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. All advertising materials mentioning features or use of this software
   14  *    must display the following acknowledgement:
   15  *      This product includes software developed by the University of
   16  *      California, Berkeley and its contributors.
   17  * 4. Neither the name of the University nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  *      @(#)ip_icmp.c   8.2 (Berkeley) 1/4/94
   34  * $FreeBSD: src/sys/netinet/ip_icmp.c,v 1.78 2003/03/21 15:43:06 mdodd Exp $
   35  */
   36 
   37 #include "opt_ipsec.h"
   38 #include "opt_mac.h"
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/mac.h>
   43 #include <sys/mbuf.h>
   44 #include <sys/protosw.h>
   45 #include <sys/socket.h>
   46 #include <sys/time.h>
   47 #include <sys/kernel.h>
   48 #include <sys/sysctl.h>
   49 
   50 #include <net/if.h>
   51 #include <net/if_types.h>
   52 #include <net/route.h>
   53 
   54 #include <netinet/in.h>
   55 #include <netinet/in_systm.h>
   56 #include <netinet/in_var.h>
   57 #include <netinet/ip.h>
   58 #include <netinet/ip_icmp.h>
   59 #include <netinet/ip_var.h>
   60 #include <netinet/icmp_var.h>
   61 
   62 #ifdef IPSEC
   63 #include <netinet6/ipsec.h>
   64 #include <netkey/key.h>
   65 #endif
   66 
   67 #ifdef FAST_IPSEC
   68 #include <netipsec/ipsec.h>
   69 #include <netipsec/key.h>
   70 #define IPSEC
   71 #endif
   72 
   73 #include <machine/in_cksum.h>
   74 
   75 /*
   76  * ICMP routines: error generation, receive packet processing, and
   77  * routines to turnaround packets back to the originator, and
   78  * host table maintenance routines.
   79  */
   80 
   81 static struct   icmpstat icmpstat;
   82 SYSCTL_STRUCT(_net_inet_icmp, ICMPCTL_STATS, stats, CTLFLAG_RW,
   83         &icmpstat, icmpstat, "");
   84 
   85 static int      icmpmaskrepl = 0;
   86 SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_RW,
   87         &icmpmaskrepl, 0, "Reply to ICMP Address Mask Request packets.");
   88 
   89 static u_int    icmpmaskfake = 0;
   90 SYSCTL_UINT(_net_inet_icmp, OID_AUTO, maskfake, CTLFLAG_RW,
   91         &icmpmaskfake, 0, "Fake reply to ICMP Address Mask Request packets.");
   92 
   93 static int      drop_redirect = 0;
   94 SYSCTL_INT(_net_inet_icmp, OID_AUTO, drop_redirect, CTLFLAG_RW, 
   95         &drop_redirect, 0, "");
   96 
   97 static int      log_redirect = 0;
   98 SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_RW, 
   99         &log_redirect, 0, "");
  100 
  101 static int      icmplim = 200;
  102 SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RW,
  103         &icmplim, 0, "");
  104 
  105 static int      icmplim_output = 1;
  106 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_RW,
  107         &icmplim_output, 0, "");
  108 
  109 /*
  110  * ICMP broadcast echo sysctl
  111  */
  112 
  113 static int      icmpbmcastecho = 0;
  114 SYSCTL_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_RW,
  115         &icmpbmcastecho, 0, "");
  116 
  117 
  118 #ifdef ICMPPRINTFS
  119 int     icmpprintfs = 0;
  120 #endif
  121 
  122 static void     icmp_reflect(struct mbuf *);
  123 static void     icmp_send(struct mbuf *, struct mbuf *, struct route *);
  124 static int      ip_next_mtu(int, int);
  125 
  126 extern  struct protosw inetsw[];
  127 
  128 /*
  129  * Generate an error packet of type error
  130  * in response to bad packet ip.
