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/10.3/sys/netinet/ip_options.c 272869 2014-10-09 23:46:17Z hrs $");
   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 VNET_DEFINE(int, ip_dosourceroute);
   69 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
   70     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0,
   71     "Enable forwarding source routed IP packets");
   72 #define V_ip_dosourceroute      VNET(ip_dosourceroute)
   73 
   74 static VNET_DEFINE(int, ip_acceptsourceroute);
   75 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute, 
   76     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0, 
   77     "Enable accepting source routed IP packets");
   78 #define V_ip_acceptsourceroute  VNET(ip_acceptsourceroute)
   79 
   80 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */
   81 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW,
   82     &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)");
   83 
   84 static void     save_rte(struct mbuf *m, u_char *, struct in_addr);
   85 
   86 /*
   87  * Do option processing on a datagram, possibly discarding it if bad options
   88  * are encountered, or forwarding it if source-routed.
   89  *
   90  * The pass argument is used when operating in the IPSTEALTH mode to tell
   91  * what options to process: [LS]SRR (pass 0) or the others (pass 1).  The
   92  * reason for as many as two passes is that when doing IPSTEALTH, non-routing
   93  * options should be processed only if the packet is for us.
   94  *
   95  * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
   96  * processed further.
   97  */
   98 int
   99 ip_dooptions(struct mbuf *m, int pass)
  100 {
  101         struct ip *ip = mtod(m, struct ip *);
  102         u_char *cp;
  103         struct in_ifaddr *ia;
  104         int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
  105         struct in_addr *sin, dst;
  106         uint32_t ntime;
  107         struct  sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
  108 
  109         /* Ignore or reject packets with IP options. */
  110         if (V_ip_doopts == 0)
  111                 return 0;
  112         else if (V_ip_doopts == 2) {
  113                 type = ICMP_UNREACH;
  114                 code = ICMP_UNREACH_FILTER_PROHIB;
  115                 goto bad;
  116         }
  117 
  118         dst = ip->ip_dst;
  119         cp = (u_char *)(ip + 1);
  120         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  121         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  122                 opt = cp[IPOPT_OPTVAL];
  123                 if (opt == IPOPT_EOL)
  124                         break;
  125                 if (opt == IPOPT_NOP)
  126                         optlen = 1;
  127                 else {
  128                         if (cnt < IPOPT_OLEN + sizeof(*cp)) {
  129                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  130                                 goto bad;
  131                         }
  132                         optlen = cp[IPOPT_OLEN];
  133                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
  134                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  135                                 goto bad;
  136                         }
  137                 }
  138                 switch (opt) {
  139 
  140                 default:
  141                         break;
  142 
  143                 /*
  144                  * Source routing with record.  Find interface with current
  145                  * destination address.  If none on this machine then drop if
  146                  * strictly routed, or do nothing if loosely routed.  Record
  147                  * interface address and bring up next address component.  If
  148                  * strictly routed make sure next address is on directly
  149                  * accessible net.
  150                  */
  151                 case IPOPT_LSRR:
  152                 case IPOPT_SSRR:
  153 #ifdef IPSTEALTH
  154                         if (V_ipstealth && pass > 0)
  155                                 break;
  156 #endif
  157                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
  158                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  159                                 goto bad;
  160                         }
  161                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  162                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  163                                 goto bad;
  164                         }
  165                         ipaddr.sin_addr = ip->ip_dst;
  166                         if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
  167                             == 0) {
  168                                 if (opt == IPOPT_SSRR) {
  169                                         type = ICMP_UNREACH;
  170                                         code = ICMP_UNREACH_SRCFAIL;
  171                                         goto bad;
  172                                 }
  173                                 if (!V_ip_dosourceroute)
  174                                         goto nosourcerouting;
  175                                 /*
  176                                  * Loose routing, and not at next destination
  177                                  * yet; nothing to do except forward.
  178                                  */
  179                                 break;
  180                         }
  181                         off--;                  /* 0 origin */
  182                         if (off > optlen - (int)sizeof(struct in_addr)) {
  183                                 /*
  184                                  * End of source route.  Should be for us.
