The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/netinet/if_ether.c

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1988, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)if_ether.c  8.1 (Berkeley) 6/10/93
   30  */
   31 
   32 /*
   33  * Ethernet address resolution protocol.
   34  * TODO:
   35  *      add "inuse/lock" bit (or ref. count) along with valid bit
   36  */
   37 
   38 #include <sys/cdefs.h>
   39 __FBSDID("$FreeBSD: releng/11.0/sys/netinet/if_ether.c 303698 2016-08-03 06:32:44Z karels $");
   40 
   41 #include "opt_inet.h"
   42 
   43 #include <sys/param.h>
   44 #include <sys/kernel.h>
   45 #include <sys/lock.h>
   46 #include <sys/queue.h>
   47 #include <sys/sysctl.h>
   48 #include <sys/systm.h>
   49 #include <sys/mbuf.h>
   50 #include <sys/malloc.h>
   51 #include <sys/proc.h>
   52 #include <sys/rmlock.h>
   53 #include <sys/socket.h>
   54 #include <sys/syslog.h>
   55 
   56 #include <net/if.h>
   57 #include <net/if_var.h>
   58 #include <net/if_dl.h>
   59 #include <net/if_types.h>
   60 #include <net/netisr.h>
   61 #include <net/ethernet.h>
   62 #include <net/route.h>
   63 #include <net/vnet.h>
   64 
   65 #include <netinet/in.h>
   66 #include <netinet/in_fib.h>
   67 #include <netinet/in_var.h>
   68 #include <net/if_llatbl.h>
   69 #include <netinet/if_ether.h>
   70 #ifdef INET
   71 #include <netinet/ip_carp.h>
   72 #endif
   73 
   74 #include <security/mac/mac_framework.h>
   75 
   76 #define SIN(s) ((const struct sockaddr_in *)(s))
   77 
   78 static struct timeval arp_lastlog;
   79 static int arp_curpps;
   80 static int arp_maxpps = 1;
   81 
   82 /* Simple ARP state machine */
   83 enum arp_llinfo_state {
   84         ARP_LLINFO_INCOMPLETE = 0, /* No LLE data */
   85         ARP_LLINFO_REACHABLE,   /* LLE is valid */
   86         ARP_LLINFO_VERIFY,      /* LLE is valid, need refresh */
   87         ARP_LLINFO_DELETED,     /* LLE is deleted */
   88 };
   89 
   90 SYSCTL_DECL(_net_link_ether);
   91 static SYSCTL_NODE(_net_link_ether, PF_INET, inet, CTLFLAG_RW, 0, "");
   92 static SYSCTL_NODE(_net_link_ether, PF_ARP, arp, CTLFLAG_RW, 0, "");
   93 
   94 /* timer values */
   95 static VNET_DEFINE(int, arpt_keep) = (20*60);   /* once resolved, good for 20
   96                                                  * minutes */
   97 static VNET_DEFINE(int, arp_maxtries) = 5;
   98 static VNET_DEFINE(int, arp_proxyall) = 0;
   99 static VNET_DEFINE(int, arpt_down) = 20;        /* keep incomplete entries for
  100                                                  * 20 seconds */
  101 static VNET_DEFINE(int, arpt_rexmit) = 1;       /* retransmit arp entries, sec*/
  102 VNET_PCPUSTAT_DEFINE(struct arpstat, arpstat);  /* ARP statistics, see if_arp.h */
  103 VNET_PCPUSTAT_SYSINIT(arpstat);
  104 
  105 #ifdef VIMAGE
  106 VNET_PCPUSTAT_SYSUNINIT(arpstat);
  107 #endif /* VIMAGE */
  108 
  109 static VNET_DEFINE(int, arp_maxhold) = 1;
  110 
  111 #define V_arpt_keep             VNET(arpt_keep)
  112 #define V_arpt_down             VNET(arpt_down)
  113 #define V_arpt_rexmit           VNET(arpt_rexmit)
  114 #define V_arp_maxtries          VNET(arp_maxtries)
  115 #define V_arp_proxyall          VNET(arp_proxyall)
  116 #define V_arp_maxhold           VNET(arp_maxhold)
  117 
  118 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, max_age, CTLFLAG_VNET | CTLFLAG_RW,
  119         &VNET_NAME(arpt_keep), 0,
  120         "ARP entry lifetime in seconds");
  121 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, maxtries, CTLFLAG_VNET | CTLFLAG_RW,
  122         &VNET_NAME(arp_maxtries), 0,
  123         "ARP resolution attempts before returning error");
  124 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, proxyall, CTLFLAG_VNET | CTLFLAG_RW,
  125         &VNET_NAME(arp_proxyall), 0,
  126         "Enable proxy ARP for all suitable requests");
  127 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, wait, CTLFLAG_VNET | CTLFLAG_RW,
  128         &VNET_NAME(arpt_down), 0,
  129         "Incomplete ARP entry lifetime in seconds");
  130 SYSCTL_VNET_PCPUSTAT(_net_link_ether_arp, OID_AUTO, stats, struct arpstat,
  131     arpstat, "ARP statistics (struct arpstat, net/if_arp.h)");
  132 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, maxhold, CTLFLAG_VNET | CTLFLAG_RW,
  133         &VNET_NAME(arp_maxhold), 0,
  134         "Number of packets to hold per ARP entry");
  135 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, max_log_per_second,
  136         CTLFLAG_RW, &arp_maxpps, 0,
  137         "Maximum number of remotely triggered ARP messages that can be "
  138         "logged per second");
  139 
  140 #define ARP_LOG(pri, ...)       do {                                    \
  141         if (ppsratecheck(&arp_lastlog, &arp_curpps, arp_maxpps))        \
  142                 log((pri), "arp: " __VA_ARGS__);                        \
  143 } while (0)
  144 
  145 
  146 static void     arpintr(struct mbuf *);
  147 static void     arptimer(void *);
  148 #ifdef INET
  149 static void     in_arpinput(struct mbuf *);
  150 #endif
  151 
  152 static void arp_check_update_lle(struct arphdr *ah, struct in_addr isaddr,
  153     struct ifnet *ifp, int bridged, struct llentry *la);
  154 static void arp_mark_lle_reachable(struct llentry *la);
  155 static void arp_iflladdr(void *arg __unused, struct ifnet *ifp);
  156 
  157 static eventhandler_tag iflladdr_tag;
  158 
  159 static const struct netisr_handler arp_nh = {
  160         .nh_name = "arp",
  161         .nh_handler = arpintr,
  162         .nh_proto = NETISR_ARP,
  163         .nh_policy = NETISR_POLICY_SOURCE,
  164 };
  165 
  166 /*
  167  * Timeout routine.  Age arp_tab entries periodically.
  168  */
  169 static void
  170 arptimer(void *arg)
  171 {
  172         struct llentry *lle = (struct llentry *)arg;
  173         struct ifnet *ifp;
  174         int r_skip_req;
  175 
  176         if (lle->la_flags & LLE_STATIC) {
  177                 return;
  178         }
  179         LLE_WLOCK(lle);
  180         if (callout_pending(&lle->lle_timer)) {
  181                 /*
  182                  * Here we are a bit odd here in the treatment of 
  183                  * active/pending. If the pending bit is set, it got
  184                  * rescheduled before I ran. The active
  185                  * bit we ignore, since if it was stopped
  186                  * in ll_tablefree() and was currently running
  187                  * it would have return 0 so the code would
  188                  * not have deleted it since the callout could
  189                  * not be stopped so we want to go through
  190                  * with the delete here now. If the callout
  191                  * was restarted, the pending bit will be back on and
  192                  * we just want to bail since the callout_reset would
  193                  * return 1 and our reference would have been removed
  194                  * by arpresolve() below.
