xref: /freebsd/sys/netinet/ip_carp.c (revision 5ee92cbd82d0afb65bc5feabf29d8417307d38ad)

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2002 Michael Shalayeff.
 * Copyright (c) 2003 Ryan McBride.
 * Copyright (c) 2011 Gleb Smirnoff <glebius@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR OR HIS RELATIVES BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF MIND, USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#include "opt_bpf.h"
#include "opt_inet.h"
#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/devctl.h>
#include <sys/jail.h>
#include <sys/kassert.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/taskqueue.h>
#include <sys/counter.h>

#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/if_dl.h>
#include <net/if_llatbl.h>
#include <net/if_private.h>
#include <net/if_types.h>
#include <net/route.h>
#include <net/vnet.h>

#if defined(INET) || defined(INET6)
#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/ip_carp.h>
#include <netinet/ip_carp_nl.h>
#include <netinet/ip.h>
#include <machine/in_cksum.h>
#endif
#ifdef INET
#include <netinet/ip_var.h>
#include <netinet/if_ether.h>
#endif

#ifdef INET6
#include <netinet/icmp6.h>
#include <netinet/ip6.h>
#include <netinet6/in6_var.h>
#include <netinet6/ip6_var.h>
#include <netinet6/scope6_var.h>
#include <netinet6/nd6.h>
#endif

#include <netlink/netlink.h>
#include <netlink/netlink_ctl.h>
#include <netlink/netlink_generic.h>
#include <netlink/netlink_message_parser.h>

#include <crypto/sha1.h>

static MALLOC_DEFINE(M_CARP, "CARP", "CARP addresses");

struct carp_softc {
	struct ifnet		*sc_carpdev;	/* Pointer to parent ifnet. */
	struct ifaddr		**sc_ifas;	/* Our ifaddrs. */
	carp_version_t		sc_version;	/* carp or VRRPv3 */
	struct sockaddr_dl	sc_addr;	/* Our link level address. */
	struct callout		sc_ad_tmo;	/* Advertising timeout. */
#ifdef INET
	struct callout		sc_md_tmo;	/* Master down timeout. */
#endif
#ifdef INET6
	struct callout 		sc_md6_tmo;	/* XXX: Master down timeout. */
#endif
	struct mtx		sc_mtx;

	int			sc_vhid;
	struct { /* CARP specific context */
		int		sc_advskew;
		int		sc_advbase;
		struct in_addr	sc_carpaddr;
		struct in6_addr	sc_carpaddr6;
	};
	struct { /* VRRPv3 specific context */
		uint8_t		sc_vrrp_prio;
		uint16_t	sc_vrrp_adv_inter;
		uint16_t	sc_vrrp_master_inter;
	};

	int			sc_naddrs;
	int			sc_naddrs6;
	int			sc_ifasiz;
	enum { INIT = 0, BACKUP, MASTER }	sc_state;
	int			sc_suppress;
	int			sc_sendad_errors;
#define	CARP_SENDAD_MAX_ERRORS	3
	int			sc_sendad_success;
#define	CARP_SENDAD_MIN_SUCCESS 3

	int			sc_init_counter;
	uint64_t		sc_counter;

	/* authentication */
#define	CARP_HMAC_PAD	64
	unsigned char sc_key[CARP_KEY_LEN];
	unsigned char sc_pad[CARP_HMAC_PAD];
	SHA1_CTX sc_sha1;

	TAILQ_ENTRY(carp_softc)	sc_list;	/* On the carp_if list. */
	LIST_ENTRY(carp_softc)	sc_next;	/* On the global list. */
};

struct carp_if {
#ifdef INET
	int	cif_naddrs;
#endif
#ifdef INET6
	int	cif_naddrs6;
#endif
	TAILQ_HEAD(, carp_softc) cif_vrs;
#ifdef INET
	struct ip_moptions 	 cif_imo;
#endif
#ifdef INET6
	struct ip6_moptions 	 cif_im6o;
#endif
	struct ifnet	*cif_ifp;
	struct mtx	cif_mtx;
	uint32_t	cif_flags;
#define	CIF_PROMISC	0x00000001
};

/* Kernel equivalent of struct carpreq, but with more fields for new features.
 * */
struct carpkreq {
	int		carpr_count;
	int		carpr_vhid;
	int		carpr_state;
	int		carpr_advskew;
	int		carpr_advbase;
	unsigned char	carpr_key[CARP_KEY_LEN];
	/* Everything above this is identical to carpreq */
	struct in_addr	carpr_addr;
	struct in6_addr	carpr_addr6;
	carp_version_t	carpr_version;
	uint8_t		carpr_vrrp_priority;
	uint16_t	carpr_vrrp_adv_inter;
};

/*
 * Brief design of carp(4).
 *
 * Any carp-capable ifnet may have a list of carp softcs hanging off
 * its ifp->if_carp pointer. Each softc represents one unique virtual
 * host id, or vhid. The softc has a back pointer to the ifnet. All
 * softcs are joined in a global list, which has quite limited use.
 *
 * Any interface address that takes part in CARP negotiation has a
 * pointer to the softc of its vhid, ifa->ifa_carp. That could be either
 * AF_INET or AF_INET6 address.
 *
 * Although, one can get the softc's backpointer to ifnet and traverse
 * through its ifp->if_addrhead queue to find all interface addresses
 * involved in CARP, we keep a growable array of ifaddr pointers. This
 * allows us to avoid grabbing the IF_ADDR_LOCK() in many traversals that
 * do calls into the network stack, thus avoiding LORs.
 *
 * Locking:
 *
 * Each softc has a lock sc_mtx. It is used to synchronise carp_input_c(),
 * callout-driven events and ioctl()s.
 *
 * To traverse the list of softcs on an ifnet we use CIF_LOCK() or carp_sx.
 * To traverse the global list we use the mutex carp_mtx.
 *
 * Known issues with locking:
 *
 * - Sending ad, we put the pointer to the softc in an mtag, and no reference
 *   counting is done on the softc.
 * - On module unload we may race (?) with packet processing thread
 *   dereferencing our function pointers.
 */

/* Accept incoming CARP packets. */
VNET_DEFINE_STATIC(int, carp_allow) = 1;
#define	V_carp_allow	VNET(carp_allow)

/* Set DSCP in outgoing CARP packets. */
VNET_DEFINE_STATIC(int, carp_dscp) = 56;
#define	V_carp_dscp	VNET(carp_dscp)

/* Preempt slower nodes. */
VNET_DEFINE_STATIC(int, carp_preempt) = 0;
#define	V_carp_preempt	VNET(carp_preempt)

/* Log level. */
VNET_DEFINE_STATIC(int, carp_log) = 1;
#define	V_carp_log	VNET(carp_log)

/* Global advskew demotion. */
VNET_DEFINE_STATIC(int, carp_demotion) = 0;
#define	V_carp_demotion	VNET(carp_demotion)

/* Send error demotion factor. */
VNET_DEFINE_STATIC(int, carp_senderr_adj) = CARP_MAXSKEW;
#define	V_carp_senderr_adj	VNET(carp_senderr_adj)

/* Iface down demotion factor. */
VNET_DEFINE_STATIC(int, carp_ifdown_adj) = CARP_MAXSKEW;
#define	V_carp_ifdown_adj	VNET(carp_ifdown_adj)

static int carp_allow_sysctl(SYSCTL_HANDLER_ARGS);
static int carp_dscp_sysctl(SYSCTL_HANDLER_ARGS);
static int carp_demote_adj_sysctl(SYSCTL_HANDLER_ARGS);

SYSCTL_NODE(_net_inet, IPPROTO_CARP, carp, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "CARP");
SYSCTL_PROC(_net_inet_carp, OID_AUTO, allow,
    CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE,
    &VNET_NAME(carp_allow), 0, carp_allow_sysctl, "I",
    "Accept incoming CARP packets");
SYSCTL_PROC(_net_inet_carp, OID_AUTO, dscp,
    CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
    0, 0, carp_dscp_sysctl, "I",
    "DSCP value for carp packets");
SYSCTL_INT(_net_inet_carp, OID_AUTO, preempt, CTLFLAG_VNET | CTLFLAG_RW,
    &VNET_NAME(carp_preempt), 0, "High-priority backup preemption mode");
SYSCTL_INT(_net_inet_carp, OID_AUTO, log, CTLFLAG_VNET | CTLFLAG_RW,
    &VNET_NAME(carp_log), 0, "CARP log level");
SYSCTL_PROC(_net_inet_carp, OID_AUTO, demotion,
    CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
    0, 0, carp_demote_adj_sysctl, "I",
    "Adjust demotion factor (skew of advskew)");
SYSCTL_INT(_net_inet_carp, OID_AUTO, senderr_demotion_factor,
    CTLFLAG_VNET | CTLFLAG_RW,
    &VNET_NAME(carp_senderr_adj), 0, "Send error demotion factor adjustment");
SYSCTL_INT(_net_inet_carp, OID_AUTO, ifdown_demotion_factor,
    CTLFLAG_VNET | CTLFLAG_RW,
    &VNET_NAME(carp_ifdown_adj), 0,
    "Interface down demotion factor adjustment");

VNET_PCPUSTAT_DEFINE(struct carpstats, carpstats);
VNET_PCPUSTAT_SYSINIT(carpstats);
VNET_PCPUSTAT_SYSUNINIT(carpstats);

#define	CARPSTATS_ADD(name, val)	\
    counter_u64_add(VNET(carpstats)[offsetof(struct carpstats, name) / \
	sizeof(uint64_t)], (val))
#define	CARPSTATS_INC(name)		CARPSTATS_ADD(name, 1)

SYSCTL_VNET_PCPUSTAT(_net_inet_carp, OID_AUTO, stats, struct carpstats,
    carpstats, "CARP statistics (struct carpstats, netinet/ip_carp.h)");

#define	CARP_LOCK_INIT(sc)	mtx_init(&(sc)->sc_mtx, "carp_softc",   \
	NULL, MTX_DEF)
#define	CARP_LOCK_DESTROY(sc)	mtx_destroy(&(sc)->sc_mtx)
#define	CARP_LOCK_ASSERT(sc)	mtx_assert(&(sc)->sc_mtx, MA_OWNED)
#define	CARP_LOCK(sc)		mtx_lock(&(sc)->sc_mtx)
#define	CARP_UNLOCK(sc)		mtx_unlock(&(sc)->sc_mtx)
#define	CIF_LOCK_INIT(cif)	mtx_init(&(cif)->cif_mtx, "carp_if",   \
	NULL, MTX_DEF)
#define	CIF_LOCK_DESTROY(cif)	mtx_destroy(&(cif)->cif_mtx)
#define	CIF_LOCK_ASSERT(cif)	mtx_assert(&(cif)->cif_mtx, MA_OWNED)
#define	CIF_LOCK(cif)		mtx_lock(&(cif)->cif_mtx)
#define	CIF_UNLOCK(cif)		mtx_unlock(&(cif)->cif_mtx)
#define	CIF_FREE(cif)	do {				\
		CIF_LOCK(cif);				\
		if (TAILQ_EMPTY(&(cif)->cif_vrs))	\
			carp_free_if(cif);		\
		else					\
			CIF_UNLOCK(cif);		\
} while (0)

#define	CARP_LOG(...)	do {				\
	if (V_carp_log > 0)				\
		log(LOG_INFO, "carp: " __VA_ARGS__);	\
} while (0)

#define	CARP_DEBUG(...)	do {				\
	if (V_carp_log > 1)				\
		log(LOG_DEBUG, __VA_ARGS__);		\
} while (0)

#define	IFNET_FOREACH_IFA(ifp, ifa)					\
	CK_STAILQ_FOREACH((ifa), &(ifp)->if_addrhead, ifa_link)	\
		if ((ifa)->ifa_carp != NULL)

#define	CARP_FOREACH_IFA(sc, ifa)					\
	CARP_LOCK_ASSERT(sc);						\
	for (int _i = 0;						\
		_i < (sc)->sc_naddrs + (sc)->sc_naddrs6 &&		\
		((ifa) = sc->sc_ifas[_i]) != NULL;			\
		++_i)

#define	IFNET_FOREACH_CARP(ifp, sc)					\
	KASSERT(mtx_owned(&ifp->if_carp->cif_mtx) ||			\
	    sx_xlocked(&carp_sx), ("cif_vrs not locked"));		\
	TAILQ_FOREACH((sc), &(ifp)->if_carp->cif_vrs, sc_list)