  131  */
  132 void
  133 icmp_error(n, type, code, dest, destifp)
  134         struct mbuf *n;
  135         int type, code;
  136         n_long dest;
  137         struct ifnet *destifp;
  138 {
  139         register struct ip *oip = mtod(n, struct ip *), *nip;
  140         register unsigned oiplen = oip->ip_hl << 2;
  141         register struct icmp *icp;
  142         register struct mbuf *m;
  143         unsigned icmplen;
  144 
  145 #ifdef ICMPPRINTFS
  146         if (icmpprintfs)
  147                 printf("icmp_error(%p, %x, %d)\n", oip, type, code);
  148 #endif
  149         if (type != ICMP_REDIRECT)
  150                 icmpstat.icps_error++;
  151         /*
  152          * Don't send error if not the first fragment of message.
  153          * Don't error if the old packet protocol was ICMP
  154          * error message, only known informational types.
  155          */
  156         if (oip->ip_off &~ (IP_MF|IP_DF))
  157                 goto freeit;
  158         if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
  159           n->m_len >= oiplen + ICMP_MINLEN &&
  160           !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip + oiplen))->icmp_type)) {
  161                 icmpstat.icps_oldicmp++;
  162                 goto freeit;
  163         }
  164         /* Don't send error in response to a multicast or broadcast packet */
  165         if (n->m_flags & (M_BCAST|M_MCAST))
  166                 goto freeit;
  167         /*
  168          * First, formulate icmp message
  169          */
  170         m = m_gethdr(M_DONTWAIT, MT_HEADER);
  171         if (m == NULL)
  172                 goto freeit;
  173 #ifdef MAC
  174         mac_create_mbuf_netlayer(n, m);
  175 #endif
  176         icmplen = min(oiplen + 8, oip->ip_len);
  177         if (icmplen < sizeof(struct ip))
  178                 panic("icmp_error: bad length");
  179         m->m_len = icmplen + ICMP_MINLEN;
  180         MH_ALIGN(m, m->m_len);
  181         icp = mtod(m, struct icmp *);
  182         if ((u_int)type > ICMP_MAXTYPE)
  183                 panic("icmp_error");
  184         icmpstat.icps_outhist[type]++;
  185         icp->icmp_type = type;
  186         if (type == ICMP_REDIRECT)
  187                 icp->icmp_gwaddr.s_addr = dest;
  188         else {
  189                 icp->icmp_void = 0;
  190                 /*
  191                  * The following assignments assume an overlay with the
  192                  * zeroed icmp_void field.
  193                  */
  194                 if (type == ICMP_PARAMPROB) {
  195                         icp->icmp_pptr = code;
  196                         code = 0;
  197                 } else if (type == ICMP_UNREACH &&
  198                         code == ICMP_UNREACH_NEEDFRAG && destifp) {
  199                         icp->icmp_nextmtu = htons(destifp->if_mtu);
  200                 }
  201         }
  202 
  203         icp->icmp_code = code;
  204         m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip);
  205         nip = &icp->icmp_ip;
  206 
  207         /*
  208          * Convert fields to network representation.
  209          */
  210         nip->ip_len = htons(nip->ip_len);
  211         nip->ip_off = htons(nip->ip_off);
  212 
  213         /*
  214          * Now, copy old ip header (without options)
  215          * in front of icmp message.
  216          */
  217         if (m->m_data - sizeof(struct ip) < m->m_pktdat)
  218                 panic("icmp len");
  219         m->m_data -= sizeof(struct ip);
  220         m->m_len += sizeof(struct ip);
  221         m->m_pkthdr.len = m->m_len;
  222         m->m_pkthdr.rcvif = n->m_pkthdr.rcvif;
  223         nip = mtod(m, struct ip *);
  224         bcopy((caddr_t)oip, (caddr_t)nip, sizeof(struct ip));
  225         nip->ip_len = m->m_len;
  226         nip->ip_v = IPVERSION;
  227         nip->ip_hl = 5;
  228         nip->ip_p = IPPROTO_ICMP;
  229         nip->ip_tos = 0;
  230         icmp_reflect(m);
  231 
  232 freeit:
  233         m_freem(n);
  234 }
  235 
  236 static struct sockaddr_in icmpsrc = { sizeof (struct sockaddr_in), AF_INET };
  237 static struct sockaddr_in icmpdst = { sizeof (struct sockaddr_in), AF_INET };
  238 static struct sockaddr_in icmpgw = { sizeof (struct sockaddr_in), AF_INET };
  239 
  240 /*
  241  * Process a received ICMP message.
