frr/lib/bfd.c

/**
 * bfd.c: BFD handling routines
 *
 * @copyright Copyright (C) 2015 Cumulus Networks, Inc.
 *
 * This file is part of GNU Zebra.
 *
 * GNU Zebra 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, or (at your option) any
 * later version.
 *
 * GNU Zebra 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
 */

#include <zebra.h>

#include "command.h"
#include "memory.h"
#include "prefix.h"
#include "thread.h"
#include "stream.h"
#include "vrf.h"
#include "zclient.h"
#include "libfrr.h"
#include "table.h"
#include "vty.h"
#include "bfd.h"

DEFINE_MTYPE_STATIC(LIB, BFD_INFO, "BFD info");
DEFINE_MTYPE_STATIC(LIB, BFD_SOURCE, "BFD source cache");

/**
 * BFD protocol integration configuration.
 */

/** Events definitions. */
enum bfd_session_event {
	/** Remove the BFD session configuration. */
	BSE_UNINSTALL,
	/** Install the BFD session configuration. */
	BSE_INSTALL,
};

/**
 * BFD source selection result cache.
 *
 * This structure will keep track of the result based on the destination
 * prefix. When the result changes all related BFD sessions with automatic
 * source will be updated.
 */
struct bfd_source_cache {
	/** Address VRF belongs. */
	vrf_id_t vrf_id;
	/** Destination network address. */
	struct prefix address;
	/** Source selected. */
	struct prefix source;
	/** Is the source address valid? */
	bool valid;
	/** BFD sessions using this. */
	size_t refcount;

	SLIST_ENTRY(bfd_source_cache) entry;
};
SLIST_HEAD(bfd_source_list, bfd_source_cache);

/**
 * Data structure to do the necessary tricks to hide the BFD protocol
 * integration internals.
 */
struct bfd_session_params {
	/** Contains the session parameters and more. */
	struct bfd_session_arg args;
	/** Contains the session state. */
	struct bfd_session_status bss;
	/** Protocol implementation status update callback. */
	bsp_status_update updatecb;
	/** Protocol implementation custom data pointer. */
	void *arg;

	/**
	 * Next event.
	 *
	 * This variable controls what action to execute when the command batch
	 * finishes. Normally we'd use `thread_add_event` value, however since
	 * that function is going to be called multiple times and the value
	 * might be different we'll use this variable to keep track of it.
	 */
	enum bfd_session_event lastev;
	/**
	 * BFD session configuration event.
	 *
	 * Multiple actions might be asked during a command batch (either via
	 * configuration load or northbound batch), so we'll use this to
	 * install/uninstall the BFD session parameters only once.
	 */
	struct thread *installev;

	/** BFD session installation state. */
	bool installed;

	/** Automatic source selection. */
	bool auto_source;
	/** Currently selected source. */
	struct bfd_source_cache *source_cache;

	/** Global BFD paramaters list. */
	TAILQ_ENTRY(bfd_session_params) entry;
};

struct bfd_sessions_global {
	/**
	 * Global BFD session parameters list for (re)installation and update
	 * without code duplication among daemons.
	 */
	TAILQ_HEAD(bsplist, bfd_session_params) bsplist;
	/** BFD automatic source selection cache. */
	struct bfd_source_list source_list;

	/** Pointer to FRR's event manager. */
	struct thread_master *tm;
	/** Pointer to zebra client data structure. */
	struct zclient *zc;

	/** Debugging state. */
	bool debugging;
	/** Is shutting down? */
	bool shutting_down;
};

/** Global configuration variable. */
static struct bfd_sessions_global bsglobal;

/** Global empty address for IPv4/IPv6. */
static const struct in6_addr i6a_zero;

/*
 * Prototypes
 */

static void bfd_source_cache_get(struct bfd_session_params *session);
static void bfd_source_cache_put(struct bfd_session_params *session);

static inline void
bfd_source_cache_register(const struct bfd_source_cache *source)
{
	zclient_send_rnh(bsglobal.zc, ZEBRA_NEXTHOP_REGISTER, &source->address,
			 SAFI_UNICAST, false, false, source->vrf_id);
}

static inline void
bfd_source_cache_unregister(const struct bfd_source_cache *source)
{
	zclient_send_rnh(bsglobal.zc, ZEBRA_NEXTHOP_UNREGISTER,
			 &source->address, SAFI_UNICAST, false, false,
			 source->vrf_id);
}


/*
 * bfd_get_peer_info - Extract the Peer information for which the BFD session
 *                     went down from the message sent from Zebra to clients.
 */
static struct interface *bfd_get_peer_info(struct stream *s, struct prefix *dp,
					   struct prefix *sp, int *status,
					   int *remote_cbit, vrf_id_t vrf_id)
{
	unsigned int ifindex;
	struct interface *ifp = NULL;
	int plen;
	int local_remote_cbit;

	/*
	 * If the ifindex lookup fails the
	 * rest of the data in the stream is
	 * not read.  All examples of this function
	 * call immediately use the dp->family which
	 * is not good.  Ensure we are not using
	 * random data
	 */
	memset(dp, 0, sizeof(*dp));
	memset(sp, 0, sizeof(*sp));