  195                  */
  196                 LLE_WUNLOCK(lle);
  197                 return;
  198         }
  199         ifp = lle->lle_tbl->llt_ifp;
  200         CURVNET_SET(ifp->if_vnet);
  201 
  202         switch (lle->ln_state) {
  203         case ARP_LLINFO_REACHABLE:
  204 
  205                 /*
  206                  * Expiration time is approaching.
  207                  * Let's try to refresh entry if it is still
  208                  * in use.
  209                  *
  210                  * Set r_skip_req to get feedback from
  211                  * fast path. Change state and re-schedule
  212                  * ourselves.
  213                  */
  214                 LLE_REQ_LOCK(lle);
  215                 lle->r_skip_req = 1;
  216                 LLE_REQ_UNLOCK(lle);
  217                 lle->ln_state = ARP_LLINFO_VERIFY;
  218                 callout_schedule(&lle->lle_timer, hz * V_arpt_rexmit);
  219                 LLE_WUNLOCK(lle);
  220                 CURVNET_RESTORE();
  221                 return;
  222         case ARP_LLINFO_VERIFY:
  223                 LLE_REQ_LOCK(lle);
  224                 r_skip_req = lle->r_skip_req;
  225                 LLE_REQ_UNLOCK(lle);
  226 
  227                 if (r_skip_req == 0 && lle->la_preempt > 0) {
  228                         /* Entry was used, issue refresh request */
  229                         struct in_addr dst;
  230                         dst = lle->r_l3addr.addr4;
  231                         lle->la_preempt--;
  232                         callout_schedule(&lle->lle_timer, hz * V_arpt_rexmit);
  233                         LLE_WUNLOCK(lle);
  234                         arprequest(ifp, NULL, &dst, NULL);
  235                         CURVNET_RESTORE();
  236                         return;
  237                 }
  238                 /* Nothing happened. Reschedule if not too late */
  239                 if (lle->la_expire > time_uptime) {
  240                         callout_schedule(&lle->lle_timer, hz * V_arpt_rexmit);
  241                         LLE_WUNLOCK(lle);
  242                         CURVNET_RESTORE();
  243                         return;
  244                 }
  245                 break;
  246         case ARP_LLINFO_INCOMPLETE:
  247         case ARP_LLINFO_DELETED:
  248                 break;
  249         }
  250 
  251         if ((lle->la_flags & LLE_DELETED) == 0) {
  252                 int evt;
  253 
  254                 if (lle->la_flags & LLE_VALID)
  255                         evt = LLENTRY_EXPIRED;
  256                 else
  257                         evt = LLENTRY_TIMEDOUT;
  258                 EVENTHANDLER_INVOKE(lle_event, lle, evt);
  259         }
  260 
  261         callout_stop(&lle->lle_timer);
  262 
  263         /* XXX: LOR avoidance. We still have ref on lle. */
  264         LLE_WUNLOCK(lle);
  265         IF_AFDATA_LOCK(ifp);
  266         LLE_WLOCK(lle);
  267 
  268         /* Guard against race with other llentry_free(). */
  269         if (lle->la_flags & LLE_LINKED) {
  270                 LLE_REMREF(lle);
  271                 lltable_unlink_entry(lle->lle_tbl, lle);
  272         }
  273         IF_AFDATA_UNLOCK(ifp);
  274 
  275         size_t pkts_dropped = llentry_free(lle);
  276 
  277         ARPSTAT_ADD(dropped, pkts_dropped);
  278         ARPSTAT_INC(timeouts);
  279 
  280         CURVNET_RESTORE();
  281 }
  282 
  283 /*
  284  * Stores link-layer header for @ifp in format suitable for if_output()
  285  * into buffer @buf. Resulting header length is stored in @bufsize.
  286  *
  287  * Returns 0 on success.
  288  */
  289 static int
  290 arp_fillheader(struct ifnet *ifp, struct arphdr *ah, int bcast, u_char *buf,
  291     size_t *bufsize)
  292 {
  293         struct if_encap_req ereq;
  294         int error;
  295 
  296         bzero(buf, *bufsize);
  297         bzero(&ereq, sizeof(ereq));
  298         ereq.buf = buf;
  299         ereq.bufsize = *bufsize;
  300         ereq.rtype = IFENCAP_LL;
  301         ereq.family = AF_ARP;
  302         ereq.lladdr = ar_tha(ah);
  303         ereq.hdata = (u_char *)ah;
  304         if (bcast)
  305                 ereq.flags = IFENCAP_FLAG_BROADCAST;
  306         error = ifp->if_requestencap(ifp, &ereq);
  307         if (error == 0)
  308                 *bufsize = ereq.bufsize;
  309 
  310         return (error);
  311 }
  312 
  313 
  314 /*
  315  * Broadcast an ARP request. Caller specifies:
  316  *      - arp header source ip address
  317  *      - arp header target ip address
  318  *      - arp header source ethernet address
  319  */
  320 void
  321 arprequest(struct ifnet *ifp, const struct in_addr *sip,
  322     const struct in_addr *tip, u_char *enaddr)
  323 {
  324         struct mbuf *m;
  325         struct arphdr *ah;
  326         struct sockaddr sa;
  327         u_char *carpaddr = NULL;
  328         uint8_t linkhdr[LLE_MAX_LINKHDR];
  329         size_t linkhdrsize;
  330         struct route ro;
  331         int error;
  332 
  333         if (sip == NULL) {
  334                 /*
  335                  * The caller did not supply a source address, try to find
  336                  * a compatible one among those assigned to this interface.
