bfdd: Handling local and remote admin-down

[mirror_frr.git] / bfdd / bfd.c

/*********************************************************************
 * Copyright 2013 Cumulus Networks, LLC.  All rights reserved.
 * Copyright 2014,2015,2016,2017 Cumulus Networks, Inc.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program 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 General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * bfd.c: implements the BFD protocol.
 *
 * Authors
 * -------
 * Shrijeet Mukherjee [shm@cumulusnetworks.com]
 * Kanna Rajagopal [kanna@cumulusnetworks.com]
 * Radhika Mahankali [Radhika@cumulusnetworks.com]
 */

#include <zebra.h>

#include "lib/jhash.h"

#include "bfd.h"

DEFINE_MTYPE_STATIC(BFDD, BFDD_CONFIG, "long-lived configuration memory")
DEFINE_MTYPE_STATIC(BFDD, BFDD_SESSION_OBSERVER, "Session observer")
DEFINE_MTYPE_STATIC(BFDD, BFDD_VRF, "BFD VRF")

/*
 * Prototypes
 */
static uint32_t ptm_bfd_gen_ID(void);
static void ptm_bfd_echo_xmt_TO(struct bfd_session *bfd);
static struct bfd_session *bfd_find_disc(struct sockaddr_any *sa,
                                         uint32_t ldisc);
static int bfd_session_update(struct bfd_session *bs, struct bfd_peer_cfg *bpc);
static const char *get_diag_str(int diag);

static void bs_admin_down_handler(struct bfd_session *bs, int nstate);
static void bs_down_handler(struct bfd_session *bs, int nstate);
static void bs_init_handler(struct bfd_session *bs, int nstate);
static void bs_up_handler(struct bfd_session *bs, int nstate);
static void bs_neighbour_admin_down_handler(struct bfd_session *bfd,
                                            uint8_t diag);

/* Zeroed array with the size of an IPv6 address. */
struct in6_addr zero_addr;

/*
 * Functions
 */
void gen_bfd_key(struct bfd_key *key, struct sockaddr_any *peer,
                 struct sockaddr_any *local, bool mhop, const char *ifname,
                 const char *vrfname)
{
        memset(key, 0, sizeof(*key));

        switch (peer->sa_sin.sin_family) {
        case AF_INET:
                key->family = AF_INET;
                memcpy(&key->peer, &peer->sa_sin.sin_addr,
                       sizeof(peer->sa_sin.sin_addr));
                memcpy(&key->local, &local->sa_sin.sin_addr,
                       sizeof(local->sa_sin.sin_addr));
                break;
        case AF_INET6:
                key->family = AF_INET6;
                memcpy(&key->peer, &peer->sa_sin6.sin6_addr,
                       sizeof(peer->sa_sin6.sin6_addr));
                memcpy(&key->local, &local->sa_sin6.sin6_addr,
                       sizeof(local->sa_sin6.sin6_addr));
                break;
        }

        key->mhop = mhop;
        if (ifname && ifname[0])
                strlcpy(key->ifname, ifname, sizeof(key->ifname));
        if (vrfname && vrfname[0])
                strlcpy(key->vrfname, vrfname, sizeof(key->vrfname));
        else
                strlcpy(key->vrfname, VRF_DEFAULT_NAME, sizeof(key->vrfname));
}

struct bfd_session *bs_peer_find(struct bfd_peer_cfg *bpc)
{
        struct bfd_session *bs;
        struct peer_label *pl;
        struct bfd_key key;

        /* Try to find label first. */
        if (bpc->bpc_has_label) {
                pl = pl_find(bpc->bpc_label);
                if (pl != NULL) {
                        bs = pl->pl_bs;
                        return bs;
                }
        }

        /* Otherwise fallback to peer/local hash lookup. */
        gen_bfd_key(&key, &bpc->bpc_peer, &bpc->bpc_local, bpc->bpc_mhop,
                    bpc->bpc_localif, bpc->bpc_vrfname);

        return bfd_key_lookup(key);
}

/*
 * Starts a disabled BFD session.
 *
 * A session is disabled when the specified interface/VRF doesn't exist
 * yet. It might happen on FRR boot or with virtual interfaces.
 */
int bfd_session_enable(struct bfd_session *bs)
{
        struct interface *ifp = NULL;
        struct vrf *vrf = NULL;
        int psock;

        /*
         * If the interface or VRF doesn't exist, then we must register
         * the session but delay its start.
         */
        if (bs->key.vrfname[0]) {
                vrf = vrf_lookup_by_name(bs->key.vrfname);
                if (vrf == NULL) {
                        log_error(
                                "session-enable: specified VRF doesn't exists.");
                        return 0;
                }
        }

        if (bs->key.ifname[0]) {
                if (vrf)
                        ifp = if_lookup_by_name(bs->key.ifname, vrf->vrf_id);
                else
                        ifp = if_lookup_by_name_all_vrf(bs->key.ifname);
                if (ifp == NULL) {
                        log_error(
                                  "session-enable: specified interface doesn't exists.");
                        return 0;
                }
                if (bs->key.ifname[0] && !vrf) {
                        vrf = vrf_lookup_by_id(ifp->vrf_id);
                        if (vrf == NULL) {
                                log_error(
                                          "session-enable: specified VRF doesn't exists.");
                                return 0;
                        }
                }
        }

        /* Assign interface/VRF pointers. */
        bs->vrf = vrf;
        if (bs->vrf == NULL)
                bs->vrf = vrf_lookup_by_id(VRF_DEFAULT);

        if (bs->key.ifname[0]
            && BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_MH) == 0)
                bs->ifp = ifp;

        /* Sanity check: don't leak open sockets. */
        if (bs->sock != -1) {
                log_debug("session-enable: previous socket open");
                close(bs->sock);
                bs->sock = -1;
        }

        /*
         * Get socket for transmitting control packets.  Note that if we
         * could use the destination port (3784) for the source
         * port we wouldn't need a socket per session.
         */
        if (BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_IPV6) == 0) {
                psock = bp_peer_socket(bs);
                if (psock == -1)
                        return 0;
        } else {
                psock = bp_peer_socketv6(bs);
                if (psock == -1)
                        return 0;
        }

        /*
         * We've got a valid socket, lets start the timers and the
         * protocol.
         */
        bs->sock = psock;
        bfd_recvtimer_update(bs);
        ptm_bfd_start_xmt_timer(bs, false);

        return 0;
}

/*
 * Disabled a running BFD session.
 *
 * A session is disabled when the specified interface/VRF gets removed
 * (e.g. virtual interfaces).
 */
void bfd_session_disable(struct bfd_session *bs)
{
        /* Free up socket resources. */
        if (bs->sock != -1) {
                close(bs->sock);
                bs->sock = -1;
        }

        /* Disable all timers. */
        bfd_recvtimer_delete(bs);
        bfd_echo_recvtimer_delete(bs);
        bfd_xmttimer_delete(bs);
        bfd_echo_xmttimer_delete(bs);
}

static uint32_t ptm_bfd_gen_ID(void)
{
        uint32_t session_id;

        /*
         * RFC 5880, Section 6.8.1. recommends that we should generate
         * random session identification numbers.
         */
        do {
                session_id = ((random() << 16) & 0xFFFF0000)
                             | (random() & 0x0000FFFF);
        } while (session_id == 0 || bfd_id_lookup(session_id) != NULL);

        return session_id;
}

void ptm_bfd_start_xmt_timer(struct bfd_session *bfd, bool is_echo)
{
        uint64_t jitter, xmt_TO;
        int maxpercent;

        xmt_TO = is_echo ? bfd->echo_xmt_TO : bfd->xmt_TO;

