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/11.1/sys/netinet/ip_options.c 315456 2017-03-17 14:54:10Z vangyzen $");
   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_fib.h>
   58 #include <netinet/in_systm.h>
   59 #include <netinet/in_var.h>
   60 #include <netinet/ip.h>
   61 #include <netinet/in_pcb.h>
   62 #include <netinet/ip_var.h>
   63 #include <netinet/ip_options.h>
   64 #include <netinet/ip_icmp.h>
   65 #include <machine/in_cksum.h>
   66 
   67 #include <sys/socketvar.h>
   68 
   69 static VNET_DEFINE(int, ip_dosourceroute);
   70 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
   71     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0,
   72     "Enable forwarding source routed IP packets");
   73 #define V_ip_dosourceroute      VNET(ip_dosourceroute)
   74 
   75 static VNET_DEFINE(int, ip_acceptsourceroute);
   76 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute, 
   77     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0, 
   78     "Enable accepting source routed IP packets");
   79 #define V_ip_acceptsourceroute  VNET(ip_acceptsourceroute)
   80 
   81 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */
   82 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW,
   83     &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)");
   84 
   85 static void     save_rte(struct mbuf *m, u_char *, struct in_addr);
   86 
   87 /*
   88  * Do option processing on a datagram, possibly discarding it if bad options
   89  * are encountered, or forwarding it if source-routed.
   90  *
   91  * The pass argument is used when operating in the IPSTEALTH mode to tell
   92  * what options to process: [LS]SRR (pass 0) or the others (pass 1).  The
   93  * reason for as many as two passes is that when doing IPSTEALTH, non-routing
   94  * options should be processed only if the packet is for us.
   95  *
   96  * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
   97  * processed further.
   98  */
   99 int
  100 ip_dooptions(struct mbuf *m, int pass)
  101 {
  102         struct ip *ip = mtod(m, struct ip *);
  103         u_char *cp;
  104         struct in_ifaddr *ia;
  105         int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
  106         struct in_addr *sin, dst;
  107         uint32_t ntime;
  108         struct nhop4_extended nh_ext;
  109         struct  sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
  110 
  111         /* Ignore or reject packets with IP options. */
  112         if (V_ip_doopts == 0)
  113                 return 0;
  114         else if (V_ip_doopts == 2) {
  115                 type = ICMP_UNREACH;
  116                 code = ICMP_UNREACH_FILTER_PROHIB;
  117                 goto bad;
  118         }
  119 
  120         dst = ip->ip_dst;
  121         cp = (u_char *)(ip + 1);
  122         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  123         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  124                 opt = cp[IPOPT_OPTVAL];
  125                 if (opt == IPOPT_EOL)
  126                         break;
  127                 if (opt == IPOPT_NOP)
  128                         optlen = 1;
  129                 else {
  130                         if (cnt < IPOPT_OLEN + sizeof(*cp)) {
  131                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  132                                 goto bad;
  133                         }
  134                         optlen = cp[IPOPT_OLEN];
  135                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
  136                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  137                                 goto bad;
  138                         }
  139                 }
  140                 switch (opt) {
  141 
  142                 default:
  143                         break;
  144 
  145                 /*
  146                  * Source routing with record.  Find interface with current
  147                  * destination address.  If none on this machine then drop if
  148                  * strictly routed, or do nothing if loosely routed.  Record
  149                  * interface address and bring up next address component.  If
  150                  * strictly routed make sure next address is on directly
  151                  * accessible net.
  152                  */
  153                 case IPOPT_LSRR:
  154                 case IPOPT_SSRR:
  155 #ifdef IPSTEALTH
  156                         if (V_ipstealth && pass > 0)
  157                                 break;
  158 #endif
  159                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
  160                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  161                                 goto bad;
  162                         }
  163                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  164                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  165                                 goto bad;
  166                         }
  167                         ipaddr.sin_addr = ip->ip_dst;
  168                         if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
  169                             == 0) {
  170                                 if (opt == IPOPT_SSRR) {
  171                                         type = ICMP_UNREACH;
  172                                         code = ICMP_UNREACH_SRCFAIL;
  173                                         goto bad;
  174                                 }
  175                                 if (!V_ip_dosourceroute)
  176                                         goto nosourcerouting;
  177                                 /*
  178                                  * Loose routing, and not at next destination
  179                                  * yet; nothing to do except forward.
