bsd/netinet6/udp6_output.c

   1 /*
   2  * Copyright (c) 2000-2016 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29
  30 /*      $FreeBSD: src/sys/netinet6/udp6_output.c,v 1.1.2.3 2001/08/31 13:49:58 jlemon Exp $     */
  31 /*      $KAME: udp6_output.c,v 1.31 2001/05/21 16:39:15 jinmei Exp $    */
  32
  33 /*
  34  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
  35  * All rights reserved.
  36  *
  37  * Redistribution and use in source and binary forms, with or without
  38  * modification, are permitted provided that the following conditions
  39  * are met:
  40  * 1. Redistributions of source code must retain the above copyright
  41  *    notice, this list of conditions and the following disclaimer.
  42  * 2. Redistributions in binary form must reproduce the above copyright
  43  *    notice, this list of conditions and the following disclaimer in the
  44  *    documentation and/or other materials provided with the distribution.
  45  * 3. Neither the name of the project nor the names of its contributors
  46  *    may be used to endorse or promote products derived from this software
  47  *    without specific prior written permission.
  48  *
  49  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
  50  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  51  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  52  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
  53  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  54  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  55  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  56  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  57  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  58  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  59  * SUCH DAMAGE.
  60  */
  61
  62 /*
  63  * Copyright (c) 1982, 1986, 1989, 1993
  64  *      The Regents of the University of California.  All rights reserved.
  65  *
  66  * Redistribution and use in source and binary forms, with or without
  67  * modification, are permitted provided that the following conditions
  68  * are met:
  69  * 1. Redistributions of source code must retain the above copyright
  70  *    notice, this list of conditions and the following disclaimer.
  71  * 2. Redistributions in binary form must reproduce the above copyright
  72  *    notice, this list of conditions and the following disclaimer in the
  73  *    documentation and/or other materials provided with the distribution.
  74  * 3. All advertising materials mentioning features or use of this software
  75  *    must display the following acknowledgement:
  76  *      This product includes software developed by the University of
  77  *      California, Berkeley and its contributors.
  78  * 4. Neither the name of the University nor the names of its contributors
  79  *    may be used to endorse or promote products derived from this software
  80  *    without specific prior written permission.
  81  *
  82  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  83  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  84  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  85  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  86  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  87  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  88  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  89  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  90  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  91  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  92  * SUCH DAMAGE.
  93  *
  94  *      @(#)udp_var.h   8.1 (Berkeley) 6/10/93
  95  */
  96
  97 #include <sys/param.h>
  98 #include <sys/malloc.h>
  99 #include <sys/mbuf.h>
 100 #include <sys/protosw.h>
 101 #include <sys/socket.h>
 102 #include <sys/socketvar.h>
 103 #include <sys/sysctl.h>
 104 #include <sys/errno.h>
 105 #include <sys/stat.h>
 106 #include <sys/systm.h>
 107 #include <sys/proc.h>
 108 #include <sys/syslog.h>
 109
 110 #include <machine/endian.h>
 111
 112 #include <net/if.h>
 113 #include <net/route.h>
 114 #include <net/if_types.h>
 115 #include <net/ntstat.h>
 116
 117 #include <netinet/in.h>
 118 #include <netinet/in_var.h>
 119 #include <netinet/in_systm.h>
 120 #include <netinet/in_tclass.h>
 121 #include <netinet/ip.h>
 122 #include <netinet/ip_var.h>
 123 #include <netinet/in_pcb.h>
 124 #include <netinet/udp.h>
 125 #include <netinet/udp_var.h>
 126 #include <netinet/ip6.h>
 127 #include <netinet6/ip6_var.h>
 128 #include <netinet6/in6_pcb.h>
 129 #include <netinet6/udp6_var.h>
 130 #include <netinet/icmp6.h>
 131 #include <netinet6/ip6protosw.h>
 132
 133 #if NECP
 134 #include <net/necp.h>
 135 #endif /* NECP */
 136
 137 #include <net/net_osdep.h>
 138
 139 /*
 140  * UDP protocol inplementation.