  185                                  */
  186                                 if (!V_ip_acceptsourceroute)
  187                                         goto nosourcerouting;
  188                                 save_rte(m, cp, ip->ip_src);
  189                                 break;
  190                         }
  191 #ifdef IPSTEALTH
  192                         if (V_ipstealth)
  193                                 goto dropit;
  194 #endif
  195                         if (!V_ip_dosourceroute) {
  196                                 if (V_ipforwarding) {
  197                                         char buf[16]; /* aaa.bbb.ccc.ddd\0 */
  198                                         /*
  199                                          * Acting as a router, so generate
  200                                          * ICMP
  201                                          */
  202 nosourcerouting:
  203                                         strcpy(buf, inet_ntoa(ip->ip_dst));
  204                                         log(LOG_WARNING, 
  205                                             "attempted source route from %s to %s\n",
  206                                             inet_ntoa(ip->ip_src), buf);
  207                                         type = ICMP_UNREACH;
  208                                         code = ICMP_UNREACH_SRCFAIL;
  209                                         goto bad;
  210                                 } else {
  211                                         /*
  212                                          * Not acting as a router, so
  213                                          * silently drop.
  214                                          */
  215 #ifdef IPSTEALTH
  216 dropit:
  217 #endif
  218                                         IPSTAT_INC(ips_cantforward);
  219                                         m_freem(m);
  220                                         return (1);
  221                                 }
  222                         }
  223 
  224                         /*
  225                          * locate outgoing interface
  226                          */
  227                         (void)memcpy(&ipaddr.sin_addr, cp + off,
  228                             sizeof(ipaddr.sin_addr));
  229 
  230                         if (opt == IPOPT_SSRR) {
  231 #define INA     struct in_ifaddr *
  232 #define SA      struct sockaddr *
  233                             if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == NULL)
  234                                     ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0);
  235                         } else
  236 /* XXX MRT 0 for routing */
  237                                 ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m));
  238                         if (ia == NULL) {
  239                                 type = ICMP_UNREACH;
  240                                 code = ICMP_UNREACH_SRCFAIL;
  241                                 goto bad;
  242                         }
  243                         ip->ip_dst = ipaddr.sin_addr;
  244                         (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  245                             sizeof(struct in_addr));
  246                         ifa_free(&ia->ia_ifa);
  247                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  248                         /*
  249                          * Let ip_intr's mcast routing check handle mcast pkts
  250                          */
  251                         forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
  252                         break;
  253 
  254                 case IPOPT_RR:
  255 #ifdef IPSTEALTH
  256                         if (V_ipstealth && pass == 0)
  257                                 break;
  258 #endif
  259                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
  260                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  261                                 goto bad;
  262                         }
  263                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  264                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  265                                 goto bad;
  266                         }
  267                         /*
  268                          * If no space remains, ignore.
  269                          */
  270                         off--;                  /* 0 origin */
  271                         if (off > optlen - (int)sizeof(struct in_addr))
  272                                 break;
  273                         (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
  274                             sizeof(ipaddr.sin_addr));
  275                         /*
  276                          * Locate outgoing interface; if we're the
  277                          * destination, use the incoming interface (should be
  278                          * same).
  279                          */
  280                         if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == NULL &&
  281                             (ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m))) == NULL) {
  282                                 type = ICMP_UNREACH;
  283                                 code = ICMP_UNREACH_HOST;
  284                                 goto bad;
  285                         }
  286                         (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  287                             sizeof(struct in_addr));
  288                         ifa_free(&ia->ia_ifa);
  289                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  290                         break;
  291 
  292                 case IPOPT_TS:
  293 #ifdef IPSTEALTH
  294                         if (V_ipstealth && pass == 0)
  295                                 break;
  296 #endif
  297                         code = cp - (u_char *)ip;
  298                         if (optlen < 4 || optlen > 40) {
  299                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  300                                 goto bad;
  301                         }
  302                         if ((off = cp[IPOPT_OFFSET]) < 5) {
  303                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  304                                 goto bad;
  305                         }
  306                         if (off > optlen - (int)sizeof(int32_t)) {
  307                                 cp[IPOPT_OFFSET + 1] += (1 << 4);