  180                                  */
  181                                 break;
  182                         }
  183                         off--;                  /* 0 origin */
  184                         if (off > optlen - (int)sizeof(struct in_addr)) {
  185                                 /*
  186                                  * End of source route.  Should be for us.
  187                                  */
  188                                 if (!V_ip_acceptsourceroute)
  189                                         goto nosourcerouting;
  190                                 save_rte(m, cp, ip->ip_src);
  191                                 break;
  192                         }
  193 #ifdef IPSTEALTH
  194                         if (V_ipstealth)
  195                                 goto dropit;
  196 #endif
  197                         if (!V_ip_dosourceroute) {
  198                                 if (V_ipforwarding) {
  199                                         char srcbuf[INET_ADDRSTRLEN];
  200                                         char dstbuf[INET_ADDRSTRLEN];
  201 
  202                                         /*
  203                                          * Acting as a router, so generate
  204                                          * ICMP
  205                                          */
  206 nosourcerouting:
  207                                         log(LOG_WARNING, 
  208                                             "attempted source route from %s "
  209                                             "to %s\n",
  210                                             inet_ntoa_r(ip->ip_src, srcbuf),
  211                                             inet_ntoa_r(ip->ip_dst, dstbuf));
  212                                         type = ICMP_UNREACH;
  213                                         code = ICMP_UNREACH_SRCFAIL;
  214                                         goto bad;
  215                                 } else {
  216                                         /*
  217                                          * Not acting as a router, so
  218                                          * silently drop.
  219                                          */
  220 #ifdef IPSTEALTH
  221 dropit:
  222 #endif
  223                                         IPSTAT_INC(ips_cantforward);
  224                                         m_freem(m);
  225                                         return (1);
  226                                 }
  227                         }
  228 
  229                         /*
  230                          * locate outgoing interface
  231                          */
  232                         (void)memcpy(&ipaddr.sin_addr, cp + off,
  233                             sizeof(ipaddr.sin_addr));
  234 
  235                         type = ICMP_UNREACH;
  236                         code = ICMP_UNREACH_SRCFAIL;
  237 
  238                         if (opt == IPOPT_SSRR) {
  239 #define INA     struct in_ifaddr *
  240 #define SA      struct sockaddr *
  241                             ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr,
  242                                             RT_ALL_FIBS);
  243                             if (ia == NULL)
  244                                     ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0,
  245                                                     RT_ALL_FIBS);
  246                                 if (ia == NULL)
  247                                         goto bad;
  248 
  249                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  250                                     sizeof(struct in_addr));
  251                                 ifa_free(&ia->ia_ifa);
  252                         } else {
  253                                 /* XXX MRT 0 for routing */
  254                                 if (fib4_lookup_nh_ext(M_GETFIB(m),
  255                                     ipaddr.sin_addr, 0, 0, &nh_ext) != 0)
  256                                         goto bad;
  257 
  258                                 memcpy(cp + off, &nh_ext.nh_src,
  259                                     sizeof(struct in_addr));
  260                         }
  261 
  262                         ip->ip_dst = ipaddr.sin_addr;
  263                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  264                         /*
  265                          * Let ip_intr's mcast routing check handle mcast pkts
  266                          */
  267                         forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
  268                         break;
  269 
  270                 case IPOPT_RR:
  271 #ifdef IPSTEALTH
  272                         if (V_ipstealth && pass == 0)
  273                                 break;
  274 #endif
  275                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
  276                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  277                                 goto bad;
  278                         }
  279                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  280                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  281                                 goto bad;
  282                         }
  283                         /*
  284                          * If no space remains, ignore.
