/*-
 * 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 "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 */
        uint8_t                 sc_addr[ETHER_ADDR_LEN];        /* 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;
        union {
                struct { /* sc_version == CARP_VERSION_CARP */
                        int             sc_advskew;
                        int             sc_advbase;
                        struct in_addr  sc_carpaddr;
                        struct in6_addr sc_carpaddr6;
                        uint64_t        sc_counter;
                        bool            sc_init_counter;
#define CARP_HMAC_PAD   64
                        unsigned char sc_key[CARP_KEY_LEN];
                        unsigned char sc_pad[CARP_HMAC_PAD];
                        SHA1_CTX sc_sha1;
                };
                struct { /* sc_version == CARP_VERSION_VRRPv3 */
                        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

        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
};

/*
 * 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:
 *
 * - 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)))

/*
 * VRRPv3 priority is the inverse of CARP advskew: higher is better.
 * Subtract the global demotion counter and clamp to [0, 254].
 * Priority 255 (IP address owner) is never demoted.
 */
#define DEMOTE_VRRP_PRIO(sc)                                    \
    ((sc)->sc_vrrp_prio == 255 ? 255 :                          \
    (((int)(sc)->sc_vrrp_prio - V_carp_demotion < 0) ? 0 :      \
    (((int)(sc)->sc_vrrp_prio - V_carp_demotion > 254) ? 254 :  \
    (int)(sc)->sc_vrrp_prio - 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 *, carp_version_t, int);
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 = LIST_HEAD_INITIALIZER(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);
        MPASS(sc->sc_version == CARP_VERSION_CARP);

        /* 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;
        struct vrrpv3_header *vh;
        int iplen;
        int minlen;
        int totlen;

        iplen = *offp;
        *mp = NULL;

        CARPSTATS_INC(carps_ipackets);

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

        /* 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 (m->m_len < iplen + sizeof(*vh)) {
                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 *);
        totlen = ntohs(ip->ip_len);
        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 (m->m_len < iplen + minlen) {
                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);
        }

        switch (vh->vrrp_version) {
        case CARP_VERSION_CARP: {
                struct carp_header *ch;

                /* verify the CARP checksum */
                if (in_cksum_skip(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);
                        break;
                }
                ch = (struct carp_header *)((char *)ip + iplen);
                carp_input_c(m, ch, AF_INET, ip->ip_ttl);
                break;
        }
        case CARP_VERSION_VRRPv3: {
                uint16_t phdrcksum;

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

        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 (m->m_len < sizeof(*ip6) + minlen) {
                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));
        }

        switch (vh->vrrp_version) {
        case CARP_VERSION_CARP: {
                struct carp_header *ch;

                /* verify the CARP checksum */
                if (in_cksum_skip(m, *offp + sizeof(struct carp_header),
                    *offp)) {
                        CARPSTATS_INC(carps_badsum);
                        CARP_DEBUG("%s: checksum failed, on %s\n", __func__,
                            if_name(m->m_pkthdr.rcvif));
                        m_freem(m);
                        break;
                }
                ch = (struct carp_header *)((char *)ip6 + sizeof(*ip6));
                carp_input_c(m, ch, AF_INET6, ip6->ip6_hlim);
                break;
        }
        case CARP_VERSION_VRRPv3: {
                uint16_t phdrcksum;

                phdrcksum = in6_cksum_pseudo(ip6, ntohs(ip6->ip6_plen),
                    ip6->ip6_nxt, 0);
                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();
        MPASS(ch->carp_version == CARP_VERSION_CARP);

        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 (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(ntohl(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 = false;
        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();
        MPASS(vh->vrrp_version == CARP_VERSION_VRRPv3);

        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 (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 > DEMOTE_VRRP_PRIO(sc)) {
                        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 < DEMOTE_VRRP_PRIO(sc))) {
                        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(sc->sc_vhid),
            M_NOWAIT)) == NULL) {
                m_freem(m);
                CARPSTATS_INC(carps_onomem);
                return (ENOMEM);
        }
        bcopy(&sc->sc_vhid, mtag + 1, sizeof(sc->sc_vhid));
        m_tag_prepend(m, mtag);

        return (0);
}

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

        MPASS(sc->sc_version == CARP_VERSION_CARP);

        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);
}

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(ntohl(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, V_ip_random_id);

                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));
                carp_prepare_ad(m, sc, ch_ptr);
                if (IN_MULTICAST(ntohl(sc->sc_carpaddr.s_addr)) &&
                    carp_tag(sc, m) != 0)
                        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));
                carp_prepare_ad(m, sc, ch_ptr);
                if (IN6_IS_ADDR_MULTICAST(&sc->sc_carpaddr6) &&
                    carp_tag(sc, m) != 0)
                        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 = DEMOTE_VRRP_PRIO(sc),
            .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, V_ip_random_id);