#define	DEMOTE_ADVSKEW(sc)					\
    (((sc)->sc_advskew + V_carp_demotion > CARP_MAXSKEW) ?	\
    CARP_MAXSKEW :						\
        (((sc)->sc_advskew + V_carp_demotion < 0) ?		\
        0 : ((sc)->sc_advskew + V_carp_demotion)))

static void	carp_input_c(struct mbuf *, struct carp_header *, sa_family_t, int);
static void	vrrp_input_c(struct mbuf *, int, sa_family_t, int, int, uint16_t);
static struct carp_softc
		*carp_alloc(struct ifnet *);
static void	carp_destroy(struct carp_softc *);
static struct carp_if
		*carp_alloc_if(struct ifnet *);
static void	carp_free_if(struct carp_if *);
static void	carp_set_state(struct carp_softc *, int, const char* reason);
static void	carp_sc_state(struct carp_softc *);
static void	carp_setrun(struct carp_softc *, sa_family_t);
static void	carp_master_down(void *);
static void	carp_master_down_locked(struct carp_softc *,
    		    const char* reason);
static void	carp_send_ad_locked(struct carp_softc *);
static void	vrrp_send_ad_locked(struct carp_softc *);
static void	carp_addroute(struct carp_softc *);
static void	carp_ifa_addroute(struct ifaddr *);
static void	carp_delroute(struct carp_softc *);
static void	carp_ifa_delroute(struct ifaddr *);
static void	carp_send_ad_all(void *, int);
static void	carp_demote_adj(int, char *);

static LIST_HEAD(, carp_softc) carp_list;
static struct mtx carp_mtx;
static struct sx carp_sx;
static struct task carp_sendall_task =
    TASK_INITIALIZER(0, carp_send_ad_all, NULL);

static int
carp_is_supported_if(if_t ifp)
{
	if (ifp == NULL)
		return (ENXIO);

	switch (ifp->if_type) {
	case IFT_ETHER:
	case IFT_L2VLAN:
	case IFT_BRIDGE:
		break;
	default:
		return (EOPNOTSUPP);
	}

	return (0);
}

static void
carp_hmac_prepare(struct carp_softc *sc)
{
	uint8_t version = CARP_VERSION_CARP, type = CARP_ADVERTISEMENT;
	uint8_t vhid = sc->sc_vhid & 0xff;
	struct ifaddr *ifa;
	int i, found;
#ifdef INET
	struct in_addr last, cur, in;
#endif
#ifdef INET6
	struct in6_addr last6, cur6, in6;
#endif

	CARP_LOCK_ASSERT(sc);

	/* Compute ipad from key. */
	bzero(sc->sc_pad, sizeof(sc->sc_pad));
	bcopy(sc->sc_key, sc->sc_pad, sizeof(sc->sc_key));
	for (i = 0; i < sizeof(sc->sc_pad); i++)
		sc->sc_pad[i] ^= 0x36;

	/* Precompute first part of inner hash. */
	SHA1Init(&sc->sc_sha1);
	SHA1Update(&sc->sc_sha1, sc->sc_pad, sizeof(sc->sc_pad));
	SHA1Update(&sc->sc_sha1, (void *)&version, sizeof(version));
	SHA1Update(&sc->sc_sha1, (void *)&type, sizeof(type));
	SHA1Update(&sc->sc_sha1, (void *)&vhid, sizeof(vhid));
#ifdef INET
	cur.s_addr = 0;
	do {
		found = 0;
		last = cur;
		cur.s_addr = 0xffffffff;
		CARP_FOREACH_IFA(sc, ifa) {
			in.s_addr = ifatoia(ifa)->ia_addr.sin_addr.s_addr;
			if (ifa->ifa_addr->sa_family == AF_INET &&
			    ntohl(in.s_addr) > ntohl(last.s_addr) &&
			    ntohl(in.s_addr) < ntohl(cur.s_addr)) {
				cur.s_addr = in.s_addr;
				found++;
			}
		}
		if (found)
			SHA1Update(&sc->sc_sha1, (void *)&cur, sizeof(cur));
	} while (found);
#endif /* INET */
#ifdef INET6
	memset(&cur6, 0, sizeof(cur6));
	do {
		found = 0;
		last6 = cur6;
		memset(&cur6, 0xff, sizeof(cur6));
		CARP_FOREACH_IFA(sc, ifa) {
			in6 = ifatoia6(ifa)->ia_addr.sin6_addr;
			if (IN6_IS_SCOPE_EMBED(&in6))
				in6.s6_addr16[1] = 0;
			if (ifa->ifa_addr->sa_family == AF_INET6 &&
			    memcmp(&in6, &last6, sizeof(in6)) > 0 &&
			    memcmp(&in6, &cur6, sizeof(in6)) < 0) {
				cur6 = in6;
				found++;
			}
		}
		if (found)
			SHA1Update(&sc->sc_sha1, (void *)&cur6, sizeof(cur6));
	} while (found);
#endif /* INET6 */

	/* convert ipad to opad */
	for (i = 0; i < sizeof(sc->sc_pad); i++)
		sc->sc_pad[i] ^= 0x36 ^ 0x5c;
}

static void
carp_hmac_generate(struct carp_softc *sc, uint32_t counter[2],
    unsigned char md[20])
{
	SHA1_CTX sha1ctx;

	CARP_LOCK_ASSERT(sc);

	/* fetch first half of inner hash */
	bcopy(&sc->sc_sha1, &sha1ctx, sizeof(sha1ctx));

	SHA1Update(&sha1ctx, (void *)counter, sizeof(sc->sc_counter));
	SHA1Final(md, &sha1ctx);

	/* outer hash */
	SHA1Init(&sha1ctx);
	SHA1Update(&sha1ctx, sc->sc_pad, sizeof(sc->sc_pad));
	SHA1Update(&sha1ctx, md, 20);
	SHA1Final(md, &sha1ctx);
}

static int
carp_hmac_verify(struct carp_softc *sc, uint32_t counter[2],
    unsigned char md[20])
{
	unsigned char md2[20];

	CARP_LOCK_ASSERT(sc);

	carp_hmac_generate(sc, counter, md2);

	return (bcmp(md, md2, sizeof(md2)));
}

static int
vrrp_checksum_verify(struct mbuf *m, int off, int len, uint16_t phdrcksum)
{
	uint16_t cksum;

	/*
	 * Note that VRRPv3 checksums are different from CARP checksums.
	 * Carp just calculates the checksum over the packet.
	 * VRRPv3 includes the pseudo-header checksum as well.
	 */
	cksum = in_cksum_skip(m, off + len, off);
	cksum -= phdrcksum;

	return (cksum);
}

/*
 * process input packet.
 * we have rearranged checks order compared to the rfc,
 * but it seems more efficient this way or not possible otherwise.
 */
#ifdef INET
static int
carp_input(struct mbuf **mp, int *offp, int proto)
{
	struct mbuf *m = *mp;
	struct ip *ip = mtod(m, struct ip *);
	struct vrrpv3_header *vh;
	int iplen;
	int minlen;
	int totlen;
	uint16_t phdrcksum = 0;

	iplen = *offp;
	*mp = NULL;

	CARPSTATS_INC(carps_ipackets);

	if (!V_carp_allow) {
		m_freem(m);
		return (IPPROTO_DONE);
	}

	iplen = ip->ip_hl << 2;
	totlen = ntohs(ip->ip_len);

	/* Ensure we have enough header to figure out the version. */
	if (m->m_pkthdr.len < iplen + sizeof(*vh)) {
		CARPSTATS_INC(carps_badlen);
		CARP_DEBUG("%s: received len %zd < sizeof(struct vrrpv3_header) "
		    "on %s\n", __func__, m->m_len - sizeof(struct ip),
		    if_name(m->m_pkthdr.rcvif));
		m_freem(m);
		return (IPPROTO_DONE);
	}

	if (iplen + sizeof(*vh) < m->m_len) {
		if ((m = m_pullup(m, iplen + sizeof(*vh))) == NULL) {
			CARPSTATS_INC(carps_hdrops);
			CARP_DEBUG("%s():%d: pullup failed\n", __func__, __LINE__);
			return (IPPROTO_DONE);
		}
		ip = mtod(m, struct ip *);
	}
	vh = (struct vrrpv3_header *)((char *)ip + iplen);

	switch (vh->vrrp_version) {
	case CARP_VERSION_CARP:
		minlen = sizeof(struct carp_header);
		break;
	case CARP_VERSION_VRRPv3:
		minlen = sizeof(struct vrrpv3_header);
		break;
	default:
		CARPSTATS_INC(carps_badver);
		CARP_DEBUG("%s: unsupported version %d on %s\n", __func__,
		    vh->vrrp_version, if_name(m->m_pkthdr.rcvif));
		m_freem(m);
		return (IPPROTO_DONE);
	}

	/* And now check the length again but with the real minimal length. */
	if (m->m_pkthdr.len < iplen + minlen) {
		CARPSTATS_INC(carps_badlen);
		CARP_DEBUG("%s: received len %zd < %d "
		    "on %s\n", __func__, m->m_len - sizeof(struct ip),
		    iplen + minlen,
		    if_name(m->m_pkthdr.rcvif));
		m_freem(m);
		return (IPPROTO_DONE);
	}

	if (iplen + minlen < m->m_len) {
		if ((m = m_pullup(m, iplen + minlen)) == NULL) {
			CARPSTATS_INC(carps_hdrops);
			CARP_DEBUG("%s():%d: pullup failed\n", __func__, __LINE__);
			return (IPPROTO_DONE);
		}
		ip = mtod(m, struct ip *);
		vh = (struct vrrpv3_header *)((char *)ip + iplen);
	}

	phdrcksum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
	    htonl((u_short)(totlen - iplen) + ip->ip_p));

	if (vh->vrrp_version == CARP_VERSION_CARP) {
		/* verify the CARP checksum */
		m->m_data += iplen;
		if (in_cksum(m, totlen - iplen)) {
			CARPSTATS_INC(carps_badsum);
			CARP_DEBUG("%s: checksum failed on %s\n", __func__,
			    if_name(m->m_pkthdr.rcvif));
			m_freem(m);
			return (IPPROTO_DONE);
		}
		m->m_data -= iplen;
	}

	switch (vh->vrrp_version) {
	case CARP_VERSION_CARP: {
		struct carp_header *ch = (struct carp_header *)((char *)ip + iplen);
		carp_input_c(m, ch, AF_INET, ip->ip_ttl);
		break;
	}
	case CARP_VERSION_VRRPv3:
		vrrp_input_c(m, iplen, AF_INET, ip->ip_ttl, totlen - iplen, phdrcksum);
		break;
	default:
		KASSERT(false, ("Unsupported version %d", vh->vrrp_version));
	}

	return (IPPROTO_DONE);
}
#endif

#ifdef INET6
static int
carp6_input(struct mbuf **mp, int *offp, int proto)
{
	struct mbuf *m = *mp;
	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
	struct vrrpv3_header *vh;
	u_int len, minlen;
	uint16_t phdrcksum = 0;

	CARPSTATS_INC(carps_ipackets6);

	if (!V_carp_allow) {
		m_freem(m);
		return (IPPROTO_DONE);
	}

	/* check if received on a valid carp interface */
	if (m->m_pkthdr.rcvif->if_carp == NULL) {
		CARPSTATS_INC(carps_badif);
		CARP_DEBUG("%s: packet received on non-carp interface: %s\n",
		    __func__, if_name(m->m_pkthdr.rcvif));
		m_freem(m);
		return (IPPROTO_DONE);
	}

	if (m->m_len < *offp + sizeof(*vh)) {
		len = m->m_len;
		m = m_pullup(m, *offp + sizeof(*vh));
		if (m == NULL) {
			CARPSTATS_INC(carps_badlen);
			CARP_DEBUG("%s: packet size %u too small\n", __func__, len);
			return (IPPROTO_DONE);
		}
		ip6 = mtod(m, struct ip6_hdr *);
	}
	vh = (struct vrrpv3_header *)(mtod(m, char *) + *offp);

	switch (vh->vrrp_version) {
	case CARP_VERSION_CARP:
		minlen = sizeof(struct carp_header);
		break;
	case CARP_VERSION_VRRPv3:
		minlen = sizeof(struct vrrpv3_header);
		break;
	default:
		CARPSTATS_INC(carps_badver);
		CARP_DEBUG("%s: unsupported version %d on %s\n", __func__,
		    vh->vrrp_version, if_name(m->m_pkthdr.rcvif));
		m_freem(m);
		return (IPPROTO_DONE);
	}

	/* And now check the length again but with the real minimal length. */
	if (m->m_pkthdr.len < sizeof(*ip6) + minlen) {
		CARPSTATS_INC(carps_badlen);
		CARP_DEBUG("%s: received len %zd < %zd "
		    "on %s\n", __func__, m->m_len - sizeof(struct ip),
		    sizeof(*ip6) + minlen,
		    if_name(m->m_pkthdr.rcvif));
		m_freem(m);
		return (IPPROTO_DONE);
	}

	if (sizeof (*ip6) + minlen < m->m_len) {
		if ((m = m_pullup(m, sizeof(*ip6) + minlen)) == NULL) {
			CARPSTATS_INC(carps_hdrops);
			CARP_DEBUG("%s():%d: pullup failed\n", __func__, __LINE__);
			return (IPPROTO_DONE);
		}
		ip6 = mtod(m, struct ip6_hdr *);
		vh = (struct vrrpv3_header *)mtodo(m, sizeof(*ip6));
	}

	phdrcksum = in6_cksum_pseudo(ip6, ntohs(ip6->ip6_plen), ip6->ip6_nxt, 0);

