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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  * 4. 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  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD: releng/7.4/sys/netinet/ip_icmp.c 211543 2010-08-21 11:02:18Z andre $");
   34 
   35 #include "opt_ipsec.h"
   36 #include "opt_mac.h"
   37 
   38 #include <sys/param.h>
   39 #include <sys/systm.h>
   40 #include <sys/mbuf.h>
   41 #include <sys/protosw.h>
   42 #include <sys/socket.h>
   43 #include <sys/time.h>
   44 #include <sys/kernel.h>
   45 #include <sys/sysctl.h>
   46 #include <sys/syslog.h>
   47 
   48 #include <net/if.h>
   49 #include <net/if_types.h>
   50 #include <net/route.h>
   51 
   52 #include <netinet/in.h>
   53 #include <netinet/in_pcb.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/ip_options.h>
   60 #include <netinet/tcp.h>
   61 #include <netinet/tcp_var.h>
   62 #include <netinet/tcpip.h>
   63 #include <netinet/icmp_var.h>
   64 
   65 #ifdef IPSEC
   66 #include <netipsec/ipsec.h>
   67 #include <netipsec/key.h>
   68 #endif
   69 
   70 #include <machine/in_cksum.h>
   71 
   72 #include <security/mac/mac_framework.h>
   73 
   74 /*
   75  * ICMP routines: error generation, receive packet processing, and
   76  * routines to turnaround packets back to the originator, and
   77  * host table maintenance routines.
   78  */
   79 
   80 struct  icmpstat icmpstat;
   81 SYSCTL_STRUCT(_net_inet_icmp, ICMPCTL_STATS, stats, CTLFLAG_RW,
   82         &icmpstat, icmpstat, "");
   83 
   84 static int      icmpmaskrepl = 0;
   85 SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_RW,
   86         &icmpmaskrepl, 0, "Reply to ICMP Address Mask Request packets.");
   87 
   88 static u_int    icmpmaskfake = 0;
   89 SYSCTL_UINT(_net_inet_icmp, OID_AUTO, maskfake, CTLFLAG_RW,
   90         &icmpmaskfake, 0, "Fake reply to ICMP Address Mask Request packets.");
   91 
   92 static int      drop_redirect = 0;
   93 SYSCTL_INT(_net_inet_icmp, OID_AUTO, drop_redirect, CTLFLAG_RW,
   94         &drop_redirect, 0, "Ignore ICMP redirects");
   95 
   96 static int      log_redirect = 0;
   97 SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_RW,
   98         &log_redirect, 0, "Log ICMP redirects to the console");
   99 
  100 static int      icmplim = 200;
  101 SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RW,
  102         &icmplim, 0, "Maximum number of ICMP responses per second");
  103 
  104 static int      icmplim_output = 1;
  105 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_RW,
  106         &icmplim_output, 0, "Enable rate limiting of ICMP responses");
  107 
  108 static char     reply_src[IFNAMSIZ];
  109 SYSCTL_STRING(_net_inet_icmp, OID_AUTO, reply_src, CTLFLAG_RW,
  110         &reply_src, IFNAMSIZ, "icmp reply source for non-local packets.");
  111 
  112 static int      icmp_rfi = 0;
  113 SYSCTL_INT(_net_inet_icmp, OID_AUTO, reply_from_interface, CTLFLAG_RW,
  114         &icmp_rfi, 0, "ICMP reply from incoming interface for "
  115         "non-local packets");
  116 
  117 static int      icmp_quotelen = 8;
  118 SYSCTL_INT(_net_inet_icmp, OID_AUTO, quotelen, CTLFLAG_RW,
  119         &icmp_quotelen, 0, "Number of bytes from original packet to "
  120         "quote in ICMP reply");
  121 
  122 /*
  123  * ICMP broadcast echo sysctl
  124  */
  125 
  126 static int      icmpbmcastecho = 0;
  127 SYSCTL_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_RW,
  128         &icmpbmcastecho, 0, "");
  129 
  130 
  131 #ifdef ICMPPRINTFS
  132 int     icmpprintfs = 0;
  133 #endif
  134 
  135 static void     icmp_reflect(struct mbuf *);
  136 static void     icmp_send(struct mbuf *, struct mbuf *);
  137 
  138 extern  struct protosw inetsw[];
  139 
  140 /*
  141  * Generate an error packet of type error
  142  * in response to bad packet ip.
  143  */
  144 void
  145 icmp_error(struct mbuf *n, int type, int code, uint32_t dest, int mtu)
  146 {
  147         register struct ip *oip = mtod(n, struct ip *), *nip;
  148         register unsigned oiphlen = oip->ip_hl << 2;
  149         register struct icmp *icp;
  150         register struct mbuf *m;
  151         unsigned icmplen, icmpelen, nlen;
  152 
  153         KASSERT((u_int)type <= ICMP_MAXTYPE, ("%s: illegal ICMP type", __func__));
  154 #ifdef ICMPPRINTFS
  155         if (icmpprintfs)
  156                 printf("icmp_error(%p, %x, %d)\n", oip, type, code);
  157 #endif
  158         if (type != ICMP_REDIRECT)
  159                 icmpstat.icps_error++;
  160         /*
  161          * Don't send error:
  162          *  if the original packet was encrypted.
  163          *  if not the first fragment of message.
