/*
 * Copyright (c) 2002 Michael Shalayeff. All rights reserved.
 * Copyright (c) 2003 Ryan McBride. 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.
 */
/*
 * $FreeBSD: src/sys/netinet/ip_carp.c,v 1.48 2007/02/02 09:39:09 glebius Exp $
 */

#include "opt_carp.h"
#include "opt_inet.h"
#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/in_cksum.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/msgport2.h>
#include <sys/time.h>
#include <sys/proc.h>
#include <sys/caps.h>
#include <sys/sockio.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/thread.h>

#include <machine/stdarg.h>
#include <crypto/sha1.h>

#include <net/bpf.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/route.h>
#include <net/if_clone.h>
#include <net/if_var.h>
#include <net/ifq_var.h>
#include <net/netmsg2.h>
#include <net/netisr2.h>

#ifdef INET
#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/if_ether.h>
#endif

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

#include <netinet/ip_carp.h>

/*
 * Note about carp's MP safe approach:
 *
 * Brief: carp_softc (softc), carp_softc_container (scc)
 *
 * - All configuration operation, e.g. ioctl, add/delete inet addresses
 *   is serialized by netisr0; not by carp's serializer
 *
 * - Backing interface's if_carp and carp_softc's relationship:
 *
 *                +---------+
 *     if_carp -->| carp_if |
 *                +---------+
 *                     |
 *                     |
 *                     V      +---------+
 *                  +-----+   |         |
 *                  | scc |-->|  softc  |
 *                  +-----+   |         |
 *                     |      +---------+
 *                     |
 *                     V      +---------+
 *                  +-----+   |         |
 *                  | scc |-->|  softc  |
 *                  +-----+   |         |
 *                            +---------+
 *
 * - if_carp creation, modification and deletion all happen in netisr0,
 *   as stated previously.  Since if_carp is accessed by multiple netisrs,
 *   the modification to if_carp is conducted in the following way:
 *
 *   Adding carp_softc:
 *
 *   1) Duplicate the old carp_if to new carp_if (ncif), and insert the
 *      to-be-added carp_softc to the new carp_if (ncif):
 *
 *        if_carp                     ncif
 *           |                         |
 *           V                         V
 *      +---------+               +---------+
 *      | carp_if |               | carp_if |
 *      +---------+               +---------+
 *           |                         |
 *           |                         |
 *           V        +-------+        V
 *        +-----+     |       |     +-----+
 *        | scc |---->| softc |<----| scc |
 *        +-----+     |       |     +-----+
 *           |        +-------+        |
 *           |                         |
 *           V        +-------+        V
 *        +-----+     |       |     +-----+
 *        | scc |---->| softc |<----| scc |
 *        +-----+     |       |     +-----+
 *                    +-------+        |
 *                                     |
 *                    +-------+        V
 *                    |       |     +-----+
 *                    | softc |<----| scc |
 *                    |       |     +-----+
 *                    +-------+
 *
 *   2) Switch save if_carp into ocif and switch if_carp to ncif:
 *      
 *          ocif                    if_carp
 *           |                         |
 *           V                         V
 *      +---------+               +---------+
 *      | carp_if |               | carp_if |
 *      +---------+               +---------+
 *           |                         |
 *           |                         |
 *           V        +-------+        V
 *        +-----+     |       |     +-----+
 *        | scc |---->| softc |<----| scc |
 *        +-----+     |       |     +-----+
 *           |        +-------+        |
 *           |                         |
 *           V        +-------+        V
 *        +-----+     |       |     +-----+
 *        | scc |---->| softc |<----| scc |
 *        +-----+     |       |     +-----+
 *                    +-------+        |
 *                                     |
 *                    +-------+        V
 *                    |       |     +-----+
 *                    | softc |<----| scc |
 *                    |       |     +-----+
 *                    +-------+
 *
 *   3) Run netmsg_service_sync(), which will make sure that
 *      ocif is no longer accessed (all network operations
 *      are happened only in network threads).
 *   4) Free ocif -- only carp_if and scc are freed.
 *
 *
 *   Removing carp_softc:
 *
 *   1) Duplicate the old carp_if to new carp_if (ncif); the to-be-deleted
 *      carp_softc will not be duplicated.
 *
 *        if_carp                     ncif
 *           |                         |
 *           V                         V
 *      +---------+               +---------+
 *      | carp_if |               | carp_if |
 *      +---------+               +---------+
 *           |                         |
 *           |                         |
 *           V        +-------+        V
 *        +-----+     |       |     +-----+
 *        | scc |---->| softc |<----| scc |
 *        +-----+     |       |     +-----+
 *           |        +-------+        |
 *           |                         |
 *           V        +-------+        |
 *        +-----+     |       |        |
 *        | scc |---->| softc |        |
 *        +-----+     |       |        |
 *           |        +-------+        |
 *           |                         |
 *           V        +-------+        V
 *        +-----+     |       |     +-----+
 *        | scc |---->| softc |<----| scc |
 *        +-----+     |       |     +-----+
 *                    +-------+
 *
 *   2) Switch save if_carp into ocif and switch if_carp to ncif:
 *      
 *          ocif                    if_carp
 *           |                         |
 *           V                         V
 *      +---------+               +---------+
 *      | carp_if |               | carp_if |
 *      +---------+               +---------+
 *           |                         |
 *           |                         |
 *           V        +-------+        V
 *        +-----+     |       |     +-----+
 *        | scc |---->| softc |<----| scc |
 *        +-----+     |       |     +-----+
 *           |        +-------+        |
 *           |                         |
 *           V        +-------+        |
 *        +-----+     |       |        |
 *        | scc |---->| softc |        |
 *        +-----+     |       |        |
 *           |        +-------+        |
 *           |                         |
 *           V        +-------+        V
 *        +-----+     |       |     +-----+
 *        | scc |---->| softc |<----| scc |
 *        +-----+     |       |     +-----+
 *                    +-------+
 *
 *   3) Run netmsg_service_sync(), which will make sure that
 *      ocif is no longer accessed (all network operations
 *      are happened only in network threads).
 *   4) Free ocif -- only carp_if and scc are freed.
 *
 * - if_carp accessing:
 *   The accessing code should cache the if_carp in a local temporary
 *   variable and accessing the temporary variable along the code path
 *   instead of accessing if_carp later on.
 */

#define CARP_IFNAME             "carp"
#define CARP_IS_RUNNING(ifp)    \
        (((ifp)->if_flags & (IFF_UP | IFF_RUNNING)) == (IFF_UP | IFF_RUNNING))

struct carp_softc;

struct carp_vhaddr {
        uint32_t                vha_flags;      /* CARP_VHAF_ */
        struct in_ifaddr        *vha_ia;        /* carp address */
        struct in_ifaddr        *vha_iaback;    /* backing address */
        TAILQ_ENTRY(carp_vhaddr) vha_link;
};
TAILQ_HEAD(carp_vhaddr_list, carp_vhaddr);

struct netmsg_carp {
        struct netmsg_base      base;
        struct ifnet            *nc_carpdev;
        struct carp_softc       *nc_softc;
        void                    *nc_data;
        size_t                  nc_datalen;
};

struct carp_softc {
        struct arpcom            arpcom;
        struct ifnet            *sc_carpdev;    /* parent interface */
        struct carp_vhaddr_list  sc_vha_list;   /* virtual addr list */

        const struct in_ifaddr  *sc_ia;         /* primary iface address v4 */
        struct ip_moptions       sc_imo;

#ifdef INET6
        struct in6_ifaddr       *sc_ia6;        /* primary iface address v6 */
        struct ip6_moptions      sc_im6o;
#endif /* INET6 */

        enum { INIT = 0, BACKUP, MASTER }
                                 sc_state;
        boolean_t                sc_dead;

        int                      sc_suppress;

        int                      sc_sendad_errors;
#define CARP_SENDAD_MAX_ERRORS  3
        int                      sc_sendad_success;
#define CARP_SENDAD_MIN_SUCCESS 3

        int                      sc_vhid;
        int                      sc_advskew;
        int                      sc_naddrs;     /* actually used IPv4 vha */
        int                      sc_naddrs6;
        int                      sc_advbase;    /* seconds */
        int                      sc_init_counter;
        uint64_t                 sc_counter;

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

        struct callout           sc_ad_tmo;     /* advertisement timeout */
        struct netmsg_carp       sc_ad_msg;     /* adv timeout netmsg */
        struct callout           sc_md_tmo;     /* ip4 master down timeout */
        struct callout           sc_md6_tmo;    /* ip6 master down timeout */
        struct netmsg_carp       sc_md_msg;     /* master down timeout netmsg */

        LIST_ENTRY(carp_softc)   sc_next;       /* Interface clue */
};

#define sc_if   arpcom.ac_if

struct carp_softc_container {
        TAILQ_ENTRY(carp_softc_container) scc_link;
        struct carp_softc       *scc_softc;
};
TAILQ_HEAD(carp_if, carp_softc_container);

SYSCTL_DECL(_net_inet_carp);

static int carp_opts[CARPCTL_MAXID] = { 0, 1, 0, 1, 0, 0, 1 }; /* XXX for now */
SYSCTL_INT(_net_inet_carp, CARPCTL_ALLOW, allow, CTLFLAG_RW,
    &carp_opts[CARPCTL_ALLOW], 0, "Accept incoming CARP packets");
SYSCTL_INT(_net_inet_carp, CARPCTL_PREEMPT, preempt, CTLFLAG_RW,
    &carp_opts[CARPCTL_PREEMPT], 0, "high-priority backup preemption mode");
SYSCTL_INT(_net_inet_carp, CARPCTL_LOG, log, CTLFLAG_RW,
    &carp_opts[CARPCTL_LOG], 0, "log bad carp packets");
SYSCTL_INT(_net_inet_carp, CARPCTL_ARPBALANCE, arpbalance, CTLFLAG_RW,
    &carp_opts[CARPCTL_ARPBALANCE], 0, "balance arp responses");
SYSCTL_INT(_net_inet_carp, CARPCTL_SETROUTE, setroute, CTLFLAG_RW,
    &carp_opts[CARPCTL_SETROUTE], 0, "set route");

static int carp_suppress_preempt = 0;
SYSCTL_INT(_net_inet_carp, OID_AUTO, suppress_preempt, CTLFLAG_RD,
    &carp_suppress_preempt, 0, "Preemption is suppressed");

static int carp_prio_ad = 1;
SYSCTL_INT(_net_inet_carp, OID_AUTO, prio_ad, CTLFLAG_RD,
    &carp_prio_ad, 0, "Prioritize advertisement packet");

static struct carpstats carpstats;
SYSCTL_STRUCT(_net_inet_carp, CARPCTL_STATS, stats, CTLFLAG_RW,
    &carpstats, carpstats,
    "CARP statistics (struct carpstats, netinet/ip_carp.h)");

#define CARP_LOG(...)   do {                            \
        if (carp_opts[CARPCTL_LOG] > 0)                 \
                log(LOG_INFO, __VA_ARGS__);             \
} while (0)

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

static struct lwkt_token carp_listtok = LWKT_TOKEN_INITIALIZER(carp_list_token);

static void     carp_hmac_prepare(struct carp_softc *);
static void     carp_hmac_generate(struct carp_softc *, uint32_t [2],
                    unsigned char [20]);
static int      carp_hmac_verify(struct carp_softc *, uint32_t [2],
                    unsigned char [20]);
static void     carp_setroute(struct carp_softc *, int);
static void     carp_proto_input_c(struct carp_softc *, struct mbuf *,
                    struct carp_header *, sa_family_t);
static int      carp_clone_create(struct if_clone *, int, caddr_t, caddr_t);
static int      carp_clone_destroy(struct ifnet *);
static void     carp_detach(struct carp_softc *, boolean_t, boolean_t);
static void     carp_prepare_ad(struct carp_softc *, struct carp_header *);
static void     carp_send_ad_all(void);
static void     carp_send_ad_timeout(void *);
static void     carp_send_ad(struct carp_softc *);
static void     carp_send_arp(struct carp_softc *);
static void     carp_master_down_timeout(void *);
static void     carp_master_down(struct carp_softc *);
static void     carp_setrun(struct carp_softc *, sa_family_t);
static void     carp_set_state(struct carp_softc *, int);
static struct ifnet *carp_forus(struct carp_if *, const uint8_t *);

static void     carp_init(void *);
static int      carp_ioctl(struct ifnet *, u_long, caddr_t, struct ucred *);
static int      carp_output(struct ifnet *, struct mbuf *, struct sockaddr *,
                    struct rtentry *);
static void     carp_start(struct ifnet *, struct ifaltq_subque *);

static void     carp_multicast_cleanup(struct carp_softc *);
static void     carp_add_addr(struct carp_softc *, struct ifaddr *);
static void     carp_del_addr(struct carp_softc *, struct ifaddr *);
static void     carp_config_addr(struct carp_softc *, struct ifaddr *);
static void     carp_link_addrs(struct carp_softc *, struct ifnet *,
                    struct ifaddr *);
static void     carp_unlink_addrs(struct carp_softc *, struct ifnet *,
                    struct ifaddr *);
static void     carp_update_addrs(struct carp_softc *, struct ifaddr *);

static int      carp_config_vhaddr(struct carp_softc *, struct carp_vhaddr *,
                    struct in_ifaddr *);
static int      carp_activate_vhaddr(struct carp_softc *, struct carp_vhaddr *,
                    struct ifnet *, struct in_ifaddr *, int);
static void     carp_deactivate_vhaddr(struct carp_softc *,
                    struct carp_vhaddr *, boolean_t);
static int      carp_addroute_vhaddr(struct carp_softc *, struct carp_vhaddr *);
static void     carp_delroute_vhaddr(struct carp_softc *, struct carp_vhaddr *,
                    boolean_t);