  308                                 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
  309                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  310                                         goto bad;
  311                                 }
  312                                 break;
  313                         }
  314                         off--;                          /* 0 origin */
  315                         sin = (struct in_addr *)(cp + off);
  316                         switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
  317 
  318                         case IPOPT_TS_TSONLY:
  319                                 break;
  320 
  321                         case IPOPT_TS_TSANDADDR:
  322                                 if (off + sizeof(uint32_t) +
  323                                     sizeof(struct in_addr) > optlen) {
  324                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  325                                         goto bad;
  326                                 }
  327                                 ipaddr.sin_addr = dst;
  328                                 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
  329                                                             m->m_pkthdr.rcvif);
  330                                 if (ia == NULL)
  331                                         continue;
  332                                 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
  333                                     sizeof(struct in_addr));
  334                                 ifa_free(&ia->ia_ifa);
  335                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  336                                 off += sizeof(struct in_addr);
  337                                 break;
  338 
  339                         case IPOPT_TS_PRESPEC:
  340                                 if (off + sizeof(uint32_t) +
  341                                     sizeof(struct in_addr) > optlen) {
  342                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  343                                         goto bad;
  344                                 }
  345                                 (void)memcpy(&ipaddr.sin_addr, sin,
  346                                     sizeof(struct in_addr));
  347                                 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
  348                                         continue;
  349                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  350                                 off += sizeof(struct in_addr);
  351                                 break;
  352 
  353                         default:
  354                                 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
  355                                 goto bad;
  356                         }
  357                         ntime = iptime();
  358                         (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
  359                         cp[IPOPT_OFFSET] += sizeof(uint32_t);
  360                 }
  361         }
  362         if (forward && V_ipforwarding) {
  363                 ip_forward(m, 1);
  364                 return (1);
  365         }
  366         return (0);
  367 bad:
  368         icmp_error(m, type, code, 0, 0);
  369         IPSTAT_INC(ips_badoptions);
  370         return (1);
  371 }
  372 
  373 /*
  374  * Save incoming source route for use in replies, to be picked up later by
  375  * ip_srcroute if the receiver is interested.
  376  */
  377 static void
  378 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
  379 {
  380         unsigned olen;
  381         struct ipopt_tag *opts;
  382 
  383         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
  384             sizeof(struct ipopt_tag), M_NOWAIT);
  385         if (opts == NULL)
  386                 return;
  387 
  388         olen = option[IPOPT_OLEN];
  389         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
  390                 m_tag_free((struct m_tag *)opts);
  391                 return;
  392         }
  393         bcopy(option, opts->ip_srcrt.srcopt, olen);
  394         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
  395         opts->ip_srcrt.dst = dst;
  396         m_tag_prepend(m, (struct m_tag *)opts);
  397 }
  398 
  399 /*
  400  * Retrieve incoming source route for use in replies, in the same form used
  401  * by setsockopt.  The first hop is placed before the options, will be
  402  * removed later.
  403  */
  404 struct mbuf *
  405 ip_srcroute(struct mbuf *m0)
  406 {
  407         struct in_addr *p, *q;
  408         struct mbuf *m;
  409         struct ipopt_tag *opts;
  410 
  411         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
  412         if (opts == NULL)
  413                 return (NULL);
  414 
  415         if (opts->ip_nhops == 0)
  416                 return (NULL);
  417         m = m_get(M_NOWAIT, MT_DATA);
  418         if (m == NULL)
  419                 return (NULL);
  420 
  421 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
  422 
  423         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
  424         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
  425             sizeof(struct in_addr) + OPTSIZ;
  426 
  427         /*
  428          * First, save first hop for return route.
  429          */
  430         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
  431         *(mtod(m, struct in_addr *)) = *p--;
  432 
  433         /*
  434          * Copy option fields and padding (nop) to mbuf.
  435          */
  436         opts->ip_srcrt.nop = IPOPT_NOP;
  437         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
  438         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
  439             &(opts->ip_srcrt.nop), OPTSIZ);
  440         q = (struct in_addr *)(mtod(m, caddr_t) +
  441             sizeof(struct in_addr) + OPTSIZ);
  442 #undef OPTSIZ
  443         /*
  444          * Record return path as an IP source route, reversing the path
  445          * (pointers are now aligned).
  446          */
  447         while (p >= opts->ip_srcrt.route) {
  448                 *q++ = *p--;
  449         }
  450         /*
  451          * Last hop goes to final destination.
  452          */
  453         *q = opts->ip_srcrt.dst;
  454         m_tag_delete(m0, (struct m_tag *)opts);
  455         return (m);
  456 }
  457 
  458 /*
  459  * Strip out IP options, at higher level protocol in the kernel.