  337                  */
  338                 struct ifaddr *ifa;
  339 
  340                 IF_ADDR_RLOCK(ifp);
  341                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
  342                         if (ifa->ifa_addr->sa_family != AF_INET)
  343                                 continue;
  344 
  345                         if (ifa->ifa_carp) {
  346                                 if ((*carp_iamatch_p)(ifa, &carpaddr) == 0)
  347                                         continue;
  348                                 sip = &IA_SIN(ifa)->sin_addr;
  349                         } else {
  350                                 carpaddr = NULL;
  351                                 sip = &IA_SIN(ifa)->sin_addr;
  352                         }
  353 
  354                         if (0 == ((sip->s_addr ^ tip->s_addr) &
  355                             IA_MASKSIN(ifa)->sin_addr.s_addr))
  356                                 break;  /* found it. */
  357                 }
  358                 IF_ADDR_RUNLOCK(ifp);
  359                 if (sip == NULL) {
  360                         printf("%s: cannot find matching address\n", __func__);
  361                         return;
  362                 }
  363         }
  364         if (enaddr == NULL)
  365                 enaddr = carpaddr ? carpaddr : (u_char *)IF_LLADDR(ifp);
  366 
  367         if ((m = m_gethdr(M_NOWAIT, MT_DATA)) == NULL)
  368                 return;
  369         m->m_len = sizeof(*ah) + 2 * sizeof(struct in_addr) +
  370                 2 * ifp->if_addrlen;
  371         m->m_pkthdr.len = m->m_len;
  372         M_ALIGN(m, m->m_len);
  373         ah = mtod(m, struct arphdr *);
  374         bzero((caddr_t)ah, m->m_len);
  375 #ifdef MAC
  376         mac_netinet_arp_send(ifp, m);
  377 #endif
  378         ah->ar_pro = htons(ETHERTYPE_IP);
  379         ah->ar_hln = ifp->if_addrlen;           /* hardware address length */
  380         ah->ar_pln = sizeof(struct in_addr);    /* protocol address length */
  381         ah->ar_op = htons(ARPOP_REQUEST);
  382         bcopy(enaddr, ar_sha(ah), ah->ar_hln);
  383         bcopy(sip, ar_spa(ah), ah->ar_pln);
  384         bcopy(tip, ar_tpa(ah), ah->ar_pln);
  385         sa.sa_family = AF_ARP;
  386         sa.sa_len = 2;
  387 
  388         /* Calculate link header for sending frame */
  389         bzero(&ro, sizeof(ro));
  390         linkhdrsize = sizeof(linkhdr);
  391         error = arp_fillheader(ifp, ah, 1, linkhdr, &linkhdrsize);
  392         if (error != 0 && error != EAFNOSUPPORT) {
  393                 ARP_LOG(LOG_ERR, "Failed to calculate ARP header on %s: %d\n",
  394                     if_name(ifp), error);
  395                 return;
  396         }
  397 
  398         ro.ro_prepend = linkhdr;
  399         ro.ro_plen = linkhdrsize;
  400         ro.ro_flags = 0;
  401 
  402         m->m_flags |= M_BCAST;
  403         m_clrprotoflags(m);     /* Avoid confusing lower layers. */
  404         (*ifp->if_output)(ifp, m, &sa, &ro);
  405         ARPSTAT_INC(txrequests);
  406 }
  407 
  408 
  409 /*
  410  * Resolve an IP address into an ethernet address - heavy version.
  411  * Used internally by arpresolve().
  412  * We have already checked than  we can't use existing lle without
  413  * modification so we have to acquire LLE_EXCLUSIVE lle lock.
  414  *
  415  * On success, desten and flags are filled in and the function returns 0;
  416  * If the packet must be held pending resolution, we return EWOULDBLOCK
  417  * On other errors, we return the corresponding error code.
  418  * Note that m_freem() handles NULL.
  419  */
  420 static int
  421 arpresolve_full(struct ifnet *ifp, int is_gw, int flags, struct mbuf *m,
  422         const struct sockaddr *dst, u_char *desten, uint32_t *pflags,
  423         struct llentry **plle)
  424 {
  425         struct llentry *la = NULL, *la_tmp;
  426         struct mbuf *curr = NULL;
  427         struct mbuf *next = NULL;
  428         int error, renew;
  429         char *lladdr;
  430         int ll_len;
  431 
  432         if (pflags != NULL)
  433                 *pflags = 0;
  434         if (plle != NULL)
  435                 *plle = NULL;
  436 
  437         if ((flags & LLE_CREATE) == 0) {
  438                 IF_AFDATA_RLOCK(ifp);
  439                 la = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
  440                 IF_AFDATA_RUNLOCK(ifp);
  441         }
  442         if (la == NULL && (ifp->if_flags & (IFF_NOARP | IFF_STATICARP)) == 0) {
  443                 la = lltable_alloc_entry(LLTABLE(ifp), 0, dst);
  444                 if (la == NULL) {
  445                         log(LOG_DEBUG,
  446                             "arpresolve: can't allocate llinfo for %s on %s\n",
  447                             inet_ntoa(SIN(dst)->sin_addr), if_name(ifp));
  448                         m_freem(m);
  449                         return (EINVAL);
  450                 }
  451 
  452                 IF_AFDATA_WLOCK(ifp);
  453                 LLE_WLOCK(la);
  454                 la_tmp = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
  455                 /* Prefer ANY existing lle over newly-created one */
  456                 if (la_tmp == NULL)
  457                         lltable_link_entry(LLTABLE(ifp), la);
  458                 IF_AFDATA_WUNLOCK(ifp);
  459                 if (la_tmp != NULL) {
  460                         lltable_free_entry(LLTABLE(ifp), la);
  461                         la = la_tmp;
  462                 }
  463         }
  464         if (la == NULL) {
  465                 m_freem(m);
  466                 return (EINVAL);
  467         }
  468 
  469         if ((la->la_flags & LLE_VALID) &&
  470             ((la->la_flags & LLE_STATIC) || la->la_expire > time_uptime)) {
  471                 if (flags & LLE_ADDRONLY) {
  472                         lladdr = la->ll_addr;
  473                         ll_len = ifp->if_addrlen;
  474                 } else {
  475                         lladdr = la->r_linkdata;
  476                         ll_len = la->r_hdrlen;
  477                 }
  478                 bcopy(lladdr, desten, ll_len);
  479 
  480                 /* Check if we have feedback request from arptimer() */
  481                 if (la->r_skip_req != 0) {
  482                         LLE_REQ_LOCK(la);
  483                         la->r_skip_req = 0; /* Notify that entry was used */
  484                         LLE_REQ_UNLOCK(la);
  485                 }
  486                 if (pflags != NULL)
  487                         *pflags = la->la_flags & (LLE_VALID|LLE_IFADDR);
  488                 if (plle) {
  489                         LLE_ADDREF(la);
  490                         *plle = la;
  491                 }
  492                 LLE_WUNLOCK(la);
  493                 return (0);
  494         }
  495 
  496         renew = (la->la_asked == 0 || la->la_expire != time_uptime);
  497         /*
  498          * There is an arptab entry, but no ethernet address
  499          * response yet.  Add the mbuf to the list, dropping
  500          * the oldest packet if we have exceeded the system
  501          * setting.
  502          */
  503         if (m != NULL) {
  504                 if (la->la_numheld >= V_arp_maxhold) {
  505                         if (la->la_hold != NULL) {
  506                                 next = la->la_hold->m_nextpkt;
  507                                 m_freem(la->la_hold);
  508                                 la->la_hold = next;
  509                                 la->la_numheld--;
  510                                 ARPSTAT_INC(dropped);
  511                         }
  512                 }
  513                 if (la->la_hold != NULL) {
  514                         curr = la->la_hold;
  515                         while (curr->m_nextpkt != NULL)
  516                                 curr = curr->m_nextpkt;
  517                         curr->m_nextpkt = m;
  518                 } else
  519                         la->la_hold = m;
  520                 la->la_numheld++;
  521         }
  522         /*
  523          * Return EWOULDBLOCK if we have tried less than arp_maxtries. It
  524          * will be masked by ether_output(). Return EHOSTDOWN/EHOSTUNREACH
  525          * if we have already sent arp_maxtries ARP requests. Retransmit the
  526          * ARP request, but not faster than one request per second.
  527          */
  528         if (la->la_asked < V_arp_maxtries)
  529                 error = EWOULDBLOCK;    /* First request. */
  530         else
  531                 error = is_gw != 0 ? EHOSTUNREACH : EHOSTDOWN;
  532 
  533         if (renew) {
  534                 int canceled;
  535 
  536                 LLE_ADDREF(la);
  537                 la->la_expire = time_uptime;
  538                 canceled = callout_reset(&la->lle_timer, hz * V_arpt_down,
  539                     arptimer, la);
  540                 if (canceled)
  541                         LLE_REMREF(la);
  542                 la->la_asked++;
  543                 LLE_WUNLOCK(la);
  544                 arprequest(ifp, NULL, &SIN(dst)->sin_addr, NULL);
  545                 return (error);
  546         }
  547 
  548         LLE_WUNLOCK(la);
  549         return (error);
  550 }
  551 
  552 /*
  553  * Resolve an IP address into an ethernet address.