  242  */
  243 void
  244 icmp_input(m, off)
  245         register struct mbuf *m;
  246         int off;
  247 {
  248         int hlen = off;
  249         register struct icmp *icp;
  250         register struct ip *ip = mtod(m, struct ip *);
  251         int icmplen = ip->ip_len;
  252         register int i;
  253         struct in_ifaddr *ia;
  254         void (*ctlfunc)(int, struct sockaddr *, void *);
  255         int code;
  256 
  257         /*
  258          * Locate icmp structure in mbuf, and check
  259          * that not corrupted and of at least minimum length.
  260          */
  261 #ifdef ICMPPRINTFS
  262         if (icmpprintfs) {
  263                 char buf[4 * sizeof "123"];
  264                 strcpy(buf, inet_ntoa(ip->ip_src));
  265                 printf("icmp_input from %s to %s, len %d\n",
  266                        buf, inet_ntoa(ip->ip_dst), icmplen);
  267         }
  268 #endif
  269         if (icmplen < ICMP_MINLEN) {
  270                 icmpstat.icps_tooshort++;
  271                 goto freeit;
  272         }
  273         i = hlen + min(icmplen, ICMP_ADVLENMIN);
  274         if (m->m_len < i && (m = m_pullup(m, i)) == 0)  {
  275                 icmpstat.icps_tooshort++;
  276                 return;
  277         }
  278         ip = mtod(m, struct ip *);
  279         m->m_len -= hlen;
  280         m->m_data += hlen;
  281         icp = mtod(m, struct icmp *);
  282         if (in_cksum(m, icmplen)) {
  283                 icmpstat.icps_checksum++;
  284                 goto freeit;
  285         }
  286         m->m_len += hlen;
  287         m->m_data -= hlen;
  288 
  289         if (m->m_pkthdr.rcvif && m->m_pkthdr.rcvif->if_type == IFT_FAITH) {
  290                 /*
  291                  * Deliver very specific ICMP type only.
  292                  */
  293                 switch (icp->icmp_type) {
  294                 case ICMP_UNREACH:
  295                 case ICMP_TIMXCEED:
  296                         break;
  297                 default:
  298                         goto freeit;
  299                 }
  300         }
  301 
  302 #ifdef ICMPPRINTFS
  303         if (icmpprintfs)
  304                 printf("icmp_input, type %d code %d\n", icp->icmp_type,
  305                     icp->icmp_code);
  306 #endif
  307 
  308         /*
  309          * Message type specific processing.
  310          */
  311         if (icp->icmp_type > ICMP_MAXTYPE)
  312                 goto raw;
  313         icmpstat.icps_inhist[icp->icmp_type]++;
  314         code = icp->icmp_code;
  315         switch (icp->icmp_type) {
  316 
  317         case ICMP_UNREACH:
  318                 switch (code) {
  319                         case ICMP_UNREACH_NET:
  320                         case ICMP_UNREACH_HOST:
  321                         case ICMP_UNREACH_SRCFAIL:
  322                         case ICMP_UNREACH_NET_UNKNOWN:
  323                         case ICMP_UNREACH_HOST_UNKNOWN:
  324                         case ICMP_UNREACH_ISOLATED:
  325                         case ICMP_UNREACH_TOSNET:
  326                         case ICMP_UNREACH_TOSHOST:
  327                         case ICMP_UNREACH_HOST_PRECEDENCE:
  328                         case ICMP_UNREACH_PRECEDENCE_CUTOFF:
  329                                 code = PRC_UNREACH_NET;
  330                                 break;
  331 
  332                         case ICMP_UNREACH_NEEDFRAG:
  333                                 code = PRC_MSGSIZE;
  334                                 break;
  335 
  336                         /*
  337                          * RFC 1122, Sections 3.2.2.1 and 4.2.3.9.
