tuning.7: Fix typo.

[dragonfly.git] / sys / netinet / if_ether.c

/*
 * Copyright (c) 2004, 2005 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Jeffrey M. Hsu.
 *
 * 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.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``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
 * COPYRIGHT HOLDERS OR CONTRIBUTORS 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 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.
 */

/*
 * Copyright (c) 1982, 1986, 1988, 1993
 *      The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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 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.
 *
 *      @(#)if_ether.c  8.1 (Berkeley) 6/10/93
 * $FreeBSD: src/sys/netinet/if_ether.c,v 1.64.2.23 2003/04/11 07:23:15 fjoe Exp $
 */

/*
 * Ethernet address resolution protocol.
 * TODO:
 *      add "inuse/lock" bit (or ref. count) along with valid bit
 */

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

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/queue.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/socket.h>
#include <sys/syslog.h>
#include <sys/lock.h>

#include <net/if.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/route.h>
#include <net/netisr.h>
#include <net/if_llc.h>

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/if_ether.h>

#include <sys/thread2.h>
#include <sys/msgport2.h>
#include <net/netmsg2.h>
#include <net/netisr2.h>
#include <sys/mplock2.h>

#ifdef CARP
#include <netinet/ip_carp.h>
#endif

#define SIN(s) ((struct sockaddr_in *)s)
#define SDL(s) ((struct sockaddr_dl *)s)

SYSCTL_DECL(_net_link_ether);
SYSCTL_NODE(_net_link_ether, PF_INET, inet, CTLFLAG_RW, 0, "");

/* timer values */
static int arpt_prune = (5*60*1); /* walk list every 5 minutes */
static int arpt_keep = (20*60); /* once resolved, good for 20 more minutes */
static int arpt_down = 20;      /* once declared down, don't send for 20 sec */

SYSCTL_INT(_net_link_ether_inet, OID_AUTO, prune_intvl, CTLFLAG_RW,
           &arpt_prune, 0, "");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, max_age, CTLFLAG_RW,
           &arpt_keep, 0, "");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, host_down_time, CTLFLAG_RW,
           &arpt_down, 0, "");

#define rt_expire       rt_rmx.rmx_expire

struct llinfo_arp {
        LIST_ENTRY(llinfo_arp) la_le;
        struct  rtentry *la_rt;
        struct  mbuf *la_hold;  /* last packet until resolved/timeout */
        u_short la_preempt;     /* countdown for pre-expiry arps */
        u_short la_asked;       /* #times we QUERIED following expiration */
};

static int      arp_maxtries = 5;
static int      useloopback = 1; /* use loopback interface for local traffic */
static int      arp_proxyall = 0;
static int      arp_refresh = 60; /* refresh arp cache ~60 (not impl yet) */
static int      arp_restricted_match = 0;
static int      arp_ignore_probes = 1;

SYSCTL_INT(_net_link_ether_inet, OID_AUTO, maxtries, CTLFLAG_RW,
           &arp_maxtries, 0, "ARP resolution attempts before returning error");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, useloopback, CTLFLAG_RW,
           &useloopback, 0, "Use the loopback interface for local traffic");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, proxyall, CTLFLAG_RW,
           &arp_proxyall, 0, "Enable proxy ARP for all suitable requests");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, restricted_match, CTLFLAG_RW,
           &arp_restricted_match, 0, "Only match against the sender");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, refresh, CTLFLAG_RW,
           &arp_refresh, 0, "Preemptively refresh the ARP");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, ignore_probes, CTLFLAG_RW,
           &arp_ignore_probes, 0, "Ignore ARP probes");

static void     arp_rtrequest(int, struct rtentry *);
static void     arprequest(struct ifnet *, const struct in_addr *,
                           const struct in_addr *, const u_char *);
static void     arprequest_async(struct ifnet *, const struct in_addr *,
                                 const struct in_addr *, const u_char *);
static void     arpintr(netmsg_t msg);
static void     arptfree(struct llinfo_arp *);
static void     arptimer(void *);
static struct llinfo_arp *
                arplookup(in_addr_t, boolean_t, boolean_t, boolean_t);
#ifdef INET
static void     in_arpinput(struct mbuf *);
static void     in_arpreply(struct mbuf *m, in_addr_t, in_addr_t);
static void     arp_update_msghandler(netmsg_t);
static void     arp_reply_msghandler(netmsg_t);
#endif

struct arp_pcpu_data {
        struct callout          timer_ch;
        struct netmsg_base      timer_nmsg;
        LIST_HEAD(, llinfo_arp) llinfo_list;
} __cachealign;

static struct arp_pcpu_data     arp_data[MAXCPU];

/*
 * Timeout routine.  Age arp_tab entries periodically.
 */
static void
arptimer_dispatch(netmsg_t nmsg)
{
        struct llinfo_arp *la, *nla;
        struct arp_pcpu_data *ad = &arp_data[mycpuid];

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

        LIST_FOREACH_MUTABLE(la, &ad->llinfo_list, la_le, nla) {
                if (la->la_rt->rt_expire && la->la_rt->rt_expire <= time_uptime)
                        arptfree(la);
        }
        callout_reset(&ad->timer_ch, arpt_prune * hz, arptimer, NULL);
}

static void
arptimer(void *arg __unused)
{
        int cpuid = mycpuid;
        struct lwkt_msg *lmsg = &arp_data[cpuid].timer_nmsg.lmsg;

        crit_enter();
        if (lmsg->ms_flags & MSGF_DONE)
                lwkt_sendmsg_oncpu(netisr_cpuport(cpuid), lmsg);
        crit_exit();
}