#ifdef foo
static void     carp_sc_state(struct carp_softc *);
#endif
#ifdef INET6
static void     carp_send_na(struct carp_softc *);
#ifdef notyet
static int      carp_set_addr6(struct carp_softc *, struct sockaddr_in6 *);
static int      carp_del_addr6(struct carp_softc *, struct sockaddr_in6 *);
#endif
static void     carp_multicast6_cleanup(struct carp_softc *);
#endif
static void     carp_stop(struct carp_softc *, boolean_t);
static void     carp_suspend(struct carp_softc *, boolean_t);
static void     carp_ioctl_stop(struct carp_softc *);
static int      carp_ioctl_setvh(struct carp_softc *, void *, struct ucred *);
static void     carp_ioctl_ifcap(struct carp_softc *, int);
static int      carp_ioctl_getvh(struct carp_softc *, void *, struct ucred *);
static int      carp_ioctl_getdevname(struct carp_softc *, struct ifdrv *);
static int      carp_ioctl_getvhaddr(struct carp_softc *, struct ifdrv *);

static struct carp_if *carp_if_remove(struct carp_if *, struct carp_softc *);
static struct carp_if *carp_if_insert(struct carp_if *, struct carp_softc *);
static void     carp_if_free(struct carp_if *);

static void     carp_ifaddr(void *, struct ifnet *, enum ifaddr_event,
                            struct ifaddr *);
static void     carp_ifdetach(void *, struct ifnet *);

static void     carp_ifdetach_dispatch(netmsg_t);
static void     carp_clone_destroy_dispatch(netmsg_t);
static void     carp_init_dispatch(netmsg_t);
static void     carp_ioctl_stop_dispatch(netmsg_t);
static void     carp_ioctl_setvh_dispatch(netmsg_t);
static void     carp_ioctl_ifcap_dispatch(netmsg_t);
static void     carp_ioctl_getvh_dispatch(netmsg_t);
static void     carp_ioctl_getdevname_dispatch(netmsg_t);
static void     carp_ioctl_getvhaddr_dispatch(netmsg_t);
static void     carp_send_ad_timeout_dispatch(netmsg_t);
static void     carp_master_down_timeout_dispatch(netmsg_t);

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

static LIST_HEAD(, carp_softc) carpif_list;

static struct if_clone carp_cloner =
IF_CLONE_INITIALIZER(CARP_IFNAME, carp_clone_create, carp_clone_destroy,
                     0, IF_MAXUNIT);

static const uint8_t    carp_etheraddr[ETHER_ADDR_LEN] =
        { 0, 0, 0x5e, 0, 1, 0 };

static eventhandler_tag carp_ifdetach_event;
static eventhandler_tag carp_ifaddr_event;

static __inline void
carp_insert_vhaddr(struct carp_softc *sc, struct carp_vhaddr *vha_new)
{
        struct carp_vhaddr *vha;
        u_long new_addr, addr;

        KKASSERT((vha_new->vha_flags & CARP_VHAF_ONLIST) == 0);

        /*
         * Virtual address list is sorted; smaller one first
         */
        new_addr = ntohl(vha_new->vha_ia->ia_addr.sin_addr.s_addr);

        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                addr = ntohl(vha->vha_ia->ia_addr.sin_addr.s_addr);

                if (addr > new_addr)
                        break;
        }
        if (vha == NULL)
                TAILQ_INSERT_TAIL(&sc->sc_vha_list, vha_new, vha_link);
        else
                TAILQ_INSERT_BEFORE(vha, vha_new, vha_link);
        vha_new->vha_flags |= CARP_VHAF_ONLIST;
}

static __inline void
carp_remove_vhaddr(struct carp_softc *sc, struct carp_vhaddr *vha)
{
        KKASSERT(vha->vha_flags & CARP_VHAF_ONLIST);
        vha->vha_flags &= ~CARP_VHAF_ONLIST;
        TAILQ_REMOVE(&sc->sc_vha_list, vha, vha_link);
}

static void
carp_hmac_prepare(struct carp_softc *sc)
{
        uint8_t version = CARP_VERSION, type = CARP_ADVERTISEMENT;
        uint8_t vhid = sc->sc_vhid & 0xff;
        int i;
#ifdef INET6
        struct ifaddr_container *ifac;
        struct in6_addr in6;
#endif
#ifdef INET
        struct carp_vhaddr *vha;
#endif

        /* XXX: possible race here */

        /* 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
        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                SHA1Update(&sc->sc_sha1,
                    (const uint8_t *)&vha->vha_ia->ia_addr.sin_addr,
                    sizeof(struct in_addr));
        }
#endif /* INET */
#ifdef INET6
        TAILQ_FOREACH(ifac, &sc->sc_if.if_addrheads[mycpuid], ifa_link) {
                struct ifaddr *ifa = ifac->ifa;

                if (ifa->ifa_addr->sa_family == AF_INET6) {
                        in6 = ifatoia6(ifa)->ia_addr.sin6_addr;
                        in6_clearscope(&in6);
                        SHA1Update(&sc->sc_sha1, (void *)&in6, sizeof(in6));
                }
        }
#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;

        /* 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_hmac_generate(sc, counter, md2);
        return (bcmp(md, md2, sizeof(md2)));
}

static void
carp_setroute(struct carp_softc *sc, int cmd)
{
#ifdef INET6
        struct ifaddr_container *ifac;
#endif
        struct carp_vhaddr *vha;

        KKASSERT(cmd == RTM_DELETE || cmd == RTM_ADD);

        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                if (vha->vha_iaback == NULL)
                        continue;
                if (cmd == RTM_DELETE)
                        carp_delroute_vhaddr(sc, vha, FALSE);
                else
                        carp_addroute_vhaddr(sc, vha);
        }

#ifdef INET6
        TAILQ_FOREACH(ifac, &sc->sc_if.if_addrheads[mycpuid], ifa_link) {
                struct ifaddr *ifa = ifac->ifa;

                if (ifa->ifa_addr->sa_family == AF_INET6) {
                        if (cmd == RTM_ADD)
                                in6_ifaddloop(ifa);
                        else
                                in6_ifremloop(ifa);
                }
        }
#endif /* INET6 */
}

static int
carp_clone_create(struct if_clone *ifc, int unit,
                  caddr_t params __unused, caddr_t data __unused)
{
        struct carp_softc *sc;
        struct ifnet *ifp;

        sc = kmalloc(sizeof(*sc), M_CARP, M_WAITOK | M_ZERO);
        ifp = &sc->sc_if;

        sc->sc_suppress = 0;
        sc->sc_advbase = CARP_DFLTINTV;
        sc->sc_vhid = -1;       /* required setting */
        sc->sc_advskew = 0;
        sc->sc_init_counter = 1;
        sc->sc_naddrs = 0;
        sc->sc_naddrs6 = 0;

        TAILQ_INIT(&sc->sc_vha_list);

#ifdef INET6
        sc->sc_im6o.im6o_multicast_hlim = CARP_DFLTTL;
#endif

        callout_init_mp(&sc->sc_ad_tmo);
        netmsg_init(&sc->sc_ad_msg.base, NULL, &netisr_adone_rport,
            MSGF_DROPABLE | MSGF_PRIORITY, carp_send_ad_timeout_dispatch);
        sc->sc_ad_msg.nc_softc = sc;

        callout_init_mp(&sc->sc_md_tmo);
        callout_init_mp(&sc->sc_md6_tmo);
        netmsg_init(&sc->sc_md_msg.base, NULL, &netisr_adone_rport,
            MSGF_DROPABLE | MSGF_PRIORITY, carp_master_down_timeout_dispatch);
        sc->sc_md_msg.nc_softc = sc;

        if_initname(ifp, CARP_IFNAME, unit);
        ifp->if_softc = sc;
        ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
        ifp->if_init = carp_init;
        ifp->if_ioctl = carp_ioctl;
        ifp->if_start = carp_start;

        ifp->if_capabilities = IFCAP_TXCSUM | IFCAP_TSO;
        ifp->if_capenable = ifp->if_capabilities;
        /*
         * Leave if_hwassist as it is; if_hwassist will be
         * setup when this carp interface has parent.
         */

        ifq_set_maxlen(&ifp->if_snd, ifqmaxlen);
        ifq_set_ready(&ifp->if_snd);

        ether_ifattach(ifp, carp_etheraddr, NULL);

        ifp->if_type = IFT_CARP;
        ifp->if_output = carp_output;

        lwkt_gettoken(&carp_listtok);
        LIST_INSERT_HEAD(&carpif_list, sc, sc_next);
        lwkt_reltoken(&carp_listtok);

        return (0);
}

static void
carp_clone_destroy_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;

        sc->sc_dead = TRUE;
        carp_detach(sc, TRUE, FALSE);

        callout_cancel(&sc->sc_ad_tmo);
        callout_cancel(&sc->sc_md_tmo);
        callout_cancel(&sc->sc_md6_tmo);

        crit_enter();
        lwkt_dropmsg(&sc->sc_ad_msg.base.lmsg);
        lwkt_dropmsg(&sc->sc_md_msg.base.lmsg);
        crit_exit();

        lwkt_replymsg(&cmsg->base.lmsg, 0);
}

static int
carp_clone_destroy(struct ifnet *ifp)
{
        struct carp_softc *sc = ifp->if_softc;
        struct netmsg_carp cmsg;

        bzero(&cmsg, sizeof(cmsg));
        netmsg_init(&cmsg.base, NULL, &curthread->td_msgport, 0,
            carp_clone_destroy_dispatch);
        cmsg.nc_softc = sc;

        lwkt_domsg(netisr_cpuport(0), &cmsg.base.lmsg, 0);

        lwkt_gettoken(&carp_listtok);
        LIST_REMOVE(sc, sc_next);
        lwkt_reltoken(&carp_listtok);

        bpfdetach(ifp);
        if_detach(ifp);

        KASSERT(sc->sc_naddrs == 0, ("certain inet address is still active"));
        kfree(sc, M_CARP);

        return 0;
}

static struct carp_if *
carp_if_remove(struct carp_if *ocif, struct carp_softc *sc)
{
        struct carp_softc_container *oscc, *scc;
        struct carp_if *cif;
        int count = 0;
#ifdef INVARIANTS
        int found = 0;
#endif

        TAILQ_FOREACH(oscc, ocif, scc_link) {
                ++count;
#ifdef INVARIANTS
                if (oscc->scc_softc == sc)
                        found = 1;
#endif
        }
        KASSERT(found, ("%s carp_softc is not on carp_if", __func__));

        if (count == 1) {
                /* Last one is going to be unlinked */
                return NULL;
        }

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

        TAILQ_FOREACH(oscc, ocif, scc_link) {
                if (oscc->scc_softc == sc)
                        continue;

                scc = kmalloc(sizeof(*scc), M_CARP, M_WAITOK | M_ZERO);
                scc->scc_softc = oscc->scc_softc;
                TAILQ_INSERT_TAIL(cif, scc, scc_link);
        }

        return cif;
}

static struct carp_if *
carp_if_insert(struct carp_if *ocif, struct carp_softc *sc)
{
        struct carp_softc_container *oscc;
        int onlist;

        onlist = 0;
        if (ocif != NULL) {
                TAILQ_FOREACH(oscc, ocif, scc_link) {
                        if (oscc->scc_softc == sc)
                                onlist = 1;
                }
        }

#ifdef INVARIANTS
        if (sc->sc_carpdev != NULL) {
                KASSERT(onlist, ("%s is not on %s carp list",
                    sc->sc_if.if_xname, sc->sc_carpdev->if_xname));
        } else {
                KASSERT(!onlist, ("%s is already on carp list",
                    sc->sc_if.if_xname));
        }
#endif

        if (!onlist) {
                struct carp_if *cif;
                struct carp_softc_container *new_scc, *scc;
                int inserted = 0;