  338                          * Treat subcodes 2,3 as immediate RST
  339                          */
  340                         case ICMP_UNREACH_PROTOCOL:
  341                         case ICMP_UNREACH_PORT:
  342                                 code = PRC_UNREACH_PORT;
  343                                 break;
  344 
  345                         case ICMP_UNREACH_NET_PROHIB:
  346                         case ICMP_UNREACH_HOST_PROHIB:
  347                         case ICMP_UNREACH_FILTER_PROHIB:
  348                                 code = PRC_UNREACH_ADMIN_PROHIB;
  349                                 break;
  350 
  351                         default:
  352                                 goto badcode;
  353                 }
  354                 goto deliver;
  355 
  356         case ICMP_TIMXCEED:
  357                 if (code > 1)
  358                         goto badcode;
  359                 code += PRC_TIMXCEED_INTRANS;
  360                 goto deliver;
  361 
  362         case ICMP_PARAMPROB:
  363                 if (code > 1)
  364                         goto badcode;
  365                 code = PRC_PARAMPROB;
  366                 goto deliver;
  367 
  368         case ICMP_SOURCEQUENCH:
  369                 if (code)
  370                         goto badcode;
  371                 code = PRC_QUENCH;
  372         deliver:
  373                 /*
  374                  * Problem with datagram; advise higher level routines.
  375                  */
  376                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  377                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
  378                         icmpstat.icps_badlen++;
  379                         goto freeit;
  380                 }
  381                 icp->icmp_ip.ip_len = ntohs(icp->icmp_ip.ip_len);
  382                 /* Discard ICMP's in response to multicast packets */
  383                 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
  384                         goto badcode;
  385 #ifdef ICMPPRINTFS
  386                 if (icmpprintfs)
  387                         printf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
  388 #endif
  389                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  390 #if 1
  391                 /*
  392                  * MTU discovery:
  393                  * If we got a needfrag and there is a host route to the
  394                  * original destination, and the MTU is not locked, then
  395                  * set the MTU in the route to the suggested new value
  396                  * (if given) and then notify as usual.  The ULPs will
  397                  * notice that the MTU has changed and adapt accordingly.
  398                  * If no new MTU was suggested, then we guess a new one
  399                  * less than the current value.  If the new MTU is 
  400                  * unreasonably small (arbitrarily set at 296), then
  401                  * we reset the MTU to the interface value and enable the
  402                  * lock bit, indicating that we are no longer doing MTU
  403                  * discovery.
  404                  */
  405                 if (code == PRC_MSGSIZE) {
  406                         struct rtentry *rt;
  407                         int mtu;
  408 
  409                         rt = rtalloc1((struct sockaddr *)&icmpsrc, 0,
  410                                       RTF_CLONING | RTF_PRCLONING);
  411                         if (rt && (rt->rt_flags & RTF_HOST)
  412                             && !(rt->rt_rmx.rmx_locks & RTV_MTU)) {
  413                                 mtu = ntohs(icp->icmp_nextmtu);
  414                                 if (!mtu)
  415                                         mtu = ip_next_mtu(rt->rt_rmx.rmx_mtu,
  416                                                           1);
  417 #ifdef DEBUG_MTUDISC
  418                                 printf("MTU for %s reduced to %d\n",
  419                                         inet_ntoa(icmpsrc.sin_addr), mtu);
  420 #endif
  421                                 if (mtu < 296) {
  422                                         /* rt->rt_rmx.rmx_mtu =
  423                                                 rt->rt_ifp->if_mtu; */
  424                                         rt->rt_rmx.rmx_locks |= RTV_MTU;
  425                                 } else if (rt->rt_rmx.rmx_mtu > mtu) {
  426                                         rt->rt_rmx.rmx_mtu = mtu;
  427                                 }
  428                         }
  429                         if (rt)
  430                                 RTFREE(rt);
  431                 }
  432 
  433 #endif
  434                 /*
  435                  * XXX if the packet contains [IPv4 AH TCP], we can't make a
  436                  * notification to TCP layer.