  554  */
  555 int
  556 arpresolve_addr(struct ifnet *ifp, int flags, const struct sockaddr *dst,
  557     char *desten, uint32_t *pflags, struct llentry **plle)
  558 {
  559         int error;
  560 
  561         flags |= LLE_ADDRONLY;
  562         error = arpresolve_full(ifp, 0, flags, NULL, dst, desten, pflags, plle);
  563         return (error);
  564 }
  565 
  566 
  567 /*
  568  * Lookups link header based on an IP address.
  569  * On input:
  570  *    ifp is the interface we use
  571  *    is_gw != 0 if @dst represents gateway to some destination
  572  *    m is the mbuf. May be NULL if we don't have a packet.
  573  *    dst is the next hop,
  574  *    desten is the storage to put LL header.
  575  *    flags returns subset of lle flags: LLE_VALID | LLE_IFADDR
  576  *
  577  * On success, full/partial link header and flags are filled in and
  578  * the function returns 0.
  579  * If the packet must be held pending resolution, we return EWOULDBLOCK
  580  * On other errors, we return the corresponding error code.
  581  * Note that m_freem() handles NULL.
  582  */
  583 int
  584 arpresolve(struct ifnet *ifp, int is_gw, struct mbuf *m,
  585         const struct sockaddr *dst, u_char *desten, uint32_t *pflags,
  586         struct llentry **plle)
  587 {
  588         struct llentry *la = NULL;
  589 
  590         if (pflags != NULL)
  591                 *pflags = 0;
  592         if (plle != NULL)
  593                 *plle = NULL;
  594 
  595         if (m != NULL) {
  596                 if (m->m_flags & M_BCAST) {
  597                         /* broadcast */
  598                         (void)memcpy(desten,
  599                             ifp->if_broadcastaddr, ifp->if_addrlen);
  600                         return (0);
  601                 }
  602                 if (m->m_flags & M_MCAST) {
  603                         /* multicast */
  604                         ETHER_MAP_IP_MULTICAST(&SIN(dst)->sin_addr, desten);
  605                         return (0);
  606                 }
  607         }
  608 
  609         IF_AFDATA_RLOCK(ifp);
  610         la = lla_lookup(LLTABLE(ifp), plle ? LLE_EXCLUSIVE : LLE_UNLOCKED, dst);
  611         if (la != NULL && (la->r_flags & RLLE_VALID) != 0) {
  612                 /* Entry found, let's copy lle info */
  613                 bcopy(la->r_linkdata, desten, la->r_hdrlen);
  614                 if (pflags != NULL)
  615                         *pflags = LLE_VALID | (la->r_flags & RLLE_IFADDR);
  616                 /* Check if we have feedback request from arptimer() */
  617                 if (la->r_skip_req != 0) {
  618                         LLE_REQ_LOCK(la);
  619                         la->r_skip_req = 0; /* Notify that entry was used */
  620                         LLE_REQ_UNLOCK(la);
  621                 }
  622                 if (plle) {
  623                         LLE_ADDREF(la);
  624                         *plle = la;
  625                         LLE_WUNLOCK(la);
  626                 }
  627                 IF_AFDATA_RUNLOCK(ifp);
  628                 return (0);
  629         }
  630         if (plle && la)
  631                 LLE_WUNLOCK(la);
  632         IF_AFDATA_RUNLOCK(ifp);
  633 
  634         return (arpresolve_full(ifp, is_gw, la == NULL ? LLE_CREATE : 0, m, dst,
  635             desten, pflags, plle));
  636 }
  637 
  638 /*
  639  * Common length and type checks are done here,
  640  * then the protocol-specific routine is called.
  641  */
  642 static void
  643 arpintr(struct mbuf *m)
  644 {
  645         struct arphdr *ar;
  646         struct ifnet *ifp;
  647         char *layer;
  648         int hlen;
  649 
  650         ifp = m->m_pkthdr.rcvif;
  651 
  652         if (m->m_len < sizeof(struct arphdr) &&
  653             ((m = m_pullup(m, sizeof(struct arphdr))) == NULL)) {
  654                 ARP_LOG(LOG_NOTICE, "packet with short header received on %s\n",
  655                     if_name(ifp));
  656                 return;
  657         }
  658         ar = mtod(m, struct arphdr *);
  659 
  660         /* Check if length is sufficient */
  661         if (m->m_len <  arphdr_len(ar)) {
  662                 m = m_pullup(m, arphdr_len(ar));
  663                 if (m == NULL) {
  664                         ARP_LOG(LOG_NOTICE, "short packet received on %s\n",
  665                             if_name(ifp));
  666                         return;
  667                 }
  668                 ar = mtod(m, struct arphdr *);
  669         }
  670 
  671         hlen = 0;
  672         layer = "";
  673         switch (ntohs(ar->ar_hrd)) {
  674         case ARPHRD_ETHER:
  675                 hlen = ETHER_ADDR_LEN; /* RFC 826 */
  676                 layer = "ethernet";
  677                 break;
  678         case ARPHRD_IEEE802:
  679                 hlen = 6; /* RFC 1390, FDDI_ADDR_LEN */
  680                 layer = "fddi";
  681                 break;
  682         case ARPHRD_ARCNET:
  683                 hlen = 1; /* RFC 1201, ARC_ADDR_LEN */
  684                 layer = "arcnet";
  685                 break;
  686         case ARPHRD_INFINIBAND:
  687                 hlen = 20;      /* RFC 4391, INFINIBAND_ALEN */ 
  688                 layer = "infiniband";
  689                 break;
  690         case ARPHRD_IEEE1394:
  691                 hlen = 0; /* SHALL be 16 */ /* RFC 2734 */
  692                 layer = "firewire";
  693 
  694                 /*
  695                  * Restrict too long hardware addresses.
  696                  * Currently we are capable of handling 20-byte
  697                  * addresses ( sizeof(lle->ll_addr) )
  698                  */
  699                 if (ar->ar_hln >= 20)
  700                         hlen = 16;
  701                 break;
  702         default:
  703                 ARP_LOG(LOG_NOTICE,
  704                     "packet with unknown hardware format 0x%02d received on "
  705                     "%s\n", ntohs(ar->ar_hrd), if_name(ifp));
  706                 m_freem(m);
  707                 return;
  708         }
  709 
  710         if (hlen != 0 && hlen != ar->ar_hln) {
  711                 ARP_LOG(LOG_NOTICE,
  712                     "packet with invalid %s address length %d received on %s\n",
  713                     layer, ar->ar_hln, if_name(ifp));
  714                 m_freem(m);
  715                 return;
  716         }
  717 
  718         ARPSTAT_INC(received);
  719         switch (ntohs(ar->ar_pro)) {
  720 #ifdef INET
  721         case ETHERTYPE_IP:
  722                 in_arpinput(m);
  723                 return;
  724 #endif
  725         }
  726         m_freem(m);
  727 }
  728 
  729 #ifdef INET
  730 /*
  731  * ARP for Internet protocols on 10 Mb/s Ethernet.