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

                new_scc = kmalloc(sizeof(*new_scc), M_CARP, M_WAITOK | M_ZERO);
                new_scc->scc_softc = sc;

                if (ocif != NULL) {
                        TAILQ_FOREACH(oscc, ocif, scc_link) {
                                if (!inserted &&
                                    oscc->scc_softc->sc_vhid > sc->sc_vhid) {
                                        TAILQ_INSERT_TAIL(cif, new_scc,
                                            scc_link);
                                        inserted = 1;
                                }

                                scc = kmalloc(sizeof(*scc), M_CARP,
                                    M_WAITOK | M_ZERO);
                                scc->scc_softc = oscc->scc_softc;
                                TAILQ_INSERT_TAIL(cif, scc, scc_link);
                        }
                }
                if (!inserted)
                        TAILQ_INSERT_TAIL(cif, new_scc, scc_link);

                return cif;
        } else {
                return ocif;
        }
}

static void
carp_if_free(struct carp_if *cif)
{
        struct carp_softc_container *scc;

        while ((scc = TAILQ_FIRST(cif)) != NULL) {
                TAILQ_REMOVE(cif, scc, scc_link);
                kfree(scc, M_CARP);
        }
        kfree(cif, M_CARP);
}

static void
carp_detach(struct carp_softc *sc, boolean_t detach, boolean_t del_iaback)
{
        carp_suspend(sc, detach);

        carp_multicast_cleanup(sc);
#ifdef INET6
        carp_multicast6_cleanup(sc);
#endif

        if (!sc->sc_dead && detach) {
                struct carp_vhaddr *vha;

                TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link)
                        carp_deactivate_vhaddr(sc, vha, del_iaback);
                KKASSERT(sc->sc_naddrs == 0);
        }

        if (sc->sc_carpdev != NULL) {
                struct ifnet *ifp = sc->sc_carpdev;
                struct carp_if *ocif = ifp->if_carp;

                ifp->if_carp = carp_if_remove(ocif, sc);
                KASSERT(ifp->if_carp != ocif,
                    ("%s carp_if_remove failed", __func__));

                sc->sc_carpdev = NULL;
                sc->sc_ia = NULL;
                sc->arpcom.ac_if.if_hwassist = 0;

                /*
                 * Make sure that all protocol threads see the
                 * sc_carpdev and if_carp changes
                 */
                netmsg_service_sync();

                if (ifp->if_carp == NULL) {
                        /*
                         * No more carp interfaces using
                         * ifp as the backing interface,
                         * move it out of promiscous mode.
                         */
                        ifpromisc(ifp, 0);
                }

                /*
                 * The old carp list could be safely free now,
                 * since no one can access it.
                 */
                carp_if_free(ocif);
        }
}

static void
carp_ifdetach_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct ifnet *ifp = cmsg->nc_carpdev;

        while (ifp->if_carp) {
                struct carp_softc_container *scc;

                scc = TAILQ_FIRST((struct carp_if *)(ifp->if_carp));
                carp_detach(scc->scc_softc, TRUE, TRUE);
        }
        lwkt_replymsg(&cmsg->base.lmsg, 0);
}

/* Detach an interface from the carp. */
static void
carp_ifdetach(void *arg __unused, struct ifnet *ifp)
{
        struct netmsg_carp cmsg;

        ASSERT_IFNET_NOT_SERIALIZED_ALL(ifp);

        bzero(&cmsg, sizeof(cmsg));
        netmsg_init(&cmsg.base, NULL, &curthread->td_msgport, 0,
            carp_ifdetach_dispatch);
        cmsg.nc_carpdev = ifp;

        lwkt_domsg(netisr_cpuport(0), &cmsg.base.lmsg, 0);
}

/*
 * process input packet.
 * we have rearranged checks order compared to the rfc,
 * but it seems more efficient this way or not possible otherwise.
 */
int
carp_proto_input(struct mbuf **mp, int *offp, int proto)
{
        struct mbuf *m = *mp;
        struct ip *ip = mtod(m, struct ip *);
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct carp_header *ch;
        struct carp_softc *sc;
        int len, iphlen;

        iphlen = *offp;
        *mp = NULL;

        carpstats.carps_ipackets++;

        if (!carp_opts[CARPCTL_ALLOW]) {
                m_freem(m);
                goto back;
        }

        /* Check if received on a valid carp interface */
        if (ifp->if_type != IFT_CARP) {
                carpstats.carps_badif++;
                CARP_LOG("carp_proto_input: packet received on non-carp "
                    "interface: %s\n", ifp->if_xname);
                m_freem(m);
                goto back;
        }

        if (!CARP_IS_RUNNING(ifp)) {
                carpstats.carps_badif++;
                CARP_LOG("carp_proto_input: packet received on stopped carp "
                    "interface: %s\n", ifp->if_xname);
                m_freem(m);
                goto back;
        }

        sc = ifp->if_softc;
        if (sc->sc_carpdev == NULL) {
                carpstats.carps_badif++;
                CARP_LOG("carp_proto_input: packet received on defunc carp "
                    "interface: %s\n", ifp->if_xname);
                m_freem(m);
                goto back;
        }

        if (!IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
                carpstats.carps_badif++;
                CARP_LOG("carp_proto_input: non-mcast packet on "
                    "interface: %s\n", ifp->if_xname);
                m_freem(m);
                goto back;
        }

        /* Verify that the IP TTL is CARP_DFLTTL. */
        if (ip->ip_ttl != CARP_DFLTTL) {
                carpstats.carps_badttl++;
                CARP_LOG("carp_proto_input: received ttl %d != %d on %s\n",
                    ip->ip_ttl, CARP_DFLTTL, ifp->if_xname);
                m_freem(m);
                goto back;
        }

        /* Minimal CARP packet size */
        len = iphlen + sizeof(*ch);

        /*
         * Verify that the received packet length is
         * not less than the CARP header
         */
        if (m->m_pkthdr.len < len) {
                carpstats.carps_badlen++;
                CARP_LOG("packet too short %d on %s\n", m->m_pkthdr.len,
                    ifp->if_xname);
                m_freem(m);
                goto back;
        }

        /* Make sure that CARP header is contiguous */
        if (len > m->m_len) {
                m = m_pullup(m, len);
                if (m == NULL) {
                        carpstats.carps_hdrops++;
                        CARP_LOG("carp_proto_input: m_pullup failed\n");
                        goto back;
                }
                ip = mtod(m, struct ip *);
        }
        ch = (struct carp_header *)((uint8_t *)ip + iphlen);

        /* Verify the CARP checksum */
        if (in_cksum_skip(m, len, iphlen)) {
                carpstats.carps_badsum++;
                CARP_LOG("carp_proto_input: checksum failed on %s\n",
                    ifp->if_xname);
                m_freem(m);
                goto back;
        }
        carp_proto_input_c(sc, m, ch, AF_INET);
back:
        return(IPPROTO_DONE);
}

#ifdef INET6
int
carp6_proto_input(struct mbuf **mp, int *offp, int proto)
{
        struct mbuf *m = *mp;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct carp_header *ch;
        struct carp_softc *sc;
        u_int len;

        carpstats.carps_ipackets6++;

        if (!carp_opts[CARPCTL_ALLOW]) {
                m_freem(m);
                goto back;
        }

        /* check if received on a valid carp interface */
        if (ifp->if_type != IFT_CARP) {
                carpstats.carps_badif++;
                CARP_LOG("carp6_proto_input: packet received on non-carp "
                    "interface: %s\n", ifp->if_xname);
                m_freem(m);
                goto back;
        }

        if (!CARP_IS_RUNNING(ifp)) {
                carpstats.carps_badif++;
                CARP_LOG("carp_proto_input: packet received on stopped carp "
                    "interface: %s\n", ifp->if_xname);
                m_freem(m);
                goto back;
        }

        sc = ifp->if_softc;
        if (sc->sc_carpdev == NULL) {
                carpstats.carps_badif++;
                CARP_LOG("carp6_proto_input: packet received on defunc-carp "
                    "interface: %s\n", ifp->if_xname);
                m_freem(m);
                goto back;
        }

        /* verify that the IP TTL is 255 */
        if (ip6->ip6_hlim != CARP_DFLTTL) {
                carpstats.carps_badttl++;
                CARP_LOG("carp6_proto_input: received ttl %d != 255 on %s\n",
                    ip6->ip6_hlim, ifp->if_xname);
                m_freem(m);
                goto back;
        }

        /* verify that we have a complete carp packet */
        len = m->m_len;
        IP6_EXTHDR_GET(ch, struct carp_header *, m, *offp, sizeof(*ch));
        if (ch == NULL) {
                carpstats.carps_badlen++;
                CARP_LOG("carp6_proto_input: packet size %u too small\n", len);
                goto back;
        }

        /* verify the CARP checksum */
        if (in_cksum_range(m, 0, *offp, sizeof(*ch))) {
                carpstats.carps_badsum++;
                CARP_LOG("carp6_proto_input: checksum failed, on %s\n",
                    ifp->if_xname);
                m_freem(m);
                goto back;
        }

        carp_proto_input_c(sc, m, ch, AF_INET6);
back:
        return (IPPROTO_DONE);
}
#endif /* INET6 */

static void
carp_proto_input_c(struct carp_softc *sc, struct mbuf *m,
    struct carp_header *ch, sa_family_t af)
{
        struct ifnet *cifp;
        uint64_t tmp_counter;
        struct timeval sc_tv, ch_tv;

        if (sc->sc_vhid != ch->carp_vhid) {
                /*
                 * CARP uses multicast, however, multicast packets
                 * are tapped to all CARP interfaces on the physical
                 * interface receiving the CARP packets, so we don't
                 * update any stats here.
                 */
                m_freem(m);
                return;
        }
        cifp = &sc->sc_if;

        /* verify the CARP version. */
        if (ch->carp_version != CARP_VERSION) {
                carpstats.carps_badver++;
                CARP_LOG("%s; invalid version %d\n", cifp->if_xname,
                         ch->carp_version);
                m_freem(m);
                return;
        }

        /* verify the hash */
        if (carp_hmac_verify(sc, ch->carp_counter, ch->carp_md)) {
                carpstats.carps_badauth++;
                CARP_LOG("%s: incorrect hash\n", cifp->if_xname);
                m_freem(m);
                return;
        }

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

        /* XXX Replay protection goes here */

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

        sc_tv.tv_sec = sc->sc_advbase;
        if (carp_suppress_preempt && sc->sc_advskew <  240)
                sc_tv.tv_usec = 240 * 1000000 / 256;
        else
                sc_tv.tv_usec = sc->sc_advskew * 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_DEBUG("%s: MASTER -> BACKUP "
                           "(more frequent advertisement received)\n",
                           cifp->if_xname);
                        carp_set_state(sc, BACKUP);
                        carp_setrun(sc, 0);
                        if (carp_opts[CARPCTL_SETROUTE])
                                carp_setroute(sc, RTM_DELETE);
                }
                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 (carp_opts[CARPCTL_PREEMPT] &&
                    timevalcmp(&sc_tv, &ch_tv, <)) {
                        CARP_DEBUG("%s: BACKUP -> MASTER "
                            "(preempting a slower master)\n", cifp->if_xname);
                        carp_master_down(sc);
                        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_DEBUG("%s: BACKUP -> MASTER (master timed out)\n",
                                   cifp->if_xname);
                        carp_master_down(sc);
                        break;
                }

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

struct mbuf *
carp_input(void *v, struct mbuf *m)
{
        struct carp_if *cif = v;
        struct ether_header *eh;
        struct carp_softc_container *scc;
        struct ifnet *ifp;

        eh = mtod(m, struct ether_header *);

        ifp = carp_forus(cif, eh->ether_dhost);
        if (ifp != NULL) {
                ether_reinput_oncpu(ifp, m, REINPUT_RUNBPF);
                return NULL;
        }

        if ((m->m_flags & (M_BCAST | M_MCAST)) == 0)
                return m;

        /*
         * XXX Should really check the list of multicast addresses
         * for each CARP interface _before_ copying.
         */
        TAILQ_FOREACH(scc, cif, scc_link) {
                struct carp_softc *sc = scc->scc_softc;
                struct mbuf *m0;

                if ((sc->sc_if.if_flags & IFF_UP) == 0)
                        continue;

                m0 = m_dup(m, M_NOWAIT);
                if (m0 == NULL)
                        continue;

                ether_reinput_oncpu(&sc->sc_if, m0, REINPUT_RUNBPF);
        }
        return m;
}

static void
carp_prepare_ad(struct carp_softc *sc, struct carp_header *ch)
{
        if (sc->sc_init_counter) {
                /* this could also be seconds since unix epoch */
                sc->sc_counter = karc4random();
                sc->sc_counter = sc->sc_counter << 32;
                sc->sc_counter += karc4random();
        } 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 void
carp_send_ad_all(void)
{
        struct carp_softc *sc;