/*
 * Parallel to llc_rtrequest.
 *
 * Called after a route is successfully added to the tree to fix-up the
 * route and initiate arp operations if required.
 */
static void
arp_rtrequest(int req, struct rtentry *rt)
{
        struct sockaddr *gate = rt->rt_gateway;
        struct llinfo_arp *la = rt->rt_llinfo;

        struct sockaddr_dl null_sdl = { sizeof null_sdl, AF_LINK };

        if (rt->rt_flags & RTF_GATEWAY)
                return;

        switch (req) {
        case RTM_ADD:
                /*
                 * XXX: If this is a manually added route to interface
                 * such as older version of routed or gated might provide,
                 * restore cloning bit.
                 */
                if (!(rt->rt_flags & RTF_HOST) &&
                    SIN(rt_mask(rt))->sin_addr.s_addr != 0xffffffff)
                        rt->rt_flags |= RTF_CLONING;
                if (rt->rt_flags & RTF_CLONING) {
                        /*
                         * Case 1: This route should come from a route to iface.
                         */
                        rt_setgate(rt, rt_key(rt),
                                   (struct sockaddr *)&null_sdl,
                                   RTL_DONTREPORT);
                        gate = rt->rt_gateway;
                        SDL(gate)->sdl_type = rt->rt_ifp->if_type;
                        SDL(gate)->sdl_index = rt->rt_ifp->if_index;
                        rt->rt_expire = time_uptime;
                        break;
                }
                /*
                 * Announce a new entry if requested, and only announce it
                 * once on cpu0.
                 */
                if ((rt->rt_flags & RTF_ANNOUNCE) && mycpuid == 0) {
                        arprequest_async(rt->rt_ifp,
                            &SIN(rt_key(rt))->sin_addr,
                            &SIN(rt_key(rt))->sin_addr,
                            LLADDR(SDL(gate)));
                }
                /*FALLTHROUGH*/
        case RTM_RESOLVE:
                if (gate->sa_family != AF_LINK ||
                    gate->sa_len < sizeof(struct sockaddr_dl)) {
                        log(LOG_DEBUG, "arp_rtrequest: bad gateway value\n");
                        break;
                }
                SDL(gate)->sdl_type = rt->rt_ifp->if_type;
                SDL(gate)->sdl_index = rt->rt_ifp->if_index;
                if (la != NULL)
                        break; /* This happens on a route change */
                /*
                 * Case 2:  This route may come from cloning, or a manual route
                 * add with a LL address.
                 */
                R_Malloc(la, struct llinfo_arp *, sizeof *la);
                rt->rt_llinfo = la;
                if (la == NULL) {
                        log(LOG_DEBUG, "arp_rtrequest: malloc failed\n");
                        break;
                }
                bzero(la, sizeof *la);
                la->la_rt = rt;
                rt->rt_flags |= RTF_LLINFO;
                LIST_INSERT_HEAD(&arp_data[mycpuid].llinfo_list, la, la_le);

#ifdef INET
                /*
                 * This keeps the multicast addresses from showing up
                 * in `arp -a' listings as unresolved.  It's not actually
                 * functional.  Then the same for broadcast.
                 */
                if (IN_MULTICAST(ntohl(SIN(rt_key(rt))->sin_addr.s_addr))) {
                        ETHER_MAP_IP_MULTICAST(&SIN(rt_key(rt))->sin_addr,
                                               LLADDR(SDL(gate)));
                        SDL(gate)->sdl_alen = 6;
                        rt->rt_expire = 0;
                }
                if (in_broadcast(SIN(rt_key(rt))->sin_addr, rt->rt_ifp)) {
                        memcpy(LLADDR(SDL(gate)), rt->rt_ifp->if_broadcastaddr,
                               rt->rt_ifp->if_addrlen);
                        SDL(gate)->sdl_alen = rt->rt_ifp->if_addrlen;
                        rt->rt_expire = 0;
                }
#endif

                /*
                 * This fixes up the routing interface for local addresses.
                 * The route is adjusted to point at lo0 and the expiration
                 * timer is disabled.
                 *
                 * NOTE: This prevents locally targetted traffic from going
                 *       out the hardware interface, which is inefficient
                 *       and might not work if the hardware cannot listen
                 *       to its own transmitted packets.   Setting
                 *       net.link.ether.inet.useloopback to 0 will force
                 *       packets for local addresses out the hardware (and
                 *       it is expected to receive its own packet).
                 *
                 * XXX We should just be able to test RTF_LOCAL here instead
                 *     of having to compare IPs.
                 */
                if (SIN(rt_key(rt))->sin_addr.s_addr ==
                    (IA_SIN(rt->rt_ifa))->sin_addr.s_addr) {
                        rt->rt_expire = 0;
                        bcopy(IF_LLADDR(rt->rt_ifp), LLADDR(SDL(gate)),
                              SDL(gate)->sdl_alen = rt->rt_ifp->if_addrlen);
                        if (useloopback)
                                rt->rt_ifp = loif;
                }
                break;

        case RTM_DELETE:
                if (la == NULL)
                        break;
                LIST_REMOVE(la, la_le);
                rt->rt_llinfo = NULL;
                rt->rt_flags &= ~RTF_LLINFO;
                if (la->la_hold != NULL)
                        m_freem(la->la_hold);
                Free(la);
                break;
        }
}

static struct mbuf *
arpreq_alloc(struct ifnet *ifp, const struct in_addr *sip,
             const struct in_addr *tip, const u_char *enaddr)
{
        struct mbuf *m;
        struct arphdr *ah;
        u_short ar_hrd;

        if ((m = m_gethdr(M_NOWAIT, MT_DATA)) == NULL)
                return NULL;
        m->m_pkthdr.rcvif = NULL;

        switch (ifp->if_type) {
        case IFT_ETHER:
                /*
                 * This may not be correct for types not explicitly
                 * listed, but this is our best guess
                 */
        default:
                ar_hrd = htons(ARPHRD_ETHER);