  732  * Algorithm is that given in RFC 826.
  733  * In addition, a sanity check is performed on the sender
  734  * protocol address, to catch impersonators.
  735  * We no longer handle negotiations for use of trailer protocol:
  736  * Formerly, ARP replied for protocol type ETHERTYPE_TRAIL sent
  737  * along with IP replies if we wanted trailers sent to us,
  738  * and also sent them in response to IP replies.
  739  * This allowed either end to announce the desire to receive
  740  * trailer packets.
  741  * We no longer reply to requests for ETHERTYPE_TRAIL protocol either,
  742  * but formerly didn't normally send requests.
  743  */
  744 static int log_arp_wrong_iface = 1;
  745 static int log_arp_movements = 1;
  746 static int log_arp_permanent_modify = 1;
  747 static int allow_multicast = 0;
  748 
  749 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_wrong_iface, CTLFLAG_RW,
  750         &log_arp_wrong_iface, 0,
  751         "log arp packets arriving on the wrong interface");
  752 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_movements, CTLFLAG_RW,
  753         &log_arp_movements, 0,
  754         "log arp replies from MACs different than the one in the cache");
  755 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_permanent_modify, CTLFLAG_RW,
  756         &log_arp_permanent_modify, 0,
  757         "log arp replies from MACs different than the one in the permanent arp entry");
  758 SYSCTL_INT(_net_link_ether_inet, OID_AUTO, allow_multicast, CTLFLAG_RW,
  759         &allow_multicast, 0, "accept multicast addresses");
  760 
  761 static void
  762 in_arpinput(struct mbuf *m)
  763 {
  764         struct rm_priotracker in_ifa_tracker;
  765         struct arphdr *ah;
  766         struct ifnet *ifp = m->m_pkthdr.rcvif;
  767         struct llentry *la = NULL, *la_tmp;
  768         struct ifaddr *ifa;
  769         struct in_ifaddr *ia;
  770         struct sockaddr sa;
  771         struct in_addr isaddr, itaddr, myaddr;
  772         u_int8_t *enaddr = NULL;
  773         int op;
  774         int bridged = 0, is_bridge = 0;
  775         int carped;
  776         struct sockaddr_in sin;
  777         struct sockaddr *dst;
  778         struct nhop4_basic nh4;
  779         uint8_t linkhdr[LLE_MAX_LINKHDR];
  780         struct route ro;
  781         size_t linkhdrsize;
  782         int lladdr_off;
  783         int error;
  784 
  785         sin.sin_len = sizeof(struct sockaddr_in);
  786         sin.sin_family = AF_INET;
  787         sin.sin_addr.s_addr = 0;
  788 
  789         if (ifp->if_bridge)
  790                 bridged = 1;
  791         if (ifp->if_type == IFT_BRIDGE)
  792                 is_bridge = 1;
  793 
  794         /*
  795          * We already have checked that mbuf contains enough contiguous data
  796          * to hold entire arp message according to the arp header.
  797          */
  798         ah = mtod(m, struct arphdr *);
  799 
  800         /*
  801          * ARP is only for IPv4 so we can reject packets with
  802          * a protocol length not equal to an IPv4 address.
  803          */
  804         if (ah->ar_pln != sizeof(struct in_addr)) {
  805                 ARP_LOG(LOG_NOTICE, "requested protocol length != %zu\n",
  806                     sizeof(struct in_addr));
  807                 goto drop;
  808         }
  809 
  810         if (allow_multicast == 0 && ETHER_IS_MULTICAST(ar_sha(ah))) {
  811                 ARP_LOG(LOG_NOTICE, "%*D is multicast\n",
  812                     ifp->if_addrlen, (u_char *)ar_sha(ah), ":");
  813                 goto drop;
  814         }
  815 
  816         op = ntohs(ah->ar_op);
  817         (void)memcpy(&isaddr, ar_spa(ah), sizeof (isaddr));
  818         (void)memcpy(&itaddr, ar_tpa(ah), sizeof (itaddr));
  819 
  820         if (op == ARPOP_REPLY)
  821                 ARPSTAT_INC(rxreplies);
  822 
  823         /*
  824          * For a bridge, we want to check the address irrespective
  825          * of the receive interface. (This will change slightly
  826          * when we have clusters of interfaces).
  827          */
  828         IN_IFADDR_RLOCK(&in_ifa_tracker);
  829         LIST_FOREACH(ia, INADDR_HASH(itaddr.s_addr), ia_hash) {
  830                 if (((bridged && ia->ia_ifp->if_bridge == ifp->if_bridge) ||
  831                     ia->ia_ifp == ifp) &&
  832                     itaddr.s_addr == ia->ia_addr.sin_addr.s_addr &&
  833                     (ia->ia_ifa.ifa_carp == NULL ||
  834                     (*carp_iamatch_p)(&ia->ia_ifa, &enaddr))) {
  835                         ifa_ref(&ia->ia_ifa);
  836                         IN_IFADDR_RUNLOCK(&in_ifa_tracker);
  837                         goto match;
  838                 }
  839         }
  840         LIST_FOREACH(ia, INADDR_HASH(isaddr.s_addr), ia_hash)
  841                 if (((bridged && ia->ia_ifp->if_bridge == ifp->if_bridge) ||
  842                     ia->ia_ifp == ifp) &&
  843                     isaddr.s_addr == ia->ia_addr.sin_addr.s_addr) {
  844                         ifa_ref(&ia->ia_ifa);
  845                         IN_IFADDR_RUNLOCK(&in_ifa_tracker);
  846                         goto match;
  847                 }
  848 
  849 #define BDG_MEMBER_MATCHES_ARP(addr, ifp, ia)                           \
  850   (ia->ia_ifp->if_bridge == ifp->if_softc &&                            \
  851   !bcmp(IF_LLADDR(ia->ia_ifp), IF_LLADDR(ifp), ifp->if_addrlen) &&      \
  852   addr == ia->ia_addr.sin_addr.s_addr)
  853         /*
  854          * Check the case when bridge shares its MAC address with
  855          * some of its children, so packets are claimed by bridge
  856          * itself (bridge_input() does it first), but they are really
  857          * meant to be destined to the bridge member.
  858          */
  859         if (is_bridge) {
  860                 LIST_FOREACH(ia, INADDR_HASH(itaddr.s_addr), ia_hash) {
  861                         if (BDG_MEMBER_MATCHES_ARP(itaddr.s_addr, ifp, ia)) {
  862                                 ifa_ref(&ia->ia_ifa);
  863                                 ifp = ia->ia_ifp;
  864                                 IN_IFADDR_RUNLOCK(&in_ifa_tracker);
  865                                 goto match;
  866                         }
  867                 }
  868         }
  869 #undef BDG_MEMBER_MATCHES_ARP
  870         IN_IFADDR_RUNLOCK(&in_ifa_tracker);
  871 
  872         /*
  873          * No match, use the first inet address on the receive interface
  874          * as a dummy address for the rest of the function.
  875          */
  876         IF_ADDR_RLOCK(ifp);
  877         TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link)
  878                 if (ifa->ifa_addr->sa_family == AF_INET &&
  879                     (ifa->ifa_carp == NULL ||
  880                     (*carp_iamatch_p)(ifa, &enaddr))) {
  881                         ia = ifatoia(ifa);
  882                         ifa_ref(ifa);
  883                         IF_ADDR_RUNLOCK(ifp);
  884                         goto match;
  885                 }
  886         IF_ADDR_RUNLOCK(ifp);
  887 
  888         /*
  889          * If bridging, fall back to using any inet address.