	/* Get interface index. */
	STREAM_GETL(s, ifindex);

	/* Lookup index. */
	if (ifindex != 0) {
		ifp = if_lookup_by_index(ifindex, vrf_id);
		if (ifp == NULL) {
			if (bsglobal.debugging)
				zlog_debug(
					"%s: Can't find interface by ifindex: %d ",
					__func__, ifindex);
			return NULL;
		}
	}

	/* Fetch destination address. */
	STREAM_GETC(s, dp->family);

	plen = prefix_blen(dp);
	STREAM_GET(&dp->u.prefix, s, plen);
	STREAM_GETC(s, dp->prefixlen);

	/* Get BFD status. */
	STREAM_GETL(s, (*status));

	STREAM_GETC(s, sp->family);

	plen = prefix_blen(sp);
	STREAM_GET(&sp->u.prefix, s, plen);
	STREAM_GETC(s, sp->prefixlen);

	STREAM_GETC(s, local_remote_cbit);
	if (remote_cbit)
		*remote_cbit = local_remote_cbit;
	return ifp;

stream_failure:
	/*
	 * Clean dp and sp because caller
	 * will immediately check them valid or not
	 */
	memset(dp, 0, sizeof(*dp));
	memset(sp, 0, sizeof(*sp));
	return NULL;
}

/*
 * bfd_get_status_str - Convert BFD status to a display string.
 */
const char *bfd_get_status_str(int status)
{
	switch (status) {
	case BFD_STATUS_DOWN:
		return "Down";
	case BFD_STATUS_UP:
		return "Up";
	case BFD_STATUS_ADMIN_DOWN:
		return "Admin Down";
	case BFD_STATUS_UNKNOWN:
	default:
		return "Unknown";
	}
}

/*
 * bfd_last_update - Calculate the last BFD update time and convert it
 *                   into a dd:hh:mm:ss display format.
 */
static void bfd_last_update(time_t last_update, char *buf, size_t len)
{
	time_t curr;
	time_t diff;
	struct tm tm;
	struct timeval tv;

	/* If no BFD status update has ever been received, print `never'. */
	if (last_update == 0) {
		snprintf(buf, len, "never");
		return;
	}

	/* Get current time. */
	monotime(&tv);
	curr = tv.tv_sec;
	diff = curr - last_update;
	gmtime_r(&diff, &tm);

	snprintf(buf, len, "%d:%02d:%02d:%02d", tm.tm_yday, tm.tm_hour,
		 tm.tm_min, tm.tm_sec);
}

/*
 * bfd_client_sendmsg - Format and send a client register
 *                    command to Zebra to be forwarded to BFD
 */
void bfd_client_sendmsg(struct zclient *zclient, int command,
			vrf_id_t vrf_id)
{
	struct stream *s;
	enum zclient_send_status ret;

	/* Check socket. */
	if (!zclient || zclient->sock < 0) {
		if (bsglobal.debugging)
			zlog_debug(
				"%s: Can't send BFD client register, Zebra client not established",
				__func__);
		return;
	}

	s = zclient->obuf;
	stream_reset(s);
	zclient_create_header(s, command, vrf_id);

	stream_putl(s, getpid());

	stream_putw_at(s, 0, stream_get_endp(s));

	ret = zclient_send_message(zclient);

	if (ret == ZCLIENT_SEND_FAILURE) {
		if (bsglobal.debugging)
			zlog_debug(
				"%s:  %ld: zclient_send_message() failed",
				__func__, (long)getpid());
		return;
	}

	return;
}

int zclient_bfd_command(struct zclient *zc, struct bfd_session_arg *args)
{
	struct stream *s;
	size_t addrlen;

	/* Individual reg/dereg messages are suppressed during shutdown. */
	if (bsglobal.shutting_down) {
		if (bsglobal.debugging)
			zlog_debug(
				"%s: Suppressing BFD peer reg/dereg messages",
				__func__);
		return -1;
	}

	/* Check socket. */
	if (!zc || zc->sock < 0) {
		if (bsglobal.debugging)
			zlog_debug("%s: zclient unavailable", __func__);
		return -1;
	}

	s = zc->obuf;
	stream_reset(s);

	/* Create new message. */
	zclient_create_header(s, args->command, args->vrf_id);
	stream_putl(s, getpid());

	/* Encode destination address. */
	stream_putw(s, args->family);
	addrlen = (args->family == AF_INET) ? sizeof(struct in_addr)
					    : sizeof(struct in6_addr);
	stream_put(s, &args->dst, addrlen);

	/*
	 * For more BFD integration protocol details, see function
	 * `_ptm_msg_read` in `bfdd/ptm_adapter.c`.
	 */
#if HAVE_BFDD > 0
	/* Session timers. */
	stream_putl(s, args->min_rx);
	stream_putl(s, args->min_tx);
	stream_putc(s, args->detection_multiplier);

	/* Is multi hop? */
	stream_putc(s, args->mhop != 0);

	/* Source address. */
	stream_putw(s, args->family);
	stream_put(s, &args->src, addrlen);