        LIST_FOREACH(sc, &carpif_list, sc_next) {
                if (sc->sc_carpdev == NULL)
                        continue;

                if (CARP_IS_RUNNING(&sc->sc_if) && sc->sc_state == MASTER)
                        carp_send_ad(sc);
        }
}

static void
carp_send_ad_timeout(void *xsc)
{
        struct carp_softc *sc = xsc;
        struct netmsg_carp *cmsg = &sc->sc_ad_msg;

        KASSERT(mycpuid == 0, ("%s not on cpu0 but on cpu%d",
            __func__, mycpuid));

        crit_enter();
        if (cmsg->base.lmsg.ms_flags & MSGF_DONE)
                lwkt_sendmsg_oncpu(netisr_cpuport(0), &cmsg->base.lmsg);
        crit_exit();
}

static void
carp_send_ad_timeout_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;

        /* Reply ASAP */
        crit_enter();
        lwkt_replymsg(&cmsg->base.lmsg, 0);
        crit_exit();

        carp_send_ad(sc);
}

static void
carp_send_ad(struct carp_softc *sc)
{
        struct ifnet *cifp = &sc->sc_if;
        struct carp_header ch;
        struct timeval tv;
        struct carp_header *ch_ptr;
        struct mbuf *m;
        int len, advbase, advskew;

        if (!CARP_IS_RUNNING(cifp)) {
                /* Bow out */
                advbase = 255;
                advskew = 255;
        } else {
                advbase = sc->sc_advbase;
                if (!carp_suppress_preempt || sc->sc_advskew > 240)
                        advskew = sc->sc_advskew;
                else
                        advskew = 240;
                tv.tv_sec = advbase;
                tv.tv_usec = advskew * 1000000 / 256;
        }

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

#ifdef INET
        if (sc->sc_ia != NULL) {
                struct ip *ip;

                MGETHDR(m, M_NOWAIT, MT_HEADER);
                if (m == NULL) {
                        IFNET_STAT_INC(cifp, oerrors, 1);
                        carpstats.carps_onomem++;
                        /* XXX maybe less ? */
                        if (advbase != 255 || advskew != 255)
                                callout_reset(&sc->sc_ad_tmo, tvtohz_high(&tv),
                                    carp_send_ad_timeout, sc);
                        return;
                }
                len = sizeof(*ip) + sizeof(ch);
                m->m_pkthdr.len = len;
                m->m_pkthdr.rcvif = NULL;
                m->m_len = len;
                MH_ALIGN(m, m->m_len);
                m->m_flags |= M_MCAST;
                if (carp_prio_ad)
                        m->m_flags |= M_PRIO;
                ip = mtod(m, struct ip *);
                ip->ip_v = IPVERSION;
                ip->ip_hl = sizeof(*ip) >> 2;
                ip->ip_tos = IPTOS_LOWDELAY;
                ip->ip_len = htons(len);
                ip->ip_id = ip_newid();
                ip->ip_off = htons(IP_DF);
                ip->ip_ttl = CARP_DFLTTL;
                ip->ip_p = IPPROTO_CARP;
                ip->ip_sum = 0;
                ip->ip_src = sc->sc_ia->ia_addr.sin_addr;
                ip->ip_dst.s_addr = htonl(INADDR_CARP_GROUP);

                ch_ptr = (struct carp_header *)(&ip[1]);
                bcopy(&ch, ch_ptr, sizeof(ch));
                carp_prepare_ad(sc, ch_ptr);
                ch_ptr->carp_cksum = in_cksum_skip(m, len, sizeof(*ip));

                getmicrotime(&cifp->if_lastchange);
                IFNET_STAT_INC(cifp, opackets, 1);
                IFNET_STAT_INC(cifp, obytes, len);
                carpstats.carps_opackets++;

                if (ip_output(m, NULL, NULL, IP_RAWOUTPUT, &sc->sc_imo, NULL)) {
                        IFNET_STAT_INC(cifp, oerrors, 1);
                        if (sc->sc_sendad_errors < INT_MAX)
                                sc->sc_sendad_errors++;
                        if (sc->sc_sendad_errors == CARP_SENDAD_MAX_ERRORS) {
                                carp_suppress_preempt++;
                                if (carp_suppress_preempt == 1) {
                                        carp_send_ad_all();
                                }
                        }
                        sc->sc_sendad_success = 0;
                } else {
                        if (sc->sc_sendad_errors >= CARP_SENDAD_MAX_ERRORS) {
                                if (++sc->sc_sendad_success >=
                                    CARP_SENDAD_MIN_SUCCESS) {
                                        carp_suppress_preempt--;
                                        sc->sc_sendad_errors = 0;
                                }
                        } else {
                                sc->sc_sendad_errors = 0;
                        }
                }
        }
#endif /* INET */
#ifdef INET6
        if (sc->sc_ia6) {
                struct ip6_hdr *ip6;

                MGETHDR(m, M_NOWAIT, MT_HEADER);
                if (m == NULL) {
                        IFNET_STAT_INC(cifp, oerrors, 1);
                        carpstats.carps_onomem++;
                        /* XXX maybe less ? */
                        if (advbase != 255 || advskew != 255)
                                callout_reset(&sc->sc_ad_tmo, tvtohz_high(&tv),
                                    carp_send_ad_timeout, sc);
                        return;
                }
                len = sizeof(*ip6) + sizeof(ch);
                m->m_pkthdr.len = len;
                m->m_pkthdr.rcvif = NULL;
                m->m_len = len;
                MH_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;
                ip6->ip6_hlim = CARP_DFLTTL;
                ip6->ip6_nxt = IPPROTO_CARP;
                bcopy(&sc->sc_ia6->ia_addr.sin6_addr, &ip6->ip6_src,
                    sizeof(struct in6_addr));
                /* set the multicast destination */

                ip6->ip6_dst.s6_addr16[0] = htons(0xff02);
                ip6->ip6_dst.s6_addr8[15] = 0x12;
                if (in6_setscope(&ip6->ip6_dst, sc->sc_carpdev, NULL) != 0) {
                        IFNET_STAT_INC(cifp, oerrors, 1);
                        m_freem(m);
                        CARP_LOG("%s: in6_setscope failed\n", __func__);
                        return;
                }

                ch_ptr = (struct carp_header *)(&ip6[1]);
                bcopy(&ch, ch_ptr, sizeof(ch));
                carp_prepare_ad(sc, ch_ptr);
                ch_ptr->carp_cksum = in_cksum_skip(m, len, sizeof(*ip6));

                getmicrotime(&cifp->if_lastchange);
                IFNET_STAT_INC(cifp, opackets, 1);
                IFNET_STAT_INC(cifp, obytes, len);
                carpstats.carps_opackets6++;

                if (ip6_output(m, NULL, NULL, 0, &sc->sc_im6o, NULL, NULL)) {
                        IFNET_STAT_INC(cifp, oerrors, 1);
                        if (sc->sc_sendad_errors < INT_MAX)
                                sc->sc_sendad_errors++;
                        if (sc->sc_sendad_errors == CARP_SENDAD_MAX_ERRORS) {
                                carp_suppress_preempt++;
                                if (carp_suppress_preempt == 1) {
                                        carp_send_ad_all();
                                }
                        }
                        sc->sc_sendad_success = 0;
                } else {
                        if (sc->sc_sendad_errors >= CARP_SENDAD_MAX_ERRORS) {
                                if (++sc->sc_sendad_success >=
                                    CARP_SENDAD_MIN_SUCCESS) {
                                        carp_suppress_preempt--;
                                        sc->sc_sendad_errors = 0;
                                }
                        } else {
                                sc->sc_sendad_errors = 0;
                        }
                }
        }
#endif /* INET6 */

        if (advbase != 255 || advskew != 255)
                callout_reset(&sc->sc_ad_tmo, tvtohz_high(&tv),
                    carp_send_ad_timeout, sc);
}

/*
 * 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)
{
        const struct carp_vhaddr *vha;

        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                if (vha->vha_iaback == NULL)
                        continue;
                arp_gratuitous(&sc->sc_if, &vha->vha_ia->ia_ifa);
        }
}

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

        TAILQ_FOREACH(ifac, &sc->sc_if.if_addrheads[mycpuid], ifa_link) {
                struct ifaddr *ifa = ifac->ifa;

                if (ifa->ifa_addr->sa_family != AF_INET6)
                        continue;

                in6 = &ifatoia6(ifa)->ia_addr.sin6_addr;
                nd6_na_output(sc->sc_carpdev, &mcast, in6,
                    ND_NA_FLAG_OVERRIDE, 1, NULL);
                DELAY(1000);    /* XXX */
        }
}
#endif /* INET6 */

#ifdef notyet
static __inline const struct carp_vhaddr *
carp_find_addr(const struct carp_softc *sc, const struct in_addr *addr)
{
        struct carp_vhaddr *vha;

        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                if (vha->vha_iaback == NULL)
                        continue;

                if (vha->vha_ia->ia_addr.sin_addr.s_addr == addr->s_addr)
                        return vha;
        }
        return NULL;
}

static int
carp_iamatch_balance(const struct carp_if *cif, const struct in_addr *itaddr,
                     const struct in_addr *isaddr, uint8_t **enaddr)
{
        const struct carp_softc *vh;
        int index, count = 0;

        /*
         * XXX proof of concept implementation.
         * We use the source ip to decide which virtual host should
         * handle the request. If we're master of that virtual host,
         * then we respond, otherwise, just drop the arp packet on
         * the floor.
         */

        TAILQ_FOREACH(vh, &cif->vhif_vrs, sc_list) {
                if (!CARP_IS_RUNNING(&vh->sc_if))
                        continue;

                if (carp_find_addr(vh, itaddr) != NULL)
                        count++;
        }
        if (count == 0)
                return 0;

        /* this should be a hash, like pf_hash() */
        index = ntohl(isaddr->s_addr) % count;
        count = 0;

        TAILQ_FOREACH(vh, &cif->vhif_vrs, sc_list) {
                if (!CARP_IS_RUNNING(&vh->sc_if))
                        continue;

                if (carp_find_addr(vh, itaddr) == NULL)
                        continue;

                if (count == index) {
                        if (vh->sc_state == MASTER) {
                                *enaddr = IF_LLADDR(&vh->sc_if);
                                return 1;
                        } else {
                                return 0;
                        }
                }
                count++;
        }
        return 0;
}
#endif

int
carp_iamatch(const struct in_ifaddr *ia)
{
        const struct carp_softc *sc = ia->ia_ifp->if_softc;

        ASSERT_NETISR0;

#ifdef notyet
        if (carp_opts[CARPCTL_ARPBALANCE])
                return carp_iamatch_balance(cif, itaddr, isaddr, enaddr);
#endif

        if (!CARP_IS_RUNNING(&sc->sc_if) || sc->sc_state != MASTER)
                return 0;

        return 1;
}

#ifdef INET6
struct ifaddr *
carp_iamatch6(void *v, struct in6_addr *taddr)
{
#ifdef foo
        struct carp_if *cif = v;
        struct carp_softc *vh;

        TAILQ_FOREACH(vh, &cif->vhif_vrs, sc_list) {
                struct ifaddr_container *ifac;

                TAILQ_FOREACH(ifac, &vh->sc_if.if_addrheads[mycpuid],
                              ifa_link) {
                        struct ifaddr *ifa = ifac->ifa;

                        if (IN6_ARE_ADDR_EQUAL(taddr,
                            &ifatoia6(ifa)->ia_addr.sin6_addr) &&
                            CARP_IS_RUNNING(&vh->sc_if) &&
                            vh->sc_state == MASTER) {
                                return (ifa);
                        }
                }
        }
#endif
        return (NULL);
}

void *
carp_macmatch6(void *v, struct mbuf *m, const struct in6_addr *taddr)
{
#ifdef foo
        struct m_tag *mtag;
        struct carp_if *cif = v;
        struct carp_softc *sc;

        TAILQ_FOREACH(sc, &cif->vhif_vrs, sc_list) {
                struct ifaddr_container *ifac;

                TAILQ_FOREACH(ifac, &sc->sc_if.if_addrheads[mycpuid],
                              ifa_link) {
                        struct ifaddr *ifa = ifac->ifa;

                        if (IN6_ARE_ADDR_EQUAL(taddr,
                            &ifatoia6(ifa)->ia_addr.sin6_addr) &&
                            CARP_IS_RUNNING(&sc->sc_if)) {
                                struct ifnet *ifp = &sc->sc_if;