 141  * Per RFC 768, August, 1980.
 142  */
 143 extern int soreserveheadroom;
 144
 145 int
 146 udp6_output(struct in6pcb *in6p, struct mbuf *m, struct sockaddr *addr6,
 147     struct mbuf *control, struct proc *p)
 148 {
 149         u_int32_t ulen = m->m_pkthdr.len;
 150         u_int32_t plen = sizeof (struct udphdr) + ulen;
 151         struct ip6_hdr *ip6;
 152         struct udphdr *udp6;
 153         struct in6_addr *laddr, *faddr;
 154         u_short fport;
 155         int error = 0;
 156         struct ip6_pktopts opt, *optp = NULL;
 157         struct ip6_moptions *im6o;
 158         int af = AF_INET6, hlen = sizeof (struct ip6_hdr);
 159         int flags;
 160         struct sockaddr_in6 tmp;
 161         struct  in6_addr storage;
 162         int sotc = SO_TC_UNSPEC;
 163         int netsvctype = _NET_SERVICE_TYPE_UNSPEC;
 164         struct ip6_out_args ip6oa =
 165             { IFSCOPE_NONE, { 0 }, IP6OAF_SELECT_SRCIF, 0, 0, 0 };
 166         struct flowadv *adv = &ip6oa.ip6oa_flowadv;
 167         struct socket *so = in6p->in6p_socket;
 168         struct route_in6 ro;
 169         int flowadv = 0;
 170
 171         /* Enable flow advisory only when connected */
 172         flowadv = (so->so_state & SS_ISCONNECTED) ? 1 : 0;
 173
 174         if (flowadv && INP_WAIT_FOR_IF_FEEDBACK(in6p)) {
 175                 error = ENOBUFS;
 176                 goto release;
 177         }
 178
 179         if (in6p->inp_flags & INP_BOUND_IF) {
 180                 ip6oa.ip6oa_boundif = in6p->inp_boundifp->if_index;
 181                 ip6oa.ip6oa_flags |= IP6OAF_BOUND_IF;
 182         }
 183         if (INP_NO_CELLULAR(in6p))
 184                 ip6oa.ip6oa_flags |= IP6OAF_NO_CELLULAR;
 185         if (INP_NO_EXPENSIVE(in6p))
 186                 ip6oa.ip6oa_flags |= IP6OAF_NO_EXPENSIVE;
 187         if (INP_AWDL_UNRESTRICTED(in6p))
 188                 ip6oa.ip6oa_flags |= IP6OAF_AWDL_UNRESTRICTED;
 189         if (INP_INTCOPROC_ALLOWED(in6p))
 190                 ip6oa.ip6oa_flags |= IP6OAF_INTCOPROC_ALLOWED;
 191
 192         if (control) {
 193                 sotc = so_tc_from_control(control, &netsvctype);
 194                 if ((error = ip6_setpktopts(control, &opt,
 195                     NULL, IPPROTO_UDP)) != 0)
 196                         goto release;
 197                 optp = &opt;
 198         } else
 199                 optp = in6p->in6p_outputopts;
 200
 201         if (sotc == SO_TC_UNSPEC) {
 202                 sotc = so->so_traffic_class;
 203                 netsvctype = so->so_netsvctype;
 204         }
 205         ip6oa.ip6oa_sotc = sotc;
 206         ip6oa.ip6oa_netsvctype = netsvctype;
 207
 208         if (addr6) {
 209                 /*
 210                  * IPv4 version of udp_output calls in_pcbconnect in this case,
 211                  * which has its costs.
 212                  *
 213                  * Since we saw no essential reason for calling in_pcbconnect,
 214                  * we get rid of such kind of logic, and call in6_selectsrc
 215                  * and in6_pcbsetport in order to fill in the local address
 216                  * and the local port.