                m->m_len = arphdr_len2(ifp->if_addrlen, sizeof(struct in_addr));
                m->m_pkthdr.len = m->m_len;
                MH_ALIGN(m, m->m_len);

                ah = mtod(m, struct arphdr *);
                break;
        }

        ah->ar_hrd = ar_hrd;
        ah->ar_pro = htons(ETHERTYPE_IP);
        ah->ar_hln = ifp->if_addrlen;           /* hardware address length */
        ah->ar_pln = sizeof(struct in_addr);    /* protocol address length */
        ah->ar_op = htons(ARPOP_REQUEST);
        memcpy(ar_sha(ah), enaddr, ah->ar_hln);
        memset(ar_tha(ah), 0, ah->ar_hln);
        memcpy(ar_spa(ah), sip, ah->ar_pln);
        memcpy(ar_tpa(ah), tip, ah->ar_pln);

        return m;
}

static void
arpreq_send(struct ifnet *ifp, struct mbuf *m)
{
        struct sockaddr sa;
        struct ether_header *eh;

        switch (ifp->if_type) {
        case IFT_ETHER:
                /*
                 * This may not be correct for types not explicitly
                 * listed, but this is our best guess
                 */
        default:
                eh = (struct ether_header *)sa.sa_data;
                /* if_output() will not swap */
                eh->ether_type = htons(ETHERTYPE_ARP);
                memcpy(eh->ether_dhost, ifp->if_broadcastaddr, ifp->if_addrlen);
                break;
        }

        sa.sa_family = AF_UNSPEC;
        sa.sa_len = sizeof(sa);
        ifp->if_output(ifp, m, &sa, NULL);
}

static void
arpreq_send_handler(netmsg_t msg)
{
        struct mbuf *m = msg->packet.nm_packet;
        struct ifnet *ifp = msg->lmsg.u.ms_resultp;

        arpreq_send(ifp, m);
        /* nmsg was embedded in the mbuf, do not reply! */
}

/*
 * Broadcast an ARP request. Caller specifies:
 *      - arp header source ip address
 *      - arp header target ip address
 *      - arp header source ethernet address
 *
 * NOTE: Caller MUST NOT hold ifp's serializer
 */
static void
arprequest(struct ifnet *ifp, const struct in_addr *sip,
           const struct in_addr *tip, const u_char *enaddr)
{
        struct mbuf *m;

        if (enaddr == NULL) {
                if (ifp->if_bridge) {
                        enaddr = IF_LLADDR(ether_bridge_interface(ifp));
                } else {
                        enaddr = IF_LLADDR(ifp);
                }
        }

        m = arpreq_alloc(ifp, sip, tip, enaddr);
        if (m == NULL)
                return;
        arpreq_send(ifp, m);
}

/*
 * Same as arprequest(), except:
 * - Caller is allowed to hold ifp's serializer
 * - Network output is done in protocol thead
 */
static void
arprequest_async(struct ifnet *ifp, const struct in_addr *sip,
                 const struct in_addr *tip, const u_char *enaddr)
{
        struct mbuf *m;
        struct netmsg_packet *pmsg;

        if (enaddr == NULL) {
                if (ifp->if_bridge) {
                        enaddr = IF_LLADDR(ether_bridge_interface(ifp));
                } else {
                        enaddr = IF_LLADDR(ifp);
                }
        }
        m = arpreq_alloc(ifp, sip, tip, enaddr);
        if (m == NULL)
                return;

        pmsg = &m->m_hdr.mh_netmsg;
        netmsg_init(&pmsg->base, NULL, &netisr_apanic_rport,
                    0, arpreq_send_handler);
        pmsg->nm_packet = m;
        pmsg->base.lmsg.u.ms_resultp = ifp;

        lwkt_sendmsg_oncpu(netisr_cpuport(mycpuid), &pmsg->base.lmsg);
}

/*
 * Resolve an IP address into an ethernet address.  If success,
 * desten is filled in.  If there is no entry in arptab,
 * set one up and broadcast a request for the IP address.
 * Hold onto this mbuf and resend it once the address
 * is finally resolved.  A return value of 1 indicates
 * that desten has been filled in and the packet should be sent
 * normally; a 0 return indicates that the packet has been
 * taken over here, either now or for later transmission.
 */
int
arpresolve(struct ifnet *ifp, struct rtentry *rt0, struct mbuf *m,
           struct sockaddr *dst, u_char *desten)
{
        struct rtentry *rt = NULL;
        struct llinfo_arp *la = NULL;
        struct sockaddr_dl *sdl;

        if (m->m_flags & M_BCAST) {     /* broadcast */
                memcpy(desten, ifp->if_broadcastaddr, ifp->if_addrlen);
                return (1);
        }
        if (m->m_flags & M_MCAST) {/* multicast */
                ETHER_MAP_IP_MULTICAST(&SIN(dst)->sin_addr, desten);
                return (1);
        }
        if (rt0 != NULL) {
                if (rt_llroute(dst, rt0, &rt) != 0) {
                        m_freem(m);
                        return 0;
                }
                la = rt->rt_llinfo;
        }
        if (la == NULL) {
                la = arplookup(SIN(dst)->sin_addr.s_addr,
                               TRUE, RTL_REPORTMSG, FALSE);
                if (la != NULL)
                        rt = la->la_rt;
        }
        if (la == NULL || rt == NULL) {
                char addr[INET_ADDRSTRLEN];

