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/8.2/sys/netinet/ip_options.c 213947 2010-10-17 08:46:34Z bz $");
   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 #include <security/mac/mac_framework.h>
   69 
   70 static int      ip_dosourceroute = 0;
   71 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, CTLFLAG_RW,
   72     &ip_dosourceroute, 0, "Enable forwarding source routed IP packets");
   73 
   74 static int      ip_acceptsourceroute = 0;
   75 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute, 
   76     CTLFLAG_RW, &ip_acceptsourceroute, 0, 
   77     "Enable accepting source routed IP packets");
   78 
   79 int             ip_doopts = 1;  /* 0 = ignore, 1 = process, 2 = reject */
   80 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_RW,
   81     &ip_doopts, 0, "Enable IP options processing ([LS]SRR, RR, TS)");
   82 
   83 static void     save_rte(struct mbuf *m, u_char *, struct in_addr);
   84 
   85 /*
   86  * Do option processing on a datagram, possibly discarding it if bad options
   87  * are encountered, or forwarding it if source-routed.
   88  *
   89  * The pass argument is used when operating in the IPSTEALTH mode to tell
   90  * what options to process: [LS]SRR (pass 0) or the others (pass 1).  The
   91  * reason for as many as two passes is that when doing IPSTEALTH, non-routing
   92  * options should be processed only if the packet is for us.
   93  *
   94  * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
   95  * processed further.
   96  */
   97 int
   98 ip_dooptions(struct mbuf *m, int pass)
   99 {
  100         struct ip *ip = mtod(m, struct ip *);
  101         u_char *cp;
  102         struct in_ifaddr *ia;
  103         int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
  104         struct in_addr *sin, dst;
  105         uint32_t ntime;
  106         struct  sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
  107 
  108         /* Ignore or reject packets with IP options. */
  109         if (ip_doopts == 0)
  110                 return 0;
  111         else if (ip_doopts == 2) {
  112                 type = ICMP_UNREACH;
  113                 code = ICMP_UNREACH_FILTER_PROHIB;
  114                 goto bad;
  115         }
  116 
  117         dst = ip->ip_dst;
  118         cp = (u_char *)(ip + 1);
  119         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  120         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  121                 opt = cp[IPOPT_OPTVAL];
  122                 if (opt == IPOPT_EOL)
  123                         break;
  124                 if (opt == IPOPT_NOP)
  125                         optlen = 1;
  126                 else {
  127                         if (cnt < IPOPT_OLEN + sizeof(*cp)) {
  128                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  129                                 goto bad;
  130                         }
  131                         optlen = cp[IPOPT_OLEN];
  132                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
  133                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  134                                 goto bad;
  135                         }
  136                 }
  137                 switch (opt) {
  138 
  139                 default:
  140                         break;
  141 
  142                 /*
  143                  * Source routing with record.  Find interface with current
  144                  * destination address.  If none on this machine then drop if
  145                  * strictly routed, or do nothing if loosely routed.  Record
  146                  * interface address and bring up next address component.  If
  147                  * strictly routed make sure next address is on directly
  148                  * accessible net.
  149                  */
  150                 case IPOPT_LSRR:
  151                 case IPOPT_SSRR:
  152 #ifdef IPSTEALTH
  153                         if (V_ipstealth && pass > 0)
  154                                 break;
  155 #endif
  156                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
  157                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  158                                 goto bad;
  159                         }
  160                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  161                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  162                                 goto bad;
  163                         }
  164                         ipaddr.sin_addr = ip->ip_dst;
  165                         if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
  166                             == 0) {
  167                                 if (opt == IPOPT_SSRR) {
  168                                         type = ICMP_UNREACH;
  169                                         code = ICMP_UNREACH_SRCFAIL;
  170                                         goto bad;
  171                                 }
  172                                 if (!ip_dosourceroute)
  173                                         goto nosourcerouting;
  174                                 /*
  175                                  * Loose routing, and not at next destination
  176                                  * yet; nothing to do except forward.
  177                                  */
  178                                 break;
  179                         }
  180                         off--;                  /* 0 origin */
  181                         if (off > optlen - (int)sizeof(struct in_addr)) {
  182                                 /*
  183                                  * End of source route.  Should be for us.