 217                  */
 218                 struct sockaddr_in6 *sin6 =
 219                     (struct sockaddr_in6 *)(void *)addr6;
 220
 221                 if (sin6->sin6_port == 0) {
 222                         error = EADDRNOTAVAIL;
 223                         goto release;
 224                 }
 225
 226                 if (!IN6_IS_ADDR_UNSPECIFIED(&in6p->in6p_faddr)) {
 227                         /* how about ::ffff:0.0.0.0 case? */
 228                         error = EISCONN;
 229                         goto release;
 230                 }
 231
 232                 /* protect *sin6 from overwrites */
 233                 tmp = *sin6;
 234                 sin6 = &tmp;
 235
 236                 faddr = &sin6->sin6_addr;
 237                 fport = sin6->sin6_port; /* allow 0 port */
 238
 239                 if (IN6_IS_ADDR_V4MAPPED(faddr)) {
 240                         if ((in6p->in6p_flags & IN6P_IPV6_V6ONLY)) {
 241                                 /*
 242                                  * I believe we should explicitly discard the
 243                                  * packet when mapped addresses are disabled,
 244                                  * rather than send the packet as an IPv6 one.
 245                                  * If we chose the latter approach, the packet
 246                                  * might be sent out on the wire based on the
 247                                  * default route, the situation which we'd
 248                                  * probably want to avoid.
 249                                  * (20010421 jinmei@kame.net)
 250                                  */
 251                                 error = EINVAL;
 252                                 goto release;
 253                         } else {
 254                                 af = AF_INET;
 255                         }
 256                 }
 257
 258                 /* KAME hack: embed scopeid */
 259                 if (in6_embedscope(&sin6->sin6_addr, sin6, in6p, NULL,
 260                     optp) != 0) {
 261                         error = EINVAL;
 262                         goto release;
 263                 }
 264
 265                 if (!IN6_IS_ADDR_V4MAPPED(faddr)) {
 266                         laddr = in6_selectsrc(sin6, optp,
 267                             in6p, &in6p->in6p_route, NULL, &storage,
 268                             ip6oa.ip6oa_boundif, &error);
 269                 } else
 270                         laddr = &in6p->in6p_laddr;      /* XXX */
 271                 if (laddr == NULL) {
 272                         if (error == 0)
 273                                 error = EADDRNOTAVAIL;
 274                         goto release;
 275                 }
 276                 if (in6p->in6p_lport == 0 &&
 277                     (error = in6_pcbsetport(laddr, in6p, p, 0)) != 0)
 278                         goto release;
 279         } else {
 280                 if (IN6_IS_ADDR_UNSPECIFIED(&in6p->in6p_faddr)) {
 281                         error = ENOTCONN;
 282                         goto release;
 283                 }
 284                 if (IN6_IS_ADDR_V4MAPPED(&in6p->in6p_faddr)) {
 285                         if ((in6p->in6p_flags & IN6P_IPV6_V6ONLY)) {
 286                                 /*
 287                                  * XXX: this case would happen when the
 288                                  * application sets the V6ONLY flag after
 289                                  * connecting the foreign address.
 290                                  * Such applications should be fixed,
 291                                  * so we bark here.
 292                                  */
 293                                 log(LOG_INFO, "udp6_output: IPV6_V6ONLY "
 294                                     "option was set for a connected socket\n");
 295                                 error = EINVAL;
 296                                 goto release;
 297                         } else
 298                                 af = AF_INET;
 299                 }
 300                 laddr = &in6p->in6p_laddr;
 301                 faddr = &in6p->in6p_faddr;
 302                 fport = in6p->in6p_fport;
 303         }
 304
 305         if (in6p->inp_flowhash == 0)
 306                 in6p->inp_flowhash = inp_calc_flowhash(in6p);
 307         /* update flowinfo - RFC 6437 */
 308         if (in6p->inp_flow == 0 && in6p->in6p_flags & IN6P_AUTOFLOWLABEL) {
 309                 in6p->inp_flow &= ~IPV6_FLOWLABEL_MASK;
 310                 in6p->inp_flow |=
 311                     (htonl(in6p->inp_flowhash) & IPV6_FLOWLABEL_MASK);
 312         }
 313
 314         if (af == AF_INET)
 315                 hlen = sizeof (struct ip);
 316
 317         /*
 318          * Calculate data length and get a mbuf
 319          * for UDP and IP6 headers.