        /*
         * From section 6.5.2: trasmit interval should be randomly jittered
         * between
         * 75% and 100% of nominal value, unless detect_mult is 1, then should
         * be
         * between 75% and 90%.
         */
        maxpercent = (bfd->detect_mult == 1) ? 16 : 26;
        jitter = (xmt_TO * (75 + (random() % maxpercent))) / 100;
        /* XXX remove that division above */

        if (is_echo)
                bfd_echo_xmttimer_update(bfd, jitter);
        else
                bfd_xmttimer_update(bfd, jitter);
}

static void ptm_bfd_echo_xmt_TO(struct bfd_session *bfd)
{
        /* Send the scheduled echo  packet */
        ptm_bfd_echo_snd(bfd);

        /* Restart the timer for next time */
        ptm_bfd_start_xmt_timer(bfd, true);
}

void ptm_bfd_xmt_TO(struct bfd_session *bfd, int fbit)
{
        /* Send the scheduled control packet */
        ptm_bfd_snd(bfd, fbit);

        /* Restart the timer for next time */
        ptm_bfd_start_xmt_timer(bfd, false);
}

void ptm_bfd_echo_stop(struct bfd_session *bfd)
{
        bfd->echo_xmt_TO = 0;
        bfd->echo_detect_TO = 0;
        BFD_UNSET_FLAG(bfd->flags, BFD_SESS_FLAG_ECHO_ACTIVE);

        bfd_echo_xmttimer_delete(bfd);
        bfd_echo_recvtimer_delete(bfd);
}

void ptm_bfd_echo_start(struct bfd_session *bfd)
{
        bfd->echo_detect_TO = (bfd->remote_detect_mult * bfd->echo_xmt_TO);
        if (bfd->echo_detect_TO > 0)
                ptm_bfd_echo_xmt_TO(bfd);
}

void ptm_bfd_sess_up(struct bfd_session *bfd)
{
        int old_state = bfd->ses_state;

        bfd->local_diag = 0;
        bfd->ses_state = PTM_BFD_UP;
        monotime(&bfd->uptime);

        /* Connection is up, lets negotiate timers. */
        bfd_set_polling(bfd);

        /* Start sending control packets with poll bit immediately. */
        ptm_bfd_snd(bfd, 0);

        control_notify(bfd, bfd->ses_state);

        if (old_state != bfd->ses_state) {
                bfd->stats.session_up++;
                log_info("state-change: [%s] %s -> %s", bs_to_string(bfd),
                         state_list[old_state].str,
                         state_list[bfd->ses_state].str);
        }
}

void ptm_bfd_sess_dn(struct bfd_session *bfd, uint8_t diag)
{
        int old_state = bfd->ses_state;

        bfd->local_diag = diag;
        bfd->discrs.remote_discr = 0;
        bfd->ses_state = PTM_BFD_DOWN;
        bfd->polling = 0;
        bfd->demand_mode = 0;
        monotime(&bfd->downtime);

        ptm_bfd_snd(bfd, 0);

        /* Slow down the control packets, the connection is down. */
        bs_set_slow_timers(bfd);

        /* only signal clients when going from up->down state */
        if (old_state == PTM_BFD_UP)
                control_notify(bfd, PTM_BFD_DOWN);

        /* Stop echo packet transmission if they are active */
        if (BFD_CHECK_FLAG(bfd->flags, BFD_SESS_FLAG_ECHO_ACTIVE))
                ptm_bfd_echo_stop(bfd);

        if (old_state != bfd->ses_state) {
                bfd->stats.session_down++;
                log_info("state-change: [%s] %s -> %s reason:%s",
                         bs_to_string(bfd), state_list[old_state].str,
                         state_list[bfd->ses_state].str,
                         get_diag_str(bfd->local_diag));
        }
}

static struct bfd_session *bfd_find_disc(struct sockaddr_any *sa,
                                         uint32_t ldisc)
{
        struct bfd_session *bs;

        bs = bfd_id_lookup(ldisc);
        if (bs == NULL)
                return NULL;

        switch (bs->key.family) {
        case AF_INET:
                if (memcmp(&sa->sa_sin.sin_addr, &bs->key.peer,
                           sizeof(sa->sa_sin.sin_addr)))
                        return NULL;
                break;
        case AF_INET6:
                if (memcmp(&sa->sa_sin6.sin6_addr, &bs->key.peer,
                           sizeof(sa->sa_sin6.sin6_addr)))
                        return NULL;
                break;
        }

        return bs;
}

struct bfd_session *ptm_bfd_sess_find(struct bfd_pkt *cp,
                                      struct sockaddr_any *peer,
                                      struct sockaddr_any *local,
                                      ifindex_t ifindex, vrf_id_t vrfid,
                                      bool is_mhop)
{
        struct interface *ifp;
        struct vrf *vrf;
        struct bfd_key key;

        /* Find our session using the ID signaled by the remote end. */
        if (cp->discrs.remote_discr)
                return bfd_find_disc(peer, ntohl(cp->discrs.remote_discr));

        /* Search for session without using discriminator. */
        ifp = if_lookup_by_index(ifindex, vrfid);

        vrf = vrf_lookup_by_id(vrfid);

        gen_bfd_key(&key, peer, local, is_mhop, ifp ? ifp->name : NULL,
                    vrf ? vrf->name : VRF_DEFAULT_NAME);

        /* XXX maybe remoteDiscr should be checked for remoteHeard cases. */
        return bfd_key_lookup(key);
}

int bfd_xmt_cb(struct thread *t)
{
        struct bfd_session *bs = THREAD_ARG(t);

        ptm_bfd_xmt_TO(bs, 0);

        return 0;
}

int bfd_echo_xmt_cb(struct thread *t)
{
        struct bfd_session *bs = THREAD_ARG(t);

        if (bs->echo_xmt_TO > 0)
                ptm_bfd_echo_xmt_TO(bs);

        return 0;
}

/* Was ptm_bfd_detect_TO() */
int bfd_recvtimer_cb(struct thread *t)
{
        struct bfd_session *bs = THREAD_ARG(t);

        switch (bs->ses_state) {
        case PTM_BFD_INIT:
        case PTM_BFD_UP:
                ptm_bfd_sess_dn(bs, BD_CONTROL_EXPIRED);
                bfd_recvtimer_update(bs);
                break;

        default:
                /* Second detect time expiration, zero remote discr (section
                 * 6.5.1)
                 */
                bs->discrs.remote_discr = 0;
                break;
        }

        return 0;
}

/* Was ptm_bfd_echo_detect_TO() */
int bfd_echo_recvtimer_cb(struct thread *t)
{
        struct bfd_session *bs = THREAD_ARG(t);

        switch (bs->ses_state) {
        case PTM_BFD_INIT:
        case PTM_BFD_UP:
                ptm_bfd_sess_dn(bs, BD_ECHO_FAILED);
                break;
        }

        return 0;
}

struct bfd_session *bfd_session_new(void)
{
        struct bfd_session *bs;

        bs = XCALLOC(MTYPE_BFDD_CONFIG, sizeof(*bs));

        bs->timers.desired_min_tx = BFD_DEFDESIREDMINTX;
        bs->timers.required_min_rx = BFD_DEFREQUIREDMINRX;
        bs->timers.required_min_echo = BFD_DEF_REQ_MIN_ECHO;
        bs->detect_mult = BFD_DEFDETECTMULT;
        bs->mh_ttl = BFD_DEF_MHOP_TTL;
        bs->ses_state = PTM_BFD_DOWN;