  890          */
  891         IN_IFADDR_RLOCK(&in_ifa_tracker);
  892         if (!bridged || (ia = TAILQ_FIRST(&V_in_ifaddrhead)) == NULL) {
  893                 IN_IFADDR_RUNLOCK(&in_ifa_tracker);
  894                 goto drop;
  895         }
  896         ifa_ref(&ia->ia_ifa);
  897         IN_IFADDR_RUNLOCK(&in_ifa_tracker);
  898 match:
  899         if (!enaddr)
  900                 enaddr = (u_int8_t *)IF_LLADDR(ifp);
  901         carped = (ia->ia_ifa.ifa_carp != NULL);
  902         myaddr = ia->ia_addr.sin_addr;
  903         ifa_free(&ia->ia_ifa);
  904         if (!bcmp(ar_sha(ah), enaddr, ifp->if_addrlen))
  905                 goto drop;      /* it's from me, ignore it. */
  906         if (!bcmp(ar_sha(ah), ifp->if_broadcastaddr, ifp->if_addrlen)) {
  907                 ARP_LOG(LOG_NOTICE, "link address is broadcast for IP address "
  908                     "%s!\n", inet_ntoa(isaddr));
  909                 goto drop;
  910         }
  911 
  912         if (ifp->if_addrlen != ah->ar_hln) {
  913                 ARP_LOG(LOG_WARNING, "from %*D: addr len: new %d, "
  914                     "i/f %d (ignored)\n", ifp->if_addrlen,
  915                     (u_char *) ar_sha(ah), ":", ah->ar_hln,
  916                     ifp->if_addrlen);
  917                 goto drop;
  918         }
  919 
  920         /*
  921          * Warn if another host is using the same IP address, but only if the
  922          * IP address isn't 0.0.0.0, which is used for DHCP only, in which
  923          * case we suppress the warning to avoid false positive complaints of
  924          * potential misconfiguration.
  925          */
  926         if (!bridged && !carped && isaddr.s_addr == myaddr.s_addr &&
  927             myaddr.s_addr != 0) {
  928                 ARP_LOG(LOG_ERR, "%*D is using my IP address %s on %s!\n",
  929                    ifp->if_addrlen, (u_char *)ar_sha(ah), ":",
  930                    inet_ntoa(isaddr), ifp->if_xname);
  931                 itaddr = myaddr;
  932                 ARPSTAT_INC(dupips);
  933                 goto reply;
  934         }
  935         if (ifp->if_flags & IFF_STATICARP)
  936                 goto reply;
  937 
  938         bzero(&sin, sizeof(sin));
  939         sin.sin_len = sizeof(struct sockaddr_in);
  940         sin.sin_family = AF_INET;
  941         sin.sin_addr = isaddr;
  942         dst = (struct sockaddr *)&sin;
  943         IF_AFDATA_RLOCK(ifp);
  944         la = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
  945         IF_AFDATA_RUNLOCK(ifp);
  946         if (la != NULL)
  947                 arp_check_update_lle(ah, isaddr, ifp, bridged, la);
  948         else if (itaddr.s_addr == myaddr.s_addr) {
  949                 /*
  950                  * Request/reply to our address, but no lle exists yet.
  951                  * Calculate full link prepend to use in lle.
  952                  */
  953                 linkhdrsize = sizeof(linkhdr);
  954                 if (lltable_calc_llheader(ifp, AF_INET, ar_sha(ah), linkhdr,
  955                     &linkhdrsize, &lladdr_off) != 0)
  956                         goto reply;
  957 
  958                 /* Allocate new entry */
  959                 la = lltable_alloc_entry(LLTABLE(ifp), 0, dst);
  960                 if (la == NULL) {
  961 
  962                         /*
  963                          * lle creation may fail if source address belongs
  964                          * to non-directly connected subnet. However, we
  965                          * will try to answer the request instead of dropping
  966                          * frame.
  967                          */
  968                         goto reply;
  969                 }
  970                 lltable_set_entry_addr(ifp, la, linkhdr, linkhdrsize,
  971                     lladdr_off);
  972 
  973                 IF_AFDATA_WLOCK(ifp);
  974                 LLE_WLOCK(la);
  975                 la_tmp = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
  976 
  977                 /*
  978                  * Check if lle still does not exists.
  979                  * If it does, that means that we either
  980                  * 1) have configured it explicitly, via
  981                  * 1a) 'arp -s' static entry or
  982                  * 1b) interface address static record
  983                  * or
  984                  * 2) it was the result of sending first packet to-host
  985                  * or
  986                  * 3) it was another arp reply packet we handled in
  987                  * different thread.
  988                  *
  989                  * In all cases except 3) we definitely need to prefer
  990                  * existing lle. For the sake of simplicity, prefer any
  991                  * existing lle over newly-create one.
  992                  */
  993                 if (la_tmp == NULL)
  994                         lltable_link_entry(LLTABLE(ifp), la);
  995                 IF_AFDATA_WUNLOCK(ifp);
  996 
  997                 if (la_tmp == NULL) {
  998                         arp_mark_lle_reachable(la);
  999                         LLE_WUNLOCK(la);
 1000                 } else {
 1001                         /* Free newly-create entry and handle packet */
 1002                         lltable_free_entry(LLTABLE(ifp), la);
 1003                         la = la_tmp;
 1004                         la_tmp = NULL;
 1005                         arp_check_update_lle(ah, isaddr, ifp, bridged, la);
 1006                         /* arp_check_update_lle() returns @la unlocked */
 1007                 }
 1008                 la = NULL;
 1009         }
 1010 reply:
 1011         if (op != ARPOP_REQUEST)
 1012                 goto drop;
 1013         ARPSTAT_INC(rxrequests);
 1014 
 1015         if (itaddr.s_addr == myaddr.s_addr) {
 1016                 /* Shortcut.. the receiving interface is the target. */
 1017                 (void)memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
 1018                 (void)memcpy(ar_sha(ah), enaddr, ah->ar_hln);
 1019         } else {
 1020                 struct llentry *lle = NULL;
 1021 
 1022                 sin.sin_addr = itaddr;
 1023                 IF_AFDATA_RLOCK(ifp);
 1024                 lle = lla_lookup(LLTABLE(ifp), 0, (struct sockaddr *)&sin);
 1025                 IF_AFDATA_RUNLOCK(ifp);
 1026 
 1027                 if ((lle != NULL) && (lle->la_flags & LLE_PUB)) {
 1028                         (void)memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
 1029                         (void)memcpy(ar_sha(ah), lle->ll_addr, ah->ar_hln);
 1030                         LLE_RUNLOCK(lle);
 1031                 } else {
 1032 
 1033                         if (lle != NULL)
 1034                                 LLE_RUNLOCK(lle);
 1035 
 1036                         if (!V_arp_proxyall)
 1037                                 goto drop;
 1038 
 1039                         /* XXX MRT use table 0 for arp reply  */
 1040                         if (fib4_lookup_nh_basic(0, itaddr, 0, 0, &nh4) != 0)
 1041                                 goto drop;
 1042 
 1043                         /*
 1044                          * Don't send proxies for nodes on the same interface
 1045                          * as this one came out of, or we'll get into a fight
 1046                          * over who claims what Ether address.