                log(LOG_DEBUG, "arpresolve: can't allocate llinfo for %s%s%s\n",
                    kinet_ntoa(SIN(dst)->sin_addr, addr), la ? "la" : " ",
                    rt ? "rt" : "");
                m_freem(m);
                return (0);
        }
        sdl = SDL(rt->rt_gateway);
        /*
         * Check the address family and length is valid, the address
         * is resolved; otherwise, try to resolve.
         */
        if ((rt->rt_expire == 0 || rt->rt_expire > time_uptime) &&
            sdl->sdl_family == AF_LINK && sdl->sdl_alen != 0) {
                /*
                 * If entry has an expiry time and it is approaching,
                 * see if we need to send an ARP request within this
                 * arpt_down interval.
                 */
                if ((rt->rt_expire != 0) &&
                    (time_uptime + la->la_preempt > rt->rt_expire)) {
                        arprequest(ifp,
                                   &SIN(rt->rt_ifa->ifa_addr)->sin_addr,
                                   &SIN(dst)->sin_addr,
                                   NULL);
                        la->la_preempt--;
                }

                bcopy(LLADDR(sdl), desten, sdl->sdl_alen);
                return 1;
        }
        /*
         * If ARP is disabled or static on this interface, stop.
         * XXX
         * Probably should not allocate empty llinfo struct if we are
         * not going to be sending out an arp request.
         */
        if (ifp->if_flags & (IFF_NOARP | IFF_STATICARP)) {
                m_freem(m);
                return (0);
        }
        /*
         * There is an arptab entry, but no ethernet address
         * response yet.  Replace the held mbuf with this
         * latest one.
         */
        if (la->la_hold != NULL)
                m_freem(la->la_hold);
        la->la_hold = m;
        if (rt->rt_expire || ((rt->rt_flags & RTF_STATIC) && !sdl->sdl_alen)) {
                rt->rt_flags &= ~RTF_REJECT;
                if (la->la_asked == 0 || rt->rt_expire != time_uptime) {
                        rt->rt_expire = time_uptime;
                        if (la->la_asked++ < arp_maxtries) {
                                arprequest(ifp,
                                           &SIN(rt->rt_ifa->ifa_addr)->sin_addr,
                                           &SIN(dst)->sin_addr,
                                           NULL);
                        } else {
                                rt->rt_flags |= RTF_REJECT;
                                rt->rt_expire += arpt_down;
                                la->la_asked = 0;
                                la->la_preempt = arp_maxtries;
                        }
                }
        }
        return (0);
}

/*
 * Common length and type checks are done here,
 * then the protocol-specific routine is called.
 */
static void
arpintr(netmsg_t msg)
{
        struct mbuf *m = msg->packet.nm_packet;
        struct arphdr *ar;
        u_short ar_hrd;
        char hexstr[6];

        if (m->m_len < sizeof(struct arphdr) &&
            (m = m_pullup(m, sizeof(struct arphdr))) == NULL) {
                log(LOG_ERR, "arp: runt packet -- m_pullup failed\n");
                return;
        }
        ar = mtod(m, struct arphdr *);

        ar_hrd = ntohs(ar->ar_hrd);
        if (ar_hrd != ARPHRD_ETHER && ar_hrd != ARPHRD_IEEE802) {
                hexncpy((unsigned char *)&ar->ar_hrd, 2, hexstr, 5, NULL);
                log(LOG_ERR, "arp: unknown hardware address format (0x%s)\n",
                    hexstr);
                m_freem(m);
                return;
        }

        if (m->m_pkthdr.len < arphdr_len(ar)) {
                if ((m = m_pullup(m, arphdr_len(ar))) == NULL) {
                        log(LOG_ERR, "arp: runt packet\n");
                        return;
                }
                ar = mtod(m, struct arphdr *);
        }

        switch (ntohs(ar->ar_pro)) {
#ifdef INET
        case ETHERTYPE_IP:
                in_arpinput(m);
                return;
#endif
        }
        m_freem(m);
        /* msg was embedded in the mbuf, do not reply! */
}

#ifdef INET
/*
 * ARP for Internet protocols on 10 Mb/s Ethernet.
 * Algorithm is that given in RFC 826.
 * In addition, a sanity check is performed on the sender
 * protocol address, to catch impersonators.
 * We no longer handle negotiations for use of trailer protocol:
 * Formerly, ARP replied for protocol type ETHERTYPE_TRAIL sent
 * along with IP replies if we wanted trailers sent to us,
 * and also sent them in response to IP replies.
 * This allowed either end to announce the desire to receive
 * trailer packets.
 * We no longer reply to requests for ETHERTYPE_TRAIL protocol either,
 * but formerly didn't normally send requests.
 */

static int      log_arp_wrong_iface = 1;
static int      log_arp_movements = 1;
static int      log_arp_permanent_modify = 1;
static int      log_arp_creation_failure = 1;

SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_wrong_iface, CTLFLAG_RW,
           &log_arp_wrong_iface, 0,
           "Log arp packets arriving on the wrong interface");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_movements, CTLFLAG_RW,
           &log_arp_movements, 0,
           "Log arp replies from MACs different than the one in the cache");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_permanent_modify, CTLFLAG_RW,
           &log_arp_permanent_modify, 0,
           "Log arp replies from MACs different than the one "
           "in the permanent arp entry");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_creation_failure, CTLFLAG_RW,
           &log_arp_creation_failure, 0, "Log arp creation failure");

/*
 * Returns non-zero if the routine updated anything.
 */
static int
arp_update_oncpu(struct mbuf *m, in_addr_t saddr, boolean_t create,
                 boolean_t generate_report, boolean_t dologging)
{
        struct arphdr *ah = mtod(m, struct arphdr *);
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct llinfo_arp *la;
        struct sockaddr_dl *sdl;
        struct rtentry *rt;
        char hexstr[2][64];
        char sbuf[INET_ADDRSTRLEN];
        int changed = create;

        KASSERT(curthread->td_type == TD_TYPE_NETISR,
            ("arp update not in netisr"));

        la = arplookup(saddr, create, generate_report, FALSE);
        if (la && (rt = la->la_rt) && (sdl = SDL(rt->rt_gateway))) {
                struct in_addr isaddr = { saddr };

