(arp);
+
+        /* see the BPF */
+        if (memcmp(arp->arp_spa, &ll->address, sizeof(ll->address)) == 0)
+                return true;
+
+        /* the TPA matched instead of the SPA, this is not a conflict */
+        return false;
+}
+
+static int ipv4acd_on_timeout(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_ipv4acd *ll = userdata;
+        int r = 0;
+
+        assert(ll);
+
+        switch (ll->state) {
+        case IPV4ACD_STATE_INIT:
+
+                ipv4acd_set_state(ll, IPV4ACD_STATE_WAITING_PROBE, true);
+
+                if (ll->conflict >= MAX_CONFLICTS) {
+                        log_ipv4acd_notice(ll, "Max conflicts reached, delaying by %us", RATE_LIMIT_INTERVAL);
+                        r = ipv4acd_set_next_wakeup(ll, RATE_LIMIT_INTERVAL, PROBE_WAIT);
+                        if (r < 0)
+                                goto out;
+
+                        ll->conflict = 0;
+                } else {
+                        r = ipv4acd_set_next_wakeup(ll, 0, PROBE_WAIT);
+                        if (r < 0)
+                                goto out;
+                }
+
+                break;
+        case IPV4ACD_STATE_WAITING_PROBE:
+        case IPV4ACD_STATE_PROBING:
+                /* Send a probe */
+                r = arp_send_probe(ll->fd, ll->index, ll->address, &ll->mac_addr);
+                if (r < 0) {
+                        log_ipv4acd_error_errno(ll, r, "Failed to send ARP probe: %m");
+                        goto out;
+                } else {
+                        _cleanup_free_ char *address = NULL;
+                        union in_addr_union addr = { .in.s_addr = ll->address };
+
+                        r = in_addr_to_string(AF_INET, &addr, &address);
+                        if (r >= 0)
+                                log_ipv4acd_debug(ll, "Probing %s", address);
+                }
+
+                if (ll->iteration < PROBE_NUM - 2) {
+                        ipv4acd_set_state(ll, IPV4ACD_STATE_PROBING, false);
+
+                        r = ipv4acd_set_next_wakeup(ll, PROBE_MIN, (PROBE_MAX-PROBE_MIN));
+                        if (r < 0)
+                                goto out;
+                } else {
+                        ipv4acd_set_state(ll, IPV4ACD_STATE_WAITING_ANNOUNCE, true);
+
+                        r = ipv4acd_set_next_wakeup(ll, ANNOUNCE_WAIT, 0);
+                        if (r < 0)
+                                goto out;
+                }
+
+                break;
+
+        case IPV4ACD_STATE_ANNOUNCING:
+                if (ll->iteration >= ANNOUNCE_NUM - 1) {
+                        ipv4acd_set_state(ll, IPV4ACD_STATE_RUNNING, false);
+
+                        break;
+                }
+        case IPV4ACD_STATE_WAITING_ANNOUNCE:
+                /* Send announcement packet */
+                r = arp_send_announcement(ll->fd, ll->index, ll->address, &ll->mac_addr);
+                if (r < 0) {
+                        log_ipv4acd_error_errno(ll, r, "Failed to send ARP announcement: %m");
+                        goto out;
+                } else
+                        log_ipv4acd_debug(ll, "ANNOUNCE");
+
+                ipv4acd_set_state(ll, IPV4ACD_STATE_ANNOUNCING, false);
+
+                r = ipv4acd_set_next_wakeup(ll, ANNOUNCE_INTERVAL, 0);
+                if (r < 0)
+                        goto out;
+
+                if (ll->iteration == 0) {
+                        ll->conflict = 0;
+                        ipv4acd_client_notify(ll, IPV4ACD_EVENT_BIND);
+                }
+
+                break;
+        default:
+                assert_not_reached("Invalid state.");
+        }
+
+out:
+        if (r < 0)
+                sd_ipv4acd_stop(ll);
+
+        return 1;
+}
+
+static void ipv4acd_on_conflict(sd_ipv4acd *ll) {
+        _cleanup_free_ char *address = NULL;
+        union in_addr_union addr = { .in.s_addr = ll->address };
+        int r;
+
+        assert(ll);
+
+        ll->conflict++;
+
+        r = in_addr_to_string(AF_INET, &addr, &address);
+        if (r >= 0)
+                log_ipv4acd_debug(ll, "Conflict on %s (%u)", address, ll->conflict);
+
+        ipv4acd_stop(ll);
+
+        ipv4acd_client_notify(ll, IPV4ACD_EVENT_CONFLICT);
+}
+
+static int ipv4acd_on_packet(sd_event_source *s, int fd,
+                            uint32_t revents, void *userdata) {
+        sd_ipv4acd *ll = userdata;
+        struct ether_arp packet;
+        int r;
+
+        assert(ll);
+        assert(fd >= 0);
+
+        r = read(fd, &packet, sizeof(struct ether_arp));
+        if (r < (int) sizeof(struct ether_arp))
+                goto out;
+
+        switch (ll->state) {
+        case IPV4ACD_STATE_ANNOUNCING:
+        case IPV4ACD_STATE_RUNNING:
+                if (ipv4acd_arp_conflict(ll, &packet)) {
+                        usec_t ts;
+
+                        assert_se(sd_event_now(ll->event, clock_boottime_or_monotonic(), &ts) >= 0);
+
+                        /* Defend address */
+                        if (ts > ll->defend_window) {
+                                ll->defend_window = ts + DEFEND_INTERVAL * USEC_PER_SEC;
+                                r = arp_send_announcement(ll->fd, ll->index, ll->address, &ll->mac_addr);
+                                if (r < 0) {
+                                        log_ipv4acd_error_errno(ll, r, "Failed to send ARP announcement: %m");
+                                        goto out;
+                                } else
+                                        log_ipv4acd_debug(ll, "DEFEND");
+
+                        } else
+                                ipv4acd_on_conflict(ll);
+                }
+
+                break;
+        case IPV4ACD_STATE_WAITING_PROBE:
+        case IPV4ACD_STATE_PROBING:
+        case IPV4ACD_STATE_WAITING_ANNOUNCE:
+                /* BPF ensures this packet indicates a conflict */
+                ipv4acd_on_conflict(ll);
+
+                break;
+        default:
+                assert_not_reached("Invalid state.");
+        }
+
+out:
+        if (r < 0)
+                sd_ipv4acd_stop(ll);
+
+        return 1;
+}
+
+int sd_ipv4acd_set_index(sd_ipv4acd *ll, int interface_index) {
+        assert_return(ll, -EINVAL);
+        assert_return(interface_index > 0, -EINVAL);
+        assert_return(ll->state == IPV4ACD_STATE_INIT, -EBUSY);
+
+        ll->index = interface_index;
+
+        return 0;
+}
+
+int sd_ipv4acd_set_mac(sd_ipv4acd *ll, const struct ether_addr *addr) {
+        assert_return(ll, -EINVAL);
+        assert_return(addr, -EINVAL);
+        assert_return(ll->state == IPV4ACD_STATE_INIT, -EBUSY);
+
+        memcpy(&ll->mac_addr, addr, ETH_ALEN);
+
+        return 0;
+}
+
+int sd_ipv4acd_detach_event(sd_ipv4acd *ll) {
+        assert_return(ll, -EINVAL);
+
+        ll->event = sd_event_unref(ll->event);
+
+        return 0;
+}
+
+int sd_ipv4acd_attach_event(sd_ipv4acd *ll, sd_event *event, int priority) {
+        int r;
+
+        assert_return(ll, -EINVAL);
+        assert_return(!ll->event, -EBUSY);
+
+        if (event)
+                ll->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&ll->event);
+                if (r < 0)
+                        return r;
+        }
+
+        ll->event_priority = priority;
+
+        return 0;
+}
+
+int sd_ipv4acd_set_callback(sd_ipv4acd *ll, sd_ipv4acd_cb_t cb, void *userdata) {
+        assert_return(ll, -EINVAL);
+
+        ll->cb = cb;
+        ll->userdata = userdata;
+
+        return 0;
+}
+
+int sd_ipv4acd_set_address(sd_ipv4acd *ll, const struct in_addr *address){
+        assert_return(ll, -EINVAL);
+        assert_return(address, -EINVAL);
+        assert_return(ll->state == IPV4ACD_STATE_INIT, -EBUSY);
+
+        ll->address = address->s_addr;
+
+        return 0;
+}
+
+bool sd_ipv4acd_is_running(sd_ipv4acd *ll) {
+        assert_return(ll, false);
+
+        return ll->state != IPV4ACD_STATE_INIT;
+}
+
+static bool ether_addr_is_nul(const struct ether_addr *addr) {
+        const struct ether_addr nul_addr = {};
+
+        assert(addr);
+
+        return memcmp(addr, &nul_addr, sizeof(struct ether_addr)) == 0;
+}
+
+#define HASH_KEY SD_ID128_MAKE(df,04,22,98,3f,ad,14,52,f9,87,2e,d1,9c,70,e2,f2)
+
+int sd_ipv4acd_start(sd_ipv4acd *ll) {
+        int r;
+
+        assert_return(ll, -EINVAL);
+        assert_return(ll->event, -EINVAL);
+        assert_return(ll->index > 0, -EINVAL);
+        assert_return(ll->address != 0, -EINVAL);
+        assert_return(!ether_addr_is_nul(&ll->mac_addr), -EINVAL);
+        assert_return(ll->state == IPV4ACD_STATE_INIT, -EBUSY);
+
+        ll->defend_window = 0;
+
+        r = arp_network_bind_raw_socket(ll->index, ll->address, &ll->mac_addr);
+        if (r < 0)
+                goto out;
+
+        ll->fd = safe_close(ll->fd);
+        ll->fd = r;
+
+        r = sd_event_add_io(ll->event, &ll->receive_message, ll->fd,
+                            EPOLLIN, ipv4acd_on_packet, ll);
+        if (r < 0)
+                goto out;
+
+        r = sd_event_source_set_priority(ll->receive_message, ll->event_priority);
+        if (r < 0)
+                goto out;
+
+        r = sd_event_source_set_description(ll->receive_message, "ipv4acd-receive-message");
+        if (r < 0)
+                goto out;
+
+        r = ipv4acd_set_next_wakeup(ll, 0, 0);
+        if (r < 0)
+                goto out;
+out:
+        if (r < 0) {
+                ipv4acd_stop(ll);
+                return r;
+        }
+
+        return 0;
+}