  437                  */
  438                 ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput;
  439                 if (ctlfunc)
  440                         (*ctlfunc)(code, (struct sockaddr *)&icmpsrc,
  441                                    (void *)&icp->icmp_ip);
  442                 break;
  443 
  444         badcode:
  445                 icmpstat.icps_badcode++;
  446                 break;
  447 
  448         case ICMP_ECHO:
  449                 if (!icmpbmcastecho
  450                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
  451                         icmpstat.icps_bmcastecho++;
  452                         break;
  453                 }
  454                 icp->icmp_type = ICMP_ECHOREPLY;
  455                 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
  456                         goto freeit;
  457                 else
  458                         goto reflect;
  459 
  460         case ICMP_TSTAMP:
  461                 if (!icmpbmcastecho
  462                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
  463                         icmpstat.icps_bmcasttstamp++;
  464                         break;
  465                 }
  466                 if (icmplen < ICMP_TSLEN) {
  467                         icmpstat.icps_badlen++;
  468                         break;
  469                 }
  470                 icp->icmp_type = ICMP_TSTAMPREPLY;
  471                 icp->icmp_rtime = iptime();
  472                 icp->icmp_ttime = icp->icmp_rtime;      /* bogus, do later! */
  473                 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
  474                         goto freeit;
  475                 else
  476                         goto reflect;
  477 
  478         case ICMP_MASKREQ:
  479                 if (icmpmaskrepl == 0)
  480                         break;
  481                 /*
  482                  * We are not able to respond with all ones broadcast
  483                  * unless we receive it over a point-to-point interface.
  484                  */
  485                 if (icmplen < ICMP_MASKLEN)
  486                         break;
  487                 switch (ip->ip_dst.s_addr) {
  488 
  489                 case INADDR_BROADCAST:
  490                 case INADDR_ANY:
  491                         icmpdst.sin_addr = ip->ip_src;
  492                         break;
  493 
  494                 default:
  495                         icmpdst.sin_addr = ip->ip_dst;
  496                 }
  497                 ia = (struct in_ifaddr *)ifaof_ifpforaddr(
  498                             (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
  499                 if (ia == 0)
  500                         break;
  501                 if (ia->ia_ifp == 0)
  502                         break;
  503                 icp->icmp_type = ICMP_MASKREPLY;
  504                 if (icmpmaskfake == 0)
  505                         icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr;
  506                 else
  507                         icp->icmp_mask = icmpmaskfake;
  508                 if (ip->ip_src.s_addr == 0) {
  509                         if (ia->ia_ifp->if_flags & IFF_BROADCAST)
  510                             ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr;
  511                         else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT)
  512                             ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr;
  513                 }
  514 reflect:
  515                 ip->ip_len += hlen;     /* since ip_input deducts this */
  516                 icmpstat.icps_reflect++;
  517                 icmpstat.icps_outhist[icp->icmp_type]++;
  518                 icmp_reflect(m);
  519                 return;
  520 
  521         case ICMP_REDIRECT:
  522                 if (log_redirect) {
  523                         u_long src, dst, gw;
  524 
  525                         src = ntohl(ip->ip_src.s_addr);
  526                         dst = ntohl(icp->icmp_ip.ip_dst.s_addr);
  527                         gw = ntohl(icp->icmp_gwaddr.s_addr);
  528                         printf("icmp redirect from %d.%d.%d.%d: "
  529                                "%d.%d.%d.%d => %d.%d.%d.%d\n",
  530                                (int)(src >> 24), (int)((src >> 16) & 0xff),
  531                                (int)((src >> 8) & 0xff), (int)(src & 0xff),
  532                                (int)(dst >> 24), (int)((dst >> 16) & 0xff),
  533                                (int)((dst >> 8) & 0xff), (int)(dst & 0xff),
  534                                (int)(gw >> 24), (int)((gw >> 16) & 0xff),
  535                                (int)((gw >> 8) & 0xff), (int)(gw & 0xff));
  536                 }
  537                 if (drop_redirect)
  538                         break;
  539                 if (code > 3)
  540                         goto badcode;
  541                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  542                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
  543                         icmpstat.icps_badlen++;
  544                         break;
  545                 }
  546                 /*
  547                  * Short circuit routing redirects to force
  548                  * immediate change in the kernel's routing
  549                  * tables.  The message is also handed to anyone
  550                  * listening on a raw socket (e.g. the routing
  551                  * daemon for use in updating its tables).