	/* verify the CARP checksum */
	if (vh->vrrp_version == CARP_VERSION_CARP) {
		m->m_data += *offp;
		if (in_cksum(m, sizeof(struct carp_header))) {
			CARPSTATS_INC(carps_badsum);
			CARP_DEBUG("%s: checksum failed, on %s\n", __func__,
			    if_name(m->m_pkthdr.rcvif));
			m_freem(m);
			return (IPPROTO_DONE);
		}
		m->m_data -= *offp;
	}

	switch (vh->vrrp_version) {
	case CARP_VERSION_CARP: {
		struct carp_header *ch = (struct carp_header *)((char *)ip6 + sizeof(*ip6));
		carp_input_c(m, ch, AF_INET6, ip6->ip6_hlim);
		break;
	}
	case CARP_VERSION_VRRPv3:
		vrrp_input_c(m, sizeof(*ip6), AF_INET6, ip6->ip6_hlim, ntohs(ip6->ip6_plen),
		    phdrcksum);
		break;
	default:
		KASSERT(false, ("Unsupported version %d", vh->vrrp_version));
	}
	return (IPPROTO_DONE);
}
#endif /* INET6 */

/*
 * This routine should not be necessary at all, but some switches
 * (VMWare ESX vswitches) can echo our own packets back at us,
 * and we must ignore them or they will cause us to drop out of
 * MASTER mode.
 *
 * We cannot catch all cases of network loops.  Instead, what we
 * do here is catch any packet that arrives with a carp header
 * with a VHID of 0, that comes from an address that is our own.
 * These packets are by definition "from us" (even if they are from
 * a misconfigured host that is pretending to be us).
 *
 * The VHID test is outside this mini-function.
 */
static int
carp_source_is_self(const struct mbuf *m, struct ifaddr *ifa, sa_family_t af)
{
#ifdef INET
	struct ip *ip4;
	struct in_addr in4;
#endif
#ifdef INET6
	struct ip6_hdr *ip6;
	struct in6_addr in6;
#endif

	switch (af) {
#ifdef INET
	case AF_INET:
		ip4 = mtod(m, struct ip *);
		in4 = ifatoia(ifa)->ia_addr.sin_addr;
		return (in4.s_addr == ip4->ip_src.s_addr);
#endif
#ifdef INET6
	case AF_INET6:
		ip6 = mtod(m, struct ip6_hdr *);
		in6 = ifatoia6(ifa)->ia_addr.sin6_addr;
		return (memcmp(&in6, &ip6->ip6_src, sizeof(in6)) == 0);
#endif
	default:
		break;
	}
	return (0);
}

static struct ifaddr *
carp_find_ifa(const struct mbuf *m, sa_family_t af, uint8_t vhid)
{
	struct ifnet *ifp = m->m_pkthdr.rcvif;
	struct ifaddr *ifa, *match;
	int error;

	NET_EPOCH_ASSERT();

	/*
	 * Verify that the VHID is valid on the receiving interface.
	 *
	 * There should be just one match.  If there are none
	 * the VHID is not valid and we drop the packet.  If
	 * there are multiple VHID matches, take just the first
	 * one, for compatibility with previous code.  While we're
	 * scanning, check for obvious loops in the network topology
	 * (these should never happen, and as noted above, we may
	 * miss real loops; this is just a double-check).
	 */
	error = 0;
	match = NULL;
	IFNET_FOREACH_IFA(ifp, ifa) {
		if (match == NULL && ifa->ifa_carp != NULL &&
		    ifa->ifa_addr->sa_family == af &&
		    ifa->ifa_carp->sc_vhid == vhid)
			match = ifa;
		if (vhid == 0 && carp_source_is_self(m, ifa, af))
			error = ELOOP;
	}
	ifa = error ? NULL : match;
	if (ifa != NULL)
		ifa_ref(ifa);

	if (ifa == NULL) {
		if (error == ELOOP) {
			CARP_DEBUG("dropping looped packet on interface %s\n",
			    if_name(ifp));
			CARPSTATS_INC(carps_badif);	/* ??? */
		} else {
			CARPSTATS_INC(carps_badvhid);
		}
	}

	return (ifa);
}

static void
carp_input_c(struct mbuf *m, struct carp_header *ch, sa_family_t af, int ttl)
{
	struct ifnet *ifp = m->m_pkthdr.rcvif;
	struct ifaddr *ifa;
	struct carp_softc *sc;
	uint64_t tmp_counter;
	struct timeval sc_tv, ch_tv;
	bool multicast = false;

	NET_EPOCH_ASSERT();

	ifa = carp_find_ifa(m, af, ch->carp_vhid);
	if (ifa == NULL) {
		m_freem(m);
		return;
	}

	sc = ifa->ifa_carp;
	CARP_LOCK(sc);

	/* verify the CARP version. */
	if (ch->carp_version != CARP_VERSION_CARP ||
	    sc->sc_version != CARP_VERSION_CARP) {
		CARP_UNLOCK(sc);

		CARPSTATS_INC(carps_badver);
		CARP_DEBUG("%s: invalid version %d\n", if_name(ifp),
		    ch->carp_version);
		ifa_free(ifa);
		m_freem(m);
		return;
	}

	if (ifa->ifa_addr->sa_family == AF_INET) {
		multicast = IN_MULTICAST(sc->sc_carpaddr.s_addr);
	} else {
		multicast = IN6_IS_ADDR_MULTICAST(&sc->sc_carpaddr6);
	}
	ifa_free(ifa);

	/* verify that the IP TTL is 255, but only if we're not in unicast mode. */
	if (multicast && ttl != CARP_DFLTTL) {
		CARPSTATS_INC(carps_badttl);
		CARP_DEBUG("%s: received ttl %d != 255 on %s\n", __func__,
		    ttl, if_name(m->m_pkthdr.rcvif));
		goto out;
	}

	if (carp_hmac_verify(sc, ch->carp_counter, ch->carp_md)) {
		CARPSTATS_INC(carps_badauth);
		CARP_DEBUG("%s: incorrect hash for VHID %u@%s\n", __func__,
		    sc->sc_vhid, if_name(ifp));
		goto out;
	}

	tmp_counter = ntohl(ch->carp_counter[0]);
	tmp_counter = tmp_counter<<32;
	tmp_counter += ntohl(ch->carp_counter[1]);

	/* XXX Replay protection goes here */

	sc->sc_init_counter = 0;
	sc->sc_counter = tmp_counter;

	sc_tv.tv_sec = sc->sc_advbase;
	sc_tv.tv_usec = DEMOTE_ADVSKEW(sc) * 1000000 / 256;
	ch_tv.tv_sec = ch->carp_advbase;
	ch_tv.tv_usec = ch->carp_advskew * 1000000 / 256;

	switch (sc->sc_state) {
	case INIT:
		break;
	case MASTER:
		/*
		 * If we receive an advertisement from a master who's going to
		 * be more frequent than us, go into BACKUP state.
		 */
		if (timevalcmp(&sc_tv, &ch_tv, >) ||
		    timevalcmp(&sc_tv, &ch_tv, ==)) {
			callout_stop(&sc->sc_ad_tmo);
			carp_set_state(sc, BACKUP,
			    "more frequent advertisement received");
			carp_setrun(sc, 0);
			carp_delroute(sc);
		}
		break;
	case BACKUP:
		/*
		 * If we're pre-empting masters who advertise slower than us,
		 * and this one claims to be slower, treat him as down.
		 */
		if (V_carp_preempt && timevalcmp(&sc_tv, &ch_tv, <)) {
			carp_master_down_locked(sc,
			    "preempting a slower master");
			break;
		}

		/*
		 *  If the master is going to advertise at such a low frequency
		 *  that he's guaranteed to time out, we'd might as well just
		 *  treat him as timed out now.
		 */
		sc_tv.tv_sec = sc->sc_advbase * 3;
		if (timevalcmp(&sc_tv, &ch_tv, <)) {
			carp_master_down_locked(sc, "master will time out");
			break;
		}

		/*
		 * Otherwise, we reset the counter and wait for the next
		 * advertisement.
		 */
		carp_setrun(sc, af);
		break;
	}

out:
	CARP_UNLOCK(sc);
	m_freem(m);
}

static void
vrrp_input_c(struct mbuf *m, int off, sa_family_t af, int ttl,
    int len, uint16_t phdrcksum)
{
	struct vrrpv3_header *vh = mtodo(m, off);
	struct ifnet *ifp = m->m_pkthdr.rcvif;
	struct ifaddr *ifa;
	struct carp_softc *sc;

	NET_EPOCH_ASSERT();

	ifa = carp_find_ifa(m, af, vh->vrrp_vrtid);
	if (ifa == NULL) {
		m_freem(m);
		return;
	}

	sc = ifa->ifa_carp;
	CARP_LOCK(sc);

	ifa_free(ifa);

	/* verify the CARP version. */
	if (vh->vrrp_version != CARP_VERSION_VRRPv3 || sc->sc_version != CARP_VERSION_VRRPv3) {
		CARP_UNLOCK(sc);

		CARPSTATS_INC(carps_badver);
		CARP_DEBUG("%s: invalid version %d\n", if_name(ifp),
		    vh->vrrp_version);
		m_freem(m);
		return;
	}

	/* verify that the IP TTL is 255. */
	if (ttl != CARP_DFLTTL) {
		CARPSTATS_INC(carps_badttl);
		CARP_DEBUG("%s: received ttl %d != 255 on %s\n", __func__,
		    ttl, if_name(m->m_pkthdr.rcvif));
		goto out;
	}

	if (vrrp_checksum_verify(m, off, len, phdrcksum)) {
		CARPSTATS_INC(carps_badsum);
		CARP_DEBUG("%s: incorrect checksum for VRID %u@%s\n", __func__,
		    sc->sc_vhid, if_name(ifp));
		goto out;
	}

	/* RFC9568, 7.1 Receiving VRRP packets. */
	if (sc->sc_vrrp_prio == 255) {
		CARP_DEBUG("%s: our priority is 255. Ignore peer announcement.\n",
		    __func__);
		goto out;
	}

	/* XXX TODO Check IP address payload. */

	sc->sc_vrrp_master_inter = ntohs(vh->vrrp_max_adver_int);

	switch (sc->sc_state) {
	case INIT:
		break;
	case MASTER:
		/*
		 * If we receive an advertisement from a master who's going to
		 * be more frequent than us, go into BACKUP state.
		 * Same if the peer has a higher priority than us.
		 */
		if (ntohs(vh->vrrp_max_adver_int) < sc->sc_vrrp_adv_inter ||
		    vh->vrrp_priority > sc->sc_vrrp_prio) {
			callout_stop(&sc->sc_ad_tmo);
			carp_set_state(sc, BACKUP,
			    "more frequent advertisement received");
			carp_setrun(sc, 0);
			carp_delroute(sc);
		}
		break;
	case BACKUP:
		/*
		 * If we're pre-empting masters who advertise slower than us,
		 * and this one claims to be slower, treat him as down.
		 */
		if (V_carp_preempt && (ntohs(vh->vrrp_max_adver_int) > sc->sc_vrrp_adv_inter
		    || vh->vrrp_priority < sc->sc_vrrp_prio)) {
			carp_master_down_locked(sc,
			    "preempting a slower master");
			break;
		}

		/*
		 * Otherwise, we reset the counter and wait for the next
		 * advertisement.
		 */
		carp_setrun(sc, af);
		break;
	}

out:
	CARP_UNLOCK(sc);
	m_freem(m);
}

static int
carp_tag(struct carp_softc *sc, struct mbuf *m)
{
	struct m_tag *mtag;

	/* Tag packet for carp_output */
	if ((mtag = m_tag_get(PACKET_TAG_CARP, sizeof(struct carp_softc *),
	    M_NOWAIT)) == NULL) {
		m_freem(m);
		CARPSTATS_INC(carps_onomem);
		return (ENOMEM);
	}
	bcopy(&sc, mtag + 1, sizeof(sc));
	m_tag_prepend(m, mtag);

	return (0);
}

static int
carp_prepare_ad(struct mbuf *m, struct carp_softc *sc, struct carp_header *ch)
{

	if (sc->sc_init_counter) {
		/* this could also be seconds since unix epoch */
		sc->sc_counter = arc4random();
		sc->sc_counter = sc->sc_counter << 32;
		sc->sc_counter += arc4random();
	} else
		sc->sc_counter++;

	ch->carp_counter[0] = htonl((sc->sc_counter>>32)&0xffffffff);
	ch->carp_counter[1] = htonl(sc->sc_counter&0xffffffff);

	carp_hmac_generate(sc, ch->carp_counter, ch->carp_md);

	return (carp_tag(sc, m));
}

static inline void
send_ad_locked(struct carp_softc *sc)
{
	switch (sc->sc_version) {
	case CARP_VERSION_CARP:
		carp_send_ad_locked(sc);
		break;
	case CARP_VERSION_VRRPv3:
		vrrp_send_ad_locked(sc);
		break;
	}
}

/*
 * To avoid LORs and possible recursions this function shouldn't
 * be called directly, but scheduled via taskqueue.
 */
static void
carp_send_ad_all(void *ctx __unused, int pending __unused)
{
	struct carp_softc *sc;
	struct epoch_tracker et;