	/* Send the expected hops. */
	stream_putc(s, args->hops);

	/* Send interface name if any. */
	if (args->mhop) {
		/* Don't send interface. */
		stream_putc(s, 0);
		if (bsglobal.debugging && args->ifnamelen)
			zlog_debug("%s: multi hop is configured, not sending interface",
				   __func__);
	} else {
		stream_putc(s, args->ifnamelen);
		if (args->ifnamelen)
			stream_put(s, args->ifname, args->ifnamelen);
	}

	/* Send the C bit indicator. */
	stream_putc(s, args->cbit);

	/* Send profile name if any. */
	stream_putc(s, args->profilelen);
	if (args->profilelen)
		stream_put(s, args->profile, args->profilelen);
#else /* PTM BFD */
	/* Encode timers if this is a registration message. */
	if (args->command != ZEBRA_BFD_DEST_DEREGISTER) {
		stream_putl(s, args->min_rx);
		stream_putl(s, args->min_tx);
		stream_putc(s, args->detection_multiplier);
	}

	if (args->mhop) {
		/* Multi hop indicator. */
		stream_putc(s, 1);

		/* Multi hop always sends the source address. */
		stream_putw(s, args->family);
		stream_put(s, &args->src, addrlen);

		/* Send the expected hops. */
		stream_putc(s, args->hops);
	} else {
		/* Multi hop indicator. */
		stream_putc(s, 0);

		/* Single hop only sends the source address when IPv6. */
		if (args->family == AF_INET6) {
			stream_putw(s, args->family);
			stream_put(s, &args->src, addrlen);
		}

		/* Send interface name if any. */
		stream_putc(s, args->ifnamelen);
		if (args->ifnamelen)
			stream_put(s, args->ifname, args->ifnamelen);
	}

	/* Send the C bit indicator. */
	stream_putc(s, args->cbit);
#endif /* HAVE_BFDD */

	/* Finish the message by writing the size. */
	stream_putw_at(s, 0, stream_get_endp(s));

	/* Send message to zebra. */
	if (zclient_send_message(zc) == ZCLIENT_SEND_FAILURE) {
		if (bsglobal.debugging)
			zlog_debug("%s: zclient_send_message failed", __func__);
		return -1;
	}

	return 0;
}

struct bfd_session_params *bfd_sess_new(bsp_status_update updatecb, void *arg)
{
	struct bfd_session_params *bsp;

	bsp = XCALLOC(MTYPE_BFD_INFO, sizeof(*bsp));

	/* Save application data. */
	bsp->updatecb = updatecb;
	bsp->arg = arg;

	/* Set defaults. */
	bsp->args.detection_multiplier = BFD_DEF_DETECT_MULT;
	bsp->args.hops = 1;
	bsp->args.min_rx = BFD_DEF_MIN_RX;
	bsp->args.min_tx = BFD_DEF_MIN_TX;
	bsp->args.vrf_id = VRF_DEFAULT;

	/* Register in global list. */
	TAILQ_INSERT_TAIL(&bsglobal.bsplist, bsp, entry);

	return bsp;
}

static bool _bfd_sess_valid(const struct bfd_session_params *bsp)
{
	/* Peer/local address not configured. */
	if (bsp->args.family == 0)
		return false;

	/* Address configured but invalid. */
	if (bsp->args.family != AF_INET && bsp->args.family != AF_INET6) {
		if (bsglobal.debugging)
			zlog_debug("%s: invalid session family: %d", __func__,
				   bsp->args.family);
		return false;
	}

	/* Invalid address. */
	if (memcmp(&bsp->args.dst, &i6a_zero, sizeof(i6a_zero)) == 0) {
		if (bsglobal.debugging) {
			if (bsp->args.family == AF_INET)
				zlog_debug("%s: invalid address: %pI4",
					   __func__,
					   (struct in_addr *)&bsp->args.dst);
			else
				zlog_debug("%s: invalid address: %pI6",
					   __func__, &bsp->args.dst);
		}
		return false;
	}

	/* Multi hop requires local address. */
	if (bsp->args.mhop
	    && memcmp(&i6a_zero, &bsp->args.src, sizeof(i6a_zero)) == 0) {
		if (bsglobal.debugging)
			zlog_debug(
				"%s: multi hop but no local address provided",
				__func__);
		return false;
	}

	/* Check VRF ID. */
	if (bsp->args.vrf_id == VRF_UNKNOWN) {
		if (bsglobal.debugging)
			zlog_debug("%s: asked for unknown VRF", __func__);
		return false;
	}

	return true;
}

static void _bfd_sess_send(struct thread *t)
{
	struct bfd_session_params *bsp = THREAD_ARG(t);
	int rv;

	/* Validate configuration before trying to send bogus data. */
	if (!_bfd_sess_valid(bsp))
		return;

	if (bsp->lastev == BSE_INSTALL) {
		bsp->args.command = bsp->installed ? ZEBRA_BFD_DEST_UPDATE
						   : ZEBRA_BFD_DEST_REGISTER;
	} else
		bsp->args.command = ZEBRA_BFD_DEST_DEREGISTER;