        /* Initiate connection with slow timers. */
        bs_set_slow_timers(bs);

        /* Initiate remote settings as well. */
        bs->remote_timers = bs->cur_timers;
        bs->remote_detect_mult = BFD_DEFDETECTMULT;

        bs->sock = -1;
        monotime(&bs->uptime);
        bs->downtime = bs->uptime;

        return bs;
}

int bfd_session_update_label(struct bfd_session *bs, const char *nlabel)
{
        /* New label treatment:
         * - Check if the label is taken;
         * - Try to allocate the memory for it and register;
         */
        if (bs->pl == NULL) {
                if (pl_find(nlabel) != NULL) {
                        /* Someone is already using it. */
                        return -1;
                }

                if (pl_new(nlabel, bs) == NULL)
                        return -1;

                return 0;
        }

        /*
         * Test label change consistency:
         * - Do nothing if it's the same label;
         * - Check if the future label is already taken;
         * - Change label;
         */
        if (strcmp(nlabel, bs->pl->pl_label) == 0)
                return -1;
        if (pl_find(nlabel) != NULL)
                return -1;

        strlcpy(bs->pl->pl_label, nlabel, sizeof(bs->pl->pl_label));
        return 0;
}

static void _bfd_session_update(struct bfd_session *bs,
                                struct bfd_peer_cfg *bpc)
{
        if (bpc->bpc_echo) {
                /* Check if echo mode is already active. */
                if (BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_ECHO))
                        goto skip_echo;

                BFD_SET_FLAG(bs->flags, BFD_SESS_FLAG_ECHO);

                /* Activate/update echo receive timeout timer. */
                bs_echo_timer_handler(bs);
        } else {
                /* Check if echo mode is already disabled. */
                if (!BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_ECHO))
                        goto skip_echo;

                BFD_UNSET_FLAG(bs->flags, BFD_SESS_FLAG_ECHO);
                ptm_bfd_echo_stop(bs);
        }

skip_echo:
        if (bpc->bpc_has_txinterval)
                bs->timers.desired_min_tx = bpc->bpc_txinterval * 1000;

        if (bpc->bpc_has_recvinterval)
                bs->timers.required_min_rx = bpc->bpc_recvinterval * 1000;

        if (bpc->bpc_has_detectmultiplier)
                bs->detect_mult = bpc->bpc_detectmultiplier;

        if (bpc->bpc_has_echointerval)
                bs->timers.required_min_echo = bpc->bpc_echointerval * 1000;

        if (bpc->bpc_has_label)
                bfd_session_update_label(bs, bpc->bpc_label);

        if (bpc->bpc_shutdown) {
                /* Check if already shutdown. */
                if (BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_SHUTDOWN))
                        return;

                BFD_SET_FLAG(bs->flags, BFD_SESS_FLAG_SHUTDOWN);

                /* Disable all events. */
                bfd_recvtimer_delete(bs);
                bfd_echo_recvtimer_delete(bs);
                bfd_xmttimer_delete(bs);
                bfd_echo_xmttimer_delete(bs);

                /* Change and notify state change. */
                bs->ses_state = PTM_BFD_ADM_DOWN;
                control_notify(bs, bs->ses_state);

                /* Don't try to send packets with a disabled session. */
                if (bs->sock != -1)
                        ptm_bfd_snd(bs, 0);
        } else {
                /* Check if already working. */
                if (!BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_SHUTDOWN))
                        return;

                BFD_UNSET_FLAG(bs->flags, BFD_SESS_FLAG_SHUTDOWN);

                /* Change and notify state change. */
                bs->ses_state = PTM_BFD_DOWN;
                control_notify(bs, bs->ses_state);

                /* Enable all timers. */
                bfd_recvtimer_update(bs);
                bfd_xmttimer_update(bs, bs->xmt_TO);
        }
        if (bpc->bpc_cbit) {
                if (BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_CBIT))
                        return;

                BFD_SET_FLAG(bs->flags, BFD_SESS_FLAG_CBIT);
        } else {
                if (!BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_CBIT))
                        return;

                BFD_UNSET_FLAG(bs->flags, BFD_SESS_FLAG_CBIT);
        }
}

static int bfd_session_update(struct bfd_session *bs, struct bfd_peer_cfg *bpc)
{
        /* User didn't want to update, return failure. */
        if (bpc->bpc_createonly)
                return -1;

        _bfd_session_update(bs, bpc);

        control_notify_config(BCM_NOTIFY_CONFIG_UPDATE, bs);

        return 0;
}

void bfd_session_free(struct bfd_session *bs)
{
        struct bfd_session_observer *bso;

        bfd_session_disable(bs);

        bfd_key_delete(bs->key);
        bfd_id_delete(bs->discrs.my_discr);

        /* Remove observer if any. */
        TAILQ_FOREACH(bso, &bglobal.bg_obslist, bso_entry) {
                if (bso->bso_bs != bs)
                        continue;

                break;
        }
        if (bso != NULL)
                bs_observer_del(bso);

        pl_free(bs->pl);

        XFREE(MTYPE_BFDD_CONFIG, bs);
}

struct bfd_session *ptm_bfd_sess_new(struct bfd_peer_cfg *bpc)
{
        struct bfd_session *bfd, *l_bfd;

        /* check to see if this needs a new session */
        l_bfd = bs_peer_find(bpc);
        if (l_bfd) {
                /* Requesting a duplicated peer means update configuration. */
                if (bfd_session_update(l_bfd, bpc) == 0)
                        return l_bfd;
                else
                        return NULL;
        }

        /* Get BFD session storage with its defaults. */
        bfd = bfd_session_new();
        if (bfd == NULL) {
                log_error("session-new: allocation failed");
                return NULL;
        }

        /*
         * Store interface/VRF name in case we need to delay session
         * start. See `bfd_session_enable` for more information.
         */
        if (bpc->bpc_has_localif)
                strlcpy(bfd->key.ifname, bpc->bpc_localif,
                        sizeof(bfd->key.ifname));

        if (bpc->bpc_has_vrfname)
                strlcpy(bfd->key.vrfname, bpc->bpc_vrfname,
                        sizeof(bfd->key.vrfname));
        else
                strlcpy(bfd->key.vrfname, VRF_DEFAULT_NAME,
                        sizeof(bfd->key.vrfname));

        /* Copy remaining data. */
        if (bpc->bpc_ipv4 == false)
                BFD_SET_FLAG(bfd->flags, BFD_SESS_FLAG_IPV6);

        bfd->key.family = (bpc->bpc_ipv4) ? AF_INET : AF_INET6;
        switch (bfd->key.family) {
        case AF_INET:
                memcpy(&bfd->key.peer, &bpc->bpc_peer.sa_sin.sin_addr,
                       sizeof(bpc->bpc_peer.sa_sin.sin_addr));
                memcpy(&bfd->key.local, &bpc->bpc_local.sa_sin.sin_addr,
                       sizeof(bpc->bpc_local.sa_sin.sin_addr));
                break;

        case AF_INET6:
                memcpy(&bfd->key.peer, &bpc->bpc_peer.sa_sin6.sin6_addr,
                       sizeof(bpc->bpc_peer.sa_sin6.sin6_addr));
                memcpy(&bfd->key.local, &bpc->bpc_local.sa_sin6.sin6_addr,
                       sizeof(bpc->bpc_local.sa_sin6.sin6_addr));
                break;

        default:
                assert(1);
                break;
        }

        if (bpc->bpc_mhop)
                BFD_SET_FLAG(bfd->flags, BFD_SESS_FLAG_MH);

        bfd->key.mhop = bpc->bpc_mhop;

        if (bs_registrate(bfd) == NULL)
                return NULL;