  285                          */
  286                         off--;                  /* 0 origin */
  287                         if (off > optlen - (int)sizeof(struct in_addr))
  288                                 break;
  289                         (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
  290                             sizeof(ipaddr.sin_addr));
  291                         /*
  292                          * Locate outgoing interface; if we're the
  293                          * destination, use the incoming interface (should be
  294                          * same).
  295                          */
  296                         if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) {
  297                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  298                                     sizeof(struct in_addr));
  299                                 ifa_free(&ia->ia_ifa);
  300                         } else if (fib4_lookup_nh_ext(M_GETFIB(m),
  301                             ipaddr.sin_addr, 0, 0, &nh_ext) == 0) {
  302                                 memcpy(cp + off, &nh_ext.nh_src,
  303                                     sizeof(struct in_addr));
  304                         } else {
  305                                 type = ICMP_UNREACH;
  306                                 code = ICMP_UNREACH_HOST;
  307                                 goto bad;
  308                         }
  309                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  310                         break;
  311 
  312                 case IPOPT_TS:
  313 #ifdef IPSTEALTH
  314                         if (V_ipstealth && pass == 0)
  315                                 break;
  316 #endif
  317                         code = cp - (u_char *)ip;
  318                         if (optlen < 4 || optlen > 40) {
  319                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  320                                 goto bad;
  321                         }
  322                         if ((off = cp[IPOPT_OFFSET]) < 5) {
  323                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
  324                                 goto bad;
  325                         }
  326                         if (off > optlen - (int)sizeof(int32_t)) {
  327                                 cp[IPOPT_OFFSET + 1] += (1 << 4);
  328                                 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
  329                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  330                                         goto bad;
  331                                 }
  332                                 break;
  333                         }
  334                         off--;                          /* 0 origin */
  335                         sin = (struct in_addr *)(cp + off);
  336                         switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
  337 
  338                         case IPOPT_TS_TSONLY:
  339                                 break;
  340 
  341                         case IPOPT_TS_TSANDADDR:
  342                                 if (off + sizeof(uint32_t) +
  343                                     sizeof(struct in_addr) > optlen) {
  344                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  345                                         goto bad;
  346                                 }
  347                                 ipaddr.sin_addr = dst;
  348                                 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
  349                                                             m->m_pkthdr.rcvif);
  350                                 if (ia == NULL)
  351                                         continue;
  352                                 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
  353                                     sizeof(struct in_addr));
  354                                 ifa_free(&ia->ia_ifa);
  355                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  356                                 off += sizeof(struct in_addr);
  357                                 break;
  358 
  359                         case IPOPT_TS_PRESPEC:
  360                                 if (off + sizeof(uint32_t) +
  361                                     sizeof(struct in_addr) > optlen) {
  362                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  363                                         goto bad;
  364                                 }
  365                                 (void)memcpy(&ipaddr.sin_addr, sin,
  366                                     sizeof(struct in_addr));
  367                                 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
  368                                         continue;
  369                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
  370                                 off += sizeof(struct in_addr);
  371                                 break;
  372 
  373                         default:
  374                                 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
  375                                 goto bad;
  376                         }
  377                         ntime = iptime();
  378                         (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
  379                         cp[IPOPT_OFFSET] += sizeof(uint32_t);
  380                 }
  381         }
  382         if (forward && V_ipforwarding) {
  383                 ip_forward(m, 1);
  384                 return (1);
  385         }
  386         return (0);
  387 bad:
  388         icmp_error(m, type, code, 0, 0);
  389         IPSTAT_INC(ips_badoptions);
  390         return (1);
  391 }
  392 
  393 /*
  394  * Save incoming source route for use in replies, to be picked up later by
  395  * ip_srcroute if the receiver is interested.