	NET_EPOCH_ENTER(et);
	mtx_lock(&carp_mtx);
	LIST_FOREACH(sc, &carp_list, sc_next)
		if (sc->sc_state == MASTER) {
			CARP_LOCK(sc);
			CURVNET_SET(sc->sc_carpdev->if_vnet);
			send_ad_locked(sc);
			CURVNET_RESTORE();
			CARP_UNLOCK(sc);
		}
	mtx_unlock(&carp_mtx);
	NET_EPOCH_EXIT(et);
}

/* Send a periodic advertisement, executed in callout context. */
static void
carp_callout(void *v)
{
	struct carp_softc *sc = v;
	struct epoch_tracker et;

	NET_EPOCH_ENTER(et);
	CARP_LOCK_ASSERT(sc);
	CURVNET_SET(sc->sc_carpdev->if_vnet);
	send_ad_locked(sc);
	CURVNET_RESTORE();
	CARP_UNLOCK(sc);
	NET_EPOCH_EXIT(et);
}

static void
carp_send_ad_error(struct carp_softc *sc, int error)
{

	/*
	 * We track errors and successful sends with this logic:
	 * - Any error resets success counter to 0.
	 * - MAX_ERRORS triggers demotion.
	 * - MIN_SUCCESS successes resets error counter to 0.
	 * - MIN_SUCCESS reverts demotion, if it was triggered before.
	 */
	if (error) {
		if (sc->sc_sendad_errors < INT_MAX)
			sc->sc_sendad_errors++;
		if (sc->sc_sendad_errors == CARP_SENDAD_MAX_ERRORS) {
			static const char fmt[] = "send error %d on %s";
			char msg[sizeof(fmt) + IFNAMSIZ];

			sprintf(msg, fmt, error, if_name(sc->sc_carpdev));
			carp_demote_adj(V_carp_senderr_adj, msg);
		}
		sc->sc_sendad_success = 0;
	} else if (sc->sc_sendad_errors > 0) {
		if (++sc->sc_sendad_success >= CARP_SENDAD_MIN_SUCCESS) {
			if (sc->sc_sendad_errors >= CARP_SENDAD_MAX_ERRORS) {
				static const char fmt[] = "send ok on %s";
				char msg[sizeof(fmt) + IFNAMSIZ];

				sprintf(msg, fmt, if_name(sc->sc_carpdev));
				carp_demote_adj(-V_carp_senderr_adj, msg);
			}
			sc->sc_sendad_errors = 0;
		}
	}
}

/*
 * Pick the best ifaddr on the given ifp for sending CARP
 * advertisements.
 *
 * "Best" here is defined by ifa_preferred().  This function is much
 * much like ifaof_ifpforaddr() except that we just use ifa_preferred().
 *
 * (This could be simplified to return the actual address, except that
 * it has a different format in AF_INET and AF_INET6.)
 */
static struct ifaddr *
carp_best_ifa(int af, struct ifnet *ifp)
{
	struct ifaddr *ifa, *best;

	NET_EPOCH_ASSERT();

	if (af >= AF_MAX)
		return (NULL);
	best = NULL;
	CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
		if (ifa->ifa_addr->sa_family == af &&
		    (best == NULL || ifa_preferred(best, ifa)))
			best = ifa;
	}
	if (best != NULL)
		ifa_ref(best);
	return (best);
}

static void
carp_send_ad_locked(struct carp_softc *sc)
{
	struct carp_header ch;
	struct timeval tv;
	struct ifaddr *ifa;
	struct carp_header *ch_ptr;
	struct mbuf *m;
	int len, advskew;

	NET_EPOCH_ASSERT();
	CARP_LOCK_ASSERT(sc);
	MPASS(sc->sc_version == CARP_VERSION_CARP);

	advskew = DEMOTE_ADVSKEW(sc);
	tv.tv_sec = sc->sc_advbase;
	tv.tv_usec = advskew * 1000000 / 256;

	ch.carp_version = CARP_VERSION_CARP;
	ch.carp_type = CARP_ADVERTISEMENT;
	ch.carp_vhid = sc->sc_vhid;
	ch.carp_advbase = sc->sc_advbase;
	ch.carp_advskew = advskew;
	ch.carp_authlen = 7;	/* XXX DEFINE */
	ch.carp_pad1 = 0;	/* must be zero */
	ch.carp_cksum = 0;

	/* XXXGL: OpenBSD picks first ifaddr with needed family. */

#ifdef INET
	if (sc->sc_naddrs) {
		struct ip *ip;

		m = m_gethdr(M_NOWAIT, MT_DATA);
		if (m == NULL) {
			CARPSTATS_INC(carps_onomem);
			goto resched;
		}
		len = sizeof(*ip) + sizeof(ch);
		m->m_pkthdr.len = len;
		m->m_pkthdr.rcvif = NULL;
		m->m_len = len;
		M_ALIGN(m, m->m_len);
		if (IN_MULTICAST(sc->sc_carpaddr.s_addr))
			m->m_flags |= M_MCAST;
		ip = mtod(m, struct ip *);
		ip->ip_v = IPVERSION;
		ip->ip_hl = sizeof(*ip) >> 2;
		ip->ip_tos = V_carp_dscp << IPTOS_DSCP_OFFSET;
		ip->ip_len = htons(len);
		ip->ip_off = htons(IP_DF);
		ip->ip_ttl = CARP_DFLTTL;
		ip->ip_p = IPPROTO_CARP;
		ip->ip_sum = 0;
		ip_fillid(ip);

		ifa = carp_best_ifa(AF_INET, sc->sc_carpdev);
		if (ifa != NULL) {
			ip->ip_src.s_addr =
			    ifatoia(ifa)->ia_addr.sin_addr.s_addr;
			ifa_free(ifa);
		} else
			ip->ip_src.s_addr = 0;
		ip->ip_dst = sc->sc_carpaddr;

		ch_ptr = (struct carp_header *)(&ip[1]);
		bcopy(&ch, ch_ptr, sizeof(ch));
		if (carp_prepare_ad(m, sc, ch_ptr))
			goto resched;

		m->m_data += sizeof(*ip);
		ch_ptr->carp_cksum = in_cksum(m, len - sizeof(*ip));
		m->m_data -= sizeof(*ip);

		CARPSTATS_INC(carps_opackets);

		carp_send_ad_error(sc, ip_output(m, NULL, NULL, IP_RAWOUTPUT,
		    &sc->sc_carpdev->if_carp->cif_imo, NULL));
	}
#endif /* INET */
#ifdef INET6
	if (sc->sc_naddrs6) {
		struct ip6_hdr *ip6;

		m = m_gethdr(M_NOWAIT, MT_DATA);
		if (m == NULL) {
			CARPSTATS_INC(carps_onomem);
			goto resched;
		}
		len = sizeof(*ip6) + sizeof(ch);
		m->m_pkthdr.len = len;
		m->m_pkthdr.rcvif = NULL;
		m->m_len = len;
		M_ALIGN(m, m->m_len);
		ip6 = mtod(m, struct ip6_hdr *);
		bzero(ip6, sizeof(*ip6));
		ip6->ip6_vfc |= IPV6_VERSION;
		/* Traffic class isn't defined in ip6 struct instead
		 * it gets offset into flowid field */
		ip6->ip6_flow |= htonl(V_carp_dscp << (IPV6_FLOWLABEL_LEN +
		    IPTOS_DSCP_OFFSET));
		ip6->ip6_hlim = CARP_DFLTTL;
		ip6->ip6_nxt = IPPROTO_CARP;

		/* set the source address */
		ifa = carp_best_ifa(AF_INET6, sc->sc_carpdev);
		if (ifa != NULL) {
			bcopy(IFA_IN6(ifa), &ip6->ip6_src,
			    sizeof(struct in6_addr));
			ifa_free(ifa);
		} else
			/* This should never happen with IPv6. */
			bzero(&ip6->ip6_src, sizeof(struct in6_addr));

		/* Set the multicast destination. */
		memcpy(&ip6->ip6_dst, &sc->sc_carpaddr6, sizeof(ip6->ip6_dst));
		if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
		    IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_dst)) {
			if (in6_setscope(&ip6->ip6_dst, sc->sc_carpdev, NULL) != 0) {
				m_freem(m);
				CARP_DEBUG("%s: in6_setscope failed\n", __func__);
				goto resched;
			}
		}

		ch_ptr = (struct carp_header *)(&ip6[1]);
		bcopy(&ch, ch_ptr, sizeof(ch));
		if (carp_prepare_ad(m, sc, ch_ptr))
			goto resched;

		m->m_data += sizeof(*ip6);
		ch_ptr->carp_cksum = in_cksum(m, len - sizeof(*ip6));
		m->m_data -= sizeof(*ip6);

		CARPSTATS_INC(carps_opackets6);

		carp_send_ad_error(sc, ip6_output(m, NULL, NULL, 0,
		    &sc->sc_carpdev->if_carp->cif_im6o, NULL, NULL));
	}
#endif /* INET6 */

resched:
	callout_reset(&sc->sc_ad_tmo, tvtohz(&tv), carp_callout, sc);
}

static void
vrrp_send_ad_locked(struct carp_softc *sc)
{
	struct vrrpv3_header *vh_ptr;
	struct ifaddr *ifa;
	struct mbuf *m;
	int len;
	struct vrrpv3_header vh = {
	    .vrrp_version = CARP_VERSION_VRRPv3,
	    .vrrp_type = VRRP_TYPE_ADVERTISEMENT,
	    .vrrp_vrtid = sc->sc_vhid,
	    .vrrp_priority = sc->sc_vrrp_prio,
	    .vrrp_count_addr = 0,
	    .vrrp_max_adver_int = htons(sc->sc_vrrp_adv_inter),
	    .vrrp_checksum = 0,
	};

	NET_EPOCH_ASSERT();
	CARP_LOCK_ASSERT(sc);
	MPASS(sc->sc_version == CARP_VERSION_VRRPv3);

#ifdef INET
	if (sc->sc_naddrs) {
		struct ip *ip;

		m = m_gethdr(M_NOWAIT, MT_DATA);
		if (m == NULL) {
			CARPSTATS_INC(carps_onomem);
			goto resched;
		}
		len = sizeof(*ip) + sizeof(vh);
		m->m_pkthdr.len = len;
		m->m_pkthdr.rcvif = NULL;
		m->m_len = len;
		M_ALIGN(m, m->m_len);
		m->m_flags |= M_MCAST;
		ip = mtod(m, struct ip *);
		ip->ip_v = IPVERSION;
		ip->ip_hl = sizeof(*ip) >> 2;
		ip->ip_tos = V_carp_dscp << IPTOS_DSCP_OFFSET;
		ip->ip_off = htons(IP_DF);
		ip->ip_ttl = CARP_DFLTTL;
		ip->ip_p = IPPROTO_CARP;
		ip->ip_sum = 0;
		ip_fillid(ip);

		ifa = carp_best_ifa(AF_INET, sc->sc_carpdev);
		if (ifa != NULL) {
			ip->ip_src.s_addr =
			    ifatoia(ifa)->ia_addr.sin_addr.s_addr;
			ifa_free(ifa);
		} else
			ip->ip_src.s_addr = 0;
		ip->ip_dst.s_addr = htonl(INADDR_CARP_GROUP);

		/* Include the IP addresses in the announcement. */
		for (int i = 0; i < (sc->sc_naddrs + sc->sc_naddrs6); i++) {
			struct sockaddr_in *in;

			MPASS(sc->sc_ifas[i] != NULL);
			if (sc->sc_ifas[i]->ifa_addr->sa_family != AF_INET)
				continue;

			in = (struct sockaddr_in *)sc->sc_ifas[i]->ifa_addr;

			if (m_append(m, sizeof(in->sin_addr),
			    (caddr_t)&in->sin_addr) != 1) {
				m_freem(m);
				goto resched;
			}

			vh.vrrp_count_addr++;
			len += sizeof(in->sin_addr);
		}
		ip->ip_len = htons(len);

		vh_ptr = (struct vrrpv3_header *)mtodo(m, sizeof(*ip));
		bcopy(&vh, vh_ptr, sizeof(vh));

		vh_ptr->vrrp_checksum = in_pseudo(ip->ip_src.s_addr,
		    ip->ip_dst.s_addr,
		    htonl((uint16_t)(len - sizeof(*ip)) + ip->ip_p));
		vh_ptr->vrrp_checksum = in_cksum_skip(m, len, sizeof(*ip));

		if (carp_tag(sc, m))
			goto resched;