        /* Apply other configurations. */
        _bfd_session_update(bfd, bpc);

        return bfd;
}

struct bfd_session *bs_registrate(struct bfd_session *bfd)
{
        /* Registrate session into data structures. */
        bfd_key_insert(bfd);
        bfd->discrs.my_discr = ptm_bfd_gen_ID();
        bfd_id_insert(bfd);

        /* Try to enable session and schedule for packet receive/send. */
        if (bfd_session_enable(bfd) == -1) {
                /* Unrecoverable failure, remove the session/peer. */
                bfd_session_free(bfd);
                return NULL;
        }

        /* Add observer if we have moving parts. */
        if (bfd->key.ifname[0] || bfd->key.vrfname[0] || bfd->sock == -1)
                bs_observer_add(bfd);

        log_info("session-new: %s", bs_to_string(bfd));

        control_notify_config(BCM_NOTIFY_CONFIG_ADD, bfd);

        return bfd;
}

int ptm_bfd_sess_del(struct bfd_peer_cfg *bpc)
{
        struct bfd_session *bs;

        /* Find session and call free(). */
        bs = bs_peer_find(bpc);
        if (bs == NULL)
                return -1;

        /* This pointer is being referenced, don't let it be deleted. */
        if (bs->refcount > 0) {
                log_error("session-delete: refcount failure: %" PRIu64
                          " references",
                          bs->refcount);
                return -1;
        }

        log_info("session-delete: %s", bs_to_string(bs));

        control_notify_config(BCM_NOTIFY_CONFIG_DELETE, bs);

        bfd_session_free(bs);

        return 0;
}

void bfd_set_polling(struct bfd_session *bs)
{
        /*
         * Start polling procedure: the only timers that require polling
         * to change value without losing connection are:
         *
         *   - Desired minimum transmission interval;
         *   - Required minimum receive interval;
         *
         * RFC 5880, Section 6.8.3.
         */
        bs->polling = 1;
}

/*
 * bs_<state>_handler() functions implement the BFD state machine
 * transition mechanism. `<state>` is the current session state and
 * the parameter `nstate` is the peer new state.
 */
static void bs_admin_down_handler(struct bfd_session *bs
                                  __attribute__((__unused__)),
                                  int nstate __attribute__((__unused__)))
{
        /*
         * We are administratively down, there is no state machine
         * handling.
         */
}

static void bs_down_handler(struct bfd_session *bs, int nstate)
{
        switch (nstate) {
        case PTM_BFD_ADM_DOWN:
                /*
                 * Remote peer doesn't want to talk, so lets keep the
                 * connection down.
                 */
        case PTM_BFD_UP:
                /* Peer can't be up yet, wait it go to 'init' or 'down'. */
                break;

        case PTM_BFD_DOWN:
                /*
                 * Remote peer agreed that the path is down, lets try to
                 * bring it up.
                 */
                bs->ses_state = PTM_BFD_INIT;
                break;

        case PTM_BFD_INIT:
                /*
                 * Remote peer told us his path is up, lets turn
                 * activate the session.
                 */
                ptm_bfd_sess_up(bs);
                break;

        default:
                log_debug("state-change: unhandled neighbor state: %d", nstate);
                break;
        }
}

static void bs_init_handler(struct bfd_session *bs, int nstate)
{
        switch (nstate) {
        case PTM_BFD_ADM_DOWN:
                /*
                 * Remote peer doesn't want to talk, so lets make the
                 * connection down.
                 */
                bs->ses_state = PTM_BFD_DOWN;
                break;

        case PTM_BFD_DOWN:
                /* Remote peer hasn't moved to first stage yet. */
                break;

        case PTM_BFD_INIT:
        case PTM_BFD_UP:
                /* We agreed on the settings and the path is up. */
                ptm_bfd_sess_up(bs);
                break;

        default:
                log_debug("state-change: unhandled neighbor state: %d", nstate);
                break;
        }
}

static void bs_neighbour_admin_down_handler(struct bfd_session *bfd,
                                            uint8_t diag)
{
        int old_state = bfd->ses_state;

        bfd->local_diag = diag;
        bfd->discrs.remote_discr = 0;
        bfd->ses_state = PTM_BFD_DOWN;
        bfd->polling = 0;
        bfd->demand_mode = 0;
        monotime(&bfd->downtime);

        /* Slow down the control packets, the connection is down. */
        bs_set_slow_timers(bfd);

        /* only signal clients when going from up->down state */
        if (old_state == PTM_BFD_UP)
                control_notify(bfd, PTM_BFD_ADM_DOWN);

        /* Stop echo packet transmission if they are active */
        if (BFD_CHECK_FLAG(bfd->flags, BFD_SESS_FLAG_ECHO_ACTIVE))
                ptm_bfd_echo_stop(bfd);

        if (old_state != bfd->ses_state) {
                bfd->stats.session_down++;

                log_info("state-change: [%s] %s -> %s reason:%s",
                        bs_to_string(bfd), state_list[old_state].str,
                        state_list[bfd->ses_state].str,
                        get_diag_str(bfd->local_diag));
        }
}

static void bs_up_handler(struct bfd_session *bs, int nstate)
{
        switch (nstate) {
        case PTM_BFD_ADM_DOWN:
                bs_neighbour_admin_down_handler(bs, BD_ADMIN_DOWN);
                break;

        case PTM_BFD_DOWN:
                /* Peer lost or asked to shutdown connection. */
                ptm_bfd_sess_dn(bs, BD_NEIGHBOR_DOWN);
                break;

        case PTM_BFD_INIT:
        case PTM_BFD_UP:
                /* Path is up and working. */
                break;

        default:
                log_debug("state-change: unhandled neighbor state: %d", nstate);
                break;
        }
}

void bs_state_handler(struct bfd_session *bs, int nstate)
{
        switch (bs->ses_state) {
        case PTM_BFD_ADM_DOWN:
                bs_admin_down_handler(bs, nstate);
                break;
        case PTM_BFD_DOWN:
                bs_down_handler(bs, nstate);
                break;
        case PTM_BFD_INIT:
                bs_init_handler(bs, nstate);
                break;
        case PTM_BFD_UP:
                bs_up_handler(bs, nstate);
                break;

        default:
                log_debug("state-change: [%s] is in invalid state: %d",
                          bs_to_string(bs), nstate);
                break;
        }
}

/*
 * Handles echo timer manipulation after updating timer.
 */
void bs_echo_timer_handler(struct bfd_session *bs)
{
        uint32_t old_timer;

        /*
         * Before doing any echo handling, check if it is possible to
         * use it.
         *
         *   - Check for `echo-mode` configuration.
         *   - Check that we are not using multi hop (RFC 5883,
         *     Section 3).
         *   - Check that we are already at the up state.
         */
        if (BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_ECHO) == 0
            || BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_MH)
            || bs->ses_state != PTM_BFD_UP)
                return;