                                mtag = m_tag_get(PACKET_TAG_CARP,
                                    sizeof(struct ifnet *), M_NOWAIT);
                                if (mtag == NULL) {
                                        /* better a bit than nothing */
                                        return (IF_LLADDR(ifp));
                                }
                                bcopy(&ifp, (caddr_t)(mtag + 1),
                                    sizeof(struct ifnet *));
                                m_tag_prepend(m, mtag);

                                return (IF_LLADDR(ifp));
                        }
                }
        }
#endif
        return (NULL);
}
#endif

static struct ifnet *
carp_forus(struct carp_if *cif, const uint8_t *dhost)
{
        struct carp_softc_container *scc;

        if (memcmp(dhost, carp_etheraddr, ETHER_ADDR_LEN - 1) != 0)
                return NULL;

        TAILQ_FOREACH(scc, cif, scc_link) {
                struct carp_softc *sc = scc->scc_softc;
                struct ifnet *ifp = &sc->sc_if;

                if (CARP_IS_RUNNING(ifp) && sc->sc_state == MASTER &&
                    !bcmp(dhost, IF_LLADDR(ifp), ETHER_ADDR_LEN))
                        return ifp;
        }
        return NULL;
}

static void
carp_master_down_timeout(void *xsc)
{
        struct carp_softc *sc = xsc;
        struct netmsg_carp *cmsg = &sc->sc_md_msg;

        KASSERT(mycpuid == 0, ("%s not on cpu0 but on cpu%d",
            __func__, mycpuid));

        crit_enter();
        if (cmsg->base.lmsg.ms_flags & MSGF_DONE)
                lwkt_sendmsg_oncpu(netisr_cpuport(0), &cmsg->base.lmsg);
        crit_exit();
}

static void
carp_master_down_timeout_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;

        /* Reply ASAP */
        crit_enter();
        lwkt_replymsg(&cmsg->base.lmsg, 0);
        crit_exit();

        CARP_DEBUG("%s: BACKUP -> MASTER (master timed out)\n",
                   sc->sc_if.if_xname);
        carp_master_down(sc);
}

static void
carp_master_down(struct carp_softc *sc)
{
        switch (sc->sc_state) {
        case INIT:
                kprintf("%s: master_down event in INIT state\n",
                        sc->sc_if.if_xname);
                break;

        case MASTER:
                break;

        case BACKUP:
                carp_set_state(sc, MASTER);
                carp_send_ad(sc);
                carp_send_arp(sc);
#ifdef INET6
                carp_send_na(sc);
#endif /* INET6 */
                carp_setrun(sc, 0);
                if (carp_opts[CARPCTL_SETROUTE])
                        carp_setroute(sc, RTM_ADD);
                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 ifnet *cifp = &sc->sc_if;
        struct timeval tv;

        if (sc->sc_carpdev == NULL) {
                carp_set_state(sc, INIT);
                return;
        }

        if ((cifp->if_flags & IFF_RUNNING) && sc->sc_vhid > 0 &&
            (sc->sc_naddrs || sc->sc_naddrs6)) {
                /* Nothing */
        } else {
                if (carp_opts[CARPCTL_SETROUTE])
                        carp_setroute(sc, RTM_DELETE);
                return;
        }

        switch (sc->sc_state) {
        case INIT:
                if (carp_opts[CARPCTL_PREEMPT] && !carp_suppress_preempt) {
                        carp_send_ad(sc);
                        carp_send_arp(sc);
#ifdef INET6
                        carp_send_na(sc);
#endif /* INET6 */
                        CARP_DEBUG("%s: INIT -> MASTER (preempting)\n",
                                   cifp->if_xname);
                        carp_set_state(sc, MASTER);
                        if (carp_opts[CARPCTL_SETROUTE])
                                carp_setroute(sc, RTM_ADD);
                } else {
                        CARP_DEBUG("%s: INIT -> BACKUP\n", cifp->if_xname);
                        carp_set_state(sc, BACKUP);
                        if (carp_opts[CARPCTL_SETROUTE])
                                carp_setroute(sc, RTM_DELETE);
                        carp_setrun(sc, 0);
                }
                break;

        case BACKUP:
                callout_stop(&sc->sc_ad_tmo);
                tv.tv_sec = 3 * sc->sc_advbase;
                tv.tv_usec = sc->sc_advskew * 1000000 / 256;
                switch (af) {
#ifdef INET
                case AF_INET:
                        callout_reset(&sc->sc_md_tmo, tvtohz_high(&tv),
                            carp_master_down_timeout, sc);
                        break;
#endif /* INET */
#ifdef INET6
                case AF_INET6:
                        callout_reset(&sc->sc_md6_tmo, tvtohz_high(&tv),
                            carp_master_down_timeout, sc);
                        break;
#endif /* INET6 */
                default:
                        if (sc->sc_naddrs)
                                callout_reset(&sc->sc_md_tmo, tvtohz_high(&tv),
                                    carp_master_down_timeout, sc);
                        if (sc->sc_naddrs6)
                                callout_reset(&sc->sc_md6_tmo, tvtohz_high(&tv),
                                    carp_master_down_timeout, sc);
                        break;
                }
                break;

        case MASTER:
                tv.tv_sec = sc->sc_advbase;
                tv.tv_usec = sc->sc_advskew * 1000000 / 256;
                callout_reset(&sc->sc_ad_tmo, tvtohz_high(&tv),
                    carp_send_ad_timeout, sc);
                break;
        }
}

static void
carp_multicast_cleanup(struct carp_softc *sc)
{
        struct ip_moptions *imo = &sc->sc_imo;

        if (imo->imo_num_memberships == 0)
                return;
        KKASSERT(imo->imo_num_memberships == 1);

        in_delmulti(imo->imo_membership[0]);
        imo->imo_membership[0] = NULL;
        imo->imo_num_memberships = 0;
        imo->imo_multicast_ifp = NULL;
}

#ifdef INET6
static void
carp_multicast6_cleanup(struct carp_softc *sc)
{
        struct ip6_moptions *im6o = &sc->sc_im6o;

        while (!LIST_EMPTY(&im6o->im6o_memberships)) {
                struct in6_multi_mship *imm =
                    LIST_FIRST(&im6o->im6o_memberships);

                LIST_REMOVE(imm, i6mm_chain);
                in6_leavegroup(imm);
        }
        im6o->im6o_multicast_ifp = NULL;
}
#endif

static void
carp_ioctl_getvhaddr_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;
        const struct carp_vhaddr *vha;
        struct ifcarpvhaddr *carpa, *carpa0;
        int count, len, error = 0;

        count = 0;
        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link)
                ++count;

        if (cmsg->nc_datalen == 0) {
                cmsg->nc_datalen = count * sizeof(*carpa);
                goto back;
        } else if (count == 0 || cmsg->nc_datalen < sizeof(*carpa)) {
                cmsg->nc_datalen = 0;
                goto back;
        }
        len = min(cmsg->nc_datalen, sizeof(*carpa) * count);
        KKASSERT(len >= sizeof(*carpa));

        carpa0 = carpa = kmalloc(len, M_TEMP, M_WAITOK | M_NULLOK | M_ZERO);
        if (carpa == NULL) {
                error = ENOMEM; 
                goto back;
        }

        count = 0;
        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                if (len < sizeof(*carpa))
                        break;

                carpa->carpa_flags = vha->vha_flags;
                carpa->carpa_addr.sin_family = AF_INET;
                carpa->carpa_addr.sin_addr = vha->vha_ia->ia_addr.sin_addr;

                carpa->carpa_baddr.sin_family = AF_INET;
                if (vha->vha_iaback == NULL) {
                        carpa->carpa_baddr.sin_addr.s_addr = INADDR_ANY;
                } else {
                        carpa->carpa_baddr.sin_addr =
                        vha->vha_iaback->ia_addr.sin_addr;
                }

                ++carpa;
                ++count;
                len -= sizeof(*carpa);
        }
        cmsg->nc_datalen = sizeof(*carpa) * count;
        KKASSERT(cmsg->nc_datalen > 0);

        cmsg->nc_data = carpa0;

back:
        lwkt_replymsg(&cmsg->base.lmsg, error);
}

static int
carp_ioctl_getvhaddr(struct carp_softc *sc, struct ifdrv *ifd)
{
        struct ifnet *ifp = &sc->arpcom.ac_if;
        struct netmsg_carp cmsg;
        int error;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);
        ifnet_deserialize_all(ifp);

        bzero(&cmsg, sizeof(cmsg));
        netmsg_init(&cmsg.base, NULL, &curthread->td_msgport, 0,
            carp_ioctl_getvhaddr_dispatch);
        cmsg.nc_softc = sc;
        cmsg.nc_datalen = ifd->ifd_len;

        error = lwkt_domsg(netisr_cpuport(0), &cmsg.base.lmsg, 0);

        if (!error) {
                if (cmsg.nc_data != NULL) {
                        error = copyout(cmsg.nc_data, ifd->ifd_data,
                            cmsg.nc_datalen);
                        kfree(cmsg.nc_data, M_TEMP);
                }
                ifd->ifd_len = cmsg.nc_datalen;
        } else {
                KASSERT(cmsg.nc_data == NULL,
                    ("%s temp vhaddr is alloc upon error", __func__));
        }

        ifnet_serialize_all(ifp);
        return error;
}

static int
carp_config_vhaddr(struct carp_softc *sc, struct carp_vhaddr *vha,
    struct in_ifaddr *ia_del)
{
        struct ifnet *ifp;
        struct in_ifaddr *ia_if;
        const struct in_ifaddr *ia_vha;
        struct in_ifaddr_container *iac;
        int own, ia_match_carpdev;

        KKASSERT(vha->vha_ia != NULL);
        ia_vha = vha->vha_ia;

        ia_if = NULL;
        own = 0;
        ia_match_carpdev = 0;
        TAILQ_FOREACH(iac, &in_ifaddrheads[mycpuid], ia_link) {
                struct in_ifaddr *ia = iac->ia;

                if (ia == ia_del)
                        continue;

                if (ia->ia_ifp->if_type == IFT_CARP)
                        continue;

                if ((ia->ia_ifp->if_flags & IFF_UP) == 0)
                        continue;

                /* and, yeah, we need a multicast-capable iface too */
                if ((ia->ia_ifp->if_flags & IFF_MULTICAST) == 0)
                        continue;

                if (ia_vha->ia_subnetmask == ia->ia_subnetmask &&
                    ia_vha->ia_subnet == ia->ia_subnet) {
                        if (ia_vha->ia_addr.sin_addr.s_addr ==
                            ia->ia_addr.sin_addr.s_addr)
                                own = 1;
                        if (ia_if == NULL) {
                                ia_if = ia;
                        } else if (sc->sc_carpdev != NULL &&
                            sc->sc_carpdev == ia->ia_ifp) {
                                ia_if = ia;
                                if (ia_if->ia_flags & IFA_ROUTE) {
                                        /*
                                         * Address with prefix route
                                         * is prefered
                                         */
                                        break;
                                }
                                ia_match_carpdev = 1;
                        } else if (!ia_match_carpdev) {
                                if (ia->ia_flags & IFA_ROUTE) {
                                        /*
                                         * Address with prefix route
                                         * is prefered over others.
                                         */
                                        ia_if = ia;
                                }
                        }
                }
        }

        carp_deactivate_vhaddr(sc, vha, FALSE);
        if (!ia_if)
                return ENOENT;

        ifp = ia_if->ia_ifp;

        /* XXX Don't allow parent iface to be changed */
        if (sc->sc_carpdev != NULL && sc->sc_carpdev != ifp)
                return EEXIST;

        return carp_activate_vhaddr(sc, vha, ifp, ia_if, own);
}

static void
carp_add_addr(struct carp_softc *sc, struct ifaddr *carp_ifa)
{
        struct carp_vhaddr *vha_new;
        struct in_ifaddr *carp_ia;
#ifdef INVARIANTS
        struct carp_vhaddr *vha;
#endif

        KKASSERT(carp_ifa->ifa_addr->sa_family == AF_INET);
        carp_ia = ifatoia(carp_ifa);

#ifdef INVARIANTS
        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link)
                KKASSERT(vha->vha_ia != NULL && vha->vha_ia != carp_ia);
#endif

        vha_new = kmalloc(sizeof(*vha_new), M_CARP, M_WAITOK | M_ZERO);
        vha_new->vha_ia = carp_ia;
        carp_insert_vhaddr(sc, vha_new);

        if (carp_config_vhaddr(sc, vha_new, NULL) != 0) {
                /*
                 * If the above configuration fails, it may only mean
                 * that the new address is problematic.  However, the
                 * carp(4) interface may already have several working
                 * addresses.  Since the expected behaviour of
                 * SIOC[AS]IFADDR is to put the NIC into working state,
                 * we try starting the state machine manually here with
                 * the hope that the carp(4)'s previously working
                 * addresses still could be brought up.
                 */
                carp_hmac_prepare(sc);
                carp_set_state(sc, INIT);
                carp_setrun(sc, 0);
        }
}

static void
carp_del_addr(struct carp_softc *sc, struct ifaddr *carp_ifa)
{
        struct carp_vhaddr *vha;
        struct in_ifaddr *carp_ia;