  460  */
  461 void
  462 ip_stripoptions(struct mbuf *m)
  463 {
  464         struct ip *ip = mtod(m, struct ip *);
  465         int olen;
  466 
  467         olen = (ip->ip_hl << 2) - sizeof(struct ip);
  468         m->m_len -= olen;
  469         if (m->m_flags & M_PKTHDR)
  470                 m->m_pkthdr.len -= olen;
  471         ip->ip_len = htons(ntohs(ip->ip_len) - olen);
  472         ip->ip_hl = sizeof(struct ip) >> 2;
  473 
  474         bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
  475             (size_t )(m->m_len - sizeof(struct ip)));
  476 }
  477 
  478 /*
  479  * Insert IP options into preformed packet.  Adjust IP destination as
  480  * required for IP source routing, as indicated by a non-zero in_addr at the
  481  * start of the options.
  482  *
  483  * XXX This routine assumes that the packet has no options in place.
  484  */
  485 struct mbuf *
  486 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
  487 {
  488         struct ipoption *p = mtod(opt, struct ipoption *);
  489         struct mbuf *n;
  490         struct ip *ip = mtod(m, struct ip *);
  491         unsigned optlen;
  492 
  493         optlen = opt->m_len - sizeof(p->ipopt_dst);
  494         if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
  495                 *phlen = 0;
  496                 return (m);             /* XXX should fail */
  497         }
  498         if (p->ipopt_dst.s_addr)
  499                 ip->ip_dst = p->ipopt_dst;
  500         if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
  501                 n = m_gethdr(M_NOWAIT, MT_DATA);
  502                 if (n == NULL) {
  503                         *phlen = 0;
  504                         return (m);
  505                 }
  506                 m_move_pkthdr(n, m);
  507                 n->m_pkthdr.rcvif = NULL;
  508                 n->m_pkthdr.len += optlen;
  509                 m->m_len -= sizeof(struct ip);
  510                 m->m_data += sizeof(struct ip);
  511                 n->m_next = m;
  512                 m = n;
  513                 m->m_len = optlen + sizeof(struct ip);
  514                 m->m_data += max_linkhdr;
  515                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
  516         } else {
  517                 m->m_data -= optlen;
  518                 m->m_len += optlen;
  519                 m->m_pkthdr.len += optlen;
  520                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
  521         }
  522         ip = mtod(m, struct ip *);
  523         bcopy(p->ipopt_list, ip + 1, optlen);
  524         *phlen = sizeof(struct ip) + optlen;
  525         ip->ip_v = IPVERSION;
  526         ip->ip_hl = *phlen >> 2;
  527         ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
  528         return (m);
  529 }
  530 
  531 /*
  532  * Copy options from ip to jp, omitting those not copied during
  533  * fragmentation.
  534  */
  535 int
  536 ip_optcopy(struct ip *ip, struct ip *jp)
  537 {
  538         u_char *cp, *dp;
  539         int opt, optlen, cnt;
  540 
  541         cp = (u_char *)(ip + 1);
  542         dp = (u_char *)(jp + 1);
  543         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  544         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  545                 opt = cp[0];
  546                 if (opt == IPOPT_EOL)
  547                         break;
  548                 if (opt == IPOPT_NOP) {
  549                         /* Preserve for IP mcast tunnel's LSRR alignment. */
  550                         *dp++ = IPOPT_NOP;
  551                         optlen = 1;
  552                         continue;
  553                 }
  554 
  555                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
  556                     ("ip_optcopy: malformed ipv4 option"));
  557                 optlen = cp[IPOPT_OLEN];
  558                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
  559                     ("ip_optcopy: malformed ipv4 option"));
  560 
  561                 /* Bogus lengths should have been caught by ip_dooptions. */
  562                 if (optlen > cnt)
  563                         optlen = cnt;
  564                 if (IPOPT_COPIED(opt)) {
  565                         bcopy(cp, dp, optlen);
  566                         dp += optlen;
  567                 }
  568         }
  569         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
  570                 *dp++ = IPOPT_EOL;
  571         return (optlen);
  572 }
  573 
  574 /*
  575  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
  576  * with pointer in pcbopt, adding pseudo-option with destination address if
  577  * source routed.
  578  */
  579 int
  580 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
  581 {
  582         int cnt, optlen;
  583         u_char *cp;
  584         struct mbuf **pcbopt;
  585         u_char opt;
  586 
  587         INP_WLOCK_ASSERT(inp);
  588 
  589         pcbopt = &inp->inp_options;
  590 
  591         /* turn off any old options */
  592         if (*pcbopt)
  593                 (void)m_free(*pcbopt);
  594         *pcbopt = 0;
  595         if (m == NULL || m->m_len == 0) {
  596                 /*
  597                  * Only turning off any previous options.