  552                  */
  553                 icmpgw.sin_addr = ip->ip_src;
  554                 icmpdst.sin_addr = icp->icmp_gwaddr;
  555 #ifdef  ICMPPRINTFS
  556                 if (icmpprintfs) {
  557                         char buf[4 * sizeof "123"];
  558                         strcpy(buf, inet_ntoa(icp->icmp_ip.ip_dst));
  559 
  560                         printf("redirect dst %s to %s\n",
  561                                buf, inet_ntoa(icp->icmp_gwaddr));
  562                 }
  563 #endif
  564                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  565                 rtredirect((struct sockaddr *)&icmpsrc,
  566                   (struct sockaddr *)&icmpdst,
  567                   (struct sockaddr *)0, RTF_GATEWAY | RTF_HOST,
  568                   (struct sockaddr *)&icmpgw, (struct rtentry **)0);
  569                 pfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
  570 #ifdef IPSEC
  571                 key_sa_routechange((struct sockaddr *)&icmpsrc);
  572 #endif
  573                 break;
  574 
  575         /*
  576          * No kernel processing for the following;
  577          * just fall through to send to raw listener.
  578          */
  579         case ICMP_ECHOREPLY:
  580         case ICMP_ROUTERADVERT:
  581         case ICMP_ROUTERSOLICIT:
  582         case ICMP_TSTAMPREPLY:
  583         case ICMP_IREQREPLY:
  584         case ICMP_MASKREPLY:
  585         default:
  586                 break;
  587         }
  588 
  589 raw:
  590         rip_input(m, off);
  591         return;
  592 
  593 freeit:
  594         m_freem(m);
  595 }
  596 
  597 /*
  598  * Reflect the ip packet back to the source
  599  */
  600 static void
  601 icmp_reflect(m)
  602         struct mbuf *m;
  603 {
  604         struct ip *ip = mtod(m, struct ip *);
  605         struct ifaddr *ifa;
  606         struct in_ifaddr *ia;
  607         struct in_addr t;
  608         struct mbuf *opts = 0;
  609         int optlen = (ip->ip_hl << 2) - sizeof(struct ip);
  610         struct route *ro = NULL, rt;
  611 
  612         if (!in_canforward(ip->ip_src) &&
  613             ((ntohl(ip->ip_src.s_addr) & IN_CLASSA_NET) !=
  614              (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))) {
  615                 m_freem(m);     /* Bad return address */
  616                 icmpstat.icps_badaddr++;
  617                 goto done;      /* Ip_output() will check for broadcast */
  618         }
  619         t = ip->ip_dst;
  620         ip->ip_dst = ip->ip_src;
  621         ro = &rt;
  622         bzero(ro, sizeof(*ro));
  623         /*
  624          * If the incoming packet was addressed directly to us,
  625          * use dst as the src for the reply.  Otherwise (broadcast
  626          * or anonymous), use the address which corresponds
  627          * to the incoming interface.
  628          */
  629         LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash)
  630                 if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr)
  631                         goto match;
  632         if (m->m_pkthdr.rcvif != NULL &&
  633             m->m_pkthdr.rcvif->if_flags & IFF_BROADCAST) {
  634                 TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
  635                         if (ifa->ifa_addr->sa_family != AF_INET)
  636                                 continue;
  637                         ia = ifatoia(ifa);
  638                         if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
  639                             t.s_addr)
  640                                 goto match;
  641                 }
  642         }
  643         ia = ip_rtaddr(ip->ip_dst, ro);
  644         /* We need a route to do anything useful. */
  645         if (ia == NULL) {
  646                 m_freem(m);
  647                 icmpstat.icps_noroute++;
  648                 goto done;
  649         }
  650 match:
  651         t = IA_SIN(ia)->sin_addr;
  652         ip->ip_src = t;
  653         ip->ip_ttl = ip_defttl;
  654 
  655         if (optlen > 0) {
  656                 register u_char *cp;
  657                 int opt, cnt;
  658                 u_int len;
  659 
  660                 /*
  661                  * Retrieve any source routing from the incoming packet;
  662                  * add on any record-route or timestamp options.