        KKASSERT(carp_ifa->ifa_addr->sa_family == AF_INET);
        carp_ia = ifatoia(carp_ifa);

        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                KKASSERT(vha->vha_ia != NULL);
                if (vha->vha_ia == carp_ia)
                        break;
        }
        KASSERT(vha != NULL, ("no corresponding vhaddr %p", carp_ifa));

        /*
         * Remove the vhaddr from the list before deactivating
         * the vhaddr, so that the HMAC could be correctly
         * updated in carp_deactivate_vhaddr()
         */
        carp_remove_vhaddr(sc, vha);

        carp_deactivate_vhaddr(sc, vha, FALSE);
        kfree(vha, M_CARP);
}

static void
carp_config_addr(struct carp_softc *sc, struct ifaddr *carp_ifa)
{
        struct carp_vhaddr *vha;
        struct in_ifaddr *carp_ia;

        KKASSERT(carp_ifa->ifa_addr->sa_family == AF_INET);
        carp_ia = ifatoia(carp_ifa);

        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                KKASSERT(vha->vha_ia != NULL);
                if (vha->vha_ia == carp_ia)
                        break;
        }
        KASSERT(vha != NULL, ("no corresponding vhaddr %p", carp_ifa));

        /* Remove then reinsert, to keep the vhaddr list sorted */
        carp_remove_vhaddr(sc, vha);
        carp_insert_vhaddr(sc, vha);

        if (carp_config_vhaddr(sc, vha, NULL) != 0) {
                /* See the comment in carp_add_addr() */
                carp_hmac_prepare(sc);
                carp_set_state(sc, INIT);
                carp_setrun(sc, 0);
        }
}

#ifdef notyet

#ifdef INET6
static int
carp_set_addr6(struct carp_softc *sc, struct sockaddr_in6 *sin6)
{
        struct ifnet *ifp;
        struct carp_if *cif;
        struct in6_ifaddr *ia, *ia_if;
        struct ip6_moptions *im6o = &sc->sc_im6o;
        struct in6_multi_mship *imm;
        struct in6_addr in6;
        int own, error;

        if (IN6_IS_ADDR_UNSPECIFIED(&sin6->sin6_addr)) {
                carp_setrun(sc, 0);
                return (0);
        }

        /* we have to do it by hands to check we won't match on us */
        ia_if = NULL; own = 0;
        for (ia = in6_ifaddr; ia; ia = ia->ia_next) {
                int i;

                for (i = 0; i < 4; i++) {
                        if ((sin6->sin6_addr.s6_addr32[i] &
                            ia->ia_prefixmask.sin6_addr.s6_addr32[i]) !=
                            (ia->ia_addr.sin6_addr.s6_addr32[i] &
                            ia->ia_prefixmask.sin6_addr.s6_addr32[i]))
                                break;
                }
                /* and, yeah, we need a multicast-capable iface too */
                if (ia->ia_ifp != &sc->sc_if &&
                    (ia->ia_ifp->if_flags & IFF_MULTICAST) &&
                    (i == 4)) {
                        if (!ia_if)
                                ia_if = ia;
                        if (IN6_ARE_ADDR_EQUAL(&sin6->sin6_addr,
                            &ia->ia_addr.sin6_addr))
                                own++;
                }
        }

        if (!ia_if)
                return (EADDRNOTAVAIL);
        ia = ia_if;
        ifp = ia->ia_ifp;

        if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0 ||
            (im6o->im6o_multicast_ifp && im6o->im6o_multicast_ifp != ifp))
                return (EADDRNOTAVAIL);

        if (!sc->sc_naddrs6) {
                im6o->im6o_multicast_ifp = ifp;

                /* join CARP multicast address */
                bzero(&in6, sizeof(in6));
                in6.s6_addr16[0] = htons(0xff02);
                in6.s6_addr8[15] = 0x12;
                if (in6_setscope(&in6, ifp, NULL) != 0)
                        goto cleanup;
                if ((imm = in6_joingroup(ifp, &in6, &error)) == NULL)
                        goto cleanup;
                LIST_INSERT_HEAD(&im6o->im6o_memberships, imm, i6mm_chain);

                /* 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] = sin6->sin6_addr.s6_addr32[3];
                in6.s6_addr8[12] = 0xff;
                if (in6_setscope(&in6, ifp, NULL) != 0)
                        goto cleanup;
                if ((imm = in6_joingroup(ifp, &in6, &error)) == NULL)
                        goto cleanup;
                LIST_INSERT_HEAD(&im6o->im6o_memberships, imm, i6mm_chain);
        }

#ifdef foo
        if (!ifp->if_carp) {
                cif = kmalloc(sizeof(*cif), M_CARP, M_WAITOK | M_ZERO);

                if ((error = ifpromisc(ifp, 1))) {
                        kfree(cif, M_CARP);
                        goto cleanup;
                }

                TAILQ_INIT(&cif->vhif_vrs);
                ifp->if_carp = cif;
        } else {
                struct carp_softc *vr;

                cif = ifp->if_carp;
                TAILQ_FOREACH(vr, &cif->vhif_vrs, sc_list) {
                        if (vr != sc && vr->sc_vhid == sc->sc_vhid) {
                                error = EINVAL;
                                goto cleanup;
                        }
                }
        }
#endif
        sc->sc_ia6 = ia;
        sc->sc_carpdev = ifp;

#ifdef foo
        { /* XXX prevent endless loop if already in queue */
        struct carp_softc *vr, *after = NULL;
        int myself = 0;
        cif = ifp->if_carp;

        TAILQ_FOREACH(vr, &cif->vhif_vrs, sc_list) {
                if (vr == sc)
                        myself = 1;
                if (vr->sc_vhid < sc->sc_vhid)
                        after = vr;
        }

        if (!myself) {
                /* We're trying to keep things in order */
                if (after == NULL)
                        TAILQ_INSERT_TAIL(&cif->vhif_vrs, sc, sc_list);
                else
                        TAILQ_INSERT_AFTER(&cif->vhif_vrs, after, sc, sc_list);
        }
        }
#endif

        sc->sc_naddrs6++;
        if (own)
                sc->sc_advskew = 0;
        carp_sc_state(sc);
        carp_setrun(sc, 0);

        return (0);

cleanup:
        /* clean up multicast memberships */
        if (!sc->sc_naddrs6) {
                while (!LIST_EMPTY(&im6o->im6o_memberships)) {
                        imm = LIST_FIRST(&im6o->im6o_memberships);
                        LIST_REMOVE(imm, i6mm_chain);
                        in6_leavegroup(imm);
                }
        }
        return (error);
}

static int
carp_del_addr6(struct carp_softc *sc, struct sockaddr_in6 *sin6)
{
        int error = 0;

        if (!--sc->sc_naddrs6) {
                struct carp_if *cif = sc->sc_carpdev->if_carp;
                struct ip6_moptions *im6o = &sc->sc_im6o;

                callout_stop(&sc->sc_ad_tmo);
                sc->sc_vhid = -1;
                while (!LIST_EMPTY(&im6o->im6o_memberships)) {
                        struct in6_multi_mship *imm =
                            LIST_FIRST(&im6o->im6o_memberships);

                        LIST_REMOVE(imm, i6mm_chain);
                        in6_leavegroup(imm);
                }
                im6o->im6o_multicast_ifp = NULL;
#ifdef foo
                TAILQ_REMOVE(&cif->vhif_vrs, sc, sc_list);
                if (TAILQ_EMPTY(&cif->vhif_vrs)) {
                        sc->sc_carpdev->if_carp = NULL;
                        kfree(cif, M_IFADDR);
                }
#endif
        }
        return (error);
}
#endif /* INET6 */

#endif

static int
carp_ioctl(struct ifnet *ifp, u_long cmd, caddr_t addr, struct ucred *cr)
{
        struct carp_softc *sc = ifp->if_softc;
        struct ifreq *ifr = (struct ifreq *)addr;
        struct ifdrv *ifd = (struct ifdrv *)addr;
        int error = 0;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);

        switch (cmd) {
        case SIOCSIFFLAGS:
                if (ifp->if_flags & IFF_UP) {
                        if ((ifp->if_flags & IFF_RUNNING) == 0)
                                carp_init(sc);
                } else if (ifp->if_flags & IFF_RUNNING) {
                        carp_ioctl_stop(sc);
                }
                break;

        case SIOCSIFCAP:
                carp_ioctl_ifcap(sc, ifr->ifr_reqcap);
                break;

        case SIOCSVH:
                error = carp_ioctl_setvh(sc, ifr->ifr_data, cr);
                break;

        case SIOCGVH:
                error = carp_ioctl_getvh(sc, ifr->ifr_data, cr);
                break;

        case SIOCGDRVSPEC:
                switch (ifd->ifd_cmd) {
                case CARPGDEVNAME:
                        error = carp_ioctl_getdevname(sc, ifd);
                        break;

                case CARPGVHADDR:
                        error = carp_ioctl_getvhaddr(sc, ifd);
                        break;

                default:
                        error = EINVAL;
                        break;
                }
                break;

        default:
                error = ether_ioctl(ifp, cmd, addr);
                break;
        }

        return error;
}

static void
carp_ioctl_stop_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;

        carp_stop(sc, FALSE);
        lwkt_replymsg(&cmsg->base.lmsg, 0);
}

static void
carp_ioctl_stop(struct carp_softc *sc)
{
        struct ifnet *ifp = &sc->arpcom.ac_if;
        struct netmsg_carp cmsg;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);

        ifnet_deserialize_all(ifp);

        bzero(&cmsg, sizeof(cmsg));
        netmsg_init(&cmsg.base, NULL, &curthread->td_msgport, 0,
            carp_ioctl_stop_dispatch);
        cmsg.nc_softc = sc;

        lwkt_domsg(netisr_cpuport(0), &cmsg.base.lmsg, 0);

        ifnet_serialize_all(ifp);
}

static void
carp_ioctl_setvh_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;
        struct ifnet *ifp = &sc->arpcom.ac_if;
        const struct carpreq *carpr = cmsg->nc_data;
        int error;

        error = 1;
        if ((ifp->if_flags & IFF_RUNNING) &&
            sc->sc_state != INIT && carpr->carpr_state != sc->sc_state) {
                switch (carpr->carpr_state) {
                case BACKUP:
                        callout_stop(&sc->sc_ad_tmo);
                        carp_set_state(sc, BACKUP);
                        carp_setrun(sc, 0);
                        if (carp_opts[CARPCTL_SETROUTE])
                                carp_setroute(sc, RTM_DELETE);
                        break;

                case MASTER:
                        carp_master_down(sc);
                        break;

                default:
                        break;
                }
        }
        if (carpr->carpr_vhid > 0) {
                if (carpr->carpr_vhid > 255) {
                        error = EINVAL;
                        goto back;
                }
                if (sc->sc_carpdev) {
                        struct carp_if *cif = sc->sc_carpdev->if_carp;
                        struct carp_softc_container *scc;

                        TAILQ_FOREACH(scc, cif, scc_link) {
                                struct carp_softc *vr = scc->scc_softc;

                                if (vr != sc &&
                                    vr->sc_vhid == carpr->carpr_vhid) {
                                        error = EEXIST;
                                        goto back;
                                }
                        }
                }
                sc->sc_vhid = carpr->carpr_vhid;