  598                  */
  599                 if (m != NULL)
  600                         (void)m_free(m);
  601                 return (0);
  602         }
  603 
  604         if (m->m_len % sizeof(int32_t))
  605                 goto bad;
  606         /*
  607          * IP first-hop destination address will be stored before actual
  608          * options; move other options back and clear it when none present.
  609          */
  610         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
  611                 goto bad;
  612         cnt = m->m_len;
  613         m->m_len += sizeof(struct in_addr);
  614         cp = mtod(m, u_char *) + sizeof(struct in_addr);
  615         bcopy(mtod(m, void *), cp, (unsigned)cnt);
  616         bzero(mtod(m, void *), sizeof(struct in_addr));
  617 
  618         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  619                 opt = cp[IPOPT_OPTVAL];
  620                 if (opt == IPOPT_EOL)
  621                         break;
  622                 if (opt == IPOPT_NOP)
  623                         optlen = 1;
  624                 else {
  625                         if (cnt < IPOPT_OLEN + sizeof(*cp))
  626                                 goto bad;
  627                         optlen = cp[IPOPT_OLEN];
  628                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
  629                                 goto bad;
  630                 }
  631                 switch (opt) {
  632 
  633                 default:
  634                         break;
  635 
  636                 case IPOPT_LSRR:
  637                 case IPOPT_SSRR:
  638                         /*
  639                          * User process specifies route as:
  640                          *
  641                          *      ->A->B->C->D
  642                          *
  643                          * D must be our final destination (but we can't
  644                          * check that since we may not have connected yet).
  645                          * A is first hop destination, which doesn't appear
  646                          * in actual IP option, but is stored before the
  647                          * options.
  648                          */
  649                         /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
  650                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
  651                                 goto bad;
  652                         m->m_len -= sizeof(struct in_addr);
  653                         cnt -= sizeof(struct in_addr);
  654                         optlen -= sizeof(struct in_addr);
  655                         cp[IPOPT_OLEN] = optlen;
  656                         /*
  657                          * Move first hop before start of options.
  658                          */
  659                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
  660                             sizeof(struct in_addr));
  661                         /*
  662                          * Then copy rest of options back
  663                          * to close up the deleted entry.
  664                          */
  665                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
  666                             &cp[IPOPT_OFFSET+1],
  667                             (unsigned)cnt - (IPOPT_MINOFF - 1));
  668                         break;
  669                 }
  670         }
  671         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
  672                 goto bad;
  673         *pcbopt = m;
  674         return (0);
  675 
  676 bad:
  677         (void)m_free(m);
  678         return (EINVAL);
  679 }
  680 
  681 /*
  682  * Check for the presence of the IP Router Alert option [RFC2113]
  683  * in the header of an IPv4 datagram.
  684  *
  685  * This call is not intended for use from the forwarding path; it is here
  686  * so that protocol domains may check for the presence of the option.
  687  * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
  688  * option does not have much relevance to the implementation, though this
  689  * may change in future.
  690  * Router alert options SHOULD be passed if running in IPSTEALTH mode and
  691  * we are not the endpoint.
  692  * Length checks on individual options should already have been peformed
  693  * by ip_dooptions() therefore they are folded under INVARIANTS here.
  694  *
  695  * Return zero if not present or options are invalid, non-zero if present.
  696  */
  697 int
  698 ip_checkrouteralert(struct mbuf *m)
  699 {
  700         struct ip *ip = mtod(m, struct ip *);
  701         u_char *cp;
  702         int opt, optlen, cnt, found_ra;
  703 
  704         found_ra = 0;
  705         cp = (u_char *)(ip + 1);
  706         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  707         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  708                 opt = cp[IPOPT_OPTVAL];
  709                 if (opt == IPOPT_EOL)
  710                         break;
  711                 if (opt == IPOPT_NOP)
  712                         optlen = 1;
  713                 else {
  714 #ifdef INVARIANTS
  715                         if (cnt < IPOPT_OLEN + sizeof(*cp))
  716                                 break;
  717 #endif
  718                         optlen = cp[IPOPT_OLEN];
  719 #ifdef INVARIANTS
  720                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
  721                                 break;
  722 #endif
  723                 }
  724                 switch (opt) {
  725                 case IPOPT_RA:
  726 #ifdef INVARIANTS
  727                         if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
  728                             (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
  729                             break;
  730                         else
  731 #endif
  732                         found_ra = 1;
  733                         break;
  734                 default:
  735                         break;
  736                 }
  737         }
  738 
  739         return (found_ra);
  740 }

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