        /* Remote peer asked to stop echo. */
        if (bs->remote_timers.required_min_echo == 0) {
                if (BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_ECHO_ACTIVE))
                        ptm_bfd_echo_stop(bs);

                return;
        }

        /*
         * Calculate the echo transmission timer: we must not send
         * echo packets faster than the minimum required time
         * announced by the remote system.
         *
         * RFC 5880, Section 6.8.9.
         */
        old_timer = bs->echo_xmt_TO;
        if (bs->remote_timers.required_min_echo > bs->timers.required_min_echo)
                bs->echo_xmt_TO = bs->remote_timers.required_min_echo;
        else
                bs->echo_xmt_TO = bs->timers.required_min_echo;

        if (BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_ECHO_ACTIVE) == 0
            || old_timer != bs->echo_xmt_TO)
                ptm_bfd_echo_start(bs);
}

/*
 * RFC 5880 Section 6.5.
 *
 * When a BFD control packet with the final bit is received, we must
 * update the session parameters.
 */
void bs_final_handler(struct bfd_session *bs)
{
        /* Start using our new timers. */
        bs->cur_timers.desired_min_tx = bs->timers.desired_min_tx;
        bs->cur_timers.required_min_rx = bs->timers.required_min_rx;

        /*
         * TODO: demand mode. See RFC 5880 Section 6.1.
         *
         * When using demand mode we must disable the detection timer
         * for lost control packets.
         */
        if (bs->demand_mode) {
                /* Notify watchers about changed timers. */
                control_notify_config(BCM_NOTIFY_CONFIG_UPDATE, bs);
                return;
        }

        /*
         * Calculate detection time based on new timers.
         *
         * Transmission calculation:
         * We must respect the RequiredMinRxInterval from the remote
         * system: if our desired transmission timer is more than the
         * minimum receive rate, then we must lower it to at least the
         * minimum receive interval.
         *
         * RFC 5880, Section 6.8.3.
         */
        if (bs->timers.desired_min_tx > bs->remote_timers.required_min_rx)
                bs->xmt_TO = bs->remote_timers.required_min_rx;
        else
                bs->xmt_TO = bs->timers.desired_min_tx;

        /* Apply new transmission timer immediately. */
        ptm_bfd_start_xmt_timer(bs, false);

        /*
         * Detection timeout calculation:
         * The minimum detection timeout is the remote detection
         * multipler (number of packets to be missed) times the agreed
         * transmission interval.
         *
         * RFC 5880, Section 6.8.4.
         *
         * TODO: support sending/counting more packets inside detection
         * timeout.
         */
        if (bs->remote_timers.required_min_rx > bs->timers.desired_min_tx)
                bs->detect_TO = bs->remote_detect_mult
                                * bs->remote_timers.required_min_rx;
        else
                bs->detect_TO = bs->remote_detect_mult
                                * bs->timers.desired_min_tx;

        /* Apply new receive timer immediately. */
        bfd_recvtimer_update(bs);

        /* Notify watchers about changed timers. */
        control_notify_config(BCM_NOTIFY_CONFIG_UPDATE, bs);
}

void bs_set_slow_timers(struct bfd_session *bs)
{
        /*
         * BFD connection must use slow timers before going up or after
         * losing connectivity to avoid wasting bandwidth.
         *
         * RFC 5880, Section 6.8.3.
         */
        bs->cur_timers.desired_min_tx = BFD_DEF_SLOWTX;
        bs->cur_timers.required_min_rx = BFD_DEF_SLOWTX;
        bs->cur_timers.required_min_echo = 0;

        /* Set the appropriated timeouts for slow connection. */
        bs->detect_TO = (BFD_DEFDETECTMULT * BFD_DEF_SLOWTX);
        bs->xmt_TO = BFD_DEF_SLOWTX;
}

/*
 * Helper functions.
 */
static const char *get_diag_str(int diag)
{
        for (int i = 0; diag_list[i].str; i++) {
                if (diag_list[i].type == diag)
                        return diag_list[i].str;
        }
        return "N/A";
}

const char *satostr(struct sockaddr_any *sa)
{
#define INETSTR_BUFCOUNT 8
        static char buf[INETSTR_BUFCOUNT][INET6_ADDRSTRLEN];
        static int bufidx;
        struct sockaddr_in *sin = &sa->sa_sin;
        struct sockaddr_in6 *sin6 = &sa->sa_sin6;

        bufidx += (bufidx + 1) % INETSTR_BUFCOUNT;
        buf[bufidx][0] = 0;

        switch (sin->sin_family) {
        case AF_INET:
                inet_ntop(AF_INET, &sin->sin_addr, buf[bufidx],
                          sizeof(buf[bufidx]));
                break;
        case AF_INET6:
                inet_ntop(AF_INET6, &sin6->sin6_addr, buf[bufidx],
                          sizeof(buf[bufidx]));
                break;

        default:
                strlcpy(buf[bufidx], "unknown", sizeof(buf[bufidx]));
                break;
        }

        return buf[bufidx];
}

const char *diag2str(uint8_t diag)
{
        switch (diag) {
        case 0:
                return "ok";
        case 1:
                return "control detection time expired";
        case 2:
                return "echo function failed";
        case 3:
                return "neighbor signaled session down";
        case 4:
                return "forwarding plane reset";
        case 5:
                return "path down";
        case 6:
                return "concatenated path down";
        case 7:
                return "administratively down";
        case 8:
                return "reverse concatenated path down";
        default:
                return "unknown";
        }
}

int strtosa(const char *addr, struct sockaddr_any *sa)
{
        memset(sa, 0, sizeof(*sa));

        if (inet_pton(AF_INET, addr, &sa->sa_sin.sin_addr) == 1) {
                sa->sa_sin.sin_family = AF_INET;
#ifdef HAVE_STRUCT_SOCKADDR_SA_LEN
                sa->sa_sin.sin_len = sizeof(sa->sa_sin);
#endif /* HAVE_STRUCT_SOCKADDR_SA_LEN */
                return 0;
        }

        if (inet_pton(AF_INET6, addr, &sa->sa_sin6.sin6_addr) == 1) {
                sa->sa_sin6.sin6_family = AF_INET6;
#ifdef HAVE_STRUCT_SOCKADDR_SA_LEN
                sa->sa_sin6.sin6_len = sizeof(sa->sa_sin6);
#endif /* HAVE_STRUCT_SOCKADDR_SA_LEN */
                return 0;
        }

        return -1;
}

void integer2timestr(uint64_t time, char *buf, size_t buflen)
{
        unsigned int year, month, day, hour, minute, second;
        int rv;

#define MINUTES (60)
#define HOURS (60 * MINUTES)
#define DAYS (24 * HOURS)
#define MONTHS (30 * DAYS)
#define YEARS (12 * MONTHS)
        if (time >= YEARS) {
                year = time / YEARS;
                time -= year * YEARS;

                rv = snprintf(buf, buflen, "%u year(s), ", year);
                buf += rv;
                buflen -= rv;
        }
        if (time >= MONTHS) {
                month = time / MONTHS;
                time -= month * MONTHS;

                rv = snprintf(buf, buflen, "%u month(s), ", month);
                buf += rv;
                buflen -= rv;
        }
        if (time >= DAYS) {
                day = time / DAYS;
                time -= day * DAYS;

                rv = snprintf(buf, buflen, "%u day(s), ", day);
                buf += rv;
                buflen -= rv;
        }
        if (time >= HOURS) {
                hour = time / HOURS;
                time -= hour * HOURS;

                rv = snprintf(buf, buflen, "%u hour(s), ", hour);
                buf += rv;
                buflen -= rv;
        }
        if (time >= MINUTES) {
                minute = time / MINUTES;
                time -= minute * MINUTES;