  663                  */
  664                 cp = (u_char *) (ip + 1);
  665                 if ((opts = ip_srcroute()) == 0 &&
  666                     (opts = m_gethdr(M_DONTWAIT, MT_HEADER))) {
  667                         opts->m_len = sizeof(struct in_addr);
  668                         mtod(opts, struct in_addr *)->s_addr = 0;
  669                 }
  670                 if (opts) {
  671 #ifdef ICMPPRINTFS
  672                     if (icmpprintfs)
  673                             printf("icmp_reflect optlen %d rt %d => ",
  674                                 optlen, opts->m_len);
  675 #endif
  676                     for (cnt = optlen; cnt > 0; cnt -= len, cp += len) {
  677                             opt = cp[IPOPT_OPTVAL];
  678                             if (opt == IPOPT_EOL)
  679                                     break;
  680                             if (opt == IPOPT_NOP)
  681                                     len = 1;
  682                             else {
  683                                     if (cnt < IPOPT_OLEN + sizeof(*cp))
  684                                             break;
  685                                     len = cp[IPOPT_OLEN];
  686                                     if (len < IPOPT_OLEN + sizeof(*cp) ||
  687                                         len > cnt)
  688                                             break;
  689                             }
  690                             /*
  691                              * Should check for overflow, but it "can't happen"
  692                              */
  693                             if (opt == IPOPT_RR || opt == IPOPT_TS ||
  694                                 opt == IPOPT_SECURITY) {
  695                                     bcopy((caddr_t)cp,
  696                                         mtod(opts, caddr_t) + opts->m_len, len);
  697                                     opts->m_len += len;
  698                             }
  699                     }
  700                     /* Terminate & pad, if necessary */
  701                     cnt = opts->m_len % 4;
  702                     if (cnt) {
  703                             for (; cnt < 4; cnt++) {
  704                                     *(mtod(opts, caddr_t) + opts->m_len) =
  705                                         IPOPT_EOL;
  706                                     opts->m_len++;
  707                             }
  708                     }
  709 #ifdef ICMPPRINTFS
  710                     if (icmpprintfs)
  711                             printf("%d\n", opts->m_len);
  712 #endif
  713                 }
  714                 /*
  715                  * Now strip out original options by copying rest of first
  716                  * mbuf's data back, and adjust the IP length.
  717                  */
  718                 ip->ip_len -= optlen;
  719                 ip->ip_v = IPVERSION;
  720                 ip->ip_hl = 5;
  721                 m->m_len -= optlen;
  722                 if (m->m_flags & M_PKTHDR)
  723                         m->m_pkthdr.len -= optlen;
  724                 optlen += sizeof(struct ip);
  725                 bcopy((caddr_t)ip + optlen, (caddr_t)(ip + 1),
  726                          (unsigned)(m->m_len - sizeof(struct ip)));
  727         }
  728         m->m_flags &= ~(M_BCAST|M_MCAST);
  729         icmp_send(m, opts, ro);
  730 done:
  731         if (opts)
  732                 (void)m_free(opts);
  733         if (ro && ro->ro_rt)
  734                 RTFREE(ro->ro_rt);
  735 }
  736 
  737 /*
  738  * Send an icmp packet back to the ip level,
  739  * after supplying a checksum.