  184                                  */
  185                                 if (!ip_acceptsourceroute)
  186                                         goto nosourcerouting;
  187                                 save_rte(m, cp, ip->ip_src);
  188                                 break;
  189                         }
  190 #ifdef IPSTEALTH
  191                         if (V_ipstealth)
  192                                 goto dropit;
  193 #endif
  194                         if (!ip_dosourceroute) {
  195                                 if (V_ipforwarding) {
  196                                         char buf[16]; /* aaa.bbb.ccc.ddd\0 */
  197                                         /*
  198                                          * Acting as a router, so generate
  199                                          * ICMP
  200                                          */
  201 nosourcerouting:
  202                                         strcpy(buf, inet_ntoa(ip->ip_dst));
  203                                         log(LOG_WARNING, 
  204                                             "attempted source route from %s to %s\n",
  205                                             inet_ntoa(ip->ip_src), buf);
  206                                         type = ICMP_UNREACH;
  207                                         code = ICMP_UNREACH_SRCFAIL;
  208                                         goto bad;
  209                                 } else {
  210                                         /*
  211                                          * Not acting as a router, so
  212                                          * silently drop.
  213                                          */
  214 #ifdef IPSTEALTH
  215 dropit:
  216 #endif
  217                                         IPSTAT_INC(ips_cantforward);
  218                                         m_freem(m);
  219                                         return (1);
  220                                 }
  221                         }
  222 
  223                         /*
  224                          * locate outgoing interface
  225                          */
  226                         (void)memcpy(&ipaddr.sin_addr, cp + off,
  227                             sizeof(ipaddr.sin_addr));
  228 
  229                         if (opt == IPOPT_SSRR) {
  230 #define INA     struct in_ifaddr *
  231 #define SA      struct sockaddr *
  232                             if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == NULL)
  233                                     ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0);
  234                         } else
  235 /* XXX MRT 0 for routing */
  236                                 ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m));
  237                         if (ia == NULL) {
  238                                 type = ICMP_UNREACH;
  239                                 code = ICMP_UNREACH_SRCFAIL;
  240                                 goto bad;
  241                         }
  242                         ip->ip_dst = ipaddr.sin_addr;
  243                         (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  244                             sizeof(struct in_addr));
  245                         ifa_free(&ia->ia_ifa);
  246                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  247                         /*
  248                          * Let ip_intr's mcast routing check handle mcast pkts
  249                          */
  250                         forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
  251                         break;
  252 
  253                 case IPOPT_RR:
  254 #ifdef IPSTEALTH
  255                         if (V_ipstealth && pass == 0)
  256                                 break;
  257 #endif
  258                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
  259                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  260                                 goto bad;
  261                         }
  262                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  263                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  264                                 goto bad;
  265                         }
  266                         /*
  267                          * If no space remains, ignore.
  268                          */
  269                         off--;                  /* 0 origin */
  270                         if (off > optlen - (int)sizeof(struct in_addr))
  271                                 break;
  272                         (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
  273                             sizeof(ipaddr.sin_addr));
  274                         /*
  275                          * Locate outgoing interface; if we're the
  276                          * destination, use the incoming interface (should be
  277                          * same).
  278                          */
  279                         if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == NULL &&
  280                             (ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m))) == NULL) {
  281                                 type = ICMP_UNREACH;
  282                                 code = ICMP_UNREACH_HOST;
  283                                 goto bad;
  284                         }
  285                         (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  286                             sizeof(struct in_addr));
  287                         ifa_free(&ia->ia_ifa);
  288                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  289                         break;
  290 
  291                 case IPOPT_TS:
  292 #ifdef IPSTEALTH
  293                         if (V_ipstealth && pass == 0)
  294                                 break;
  295 #endif
  296                         code = cp - (u_char *)ip;
  297                         if (optlen < 4 || optlen > 40) {
  298                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  299                                 goto bad;
  300                         }
  301                         if ((off = cp[IPOPT_OFFSET]) < 5) {
  302                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  303                                 goto bad;
  304                         }
  305                         if (off > optlen - (int)sizeof(int32_t)) {
  306                                 cp[IPOPT_OFFSET + 1] += (1 << 4);
  307                                 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