 320          */
 321         M_PREPEND(m, hlen + sizeof (struct udphdr), M_DONTWAIT, 1);
 322         if (m == 0) {
 323                 error = ENOBUFS;
 324                 goto release;
 325         }
 326
 327         /*
 328          * Stuff checksum and output datagram.
 329          */
 330         udp6 = (struct udphdr *)(void *)(mtod(m, caddr_t) + hlen);
 331         udp6->uh_sport = in6p->in6p_lport; /* lport is always set in the PCB */
 332         udp6->uh_dport = fport;
 333         if (plen <= 0xffff)
 334                 udp6->uh_ulen = htons((u_short)plen);
 335         else
 336                 udp6->uh_ulen = 0;
 337         udp6->uh_sum = 0;
 338
 339         switch (af) {
 340         case AF_INET6:
 341                 ip6 = mtod(m, struct ip6_hdr *);
 342                 ip6->ip6_flow   = in6p->inp_flow & IPV6_FLOWINFO_MASK;
 343                 ip6->ip6_vfc    &= ~IPV6_VERSION_MASK;
 344                 ip6->ip6_vfc    |= IPV6_VERSION;
 345 #if 0           /* ip6_plen will be filled in ip6_output. */
 346                 ip6->ip6_plen   = htons((u_short)plen);
 347 #endif
 348                 ip6->ip6_nxt    = IPPROTO_UDP;
 349                 ip6->ip6_hlim   = in6_selecthlim(in6p, in6p->in6p_route.ro_rt ?
 350                     in6p->in6p_route.ro_rt->rt_ifp : NULL);
 351                 ip6->ip6_src    = *laddr;
 352                 ip6->ip6_dst    = *faddr;
 353
 354                 udp6->uh_sum = in6_pseudo(laddr, faddr,
 355                     htonl(plen + IPPROTO_UDP));
 356                 m->m_pkthdr.csum_flags = CSUM_UDPIPV6;
 357                 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
 358
 359                 if (!IN6_IS_ADDR_UNSPECIFIED(laddr))
 360                         ip6oa.ip6oa_flags |= IP6OAF_BOUND_SRCADDR;
 361
 362                 flags = IPV6_OUTARGS;
 363
 364                 udp6stat.udp6s_opackets++;
 365
 366 #if NECP
 367                 {
 368                         necp_kernel_policy_id policy_id;
 369                         u_int32_t route_rule_id;
 370
 371                         /*
 372                          * We need a route to perform NECP route rule checks
 373                          */
 374                         if (net_qos_policy_restricted != 0 &&
 375                             ROUTE_UNUSABLE(&in6p->inp_route)) {
 376                                 struct sockaddr_in6 to;
 377                                 struct sockaddr_in6 from;
 378
 379                                 ROUTE_RELEASE(&in6p->inp_route);
 380
 381                                 bzero(&from, sizeof(struct sockaddr_in6));
 382                                 from.sin6_family = AF_INET6;
 383                                 from.sin6_len = sizeof(struct sockaddr_in6);
 384                                 from.sin6_addr = *laddr;
 385
 386                                 bzero(&to, sizeof(struct sockaddr_in6));
 387                                 to.sin6_family = AF_INET6;
 388                                 to.sin6_len = sizeof(struct sockaddr_in6);
 389                                 to.sin6_addr = *faddr;
 390
 391                                 in6p->inp_route.ro_dst.sa_family = AF_INET6;
 392                                 in6p->inp_route.ro_dst.sa_len = sizeof(struct sockaddr_in6);
 393                                 ((struct sockaddr_in6 *)(void *)&in6p->inp_route.ro_dst)->sin6_addr =
 394                                         *faddr;
 395
 396                                 rtalloc_scoped(&in6p->inp_route, ip6oa.ip6oa_boundif);
 397