 1047                          */
 1048                         if (nh4.nh_ifp == ifp)
 1049                                 goto drop;
 1050 
 1051                         (void)memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
 1052                         (void)memcpy(ar_sha(ah), enaddr, ah->ar_hln);
 1053 
 1054                         /*
 1055                          * Also check that the node which sent the ARP packet
 1056                          * is on the interface we expect it to be on. This
 1057                          * avoids ARP chaos if an interface is connected to the
 1058                          * wrong network.
 1059                          */
 1060 
 1061                         /* XXX MRT use table 0 for arp checks */
 1062                         if (fib4_lookup_nh_basic(0, isaddr, 0, 0, &nh4) != 0)
 1063                                 goto drop;
 1064                         if (nh4.nh_ifp != ifp) {
 1065                                 ARP_LOG(LOG_INFO, "proxy: ignoring request"
 1066                                     " from %s via %s\n",
 1067                                     inet_ntoa(isaddr), ifp->if_xname);
 1068                                 goto drop;
 1069                         }
 1070 
 1071 #ifdef DEBUG_PROXY
 1072                         printf("arp: proxying for %s\n", inet_ntoa(itaddr));
 1073 #endif
 1074                 }
 1075         }
 1076 
 1077         if (itaddr.s_addr == myaddr.s_addr &&
 1078             IN_LINKLOCAL(ntohl(itaddr.s_addr))) {
 1079                 /* RFC 3927 link-local IPv4; always reply by broadcast. */
 1080 #ifdef DEBUG_LINKLOCAL
 1081                 printf("arp: sending reply for link-local addr %s\n",
 1082                     inet_ntoa(itaddr));
 1083 #endif
 1084                 m->m_flags |= M_BCAST;
 1085                 m->m_flags &= ~M_MCAST;
 1086         } else {
 1087                 /* default behaviour; never reply by broadcast. */
 1088                 m->m_flags &= ~(M_BCAST|M_MCAST);
 1089         }
 1090         (void)memcpy(ar_tpa(ah), ar_spa(ah), ah->ar_pln);
 1091         (void)memcpy(ar_spa(ah), &itaddr, ah->ar_pln);
 1092         ah->ar_op = htons(ARPOP_REPLY);
 1093         ah->ar_pro = htons(ETHERTYPE_IP); /* let's be sure! */
 1094         m->m_len = sizeof(*ah) + (2 * ah->ar_pln) + (2 * ah->ar_hln);
 1095         m->m_pkthdr.len = m->m_len;
 1096         m->m_pkthdr.rcvif = NULL;
 1097         sa.sa_family = AF_ARP;
 1098         sa.sa_len = 2;
 1099 
 1100         /* Calculate link header for sending frame */
 1101         bzero(&ro, sizeof(ro));
 1102         linkhdrsize = sizeof(linkhdr);
 1103         error = arp_fillheader(ifp, ah, 0, linkhdr, &linkhdrsize);
 1104 
 1105         /*
 1106          * arp_fillheader() may fail due to lack of support inside encap request
 1107          * routing. This is not necessary an error, AF_ARP can/should be handled
 1108          * by if_output().
 1109          */
 1110         if (error != 0 && error != EAFNOSUPPORT) {
 1111                 ARP_LOG(LOG_ERR, "Failed to calculate ARP header on %s: %d\n",
 1112                     if_name(ifp), error);
 1113                 return;
 1114         }
 1115 
 1116         ro.ro_prepend = linkhdr;
 1117         ro.ro_plen = linkhdrsize;
 1118         ro.ro_flags = 0;
 1119 
 1120         m_clrprotoflags(m);     /* Avoid confusing lower layers. */
 1121         (*ifp->if_output)(ifp, m, &sa, &ro);
 1122         ARPSTAT_INC(txreplies);
 1123         return;
 1124 
 1125 drop:
 1126         m_freem(m);
 1127 }
 1128 #endif
 1129 
 1130 /*
 1131  * Checks received arp data against existing @la.
 1132  * Updates lle state/performs notification if necessary.
 1133  */
 1134 static void
 1135 arp_check_update_lle(struct arphdr *ah, struct in_addr isaddr, struct ifnet *ifp,
 1136     int bridged, struct llentry *la)
 1137 {
 1138         struct sockaddr sa;
 1139         struct mbuf *m_hold, *m_hold_next;
 1140         uint8_t linkhdr[LLE_MAX_LINKHDR];
 1141         size_t linkhdrsize;
 1142         int lladdr_off;
 1143 
 1144         LLE_WLOCK_ASSERT(la);
 1145 
 1146         /* the following is not an error when doing bridging */
 1147         if (!bridged && la->lle_tbl->llt_ifp != ifp) {
 1148                 if (log_arp_wrong_iface)
 1149                         ARP_LOG(LOG_WARNING, "%s is on %s "
 1150                             "but got reply from %*D on %s\n",
 1151                             inet_ntoa(isaddr),
 1152                             la->lle_tbl->llt_ifp->if_xname,
 1153                             ifp->if_addrlen, (u_char *)ar_sha(ah), ":",
 1154                             ifp->if_xname);
 1155                 LLE_WUNLOCK(la);
 1156                 return;
 1157         }
 1158         if ((la->la_flags & LLE_VALID) &&
 1159             bcmp(ar_sha(ah), la->ll_addr, ifp->if_addrlen)) {
 1160                 if (la->la_flags & LLE_STATIC) {
 1161                         LLE_WUNLOCK(la);
 1162                         if (log_arp_permanent_modify)
 1163                                 ARP_LOG(LOG_ERR,
 1164                                     "%*D attempts to modify "
 1165                                     "permanent entry for %s on %s\n",
 1166                                     ifp->if_addrlen,
 1167                                     (u_char *)ar_sha(ah), ":",
 1168                                     inet_ntoa(isaddr), ifp->if_xname);
 1169                         return;
 1170                 }
 1171                 if (log_arp_movements) {
 1172                         ARP_LOG(LOG_INFO, "%s moved from %*D "
 1173                             "to %*D on %s\n",
 1174                             inet_ntoa(isaddr),
 1175                             ifp->if_addrlen,
 1176                             (u_char *)&la->ll_addr, ":",
 1177                             ifp->if_addrlen, (u_char *)ar_sha(ah), ":",
 1178                             ifp->if_xname);
 1179                 }
 1180         }
 1181 
 1182         /* Calculate full link prepend to use in lle */
 1183         linkhdrsize = sizeof(linkhdr);
 1184         if (lltable_calc_llheader(ifp, AF_INET, ar_sha(ah), linkhdr,
 1185             &linkhdrsize, &lladdr_off) != 0)
 1186                 return;
 1187 
 1188         /* Check if something has changed */
 1189         if (memcmp(la->r_linkdata, linkhdr, linkhdrsize) != 0 ||
 1190             (la->la_flags & LLE_VALID) == 0) {
 1191                 /* Try to perform LLE update */
 1192                 if (lltable_try_set_entry_addr(ifp, la, linkhdr, linkhdrsize,
 1193                     lladdr_off) == 0)
 1194                         return;
 1195 
 1196                 /* Clear fast path feedback request if set */
 1197                 la->r_skip_req = 0;
 1198         }
 1199 
 1200         arp_mark_lle_reachable(la);
 1201 
 1202         /*
 1203          * The packets are all freed within the call to the output
 1204          * routine.