                rv = snprintf(buf, buflen, "%u minute(s), ", minute);
                buf += rv;
                buflen -= rv;
        }
        second = time % MINUTES;
        snprintf(buf, buflen, "%u second(s)", second);
}

const char *bs_to_string(const struct bfd_session *bs)
{
        static char buf[256];
        char addr_buf[INET6_ADDRSTRLEN];
        int pos;
        bool is_mhop = BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_MH);

        pos = snprintf(buf, sizeof(buf), "mhop:%s", is_mhop ? "yes" : "no");
        pos += snprintf(buf + pos, sizeof(buf) - pos, " peer:%s",
                        inet_ntop(bs->key.family, &bs->key.peer, addr_buf,
                                  sizeof(addr_buf)));
        pos += snprintf(buf + pos, sizeof(buf) - pos, " local:%s",
                        inet_ntop(bs->key.family, &bs->key.local, addr_buf,
                                  sizeof(addr_buf)));
        if (bs->key.vrfname[0])
                pos += snprintf(buf + pos, sizeof(buf) - pos, " vrf:%s",
                                bs->key.vrfname);
        if (bs->key.ifname[0])
                pos += snprintf(buf + pos, sizeof(buf) - pos, " ifname:%s",
                                bs->key.ifname);

        (void)pos;

        return buf;
}

int bs_observer_add(struct bfd_session *bs)
{
        struct bfd_session_observer *bso;

        bso = XCALLOC(MTYPE_BFDD_SESSION_OBSERVER, sizeof(*bso));
        bso->bso_isaddress = false;
        bso->bso_bs = bs;
        bso->bso_isinterface = !BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_MH);
        if (bso->bso_isinterface)
                strlcpy(bso->bso_entryname, bs->key.ifname,
                        sizeof(bso->bso_entryname));
        /* Handle socket binding failures caused by missing local addresses. */
        if (bs->sock == -1) {
                bso->bso_isaddress = true;
                bso->bso_addr.family = bs->key.family;
                memcpy(&bso->bso_addr.u.prefix, &bs->key.local,
                       sizeof(bs->key.local));
        }

        TAILQ_INSERT_TAIL(&bglobal.bg_obslist, bso, bso_entry);

        return 0;
}

void bs_observer_del(struct bfd_session_observer *bso)
{
        TAILQ_REMOVE(&bglobal.bg_obslist, bso, bso_entry);
        XFREE(MTYPE_BFDD_SESSION_OBSERVER, bso);
}

void bs_to_bpc(struct bfd_session *bs, struct bfd_peer_cfg *bpc)
{
        memset(bpc, 0, sizeof(*bpc));

        bpc->bpc_ipv4 = (bs->key.family == AF_INET);
        bpc->bpc_mhop = bs->key.mhop;

        switch (bs->key.family) {
        case AF_INET:
                bpc->bpc_peer.sa_sin.sin_family = AF_INET;
                memcpy(&bpc->bpc_peer.sa_sin.sin_addr, &bs->key.peer,
                       sizeof(bpc->bpc_peer.sa_sin.sin_addr));

                if (memcmp(&bs->key.local, &zero_addr, sizeof(bs->key.local))) {
                        bpc->bpc_local.sa_sin.sin_family = AF_INET6;
                        memcpy(&bpc->bpc_local.sa_sin.sin_addr, &bs->key.local,
                               sizeof(bpc->bpc_local.sa_sin.sin_addr));
                }
                break;

        case AF_INET6:
                bpc->bpc_peer.sa_sin.sin_family = AF_INET6;
                memcpy(&bpc->bpc_peer.sa_sin6.sin6_addr, &bs->key.peer,
                       sizeof(bpc->bpc_peer.sa_sin6.sin6_addr));

                bpc->bpc_local.sa_sin6.sin6_family = AF_INET6;
                memcpy(&bpc->bpc_local.sa_sin6.sin6_addr, &bs->key.local,
                       sizeof(bpc->bpc_local.sa_sin6.sin6_addr));
                break;
        }

        if (bs->key.ifname[0]) {
                bpc->bpc_has_localif = true;
                strlcpy(bpc->bpc_localif, bs->key.ifname,
                        sizeof(bpc->bpc_localif));
        }

        if (bs->key.vrfname[0]) {
                bpc->bpc_has_vrfname = true;
                strlcpy(bpc->bpc_vrfname, bs->key.vrfname,
                        sizeof(bpc->bpc_vrfname));
        }
}


/*
 * BFD hash data structures to find sessions.
 */
static struct hash *bfd_id_hash;
static struct hash *bfd_key_hash;

static unsigned int bfd_id_hash_do(const void *p);
static unsigned int bfd_key_hash_do(const void *p);

static void _bfd_free(struct hash_bucket *hb,
                      void *arg __attribute__((__unused__)));

/* BFD hash for our discriminator. */
static unsigned int bfd_id_hash_do(const void *p)
{
        const struct bfd_session *bs = p;

        return jhash_1word(bs->discrs.my_discr, 0);
}

static bool bfd_id_hash_cmp(const void *n1, const void *n2)
{
        const struct bfd_session *bs1 = n1, *bs2 = n2;

        return bs1->discrs.my_discr == bs2->discrs.my_discr;
}

/* BFD hash for single hop. */
static unsigned int bfd_key_hash_do(const void *p)
{
        const struct bfd_session *bs = p;

        return jhash(&bs->key, sizeof(bs->key), 0);
}

static bool bfd_key_hash_cmp(const void *n1, const void *n2)
{
        const struct bfd_session *bs1 = n1, *bs2 = n2;

        return memcmp(&bs1->key, &bs2->key, sizeof(bs1->key)) == 0;
}


/*
 * Hash public interface / exported functions.
 */

/* Lookup functions. */
struct bfd_session *bfd_id_lookup(uint32_t id)
{
        struct bfd_session bs;

        bs.discrs.my_discr = id;

        return hash_lookup(bfd_id_hash, &bs);
}

struct bfd_key_walk_partial_lookup {
        struct bfd_session *given;
        struct bfd_session *result;
};

/* ignore some parameters */
static int bfd_key_lookup_ignore_partial_walker(struct hash_bucket *b,
                                                void *data)
{
        struct bfd_key_walk_partial_lookup *ctx =
                (struct bfd_key_walk_partial_lookup *)data;
        struct bfd_session *given = ctx->given;
        struct bfd_session *parsed = b->data;

        if (given->key.family != parsed->key.family)
                return HASHWALK_CONTINUE;
        if (given->key.mhop != parsed->key.mhop)
                return HASHWALK_CONTINUE;
        if (memcmp(&given->key.peer, &parsed->key.peer,
                   sizeof(struct in6_addr)))
                return HASHWALK_CONTINUE;
        if (memcmp(given->key.vrfname, parsed->key.vrfname, MAXNAMELEN))
                return HASHWALK_CONTINUE;
        ctx->result = parsed;
        /* ignore localaddr or interface */
        return HASHWALK_ABORT;
}

struct bfd_session *bfd_key_lookup(struct bfd_key key)
{
        struct bfd_session bs, *bsp;
        struct bfd_key_walk_partial_lookup ctx;
        char peer_buf[INET6_ADDRSTRLEN];

        bs.key = key;
        bsp = hash_lookup(bfd_key_hash, &bs);
        if (bsp)
                return bsp;

        inet_ntop(bs.key.family, &bs.key.peer, peer_buf,
                  sizeof(peer_buf));
        /* Handle cases where local-address is optional. */
        if (bs.key.family == AF_INET) {
                memset(&bs.key.local, 0, sizeof(bs.key.local));
                bsp = hash_lookup(bfd_key_hash, &bs);
                if (bsp) {
                        char addr_buf[INET6_ADDRSTRLEN];