  396  */
  397 static void
  398 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
  399 {
  400         unsigned olen;
  401         struct ipopt_tag *opts;
  402 
  403         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
  404             sizeof(struct ipopt_tag), M_NOWAIT);
  405         if (opts == NULL)
  406                 return;
  407 
  408         olen = option[IPOPT_OLEN];
  409         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
  410                 m_tag_free((struct m_tag *)opts);
  411                 return;
  412         }
  413         bcopy(option, opts->ip_srcrt.srcopt, olen);
  414         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
  415         opts->ip_srcrt.dst = dst;
  416         m_tag_prepend(m, (struct m_tag *)opts);
  417 }
  418 
  419 /*
  420  * Retrieve incoming source route for use in replies, in the same form used
  421  * by setsockopt.  The first hop is placed before the options, will be
  422  * removed later.
  423  */
  424 struct mbuf *
  425 ip_srcroute(struct mbuf *m0)
  426 {
  427         struct in_addr *p, *q;
  428         struct mbuf *m;
  429         struct ipopt_tag *opts;
  430 
  431         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
  432         if (opts == NULL)
  433                 return (NULL);
  434 
  435         if (opts->ip_nhops == 0)
  436                 return (NULL);
  437         m = m_get(M_NOWAIT, MT_DATA);
  438         if (m == NULL)
  439                 return (NULL);
  440 
  441 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
  442 
  443         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
  444         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
  445             sizeof(struct in_addr) + OPTSIZ;
  446 
  447         /*
  448          * First, save first hop for return route.
  449          */
  450         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
  451         *(mtod(m, struct in_addr *)) = *p--;
  452 
  453         /*
  454          * Copy option fields and padding (nop) to mbuf.
  455          */
  456         opts->ip_srcrt.nop = IPOPT_NOP;
  457         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
  458         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
  459             &(opts->ip_srcrt.nop), OPTSIZ);
  460         q = (struct in_addr *)(mtod(m, caddr_t) +
  461             sizeof(struct in_addr) + OPTSIZ);
  462 #undef OPTSIZ
  463         /*
  464          * Record return path as an IP source route, reversing the path
  465          * (pointers are now aligned).
  466          */
  467         while (p >= opts->ip_srcrt.route) {
  468                 *q++ = *p--;
  469         }
  470         /*
  471          * Last hop goes to final destination.
  472          */
  473         *q = opts->ip_srcrt.dst;
  474         m_tag_delete(m0, (struct m_tag *)opts);
  475         return (m);
  476 }
  477 
  478 /*
  479  * Strip out IP options, at higher level protocol in the kernel.
  480  */
  481 void
  482 ip_stripoptions(struct mbuf *m)
  483 {
  484         struct ip *ip = mtod(m, struct ip *);
  485         int olen;
  486 
  487         olen = (ip->ip_hl << 2) - sizeof(struct ip);
  488         m->m_len -= olen;
  489         if (m->m_flags & M_PKTHDR)
  490                 m->m_pkthdr.len -= olen;
  491         ip->ip_len = htons(ntohs(ip->ip_len) - olen);
  492         ip->ip_hl = sizeof(struct ip) >> 2;
  493 
  494         bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
  495             (size_t )(m->m_len - sizeof(struct ip)));
  496 }
  497 
  498 /*
  499  * Insert IP options into preformed packet.  Adjust IP destination as
  500  * required for IP source routing, as indicated by a non-zero in_addr at the
  501  * start of the options.
  502  *
  503  * XXX This routine assumes that the packet has no options in place.
  504  */
  505 struct mbuf *
  506 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
  507 {
  508         struct ipoption *p = mtod(opt, struct ipoption *);
  509         struct mbuf *n;
  510         struct ip *ip = mtod(m, struct ip *);
  511         unsigned optlen;
  512 
  513         optlen = opt->m_len - sizeof(p->ipopt_dst);
  514         if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
  515                 *phlen = 0;
  516                 return (m);             /* XXX should fail */
  517         }
  518         if (p->ipopt_dst.s_addr)
  519                 ip->ip_dst = p->ipopt_dst;
  520         if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
  521                 n = m_gethdr(M_NOWAIT, MT_DATA);
  522                 if (n == NULL) {
  523                         *phlen = 0;
  524                         return (m);
  525                 }
  526                 m_move_pkthdr(n, m);
  527                 n->m_pkthdr.rcvif = NULL;
  528                 n->m_pkthdr.len += optlen;
  529                 m->m_len -= sizeof(struct ip);
  530                 m->m_data += sizeof(struct ip);
  531                 n->m_next = m;
  532                 m = n;
  533                 m->m_len = optlen + sizeof(struct ip);
  534                 m->m_data += max_linkhdr;
  535                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
  536         } else {
  537                 m->m_data -= optlen;
  538                 m->m_len += optlen;
  539                 m->m_pkthdr.len += optlen;
  540                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
  541         }
  542         ip = mtod(m, struct ip *);
  543         bcopy(p->ipopt_list, ip + 1, optlen);
  544         *phlen = sizeof(struct ip) + optlen;
  545         ip->ip_v = IPVERSION;
  546         ip->ip_hl = *phlen >> 2;
  547         ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
  548         return (m);
  549 }
  550 
  551 /*
  552  * Copy options from ip to jp, omitting those not copied during
  553  * fragmentation.
  554  */
  555 int
  556 ip_optcopy(struct ip *ip, struct ip *jp)
  557 {
  558         u_char *cp, *dp;
  559         int opt, optlen, cnt;
  560 
  561         cp = (u_char *)(ip + 1);
  562         dp = (u_char *)(jp + 1);
  563         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  564         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  565                 opt = cp[0];
  566                 if (opt == IPOPT_EOL)
  567                         break;
  568                 if (opt == IPOPT_NOP) {
  569                         /* Preserve for IP mcast tunnel's LSRR alignment. */
  570                         *dp++ = IPOPT_NOP;
  571                         optlen = 1;
  572                         continue;
  573                 }
  574 
  575                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
  576                     ("ip_optcopy: malformed ipv4 option"));
  577                 optlen = cp[IPOPT_OLEN];
  578                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
  579                     ("ip_optcopy: malformed ipv4 option"));
  580 
  581                 /* Bogus lengths should have been caught by ip_dooptions. */
  582                 if (optlen > cnt)
  583                         optlen = cnt;
  584                 if (IPOPT_COPIED(opt)) {
  585                         bcopy(cp, dp, optlen);
  586                         dp += optlen;
  587                 }
  588         }
  589         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
  590                 *dp++ = IPOPT_EOL;
  591         return (optlen);
  592 }
  593 
  594 /*
  595  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
  596  * with pointer in pcbopt, adding pseudo-option with destination address if
  597  * source routed.
  598  */
  599 int
  600 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
  601 {
  602         int cnt, optlen;
  603         u_char *cp;
  604         struct mbuf **pcbopt;
  605         u_char opt;
  606 
  607         INP_WLOCK_ASSERT(inp);
  608 
  609         pcbopt = &inp->inp_options;
  610 
  611         /* turn off any old options */
  612         if (*pcbopt)
  613                 (void)m_free(*pcbopt);
  614         *pcbopt = NULL;
  615         if (m == NULL || m->m_len == 0) {
  616                 /*
  617                  * Only turning off any previous options.
  618                  */
  619                 if (m != NULL)
  620                         (void)m_free(m);
  621                 return (0);
  622         }
  623 
  624         if (m->m_len % sizeof(int32_t))
  625                 goto bad;
  626         /*
  627          * IP first-hop destination address will be stored before actual
  628          * options; move other options back and clear it when none present.