		CARPSTATS_INC(carps_opackets);

		carp_send_ad_error(sc, ip_output(m, NULL, NULL, IP_RAWOUTPUT,
		    &sc->sc_carpdev->if_carp->cif_imo, NULL));
	}
#endif
#ifdef INET6
	if (sc->sc_naddrs6) {
		struct ip6_hdr *ip6;

		m = m_gethdr(M_NOWAIT, MT_DATA);
		if (m == NULL) {
			CARPSTATS_INC(carps_onomem);
			goto resched;
		}
		len = sizeof(*ip6) + sizeof(vh);
		m->m_pkthdr.len = len;
		m->m_pkthdr.rcvif = NULL;
		m->m_len = len;
		M_ALIGN(m, m->m_len);
		m->m_flags |= M_MCAST;
		ip6 = mtod(m, struct ip6_hdr *);
		bzero(ip6, sizeof(*ip6));
		ip6->ip6_vfc |= IPV6_VERSION;
		/* Traffic class isn't defined in ip6 struct instead
		 * it gets offset into flowid field */
		ip6->ip6_flow |= htonl(V_carp_dscp << (IPV6_FLOWLABEL_LEN +
		    IPTOS_DSCP_OFFSET));
		ip6->ip6_hlim = CARP_DFLTTL;
		ip6->ip6_nxt = IPPROTO_CARP;

		/* set the source address */
		ifa = carp_best_ifa(AF_INET6, sc->sc_carpdev);
		if (ifa != NULL) {
			bcopy(IFA_IN6(ifa), &ip6->ip6_src,
			    sizeof(struct in6_addr));
			ifa_free(ifa);
		} else
			/* This should never happen with IPv6. */
			bzero(&ip6->ip6_src, sizeof(struct in6_addr));

		/* Set the multicast destination. */
		bzero(&ip6->ip6_dst, sizeof(ip6->ip6_dst));
		ip6->ip6_dst.s6_addr16[0] = IPV6_ADDR_INT16_MLL;
		ip6->ip6_dst.s6_addr8[15] = 0x12;

		/* Include the IP addresses in the announcement. */
		len = sizeof(vh);
		for (int i = 0; i < (sc->sc_naddrs + sc->sc_naddrs6); i++) {
			struct sockaddr_in6 *in6;

			MPASS(sc->sc_ifas[i] != NULL);
			if (sc->sc_ifas[i]->ifa_addr->sa_family != AF_INET6)
				continue;

			in6 = (struct sockaddr_in6 *)sc->sc_ifas[i]->ifa_addr;

			if (m_append(m, sizeof(in6->sin6_addr),
			    (char *)&in6->sin6_addr) != 1) {
				m_freem(m);
				goto resched;
			}

			vh.vrrp_count_addr++;
			len += sizeof(in6->sin6_addr);
		}
		ip6->ip6_plen = htonl(len);

		vh_ptr = (struct vrrpv3_header *)mtodo(m, sizeof(*ip6));
		bcopy(&vh, vh_ptr, sizeof(vh));

		vh_ptr->vrrp_checksum = in6_cksum_pseudo(ip6, len, ip6->ip6_nxt, 0);
		vh_ptr->vrrp_checksum = in_cksum_skip(m, len + sizeof(*ip6), sizeof(*ip6));

		if (in6_setscope(&ip6->ip6_dst, sc->sc_carpdev, NULL) != 0) {
			m_freem(m);
			CARP_DEBUG("%s: in6_setscope failed\n", __func__);
			goto resched;
		}

		if (carp_tag(sc, m))
			goto resched;
		CARPSTATS_INC(carps_opackets6);

		carp_send_ad_error(sc, ip6_output(m, NULL, NULL, 0,
		    &sc->sc_carpdev->if_carp->cif_im6o, NULL, NULL));
	}
#endif

resched:
	callout_reset(&sc->sc_ad_tmo, sc->sc_vrrp_adv_inter * hz / 100,
	    carp_callout, sc);
}

static void
carp_addroute(struct carp_softc *sc)
{
	struct ifaddr *ifa;

	CARP_FOREACH_IFA(sc, ifa)
		carp_ifa_addroute(ifa);
}

static void
carp_ifa_addroute(struct ifaddr *ifa)
{

	switch (ifa->ifa_addr->sa_family) {
#ifdef INET
	case AF_INET:
		in_addprefix(ifatoia(ifa));
		ifa_add_loopback_route(ifa,
		    (struct sockaddr *)&ifatoia(ifa)->ia_addr);
		break;
#endif
#ifdef INET6
	case AF_INET6:
		ifa_add_loopback_route(ifa,
		    (struct sockaddr *)&ifatoia6(ifa)->ia_addr);
		nd6_add_ifa_lle(ifatoia6(ifa));
		break;
#endif
	}
}

static void
carp_delroute(struct carp_softc *sc)
{
	struct ifaddr *ifa;

	CARP_FOREACH_IFA(sc, ifa)
		carp_ifa_delroute(ifa);
}

static void
carp_ifa_delroute(struct ifaddr *ifa)
{

	switch (ifa->ifa_addr->sa_family) {
#ifdef INET
	case AF_INET:
		ifa_del_loopback_route(ifa,
		    (struct sockaddr *)&ifatoia(ifa)->ia_addr);
		in_scrubprefix(ifatoia(ifa), LLE_STATIC);
		break;
#endif
#ifdef INET6
	case AF_INET6:
		ifa_del_loopback_route(ifa,
		    (struct sockaddr *)&ifatoia6(ifa)->ia_addr);
		nd6_rem_ifa_lle(ifatoia6(ifa), 1);
		break;
#endif
	}
}

int
carp_master(struct ifaddr *ifa)
{
	struct carp_softc *sc = ifa->ifa_carp;

	return (sc->sc_state == MASTER);
}

#ifdef INET
/*
 * Broadcast a gratuitous ARP request containing
 * the virtual router MAC address for each IP address
 * associated with the virtual router.
 */
static void
carp_send_arp(struct carp_softc *sc)
{
	struct ifaddr *ifa;
	struct in_addr addr;

	NET_EPOCH_ASSERT();

	CARP_FOREACH_IFA(sc, ifa) {
		if (ifa->ifa_addr->sa_family != AF_INET)
			continue;
		addr = ((struct sockaddr_in *)ifa->ifa_addr)->sin_addr;
		arp_announce_ifaddr(sc->sc_carpdev, addr, LLADDR(&sc->sc_addr));
	}
}

int
carp_iamatch(struct ifaddr *ifa, uint8_t **enaddr)
{
	struct carp_softc *sc = ifa->ifa_carp;

	if (sc->sc_state == MASTER) {
		*enaddr = LLADDR(&sc->sc_addr);
		return (1);
	}

	return (0);
}
#endif

#ifdef INET6
static void
carp_send_na(struct carp_softc *sc)
{
	static struct in6_addr mcast = IN6ADDR_LINKLOCAL_ALLNODES_INIT;
	struct ifaddr *ifa;
	struct in6_addr *in6;

	CARP_FOREACH_IFA(sc, ifa) {
		if (ifa->ifa_addr->sa_family != AF_INET6)
			continue;

		in6 = IFA_IN6(ifa);
		nd6_na_output(sc->sc_carpdev, &mcast, in6,
		    ND_NA_FLAG_OVERRIDE, 1, NULL);
		DELAY(1000);	/* XXX */
	}
}

/*
 * Returns ifa in case it's a carp address and it is MASTER, or if the address
 * matches and is not a carp address.  Returns NULL otherwise.
 */
struct ifaddr *
carp_iamatch6(struct ifnet *ifp, struct in6_addr *taddr)
{
	struct ifaddr *ifa;

	NET_EPOCH_ASSERT();

	ifa = NULL;
	CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
		if (ifa->ifa_addr->sa_family != AF_INET6)
			continue;
		if (!IN6_ARE_ADDR_EQUAL(taddr, IFA_IN6(ifa)))
			continue;
		if (ifa->ifa_carp && ifa->ifa_carp->sc_state != MASTER)
			ifa = NULL;
		else
			ifa_ref(ifa);
		break;
	}

	return (ifa);
}

char *
carp_macmatch6(struct ifnet *ifp, struct mbuf *m, const struct in6_addr *taddr)
{
	struct ifaddr *ifa;

	NET_EPOCH_ASSERT();

	IFNET_FOREACH_IFA(ifp, ifa)
		if (ifa->ifa_addr->sa_family == AF_INET6 &&
		    IN6_ARE_ADDR_EQUAL(taddr, IFA_IN6(ifa))) {
			struct carp_softc *sc = ifa->ifa_carp;
			struct m_tag *mtag;

			mtag = m_tag_get(PACKET_TAG_CARP,
			    sizeof(struct carp_softc *), M_NOWAIT);
			if (mtag == NULL)
				/* Better a bit than nothing. */
				return (LLADDR(&sc->sc_addr));

			bcopy(&sc, mtag + 1, sizeof(sc));
			m_tag_prepend(m, mtag);

			return (LLADDR(&sc->sc_addr));
		}

	return (NULL);
}
#endif /* INET6 */

int
carp_forus(struct ifnet *ifp, u_char *dhost)
{
	struct carp_softc *sc;
	uint8_t *ena = dhost;

	if (ena[0] || ena[1] || ena[2] != 0x5e || ena[3] || ena[4] != 1)
		return (0);

	CIF_LOCK(ifp->if_carp);
	IFNET_FOREACH_CARP(ifp, sc) {
		/*
		 * CARP_LOCK() is not here, since would protect nothing, but
		 * cause deadlock with if_bridge, calling this under its lock.
		 */
		if (sc->sc_state == MASTER && !bcmp(dhost, LLADDR(&sc->sc_addr),
		    ETHER_ADDR_LEN)) {
			CIF_UNLOCK(ifp->if_carp);
			return (1);
		}
	}
	CIF_UNLOCK(ifp->if_carp);

	return (0);
}

/* Master down timeout event, executed in callout context. */
static void
carp_master_down(void *v)
{
	struct carp_softc *sc = v;
	struct epoch_tracker et;

	NET_EPOCH_ENTER(et);
	CARP_LOCK_ASSERT(sc);

	CURVNET_SET(sc->sc_carpdev->if_vnet);
	if (sc->sc_state == BACKUP) {
		carp_master_down_locked(sc, "master timed out");
	}
	CURVNET_RESTORE();

	CARP_UNLOCK(sc);
	NET_EPOCH_EXIT(et);
}

static void
carp_master_down_locked(struct carp_softc *sc, const char *reason)
{

	NET_EPOCH_ASSERT();
	CARP_LOCK_ASSERT(sc);

	switch (sc->sc_state) {
	case BACKUP:
		carp_set_state(sc, MASTER, reason);
		send_ad_locked(sc);
#ifdef INET
		carp_send_arp(sc);
#endif
#ifdef INET6
		carp_send_na(sc);
#endif
		carp_setrun(sc, 0);
		carp_addroute(sc);
		break;
	case INIT:
	case MASTER:
#ifdef INVARIANTS
		panic("carp: VHID %u@%s: master_down event in %s state\n",
		    sc->sc_vhid,
		    if_name(sc->sc_carpdev),
		    sc->sc_state ? "MASTER" : "INIT");
#endif
		break;
	}
}

/*
 * When in backup state, af indicates whether to reset the master down timer
 * for v4 or v6. If it's set to zero, reset the ones which are already pending.
 */
static void
carp_setrun(struct carp_softc *sc, sa_family_t af)
{
	struct timeval tv;
	int timeout;

	CARP_LOCK_ASSERT(sc);

	if ((sc->sc_carpdev->if_flags & IFF_UP) == 0 ||
	    sc->sc_carpdev->if_link_state != LINK_STATE_UP ||
	    (sc->sc_naddrs == 0 && sc->sc_naddrs6 == 0) ||
	    !V_carp_allow)
		return;

	switch (sc->sc_state) {
	case INIT:
		carp_set_state(sc, BACKUP, "initialization complete");
		carp_setrun(sc, 0);
		break;
	case BACKUP:
		callout_stop(&sc->sc_ad_tmo);

		if (sc->sc_version == CARP_VERSION_CARP) {
			tv.tv_sec = 3 * sc->sc_advbase;
			tv.tv_usec = sc->sc_advskew * 1000000 / 256;
			timeout = tvtohz(&tv);
		} else {
			/* skew time */
			timeout = (256 - sc->sc_vrrp_prio) * sc->sc_vrrp_master_inter / 256;
			timeout += (3 * sc->sc_vrrp_master_inter);
			timeout *= hz;
			timeout /= 100; /* master interval is in centiseconds. */
		}

		switch (af) {
#ifdef INET
		case AF_INET:
			callout_reset(&sc->sc_md_tmo, timeout,
			    carp_master_down, sc);
			break;
#endif
#ifdef INET6
		case AF_INET6:
			callout_reset(&sc->sc_md6_tmo, timeout,
			    carp_master_down, sc);
			break;
#endif
		default:
#ifdef INET
			if (sc->sc_naddrs)
				callout_reset(&sc->sc_md_tmo, timeout,
				    carp_master_down, sc);
#endif
#ifdef INET6
			if (sc->sc_naddrs6)
				callout_reset(&sc->sc_md6_tmo, timeout,
				    carp_master_down, sc);
#endif
			break;
		}
		break;
	case MASTER:
		if (sc->sc_version == CARP_VERSION_CARP) {
			tv.tv_sec = sc->sc_advbase;
			tv.tv_usec = sc->sc_advskew * 1000000 / 256;
			callout_reset(&sc->sc_ad_tmo, tvtohz(&tv),
			    carp_callout, sc);
		} else {
			callout_reset(&sc->sc_ad_tmo,
			    sc->sc_vrrp_adv_inter * hz / 100,
			    carp_callout, sc);
		}
		break;
	}
}