                        inet_ntop(bs.key.family, &key.local, addr_buf,
                                  sizeof(addr_buf));
                        log_debug(" peer %s found, but loc-addr %s ignored",
                                  peer_buf, addr_buf);
                        return bsp;
                }
        }

        bs.key = key;
        /* Handle cases where ifname is optional. */
        if (bs.key.ifname[0]) {
                memset(bs.key.ifname, 0, sizeof(bs.key.ifname));
                bsp = hash_lookup(bfd_key_hash, &bs);
                if (bsp) {
                        log_debug(" peer %s found, but ifp %s ignored",
                                  peer_buf, key.ifname);
                        return bsp;
                }
        }

        /* Handle cases where local-address and ifname are optional. */
        if (bs.key.family == AF_INET) {
                memset(&bs.key.local, 0, sizeof(bs.key.local));
                bsp = hash_lookup(bfd_key_hash, &bs);
                if (bsp) {
                        char addr_buf[INET6_ADDRSTRLEN];

                        inet_ntop(bs.key.family, &bs.key.local, addr_buf,
                                  sizeof(addr_buf));
                        log_debug(" peer %s found, but ifp %s"
                                  " and loc-addr %s ignored",
                                  peer_buf, key.ifname,
                                  addr_buf);
                        return bsp;
                }
        }
        bs.key = key;

        /* Handle case where a context more complex ctx is present.
         * input has no iface nor local-address, but a context may
         * exist
         */
        ctx.result = NULL;
        ctx.given = &bs;
        hash_walk(bfd_key_hash,
                  &bfd_key_lookup_ignore_partial_walker,
                  &ctx);
        /* change key */
        if (ctx.result) {
                bsp = ctx.result;
                log_debug(" peer %s found, but ifp"
                          " and/or loc-addr params ignored");
        }
        return bsp;
}

/*
 * Delete functions.
 *
 * Delete functions searches and remove the item from the hash and
 * returns a pointer to the removed item data. If the item was not found
 * then it returns NULL.
 *
 * The data stored inside the hash is not free()ed, so you must do it
 * manually after getting the pointer back.
 */
struct bfd_session *bfd_id_delete(uint32_t id)
{
        struct bfd_session bs;

        bs.discrs.my_discr = id;

        return hash_release(bfd_id_hash, &bs);
}

struct bfd_session *bfd_key_delete(struct bfd_key key)
{
        struct bfd_session bs, *bsp;

        bs.key = key;
        bsp = hash_lookup(bfd_key_hash, &bs);
        if (bsp == NULL && key.ifname[0]) {
                memset(bs.key.ifname, 0, sizeof(bs.key.ifname));
                bsp = hash_lookup(bfd_key_hash, &bs);
        }

        return hash_release(bfd_key_hash, bsp);
}

/* Iteration functions. */
void bfd_id_iterate(hash_iter_func hif, void *arg)
{
        hash_iterate(bfd_id_hash, hif, arg);
}

void bfd_key_iterate(hash_iter_func hif, void *arg)
{
        hash_iterate(bfd_key_hash, hif, arg);
}

/*
 * Insert functions.
 *
 * Inserts session into hash and returns `true` on success, otherwise
 * `false`.
 */
bool bfd_id_insert(struct bfd_session *bs)
{
        return (hash_get(bfd_id_hash, bs, hash_alloc_intern) == bs);
}

bool bfd_key_insert(struct bfd_session *bs)
{
        return (hash_get(bfd_key_hash, bs, hash_alloc_intern) == bs);
}

void bfd_initialize(void)
{
        bfd_id_hash = hash_create(bfd_id_hash_do, bfd_id_hash_cmp,
                                  "BFD session discriminator hash");
        bfd_key_hash = hash_create(bfd_key_hash_do, bfd_key_hash_cmp,
                                   "BFD session hash");
}

static void _bfd_free(struct hash_bucket *hb,
                      void *arg __attribute__((__unused__)))
{
        struct bfd_session *bs = hb->data;

        bfd_session_free(bs);
}

void bfd_shutdown(void)
{
        /*
         * Close and free all BFD sessions.
         *
         * _bfd_free() will call bfd_session_free() which will take care
         * of removing the session from all hashes, so we just run an
         * assert() here to make sure it really happened.
         */
        bfd_id_iterate(_bfd_free, NULL);
        assert(bfd_key_hash->count == 0);

        /* Now free the hashes themselves. */
        hash_free(bfd_id_hash);
        hash_free(bfd_key_hash);
}

struct bfd_session_iterator {
        int bsi_stop;
        bool bsi_mhop;
        const struct bfd_session *bsi_bs;
};

static int _bfd_session_next(struct hash_bucket *hb, void *arg)
{
        struct bfd_session_iterator *bsi = arg;
        struct bfd_session *bs = hb->data;

        /* Previous entry signaled stop. */
        if (bsi->bsi_stop == 1) {
                /* Match the single/multi hop sessions. */
                if (bs->key.mhop != bsi->bsi_mhop)
                        return HASHWALK_CONTINUE;

                bsi->bsi_bs = bs;
                return HASHWALK_ABORT;
        }

        /* We found the current item, stop in the next one. */
        if (bsi->bsi_bs == hb->data) {
                bsi->bsi_stop = 1;
                /* Set entry to NULL to signal end of list. */
                bsi->bsi_bs = NULL;
        } else if (bsi->bsi_bs == NULL && bsi->bsi_mhop == bs->key.mhop) {
                /* We want the first list item. */
                bsi->bsi_stop = 1;
                bsi->bsi_bs = hb->data;
                return HASHWALK_ABORT;
        }

        return HASHWALK_CONTINUE;
}

/*
 * bfd_session_next: uses the current session to find the next.
 *
 * `bs` might point to NULL to get the first item of the data structure.
 */
const struct bfd_session *bfd_session_next(const struct bfd_session *bs,
                                           bool mhop)
{
        struct bfd_session_iterator bsi;

        bsi.bsi_stop = 0;
        bsi.bsi_bs = bs;
        bsi.bsi_mhop = mhop;
        hash_walk(bfd_key_hash, _bfd_session_next, &bsi);
        if (bsi.bsi_stop == 0)
                return NULL;

        return bsi.bsi_bs;
}

static void _bfd_session_remove_manual(struct hash_bucket *hb,
                                       void *arg __attribute__((__unused__)))
{
        struct bfd_session *bs = hb->data;

        /* Delete only manually configured sessions. */
        if (BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_CONFIG) == 0)
                return;

        bs->refcount--;
        BFD_UNSET_FLAG(bs->flags, BFD_SESS_FLAG_CONFIG);

        /* Don't delete sessions still in use. */
        if (bs->refcount != 0)
                return;

        bfd_session_free(bs);
}

/*
 * bfd_sessions_remove_manual: remove all manually configured sessions.
 *
 * NOTE: this function doesn't remove automatically created sessions.
 */
void bfd_sessions_remove_manual(void)
{
        hash_iterate(bfd_key_hash, _bfd_session_remove_manual, NULL);
}