	/* If not installed and asked for uninstall, do nothing. */
	if (!bsp->installed && bsp->args.command == ZEBRA_BFD_DEST_DEREGISTER)
		return;

	rv = zclient_bfd_command(bsglobal.zc, &bsp->args);
	/* Command was sent successfully. */
	if (rv == 0) {
		/* Update installation status. */
		if (bsp->args.command == ZEBRA_BFD_DEST_DEREGISTER)
			bsp->installed = false;
		else if (bsp->args.command == ZEBRA_BFD_DEST_REGISTER)
			bsp->installed = true;
	} else {
		struct ipaddr src, dst;

		src.ipa_type = bsp->args.family;
		src.ipaddr_v6 = bsp->args.src;
		dst.ipa_type = bsp->args.family;
		dst.ipaddr_v6 = bsp->args.dst;

		zlog_err(
			"%s: BFD session %pIA -> %pIA interface %s VRF %s(%u) was not %s",
			__func__, &src, &dst,
			bsp->args.ifnamelen ? bsp->args.ifname : "*",
			vrf_id_to_name(bsp->args.vrf_id), bsp->args.vrf_id,
			bsp->lastev == BSE_INSTALL ? "installed"
						   : "uninstalled");
	}
}

static void _bfd_sess_remove(struct bfd_session_params *bsp)
{
	/* Not installed, nothing to do. */
	if (!bsp->installed)
		return;

	/* Cancel any pending installation request. */
	THREAD_OFF(bsp->installev);

	/* Send request to remove any session. */
	bsp->lastev = BSE_UNINSTALL;
	thread_execute(bsglobal.tm, _bfd_sess_send, bsp, 0);
}

void bfd_sess_free(struct bfd_session_params **bsp)
{
	if (*bsp == NULL)
		return;

	/* Remove any installed session. */
	_bfd_sess_remove(*bsp);

	/* Remove from global list. */
	TAILQ_REMOVE(&bsglobal.bsplist, (*bsp), entry);

	bfd_source_cache_put(*bsp);

	/* Free the memory and point to NULL. */
	XFREE(MTYPE_BFD_INFO, (*bsp));
}

static bool bfd_sess_address_changed(const struct bfd_session_params *bsp,
				     uint32_t family,
				     const struct in6_addr *src,
				     const struct in6_addr *dst)
{
	size_t addrlen;

	if (bsp->args.family != family)
		return true;

	addrlen = (family == AF_INET) ? sizeof(struct in_addr)
				      : sizeof(struct in6_addr);
	if ((src == NULL && memcmp(&bsp->args.src, &i6a_zero, addrlen))
	    || (src && memcmp(src, &bsp->args.src, addrlen))
	    || memcmp(dst, &bsp->args.dst, addrlen))
		return true;

	return false;
}

void bfd_sess_set_ipv4_addrs(struct bfd_session_params *bsp,
			     const struct in_addr *src,
			     const struct in_addr *dst)
{
	if (!bfd_sess_address_changed(bsp, AF_INET, (struct in6_addr *)src,
				      (struct in6_addr *)dst))
		return;

	/* If already installed, remove the old setting. */
	_bfd_sess_remove(bsp);
	/* Address changed so we must reapply auto source. */
	bfd_source_cache_put(bsp);

	bsp->args.family = AF_INET;

	/* Clean memory, set zero value and avoid static analyser warnings. */
	memset(&bsp->args.src, 0, sizeof(bsp->args.src));
	memset(&bsp->args.dst, 0, sizeof(bsp->args.dst));

	/* Copy the equivalent of IPv4 to arguments structure. */
	if (src)
		memcpy(&bsp->args.src, src, sizeof(struct in_addr));

	assert(dst);
	memcpy(&bsp->args.dst, dst, sizeof(struct in_addr));

	if (bsp->auto_source)
		bfd_source_cache_get(bsp);
}

void bfd_sess_set_ipv6_addrs(struct bfd_session_params *bsp,
			     const struct in6_addr *src,
			     const struct in6_addr *dst)
{
	if (!bfd_sess_address_changed(bsp, AF_INET6, src, dst))
		return;

	/* If already installed, remove the old setting. */
	_bfd_sess_remove(bsp);
	/* Address changed so we must reapply auto source. */
	bfd_source_cache_put(bsp);

	bsp->args.family = AF_INET6;

	/* Clean memory, set zero value and avoid static analyser warnings. */
	memset(&bsp->args.src, 0, sizeof(bsp->args.src));

	if (src)
		bsp->args.src = *src;

	assert(dst);
	bsp->args.dst = *dst;

	if (bsp->auto_source)
		bfd_source_cache_get(bsp);
}

void bfd_sess_set_interface(struct bfd_session_params *bsp, const char *ifname)
{
	if ((ifname == NULL && bsp->args.ifnamelen == 0)
	    || (ifname && strcmp(bsp->args.ifname, ifname) == 0))
		return;