                IF_LLADDR(ifp)[5] = sc->sc_vhid;
                bcopy(IF_LLADDR(ifp), sc->arpcom.ac_enaddr,
                    ETHER_ADDR_LEN);

                error--;
        }
        if (carpr->carpr_advbase > 0 || carpr->carpr_advskew > 0) {
                if (carpr->carpr_advskew >= 255) {
                        error = EINVAL;
                        goto back;
                }
                if (carpr->carpr_advbase > 255) {
                        error = EINVAL;
                        goto back;
                }
                sc->sc_advbase = carpr->carpr_advbase;
                sc->sc_advskew = carpr->carpr_advskew;
                error--;
        }
        bcopy(carpr->carpr_key, sc->sc_key, sizeof(sc->sc_key));
        if (error > 0) {
                error = EINVAL;
        } else {
                error = 0;
                carp_setrun(sc, 0);
        }
back:
        carp_hmac_prepare(sc);

        lwkt_replymsg(&cmsg->base.lmsg, error);
}

static int
carp_ioctl_setvh(struct carp_softc *sc, void *udata, struct ucred *cr)
{
        struct ifnet *ifp = &sc->arpcom.ac_if;
        struct netmsg_carp cmsg;
        struct carpreq carpr;
        int error;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);
        ifnet_deserialize_all(ifp);

        error = caps_priv_check(cr, SYSCAP_RESTRICTEDROOT |
                                    __SYSCAP_NULLCRED);
        if (error)
                goto back;

        error = copyin(udata, &carpr, sizeof(carpr));
        if (error)
                goto back;

        bzero(&cmsg, sizeof(cmsg));
        netmsg_init(&cmsg.base, NULL, &curthread->td_msgport, 0,
            carp_ioctl_setvh_dispatch);
        cmsg.nc_softc = sc;
        cmsg.nc_data = &carpr;

        error = lwkt_domsg(netisr_cpuport(0), &cmsg.base.lmsg, 0);

back:
        ifnet_serialize_all(ifp);
        return error;
}

static void
carp_ioctl_ifcap_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;
        struct ifnet *ifp = &sc->arpcom.ac_if;
        int reqcap = *((const int *)(cmsg->nc_data));
        int mask;

        mask = reqcap ^ ifp->if_capenable;
        if (mask & IFCAP_TXCSUM) {
                ifp->if_capenable ^= IFCAP_TXCSUM;
                if ((ifp->if_capenable & IFCAP_TXCSUM) &&
                    sc->sc_carpdev != NULL) {
                        ifp->if_hwassist |=
                            (sc->sc_carpdev->if_hwassist &
                             (CSUM_IP | CSUM_UDP | CSUM_TCP));
                } else {
                        ifp->if_hwassist &= ~(CSUM_IP | CSUM_UDP | CSUM_TCP);
                }
        }
        if (mask & IFCAP_TSO) {
                ifp->if_capenable ^= IFCAP_TSO;
                if ((ifp->if_capenable & IFCAP_TSO) &&
                    sc->sc_carpdev != NULL) {
                        ifp->if_hwassist |=
                            (sc->sc_carpdev->if_hwassist & CSUM_TSO);
                } else {
                        ifp->if_hwassist &= ~CSUM_TSO;
                }
        }

        lwkt_replymsg(&cmsg->base.lmsg, 0);
}

static void
carp_ioctl_ifcap(struct carp_softc *sc, int reqcap)
{
        struct ifnet *ifp = &sc->arpcom.ac_if;
        struct netmsg_carp cmsg;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);
        ifnet_deserialize_all(ifp);

        bzero(&cmsg, sizeof(cmsg));
        netmsg_init(&cmsg.base, NULL, &curthread->td_msgport, 0,
            carp_ioctl_ifcap_dispatch);
        cmsg.nc_softc = sc;
        cmsg.nc_data = &reqcap;

        lwkt_domsg(netisr_cpuport(0), &cmsg.base.lmsg, 0);

        ifnet_serialize_all(ifp);
}

static void
carp_ioctl_getvh_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;
        struct carpreq *carpr = cmsg->nc_data;

        carpr->carpr_state = sc->sc_state;
        carpr->carpr_vhid = sc->sc_vhid;
        carpr->carpr_advbase = sc->sc_advbase;
        carpr->carpr_advskew = sc->sc_advskew;
        bcopy(sc->sc_key, carpr->carpr_key, sizeof(carpr->carpr_key));

        lwkt_replymsg(&cmsg->base.lmsg, 0);
}

static int
carp_ioctl_getvh(struct carp_softc *sc, void *udata, struct ucred *cr)
{
        struct ifnet *ifp = &sc->arpcom.ac_if;
        struct netmsg_carp cmsg;
        struct carpreq carpr;
        int error;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);
        ifnet_deserialize_all(ifp);

        bzero(&cmsg, sizeof(cmsg));
        netmsg_init(&cmsg.base, NULL, &curthread->td_msgport, 0,
            carp_ioctl_getvh_dispatch);
        cmsg.nc_softc = sc;
        cmsg.nc_data = &carpr;

        lwkt_domsg(netisr_cpuport(0), &cmsg.base.lmsg, 0);

        error = caps_priv_check(cr, SYSCAP_RESTRICTEDROOT |
                                    __SYSCAP_NULLCRED);
        if (error)
                bzero(carpr.carpr_key, sizeof(carpr.carpr_key));

        error = copyout(&carpr, udata, sizeof(carpr));

        ifnet_serialize_all(ifp);
        return error;
}

static void
carp_ioctl_getdevname_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;
        char *devname = cmsg->nc_data;

        bzero(devname, IFNAMSIZ);
        if (sc->sc_carpdev != NULL)
                strlcpy(devname, sc->sc_carpdev->if_xname, IFNAMSIZ);

        lwkt_replymsg(&cmsg->base.lmsg, 0);
}

static int
carp_ioctl_getdevname(struct carp_softc *sc, struct ifdrv *ifd)
{
        struct ifnet *ifp = &sc->arpcom.ac_if;
        struct netmsg_carp cmsg;
        char devname[IFNAMSIZ];
        int error;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);

        if (ifd->ifd_len != sizeof(devname))
                return EINVAL;

        ifnet_deserialize_all(ifp);

        bzero(&cmsg, sizeof(cmsg));
        netmsg_init(&cmsg.base, NULL, &curthread->td_msgport, 0,
            carp_ioctl_getdevname_dispatch);
        cmsg.nc_softc = sc;
        cmsg.nc_data = devname;

        lwkt_domsg(netisr_cpuport(0), &cmsg.base.lmsg, 0);

        error = copyout(devname, ifd->ifd_data, sizeof(devname));

        ifnet_serialize_all(ifp);
        return error;
}

static void
carp_init_dispatch(netmsg_t msg)
{
        struct netmsg_carp *cmsg = (struct netmsg_carp *)msg;
        struct carp_softc *sc = cmsg->nc_softc;

        sc->sc_if.if_flags |= IFF_RUNNING;
        carp_hmac_prepare(sc);
        carp_set_state(sc, INIT);
        carp_setrun(sc, 0);

        lwkt_replymsg(&cmsg->base.lmsg, 0);
}

static void
carp_init(void *xsc)
{
        struct carp_softc *sc = xsc;
        struct ifnet *ifp = &sc->arpcom.ac_if;
        struct netmsg_carp cmsg;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);

        ifnet_deserialize_all(ifp);

        bzero(&cmsg, sizeof(cmsg));
        netmsg_init(&cmsg.base, NULL, &curthread->td_msgport, 0,
            carp_init_dispatch);
        cmsg.nc_softc = sc;

        lwkt_domsg(netisr_cpuport(0), &cmsg.base.lmsg, 0);

        ifnet_serialize_all(ifp);
}

static int
carp_output(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
    struct rtentry *rt)
{
        struct carp_softc *sc = ifp->if_softc;
        struct ifnet *carpdev;
        int error = 0;

        carpdev = sc->sc_carpdev;
        if (carpdev != NULL) {
                if (m->m_flags & M_MCAST)
                        IFNET_STAT_INC(ifp, omcasts, 1);
                IFNET_STAT_INC(ifp, obytes, m->m_pkthdr.len + ETHER_HDR_LEN);
                IFNET_STAT_INC(ifp, opackets, 1);

                /*
                 * NOTE:
                 * CARP's ifp is passed to backing device's
                 * if_output method.
                 */
                carpdev->if_output(ifp, m, dst, rt);
        } else {
                IFNET_STAT_INC(ifp, oerrors, 1);
                m_freem(m);
                error = ENETUNREACH;
        }
        return error;
}

/*
 * Start output on carp interface. This function should never be called.
 */
static void
carp_start(struct ifnet *ifp, struct ifaltq_subque *ifsq __unused)
{
        panic("%s: start called", ifp->if_xname);
}

static void
carp_set_state(struct carp_softc *sc, int state)
{
        struct ifnet *cifp = &sc->sc_if;

        if (sc->sc_state == state)
                return;
        sc->sc_state = state;

        switch (sc->sc_state) {
        case BACKUP:
                cifp->if_link_state = LINK_STATE_DOWN;
                break;

        case MASTER:
                cifp->if_link_state = LINK_STATE_UP;
                break;

        default:
                cifp->if_link_state = LINK_STATE_UNKNOWN;
                break;
        }
        rt_ifmsg(cifp);
}

void
carp_group_demote_adj(struct ifnet *ifp, int adj)
{
        struct ifg_list *ifgl;
        int *dm;

        TAILQ_FOREACH(ifgl, &ifp->if_groups, ifgl_next) {
                if (!strcmp(ifgl->ifgl_group->ifg_group, IFG_ALL))
                        continue;
                dm = &ifgl->ifgl_group->ifg_carp_demoted;

                if (*dm + adj >= 0)
                        *dm += adj;
                else
                        *dm = 0;

                if (adj > 0 && *dm == 1)
                        carp_send_ad_all();
                CARP_LOG("%s demoted group %s to %d", ifp->if_xname,
                    ifgl->ifgl_group->ifg_group, *dm);
        }
}

#ifdef foo
void
carp_carpdev_state(void *v)
{
        struct carp_if *cif = v;
        struct carp_softc *sc;

        TAILQ_FOREACH(sc, &cif->vhif_vrs, sc_list)
                carp_sc_state(sc);
}

static void
carp_sc_state(struct carp_softc *sc)
{
        if (!(sc->sc_carpdev->if_flags & IFF_UP)) {
                callout_stop(&sc->sc_ad_tmo);
                callout_stop(&sc->sc_md_tmo);
                callout_stop(&sc->sc_md6_tmo);
                carp_set_state(sc, INIT);
                carp_setrun(sc, 0);
                if (!sc->sc_suppress) {
                        carp_suppress_preempt++;
                        if (carp_suppress_preempt == 1)
                                carp_send_ad_all();
                }
                sc->sc_suppress = 1;
        } else {
                carp_set_state(sc, INIT);
                carp_setrun(sc, 0);
                if (sc->sc_suppress)
                        carp_suppress_preempt--;
                sc->sc_suppress = 0;
        }
}
#endif

static void
carp_stop(struct carp_softc *sc, boolean_t detach)
{
        sc->sc_if.if_flags &= ~IFF_RUNNING;

        callout_stop(&sc->sc_ad_tmo);
        callout_stop(&sc->sc_md_tmo);
        callout_stop(&sc->sc_md6_tmo);

        if (!detach && sc->sc_state == MASTER)
                carp_send_ad(sc);

        if (sc->sc_suppress)
                carp_suppress_preempt--;
        sc->sc_suppress = 0;

        if (sc->sc_sendad_errors >= CARP_SENDAD_MAX_ERRORS)
                carp_suppress_preempt--;
        sc->sc_sendad_errors = 0;
        sc->sc_sendad_success = 0;

        carp_set_state(sc, INIT);
        carp_setrun(sc, 0);
}

static void
carp_suspend(struct carp_softc *sc, boolean_t detach)
{
        struct ifnet *cifp = &sc->sc_if;

        carp_stop(sc, detach);

        /* Retain the running state, if we are not dead yet */
        if (!sc->sc_dead && (cifp->if_flags & IFF_UP))
                cifp->if_flags |= IFF_RUNNING;
}

static int
carp_activate_vhaddr(struct carp_softc *sc, struct carp_vhaddr *vha,
    struct ifnet *ifp, struct in_ifaddr *ia_if, int own)
{
        struct ip_moptions *imo = &sc->sc_imo;
        struct carp_if *ocif = ifp->if_carp;
        int error;

        KKASSERT(vha->vha_ia != NULL);

        KASSERT(ia_if != NULL, ("NULL backing address"));
        KASSERT(vha->vha_iaback == NULL, ("%p is already activated", vha));
        KASSERT((vha->vha_flags & CARP_VHAF_OWNER) == 0,
                ("inactive vhaddr %p is the address owner", vha));

        KASSERT(sc->sc_carpdev == NULL || sc->sc_carpdev == ifp,
                ("%s is already on %s", sc->sc_if.if_xname,
                 sc->sc_carpdev->if_xname));

        if (ocif == NULL) {
                KASSERT(sc->sc_carpdev == NULL,
                        ("%s is already on %s", sc->sc_if.if_xname,
                         sc->sc_carpdev->if_xname));

                error = ifpromisc(ifp, 1);
                if (error)
                        return error;
        } else {
                struct carp_softc_container *scc;

                TAILQ_FOREACH(scc, ocif, scc_link) {
                        struct carp_softc *vr = scc->scc_softc;