                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, 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 = sc->sc_addr;
                return (1);
        }

        return (0);
}
#endif

#ifdef INET6
static void
carp_send_na(struct carp_softc *sc)
{
        struct ifaddr *ifa;
        int flags;

        /*
         * Sending Unsolicited Neighbor Advertisements
         *
         * If the node is a router, we MUST set the Router flag to one.
         * We set Override flag to one and send link-layer address option,
         * thus neighboring nodes will install the new link-layer address.
         */
        flags = ND_NA_FLAG_OVERRIDE;
        if (V_ip6_forwarding)
                flags |= ND_NA_FLAG_ROUTER;
        CARP_FOREACH_IFA(sc, ifa) {
                if (ifa->ifa_addr->sa_family != AF_INET6)
                        continue;
                /*
                 * We use unspecified address as destination here to avoid
                 * scope initialization for each call.
                 * nd6_na_output() will use all nodes multicast address if
                 * destinaion address is unspecified.
                 */
                nd6_na_output(sc->sc_carpdev, &in6addr_any, IFA_IN6(ifa),
                    flags, ND6_NA_OPT_LLA | ND6_NA_CARP_MASTER, NULL);
                DELAY(1000);    /* RetransTimer */
        }
}

/*
 * 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;
        char *mac = NULL;

        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(sc->sc_vhid) + sizeof(sc->sc_addr),
                            M_NOWAIT);
                        if (mtag == NULL) {
                                CARPSTATS_INC(carps_onomem);
                                break;
                        }
                        /* carp_output expects sc_vhid first. */
                        bcopy(&sc->sc_vhid, mtag + 1, sizeof(sc->sc_vhid));
                        /*
                         * Save sc_addr into mtag data after sc_vhid to avoid
                         * possible access to destroyed softc.
                         */
                        mac = (char *)(mtag + 1) + sizeof(sc->sc_vhid);
                        bcopy(sc->sc_addr, mac, sizeof(sc->sc_addr));

                        m_tag_prepend(m, mtag);
                        break;
                }

        return (mac);
}
#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, 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);

                switch (sc->sc_version) {
                case CARP_VERSION_CARP:
                        tv.tv_sec = 3 * sc->sc_advbase;
                        tv.tv_usec = sc->sc_advskew * 1000000 / 256;
                        timeout = tvtohz(&tv);
                        break;
                case CARP_VERSION_VRRPv3:
                        /* 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 */
                        break;
                }
                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:
                switch (sc->sc_version) {
                case 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);
                        break;
                case CARP_VERSION_VRRPv3:
                        callout_reset(&sc->sc_ad_tmo,
                            sc->sc_vrrp_adv_inter * hz / 100,
                            carp_callout, sc);
                        break;
                }
                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;
        int vhid;

        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, &vhid, sizeof(vhid));

        /* 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] = 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, carp_version_t version, int vhid)
{
        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);
        *sc = (struct carp_softc ){
                .sc_vhid = vhid,
                .sc_version = version,
                .sc_state = INIT,
                .sc_carpdev = ifp,
                .sc_ifasiz = sizeof(struct ifaddr *),
                .sc_addr = { 0, 0, 0x5e, 0, 1, vhid },
        };
        sc->sc_ifas = malloc(sc->sc_ifasiz, M_CARP, M_WAITOK|M_ZERO);

        switch (version) {
        case CARP_VERSION_CARP:
                sc->sc_advbase = CARP_DFLTINTV;
                sc->sc_init_counter = true;
                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;
                break;
        case CARP_VERSION_VRRPv3:
                sc->sc_vrrp_adv_inter = 100;
                sc->sc_vrrp_master_inter = sc->sc_vrrp_adv_inter;
                sc->sc_vrrp_prio = 100;
                break;
        }

        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 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;
        if (sc->sc_version == CARP_VERSION_CARP)
                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);

        if (sc->sc_version == CARP_VERSION_CARP)
                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 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 _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 },
};
NL_DECLARE_PARSER(carp_parser, struct genlmsghdr, nlf_p_empty, nla_p_set);
#undef _OUT


static int
carp_nl_get(struct nlmsghdr *hdr, struct nl_pstate *npt)
{
        struct nl_carp_parsed attrs = { };
        struct epoch_tracker et;
        struct nl_writer *nw = npt->nw;
        struct carp_softc *sc;
        if_t ifp = NULL;
        int error;
        bool privileged;