	/* If already installed, remove the old setting. */
	_bfd_sess_remove(bsp);

	if (ifname == NULL) {
		bsp->args.ifname[0] = 0;
		bsp->args.ifnamelen = 0;
		return;
	}

	if (strlcpy(bsp->args.ifname, ifname, sizeof(bsp->args.ifname))
	    > sizeof(bsp->args.ifname))
		zlog_warn("%s: interface name truncated: %s", __func__, ifname);

	bsp->args.ifnamelen = strlen(bsp->args.ifname);
}

void bfd_sess_set_profile(struct bfd_session_params *bsp, const char *profile)
{
	if (profile == NULL) {
		bsp->args.profile[0] = 0;
		bsp->args.profilelen = 0;
		return;
	}

	if (strlcpy(bsp->args.profile, profile, sizeof(bsp->args.profile))
	    > sizeof(bsp->args.profile))
		zlog_warn("%s: profile name truncated: %s", __func__, profile);

	bsp->args.profilelen = strlen(bsp->args.profile);
}

void bfd_sess_set_vrf(struct bfd_session_params *bsp, vrf_id_t vrf_id)
{
	if (bsp->args.vrf_id == vrf_id)
		return;

	/* If already installed, remove the old setting. */
	_bfd_sess_remove(bsp);
	/* Address changed so we must reapply auto source. */
	bfd_source_cache_put(bsp);

	bsp->args.vrf_id = vrf_id;

	if (bsp->auto_source)
		bfd_source_cache_get(bsp);
}

void bfd_sess_set_hop_count(struct bfd_session_params *bsp, uint8_t hops)
{
	if (bsp->args.hops == hops)
		return;

	/* If already installed, remove the old setting. */
	_bfd_sess_remove(bsp);

	bsp->args.hops = hops;
	bsp->args.mhop = (hops > 1);
}


void bfd_sess_set_cbit(struct bfd_session_params *bsp, bool enable)
{
	bsp->args.cbit = enable;
}

void bfd_sess_set_timers(struct bfd_session_params *bsp,
			 uint8_t detection_multiplier, uint32_t min_rx,
			 uint32_t min_tx)
{
	bsp->args.detection_multiplier = detection_multiplier;
	bsp->args.min_rx = min_rx;
	bsp->args.min_tx = min_tx;
}

void bfd_sess_set_auto_source(struct bfd_session_params *bsp, bool enable)
{
	if (bsp->auto_source == enable)
		return;

	bsp->auto_source = enable;
	if (enable)
		bfd_source_cache_get(bsp);
	else
		bfd_source_cache_put(bsp);
}

void bfd_sess_install(struct bfd_session_params *bsp)
{
	bsp->lastev = BSE_INSTALL;
	thread_add_event(bsglobal.tm, _bfd_sess_send, bsp, 0, &bsp->installev);
}

void bfd_sess_uninstall(struct bfd_session_params *bsp)
{
	bsp->lastev = BSE_UNINSTALL;
	thread_add_event(bsglobal.tm, _bfd_sess_send, bsp, 0, &bsp->installev);
}

enum bfd_session_state bfd_sess_status(const struct bfd_session_params *bsp)
{
	return bsp->bss.state;
}

uint8_t bfd_sess_hop_count(const struct bfd_session_params *bsp)
{
	return bsp->args.hops;
}

const char *bfd_sess_profile(const struct bfd_session_params *bsp)
{
	return bsp->args.profilelen ? bsp->args.profile : NULL;
}

void bfd_sess_addresses(const struct bfd_session_params *bsp, int *family,
			struct in6_addr *src, struct in6_addr *dst)
{
	*family = bsp->args.family;
	if (src)
		*src = bsp->args.src;
	if (dst)
		*dst = bsp->args.dst;
}

const char *bfd_sess_interface(const struct bfd_session_params *bsp)
{
	if (bsp->args.ifnamelen)
		return bsp->args.ifname;

	return NULL;
}

const char *bfd_sess_vrf(const struct bfd_session_params *bsp)
{
	return vrf_id_to_name(bsp->args.vrf_id);
}

vrf_id_t bfd_sess_vrf_id(const struct bfd_session_params *bsp)
{
	return bsp->args.vrf_id;
}

bool bfd_sess_cbit(const struct bfd_session_params *bsp)
{
	return bsp->args.cbit;
}

void bfd_sess_timers(const struct bfd_session_params *bsp,
		     uint8_t *detection_multiplier, uint32_t *min_rx,
		     uint32_t *min_tx)
{
	*detection_multiplier = bsp->args.detection_multiplier;
	*min_rx = bsp->args.min_rx;
	*min_tx = bsp->args.min_tx;
}

bool bfd_sess_auto_source(const struct bfd_session_params *bsp)
{
	return bsp->auto_source;
}

void bfd_sess_show(struct vty *vty, struct json_object *json,
		   struct bfd_session_params *bsp)
{
	json_object *json_bfd = NULL;
	char time_buf[64];

	if (!bsp)
		return;

	/* Show type. */
	if (json) {
		json_bfd = json_object_new_object();
		if (bsp->args.mhop)
			json_object_string_add(json_bfd, "type", "multi hop");
		else
			json_object_string_add(json_bfd, "type", "single hop");
	} else
		vty_out(vty, "  BFD: Type: %s\n",
			bsp->args.mhop ? "multi hop" : "single hop");

	/* Show configuration. */
	if (json) {
		json_object_int_add(json_bfd, "detectMultiplier",
				    bsp->args.detection_multiplier);
		json_object_int_add(json_bfd, "rxMinInterval",
				    bsp->args.min_rx);
		json_object_int_add(json_bfd, "txMinInterval",
				    bsp->args.min_tx);
	} else {
		vty_out(vty,
			"  Detect Multiplier: %d, Min Rx interval: %d, Min Tx interval: %d\n",
			bsp->args.detection_multiplier, bsp->args.min_rx,
			bsp->args.min_tx);
	}

	bfd_last_update(bsp->bss.last_event, time_buf, sizeof(time_buf));
	if (json) {
		json_object_string_add(json_bfd, "status",
				       bfd_get_status_str(bsp->bss.state));
		json_object_string_add(json_bfd, "lastUpdate", time_buf);
	} else
		vty_out(vty, "  Status: %s, Last update: %s\n",
			bfd_get_status_str(bsp->bss.state), time_buf);

	if (json)
		json_object_object_add(json, "peerBfdInfo", json_bfd);
	else
		vty_out(vty, "\n");
}

/*
 * Zebra communication related.
 */

/**
 * Callback for reinstallation of all registered BFD sessions.
 *
 * Use this as `zclient` `bfd_dest_replay` callback.
 */
int zclient_bfd_session_replay(ZAPI_CALLBACK_ARGS)
{
	struct bfd_session_params *bsp;

	if (!zclient->bfd_integration)
		return 0;

	/* Do nothing when shutting down. */
	if (bsglobal.shutting_down)
		return 0;

	if (bsglobal.debugging)
		zlog_debug("%s: sending all sessions registered", __func__);

	/* Send the client registration */
	bfd_client_sendmsg(zclient, ZEBRA_BFD_CLIENT_REGISTER, vrf_id);

	/* Replay all activated peers. */
	TAILQ_FOREACH (bsp, &bsglobal.bsplist, entry) {
		/* Skip not installed sessions. */
		if (!bsp->installed)
			continue;

		/* We are reconnecting, so we must send installation. */
		bsp->installed = false;

		/* Cancel any pending installation request. */
		THREAD_OFF(bsp->installev);

		/* Ask for installation. */
		bsp->lastev = BSE_INSTALL;
		thread_execute(bsglobal.tm, _bfd_sess_send, bsp, 0);
	}

	return 0;
}

int zclient_bfd_session_update(ZAPI_CALLBACK_ARGS)
{
	struct bfd_session_params *bsp, *bspn;
	size_t sessions_updated = 0;
	struct interface *ifp;
	int remote_cbit = false;
	int state = BFD_STATUS_UNKNOWN;
	time_t now;
	size_t addrlen;
	struct prefix dp;
	struct prefix sp;
	char ifstr[128], cbitstr[32];

	if (!zclient->bfd_integration)
		return 0;

	/* Do nothing when shutting down. */
	if (bsglobal.shutting_down)
		return 0;

	ifp = bfd_get_peer_info(zclient->ibuf, &dp, &sp, &state, &remote_cbit,
				vrf_id);
	/*
	 * When interface lookup fails or an invalid stream is read, we must
	 * not proceed otherwise it will trigger an assertion while checking
	 * family type below.
	 */
	if (dp.family == 0 || sp.family == 0)
		return 0;

	if (bsglobal.debugging) {
		ifstr[0] = 0;
		if (ifp)
			snprintf(ifstr, sizeof(ifstr), " (interface %s)",
				 ifp->name);

		snprintf(cbitstr, sizeof(cbitstr), " (CPI bit %s)",
			 remote_cbit ? "yes" : "no");

		zlog_debug("%s: %pFX -> %pFX%s VRF %s(%u)%s: %s", __func__, &sp,
			   &dp, ifstr, vrf_id_to_name(vrf_id), vrf_id, cbitstr,
			   bfd_get_status_str(state));
	}

	switch (dp.family) {
	case AF_INET:
		addrlen = sizeof(struct in_addr);
		break;
	case AF_INET6:
		addrlen = sizeof(struct in6_addr);
		break;

	default:
		/* Unexpected value. */
		assert(0);
		break;
	}

	/* Cache current time to avoid multiple monotime clock calls. */
	now = monotime(NULL);

	/* Notify all matching sessions about update. */
	TAILQ_FOREACH_SAFE (bsp, &bsglobal.bsplist, entry, bspn) {
		/* Skip not installed entries. */
		if (!bsp->installed)
			continue;
		/* Skip different VRFs. */
		if (bsp->args.vrf_id != vrf_id)
			continue;
		/* Skip different families. */
		if (bsp->args.family != dp.family)
			continue;
		/* Skip different interface. */
		if (bsp->args.ifnamelen && ifp
		    && strcmp(bsp->args.ifname, ifp->name) != 0)
			continue;
		/* Skip non matching destination addresses. */
		if (memcmp(&bsp->args.dst, &dp.u, addrlen) != 0)
			continue;
		/*
		 * Source comparison test:
		 * We will only compare source if BFD daemon provided the
		 * source address and the protocol set a source address in
		 * the configuration otherwise we'll just skip it.
		 */
		if (sp.family && memcmp(&bsp->args.src, &i6a_zero, addrlen) != 0
		    && memcmp(&sp.u, &i6a_zero, addrlen) != 0
		    && memcmp(&bsp->args.src, &sp.u, addrlen) != 0)
			continue;
		/* No session state change. */
		if ((int)bsp->bss.state == state)
			continue;

		bsp->bss.last_event = now;
		bsp->bss.previous_state = bsp->bss.state;
		bsp->bss.state = state;
		bsp->bss.remote_cbit = remote_cbit;
		bsp->updatecb(bsp, &bsp->bss, bsp->arg);
		sessions_updated++;
	}

	if (bsglobal.debugging)
		zlog_debug("%s:   sessions updated: %zu", __func__,
			   sessions_updated);

	return 0;
}

/**
 * Frees all allocated resources and stops any activity.
 *
 * Must be called after every BFD session has been successfully
 * unconfigured otherwise this function will `free()` any available
 * session causing existing pointers to dangle.
 *
 * This is just a comment, in practice it will be called by the FRR
 * library late finish hook. \see `bfd_protocol_integration_init`.
 */
static int bfd_protocol_integration_finish(void)
{
	if (bsglobal.zc == NULL)
		return 0;

	while (!TAILQ_EMPTY(&bsglobal.bsplist)) {
		struct bfd_session_params *session =
			TAILQ_FIRST(&bsglobal.bsplist);
		bfd_sess_free(&session);
	}

	/*
	 * BFD source cache is linked to sessions, if all sessions are gone
	 * then the source cache must be empty.
	 */
	if (!SLIST_EMPTY(&bsglobal.source_list))
		zlog_warn("BFD integration source cache not empty");

	return 0;
}

void bfd_protocol_integration_init(struct zclient *zc, struct thread_master *tm)
{
	/* Initialize data structure. */
	TAILQ_INIT(&bsglobal.bsplist);
	SLIST_INIT(&bsglobal.source_list);

	/* Copy pointers. */
	bsglobal.zc = zc;
	bsglobal.tm = tm;

	/* Enable BFD callbacks. */
	zc->bfd_integration = true;

	/* Send the client registration */
	bfd_client_sendmsg(zc, ZEBRA_BFD_CLIENT_REGISTER, VRF_DEFAULT);

	hook_register(frr_fini, bfd_protocol_integration_finish);
}

void bfd_protocol_integration_set_debug(bool enable)
{
	bsglobal.debugging = enable;
}

void bfd_protocol_integration_set_shutdown(bool enable)
{
	bsglobal.shutting_down = enable;
}

bool bfd_protocol_integration_debug(void)
{
	return bsglobal.debugging;
}

bool bfd_protocol_integration_shutting_down(void)
{
	return bsglobal.shutting_down;
}

/*
 * BFD automatic source selection
 *
 * This feature will use the next hop tracking (NHT) provided by zebra
 * to find out the source address by looking at the output interface.
 *
 * When the interface address / routing table change we'll be notified
 * and be able to update the source address accordingly.
 *
 *     <daemon>                 zebra
 *         |
 * +-----------------+
 * | BFD session set |
 * | to auto source  |
 * +-----------------+
 *         |
 *         \                 +-----------------+
 *          -------------->  | Resolves        |
 *                           | destination     |
 *                           | address         |
 *                           +-----------------+
 *                                |
 * +-----------------+            /
 * | Sets resolved   | <----------
 * | source address  |
 * +-----------------+
 */
static bool
bfd_source_cache_session_match(const struct bfd_source_cache *source,
			       const struct bfd_session_params *session)
{
	const struct in_addr *address;
	const struct in6_addr *address_v6;

	if (session->args.vrf_id != source->vrf_id)
		return false;
	if (session->args.family != source->address.family)
		return false;

	switch (session->args.family) {
	case AF_INET:
		address = (const struct in_addr *)&session->args.dst;
		if (address->s_addr != source->address.u.prefix4.s_addr)
			return false;
		break;
	case AF_INET6:
		address_v6 = &session->args.dst;
		if (memcmp(address_v6, &source->address.u.prefix6,
			   sizeof(struct in6_addr)))
			return false;
		break;
	default:
		return false;
	}

	return true;
}

static struct bfd_source_cache *
bfd_source_cache_find(vrf_id_t vrf_id, const struct prefix *prefix)
{
	struct bfd_source_cache *source;

	SLIST_FOREACH (source, &bsglobal.source_list, entry) {
		if (source->vrf_id != vrf_id)
			continue;
		if (!prefix_same(&source->address, prefix))
			continue;

		return source;
	}

	return NULL;
}

static void bfd_source_cache_get(struct bfd_session_params *session)
{
	struct bfd_source_cache *source;
	struct prefix target = {};

	switch (session->args.family) {
	case AF_INET:
		target.family = AF_INET;
		target.prefixlen = IPV4_MAX_BITLEN;
		memcpy(&target.u.prefix4, &session->args.dst,
		       sizeof(struct in_addr));
		break;
	case AF_INET6:
		target.family = AF_INET6;
		target.prefixlen = IPV6_MAX_BITLEN;
		memcpy(&target.u.prefix6, &session->args.dst,
		       sizeof(struct in6_addr));
		break;
	default:
		return;
	}

	source = bfd_source_cache_find(session->args.vrf_id, &target);
	if (source) {
		if (session->source_cache == source)
			return;

		bfd_source_cache_put(session);
		session->source_cache = source;
		source->refcount++;
		return;
	}

	source = XCALLOC(MTYPE_BFD_SOURCE, sizeof(*source));
	prefix_copy(&source->address, &target);
	source->vrf_id = session->args.vrf_id;
	SLIST_INSERT_HEAD(&bsglobal.source_list, source, entry);

	bfd_source_cache_put(session);
	session->source_cache = source;
	source->refcount = 1;

	bfd_source_cache_register(source);

	return;
}

static void bfd_source_cache_put(struct bfd_session_params *session)
{
	if (session->source_cache == NULL)
		return;

	session->source_cache->refcount--;
	if (session->source_cache->refcount > 0) {
		session->source_cache = NULL;
		return;
	}

	bfd_source_cache_unregister(session->source_cache);
	SLIST_REMOVE(&bsglobal.source_list, session->source_cache,
		     bfd_source_cache, entry);
	XFREE(MTYPE_BFD_SOURCE, session->source_cache);
}

/** Updates BFD running session if source address has changed. */
static void
bfd_source_cache_update_session(const struct bfd_source_cache *source,
				struct bfd_session_params *session)
{
	const struct in_addr *address;
	const struct in6_addr *address_v6;

	switch (session->args.family) {
	case AF_INET:
		address = (const struct in_addr *)&session->args.src;
		if (memcmp(address, &source->source.u.prefix4,
			   sizeof(struct in_addr)) == 0)
			return;

		_bfd_sess_remove(session);
		memcpy(&session->args.src, &source->source.u.prefix4,
		       sizeof(struct in_addr));
		break;
	case AF_INET6:
		address_v6 = &session->args.src;
		if (memcmp(address_v6, &source->source.u.prefix6,
			   sizeof(struct in6_addr)) == 0)
			return;

		_bfd_sess_remove(session);
		memcpy(&session->args.src, &source->source.u.prefix6,
		       sizeof(struct in6_addr));
		break;
	default:
		return;
	}

	bfd_sess_install(session);
}

static void
bfd_source_cache_update_sessions(const struct bfd_source_cache *source)
{
	struct bfd_session_params *session;

	if (!source->valid)
		return;

	TAILQ_FOREACH (session, &bsglobal.bsplist, entry) {
		if (!session->auto_source)
			continue;
		if (!bfd_source_cache_session_match(source, session))
			continue;

		bfd_source_cache_update_session(source, session);
	}
}

/**
 * Try to translate next hop information into source address.
 *
 * \returns `true` if source changed otherwise `false`.
 */
static bool bfd_source_cache_update(struct bfd_source_cache *source,
				    const struct zapi_route *route)
{
	size_t nh_index;

	for (nh_index = 0; nh_index < route->nexthop_num; nh_index++) {
		const struct zapi_nexthop *nh = &route->nexthops[nh_index];
		const struct interface *interface;
		const struct connected *connected;
		const struct listnode *node;

		interface = if_lookup_by_index(nh->ifindex, nh->vrf_id);
		if (interface == NULL) {
			zlog_err("next hop interface not found (index %d)",
				 nh->ifindex);
			continue;
		}

		for (ALL_LIST_ELEMENTS_RO(interface->connected, node,
					  connected)) {
			if (source->address.family !=
			    connected->address->family)
				continue;
			if (prefix_same(connected->address, &source->source))
				return false;
			/*
			 * Skip link-local as it is only useful for single hop
			 * and in that case no source is specified usually.
			 */
			if (source->address.family == AF_INET6 &&
			    IN6_IS_ADDR_LINKLOCAL(
				    &connected->address->u.prefix6))
				continue;

			prefix_copy(&source->source, connected->address);
			source->valid = true;
			return true;
		}
	}

	memset(&source->source, 0, sizeof(source->source));
	source->valid = false;
	return false;
}

void bfd_nht_zclient_connected(struct zclient *zclient)
{
	struct bfd_source_cache *source;

	if (bsglobal.debugging)
		zlog_debug("BFD NHT zclient connected");

	SLIST_FOREACH (source, &bsglobal.source_list, entry)
		bfd_source_cache_register(source);
}

int bfd_nht_update(const struct prefix *match, const struct zapi_route *route)
{
	struct bfd_source_cache *source;

	if (bsglobal.debugging)
		zlog_debug("BFD NHT update for %pFX", &route->prefix);

	SLIST_FOREACH (source, &bsglobal.source_list, entry) {
		if (source->vrf_id != route->vrf_id)
			continue;
		if (!prefix_same(match, &source->address))
			continue;
		if (bfd_source_cache_update(source, route))
			bfd_source_cache_update_sessions(source);
	}

	return 0;
}