/*
 * Setup multicast structures.
 */
static int
carp_multicast_setup(struct carp_if *cif, sa_family_t sa)
{
	struct ifnet *ifp = cif->cif_ifp;
	int error = 0;

	switch (sa) {
#ifdef INET
	case AF_INET:
	    {
		struct ip_moptions *imo = &cif->cif_imo;
		struct in_mfilter *imf;
		struct in_addr addr;

		if (ip_mfilter_first(&imo->imo_head) != NULL)
			return (0);

		imf = ip_mfilter_alloc(M_WAITOK, 0, 0);
		ip_mfilter_init(&imo->imo_head);
		imo->imo_multicast_vif = -1;

		addr.s_addr = htonl(INADDR_CARP_GROUP);
		if ((error = in_joingroup(ifp, &addr, NULL,
		    &imf->imf_inm)) != 0) {
			ip_mfilter_free(imf);
			break;
		}

		ip_mfilter_insert(&imo->imo_head, imf);
		imo->imo_multicast_ifp = ifp;
		imo->imo_multicast_ttl = CARP_DFLTTL;
		imo->imo_multicast_loop = 0;
		break;
	   }
#endif
#ifdef INET6
	case AF_INET6:
	    {
		struct ip6_moptions *im6o = &cif->cif_im6o;
		struct in6_mfilter *im6f[2];
		struct in6_addr in6;

		if (ip6_mfilter_first(&im6o->im6o_head))
			return (0);

		im6f[0] = ip6_mfilter_alloc(M_WAITOK, 0, 0);
		im6f[1] = ip6_mfilter_alloc(M_WAITOK, 0, 0);

		ip6_mfilter_init(&im6o->im6o_head);
		im6o->im6o_multicast_hlim = CARP_DFLTTL;
		im6o->im6o_multicast_ifp = ifp;

		/* Join IPv6 CARP multicast group. */
		bzero(&in6, sizeof(in6));
		in6.s6_addr16[0] = htons(0xff02);
		in6.s6_addr8[15] = 0x12;
		if ((error = in6_setscope(&in6, ifp, NULL)) != 0) {
			ip6_mfilter_free(im6f[0]);
			ip6_mfilter_free(im6f[1]);
			break;
		}
		if ((error = in6_joingroup(ifp, &in6, NULL, &im6f[0]->im6f_in6m, 0)) != 0) {
			ip6_mfilter_free(im6f[0]);
			ip6_mfilter_free(im6f[1]);
			break;
		}

		/* Join solicited multicast address. */
		bzero(&in6, sizeof(in6));
		in6.s6_addr16[0] = htons(0xff02);
		in6.s6_addr32[1] = 0;
		in6.s6_addr32[2] = htonl(1);
		in6.s6_addr32[3] = 0;
		in6.s6_addr8[12] = 0xff;

		if ((error = in6_setscope(&in6, ifp, NULL)) != 0) {
			ip6_mfilter_free(im6f[0]);
			ip6_mfilter_free(im6f[1]);
			break;
		}

		if ((error = in6_joingroup(ifp, &in6, NULL, &im6f[1]->im6f_in6m, 0)) != 0) {
			in6_leavegroup(im6f[0]->im6f_in6m, NULL);
			ip6_mfilter_free(im6f[0]);
			ip6_mfilter_free(im6f[1]);
			break;
		}
		ip6_mfilter_insert(&im6o->im6o_head, im6f[0]);
		ip6_mfilter_insert(&im6o->im6o_head, im6f[1]);
		break;
	    }
#endif
	}

	return (error);
}

/*
 * Free multicast structures.
 */
static void
carp_multicast_cleanup(struct carp_if *cif, sa_family_t sa)
{
#ifdef INET
	struct ip_moptions *imo = &cif->cif_imo;
	struct in_mfilter *imf;
#endif
#ifdef INET6
	struct ip6_moptions *im6o = &cif->cif_im6o;
	struct in6_mfilter *im6f;
#endif
	sx_assert(&carp_sx, SA_XLOCKED);

	switch (sa) {
#ifdef INET
	case AF_INET:
		if (cif->cif_naddrs != 0)
			break;

		while ((imf = ip_mfilter_first(&imo->imo_head)) != NULL) {
			ip_mfilter_remove(&imo->imo_head, imf);
			in_leavegroup(imf->imf_inm, NULL);
			ip_mfilter_free(imf);
		}
		break;
#endif
#ifdef INET6
	case AF_INET6:
		if (cif->cif_naddrs6 != 0)
			break;

		while ((im6f = ip6_mfilter_first(&im6o->im6o_head)) != NULL) {
			ip6_mfilter_remove(&im6o->im6o_head, im6f);
			in6_leavegroup(im6f->im6f_in6m, NULL);
			ip6_mfilter_free(im6f);
		}
		break;
#endif
	}
}

int
carp_output(struct ifnet *ifp, struct mbuf *m, const struct sockaddr *sa)
{
	struct m_tag *mtag;
	struct carp_softc *sc;

	if (!sa)
		return (0);

	switch (sa->sa_family) {
#ifdef INET
	case AF_INET:
		break;
#endif
#ifdef INET6
	case AF_INET6:
		break;
#endif
	default:
		return (0);
	}

	mtag = m_tag_find(m, PACKET_TAG_CARP, NULL);
	if (mtag == NULL)
		return (0);

	bcopy(mtag + 1, &sc, sizeof(sc));

	switch (sa->sa_family) {
	case AF_INET:
		if (! IN_MULTICAST(ntohl(sc->sc_carpaddr.s_addr)))
			return (0);
		break;
	case AF_INET6:
		if (! IN6_IS_ADDR_MULTICAST(&sc->sc_carpaddr6))
			return (0);
		break;
	default:
		panic("Unknown af");
	}

	/* Set the source MAC address to the Virtual Router MAC Address. */
	switch (ifp->if_type) {
	case IFT_ETHER:
	case IFT_BRIDGE:
	case IFT_L2VLAN: {
			struct ether_header *eh;

			eh = mtod(m, struct ether_header *);
			eh->ether_shost[0] = 0;
			eh->ether_shost[1] = 0;
			eh->ether_shost[2] = 0x5e;
			eh->ether_shost[3] = 0;
			eh->ether_shost[4] = 1;
			eh->ether_shost[5] = sc->sc_vhid;
		}
		break;
	default:
		printf("%s: carp is not supported for the %d interface type\n",
		    if_name(ifp), ifp->if_type);
		return (EOPNOTSUPP);
	}

	return (0);
}

static struct carp_softc*
carp_alloc(struct ifnet *ifp)
{
	struct carp_softc *sc;
	struct carp_if *cif;

	sx_assert(&carp_sx, SA_XLOCKED);

	if ((cif = ifp->if_carp) == NULL)
		cif = carp_alloc_if(ifp);

	sc = malloc(sizeof(*sc), M_CARP, M_WAITOK|M_ZERO);

	sc->sc_version = CARP_VERSION_CARP;
	sc->sc_advbase = CARP_DFLTINTV;
	sc->sc_vhid = -1;	/* required setting */
	sc->sc_init_counter = 1;
	sc->sc_state = INIT;

	sc->sc_ifasiz = sizeof(struct ifaddr *);
	sc->sc_ifas = malloc(sc->sc_ifasiz, M_CARP, M_WAITOK|M_ZERO);
	sc->sc_carpdev = ifp;

	sc->sc_carpaddr.s_addr = htonl(INADDR_CARP_GROUP);
	sc->sc_carpaddr6.s6_addr16[0] = IPV6_ADDR_INT16_MLL;
	sc->sc_carpaddr6.s6_addr8[15] = 0x12;

	sc->sc_vrrp_adv_inter = 100;
	sc->sc_vrrp_master_inter = sc->sc_vrrp_adv_inter;
	sc->sc_vrrp_prio = 100;

	CARP_LOCK_INIT(sc);
#ifdef INET
	callout_init_mtx(&sc->sc_md_tmo, &sc->sc_mtx, CALLOUT_RETURNUNLOCKED);
#endif
#ifdef INET6
	callout_init_mtx(&sc->sc_md6_tmo, &sc->sc_mtx, CALLOUT_RETURNUNLOCKED);
#endif
	callout_init_mtx(&sc->sc_ad_tmo, &sc->sc_mtx, CALLOUT_RETURNUNLOCKED);

	CIF_LOCK(cif);
	TAILQ_INSERT_TAIL(&cif->cif_vrs, sc, sc_list);
	CIF_UNLOCK(cif);

	mtx_lock(&carp_mtx);
	LIST_INSERT_HEAD(&carp_list, sc, sc_next);
	mtx_unlock(&carp_mtx);

	return (sc);
}

static void
carp_grow_ifas(struct carp_softc *sc)
{
	struct ifaddr **new;

	new = malloc(sc->sc_ifasiz * 2, M_CARP, M_WAITOK | M_ZERO);
	CARP_LOCK(sc);
	bcopy(sc->sc_ifas, new, sc->sc_ifasiz);
	free(sc->sc_ifas, M_CARP);
	sc->sc_ifas = new;
	sc->sc_ifasiz *= 2;
	CARP_UNLOCK(sc);
}

static void
carp_destroy(struct carp_softc *sc)
{
	struct ifnet *ifp = sc->sc_carpdev;
	struct carp_if *cif = ifp->if_carp;

	sx_assert(&carp_sx, SA_XLOCKED);

	if (sc->sc_suppress)
		carp_demote_adj(-V_carp_ifdown_adj, "vhid removed");
	CARP_UNLOCK(sc);

	CIF_LOCK(cif);
	TAILQ_REMOVE(&cif->cif_vrs, sc, sc_list);
	CIF_UNLOCK(cif);

	mtx_lock(&carp_mtx);
	LIST_REMOVE(sc, sc_next);
	mtx_unlock(&carp_mtx);

	callout_drain(&sc->sc_ad_tmo);
#ifdef INET
	callout_drain(&sc->sc_md_tmo);
#endif
#ifdef INET6
	callout_drain(&sc->sc_md6_tmo);
#endif
	CARP_LOCK_DESTROY(sc);

	free(sc->sc_ifas, M_CARP);
	free(sc, M_CARP);
}

static struct carp_if*
carp_alloc_if(struct ifnet *ifp)
{
	struct carp_if *cif;
	int error;

	cif = malloc(sizeof(*cif), M_CARP, M_WAITOK|M_ZERO);

	if ((error = ifpromisc(ifp, 1)) != 0)
		printf("%s: ifpromisc(%s) failed: %d\n",
		    __func__, if_name(ifp), error);
	else
		cif->cif_flags |= CIF_PROMISC;

	CIF_LOCK_INIT(cif);
	cif->cif_ifp = ifp;
	TAILQ_INIT(&cif->cif_vrs);

	IF_ADDR_WLOCK(ifp);
	ifp->if_carp = cif;
	if_ref(ifp);
	IF_ADDR_WUNLOCK(ifp);

	return (cif);
}

static void
carp_free_if(struct carp_if *cif)
{
	struct ifnet *ifp = cif->cif_ifp;

	CIF_LOCK_ASSERT(cif);
	KASSERT(TAILQ_EMPTY(&cif->cif_vrs), ("%s: softc list not empty",
	    __func__));

	IF_ADDR_WLOCK(ifp);
	ifp->if_carp = NULL;
	IF_ADDR_WUNLOCK(ifp);

	CIF_LOCK_DESTROY(cif);

	if (cif->cif_flags & CIF_PROMISC)
		ifpromisc(ifp, 0);
	if_rele(ifp);

	free(cif, M_CARP);
}

static bool
carp_carprcp(void *arg, struct carp_softc *sc, int priv)
{
	struct carpreq *carpr = arg;