  308                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  309                                         goto bad;
  310                                 }
  311                                 break;
  312                         }
  313                         off--;                          /* 0 origin */
  314                         sin = (struct in_addr *)(cp + off);
  315                         switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
  316 
  317                         case IPOPT_TS_TSONLY:
  318                                 break;
  319 
  320                         case IPOPT_TS_TSANDADDR:
  321                                 if (off + sizeof(uint32_t) +
  322                                     sizeof(struct in_addr) > optlen) {
  323                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  324                                         goto bad;
  325                                 }
  326                                 ipaddr.sin_addr = dst;
  327                                 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
  328                                                             m->m_pkthdr.rcvif);
  329                                 if (ia == NULL)
  330                                         continue;
  331                                 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
  332                                     sizeof(struct in_addr));
  333                                 ifa_free(&ia->ia_ifa);
  334                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  335                                 off += sizeof(struct in_addr);
  336                                 break;
  337 
  338                         case IPOPT_TS_PRESPEC:
  339                                 if (off + sizeof(uint32_t) +
  340                                     sizeof(struct in_addr) > optlen) {
  341                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  342                                         goto bad;
  343                                 }
  344                                 (void)memcpy(&ipaddr.sin_addr, sin,
  345                                     sizeof(struct in_addr));
  346                                 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
  347                                         continue;
  348                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  349                                 off += sizeof(struct in_addr);
  350                                 break;
  351 
  352                         default:
  353                                 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
  354                                 goto bad;
  355                         }
  356                         ntime = iptime();
  357                         (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
  358                         cp[IPOPT_OFFSET] += sizeof(uint32_t);
  359                 }
  360         }
  361         if (forward && V_ipforwarding) {
  362                 ip_forward(m, 1);
  363                 return (1);
  364         }
  365         return (0);
  366 bad:
  367         icmp_error(m, type, code, 0, 0);
  368         IPSTAT_INC(ips_badoptions);
  369         return (1);
  370 }
  371 
  372 /*
  373  * Save incoming source route for use in replies, to be picked up later by
  374  * ip_srcroute if the receiver is interested.
  375  */
  376 static void
  377 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
  378 {
  379         unsigned olen;
  380         struct ipopt_tag *opts;
  381 
  382         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
  383             sizeof(struct ipopt_tag), M_NOWAIT);
  384         if (opts == NULL)
  385                 return;
  386 
  387         olen = option[IPOPT_OLEN];
  388         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
  389                 m_tag_free((struct m_tag *)opts);
  390                 return;
  391         }
  392         bcopy(option, opts->ip_srcrt.srcopt, olen);
  393         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
  394         opts->ip_srcrt.dst = dst;
  395         m_tag_prepend(m, (struct m_tag *)opts);
  396 }
  397 
  398 /*
  399  * Retrieve incoming source route for use in replies, in the same form used
  400  * by setsockopt.  The first hop is placed before the options, will be
  401  * removed later.
  402  */
  403 struct mbuf *
  404 ip_srcroute(struct mbuf *m0)
  405 {
  406         struct in_addr *p, *q;
  407         struct mbuf *m;
  408         struct ipopt_tag *opts;
  409 
  410         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
  411         if (opts == NULL)
  412                 return (NULL);
  413 
  414         if (opts->ip_nhops == 0)
  415                 return (NULL);
  416         m = m_get(M_DONTWAIT, MT_DATA);
  417         if (m == NULL)
  418                 return (NULL);
  419 
  420 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
  421 
  422         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
  423         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
  424             sizeof(struct in_addr) + OPTSIZ;
  425 
  426         /*
  427          * First, save first hop for return route.
  428          */
  429         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
  430         *(mtod(m, struct in_addr *)) = *p--;
  431 
  432         /*
  433          * Copy option fields and padding (nop) to mbuf.
  434          */
  435         opts->ip_srcrt.nop = IPOPT_NOP;
  436         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
  437         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
  438             &(opts->ip_srcrt.nop), OPTSIZ);
  439         q = (struct in_addr *)(mtod(m, caddr_t) +
  440             sizeof(struct in_addr) + OPTSIZ);
  441 #undef OPTSIZ
  442         /*
  443          * Record return path as an IP source route, reversing the path
  444          * (pointers are now aligned).
  445          */
  446         while (p >= opts->ip_srcrt.route) {
  447                 *q++ = *p--;
  448         }
  449         /*
  450          * Last hop goes to final destination.
  451          */
  452         *q = opts->ip_srcrt.dst;
  453         m_tag_delete(m0, (struct m_tag *)opts);
  454         return (m);
  455 }
  456 
  457 /*
  458  * Strip out IP options, at higher level protocol in the kernel.  Second
  459  * argument is buffer to which options will be moved, and return value is
  460  * their length.
  461  *
  462  * XXX should be deleted; last arg currently ignored.