                /*
                 * Normally arps coming in on the wrong interface are ignored,
                 * but if we are bridging and the two interfaces belong to
                 * the same bridge, or one is a member of the bridge which
                 * is the other, then it isn't an error.
                 */
                if (rt->rt_ifp != ifp) {
                        /*
                         * (1) ifp and rt_ifp both members of same bridge
                         * (2) rt_ifp member of bridge ifp
                         * (3) ifp member of bridge rt_ifp
                         *
                         * Always replace rt_ifp with the bridge ifc.
                         */
                        struct ifnet *nifp;

                        if (ifp->if_bridge &&
                            rt->rt_ifp->if_bridge == ifp->if_bridge) {
                                nifp = ether_bridge_interface(ifp);
                        } else if (rt->rt_ifp->if_bridge &&
                                   ether_bridge_interface(rt->rt_ifp) == ifp) {
                                nifp = ifp;
                        } else if (ifp->if_bridge &&
                                   ether_bridge_interface(ifp) == rt->rt_ifp) {
                                nifp = rt->rt_ifp;
                        } else {
                                nifp = NULL;
                        }

                        if ((log_arp_wrong_iface == 1 && nifp == NULL) ||
                            log_arp_wrong_iface == 2) {
                                hexncpy((u_char *)ar_sha(ah), ifp->if_addrlen,
                                    hexstr[0], HEX_NCPYLEN(ifp->if_addrlen), ":");
                                log(LOG_ERR,
                                    "arp: %s is on %s "
                                    "but got reply from %s on %s\n",
                                    kinet_ntoa(isaddr, sbuf),
                                    rt->rt_ifp->if_xname, hexstr[0],
                                    ifp->if_xname);
                        }
                        if (nifp == NULL)
                                return 0;

                        /*
                         * nifp is our man!  Replace rt_ifp and adjust
                         * the sdl.
                         */
                        ifp = rt->rt_ifp = nifp;
                        if (sdl->sdl_type != ifp->if_type) {
                                sdl->sdl_type = ifp->if_type;
                                changed = 1;
                        }
                        if (sdl->sdl_index != ifp->if_index) {
                                sdl->sdl_index = ifp->if_index;
                                changed = 1;
                        }
                }
                if (sdl->sdl_alen &&
                    bcmp(ar_sha(ah), LLADDR(sdl), sdl->sdl_alen)) {
                        changed = 1;
                        if (rt->rt_expire != 0) {
                                if (dologging && log_arp_movements) {
                                        hexncpy((u_char *)LLADDR(sdl), ifp->if_addrlen,
                                            hexstr[0], HEX_NCPYLEN(ifp->if_addrlen), ":");
                                        hexncpy((u_char *)ar_sha(ah), ifp->if_addrlen,
                                            hexstr[1], HEX_NCPYLEN(ifp->if_addrlen), ":");
                                        log(LOG_INFO,
                                            "arp: %s moved from %s to %s on %s\n",
                                            kinet_ntoa(isaddr, sbuf), hexstr[0], hexstr[1],
                                            ifp->if_xname);
                                }
                        } else {
                                if (dologging && log_arp_permanent_modify) {
                                        hexncpy((u_char *)ar_sha(ah), ifp->if_addrlen,
                                            hexstr[0], HEX_NCPYLEN(ifp->if_addrlen), ":");
                                        log(LOG_ERR,
                                        "arp: %s attempts to modify "
                                        "permanent entry for %s on %s\n",
                                        hexstr[0], kinet_ntoa(isaddr, sbuf), ifp->if_xname);
                                }
                                return changed;
                        }
                }
                /*
                 * sanity check for the address length.
                 * XXX this does not work for protocols with variable address
                 * length. -is
                 */
                if (dologging && sdl->sdl_alen && sdl->sdl_alen != ah->ar_hln) {
                        hexncpy((u_char *)ar_sha(ah), ifp->if_addrlen,
                            hexstr[0], HEX_NCPYLEN(ifp->if_addrlen), ":");
                        log(LOG_WARNING,
                            "arp from %s: new addr len %d, was %d",
                            hexstr[0], ah->ar_hln, sdl->sdl_alen);
                }
                if (ifp->if_addrlen != ah->ar_hln) {
                        if (dologging) {
                                hexncpy((u_char *)ar_sha(ah), ifp->if_addrlen,
                                    hexstr[0], HEX_NCPYLEN(ifp->if_addrlen), ":");
                                log(LOG_WARNING,
                                "arp from %s: addr len: new %d, i/f %d "
                                "(ignored)", hexstr[0],
                                ah->ar_hln, ifp->if_addrlen);
                        }
                        return changed;
                }
                memcpy(LLADDR(sdl), ar_sha(ah), sdl->sdl_alen = ah->ar_hln);
                if (rt->rt_expire != 0) {
                        if (rt->rt_expire != time_uptime + arpt_keep &&
                            rt->rt_expire != time_uptime + arpt_keep - 1) {
                                rt->rt_expire = time_uptime + arpt_keep;
                                changed = 1;
                        }
                }
                if (rt->rt_flags & RTF_REJECT) {
                        rt->rt_flags &= ~RTF_REJECT;
                        changed = 1;
                }
                if (la->la_asked != 0) {
                        la->la_asked = 0;
                        changed = 1;
                }
                if (la->la_preempt != arp_maxtries) {
                        la->la_preempt = arp_maxtries;
                        changed = 1;
                }

                /*
                 * This particular cpu might have been holding an mbuf
                 * pending ARP resolution.  If so, transmit the mbuf now.
                 */
                if (la->la_hold != NULL) {
                        struct mbuf *m = la->la_hold;

                        la->la_hold = NULL;
                        m_adj(m, sizeof(struct ether_header));
                        ifp->if_output(ifp, m, rt_key(rt), rt);
                        changed = 1;
                }
        }
        return changed;
}