	CARP_LOCK(sc);
	carpr->carpr_state = sc->sc_state;
	carpr->carpr_vhid = sc->sc_vhid;
	carpr->carpr_advbase = sc->sc_advbase;
	carpr->carpr_advskew = sc->sc_advskew;
	if (priv)
		bcopy(sc->sc_key, carpr->carpr_key, sizeof(carpr->carpr_key));
	else
		bzero(carpr->carpr_key, sizeof(carpr->carpr_key));
	CARP_UNLOCK(sc);

	return (true);
}

static int
carp_ioctl_set(if_t ifp, struct carpkreq *carpr)
{
	struct epoch_tracker et;
	struct carp_softc *sc = NULL;
	int error = 0;

	if (carpr->carpr_vhid <= 0 || carpr->carpr_vhid > CARP_MAXVHID ||
	    carpr->carpr_advbase < 0 || carpr->carpr_advskew < 0 ||
	    (carpr->carpr_version != CARP_VERSION_CARP &&
	    carpr->carpr_version != CARP_VERSION_VRRPv3)) {
		return (EINVAL);
	}

	if (ifp->if_carp) {
		IFNET_FOREACH_CARP(ifp, sc)
			if (sc->sc_vhid == carpr->carpr_vhid)
				break;
	}
	if (sc == NULL) {
		sc = carp_alloc(ifp);
		CARP_LOCK(sc);
		sc->sc_vhid = carpr->carpr_vhid;
		LLADDR(&sc->sc_addr)[0] = 0;
		LLADDR(&sc->sc_addr)[1] = 0;
		LLADDR(&sc->sc_addr)[2] = 0x5e;
		LLADDR(&sc->sc_addr)[3] = 0;
		LLADDR(&sc->sc_addr)[4] = 1;
		LLADDR(&sc->sc_addr)[5] = sc->sc_vhid;
	} else
		CARP_LOCK(sc);
	sc->sc_version = carpr->carpr_version;
	if (carpr->carpr_advbase > 0) {
		if (carpr->carpr_advbase > 255 ||
		    carpr->carpr_advbase < CARP_DFLTINTV) {
			error = EINVAL;
			goto out;
		}
		sc->sc_advbase = carpr->carpr_advbase;
	}
	if (carpr->carpr_advskew >= 255) {
		error = EINVAL;
		goto out;
	}
	sc->sc_advskew = carpr->carpr_advskew;
	if (carpr->carpr_addr.s_addr != INADDR_ANY)
		sc->sc_carpaddr = carpr->carpr_addr;
	if (! IN6_IS_ADDR_UNSPECIFIED(&carpr->carpr_addr6)) {
		memcpy(&sc->sc_carpaddr6, &carpr->carpr_addr6,
		    sizeof(sc->sc_carpaddr6));
	}
	if (carpr->carpr_key[0] != '\0') {
		bcopy(carpr->carpr_key, sc->sc_key, sizeof(sc->sc_key));
		carp_hmac_prepare(sc);
	}
	if (carpr->carpr_vrrp_priority != 0)
		sc->sc_vrrp_prio = carpr->carpr_vrrp_priority;
	if (carpr->carpr_vrrp_adv_inter)
		sc->sc_vrrp_adv_inter = carpr->carpr_vrrp_adv_inter;

	if (sc->sc_state != INIT &&
	    carpr->carpr_state != sc->sc_state) {
		switch (carpr->carpr_state) {
		case BACKUP:
			callout_stop(&sc->sc_ad_tmo);
			carp_set_state(sc, BACKUP,
			    "user requested via ifconfig");
			carp_setrun(sc, 0);
			carp_delroute(sc);
			break;
		case MASTER:
			NET_EPOCH_ENTER(et);
			carp_master_down_locked(sc,
			    "user requested via ifconfig");
			NET_EPOCH_EXIT(et);
			break;
		default:
			break;
		}
	}

out:
	CARP_UNLOCK(sc);

	return (error);
}

static int
carp_ioctl_get(if_t ifp, struct ucred *cred, struct carpreq *carpr,
    bool (*outfn)(void *, struct carp_softc *, int), void *arg)
{
	int priveleged;
	struct carp_softc *sc;

	if (carpr->carpr_vhid < 0 || carpr->carpr_vhid > CARP_MAXVHID)
		return (EINVAL);
	if (carpr->carpr_count < 1)
		return (EMSGSIZE);
	if (ifp->if_carp == NULL)
		return (ENOENT);

	priveleged = (priv_check_cred(cred, PRIV_NETINET_CARP) == 0);
	if (carpr->carpr_vhid != 0) {
		IFNET_FOREACH_CARP(ifp, sc)
			if (sc->sc_vhid == carpr->carpr_vhid)
				break;
		if (sc == NULL)
			return (ENOENT);

		if (! outfn(arg, sc, priveleged))
			return (ENOMEM);
		carpr->carpr_count = 1;
	} else  {
		int count;

		count = 0;
		IFNET_FOREACH_CARP(ifp, sc)
			count++;

		if (count > carpr->carpr_count)
			return (EMSGSIZE);

		IFNET_FOREACH_CARP(ifp, sc) {
			if (! outfn(arg, sc, priveleged))
				return (ENOMEM);
			carpr->carpr_count = count;
		}
	}

	return (0);
}

int
carp_ioctl(struct ifreq *ifr, u_long cmd, struct thread *td)
{
	struct carpreq carpr;
	struct carpkreq carprk = { };
	struct ifnet *ifp;
	int error = 0;

	if ((error = copyin(ifr_data_get_ptr(ifr), &carpr, sizeof carpr)))
		return (error);

	ifp = ifunit_ref(ifr->ifr_name);
	if ((error = carp_is_supported_if(ifp)) != 0)
		goto out;

	if ((ifp->if_flags & IFF_MULTICAST) == 0) {
		error = EADDRNOTAVAIL;
		goto out;
	}

	sx_xlock(&carp_sx);
	switch (cmd) {
	case SIOCSVH:
		if ((error = priv_check(td, PRIV_NETINET_CARP)))
			break;

		memcpy(&carprk, &carpr, sizeof(carpr));
		error = carp_ioctl_set(ifp, &carprk);
		break;

	case SIOCGVH:
		error = carp_ioctl_get(ifp, td->td_ucred, &carpr,
		    carp_carprcp, &carpr);
		if (error == 0) {
			error = copyout(&carpr,
			    (char *)ifr_data_get_ptr(ifr),
			    carpr.carpr_count * sizeof(carpr));
		}
		break;
	default:
		error = EINVAL;
	}
	sx_xunlock(&carp_sx);

out:
	if (ifp != NULL)
		if_rele(ifp);

	return (error);
}

static int
carp_get_vhid(struct ifaddr *ifa)
{

	if (ifa == NULL || ifa->ifa_carp == NULL)
		return (0);

	return (ifa->ifa_carp->sc_vhid);
}

int
carp_attach(struct ifaddr *ifa, int vhid)
{
	struct ifnet *ifp = ifa->ifa_ifp;
	struct carp_if *cif = ifp->if_carp;
	struct carp_softc *sc;
	int index, error;

	KASSERT(ifa->ifa_carp == NULL, ("%s: ifa %p attached", __func__, ifa));

	switch (ifa->ifa_addr->sa_family) {
#ifdef INET
	case AF_INET:
#endif
#ifdef INET6
	case AF_INET6:
#endif
		break;
	default:
		return (EPROTOTYPE);
	}

	sx_xlock(&carp_sx);
	if (ifp->if_carp == NULL) {
		sx_xunlock(&carp_sx);
		return (ENOPROTOOPT);
	}

	IFNET_FOREACH_CARP(ifp, sc)
		if (sc->sc_vhid == vhid)
			break;
	if (sc == NULL) {
		sx_xunlock(&carp_sx);
		return (ENOENT);
	}

	error = carp_multicast_setup(cif, ifa->ifa_addr->sa_family);
	if (error) {
		CIF_FREE(cif);
		sx_xunlock(&carp_sx);
		return (error);
	}

	index = sc->sc_naddrs + sc->sc_naddrs6 + 1;
	if (index > sc->sc_ifasiz / sizeof(struct ifaddr *))
		carp_grow_ifas(sc);

	switch (ifa->ifa_addr->sa_family) {
#ifdef INET
	case AF_INET:
		cif->cif_naddrs++;
		sc->sc_naddrs++;
		break;
#endif
#ifdef INET6
	case AF_INET6:
		cif->cif_naddrs6++;
		sc->sc_naddrs6++;
		break;
#endif
	}

	ifa_ref(ifa);

	CARP_LOCK(sc);
	sc->sc_ifas[index - 1] = ifa;
	ifa->ifa_carp = sc;
	carp_hmac_prepare(sc);
	carp_sc_state(sc);
	CARP_UNLOCK(sc);

	sx_xunlock(&carp_sx);

	return (0);
}

void
carp_detach(struct ifaddr *ifa, bool keep_cif)
{
	struct ifnet *ifp = ifa->ifa_ifp;
	struct carp_if *cif = ifp->if_carp;
	struct carp_softc *sc = ifa->ifa_carp;
	int i, index;

	KASSERT(sc != NULL, ("%s: %p not attached", __func__, ifa));

	sx_xlock(&carp_sx);

	CARP_LOCK(sc);
	/* Shift array. */
	index = sc->sc_naddrs + sc->sc_naddrs6;
	for (i = 0; i < index; i++)
		if (sc->sc_ifas[i] == ifa)
			break;
	KASSERT(i < index, ("%s: %p no backref", __func__, ifa));
	for (; i < index - 1; i++)
		sc->sc_ifas[i] = sc->sc_ifas[i+1];
	sc->sc_ifas[index - 1] = NULL;

	switch (ifa->ifa_addr->sa_family) {
#ifdef INET
	case AF_INET:
		cif->cif_naddrs--;
		sc->sc_naddrs--;
		break;
#endif
#ifdef INET6
	case AF_INET6:
		cif->cif_naddrs6--;
		sc->sc_naddrs6--;
		break;
#endif
	}

	carp_ifa_delroute(ifa);
	carp_multicast_cleanup(cif, ifa->ifa_addr->sa_family);

	ifa->ifa_carp = NULL;
	ifa_free(ifa);

	carp_hmac_prepare(sc);
	carp_sc_state(sc);

	if (!keep_cif && sc->sc_naddrs == 0 && sc->sc_naddrs6 == 0)
		carp_destroy(sc);
	else
		CARP_UNLOCK(sc);

	if (!keep_cif)
		CIF_FREE(cif);

	sx_xunlock(&carp_sx);
}

static void
carp_set_state(struct carp_softc *sc, int state, const char *reason)
{

	CARP_LOCK_ASSERT(sc);

	if (sc->sc_state != state) {
		const char *carp_states[] = { CARP_STATES };
		char subsys[IFNAMSIZ+5];

		snprintf(subsys, IFNAMSIZ+5, "%u@%s", sc->sc_vhid,
		    if_name(sc->sc_carpdev));

		CARP_LOG("%s: %s -> %s (%s)\n", subsys,
		    carp_states[sc->sc_state], carp_states[state], reason);

		sc->sc_state = state;

		devctl_notify("CARP", subsys, carp_states[state], NULL);
	}
}

static void
carp_linkstate(struct ifnet *ifp)
{
	struct carp_softc *sc;

	CIF_LOCK(ifp->if_carp);
	IFNET_FOREACH_CARP(ifp, sc) {
		CARP_LOCK(sc);
		carp_sc_state(sc);
		CARP_UNLOCK(sc);
	}
	CIF_UNLOCK(ifp->if_carp);
}

static void
carp_sc_state(struct carp_softc *sc)
{

	CARP_LOCK_ASSERT(sc);

	if (sc->sc_carpdev->if_link_state != LINK_STATE_UP ||
	    !(sc->sc_carpdev->if_flags & IFF_UP) ||
	    !V_carp_allow) {
		callout_stop(&sc->sc_ad_tmo);
#ifdef INET
		callout_stop(&sc->sc_md_tmo);
#endif
#ifdef INET6
		callout_stop(&sc->sc_md6_tmo);
#endif
		carp_set_state(sc, INIT, "hardware interface down");
		carp_setrun(sc, 0);
		carp_delroute(sc);
		if (!sc->sc_suppress)
			carp_demote_adj(V_carp_ifdown_adj, "interface down");
		sc->sc_suppress = 1;
	} else {
		carp_set_state(sc, INIT, "hardware interface up");
		carp_setrun(sc, 0);
		if (sc->sc_suppress)
			carp_demote_adj(-V_carp_ifdown_adj, "interface up");
		sc->sc_suppress = 0;
	}
}

static void
carp_demote_adj(int adj, char *reason)
{
	atomic_add_int(&V_carp_demotion, adj);
	CARP_LOG("demoted by %d to %d (%s)\n", adj, V_carp_demotion, reason);
	taskqueue_enqueue(taskqueue_swi, &carp_sendall_task);
}

static int
carp_allow_sysctl(SYSCTL_HANDLER_ARGS)
{
	int new, error;
	struct carp_softc *sc;

	new = V_carp_allow;
	error = sysctl_handle_int(oidp, &new, 0, req);
	if (error || !req->newptr)
		return (error);

	if (V_carp_allow != new) {
		V_carp_allow = new;

		mtx_lock(&carp_mtx);
		LIST_FOREACH(sc, &carp_list, sc_next) {
			CARP_LOCK(sc);
			if (curvnet == sc->sc_carpdev->if_vnet)
				carp_sc_state(sc);
			CARP_UNLOCK(sc);
		}
		mtx_unlock(&carp_mtx);
	}

	return (0);
}

static int
carp_dscp_sysctl(SYSCTL_HANDLER_ARGS)
{
	int new, error;

	new = V_carp_dscp;
	error = sysctl_handle_int(oidp, &new, 0, req);
	if (error || !req->newptr)
		return (error);

	if (new < 0 || new > 63)
		return (EINVAL);