  463  */
  464 void
  465 ip_stripoptions(struct mbuf *m, struct mbuf *mopt)
  466 {
  467         int i;
  468         struct ip *ip = mtod(m, struct ip *);
  469         caddr_t opts;
  470         int olen;
  471 
  472         olen = (ip->ip_hl << 2) - sizeof (struct ip);
  473         opts = (caddr_t)(ip + 1);
  474         i = m->m_len - (sizeof (struct ip) + olen);
  475         bcopy(opts + olen, opts, (unsigned)i);
  476         m->m_len -= olen;
  477         if (m->m_flags & M_PKTHDR)
  478                 m->m_pkthdr.len -= olen;
  479         ip->ip_v = IPVERSION;
  480         ip->ip_hl = sizeof(struct ip) >> 2;
  481 }
  482 
  483 /*
  484  * Insert IP options into preformed packet.  Adjust IP destination as
  485  * required for IP source routing, as indicated by a non-zero in_addr at the
  486  * start of the options.
  487  *
  488  * XXX This routine assumes that the packet has no options in place.
  489  */
  490 struct mbuf *
  491 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
  492 {
  493         struct ipoption *p = mtod(opt, struct ipoption *);
  494         struct mbuf *n;
  495         struct ip *ip = mtod(m, struct ip *);
  496         unsigned optlen;
  497 
  498         optlen = opt->m_len - sizeof(p->ipopt_dst);
  499         if (optlen + ip->ip_len > IP_MAXPACKET) {
  500                 *phlen = 0;
  501                 return (m);             /* XXX should fail */
  502         }
  503         if (p->ipopt_dst.s_addr)
  504                 ip->ip_dst = p->ipopt_dst;
  505         if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
  506                 MGETHDR(n, M_DONTWAIT, MT_DATA);
  507                 if (n == NULL) {
  508                         *phlen = 0;
  509                         return (m);
  510                 }
  511                 M_MOVE_PKTHDR(n, m);
  512                 n->m_pkthdr.rcvif = NULL;
  513                 n->m_pkthdr.len += optlen;
  514                 m->m_len -= sizeof(struct ip);
  515                 m->m_data += sizeof(struct ip);
  516                 n->m_next = m;
  517                 m = n;
  518                 m->m_len = optlen + sizeof(struct ip);
  519                 m->m_data += max_linkhdr;
  520                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
  521         } else {
  522                 m->m_data -= optlen;
  523                 m->m_len += optlen;
  524                 m->m_pkthdr.len += optlen;
  525                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
  526         }
  527         ip = mtod(m, struct ip *);
  528         bcopy(p->ipopt_list, ip + 1, optlen);
  529         *phlen = sizeof(struct ip) + optlen;
  530         ip->ip_v = IPVERSION;
  531         ip->ip_hl = *phlen >> 2;
  532         ip->ip_len += optlen;
  533         return (m);
  534 }
  535 
  536 /*
  537  * Copy options from ip to jp, omitting those not copied during
  538  * fragmentation.
  539  */
  540 int
  541 ip_optcopy(struct ip *ip, struct ip *jp)
  542 {
  543         u_char *cp, *dp;
  544         int opt, optlen, cnt;
  545 
  546         cp = (u_char *)(ip + 1);
  547         dp = (u_char *)(jp + 1);
  548         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  549         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  550                 opt = cp[0];
  551                 if (opt == IPOPT_EOL)
  552                         break;
  553                 if (opt == IPOPT_NOP) {
  554                         /* Preserve for IP mcast tunnel's LSRR alignment. */
  555                         *dp++ = IPOPT_NOP;
  556                         optlen = 1;
  557                         continue;
  558                 }
  559 
  560                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
  561                     ("ip_optcopy: malformed ipv4 option"));
  562                 optlen = cp[IPOPT_OLEN];
  563                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
  564                     ("ip_optcopy: malformed ipv4 option"));
  565 
  566                 /* Bogus lengths should have been caught by ip_dooptions. */
  567                 if (optlen > cnt)
  568                         optlen = cnt;
  569                 if (IPOPT_COPIED(opt)) {
  570                         bcopy(cp, dp, optlen);
  571                         dp += optlen;
  572                 }
  573         }
  574         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
  575                 *dp++ = IPOPT_EOL;
  576         return (optlen);
  577 }
  578 
  579 /*
  580  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
  581  * with pointer in pcbopt, adding pseudo-option with destination address if
  582  * source routed.
  583  */
  584 int
  585 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
  586 {
  587         int cnt, optlen;
  588         u_char *cp;
  589         struct mbuf **pcbopt;
  590         u_char opt;
  591 
  592         INP_WLOCK_ASSERT(inp);
  593 
  594         pcbopt = &inp->inp_options;
  595 
  596         /* turn off any old options */
  597         if (*pcbopt)
  598                 (void)m_free(*pcbopt);
  599         *pcbopt = 0;
  600         if (m == NULL || m->m_len == 0) {
  601                 /*
  602                  * Only turning off any previous options.