  740  */
  741 static void
  742 icmp_send(m, opts, rt)
  743         register struct mbuf *m;
  744         struct mbuf *opts;
  745         struct route *rt;
  746 {
  747         register struct ip *ip = mtod(m, struct ip *);
  748         register int hlen;
  749         register struct icmp *icp;
  750 
  751         hlen = ip->ip_hl << 2;
  752         m->m_data += hlen;
  753         m->m_len -= hlen;
  754         icp = mtod(m, struct icmp *);
  755         icp->icmp_cksum = 0;
  756         icp->icmp_cksum = in_cksum(m, ip->ip_len - hlen);
  757         m->m_data -= hlen;
  758         m->m_len += hlen;
  759         m->m_pkthdr.rcvif = (struct ifnet *)0;
  760 #ifdef ICMPPRINTFS
  761         if (icmpprintfs) {
  762                 char buf[4 * sizeof "123"];
  763                 strcpy(buf, inet_ntoa(ip->ip_dst));
  764                 printf("icmp_send dst %s src %s\n",
  765                        buf, inet_ntoa(ip->ip_src));
  766         }
  767 #endif
  768         (void) ip_output(m, opts, rt, 0, NULL, NULL);
  769 }
  770 
  771 n_time
  772 iptime()
  773 {
  774         struct timeval atv;
  775         u_long t;
  776 
  777         getmicrotime(&atv);
  778         t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000;
  779         return (htonl(t));
  780 }
  781 
  782 #if 1
  783 /*
  784  * Return the next larger or smaller MTU plateau (table from RFC 1191)
  785  * given current value MTU.  If DIR is less than zero, a larger plateau
  786  * is returned; otherwise, a smaller value is returned.
  787  */
  788 static int
  789 ip_next_mtu(mtu, dir)
  790         int mtu;
  791         int dir;
  792 {
  793         static int mtutab[] = {
  794                 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1006, 508, 296,
  795                 68, 0
  796         };
  797         int i;
  798 
  799         for (i = 0; i < (sizeof mtutab) / (sizeof mtutab[0]); i++) {
  800                 if (mtu >= mtutab[i])
  801                         break;
  802         }
  803 
  804         if (dir < 0) {
  805                 if (i == 0) {
  806                         return 0;
  807                 } else {
  808                         return mtutab[i - 1];
  809                 }
  810         } else {
  811                 if (mtutab[i] == 0) {
  812                         return 0;
  813                 } else if(mtu > mtutab[i]) {
  814                         return mtutab[i];
  815                 } else {
  816                         return mtutab[i + 1];
  817                 }
  818         }
  819 }
  820 #endif
  821 
  822 
  823 /*
  824  * badport_bandlim() - check for ICMP bandwidth limit
  825  *
  826  *      Return 0 if it is ok to send an ICMP error response, -1 if we have
  827  *      hit our bandwidth limit and it is not ok.  
  828  *
  829  *      If icmplim is <= 0, the feature is disabled and 0 is returned.
  830  *
  831  *      For now we separate the TCP and UDP subsystems w/ different 'which'
  832  *      values.  We may eventually remove this separation (and simplify the
  833  *      code further).
  834  *
  835  *      Note that the printing of the error message is delayed so we can
  836  *      properly print the icmp error rate that the system was trying to do
  837  *      (i.e. 22000/100 pps, etc...).  This can cause long delays in printing
  838  *      the 'final' error, but it doesn't make sense to solve the printing 
  839  *      delay with more complex code.
  840  */
  841 
  842 int
  843 badport_bandlim(int which)
  844 {
  845 #define N(a)    (sizeof (a) / sizeof (a[0]))
  846         static struct rate {
  847                 const char      *type;
  848                 struct timeval  lasttime;
  849                 int             curpps;;
  850         } rates[BANDLIM_MAX+1] = {
  851                 { "icmp unreach response" },
  852                 { "icmp ping response" },
  853                 { "icmp tstamp response" },
  854                 { "closed port RST response" },
  855                 { "open port RST response" }
  856         };
  857 
  858         /*
  859          * Return ok status if feature disabled or argument out of range.
  860          */
  861         if (icmplim > 0 && (u_int) which < N(rates)) {
  862                 struct rate *r = &rates[which];
  863                 int opps = r->curpps;
  864 
  865                 if (!ppsratecheck(&r->lasttime, &r->curpps, icmplim))
  866                         return -1;      /* discard packet */
  867                 /*
  868                  * If we've dropped below the threshold after having
  869                  * rate-limited traffic print the message.  This preserves
  870                  * the previous behaviour at the expense of added complexity.
  871                  */
  872                 if (icmplim_output && opps > icmplim)
  873                         printf("Limiting %s from %d to %d packets/sec\n",
  874                                 r->type, opps, icmplim);
  875         }
  876         return 0;                       /* okay to send packet */
  877 #undef N
  878 }

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