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

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    1 /*
    2  * Copyright (c) 1982, 1986, 1988, 1993
    3  *      The Regents of the University of California.
    4  * Copyright (c) 2005 Andre Oppermann, Internet Business Solutions AG.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 4. Neither the name of the University nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD: releng/10.0/sys/netinet/ip_options.c 248373 2013-03-16 08:58:28Z glebius $");
   34 
   35 #include "opt_ipstealth.h"
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/mbuf.h>
   40 #include <sys/domain.h>
   41 #include <sys/protosw.h>
   42 #include <sys/socket.h>
   43 #include <sys/time.h>
   44 #include <sys/kernel.h>
   45 #include <sys/syslog.h>
   46 #include <sys/sysctl.h>
   47 
   48 #include <net/if.h>
   49 #include <net/if_types.h>
   50 #include <net/if_var.h>
   51 #include <net/if_dl.h>
   52 #include <net/route.h>
   53 #include <net/netisr.h>
   54 #include <net/vnet.h>
   55 
   56 #include <netinet/in.h>
   57 #include <netinet/in_systm.h>
   58 #include <netinet/in_var.h>
   59 #include <netinet/ip.h>
   60 #include <netinet/in_pcb.h>
   61 #include <netinet/ip_var.h>
   62 #include <netinet/ip_options.h>
   63 #include <netinet/ip_icmp.h>
   64 #include <machine/in_cksum.h>
   65 
   66 #include <sys/socketvar.h>
   67 
   68 static int      ip_dosourceroute = 0;
   69 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, CTLFLAG_RW,
   70     &ip_dosourceroute, 0, "Enable forwarding source routed IP packets");
   71 
   72 static int      ip_acceptsourceroute = 0;
   73 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute, 
   74     CTLFLAG_RW, &ip_acceptsourceroute, 0, 
   75     "Enable accepting source routed IP packets");
   76 
   77 int             ip_doopts = 1;  /* 0 = ignore, 1 = process, 2 = reject */
   78 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_RW,
   79     &ip_doopts, 0, "Enable IP options processing ([LS]SRR, RR, TS)");
   80 
   81 static void     save_rte(struct mbuf *m, u_char *, struct in_addr);
   82 
   83 /*
   84  * Do option processing on a datagram, possibly discarding it if bad options
   85  * are encountered, or forwarding it if source-routed.
   86  *
   87  * The pass argument is used when operating in the IPSTEALTH mode to tell
   88  * what options to process: [LS]SRR (pass 0) or the others (pass 1).  The
   89  * reason for as many as two passes is that when doing IPSTEALTH, non-routing
   90  * options should be processed only if the packet is for us.
   91  *
   92  * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
   93  * processed further.
   94  */
   95 int
   96 ip_dooptions(struct mbuf *m, int pass)
   97 {
   98         struct ip *ip = mtod(m, struct ip *);
   99         u_char *cp;
  100         struct in_ifaddr *ia;
  101         int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
  102         struct in_addr *sin, dst;
  103         uint32_t ntime;
  104         struct  sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
  105 
  106         /* Ignore or reject packets with IP options. */
  107         if (ip_doopts == 0)
  108                 return 0;
  109         else if (ip_doopts == 2) {
  110                 type = ICMP_UNREACH;
  111                 code = ICMP_UNREACH_FILTER_PROHIB;
  112                 goto bad;
  113         }
  114 
  115         dst = ip->ip_dst;
  116         cp = (u_char *)(ip + 1);
  117         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  118         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  119                 opt = cp[IPOPT_OPTVAL];
  120                 if (opt == IPOPT_EOL)
  121                         break;
  122                 if (opt == IPOPT_NOP)
  123                         optlen = 1;
  124                 else {
  125                         if (cnt < IPOPT_OLEN + sizeof(*cp)) {
  126                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  127                                 goto bad;
  128                         }
  129                         optlen = cp[IPOPT_OLEN];
  130                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
  131                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  132                                 goto bad;
  133                         }
  134                 }
  135                 switch (opt) {
  136 
  137                 default:
  138                         break;
  139 
  140                 /*
  141                  * Source routing with record.  Find interface with current
  142                  * destination address.  If none on this machine then drop if
  143                  * strictly routed, or do nothing if loosely routed.  Record
  144                  * interface address and bring up next address component.  If
  145                  * strictly routed make sure next address is on directly
  146                  * accessible net.
  147                  */
  148                 case IPOPT_LSRR:
  149                 case IPOPT_SSRR:
  150 #ifdef IPSTEALTH
  151                         if (V_ipstealth && pass > 0)
  152                                 break;
  153 #endif
  154                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
  155                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  156                                 goto bad;
  157                         }
  158                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  159                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  160                                 goto bad;
  161                         }
  162                         ipaddr.sin_addr = ip->ip_dst;
  163                         if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
  164                             == 0) {
  165                                 if (opt == IPOPT_SSRR) {
  166                                         type = ICMP_UNREACH;
  167                                         code = ICMP_UNREACH_SRCFAIL;
  168                                         goto bad;
  169                                 }
  170                                 if (!ip_dosourceroute)
  171                                         goto nosourcerouting;
  172                                 /*
  173                                  * Loose routing, and not at next destination
  174                                  * yet; nothing to do except forward.
  175                                  */
  176                                 break;
  177                         }
  178                         off--;                  /* 0 origin */
  179                         if (off > optlen - (int)sizeof(struct in_addr)) {
  180                                 /*
  181                                  * End of source route.  Should be for us.
  182                                  */
  183                                 if (!ip_acceptsourceroute)
  184                                         goto nosourcerouting;
  185                                 save_rte(m, cp, ip->ip_src);
  186                                 break;
  187                         }
  188 #ifdef IPSTEALTH
  189                         if (V_ipstealth)
  190                                 goto dropit;
  191 #endif
  192                         if (!ip_dosourceroute) {
  193                                 if (V_ipforwarding) {
  194                                         char buf[16]; /* aaa.bbb.ccc.ddd\0 */
  195                                         /*
  196                                          * Acting as a router, so generate
  197                                          * ICMP
  198                                          */
  199 nosourcerouting:
  200                                         strcpy(buf, inet_ntoa(ip->ip_dst));
  201                                         log(LOG_WARNING, 
  202                                             "attempted source route from %s to %s\n",
  203                                             inet_ntoa(ip->ip_src), buf);
  204                                         type = ICMP_UNREACH;
  205                                         code = ICMP_UNREACH_SRCFAIL;
  206                                         goto bad;
  207                                 } else {
  208                                         /*
  209                                          * Not acting as a router, so
  210                                          * silently drop.
  211                                          */
  212 #ifdef IPSTEALTH
  213 dropit:
  214 #endif
  215                                         IPSTAT_INC(ips_cantforward);
  216                                         m_freem(m);
  217                                         return (1);
  218                                 }
  219                         }
  220 
  221                         /*
  222                          * locate outgoing interface
  223                          */
  224                         (void)memcpy(&ipaddr.sin_addr, cp + off,
  225                             sizeof(ipaddr.sin_addr));
  226 
  227                         if (opt == IPOPT_SSRR) {
  228 #define INA     struct in_ifaddr *
  229 #define SA      struct sockaddr *
  230                             if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == NULL)
  231                                     ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0);
  232                         } else
  233 /* XXX MRT 0 for routing */
  234                                 ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m));
  235                         if (ia == NULL) {
  236                                 type = ICMP_UNREACH;
  237                                 code = ICMP_UNREACH_SRCFAIL;
  238                                 goto bad;
  239                         }
  240                         ip->ip_dst = ipaddr.sin_addr;
  241                         (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  242                             sizeof(struct in_addr));
  243                         ifa_free(&ia->ia_ifa);
  244                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  245                         /*
  246                          * Let ip_intr's mcast routing check handle mcast pkts
  247                          */
  248                         forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
  249                         break;
  250 
  251                 case IPOPT_RR:
  252 #ifdef IPSTEALTH
  253                         if (V_ipstealth && pass == 0)
  254                                 break;
  255 #endif
  256                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
  257                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  258                                 goto bad;
  259                         }
  260                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  261                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  262                                 goto bad;
  263                         }
  264                         /*
  265                          * If no space remains, ignore.
  266                          */
  267                         off--;                  /* 0 origin */
  268                         if (off > optlen - (int)sizeof(struct in_addr))
  269                                 break;
  270                         (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
  271                             sizeof(ipaddr.sin_addr));
  272                         /*
  273                          * Locate outgoing interface; if we're the
  274                          * destination, use the incoming interface (should be
  275                          * same).
  276                          */
  277                         if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == NULL &&
  278                             (ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m))) == NULL) {
  279                                 type = ICMP_UNREACH;
  280                                 code = ICMP_UNREACH_HOST;
  281                                 goto bad;
  282                         }
  283                         (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  284                             sizeof(struct in_addr));
  285                         ifa_free(&ia->ia_ifa);
  286                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  287                         break;
  288 
  289                 case IPOPT_TS:
  290 #ifdef IPSTEALTH
  291                         if (V_ipstealth && pass == 0)
  292                                 break;
  293 #endif
  294                         code = cp - (u_char *)ip;
  295                         if (optlen < 4 || optlen > 40) {
  296                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  297                                 goto bad;
  298                         }
  299                         if ((off = cp[IPOPT_OFFSET]) < 5) {
  300                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  301                                 goto bad;
  302                         }
  303                         if (off > optlen - (int)sizeof(int32_t)) {
  304                                 cp[IPOPT_OFFSET + 1] += (1 << 4);
  305                                 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
  306                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  307                                         goto bad;
  308                                 }
  309                                 break;
  310                         }
  311                         off--;                          /* 0 origin */
  312                         sin = (struct in_addr *)(cp + off);
  313                         switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
  314 
  315                         case IPOPT_TS_TSONLY:
  316                                 break;
  317 
  318                         case IPOPT_TS_TSANDADDR:
  319                                 if (off + sizeof(uint32_t) +
  320                                     sizeof(struct in_addr) > optlen) {
  321                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  322                                         goto bad;
  323                                 }
  324                                 ipaddr.sin_addr = dst;
  325                                 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
  326                                                             m->m_pkthdr.rcvif);
  327                                 if (ia == NULL)
  328                                         continue;
  329                                 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
  330                                     sizeof(struct in_addr));
  331                                 ifa_free(&ia->ia_ifa);
  332                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  333                                 off += sizeof(struct in_addr);
  334                                 break;
  335 
  336                         case IPOPT_TS_PRESPEC:
  337                                 if (off + sizeof(uint32_t) +
  338                                     sizeof(struct in_addr) > optlen) {
  339                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  340                                         goto bad;
  341                                 }
  342                                 (void)memcpy(&ipaddr.sin_addr, sin,
  343                                     sizeof(struct in_addr));
  344                                 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
  345                                         continue;
  346                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  347                                 off += sizeof(struct in_addr);
  348                                 break;
  349 
  350                         default:
  351                                 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
  352                                 goto bad;
  353                         }
  354                         ntime = iptime();
  355                         (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
  356                         cp[IPOPT_OFFSET] += sizeof(uint32_t);
  357                 }
  358         }
  359         if (forward && V_ipforwarding) {
  360                 ip_forward(m, 1);
  361                 return (1);
  362         }
  363         return (0);
  364 bad:
  365         icmp_error(m, type, code, 0, 0);
  366         IPSTAT_INC(ips_badoptions);
  367         return (1);
  368 }
  369 
  370 /*
  371  * Save incoming source route for use in replies, to be picked up later by
  372  * ip_srcroute if the receiver is interested.
  373  */
  374 static void
  375 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
  376 {
  377         unsigned olen;
  378         struct ipopt_tag *opts;
  379 
  380         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
  381             sizeof(struct ipopt_tag), M_NOWAIT);
  382         if (opts == NULL)
  383                 return;
  384 
  385         olen = option[IPOPT_OLEN];
  386         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
  387                 m_tag_free((struct m_tag *)opts);
  388                 return;
  389         }
  390         bcopy(option, opts->ip_srcrt.srcopt, olen);
  391         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
  392         opts->ip_srcrt.dst = dst;
  393         m_tag_prepend(m, (struct m_tag *)opts);
  394 }
  395 
  396 /*
  397  * Retrieve incoming source route for use in replies, in the same form used
  398  * by setsockopt.  The first hop is placed before the options, will be
  399  * removed later.
  400  */
  401 struct mbuf *
  402 ip_srcroute(struct mbuf *m0)
  403 {
  404         struct in_addr *p, *q;
  405         struct mbuf *m;
  406         struct ipopt_tag *opts;
  407 
  408         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
  409         if (opts == NULL)
  410                 return (NULL);
  411 
  412         if (opts->ip_nhops == 0)
  413                 return (NULL);
  414         m = m_get(M_NOWAIT, MT_DATA);
  415         if (m == NULL)
  416                 return (NULL);
  417 
  418 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
  419 
  420         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
  421         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
  422             sizeof(struct in_addr) + OPTSIZ;
  423 
  424         /*
  425          * First, save first hop for return route.
  426          */
  427         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
  428         *(mtod(m, struct in_addr *)) = *p--;
  429 
  430         /*
  431          * Copy option fields and padding (nop) to mbuf.
  432          */
  433         opts->ip_srcrt.nop = IPOPT_NOP;
  434         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
  435         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
  436             &(opts->ip_srcrt.nop), OPTSIZ);
  437         q = (struct in_addr *)(mtod(m, caddr_t) +
  438             sizeof(struct in_addr) + OPTSIZ);
  439 #undef OPTSIZ
  440         /*
  441          * Record return path as an IP source route, reversing the path
  442          * (pointers are now aligned).
  443          */
  444         while (p >= opts->ip_srcrt.route) {
  445                 *q++ = *p--;
  446         }
  447         /*
  448          * Last hop goes to final destination.
  449          */
  450         *q = opts->ip_srcrt.dst;
  451         m_tag_delete(m0, (struct m_tag *)opts);
  452         return (m);
  453 }
  454 
  455 /*
  456  * Strip out IP options, at higher level protocol in the kernel.
  457  */
  458 void
  459 ip_stripoptions(struct mbuf *m)
  460 {
  461         struct ip *ip = mtod(m, struct ip *);
  462         int olen;
  463 
  464         olen = (ip->ip_hl << 2) - sizeof(struct ip);
  465         m->m_len -= olen;
  466         if (m->m_flags & M_PKTHDR)
  467                 m->m_pkthdr.len -= olen;
  468         ip->ip_len = htons(ntohs(ip->ip_len) - olen);
  469         ip->ip_hl = sizeof(struct ip) >> 2;
  470 
  471         bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
  472             (size_t )(m->m_len - sizeof(struct ip)));
  473 }
  474 
  475 /*
  476  * Insert IP options into preformed packet.  Adjust IP destination as
  477  * required for IP source routing, as indicated by a non-zero in_addr at the
  478  * start of the options.
  479  *
  480  * XXX This routine assumes that the packet has no options in place.
  481  */
  482 struct mbuf *
  483 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
  484 {
  485         struct ipoption *p = mtod(opt, struct ipoption *);
  486         struct mbuf *n;
  487         struct ip *ip = mtod(m, struct ip *);
  488         unsigned optlen;
  489 
  490         optlen = opt->m_len - sizeof(p->ipopt_dst);
  491         if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
  492                 *phlen = 0;
  493                 return (m);             /* XXX should fail */
  494         }
  495         if (p->ipopt_dst.s_addr)
  496                 ip->ip_dst = p->ipopt_dst;
  497         if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
  498                 n = m_gethdr(M_NOWAIT, MT_DATA);
  499                 if (n == NULL) {
  500                         *phlen = 0;
  501                         return (m);
  502                 }
  503                 m_move_pkthdr(n, m);
  504                 n->m_pkthdr.rcvif = NULL;
  505                 n->m_pkthdr.len += optlen;
  506                 m->m_len -= sizeof(struct ip);
  507                 m->m_data += sizeof(struct ip);
  508                 n->m_next = m;
  509                 m = n;
  510                 m->m_len = optlen + sizeof(struct ip);
  511                 m->m_data += max_linkhdr;
  512                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
  513         } else {
  514                 m->m_data -= optlen;
  515                 m->m_len += optlen;
  516                 m->m_pkthdr.len += optlen;
  517                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
  518         }
  519         ip = mtod(m, struct ip *);
  520         bcopy(p->ipopt_list, ip + 1, optlen);
  521         *phlen = sizeof(struct ip) + optlen;
  522         ip->ip_v = IPVERSION;
  523         ip->ip_hl = *phlen >> 2;
  524         ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
  525         return (m);
  526 }
  527 
  528 /*
  529  * Copy options from ip to jp, omitting those not copied during
  530  * fragmentation.
  531  */
  532 int
  533 ip_optcopy(struct ip *ip, struct ip *jp)
  534 {
  535         u_char *cp, *dp;
  536         int opt, optlen, cnt;
  537 
  538         cp = (u_char *)(ip + 1);
  539         dp = (u_char *)(jp + 1);
  540         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  541         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  542                 opt = cp[0];
  543                 if (opt == IPOPT_EOL)
  544                         break;
  545                 if (opt == IPOPT_NOP) {
  546                         /* Preserve for IP mcast tunnel's LSRR alignment. */
  547                         *dp++ = IPOPT_NOP;
  548                         optlen = 1;
  549                         continue;
  550                 }
  551 
  552                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
  553                     ("ip_optcopy: malformed ipv4 option"));
  554                 optlen = cp[IPOPT_OLEN];
  555                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
  556                     ("ip_optcopy: malformed ipv4 option"));
  557 
  558                 /* Bogus lengths should have been caught by ip_dooptions. */
  559                 if (optlen > cnt)
  560                         optlen = cnt;
  561                 if (IPOPT_COPIED(opt)) {
  562                         bcopy(cp, dp, optlen);
  563                         dp += optlen;
  564                 }
  565         }
  566         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
  567                 *dp++ = IPOPT_EOL;
  568         return (optlen);
  569 }
  570 
  571 /*
  572  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
  573  * with pointer in pcbopt, adding pseudo-option with destination address if
  574  * source routed.
  575  */
  576 int
  577 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
  578 {
  579         int cnt, optlen;
  580         u_char *cp;
  581         struct mbuf **pcbopt;
  582         u_char opt;
  583 
  584         INP_WLOCK_ASSERT(inp);
  585 
  586         pcbopt = &inp->inp_options;
  587 
  588         /* turn off any old options */
  589         if (*pcbopt)
  590                 (void)m_free(*pcbopt);
  591         *pcbopt = 0;
  592         if (m == NULL || m->m_len == 0) {
  593                 /*
  594                  * Only turning off any previous options.
  595                  */
  596                 if (m != NULL)
  597                         (void)m_free(m);
  598                 return (0);
  599         }
  600 
  601         if (m->m_len % sizeof(int32_t))
  602                 goto bad;
  603         /*
  604          * IP first-hop destination address will be stored before actual
  605          * options; move other options back and clear it when none present.
  606          */
  607         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
  608                 goto bad;
  609         cnt = m->m_len;
  610         m->m_len += sizeof(struct in_addr);
  611         cp = mtod(m, u_char *) + sizeof(struct in_addr);
  612         bcopy(mtod(m, void *), cp, (unsigned)cnt);
  613         bzero(mtod(m, void *), sizeof(struct in_addr));
  614 
  615         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  616                 opt = cp[IPOPT_OPTVAL];
  617                 if (opt == IPOPT_EOL)
  618                         break;
  619                 if (opt == IPOPT_NOP)
  620                         optlen = 1;
  621                 else {
  622                         if (cnt < IPOPT_OLEN + sizeof(*cp))
  623                                 goto bad;
  624                         optlen = cp[IPOPT_OLEN];
  625                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
  626                                 goto bad;
  627                 }
  628                 switch (opt) {
  629 
  630                 default:
  631                         break;
  632 
  633                 case IPOPT_LSRR:
  634                 case IPOPT_SSRR:
  635                         /*
  636                          * User process specifies route as:
  637                          *
  638                          *      ->A->B->C->D
  639                          *
  640                          * D must be our final destination (but we can't
  641                          * check that since we may not have connected yet).
  642                          * A is first hop destination, which doesn't appear
  643                          * in actual IP option, but is stored before the
  644                          * options.
  645                          */
  646                         /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
  647                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
  648                                 goto bad;
  649                         m->m_len -= sizeof(struct in_addr);
  650                         cnt -= sizeof(struct in_addr);
  651                         optlen -= sizeof(struct in_addr);
  652                         cp[IPOPT_OLEN] = optlen;
  653                         /*
  654                          * Move first hop before start of options.
  655                          */
  656                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
  657                             sizeof(struct in_addr));
  658                         /*
  659                          * Then copy rest of options back
  660                          * to close up the deleted entry.
  661                          */
  662                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
  663                             &cp[IPOPT_OFFSET+1],
  664                             (unsigned)cnt - (IPOPT_MINOFF - 1));
  665                         break;
  666                 }
  667         }
  668         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
  669                 goto bad;
  670         *pcbopt = m;
  671         return (0);
  672 
  673 bad:
  674         (void)m_free(m);
  675         return (EINVAL);
  676 }
  677 
  678 /*
  679  * Check for the presence of the IP Router Alert option [RFC2113]
  680  * in the header of an IPv4 datagram.
  681  *
  682  * This call is not intended for use from the forwarding path; it is here
  683  * so that protocol domains may check for the presence of the option.
  684  * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
  685  * option does not have much relevance to the implementation, though this
  686  * may change in future.
  687  * Router alert options SHOULD be passed if running in IPSTEALTH mode and
  688  * we are not the endpoint.
  689  * Length checks on individual options should already have been peformed
  690  * by ip_dooptions() therefore they are folded under INVARIANTS here.
  691  *
  692  * Return zero if not present or options are invalid, non-zero if present.
  693  */
  694 int
  695 ip_checkrouteralert(struct mbuf *m)
  696 {
  697         struct ip *ip = mtod(m, struct ip *);
  698         u_char *cp;
  699         int opt, optlen, cnt, found_ra;
  700 
  701         found_ra = 0;
  702         cp = (u_char *)(ip + 1);
  703         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  704         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  705                 opt = cp[IPOPT_OPTVAL];
  706                 if (opt == IPOPT_EOL)
  707                         break;
  708                 if (opt == IPOPT_NOP)
  709                         optlen = 1;
  710                 else {
  711 #ifdef INVARIANTS
  712                         if (cnt < IPOPT_OLEN + sizeof(*cp))
  713                                 break;
  714 #endif
  715                         optlen = cp[IPOPT_OLEN];
  716 #ifdef INVARIANTS
  717                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
  718                                 break;
  719 #endif
  720                 }
  721                 switch (opt) {
  722                 case IPOPT_RA:
  723 #ifdef INVARIANTS
  724                         if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
  725                             (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
  726                             break;
  727                         else
  728 #endif
  729                         found_ra = 1;
  730                         break;
  731                 default:
  732                         break;
  733                 }
  734         }
  735 
  736         return (found_ra);
  737 }

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