 398                                 inp_update_necp_policy(in6p, (struct sockaddr *)&from,
 399                                     (struct sockaddr *)&to, ip6oa.ip6oa_boundif);
 400                                 in6p->inp_policyresult.results.qos_marking_gencount = 0;
 401                         }
 402
 403                         if (!necp_socket_is_allowed_to_send_recv_v6(in6p, in6p->in6p_lport, fport, laddr, faddr, NULL, &policy_id, &route_rule_id)) {
 404                                 error = EHOSTUNREACH;
 405                                 goto release;
 406                         }
 407
 408                         necp_mark_packet_from_socket(m, in6p, policy_id, route_rule_id);
 409
 410                         if (net_qos_policy_restricted != 0) {
 411                                 necp_socket_update_qos_marking(in6p, in6p->in6p_route.ro_rt,
 412                                     NULL, route_rule_id);
 413                         }
 414                 }
 415 #endif /* NECP */
 416                 if ((so->so_flags1 & SOF1_QOSMARKING_ALLOWED))
 417                         ip6oa.ip6oa_flags |= IP6OAF_QOSMARKING_ALLOWED;
 418
 419 #if IPSEC
 420                 if (in6p->in6p_sp != NULL && ipsec_setsocket(m, so) != 0) {
 421                         error = ENOBUFS;
 422                         goto release;
 423                 }
 424 #endif /*IPSEC*/
 425
 426                 /* In case of IPv4-mapped address used in previous send */
 427                 if (ROUTE_UNUSABLE(&in6p->in6p_route) ||
 428                     rt_key(in6p->in6p_route.ro_rt)->sa_family != AF_INET6)
 429                         ROUTE_RELEASE(&in6p->in6p_route);
 430
 431                 /* Copy the cached route and take an extra reference */
 432                 in6p_route_copyout(in6p, &ro);
 433
 434                 set_packet_service_class(m, so, sotc, PKT_SCF_IPV6);
 435
 436                 m->m_pkthdr.pkt_flowsrc = FLOWSRC_INPCB;
 437                 m->m_pkthdr.pkt_flowid = in6p->inp_flowhash;
 438                 m->m_pkthdr.pkt_proto = IPPROTO_UDP;
 439                 m->m_pkthdr.pkt_flags |= (PKTF_FLOW_ID | PKTF_FLOW_LOCALSRC);
 440                 if (flowadv)
 441                         m->m_pkthdr.pkt_flags |= PKTF_FLOW_ADV;
 442
 443                 im6o = in6p->in6p_moptions;
 444                 if (im6o != NULL) {
 445                         IM6O_LOCK(im6o);
 446                         IM6O_ADDREF_LOCKED(im6o);
 447                         if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) &&
 448                             im6o->im6o_multicast_ifp != NULL) {
 449                                 in6p->in6p_last_outifp =
 450                                     im6o->im6o_multicast_ifp;
 451                         }
 452                         IM6O_UNLOCK(im6o);
 453                 }
 454
 455                 in6p->inp_sndinprog_cnt++;
 456
 457                 socket_unlock(so, 0);
 458                 error = ip6_output(m, optp, &ro, flags, im6o, NULL, &ip6oa);
 459                 m = NULL;
 460                 socket_lock(so, 0);
 461
 462                 if (im6o != NULL)
 463                         IM6O_REMREF(im6o);
 464
 465                 if (error == 0 && nstat_collect) {
 466                         boolean_t cell, wifi, wired;
 467
 468                         if (in6p->in6p_route.ro_rt != NULL) {
 469                                 cell = IFNET_IS_CELLULAR(in6p->in6p_route.
 470                                     ro_rt->rt_ifp);
 471                                 wifi = (!cell && IFNET_IS_WIFI(in6p->in6p_route.