                        if (vr != sc && vr->sc_vhid == sc->sc_vhid)
                                return EINVAL;
                }
        }

        ifp->if_carp = carp_if_insert(ocif, sc);
        KASSERT(ifp->if_carp != NULL, ("%s carp_if_insert failed", __func__));

        sc->sc_ia = ia_if;
        sc->sc_carpdev = ifp;
        sc->arpcom.ac_if.if_hwassist = 0;
        if (sc->arpcom.ac_if.if_capenable & IFCAP_TXCSUM) {
                sc->arpcom.ac_if.if_hwassist |=
                    (ifp->if_hwassist & (CSUM_IP | CSUM_UDP | CSUM_TCP));
        }
        if (sc->arpcom.ac_if.if_capenable & IFCAP_TSO)
                sc->arpcom.ac_if.if_hwassist |= (ifp->if_hwassist & CSUM_TSO);

        /*
         * Make sure that all protocol threads see the sc_carpdev and
         * if_carp changes
         */
        netmsg_service_sync();

        if (ocif != NULL && ifp->if_carp != ocif) {
                /*
                 * The old carp list could be safely free now,
                 * since no one can access it.
                 */
                carp_if_free(ocif);
        }

        vha->vha_iaback = ia_if;
        sc->sc_naddrs++;

        if (own) {
                vha->vha_flags |= CARP_VHAF_OWNER;

                /* XXX save user configured advskew? */
                sc->sc_advskew = 0;
        }

        carp_addroute_vhaddr(sc, vha);

        /*
         * Join the multicast group only after the backing interface
         * has been hooked with the CARP interface.
         */
        KASSERT(imo->imo_multicast_ifp == NULL ||
                imo->imo_multicast_ifp == &sc->sc_if,
                ("%s didn't leave mcast group on %s",
                 sc->sc_if.if_xname, imo->imo_multicast_ifp->if_xname));

        if (imo->imo_num_memberships == 0) {
                struct in_addr addr;

                addr.s_addr = htonl(INADDR_CARP_GROUP);
                imo->imo_membership[0] = in_addmulti(&addr, &sc->sc_if);
                if (imo->imo_membership[0] == NULL) {
                        carp_deactivate_vhaddr(sc, vha, FALSE);
                        return ENOBUFS;
                }

                imo->imo_num_memberships++;
                imo->imo_multicast_ifp = &sc->sc_if;
                imo->imo_multicast_ttl = CARP_DFLTTL;
                imo->imo_multicast_loop = 0;
        }

        carp_hmac_prepare(sc);
        carp_set_state(sc, INIT);
        carp_setrun(sc, 0);
        return 0;
}

static void
carp_deactivate_vhaddr(struct carp_softc *sc, struct carp_vhaddr *vha,
    boolean_t del_iaback)
{
        KKASSERT(vha->vha_ia != NULL);

        carp_hmac_prepare(sc);

        if (vha->vha_iaback == NULL) {
                KASSERT((vha->vha_flags & CARP_VHAF_OWNER) == 0,
                        ("inactive vhaddr %p is the address owner", vha));
                return;
        }

        vha->vha_flags &= ~CARP_VHAF_OWNER;
        carp_delroute_vhaddr(sc, vha, del_iaback);

        KKASSERT(sc->sc_naddrs > 0);
        vha->vha_iaback = NULL;
        sc->sc_naddrs--;
        if (!sc->sc_naddrs) {
                if (sc->sc_naddrs6) {
                        carp_multicast_cleanup(sc);
                        sc->sc_ia = NULL;
                } else {
                        carp_detach(sc, FALSE, del_iaback);
                }
        }
}

static void
carp_link_addrs(struct carp_softc *sc, struct ifnet *ifp, struct ifaddr *ifa_if)
{
        struct carp_vhaddr *vha;
        struct in_ifaddr *ia_if;

        KKASSERT(ifa_if->ifa_addr->sa_family == AF_INET);
        ia_if = ifatoia(ifa_if);

        /*
         * Test each inactive vhaddr against the newly added address.
         * If the newly added address could be the backing address,
         * then activate the matching vhaddr.
         */
        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                const struct in_ifaddr *ia;
                int own;

                if (vha->vha_iaback != NULL)
                        continue;

                ia = vha->vha_ia;
                if (ia->ia_subnetmask != ia_if->ia_subnetmask ||
                    ia->ia_subnet != ia_if->ia_subnet)
                        continue;

                own = 0;
                if (ia->ia_addr.sin_addr.s_addr ==
                    ia_if->ia_addr.sin_addr.s_addr)
                        own = 1;

                carp_activate_vhaddr(sc, vha, ifp, ia_if, own);
        }
}

static void
carp_unlink_addrs(struct carp_softc *sc, struct ifnet *ifp,
                  struct ifaddr *ifa_if)
{
        struct carp_vhaddr *vha;
        struct in_ifaddr *ia_if;

        KKASSERT(ifa_if->ifa_addr->sa_family == AF_INET);
        ia_if = ifatoia(ifa_if);

        /*
         * Ad src address is deleted; set it to NULL.
         * Following loop will try pick up a new ad src address
         * if one of the vhaddr could retain its backing address.
         */
        if (sc->sc_ia == ia_if)
                sc->sc_ia = NULL;

        /*
         * Test each active vhaddr against the deleted address.
         * If the deleted address is vhaddr address's backing
         * address, then deactivate the vhaddr.
         */
        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link) {
                if (vha->vha_iaback == NULL)
                        continue;

                if (vha->vha_iaback == ia_if)
                        carp_deactivate_vhaddr(sc, vha, TRUE);
                else if (sc->sc_ia == NULL)
                        sc->sc_ia = vha->vha_iaback;
        }
}

static void
carp_update_addrs(struct carp_softc *sc, struct ifaddr *ifa_del)
{
        struct carp_vhaddr *vha;

        KKASSERT(sc->sc_carpdev == NULL);

        TAILQ_FOREACH(vha, &sc->sc_vha_list, vha_link)
                carp_config_vhaddr(sc, vha, ifatoia(ifa_del));
}

static void
carp_ifaddr(void *arg __unused, struct ifnet *ifp,
            enum ifaddr_event event, struct ifaddr *ifa)
{
        struct carp_softc *sc;

        if (ifa->ifa_addr->sa_family != AF_INET)
                return;

        ASSERT_NETISR0;

        if (ifp->if_type == IFT_CARP) {
                /*
                 * Address is changed on carp(4) interface
                 */
                switch (event) {
                case IFADDR_EVENT_ADD:
                        carp_add_addr(ifp->if_softc, ifa);
                        break;

                case IFADDR_EVENT_CHANGE:
                        carp_config_addr(ifp->if_softc, ifa);
                        break;

                case IFADDR_EVENT_DELETE:
                        carp_del_addr(ifp->if_softc, ifa);
                        break;
                }
                return;
        }

        /*
         * Address is changed on non-carp(4) interface
         */
        if ((ifp->if_flags & IFF_MULTICAST) == 0)
                return;

        LIST_FOREACH(sc, &carpif_list, sc_next) {
                if (sc->sc_carpdev != NULL && sc->sc_carpdev != ifp) {
                        /* Not the parent iface; skip */
                        continue;
                }

                switch (event) {
                case IFADDR_EVENT_ADD:
                        carp_link_addrs(sc, ifp, ifa);
                        break;

                case IFADDR_EVENT_DELETE:
                        if (sc->sc_carpdev != NULL) {
                                carp_unlink_addrs(sc, ifp, ifa);
                                if (sc->sc_carpdev == NULL) {
                                        /*
                                         * We no longer have the parent
                                         * interface, however, certain
                                         * virtual addresses, which are
                                         * not used because they can't
                                         * match the previous parent
                                         * interface's addresses, may now
                                         * match different interface's
                                         * addresses.
                                         */
                                        carp_update_addrs(sc, ifa);
                                }
                        } else {
                                /*
                                 * The carp(4) interface didn't have a
                                 * parent iface, so it is not possible
                                 * that it will contain any address to
                                 * be unlinked.
                                 */
                        }
                        break;

                case IFADDR_EVENT_CHANGE:
                        if (sc->sc_carpdev == NULL) {
                                /*
                                 * The carp(4) interface didn't have a
                                 * parent iface, so it is not possible
                                 * that it will contain any address to
                                 * be updated.
                                 */
                                carp_link_addrs(sc, ifp, ifa);
                        } else {
                                /*
                                 * First try breaking tie with the old
                                 * address.  Then see whether we could
                                 * link certain vhaddr to the new address.
                                 * If that fails, i.e. carpdev is NULL,
                                 * we try a global update.
                                 *
                                 * NOTE: The above order is critical.
                                 */
                                carp_unlink_addrs(sc, ifp, ifa);
                                carp_link_addrs(sc, ifp, ifa);
                                if (sc->sc_carpdev == NULL) {
                                        /*
                                         * See the comment in the above
                                         * IFADDR_EVENT_DELETE block.
                                         */
                                        carp_update_addrs(sc, NULL);
                                }
                        }
                        break;
                }
        }
}

void
carp_proto_ctlinput(netmsg_t msg)
{
        int cmd = msg->ctlinput.nm_cmd;
        struct sockaddr *sa = msg->ctlinput.nm_arg;
        struct in_ifaddr_container *iac;

        /* We only process PRC_IFDOWN and PRC_IFUP commands */
        if (cmd != PRC_IFDOWN && cmd != PRC_IFUP)
                goto done;

        TAILQ_FOREACH(iac, &in_ifaddrheads[mycpuid], ia_link) {
                struct in_ifaddr *ia = iac->ia;
                struct ifnet *ifp = ia->ia_ifp;

                if (ifp->if_type == IFT_CARP)
                        continue;

                if (ia->ia_ifa.ifa_addr == sa) {
                        if (cmd == PRC_IFDOWN) {
                                carp_ifaddr(NULL, ifp, IFADDR_EVENT_DELETE,
                                    &ia->ia_ifa);
                        } else if (cmd == PRC_IFUP) {
                                carp_ifaddr(NULL, ifp, IFADDR_EVENT_ADD,
                                    &ia->ia_ifa);
                        }
                        break;
                }
        }
done:
        lwkt_replymsg(&msg->lmsg, 0);
}

struct ifnet *
carp_parent(struct ifnet *cifp)
{
        struct carp_softc *sc;

        KKASSERT(cifp->if_type == IFT_CARP);
        sc = cifp->if_softc;

        return sc->sc_carpdev;
}

#define rtinitflags(x) \
        (((x)->ia_ifp->if_flags & (IFF_LOOPBACK | IFF_POINTOPOINT)) \
                 ? RTF_HOST : 0)

static int
carp_addroute_vhaddr(struct carp_softc *sc, struct carp_vhaddr *vha)
{
        struct in_ifaddr *ia, *iaback;

        if (sc->sc_state != MASTER)
                return 0;

        ia = vha->vha_ia;
        KKASSERT(ia != NULL);

        iaback = vha->vha_iaback;
        KKASSERT(iaback != NULL);

        return rtchange(&iaback->ia_ifa, &ia->ia_ifa);
}

static void
carp_delroute_vhaddr(struct carp_softc *sc, struct carp_vhaddr *vha,
    boolean_t del_iaback)
{
        struct in_ifaddr *ia, *iaback;

        ia = vha->vha_ia;
        KKASSERT(ia != NULL);

        iaback = vha->vha_iaback;
        KKASSERT(iaback != NULL);

        if (!del_iaback && (iaback->ia_ifp->if_flags & IFF_UP)) {
                rtchange(&ia->ia_ifa, &iaback->ia_ifa);
                return;
        }

        rtinit(&ia->ia_ifa, RTM_DELETE, rtinitflags(ia));
        in_ifadown_force(&ia->ia_ifa, 1);
        ia->ia_flags &= ~IFA_ROUTE;
}

static int
carp_modevent(module_t mod, int type, void *data)
{
        switch (type) {
        case MOD_LOAD:
                LIST_INIT(&carpif_list);
                carp_ifdetach_event =
                EVENTHANDLER_REGISTER(ifnet_detach_event, carp_ifdetach, NULL,
                                      EVENTHANDLER_PRI_ANY);
                carp_ifaddr_event =
                EVENTHANDLER_REGISTER(ifaddr_event, carp_ifaddr, NULL,
                                      EVENTHANDLER_PRI_FIRST);
                if_clone_attach(&carp_cloner);
                break;

        case MOD_UNLOAD:
                EVENTHANDLER_DEREGISTER(ifnet_detach_event,
                                        carp_ifdetach_event);
                EVENTHANDLER_DEREGISTER(ifaddr_event,
                                        carp_ifaddr_event);
                if_clone_detach(&carp_cloner);
                break;

        default:
                return (EINVAL);
        }
        return (0);
}

static moduledata_t carp_mod = {
        "carp",
        carp_modevent,
        0
};
DECLARE_MODULE(carp, carp_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);