 1205          *
 1206          * NB: The lock MUST be released before the call to the
 1207          * output routine.
 1208          */
 1209         if (la->la_hold != NULL) {
 1210                 m_hold = la->la_hold;
 1211                 la->la_hold = NULL;
 1212                 la->la_numheld = 0;
 1213                 lltable_fill_sa_entry(la, &sa);
 1214                 LLE_WUNLOCK(la);
 1215                 for (; m_hold != NULL; m_hold = m_hold_next) {
 1216                         m_hold_next = m_hold->m_nextpkt;
 1217                         m_hold->m_nextpkt = NULL;
 1218                         /* Avoid confusing lower layers. */
 1219                         m_clrprotoflags(m_hold);
 1220                         (*ifp->if_output)(ifp, m_hold, &sa, NULL);
 1221                 }
 1222         } else
 1223                 LLE_WUNLOCK(la);
 1224 }
 1225 
 1226 static void
 1227 arp_mark_lle_reachable(struct llentry *la)
 1228 {
 1229         int canceled, wtime;
 1230 
 1231         LLE_WLOCK_ASSERT(la);
 1232 
 1233         la->ln_state = ARP_LLINFO_REACHABLE;
 1234         EVENTHANDLER_INVOKE(lle_event, la, LLENTRY_RESOLVED);
 1235 
 1236         if (!(la->la_flags & LLE_STATIC)) {
 1237                 LLE_ADDREF(la);
 1238                 la->la_expire = time_uptime + V_arpt_keep;
 1239                 wtime = V_arpt_keep - V_arp_maxtries * V_arpt_rexmit;
 1240                 if (wtime < 0)
 1241                         wtime = V_arpt_keep;
 1242                 canceled = callout_reset(&la->lle_timer,
 1243                     hz * wtime, arptimer, la);
 1244                 if (canceled)
 1245                         LLE_REMREF(la);
 1246         }
 1247         la->la_asked = 0;
 1248         la->la_preempt = V_arp_maxtries;
 1249 }
 1250 
 1251 /*
 1252  * Add pernament link-layer record for given interface address.
 1253  */
 1254 static __noinline void
 1255 arp_add_ifa_lle(struct ifnet *ifp, const struct sockaddr *dst)
 1256 {
 1257         struct llentry *lle, *lle_tmp;
 1258 
 1259         /*
 1260          * Interface address LLE record is considered static
 1261          * because kernel code relies on LLE_STATIC flag to check
 1262          * if these entries can be rewriten by arp updates.
 1263          */
 1264         lle = lltable_alloc_entry(LLTABLE(ifp), LLE_IFADDR | LLE_STATIC, dst);
 1265         if (lle == NULL) {
 1266                 log(LOG_INFO, "arp_ifinit: cannot create arp "
 1267                     "entry for interface address\n");
 1268                 return;
 1269         }
 1270 
 1271         IF_AFDATA_WLOCK(ifp);
 1272         LLE_WLOCK(lle);
 1273         /* Unlink any entry if exists */
 1274         lle_tmp = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
 1275         if (lle_tmp != NULL)
 1276                 lltable_unlink_entry(LLTABLE(ifp), lle_tmp);
 1277 
 1278         lltable_link_entry(LLTABLE(ifp), lle);
 1279         IF_AFDATA_WUNLOCK(ifp);
 1280 
 1281         if (lle_tmp != NULL)
 1282                 EVENTHANDLER_INVOKE(lle_event, lle_tmp, LLENTRY_EXPIRED);
 1283 
 1284         EVENTHANDLER_INVOKE(lle_event, lle, LLENTRY_RESOLVED);
 1285         LLE_WUNLOCK(lle);
 1286         if (lle_tmp != NULL)
 1287                 lltable_free_entry(LLTABLE(ifp), lle_tmp);
 1288 }
 1289 
 1290 void
 1291 arp_ifinit(struct ifnet *ifp, struct ifaddr *ifa)
 1292 {
 1293         const struct sockaddr_in *dst_in;
 1294         const struct sockaddr *dst;
 1295 
 1296         if (ifa->ifa_carp != NULL)
 1297                 return;
 1298 
 1299         dst = ifa->ifa_addr;
 1300         dst_in = (const struct sockaddr_in *)dst;
 1301 
 1302         if (ntohl(dst_in->sin_addr.s_addr) == INADDR_ANY)
 1303                 return;
 1304         arp_announce_ifaddr(ifp, dst_in->sin_addr, IF_LLADDR(ifp));
 1305 
 1306         arp_add_ifa_lle(ifp, dst);
 1307 }
 1308 
 1309 void
 1310 arp_announce_ifaddr(struct ifnet *ifp, struct in_addr addr, u_char *enaddr)
 1311 {
 1312 
 1313         if (ntohl(addr.s_addr) != INADDR_ANY)
 1314                 arprequest(ifp, &addr, &addr, enaddr);
 1315 }
 1316 
 1317 /*
 1318  * Sends gratuitous ARPs for each ifaddr to notify other
 1319  * nodes about the address change.
 1320  */
 1321 static __noinline void
 1322 arp_handle_ifllchange(struct ifnet *ifp)
 1323 {
 1324         struct ifaddr *ifa;
 1325 
 1326         TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
 1327                 if (ifa->ifa_addr->sa_family == AF_INET)
 1328                         arp_ifinit(ifp, ifa);
 1329         }
 1330 }
 1331 
 1332 /*
 1333  * A handler for interface link layer address change event.
 1334  */
 1335 static void
 1336 arp_iflladdr(void *arg __unused, struct ifnet *ifp)
 1337 {
 1338 
 1339         lltable_update_ifaddr(LLTABLE(ifp));
 1340 
 1341         if ((ifp->if_flags & IFF_UP) != 0)
 1342                 arp_handle_ifllchange(ifp);
 1343 }
 1344 
 1345 static void
 1346 vnet_arp_init(void)
 1347 {
 1348 
 1349         if (IS_DEFAULT_VNET(curvnet)) {
 1350                 netisr_register(&arp_nh);
 1351                 iflladdr_tag = EVENTHANDLER_REGISTER(iflladdr_event,
 1352                     arp_iflladdr, NULL, EVENTHANDLER_PRI_ANY);
 1353         }
 1354 #ifdef VIMAGE
 1355         else
 1356                 netisr_register_vnet(&arp_nh);
 1357 #endif
 1358 }
 1359 VNET_SYSINIT(vnet_arp_init, SI_SUB_PROTO_DOMAIN, SI_ORDER_SECOND,
 1360     vnet_arp_init, 0);
 1361 
 1362 #ifdef VIMAGE
 1363 /*
 1364  * We have to unregister ARP along with IP otherwise we risk doing INADDR_HASH
 1365  * lookups after destroying the hash.  Ideally this would go on SI_ORDER_3.5.
 1366  */
 1367 static void
 1368 vnet_arp_destroy(__unused void *arg)
 1369 {
 1370 
 1371         netisr_unregister_vnet(&arp_nh);
 1372 }
 1373 VNET_SYSUNINIT(vnet_arp_uninit, SI_SUB_PROTO_DOMAIN, SI_ORDER_THIRD,
 1374     vnet_arp_destroy, NULL);
 1375 #endif

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