 472                                     ro_rt->rt_ifp));
 473                                 wired = (!wifi && IFNET_IS_WIRED(in6p->in6p_route.
 474                                     ro_rt->rt_ifp));
 475                         } else {
 476                                 cell = wifi = wired = FALSE;
 477                         }
 478                         INP_ADD_STAT(in6p, cell, wifi, wired, txpackets, 1);
 479                         INP_ADD_STAT(in6p, cell, wifi, wired, txbytes, ulen);
 480                 }
 481
 482                 if (flowadv && (adv->code == FADV_FLOW_CONTROLLED ||
 483                     adv->code == FADV_SUSPENDED)) {
 484                         /*
 485                          * Return an error to indicate
 486                          * that the packet has been dropped.
 487                          */
 488                         error = ENOBUFS;
 489                         inp_set_fc_state(in6p, adv->code);
 490                 }
 491
 492                 VERIFY(in6p->inp_sndinprog_cnt > 0);
 493                 if ( --in6p->inp_sndinprog_cnt == 0)
 494                         in6p->inp_flags &= ~(INP_FC_FEEDBACK);
 495
 496                 if (ro.ro_rt != NULL) {
 497                         struct ifnet *outif = ro.ro_rt->rt_ifp;
 498
 499                         so->so_pktheadroom = P2ROUNDUP(
 500                             sizeof(struct udphdr) +
 501                             hlen +
 502                             ifnet_hdrlen(outif) +
 503                             ifnet_packetpreamblelen(outif),
 504                             sizeof(u_int32_t));
 505                 }
 506
 507                 /* Synchronize PCB cached route */
 508                 in6p_route_copyin(in6p, &ro);
 509
 510                 if (in6p->in6p_route.ro_rt != NULL) {
 511                         struct rtentry *rt = in6p->in6p_route.ro_rt;
 512                         struct ifnet *outif;
 513
 514                         if (rt->rt_flags & RTF_MULTICAST)
 515                                 rt = NULL;      /* unusable */
 516
 517                         /*
 518                          * Always discard the cached route for unconnected
 519                          * socket or if it is a multicast route.
 520                          */
 521                         if (rt == NULL)
 522                                 ROUTE_RELEASE(&in6p->in6p_route);
 523
 524                         /*
 525                          * If the destination route is unicast, update outif
 526                          * with that of the route interface used by IP.
 527                          */
 528                         if (rt != NULL &&
 529                             (outif = rt->rt_ifp) != in6p->in6p_last_outifp) {
 530                                 in6p->in6p_last_outifp = outif;
 531
 532                                 so->so_pktheadroom = P2ROUNDUP(
 533                                     sizeof(struct udphdr) +
 534                                     hlen +
 535                                     ifnet_hdrlen(outif) +
 536                                     ifnet_packetpreamblelen(outif),
 537                                     sizeof(u_int32_t));
 538                         }
 539                 } else {
 540                         ROUTE_RELEASE(&in6p->in6p_route);
 541                 }
 542
 543                 /*
 544                  * If output interface was cellular/expensive, and this
 545                  * socket is denied access to it, generate an event.
 546                  */
 547                 if (error != 0 && (ip6oa.ip6oa_retflags & IP6OARF_IFDENIED) &&
 548                     (INP_NO_CELLULAR(in6p) || INP_NO_EXPENSIVE(in6p)))
 549                         soevent(in6p->inp_socket, (SO_FILT_HINT_LOCKED|
 550                             SO_FILT_HINT_IFDENIED));
 551                 break;
 552         case AF_INET:
 553                 error = EAFNOSUPPORT;
 554                 goto release;
 555         }
 556         goto releaseopt;
 557
 558 release:
 559         if (m != NULL)
 560                 m_freem(m);
 561
 562 releaseopt:
 563         if (control != NULL) {
 564                 if (optp == &opt)
 565                         ip6_clearpktopts(optp, -1);
 566                 m_freem(control);
 567         }
 568         return (error);
 569 }