/*
 * Called from arpintr() - this routine is run from a single cpu.
 */
static void
in_arpinput(struct mbuf *m)
{
        struct arphdr *ah;
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct ifaddr_container *ifac;
        struct in_ifaddr_container *iac;
        struct in_ifaddr *ia = NULL;
        struct in_addr isaddr, itaddr, myaddr;
        uint8_t *enaddr = NULL;
        int req_len;
        int changed;
        char hexstr[64], sbuf[INET_ADDRSTRLEN];

        req_len = arphdr_len2(ifp->if_addrlen, sizeof(struct in_addr));
        if (m->m_len < req_len && (m = m_pullup(m, req_len)) == NULL) {
                log(LOG_ERR, "in_arp: runt packet -- m_pullup failed\n");
                return;
        }

        ah = mtod(m, struct arphdr *);
        memcpy(&isaddr, ar_spa(ah), sizeof isaddr);
        memcpy(&itaddr, ar_tpa(ah), sizeof itaddr);

        /*
         * Check both target and sender IP addresses:
         *
         * If we receive the packet on the interface owning the address,
         * then accept the address.
         *
         * For a bridge, we accept the address if the receive interface and
         * the interface owning the address are on the same bridge, and
         * use the bridge MAC as the is-at response.  The bridge will be
         * responsible for handling the packet.
         *
         * (0) Check target IP against CARP IPs
         */
#ifdef CARP
        LIST_FOREACH(iac, INADDR_HASH(itaddr.s_addr), ia_hash) {
                int is_match = 0, is_parent = 0;

                ia = iac->ia;

                /* Skip all ia's which don't match */
                if (itaddr.s_addr != ia->ia_addr.sin_addr.s_addr)
                        continue;

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

                if (carp_parent(ia->ia_ifp) == ifp)
                        is_parent = 1;
                if (is_parent || ia->ia_ifp == ifp)
                        is_match = carp_iamatch(ia);

                if (is_match) {
                        if (is_parent) {
                                /*
                                 * The parent interface will also receive
                                 * the ethernet broadcast packets, e.g. ARP
                                 * REQUEST, so if we could find a CARP
                                 * interface of the parent that could match
                                 * the target IP address, we then drop the
                                 * packets, which is delieverd to us through
                                 * the parent interface.
                                 */
                                m_freem(m);
                                return;
                        }
                        goto match;
                }
        }
#endif  /* CARP */

        /*
         * (1) Check target IP against our local IPs
         */
        LIST_FOREACH(iac, INADDR_HASH(itaddr.s_addr), ia_hash) {
                ia = iac->ia;

                /* Skip all ia's which don't match */
                if (itaddr.s_addr != ia->ia_addr.sin_addr.s_addr)
                        continue;

#ifdef CARP
                /* CARP interfaces are checked in (0) */
                if (ia->ia_ifp->if_type == IFT_CARP)
                        continue;
#endif

                if (ifp->if_bridge && ia->ia_ifp &&
                    ifp->if_bridge == ia->ia_ifp->if_bridge) {
                        ifp = ether_bridge_interface(ifp);
                        goto match;
                }
                if (ia->ia_ifp && ia->ia_ifp->if_bridge &&
                    ether_bridge_interface(ia->ia_ifp) == ifp) {
                        goto match;
                }
                if (ifp->if_bridge && ether_bridge_interface(ifp) ==
                    ia->ia_ifp) {
                        goto match;
                }
                if (ia->ia_ifp == ifp) {
                        goto match;
                }
        }

        /*
         * (2) Check sender IP against our local IPs
         */
        LIST_FOREACH(iac, INADDR_HASH(isaddr.s_addr), ia_hash) {
                ia = iac->ia;

                /* Skip all ia's which don't match */
                if (isaddr.s_addr != ia->ia_addr.sin_addr.s_addr)
                        continue;

                if (ifp->if_bridge && ia->ia_ifp &&
                    ifp->if_bridge == ia->ia_ifp->if_bridge) {
                        ifp = ether_bridge_interface(ifp);
                        goto match;
                }
                if (ia->ia_ifp && ia->ia_ifp->if_bridge &&
                    ether_bridge_interface(ia->ia_ifp) == ifp) {
                        goto match;
                }
                if (ifp->if_bridge && ether_bridge_interface(ifp) ==
                    ia->ia_ifp) {
                        goto match;
                }

                if (ia->ia_ifp == ifp)
                        goto match;
        }

        /*
         * No match, use the first inet address on the receive interface
         * as a dummy address for the rest of the function.
         */
        TAILQ_FOREACH(ifac, &ifp->if_addrheads[mycpuid], ifa_link) {
                struct ifaddr *ifa = ifac->ifa;

                if (ifa->ifa_addr && ifa->ifa_addr->sa_family == AF_INET) {
                        ia = ifatoia(ifa);
                        goto match;
                }
        }

        /*
         * If we got here, we didn't find any suitable interface,
         * so drop the packet.
         */
        m_freem(m);
        return;

match:
        if (!enaddr)
                enaddr = (uint8_t *)IF_LLADDR(ifp);
        myaddr = ia->ia_addr.sin_addr;
        if (!bcmp(ar_sha(ah), enaddr, ifp->if_addrlen)) {
                m_freem(m);     /* it's from me, ignore it. */
                return;
        }
        if (!bcmp(ar_sha(ah), ifp->if_broadcastaddr, ifp->if_addrlen)) {
                log(LOG_ERR,
                    "arp: link address is broadcast for IP address %s!\n",
                    kinet_ntoa(isaddr, sbuf));
                m_freem(m);
                return;
        }
        if (isaddr.s_addr == myaddr.s_addr && myaddr.s_addr != 0) {
                hexncpy((u_char *)ar_sha(ah), ifp->if_addrlen,
                    hexstr, HEX_NCPYLEN(ifp->if_addrlen), ":");
                log(LOG_ERR,
                   "arp: %s is using my IP address %s!\n",
                    hexstr, kinet_ntoa(isaddr, sbuf));
                itaddr = myaddr;
                goto reply;
        }
        if (ifp->if_flags & IFF_STATICARP)
                goto reply;