/*
 * VRF related functions.
 */
static int bfd_vrf_new(struct vrf *vrf)
{
        log_debug("VRF Created: %s(%u)", vrf->name, vrf->vrf_id);
        return 0;
}

static int bfd_vrf_delete(struct vrf *vrf)
{
        log_debug("VRF Deletion: %s(%u)", vrf->name, vrf->vrf_id);
        return 0;
}

static int bfd_vrf_update(struct vrf *vrf)
{
        if (!vrf_is_enabled(vrf))
                return 0;
        log_debug("VRF update: %s(%u)", vrf->name, vrf->vrf_id);
        /* a different name is given; update bfd list */
        bfdd_sessions_enable_vrf(vrf);
        return 0;
}

static int bfd_vrf_enable(struct vrf *vrf)
{
        struct bfd_vrf_global *bvrf;

        /* a different name */
        if (!vrf->info) {
                bvrf = XCALLOC(MTYPE_BFDD_VRF, sizeof(struct bfd_vrf_global));
                bvrf->vrf = vrf;
                vrf->info = (void *)bvrf;
        } else
                bvrf = vrf->info;
        log_debug("VRF enable add %s id %u", vrf->name, vrf->vrf_id);
        if (vrf->vrf_id == VRF_DEFAULT ||
            vrf_get_backend() == VRF_BACKEND_NETNS) {
                if (!bvrf->bg_shop)
                        bvrf->bg_shop = bp_udp_shop(vrf->vrf_id);
                if (!bvrf->bg_mhop)
                        bvrf->bg_mhop = bp_udp_mhop(vrf->vrf_id);
                if (!bvrf->bg_shop6)
                        bvrf->bg_shop6 = bp_udp6_shop(vrf->vrf_id);
                if (!bvrf->bg_mhop6)
                        bvrf->bg_mhop6 = bp_udp6_mhop(vrf->vrf_id);
                if (!bvrf->bg_echo)
                        bvrf->bg_echo = bp_echo_socket(vrf->vrf_id);
                if (!bvrf->bg_echov6)
                        bvrf->bg_echov6 = bp_echov6_socket(vrf->vrf_id);

                /* Add descriptors to the event loop. */
                if (!bvrf->bg_ev[0])
                        thread_add_read(master, bfd_recv_cb, bvrf, bvrf->bg_shop,
                                        &bvrf->bg_ev[0]);
                if (!bvrf->bg_ev[1])
                        thread_add_read(master, bfd_recv_cb, bvrf, bvrf->bg_mhop,
                                        &bvrf->bg_ev[1]);
                if (!bvrf->bg_ev[2])
                        thread_add_read(master, bfd_recv_cb, bvrf, bvrf->bg_shop6,
                                        &bvrf->bg_ev[2]);
                if (!bvrf->bg_ev[3])
                        thread_add_read(master, bfd_recv_cb, bvrf, bvrf->bg_mhop6,
                                        &bvrf->bg_ev[3]);
                if (!bvrf->bg_ev[4])
                        thread_add_read(master, bfd_recv_cb, bvrf, bvrf->bg_echo,
                                        &bvrf->bg_ev[4]);
                if (!bvrf->bg_ev[5])
                        thread_add_read(master, bfd_recv_cb, bvrf, bvrf->bg_echov6,
                                        &bvrf->bg_ev[5]);
        }
        if (vrf->vrf_id != VRF_DEFAULT) {
                bfdd_zclient_register(vrf->vrf_id);
                bfdd_sessions_enable_vrf(vrf);
        }
        return 0;
}

static int bfd_vrf_disable(struct vrf *vrf)
{
        struct bfd_vrf_global *bvrf;

        if (!vrf->info)
                return 0;
        bvrf = vrf->info;

        if (vrf->vrf_id != VRF_DEFAULT) {
                bfdd_sessions_disable_vrf(vrf);
                bfdd_zclient_unregister(vrf->vrf_id);
        }

        log_debug("VRF disable %s id %d", vrf->name, vrf->vrf_id);
        /* Close all descriptors. */
        socket_close(&bvrf->bg_echo);
        socket_close(&bvrf->bg_shop);
        socket_close(&bvrf->bg_mhop);
        socket_close(&bvrf->bg_shop6);
        socket_close(&bvrf->bg_mhop6);
        socket_close(&bvrf->bg_echo);
        socket_close(&bvrf->bg_echov6);

        /* free context */
        XFREE(MTYPE_BFDD_VRF, bvrf);
        vrf->info = NULL;

        return 0;
}

void bfd_vrf_init(void)
{
        vrf_init(bfd_vrf_new, bfd_vrf_enable, bfd_vrf_disable,
                 bfd_vrf_delete, bfd_vrf_update);
}

void bfd_vrf_terminate(void)
{
        vrf_terminate();
}

struct bfd_vrf_global *bfd_vrf_look_by_session(struct bfd_session *bfd)
{
        struct vrf *vrf;

        if (!vrf_is_backend_netns()) {
                vrf = vrf_lookup_by_id(VRF_DEFAULT);
                if (vrf)
                        return (struct bfd_vrf_global *)vrf->info;
                return NULL;
        }
        if (!bfd)
                return NULL;
        if (!bfd->vrf)
                return NULL;
        return bfd->vrf->info;
}

void bfd_session_update_vrf_name(struct bfd_session *bs, struct vrf *vrf)
{
        if (!vrf || !bs)
                return;
        /* update key */
        hash_release(bfd_key_hash, bs);
        /*
         * HACK: Change the BFD VRF in the running configuration directly,
         * bypassing the northbound layer. This is necessary to avoid deleting
         * the BFD and readding it in the new VRF, which would have
         * several implications.
         */
        if (yang_module_find("frr-bfdd") && bs->key.vrfname[0]) {
                struct lyd_node *bfd_dnode;
                char xpath[XPATH_MAXLEN], xpath_srcaddr[XPATH_MAXLEN + 32];
                char addr_buf[INET6_ADDRSTRLEN];
                int slen;

                /* build xpath */
                if (bs->key.mhop) {
                        inet_ntop(bs->key.family, &bs->key.local, addr_buf, sizeof(addr_buf));
                        snprintf(xpath_srcaddr, sizeof(xpath_srcaddr), "[source-addr='%s']",
                                 addr_buf);
                } else
                        xpath_srcaddr[0] = 0;
                inet_ntop(bs->key.family, &bs->key.peer, addr_buf, sizeof(addr_buf));
                slen = snprintf(xpath, sizeof(xpath),
                                "/frr-bfdd:bfdd/bfd/sessions/%s%s[dest-addr='%s']",
                                bs->key.mhop ? "multi-hop" : "single-hop", xpath_srcaddr,
                                addr_buf);
                if (bs->key.ifname[0])
                        slen += snprintf(xpath + slen, sizeof(xpath) - slen,
                                         "[interface='%s']", bs->key.ifname);
                else
                        slen += snprintf(xpath + slen, sizeof(xpath) - slen,
                                         "[interface='']");
                snprintf(xpath + slen, sizeof(xpath) - slen, "[vrf='%s']/vrf",
                         bs->key.vrfname);

                pthread_rwlock_wrlock(&running_config->lock);
                {
                        bfd_dnode = yang_dnode_get(
                                                   running_config->dnode,
                                                   xpath, bs->key.vrfname);
                        if (bfd_dnode) {
                                yang_dnode_change_leaf(bfd_dnode, vrf->name);
                                running_config->version++;
                        }
                        pthread_rwlock_unlock(&running_config->lock);
                }
        }
        memset(bs->key.vrfname, 0, sizeof(bs->key.vrfname));
        strlcpy(bs->key.vrfname, vrf->name, sizeof(bs->key.vrfname));
        hash_get(bfd_key_hash, bs, hash_alloc_intern);
}