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

        if (attrs.vhid < 0 || attrs.vhid > CARP_MAXVHID)
                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_carp == NULL) {
                error = ENOENT;
                goto out;
        }

        hdr->nlmsg_flags |= NLM_F_MULTI;
        privileged = (priv_check_cred(nlp_get_cred(npt->nlp),
            PRIV_NETINET_CARP) == 0);

        sx_xlock(&carp_sx);
        IFNET_FOREACH_CARP(ifp, sc) {
                struct genlmsghdr *ghdr_new;

                if (attrs.vhid != 0 && attrs.vhid != sc->sc_vhid)
                        continue;

                if (!nlmsg_reply(nw, hdr, sizeof(struct genlmsghdr))) {
                        nlmsg_abort(nw);
                        error = ENOMEM;
                        break;
                }

                ghdr_new = nlmsg_reserve_object(nw, struct genlmsghdr);
                if (ghdr_new == NULL) {
                        nlmsg_abort(nw);
                        error = ENOMEM;
                        break;
                }

                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_u8(nw, CARP_NL_VERSION, sc->sc_version);
                switch (sc->sc_version) {
                case CARP_VERSION_CARP:
                        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);
                        if (privileged)
                                nlattr_add(nw, CARP_NL_KEY, sizeof(sc->sc_key),
                                    sc->sc_key);
                        break;
                case CARP_VERSION_VRRPv3:
                        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);
                        break;
                }
                CARP_UNLOCK(sc);

                if (! nlmsg_end(nw)) {
                        nlmsg_abort(nw);
                        error = ENOMEM;
                        break;
                }
        }
        sx_xunlock(&carp_sx);

        if (! nlmsg_end_dump(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 epoch_tracker et;
        struct carp_softc *sc;
        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.version == 0) /* compat with pre-VRRPv3 */
                attrs.version = CARP_VERSION_CARP;
        switch (attrs.version) {
        case CARP_VERSION_CARP:
                if (attrs.advbase < 0 || attrs.advskew < 0)
                        return (EINVAL);
                if (attrs.advbase > 255)
                        return (EINVAL);
                if (attrs.advskew >= 255)
                        return (EINVAL);
                break;
        case CARP_VERSION_VRRPv3:
                if (attrs.vrrp_adv_inter > VRRP_MAX_INTERVAL)
                        return (EINVAL);
                break;
        default:
                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;
        }

        sx_xlock(&carp_sx);
        if (ifp->if_carp) {
                IFNET_FOREACH_CARP(ifp, sc)
                        if (sc->sc_vhid == attrs.vhid)
                                break;
        } else
                sc = NULL;
        if (sc == NULL)
                sc = carp_alloc(ifp, attrs.version, attrs.vhid);
        else if (sc->sc_version != attrs.version) {
                sx_xunlock(&carp_sx);
                error = EINVAL;
                goto out;
        }

        CARP_LOCK(sc);
        switch (sc->sc_version) {
        case CARP_VERSION_CARP:
                if (attrs.advbase != 0)
                        sc->sc_advbase = attrs.advbase;
                sc->sc_advskew = attrs.advskew;
                if (attrs.addr.s_addr != INADDR_ANY)
                        sc->sc_carpaddr = attrs.addr;
                if (!IN6_IS_ADDR_UNSPECIFIED(&attrs.addr6)) {
                        memcpy(&sc->sc_carpaddr6, &attrs.addr6,
                            sizeof(sc->sc_carpaddr6));
                }
                if (attrs.key[0] != '\0') {
                        bcopy(attrs.key, sc->sc_key, sizeof(sc->sc_key));
                        carp_hmac_prepare(sc);
                }
                break;
        case CARP_VERSION_VRRPv3:
                if (attrs.vrrp_prio != 0)
                        sc->sc_vrrp_prio = attrs.vrrp_prio;
                if (attrs.vrrp_adv_inter)
                        sc->sc_vrrp_adv_inter = attrs.vrrp_adv_inter;
                break;
        }

        if (sc->sc_state != INIT && sc->sc_state != attrs.state) {
                switch (attrs.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;
                }
        }
        CARP_UNLOCK(sc);
        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 uint16_t carp_family_id;
static void
carp_nl_register(void)
{
        bool ret __diagused;

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

        ret = genl_register_cmds(carp_family_id, carp_cmds, nitems(carp_cmds));
        MPASS(ret);
}

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

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_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");
        carp_get_vhid_p = carp_get_vhid;
        carp_forus_p = carp_forus;
        carp_output_p = carp_output;
        carp_linkstate_p = carp_linkstate;
        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);