	V_carp_dscp = new;

	return (0);
}

static int
carp_demote_adj_sysctl(SYSCTL_HANDLER_ARGS)
{
	int new, error;

	new = V_carp_demotion;
	error = sysctl_handle_int(oidp, &new, 0, req);
	if (error || !req->newptr)
		return (error);

	carp_demote_adj(new, "sysctl");

	return (0);
}

static int
nlattr_get_carp_key(struct nlattr *nla, struct nl_pstate *npt, const void *arg, void *target)
{
	if (__predict_false(NLA_DATA_LEN(nla) > CARP_KEY_LEN))
		return (EINVAL);

	memcpy(target, NLA_DATA_CONST(nla), NLA_DATA_LEN(nla));
	return (0);
}

struct carp_nl_send_args {
	struct nlmsghdr *hdr;
	struct nl_pstate *npt;
};

static bool
carp_nl_send(void *arg, struct carp_softc *sc, int priv)
{
	struct carp_nl_send_args *nlsa = arg;
	struct nlmsghdr *hdr = nlsa->hdr;
	struct nl_pstate *npt = nlsa->npt;
	struct nl_writer *nw = npt->nw;
	struct genlmsghdr *ghdr_new;

	if (!nlmsg_reply(nw, hdr, sizeof(struct genlmsghdr))) {
		nlmsg_abort(nw);
		return (false);
	}

	ghdr_new = nlmsg_reserve_object(nw, struct genlmsghdr);
	if (ghdr_new == NULL) {
		nlmsg_abort(nw);
		return (false);
	}

	ghdr_new->cmd = CARP_NL_CMD_GET;
	ghdr_new->version = 0;
	ghdr_new->reserved = 0;

	CARP_LOCK(sc);

	nlattr_add_u32(nw, CARP_NL_VHID, sc->sc_vhid);
	nlattr_add_u32(nw, CARP_NL_STATE, sc->sc_state);
	nlattr_add_s32(nw, CARP_NL_ADVBASE, sc->sc_advbase);
	nlattr_add_s32(nw, CARP_NL_ADVSKEW, sc->sc_advskew);
	nlattr_add_in_addr(nw, CARP_NL_ADDR, &sc->sc_carpaddr);
	nlattr_add_in6_addr(nw, CARP_NL_ADDR6, &sc->sc_carpaddr6);
	nlattr_add_u8(nw, CARP_NL_VERSION, sc->sc_version);
	nlattr_add_u8(nw, CARP_NL_VRRP_PRIORITY, sc->sc_vrrp_prio);
	nlattr_add_u16(nw, CARP_NL_VRRP_ADV_INTER, sc->sc_vrrp_adv_inter);

	if (priv)
		nlattr_add(nw, CARP_NL_KEY, sizeof(sc->sc_key), sc->sc_key);

	CARP_UNLOCK(sc);

	if (! nlmsg_end(nw)) {
		nlmsg_abort(nw);
		return (false);
	}

	return (true);
}

struct nl_carp_parsed {
	unsigned int	ifindex;
	char		*ifname;
	uint32_t	state;
	uint32_t	vhid;
	int32_t		advbase;
	int32_t		advskew;
	char		key[CARP_KEY_LEN];
	struct in_addr	addr;
	struct in6_addr	addr6;
	carp_version_t	version;
	uint8_t		vrrp_prio;
	uint16_t	vrrp_adv_inter;
};

#define	_IN(_field)	offsetof(struct genlmsghdr, _field)
#define	_OUT(_field)	offsetof(struct nl_carp_parsed, _field)

static const struct nlattr_parser nla_p_set[] = {
	{ .type = CARP_NL_VHID, .off = _OUT(vhid), .cb = nlattr_get_uint32 },
	{ .type = CARP_NL_STATE, .off = _OUT(state), .cb = nlattr_get_uint32 },
	{ .type = CARP_NL_ADVBASE, .off = _OUT(advbase), .cb = nlattr_get_uint32 },
	{ .type = CARP_NL_ADVSKEW, .off = _OUT(advskew), .cb = nlattr_get_uint32 },
	{ .type = CARP_NL_KEY, .off = _OUT(key), .cb = nlattr_get_carp_key },
	{ .type = CARP_NL_IFINDEX, .off = _OUT(ifindex), .cb = nlattr_get_uint32 },
	{ .type = CARP_NL_ADDR, .off = _OUT(addr), .cb = nlattr_get_in_addr },
	{ .type = CARP_NL_ADDR6, .off = _OUT(addr6), .cb = nlattr_get_in6_addr },
	{ .type = CARP_NL_IFNAME, .off = _OUT(ifname), .cb = nlattr_get_string },
	{ .type = CARP_NL_VERSION, .off = _OUT(version), .cb = nlattr_get_uint8 },
	{ .type = CARP_NL_VRRP_PRIORITY, .off = _OUT(vrrp_prio), .cb = nlattr_get_uint8 },
	{ .type = CARP_NL_VRRP_ADV_INTER, .off = _OUT(vrrp_adv_inter), .cb = nlattr_get_uint16 },
};
static const struct nlfield_parser nlf_p_set[] = {
};
NL_DECLARE_PARSER(carp_parser, struct genlmsghdr, nlf_p_set, nla_p_set);
#undef _IN
#undef _OUT


static int
carp_nl_get(struct nlmsghdr *hdr, struct nl_pstate *npt)
{
	struct nl_carp_parsed attrs = { };
	struct carp_nl_send_args args;
	struct carpreq carpr = { };
	struct epoch_tracker et;
	if_t ifp = NULL;
	int error;

	error = nl_parse_nlmsg(hdr, &carp_parser, npt, &attrs);
	if (error != 0)
		return (error);

	NET_EPOCH_ENTER(et);
	if (attrs.ifname != NULL)
		ifp = ifunit_ref(attrs.ifname);
	else if (attrs.ifindex != 0)
		ifp = ifnet_byindex_ref(attrs.ifindex);
	NET_EPOCH_EXIT(et);

	if ((error = carp_is_supported_if(ifp)) != 0)
		goto out;

	hdr->nlmsg_flags |= NLM_F_MULTI;
	args.hdr = hdr;
	args.npt = npt;

	carpr.carpr_vhid = attrs.vhid;
	carpr.carpr_count = CARP_MAXVHID;

	sx_xlock(&carp_sx);
	error = carp_ioctl_get(ifp, nlp_get_cred(npt->nlp), &carpr,
	    carp_nl_send, &args);
	sx_xunlock(&carp_sx);

	if (! nlmsg_end_dump(npt->nw, error, hdr))
		error = ENOMEM;

out:
	if (ifp != NULL)
		if_rele(ifp);

	return (error);
}

static int
carp_nl_set(struct nlmsghdr *hdr, struct nl_pstate *npt)
{
	struct nl_carp_parsed attrs = { };
	struct carpkreq carpr;
	struct epoch_tracker et;
	if_t ifp = NULL;
	int error;

	error = nl_parse_nlmsg(hdr, &carp_parser, npt, &attrs);
	if (error != 0)
		return (error);

	if (attrs.vhid <= 0 || attrs.vhid > CARP_MAXVHID)
		return (EINVAL);
	if (attrs.state > CARP_MAXSTATE)
		return (EINVAL);
	if (attrs.advbase < 0 || attrs.advskew < 0)
		return (EINVAL);
	if (attrs.advbase > 255)
		return (EINVAL);
	if (attrs.advskew >= 255)
		return (EINVAL);
	if (attrs.version == 0)
		attrs.version = CARP_VERSION_CARP;
	if (attrs.version != CARP_VERSION_CARP &&
	    attrs.version != CARP_VERSION_VRRPv3)
		return (EINVAL);
	if (attrs.vrrp_adv_inter > VRRP_MAX_INTERVAL)
		return (EINVAL);

	NET_EPOCH_ENTER(et);
	if (attrs.ifname != NULL)
		ifp = ifunit_ref(attrs.ifname);
	else if (attrs.ifindex != 0)
		ifp = ifnet_byindex_ref(attrs.ifindex);
	NET_EPOCH_EXIT(et);

	if ((error = carp_is_supported_if(ifp)) != 0)
		goto out;

	if ((ifp->if_flags & IFF_MULTICAST) == 0) {
		error = EADDRNOTAVAIL;
		goto out;
	}

	carpr.carpr_count = 1;
	carpr.carpr_vhid = attrs.vhid;
	carpr.carpr_state = attrs.state;
	carpr.carpr_advbase = attrs.advbase;
	carpr.carpr_advskew = attrs.advskew;
	carpr.carpr_addr = attrs.addr;
	carpr.carpr_addr6 = attrs.addr6;
	carpr.carpr_version = attrs.version;
	carpr.carpr_vrrp_priority = attrs.vrrp_prio;
	carpr.carpr_vrrp_adv_inter = attrs.vrrp_adv_inter;

	memcpy(&carpr.carpr_key, &attrs.key, sizeof(attrs.key));

	sx_xlock(&carp_sx);
	error = carp_ioctl_set(ifp, &carpr);
	sx_xunlock(&carp_sx);

out:
	if (ifp != NULL)
		if_rele(ifp);

	return (error);
}

static const struct nlhdr_parser *all_parsers[] = {
	&carp_parser
};

static const struct genl_cmd carp_cmds[] = {
	{
		.cmd_num = CARP_NL_CMD_GET,
		.cmd_name = "SIOCGVH",
		.cmd_cb = carp_nl_get,
		.cmd_flags = GENL_CMD_CAP_DO | GENL_CMD_CAP_DUMP |
		    GENL_CMD_CAP_HASPOL,
	},
	{
		.cmd_num = CARP_NL_CMD_SET,
		.cmd_name = "SIOCSVH",
		.cmd_cb = carp_nl_set,
		.cmd_flags = GENL_CMD_CAP_DO | GENL_CMD_CAP_HASPOL,
		.cmd_priv = PRIV_NETINET_CARP,
	},
};

static void
carp_nl_register(void)
{
	bool ret __diagused;
	int family_id __diagused;

	NL_VERIFY_PARSERS(all_parsers);
	family_id = genl_register_family(CARP_NL_FAMILY_NAME, 0, 2,
	    CARP_NL_CMD_MAX);
	MPASS(family_id != 0);

	ret = genl_register_cmds(CARP_NL_FAMILY_NAME, carp_cmds,
	    NL_ARRAY_LEN(carp_cmds));
	MPASS(ret);
}

static void
carp_nl_unregister(void)
{
	genl_unregister_family(CARP_NL_FAMILY_NAME);
}

static void
carp_mod_cleanup(void)
{

	carp_nl_unregister();

#ifdef INET
	(void)ipproto_unregister(IPPROTO_CARP);
	carp_iamatch_p = NULL;
#endif
#ifdef INET6
	(void)ip6proto_unregister(IPPROTO_CARP);
	carp_iamatch6_p = NULL;
	carp_macmatch6_p = NULL;
#endif
	carp_ioctl_p = NULL;
	carp_attach_p = NULL;
	carp_detach_p = NULL;
	carp_get_vhid_p = NULL;
	carp_linkstate_p = NULL;
	carp_forus_p = NULL;
	carp_output_p = NULL;
	carp_demote_adj_p = NULL;
	carp_master_p = NULL;
	mtx_unlock(&carp_mtx);
	taskqueue_drain(taskqueue_swi, &carp_sendall_task);
	mtx_destroy(&carp_mtx);
	sx_destroy(&carp_sx);
}

static void
ipcarp_sysinit(void)
{

	/* Load allow as tunable so to postpone carp start after module load */
	TUNABLE_INT_FETCH("net.inet.carp.allow", &V_carp_allow);
}
VNET_SYSINIT(ip_carp, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY, ipcarp_sysinit, NULL);

static int
carp_mod_load(void)
{
	int err;

	mtx_init(&carp_mtx, "carp_mtx", NULL, MTX_DEF);
	sx_init(&carp_sx, "carp_sx");
	LIST_INIT(&carp_list);
	carp_get_vhid_p = carp_get_vhid;
	carp_forus_p = carp_forus;
	carp_output_p = carp_output;
	carp_linkstate_p = carp_linkstate;
	carp_ioctl_p = carp_ioctl;
	carp_attach_p = carp_attach;
	carp_detach_p = carp_detach;
	carp_demote_adj_p = carp_demote_adj;
	carp_master_p = carp_master;
#ifdef INET6
	carp_iamatch6_p = carp_iamatch6;
	carp_macmatch6_p = carp_macmatch6;
	err = ip6proto_register(IPPROTO_CARP, carp6_input, NULL);
	if (err) {
		printf("carp: error %d registering with INET6\n", err);
		carp_mod_cleanup();
		return (err);
	}
#endif
#ifdef INET
	carp_iamatch_p = carp_iamatch;
	err = ipproto_register(IPPROTO_CARP, carp_input, NULL);
	if (err) {
		printf("carp: error %d registering with INET\n", err);
		carp_mod_cleanup();
		return (err);
	}
#endif

	carp_nl_register();

	return (0);
}

static int
carp_modevent(module_t mod, int type, void *data)
{
	switch (type) {
	case MOD_LOAD:
		return carp_mod_load();
		/* NOTREACHED */
	case MOD_UNLOAD:
		mtx_lock(&carp_mtx);
		if (LIST_EMPTY(&carp_list))
			carp_mod_cleanup();
		else {
			mtx_unlock(&carp_mtx);
			return (EBUSY);
		}
		break;

	default:
		return (EINVAL);
	}

	return (0);
}

static moduledata_t carp_mod = {
	"carp",
	carp_modevent,
	0
};

DECLARE_MODULE(carp, carp_mod, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY);