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

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    1 /*
    2  * Copyright (c) 1982, 1986, 1988, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)ip_icmp.c   8.2 (Berkeley) 1/4/94
   30  * $FreeBSD: src/sys/netinet/ip_icmp.c,v 1.39.2.19 2003/01/24 05:11:34 sam Exp $
   31  */
   32 
   33 #include "opt_ipsec.h"
   34 
   35 #include <sys/param.h>
   36 #include <sys/systm.h>
   37 #include <sys/mbuf.h>
   38 #include <sys/protosw.h>
   39 #include <sys/socket.h>
   40 #include <sys/socketops.h>
   41 #include <sys/time.h>
   42 #include <sys/kernel.h>
   43 #include <sys/sysctl.h>
   44 #include <sys/in_cksum.h>
   45 
   46 #include <machine/stdarg.h>
   47 
   48 #include <net/if.h>
   49 #include <net/if_types.h>
   50 #include <net/route.h>
   51 
   52 #define _IP_VHL
   53 #include <netinet/in.h>
   54 #include <netinet/in_systm.h>
   55 #include <netinet/in_var.h>
   56 #include <netinet/ip.h>
   57 #include <netinet/ip_icmp.h>
   58 #include <netinet/ip_var.h>
   59 #include <netinet/icmp_var.h>
   60 
   61 #ifdef IPSEC
   62 #include <netinet6/ipsec.h>
   63 #include <netproto/key/key.h>
   64 #endif
   65 
   66 #ifdef FAST_IPSEC
   67 #include <netproto/ipsec/ipsec.h>
   68 #include <netproto/ipsec/key.h>
   69 #define IPSEC
   70 #endif
   71 
   72 /*
   73  * ICMP routines: error generation, receive packet processing, and
   74  * routines to turnaround packets back to the originator, and
   75  * host table maintenance routines.
   76  */
   77 
   78 struct icmpstat icmpstat;
   79 SYSCTL_STRUCT(_net_inet_icmp, ICMPCTL_STATS, stats, CTLFLAG_RW,
   80         &icmpstat, icmpstat, "ICMP statistics");
   81 
   82 static int      icmpmaskrepl = 0;
   83 SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_RW,
   84         &icmpmaskrepl, 0, "Allow replies to netmask requests");
   85 
   86 static int      drop_redirect = 0;
   87 SYSCTL_INT(_net_inet_icmp, OID_AUTO, drop_redirect, CTLFLAG_RW,
   88         &drop_redirect, 0, "Ignore ICMP redirects");
   89 
   90 static int      log_redirect = 0;
   91 SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_RW,
   92         &log_redirect, 0, "Enable output about ICMP redirects");
   93 
   94 static int      discard_sourcequench = 1;
   95 SYSCTL_INT(_net_inet_icmp, OID_AUTO, discard_sourcequench, CTLFLAG_RW,
   96         &discard_sourcequench, 0, "Discard ICMP Source Quench");
   97 
   98 #ifdef ICMP_BANDLIM
   99 
  100 /*
  101  * ICMP error-response bandwidth limiting sysctl.  If not enabled, sysctl
  102  *      variable content is -1 and read-only.
  103  */
  104 
  105 static int      icmplim = 200;
  106 SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RW,
  107         &icmplim, 0, "ICMP bandwidth limit");
  108 #else
  109 
  110 static int      icmplim = -1;
  111 SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RD,
  112         &icmplim, 0, "ICMP bandwidth limit");
  113         
  114 #endif
  115 
  116 static int      icmplim_output = 0;
  117 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_RW,
  118         &icmplim_output, 0, "Enable output about ICMP bandwidth limits");
  119 
  120 /*
  121  * ICMP broadcast echo sysctl
  122  */
  123 
  124 static int      icmpbmcastecho = 0;
  125 SYSCTL_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_RW,
  126     &icmpbmcastecho, 0, "");
  127 
  128 static char     icmp_reply_src[IFNAMSIZ];
  129 SYSCTL_STRING(_net_inet_icmp, OID_AUTO, reply_src, CTLFLAG_RW,
  130         icmp_reply_src, IFNAMSIZ, "icmp reply source for non-local packets.");
  131 
  132 static int      icmp_rfi;
  133 SYSCTL_INT(_net_inet_icmp, OID_AUTO, reply_from_interface, CTLFLAG_RW,
  134         &icmp_rfi, 0, "ICMP reply from incoming interface for "
  135         "non-local packets");
  136 
  137 #ifdef ICMPPRINTFS
  138 int     icmpprintfs = 0;
  139 #endif
  140 
  141 static void     icmp_reflect (struct mbuf *);
  142 static void     icmp_send (struct mbuf *, struct mbuf *, struct route *);
  143 
  144 extern  struct protosw inetsw[];
  145 
  146 /*
  147  * Generate an error packet of type error
  148  * in response to bad packet ip.
  149  */
  150 void
  151 icmp_error(struct mbuf *n, int type, int code, n_long dest, int destmtu)
  152 {
  153         struct ip *oip = mtod(n, struct ip *), *nip;
  154         unsigned oiplen = IP_VHL_HL(oip->ip_vhl) << 2;
  155         struct icmp *icp;
  156         struct mbuf *m;
  157         unsigned icmplen;
  158 
  159 #ifdef ICMPPRINTFS
  160         if (icmpprintfs)
  161                 kprintf("icmp_error(%p, %d, %d)\n", oip, type, code);
  162 #endif
  163         if (type != ICMP_REDIRECT)
  164                 icmpstat.icps_error++;
  165         /*
  166          * Don't send error if the original packet was encrypted.
  167          * Don't send error if not the first fragment of message.
  168          * Don't error if the old packet protocol was ICMP
  169          * error message, only known informational types.
  170          */
  171         if (n->m_flags & M_DECRYPTED)
  172                 goto freeit;
  173         if (oip->ip_off &~ (IP_MF|IP_DF))
  174                 goto freeit;
  175         if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
  176           n->m_len >= oiplen + ICMP_MINLEN &&
  177           !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip + oiplen))->icmp_type)) {
  178                 icmpstat.icps_oldicmp++;
  179                 goto freeit;
  180         }
  181         /* Don't send error in response to a multicast or broadcast packet */
  182         if (n->m_flags & (M_BCAST|M_MCAST))
  183                 goto freeit;
  184         /*
  185          * First, formulate icmp message
  186          */
  187         m = m_gethdr(MB_DONTWAIT, MT_HEADER);
  188         if (m == NULL)
  189                 goto freeit;
  190         icmplen = min(oiplen + 8, oip->ip_len);
  191         if (icmplen < sizeof(struct ip))
  192                 panic("icmp_error: bad length");
  193         m->m_len = icmplen + ICMP_MINLEN;
  194         MH_ALIGN(m, m->m_len);
  195         icp = mtod(m, struct icmp *);
  196         if ((u_int)type > ICMP_MAXTYPE)
  197                 panic("icmp_error");
  198         icmpstat.icps_outhist[type]++;
  199         icp->icmp_type = type;
  200         if (type == ICMP_REDIRECT)
  201                 icp->icmp_gwaddr.s_addr = dest;
  202         else {
  203                 icp->icmp_void = 0;
  204                 /*
  205                  * The following assignments assume an overlay with the
  206                  * zeroed icmp_void field.
  207                  */
  208                 if (type == ICMP_PARAMPROB) {
  209                         icp->icmp_pptr = code;
  210                         code = 0;
  211                 } else if (type == ICMP_UNREACH &&
  212                         code == ICMP_UNREACH_NEEDFRAG && destmtu) {
  213                         icp->icmp_nextmtu = htons(destmtu);
  214                 }
  215         }
  216 
  217         icp->icmp_code = code;
  218         m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip);
  219         nip = &icp->icmp_ip;
  220 
  221         /*
  222          * Convert fields to network representation.
  223          */
  224         nip->ip_len = htons(nip->ip_len);
  225         nip->ip_off = htons(nip->ip_off);
  226 
  227         /*
  228          * Now, copy old ip header (without options)
  229          * in front of icmp message.
  230          */
  231         if (m->m_data - sizeof(struct ip) < m->m_pktdat)
  232                 panic("icmp len");
  233         m->m_data -= sizeof(struct ip);
  234         m->m_len += sizeof(struct ip);
  235         m->m_pkthdr.len = m->m_len;
  236         m->m_pkthdr.rcvif = n->m_pkthdr.rcvif;
  237         nip = mtod(m, struct ip *);
  238         bcopy(oip, nip, sizeof(struct ip));
  239         nip->ip_len = m->m_len;
  240         nip->ip_vhl = IP_VHL_BORING;
  241         nip->ip_p = IPPROTO_ICMP;
  242         nip->ip_tos = 0;
  243         m->m_pkthdr.fw_flags |= n->m_pkthdr.fw_flags & FW_MBUF_GENERATED;
  244         icmp_reflect(m);
  245 
  246 freeit:
  247         m_freem(n);
  248 }
  249 
  250 /*
  251  * Process a received ICMP message.
  252  */
  253 int
  254 icmp_input(struct mbuf **mp, int *offp, int proto)
  255 {
  256         struct sockaddr_in icmpsrc = { sizeof(struct sockaddr_in), AF_INET };
  257         struct sockaddr_in icmpdst = { sizeof(struct sockaddr_in), AF_INET };
  258         struct sockaddr_in icmpgw = { sizeof(struct sockaddr_in), AF_INET };
  259         struct icmp *icp;
  260         struct in_ifaddr *ia;
  261         struct mbuf *m = *mp;
  262         struct ip *ip = mtod(m, struct ip *);
  263         int icmplen = ip->ip_len;
  264         int i, hlen;
  265         int code;
  266 
  267         *mp = NULL;
  268         hlen = *offp;
  269 
  270         /*
  271          * Locate icmp structure in mbuf, and check
  272          * that not corrupted and of at least minimum length.
  273          */
  274 #ifdef ICMPPRINTFS
  275         if (icmpprintfs) {
  276                 char buf[sizeof "aaa.bbb.ccc.ddd"];
  277 
  278                 strcpy(buf, inet_ntoa(ip->ip_src));
  279                 kprintf("icmp_input from %s to %s, len %d\n",
  280                        buf, inet_ntoa(ip->ip_dst), icmplen);
  281         }
  282 #endif
  283         if (icmplen < ICMP_MINLEN) {
  284                 icmpstat.icps_tooshort++;
  285                 goto freeit;
  286         }
  287         i = hlen + min(icmplen, ICMP_ADVLENMIN);
  288         if (m->m_len < i && (m = m_pullup(m, i)) == NULL)  {
  289                 icmpstat.icps_tooshort++;
  290                 return(IPPROTO_DONE);
  291         }
  292         ip = mtod(m, struct ip *);
  293         m->m_len -= hlen;
  294         m->m_data += hlen;
  295         icp = mtod(m, struct icmp *);
  296         if (in_cksum(m, icmplen)) {
  297                 icmpstat.icps_checksum++;
  298                 goto freeit;
  299         }
  300         m->m_len += hlen;
  301         m->m_data -= hlen;
  302 
  303         if (m->m_pkthdr.rcvif && m->m_pkthdr.rcvif->if_type == IFT_FAITH) {
  304                 /*
  305                  * Deliver very specific ICMP type only.
  306                  */
  307                 switch (icp->icmp_type) {
  308                 case ICMP_UNREACH:
  309                 case ICMP_TIMXCEED:
  310                         break;
  311                 default:
  312                         goto freeit;
  313                 }
  314         }
  315 
  316 #ifdef ICMPPRINTFS
  317         if (icmpprintfs)
  318                 kprintf("icmp_input, type %d code %d\n", icp->icmp_type,
  319                     icp->icmp_code);
  320 #endif
  321 
  322         /*
  323          * Message type specific processing.
  324          */
  325         if (icp->icmp_type > ICMP_MAXTYPE)
  326                 goto raw;
  327         icmpstat.icps_inhist[icp->icmp_type]++;
  328         code = icp->icmp_code;
  329         switch (icp->icmp_type) {
  330 
  331         case ICMP_UNREACH:
  332                 switch (code) {
  333                         case ICMP_UNREACH_NET:
  334                         case ICMP_UNREACH_HOST:
  335                         case ICMP_UNREACH_SRCFAIL:
  336                         case ICMP_UNREACH_NET_UNKNOWN:
  337                         case ICMP_UNREACH_HOST_UNKNOWN:
  338                         case ICMP_UNREACH_ISOLATED:
  339                         case ICMP_UNREACH_TOSNET:
  340                         case ICMP_UNREACH_TOSHOST:
  341                         case ICMP_UNREACH_HOST_PRECEDENCE:
  342                         case ICMP_UNREACH_PRECEDENCE_CUTOFF:
  343                                 code = PRC_UNREACH_NET;
  344                                 break;
  345 
  346                         case ICMP_UNREACH_NEEDFRAG:
  347                                 code = PRC_MSGSIZE;
  348                                 break;
  349 
  350                         /*
  351                          * RFC 1122, Sections 3.2.2.1 and 4.2.3.9.
  352                          * Treat subcodes 2,3 as immediate RST
  353                          */
  354                         case ICMP_UNREACH_PROTOCOL:
  355                         case ICMP_UNREACH_PORT:
  356                                 code = PRC_UNREACH_PORT;
  357                                 break;
  358 
  359                         case ICMP_UNREACH_NET_PROHIB:
  360                         case ICMP_UNREACH_HOST_PROHIB:
  361                         case ICMP_UNREACH_FILTER_PROHIB:
  362                                 code = PRC_UNREACH_ADMIN_PROHIB;
  363                                 break;
  364 
  365                         default:
  366                                 goto badcode;
  367                 }
  368                 goto deliver;
  369 
  370         case ICMP_TIMXCEED:
  371                 if (code > 1)
  372                         goto badcode;
  373                 code += PRC_TIMXCEED_INTRANS;
  374                 goto deliver;
  375 
  376         case ICMP_PARAMPROB:
  377                 if (code > 1)
  378                         goto badcode;
  379                 code = PRC_PARAMPROB;
  380                 goto deliver;
  381 
  382         case ICMP_SOURCEQUENCH:
  383                 if (code)
  384                         goto badcode;
  385                 if (discard_sourcequench)
  386                         break;
  387                 code = PRC_QUENCH;
  388 deliver:
  389                 /*
  390                  * Problem with datagram; advise higher level routines.
  391                  */
  392                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  393                     IP_VHL_HL(icp->icmp_ip.ip_vhl) < (sizeof(struct ip) >> 2)) {
  394                         icmpstat.icps_badlen++;
  395                         goto freeit;
  396                 }
  397                 icp->icmp_ip.ip_len = ntohs(icp->icmp_ip.ip_len);
  398                 /* Discard ICMP's in response to multicast packets */
  399                 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
  400                         goto badcode;
  401 #ifdef ICMPPRINTFS
  402                 if (icmpprintfs)
  403                         kprintf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
  404 #endif
  405                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  406 #if 1
  407                 /*
  408                  * MTU discovery:
  409                  * If we got a needfrag and there is a host route to the
  410                  * original destination, and the MTU is not locked, then
  411                  * set the MTU in the route to the suggested new value
  412                  * (if given) and then notify as usual.  The ULPs will
  413                  * notice that the MTU has changed and adapt accordingly.
  414                  * If no new MTU was suggested, then we guess a new one
  415                  * less than the current value.  If the new MTU is
  416                  * unreasonably small (arbitrarily set at 296), then
  417                  * we reset the MTU to the interface value and enable the
  418                  * lock bit, indicating that we are no longer doing MTU
  419                  * discovery.
  420                  */
  421                 if (code == PRC_MSGSIZE) {
  422                         struct rtentry *rt;
  423                         int mtu;
  424 
  425                         rt = rtpurelookup((struct sockaddr *)&icmpsrc);
  426                         if (rt != NULL && (rt->rt_flags & RTF_HOST) &&
  427                             !(rt->rt_rmx.rmx_locks & RTV_MTU)) {
  428                                 mtu = ntohs(icp->icmp_nextmtu);
  429                                 if (!mtu)
  430                                         mtu = ip_next_mtu(rt->rt_rmx.rmx_mtu,
  431                                                           1);
  432 #ifdef DEBUG_MTUDISC
  433                                 kprintf("MTU for %s reduced to %d\n",
  434                                         inet_ntoa(icmpsrc.sin_addr), mtu);
  435 #endif
  436                                 if (mtu < 296) {
  437                                         /* rt->rt_rmx.rmx_mtu =
  438                                                 rt->rt_ifp->if_mtu; */
  439                                         rt->rt_rmx.rmx_locks |= RTV_MTU;
  440                                 } else if (rt->rt_rmx.rmx_mtu > mtu) {
  441                                         rt->rt_rmx.rmx_mtu = mtu;
  442                                 }
  443                         }
  444                         if (rt != NULL)
  445                                 --rt->rt_refcnt;
  446                 }
  447 #endif
  448                 /*
  449                  * XXX if the packet contains [IPv4 AH TCP], we can't make a
  450                  * notification to TCP layer.
  451                  */
  452                 so_pru_ctlinput(
  453                         &inetsw[ip_protox[icp->icmp_ip.ip_p]],
  454                         code, (struct sockaddr *)&icmpsrc, &icp->icmp_ip);
  455                 break;
  456 
  457 badcode:
  458                 icmpstat.icps_badcode++;
  459                 break;
  460 
  461         case ICMP_ECHO:
  462                 if (!icmpbmcastecho
  463                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
  464                         icmpstat.icps_bmcastecho++;
  465                         break;
  466                 }
  467                 icp->icmp_type = ICMP_ECHOREPLY;
  468 #ifdef ICMP_BANDLIM
  469                 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
  470                         goto freeit;
  471                 else
  472 #endif
  473                         goto reflect;
  474 
  475         case ICMP_TSTAMP:
  476                 if (!icmpbmcastecho
  477                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
  478                         icmpstat.icps_bmcasttstamp++;
  479                         break;
  480                 }
  481                 if (icmplen < ICMP_TSLEN) {
  482                         icmpstat.icps_badlen++;
  483                         break;
  484                 }
  485                 icp->icmp_type = ICMP_TSTAMPREPLY;
  486                 icp->icmp_rtime = iptime();
  487                 icp->icmp_ttime = icp->icmp_rtime;      /* bogus, do later! */
  488 #ifdef ICMP_BANDLIM
  489                 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
  490                         goto freeit;
  491                 else
  492 #endif
  493                         goto reflect;
  494 
  495         case ICMP_MASKREQ:
  496                 if (icmpmaskrepl == 0)
  497                         break;
  498                 /*
  499                  * We are not able to respond with all ones broadcast
  500                  * unless we receive it over a point-to-point interface.
  501                  */
  502                 if (icmplen < ICMP_MASKLEN)
  503                         break;
  504                 switch (ip->ip_dst.s_addr) {
  505 
  506                 case INADDR_BROADCAST:
  507                 case INADDR_ANY:
  508                         icmpdst.sin_addr = ip->ip_src;
  509                         break;
  510 
  511                 default:
  512                         icmpdst.sin_addr = ip->ip_dst;
  513                 }
  514                 ia = (struct in_ifaddr *)ifaof_ifpforaddr(
  515                             (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
  516                 if (ia == NULL)
  517                         break;
  518                 if (ia->ia_ifp == 0)
  519                         break;
  520                 icp->icmp_type = ICMP_MASKREPLY;
  521                 icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr;
  522                 if (ip->ip_src.s_addr == 0) {
  523                         if (ia->ia_ifp->if_flags & IFF_BROADCAST)
  524                             ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr;
  525                         else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT)
  526                             ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr;
  527                 }
  528 reflect:
  529                 ip->ip_len += hlen;     /* since ip_input deducts this */
  530                 icmpstat.icps_reflect++;
  531                 icmpstat.icps_outhist[icp->icmp_type]++;
  532                 icmp_reflect(m);
  533                 return(IPPROTO_DONE);
  534 
  535         case ICMP_REDIRECT:
  536                 if (log_redirect) {
  537                         u_long src, dst, gw;
  538 
  539                         src = ntohl(ip->ip_src.s_addr);
  540                         dst = ntohl(icp->icmp_ip.ip_dst.s_addr);
  541                         gw = ntohl(icp->icmp_gwaddr.s_addr);
  542                         kprintf("icmp redirect from %d.%d.%d.%d: "
  543                                "%d.%d.%d.%d => %d.%d.%d.%d\n",
  544                                (int)(src >> 24), (int)((src >> 16) & 0xff),
  545                                (int)((src >> 8) & 0xff), (int)(src & 0xff),
  546                                (int)(dst >> 24), (int)((dst >> 16) & 0xff),
  547                                (int)((dst >> 8) & 0xff), (int)(dst & 0xff),
  548                                (int)(gw >> 24), (int)((gw >> 16) & 0xff),
  549                                (int)((gw >> 8) & 0xff), (int)(gw & 0xff));
  550                 }
  551                 if (drop_redirect)
  552                         break;
  553                 if (code > 3)
  554                         goto badcode;
  555                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  556                     IP_VHL_HL(icp->icmp_ip.ip_vhl) < (sizeof(struct ip) >> 2)) {
  557                         icmpstat.icps_badlen++;
  558                         break;
  559                 }
  560                 /*
  561                  * Short circuit routing redirects to force
  562                  * immediate change in the kernel's routing
  563                  * tables.  The message is also handed to anyone
  564                  * listening on a raw socket (e.g. the routing
  565                  * daemon for use in updating its tables).
  566                  */
  567                 icmpgw.sin_addr = ip->ip_src;
  568                 icmpdst.sin_addr = icp->icmp_gwaddr;
  569 #ifdef  ICMPPRINTFS
  570                 if (icmpprintfs) {
  571                         char buf[sizeof "aaa.bbb.ccc.ddd"];
  572 
  573                         strcpy(buf, inet_ntoa(icp->icmp_ip.ip_dst));
  574                         kprintf("redirect dst %s to %s\n",
  575                                buf, inet_ntoa(icp->icmp_gwaddr));
  576                 }
  577 #endif
  578                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  579                 rtredirect((struct sockaddr *)&icmpsrc,
  580                   (struct sockaddr *)&icmpdst,
  581                   NULL, RTF_GATEWAY | RTF_HOST,
  582                   (struct sockaddr *)&icmpgw);
  583                 kpfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
  584 #ifdef IPSEC
  585                 key_sa_routechange((struct sockaddr *)&icmpsrc);
  586 #endif
  587                 break;
  588 
  589         /*
  590          * No kernel processing for the following;
  591          * just fall through to send to raw listener.
  592          */
  593         case ICMP_ECHOREPLY:
  594         case ICMP_ROUTERADVERT:
  595         case ICMP_ROUTERSOLICIT:
  596         case ICMP_TSTAMPREPLY:
  597         case ICMP_IREQREPLY:
  598         case ICMP_MASKREPLY:
  599         default:
  600                 break;
  601         }
  602 
  603 raw:
  604         *mp = m;
  605         rip_input(mp, offp, proto);
  606         return(IPPROTO_DONE);
  607 
  608 freeit:
  609         m_freem(m);
  610         return(IPPROTO_DONE);
  611 }
  612 
  613 /*
  614  * Reflect the ip packet back to the source
  615  */
  616 static void
  617 icmp_reflect(struct mbuf *m)
  618 {
  619         struct ip *ip = mtod(m, struct ip *);
  620         struct in_ifaddr *ia;
  621         struct in_ifaddr_container *iac;
  622         struct ifaddr_container *ifac;
  623         struct ifnet *ifp;
  624         struct in_addr t;
  625         struct mbuf *opts = NULL;
  626         int optlen = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof(struct ip);
  627         struct route *ro = NULL, rt;
  628 
  629         if (!in_canforward(ip->ip_src) &&
  630             ((ntohl(ip->ip_src.s_addr) & IN_CLASSA_NET) !=
  631              (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))) {
  632                 m_freem(m);     /* Bad return address */
  633                 icmpstat.icps_badaddr++;
  634                 goto done;      /* Ip_output() will check for broadcast */
  635         }
  636         t = ip->ip_dst;
  637         ip->ip_dst = ip->ip_src;
  638 
  639         ro = &rt;
  640         bzero(ro, sizeof *ro);
  641 
  642         /*
  643          * If the incoming packet was addressed directly to us,
  644          * use dst as the src for the reply.  Otherwise (broadcast
  645          * or anonymous), use the address which corresponds
  646          * to the incoming interface.
  647          */
  648         ia = NULL;
  649         LIST_FOREACH(iac, INADDR_HASH(t.s_addr), ia_hash) {
  650                 if (t.s_addr == IA_SIN(iac->ia)->sin_addr.s_addr) {
  651                         ia = iac->ia;
  652                         goto match;
  653                 }
  654         }
  655         ifp = m->m_pkthdr.rcvif;
  656         if (ifp != NULL && (ifp->if_flags & IFF_BROADCAST)) {
  657                 TAILQ_FOREACH(ifac, &ifp->if_addrheads[mycpuid], ifa_link) {
  658                         struct ifaddr *ifa = ifac->ifa;
  659 
  660                         if (ifa->ifa_addr->sa_family != AF_INET)
  661                                 continue;
  662                         ia = ifatoia(ifa);
  663                         if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
  664                             t.s_addr)
  665                                 goto match;
  666                 }
  667         }
  668         /*
  669          * If the packet was transiting through us, use the address of
  670          * the interface the packet came through in.  If that interface
  671          * doesn't have a suitable IP address, the normal selection
  672          * criteria apply.
  673          */
  674         if (icmp_rfi && ifp != NULL) {
  675                 TAILQ_FOREACH(ifac, &ifp->if_addrheads[mycpuid], ifa_link) {
  676                         struct ifaddr *ifa = ifac->ifa;
  677 
  678                         if (ifa->ifa_addr->sa_family != AF_INET)
  679                                 continue;
  680                         ia = ifatoia(ifa);
  681                         goto match;
  682                 }
  683         }
  684         /*
  685          * If the incoming packet was not addressed directly to us, use
  686          * designated interface for icmp replies specified by sysctl
  687          * net.inet.icmp.reply_src (default not set). Otherwise continue
  688          * with normal source selection.
  689          */
  690         if (icmp_reply_src[0] != '\0' && (ifp = ifunit(icmp_reply_src))) {
  691                 TAILQ_FOREACH(ifac, &ifp->if_addrheads[mycpuid], ifa_link) {
  692                         struct ifaddr *ifa = ifac->ifa;
  693 
  694                         if (ifa->ifa_addr->sa_family != AF_INET)
  695                                 continue;
  696                         ia = ifatoia(ifa);
  697                         goto match;
  698                 }
  699         }
  700         /*
  701          * If the packet was transiting through us, use the address of
  702          * the interface that is the closest to the packet source.
  703          * When we don't have a route back to the packet source, stop here
  704          * and drop the packet.
  705          */
  706         ia = ip_rtaddr(ip->ip_dst, ro);
  707         if (ia == NULL) {
  708                 m_freem(m);
  709                 icmpstat.icps_noroute++;
  710                 goto done;
  711         }
  712 match:
  713         t = IA_SIN(ia)->sin_addr;
  714         ip->ip_src = t;
  715         ip->ip_ttl = ip_defttl;
  716 
  717         if (optlen > 0) {
  718                 u_char *cp;
  719                 int opt, cnt;
  720                 u_int len;
  721 
  722                 /*
  723                  * Retrieve any source routing from the incoming packet;
  724                  * add on any record-route or timestamp options.
  725                  */
  726                 cp = (u_char *) (ip + 1);
  727                 if ((opts = ip_srcroute(m)) == NULL &&
  728                     (opts = m_gethdr(MB_DONTWAIT, MT_HEADER))) {
  729                         opts->m_len = sizeof(struct in_addr);
  730                         mtod(opts, struct in_addr *)->s_addr = 0;
  731                 }
  732                 if (opts) {
  733 #ifdef ICMPPRINTFS
  734                         if (icmpprintfs)
  735                                 kprintf("icmp_reflect optlen %d rt %d => ",
  736                                        optlen, opts->m_len);
  737 #endif
  738                         for (cnt = optlen; cnt > 0; cnt -= len, cp += len) {
  739                                 opt = cp[IPOPT_OPTVAL];
  740                                 if (opt == IPOPT_EOL)
  741                                         break;
  742                                 if (opt == IPOPT_NOP)
  743                                         len = 1;
  744                                 else {
  745                                         if (cnt < IPOPT_OLEN + sizeof *cp)
  746                                                 break;
  747                                         len = cp[IPOPT_OLEN];
  748                                         if (len < IPOPT_OLEN + sizeof *cp ||
  749                                             len > cnt)
  750                                         break;
  751                                 }
  752                                 /*
  753                                  * Should check for overflow, but it
  754                                  * "can't happen".
  755                                  */
  756                                 if (opt == IPOPT_RR || opt == IPOPT_TS ||
  757                                     opt == IPOPT_SECURITY) {
  758                                         bcopy(cp,
  759                                               mtod(opts, caddr_t) + opts->m_len,
  760                                               len);
  761                                         opts->m_len += len;
  762                                 }
  763                         }
  764                         /* Terminate & pad, if necessary */
  765                         cnt = opts->m_len % 4;
  766                         if (cnt) {
  767                                 for (; cnt < 4; cnt++) {
  768                                         *(mtod(opts, caddr_t) + opts->m_len) =
  769                                             IPOPT_EOL;
  770                                         opts->m_len++;
  771                                 }
  772                         }
  773 #ifdef ICMPPRINTFS
  774                         if (icmpprintfs)
  775                                 kprintf("%d\n", opts->m_len);
  776 #endif
  777                 }
  778                 /*
  779                  * Now strip out original options by copying rest of first
  780                  * mbuf's data back, and adjust the IP length.
  781                  */
  782                 ip->ip_len -= optlen;
  783                 ip->ip_vhl = IP_VHL_BORING;
  784                 m->m_len -= optlen;
  785                 if (m->m_flags & M_PKTHDR)
  786                         m->m_pkthdr.len -= optlen;
  787                 optlen += sizeof(struct ip);
  788                 bcopy((caddr_t)ip + optlen, ip + 1,
  789                       m->m_len - sizeof(struct ip));
  790         }
  791         m->m_pkthdr.fw_flags &= FW_MBUF_GENERATED;
  792         m->m_flags &= ~(M_BCAST|M_MCAST);
  793         icmp_send(m, opts, ro);
  794 done:
  795         if (opts)
  796                 m_free(opts);
  797         if (ro && ro->ro_rt)
  798                 RTFREE(ro->ro_rt);
  799 }
  800 
  801 /*
  802  * Send an icmp packet back to the ip level,
  803  * after supplying a checksum.
  804  */
  805 static void
  806 icmp_send(struct mbuf *m, struct mbuf *opts, struct route *rt)
  807 {
  808         struct ip *ip = mtod(m, struct ip *);
  809         struct icmp *icp;
  810         int hlen;
  811 
  812         hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  813         m->m_data += hlen;
  814         m->m_len -= hlen;
  815         icp = mtod(m, struct icmp *);
  816         icp->icmp_cksum = 0;
  817         icp->icmp_cksum = in_cksum(m, ip->ip_len - hlen);
  818         m->m_data -= hlen;
  819         m->m_len += hlen;
  820         m->m_pkthdr.rcvif = NULL;
  821 #ifdef ICMPPRINTFS
  822         if (icmpprintfs) {
  823                 char buf[sizeof "aaa.bbb.ccc.ddd"];
  824 
  825                 strcpy(buf, inet_ntoa(ip->ip_dst));
  826                 kprintf("icmp_send dst %s src %s\n", buf, inet_ntoa(ip->ip_src));
  827         }
  828 #endif
  829         ip_output(m, opts, rt, 0, NULL, NULL);
  830 }
  831 
  832 n_time
  833 iptime(void)
  834 {
  835         struct timeval atv;
  836         u_long t;
  837 
  838         getmicrotime(&atv);
  839         t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000;
  840         return (htonl(t));
  841 }
  842 
  843 #if 1
  844 /*
  845  * Return the next larger or smaller MTU plateau (table from RFC 1191)
  846  * given current value MTU.  If DIR is less than zero, a larger plateau
  847  * is returned; otherwise, a smaller value is returned.
  848  */
  849 int
  850 ip_next_mtu(int mtu, int dir)
  851 {
  852         static int mtutab[] = {
  853                 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1006, 508, 296,
  854                 68, 0
  855         };
  856         int i;
  857 
  858         for (i = 0; i < (sizeof mtutab) / (sizeof mtutab[0]); i++) {
  859                 if (mtu >= mtutab[i])
  860                         break;
  861         }
  862 
  863         if (dir < 0) {
  864                 if (i == 0) {
  865                         return 0;
  866                 } else {
  867                         return mtutab[i - 1];
  868                 }
  869         } else {
  870                 if (mtutab[i] == 0) {
  871                         return 0;
  872                 } else if(mtu > mtutab[i]) {
  873                         return mtutab[i];
  874                 } else {
  875                         return mtutab[i + 1];
  876                 }
  877         }
  878 }
  879 #endif
  880 
  881 #ifdef ICMP_BANDLIM
  882 /*
  883  * badport_bandlim() - check for ICMP bandwidth limit
  884  *
  885  *      Return 0 if it is ok to send an ICMP error response, -1 if we have
  886  *      hit our bandwidth limit and it is not ok.
  887  *
  888  *      If icmplim is <= 0, the feature is disabled and 0 is returned.
  889  *
  890  *      For now we separate the TCP and UDP subsystems w/ different 'which'
  891  *      values.  We may eventually remove this separation (and simplify the
  892  *      code further).
  893  *
  894  *      Note that the printing of the error message is delayed so we can
  895  *      properly print the icmp error rate that the system was trying to do
  896  *      (i.e. 22000/100 pps, etc...).  This can cause long delays in printing
  897  *      the 'final' error, but it doesn't make sense to solve the printing
  898  *      delay with more complex code.
  899  */
  900 int
  901 badport_bandlim(int which)
  902 {
  903         static int lticks[BANDLIM_MAX + 1];
  904         static int lpackets[BANDLIM_MAX + 1];
  905         int dticks;
  906         const char *bandlimittype[] = {
  907                 "Limiting icmp unreach response",
  908                 "Limiting icmp ping response",
  909                 "Limiting icmp tstamp response",
  910                 "Limiting closed port RST response",
  911                 "Limiting open port RST response"
  912                 };
  913 
  914         /*
  915          * Return ok status if feature disabled or argument out of
  916          * ranage.
  917          */
  918 
  919         if (icmplim <= 0 || which > BANDLIM_MAX || which < 0)
  920                 return(0);
  921         dticks = ticks - lticks[which];
  922 
  923         /*
  924          * reset stats when cumulative dt exceeds one second.
  925          */
  926 
  927         if ((unsigned int)dticks > hz) {
  928                 if (lpackets[which] > icmplim && icmplim_output) {
  929                         kprintf("%s from %d to %d packets per second\n",
  930                                 bandlimittype[which],
  931                                 lpackets[which],
  932                                 icmplim
  933                         );
  934                 }
  935                 lticks[which] = ticks;
  936                 lpackets[which] = 0;
  937         }
  938 
  939         /*
  940          * bump packet count
  941          */
  942 
  943         if (++lpackets[which] > icmplim) {
  944                 return(-1);
  945         }
  946         return(0);
  947 }
  948 #endif

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