        /*
         * When arp_restricted_match is true and the ARP response is not
         * specifically targetted to me, ignore it.  Otherwise the entry
         * timeout may be updated for an old MAC.
         */
        if (arp_restricted_match && itaddr.s_addr != myaddr.s_addr) {
                m_freem(m);
                return;
        }

        /*
         * Update all CPU's routing tables with this ARP packet.
         *
         * However, we only need to generate rtmsg on CPU0.
         */
        ASSERT_IN_NETISR(0);
        changed = arp_update_oncpu(m, isaddr.s_addr,
                                   itaddr.s_addr == myaddr.s_addr,
                                   RTL_REPORTMSG, TRUE);

        if (ncpus > 1 && changed) {
                struct netmsg_inarp *msg = &m->m_hdr.mh_arpmsg;

                netmsg_init(&msg->base, NULL, &netisr_apanic_rport,
                            0, arp_update_msghandler);
                msg->m = m;
                msg->saddr = isaddr.s_addr;
                msg->taddr = itaddr.s_addr;
                msg->myaddr = myaddr.s_addr;
                lwkt_sendmsg(netisr_cpuport(1), &msg->base.lmsg);
        } else {
                goto reply;
        }

        /*
         * Just return here; after all CPUs's routing tables are
         * properly updated by this ARP packet, an ARP reply will
         * be generated if appropriate.
         */
        return;
reply:
        in_arpreply(m, itaddr.s_addr, myaddr.s_addr);
}

static void
arp_reply_msghandler(netmsg_t msg)
{
        struct netmsg_inarp *rmsg = (struct netmsg_inarp *)msg;

        in_arpreply(rmsg->m, rmsg->taddr, rmsg->myaddr);
        /* Don't reply this netmsg; netmsg_inarp is embedded in mbuf */
}

static void
arp_update_msghandler(netmsg_t msg)
{
        struct netmsg_inarp *rmsg = (struct netmsg_inarp *)msg;
        int nextcpu;

        /*
         * This message handler will be called on all of the APs;
         * no need to generate rtmsg on them.
         */
        KASSERT(mycpuid > 0, ("arp update msg on cpu%d", mycpuid));
        arp_update_oncpu(rmsg->m, rmsg->saddr,
                         rmsg->taddr == rmsg->myaddr,
                         RTL_DONTREPORT, FALSE);

        nextcpu = mycpuid + 1;
        if (nextcpu < ncpus) {
                lwkt_forwardmsg(netisr_cpuport(nextcpu), &rmsg->base.lmsg);
        } else {
                struct mbuf *m = rmsg->m;
                in_addr_t saddr = rmsg->saddr;
                in_addr_t taddr = rmsg->taddr;
                in_addr_t myaddr = rmsg->myaddr;

                /*
                 * Dispatch this mbuf to netisr0 to perform ARP reply,
                 * if appropriate.
                 * NOTE: netmsg_inarp is embedded in this mbuf.
                 */
                netmsg_init(&rmsg->base, NULL, &netisr_apanic_rport,
                    0, arp_reply_msghandler);
                rmsg->m = m;
                rmsg->saddr = saddr;
                rmsg->taddr = taddr;
                rmsg->myaddr = myaddr;
                lwkt_sendmsg(netisr_cpuport(0), &rmsg->base.lmsg);
        }
}

static void
in_arpreply(struct mbuf *m, in_addr_t taddr, in_addr_t myaddr)
{
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        const uint8_t *enaddr;
        struct arphdr *ah;
        struct sockaddr sa;
        struct ether_header *eh;

        ah = mtod(m, struct arphdr *);
        if (ntohs(ah->ar_op) != ARPOP_REQUEST) {
                m_freem(m);
                return;
        }

        enaddr = (const uint8_t *)IF_LLADDR(ifp);
        if (taddr == myaddr) {
                /* I am the target */
                memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
                memcpy(ar_sha(ah), enaddr, ah->ar_hln);
        } else {
                struct llinfo_arp *la;
                struct rtentry *rt;

                la = arplookup(taddr, FALSE, RTL_DONTREPORT, SIN_PROXY);
                if (la == NULL) {
                        struct sockaddr_in sin;
#ifdef DEBUG_PROXY
                        char tbuf[INET_ADDRSTRLEN];
#endif

                        if (!arp_proxyall) {
                                m_freem(m);
                                return;
                        }

                        bzero(&sin, sizeof sin);
                        sin.sin_family = AF_INET;
                        sin.sin_len = sizeof sin;
                        sin.sin_addr.s_addr = taddr;

                        rt = rtpurelookup((struct sockaddr *)&sin);
                        if (rt == NULL) {
                                m_freem(m);
                                return;
                        }
                        --rt->rt_refcnt;
                        /*
                         * Don't send proxies for nodes on the same interface
                         * as this one came out of, or we'll get into a fight
                         * over who claims what Ether address.
                         */
                        if (rt->rt_ifp == ifp) {
                                m_freem(m);
                                return;
                        }
                        memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
                        memcpy(ar_sha(ah), enaddr, ah->ar_hln);
#ifdef DEBUG_PROXY
                        kprintf("arp: proxying for %s\n",
                            kinet_ntoa(itaddr, tbuf));
#endif
                } else {
                        struct sockaddr_dl *sdl;