  603                  */
  604                 if (m != NULL)
  605                         (void)m_free(m);
  606                 return (0);
  607         }
  608 
  609         if (m->m_len % sizeof(int32_t))
  610                 goto bad;
  611         /*
  612          * IP first-hop destination address will be stored before actual
  613          * options; move other options back and clear it when none present.
  614          */
  615         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
  616                 goto bad;
  617         cnt = m->m_len;
  618         m->m_len += sizeof(struct in_addr);
  619         cp = mtod(m, u_char *) + sizeof(struct in_addr);
  620         bcopy(mtod(m, void *), cp, (unsigned)cnt);
  621         bzero(mtod(m, void *), sizeof(struct in_addr));
  622 
  623         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  624                 opt = cp[IPOPT_OPTVAL];
  625                 if (opt == IPOPT_EOL)
  626                         break;
  627                 if (opt == IPOPT_NOP)
  628                         optlen = 1;
  629                 else {
  630                         if (cnt < IPOPT_OLEN + sizeof(*cp))
  631                                 goto bad;
  632                         optlen = cp[IPOPT_OLEN];
  633                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
  634                                 goto bad;
  635                 }
  636                 switch (opt) {
  637 
  638                 default:
  639                         break;
  640 
  641                 case IPOPT_LSRR:
  642                 case IPOPT_SSRR:
  643                         /*
  644                          * User process specifies route as:
  645                          *
  646                          *      ->A->B->C->D
  647                          *
  648                          * D must be our final destination (but we can't
  649                          * check that since we may not have connected yet).
  650                          * A is first hop destination, which doesn't appear
  651                          * in actual IP option, but is stored before the
  652                          * options.
  653                          */
  654                         /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
  655                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
  656                                 goto bad;
  657                         m->m_len -= sizeof(struct in_addr);
  658                         cnt -= sizeof(struct in_addr);
  659                         optlen -= sizeof(struct in_addr);
  660                         cp[IPOPT_OLEN] = optlen;
  661                         /*
  662                          * Move first hop before start of options.
  663                          */
  664                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
  665                             sizeof(struct in_addr));
  666                         /*
  667                          * Then copy rest of options back
  668                          * to close up the deleted entry.
  669                          */
  670                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
  671                             &cp[IPOPT_OFFSET+1],
  672                             (unsigned)cnt - (IPOPT_MINOFF - 1));
  673                         break;
  674                 }
  675         }
  676         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
  677                 goto bad;
  678         *pcbopt = m;
  679         return (0);
  680 
  681 bad:
  682         (void)m_free(m);
  683         return (EINVAL);
  684 }
  685 
  686 /*
  687  * Check for the presence of the IP Router Alert option [RFC2113]
  688  * in the header of an IPv4 datagram.
  689  *
  690  * This call is not intended for use from the forwarding path; it is here
  691  * so that protocol domains may check for the presence of the option.
  692  * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
  693  * option does not have much relevance to the implementation, though this
  694  * may change in future.
  695  * Router alert options SHOULD be passed if running in IPSTEALTH mode and
  696  * we are not the endpoint.
  697  * Length checks on individual options should already have been peformed
  698  * by ip_dooptions() therefore they are folded under INVARIANTS here.
  699  *
  700  * Return zero if not present or options are invalid, non-zero if present.
  701  */
  702 int
  703 ip_checkrouteralert(struct mbuf *m)
  704 {
  705         struct ip *ip = mtod(m, struct ip *);
  706         u_char *cp;
  707         int opt, optlen, cnt, found_ra;
  708 
  709         found_ra = 0;
  710         cp = (u_char *)(ip + 1);
  711         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  712         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  713                 opt = cp[IPOPT_OPTVAL];
  714                 if (opt == IPOPT_EOL)
  715                         break;
  716                 if (opt == IPOPT_NOP)
  717                         optlen = 1;
  718                 else {
  719 #ifdef INVARIANTS
  720                         if (cnt < IPOPT_OLEN + sizeof(*cp))
  721                                 break;
  722 #endif
  723                         optlen = cp[IPOPT_OLEN];
  724 #ifdef INVARIANTS
  725                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
  726                                 break;
  727 #endif
  728                 }
  729                 switch (opt) {
  730                 case IPOPT_RA:
  731 #ifdef INVARIANTS
  732                         if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
  733                             (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
  734                             break;
  735                         else
  736 #endif
  737                         found_ra = 1;
  738                         break;
  739                 default:
  740                         break;
  741                 }
  742         }
  743 
  744         return (found_ra);
  745 }

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