  629          */
  630         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
  631                 goto bad;
  632         cnt = m->m_len;
  633         m->m_len += sizeof(struct in_addr);
  634         cp = mtod(m, u_char *) + sizeof(struct in_addr);
  635         bcopy(mtod(m, void *), cp, (unsigned)cnt);
  636         bzero(mtod(m, void *), sizeof(struct in_addr));
  637 
  638         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  639                 opt = cp[IPOPT_OPTVAL];
  640                 if (opt == IPOPT_EOL)
  641                         break;
  642                 if (opt == IPOPT_NOP)
  643                         optlen = 1;
  644                 else {
  645                         if (cnt < IPOPT_OLEN + sizeof(*cp))
  646                                 goto bad;
  647                         optlen = cp[IPOPT_OLEN];
  648                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
  649                                 goto bad;
  650                 }
  651                 switch (opt) {
  652 
  653                 default:
  654                         break;
  655 
  656                 case IPOPT_LSRR:
  657                 case IPOPT_SSRR:
  658                         /*
  659                          * User process specifies route as:
  660                          *
  661                          *      ->A->B->C->D
  662                          *
  663                          * D must be our final destination (but we can't
  664                          * check that since we may not have connected yet).
  665                          * A is first hop destination, which doesn't appear
  666                          * in actual IP option, but is stored before the
  667                          * options.
  668                          */
  669                         /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
  670                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
  671                                 goto bad;
  672                         m->m_len -= sizeof(struct in_addr);
  673                         cnt -= sizeof(struct in_addr);
  674                         optlen -= sizeof(struct in_addr);
  675                         cp[IPOPT_OLEN] = optlen;
  676                         /*
  677                          * Move first hop before start of options.
  678                          */
  679                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
  680                             sizeof(struct in_addr));
  681                         /*
  682                          * Then copy rest of options back
  683                          * to close up the deleted entry.
  684                          */
  685                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
  686                             &cp[IPOPT_OFFSET+1],
  687                             (unsigned)cnt - (IPOPT_MINOFF - 1));
  688                         break;
  689                 }
  690         }
  691         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
  692                 goto bad;
  693         *pcbopt = m;
  694         return (0);
  695 
  696 bad:
  697         (void)m_free(m);
  698         return (EINVAL);
  699 }
  700 
  701 /*
  702  * Check for the presence of the IP Router Alert option [RFC2113]
  703  * in the header of an IPv4 datagram.
  704  *
  705  * This call is not intended for use from the forwarding path; it is here
  706  * so that protocol domains may check for the presence of the option.
  707  * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
  708  * option does not have much relevance to the implementation, though this
  709  * may change in future.
  710  * Router alert options SHOULD be passed if running in IPSTEALTH mode and
  711  * we are not the endpoint.
  712  * Length checks on individual options should already have been performed
  713  * by ip_dooptions() therefore they are folded under INVARIANTS here.
  714  *
  715  * Return zero if not present or options are invalid, non-zero if present.
  716  */
  717 int
  718 ip_checkrouteralert(struct mbuf *m)
  719 {
  720         struct ip *ip = mtod(m, struct ip *);
  721         u_char *cp;
  722         int opt, optlen, cnt, found_ra;
  723 
  724         found_ra = 0;
  725         cp = (u_char *)(ip + 1);
  726         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
  727         for (; cnt > 0; cnt -= optlen, cp += optlen) {
  728                 opt = cp[IPOPT_OPTVAL];
  729                 if (opt == IPOPT_EOL)
  730                         break;
  731                 if (opt == IPOPT_NOP)
  732                         optlen = 1;
  733                 else {
  734 #ifdef INVARIANTS
  735                         if (cnt < IPOPT_OLEN + sizeof(*cp))
  736                                 break;
  737 #endif
  738                         optlen = cp[IPOPT_OLEN];
  739 #ifdef INVARIANTS
  740                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
  741                                 break;
  742 #endif
  743                 }
  744                 switch (opt) {
  745                 case IPOPT_RA:
  746 #ifdef INVARIANTS
  747                         if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
  748                             (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
  749                             break;
  750                         else
  751 #endif
  752                         found_ra = 1;
  753                         break;
  754                 default:
  755                         break;
  756                 }
  757         }
  758 
  759         return (found_ra);
  760 }

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