                        rt = la->la_rt;
                        memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
                        sdl = SDL(rt->rt_gateway);
                        memcpy(ar_sha(ah), LLADDR(sdl), ah->ar_hln);
                }
        }

        memcpy(ar_tpa(ah), ar_spa(ah), ah->ar_pln);
        memcpy(ar_spa(ah), &taddr, ah->ar_pln);
        ah->ar_op = htons(ARPOP_REPLY);
        ah->ar_pro = htons(ETHERTYPE_IP); /* let's be sure! */
        switch (ifp->if_type) {
        case IFT_ETHER:
                /*
                 * May not be correct for types not explictly
                 * listed, but it is our best guess.
                 */
        default:
                eh = (struct ether_header *)sa.sa_data;
                memcpy(eh->ether_dhost, ar_tha(ah), sizeof eh->ether_dhost);
                eh->ether_type = htons(ETHERTYPE_ARP);
                break;
        }
        sa.sa_family = AF_UNSPEC;
        sa.sa_len = sizeof sa;
        ifp->if_output(ifp, m, &sa, NULL);
}

#endif  /* INET */

/*
 * Free an arp entry.  If the arp entry is actively referenced or represents
 * a static entry we only clear it back to an unresolved state, otherwise
 * we destroy the entry entirely.
 *
 * Note that static entries are created when route add ... -interface is used
 * to create an interface route to a (direct) destination.
 */
static void
arptfree(struct llinfo_arp *la)
{
        struct rtentry *rt = la->la_rt;
        struct sockaddr_dl *sdl;

        if (rt == NULL)
                panic("arptfree");
        sdl = SDL(rt->rt_gateway);
        if (sdl != NULL &&
            ((rt->rt_refcnt > 0 && sdl->sdl_family == AF_LINK) ||
             (rt->rt_flags & RTF_STATIC))) {
                sdl->sdl_alen = 0;
                la->la_preempt = la->la_asked = 0;
                rt->rt_flags &= ~RTF_REJECT;
                return;
        }
        rtrequest(RTM_DELETE, rt_key(rt), NULL, rt_mask(rt), 0, NULL);
}

/*
 * Lookup or enter a new address in arptab.
 */
static struct llinfo_arp *
arplookup(in_addr_t addr, boolean_t create, boolean_t generate_report,
          boolean_t proxy)
{
        struct rtentry *rt;
        struct sockaddr_inarp sin = { sizeof sin, AF_INET };
        const char *why = NULL;

        /* Check ARP probes, e.g. from Cisco switches. */
        if (addr == INADDR_ANY && arp_ignore_probes)
                return (NULL);

        sin.sin_addr.s_addr = addr;
        sin.sin_other = proxy ? SIN_PROXY : 0;
        if (create) {
                rt = _rtlookup((struct sockaddr *)&sin,
                               generate_report, RTL_DOCLONE);
        } else {
                rt = rtpurelookup((struct sockaddr *)&sin);
        }
        if (rt == NULL)
                return (NULL);
        rt->rt_refcnt--;

        if (rt->rt_flags & RTF_GATEWAY)
                why = "host is not on local network";
        else if (!(rt->rt_flags & RTF_LLINFO))
                why = "could not allocate llinfo";
        else if (rt->rt_gateway->sa_family != AF_LINK)
                why = "gateway route is not ours";

        if (why) {
                if (create && log_arp_creation_failure) {
                        char abuf[INET_ADDRSTRLEN];

                        log(LOG_DEBUG, "arplookup %s failed: %s\n",
                            kinet_ntoa(sin.sin_addr, abuf), why);
                }
                if (rt->rt_refcnt <= 0 && (rt->rt_flags & RTF_WASCLONED)) {
                        /* No references to this route.  Purge it. */
                        rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway,
                                  rt_mask(rt), rt->rt_flags, NULL);
                }
                return (NULL);
        }
        return (rt->rt_llinfo);
}

void
arp_ifinit(struct ifnet *ifp, struct ifaddr *ifa)
{
        ifa->ifa_rtrequest = arp_rtrequest;
        ifa->ifa_flags |= RTF_CLONING;
}

void
arp_gratuitous(struct ifnet *ifp, struct ifaddr *ifa)
{
        if (IA_SIN(ifa)->sin_addr.s_addr != INADDR_ANY) {
                arprequest_async(ifp, &IA_SIN(ifa)->sin_addr,
                                 &IA_SIN(ifa)->sin_addr, NULL);
        }
}

static void
arp_ifaddr(void *arg __unused, struct ifnet *ifp,
    enum ifaddr_event event, struct ifaddr *ifa)
{
        if (ifa->ifa_rtrequest != arp_rtrequest) /* XXX need a generic way */
                return;
        if (ifa->ifa_addr->sa_family != AF_INET)
                return;
        if (event == IFADDR_EVENT_DELETE)
                return;

        /*
         * - CARP interfaces will take care of gratuitous ARP themselves.
         * - If we are the CARP interface's parent, don't send gratuitous
         *   ARP to avoid unnecessary confusion.
         */
#ifdef CARP
        if (ifp->if_type != IFT_CARP && ifp->if_carp == NULL)
#endif
        {
                arp_gratuitous(ifp, ifa);
        }
}

static void
arp_init(void)
{
        int cpu;

        for (cpu = 0; cpu < ncpus; cpu++) {
                struct arp_pcpu_data *ad = &arp_data[cpu];

                LIST_INIT(&ad->llinfo_list);
                netmsg_init(&ad->timer_nmsg, NULL, &netisr_adone_rport,
                    MSGF_PRIORITY, arptimer_dispatch);
                callout_init_mp(&ad->timer_ch);

                callout_reset_bycpu(&ad->timer_ch, hz, arptimer, NULL, cpu);
        }

        netisr_register(NETISR_ARP, arpintr, NULL);

        EVENTHANDLER_REGISTER(ifaddr_event, arp_ifaddr, NULL,
            EVENTHANDLER_PRI_LAST);
}

SYSINIT(arp, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY, arp_init, 0);