  164          *  in response to a multicast or broadcast packet.
  165          *  if the old packet protocol was an ICMP error message.
  166          */
  167         if (n->m_flags & M_DECRYPTED)
  168                 goto freeit;
  169         if (oip->ip_off & ~(IP_MF|IP_DF))
  170                 goto freeit;
  171         if (n->m_flags & (M_BCAST|M_MCAST))
  172                 goto freeit;
  173         if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
  174           n->m_len >= oiphlen + ICMP_MINLEN &&
  175           !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip + oiphlen))->icmp_type)) {
  176                 icmpstat.icps_oldicmp++;
  177                 goto freeit;
  178         }
  179         /* Drop if IP header plus 8 bytes is not contignous in first mbuf. */
  180         if (oiphlen + 8 > n->m_len)
  181                 goto freeit;
  182         /*
  183          * Calculate length to quote from original packet and
  184          * prevent the ICMP mbuf from overflowing.
  185          * Unfortunatly this is non-trivial since ip_forward()
  186          * sends us truncated packets.
  187          */
  188         nlen = m_length(n, NULL);
  189         if (oip->ip_p == IPPROTO_TCP) {
  190                 struct tcphdr *th;
  191                 int tcphlen;
  192 
  193                 if (oiphlen + sizeof(struct tcphdr) > n->m_len &&
  194                     n->m_next == NULL)
  195                         goto stdreply;
  196                 if (n->m_len < oiphlen + sizeof(struct tcphdr) &&
  197                     ((n = m_pullup(n, oiphlen + sizeof(struct tcphdr))) == NULL))
  198                         goto freeit;
  199                 th = (struct tcphdr *)((caddr_t)oip + oiphlen);
  200                 tcphlen = th->th_off << 2;
  201                 if (tcphlen < sizeof(struct tcphdr))
  202                         goto freeit;
  203                 if (oip->ip_len < oiphlen + tcphlen)
  204                         goto freeit;
  205                 if (oiphlen + tcphlen > n->m_len && n->m_next == NULL)
  206                         goto stdreply;
  207                 if (n->m_len < oiphlen + tcphlen && 
  208                     ((n = m_pullup(n, oiphlen + tcphlen)) == NULL))
  209                         goto freeit;
  210                 icmpelen = max(tcphlen, min(icmp_quotelen, oip->ip_len - oiphlen));
  211         } else
  212 stdreply:       icmpelen = max(8, min(icmp_quotelen, oip->ip_len - oiphlen));
  213 
  214         icmplen = min(oiphlen + icmpelen, nlen);
  215         if (icmplen < sizeof(struct ip))
  216                 goto freeit;
  217 
  218         if (MHLEN > sizeof(struct ip) + ICMP_MINLEN + icmplen)
  219                 m = m_gethdr(M_DONTWAIT, MT_DATA);
  220         else
  221                 m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
  222         if (m == NULL)
  223                 goto freeit;
  224 #ifdef MAC
  225         mac_create_mbuf_netlayer(n, m);
  226 #endif
  227         icmplen = min(icmplen, M_TRAILINGSPACE(m) - sizeof(struct ip) - ICMP_MINLEN);
  228         m_align(m, ICMP_MINLEN + icmplen);
  229         m->m_len = ICMP_MINLEN + icmplen;
  230 
  231         /* XXX MRT  make the outgoing packet use the same FIB
  232          * that was associated with the incoming packet
  233          */
  234         M_SETFIB(m, M_GETFIB(n));
  235         icp = mtod(m, struct icmp *);
  236         icmpstat.icps_outhist[type]++;
  237         icp->icmp_type = type;
  238         if (type == ICMP_REDIRECT)
  239                 icp->icmp_gwaddr.s_addr = dest;
  240         else {
  241                 icp->icmp_void = 0;
  242                 /*
  243                  * The following assignments assume an overlay with the
  244                  * just zeroed icmp_void field.
  245                  */
  246                 if (type == ICMP_PARAMPROB) {
  247                         icp->icmp_pptr = code;
  248                         code = 0;
  249                 } else if (type == ICMP_UNREACH &&
  250                         code == ICMP_UNREACH_NEEDFRAG && mtu) {
  251                         icp->icmp_nextmtu = htons(mtu);
  252                 }
  253         }
  254         icp->icmp_code = code;
  255 
  256         /*
  257          * Copy the quotation into ICMP message and
  258          * convert quoted IP header back to network representation.
  259          */
  260         m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip);
  261         nip = &icp->icmp_ip;
  262         nip->ip_len = htons(nip->ip_len);
  263         nip->ip_off = htons(nip->ip_off);
  264 
  265         /*
  266          * Set up ICMP message mbuf and copy old IP header (without options
  267          * in front of ICMP message.
  268          * If the original mbuf was meant to bypass the firewall, the error
  269          * reply should bypass as well.
  270          */
  271         m->m_flags |= n->m_flags & M_SKIP_FIREWALL;
  272         m->m_data -= sizeof(struct ip);
  273         m->m_len += sizeof(struct ip);
  274         m->m_pkthdr.len = m->m_len;
  275         m->m_pkthdr.rcvif = n->m_pkthdr.rcvif;
  276         nip = mtod(m, struct ip *);
  277         bcopy((caddr_t)oip, (caddr_t)nip, sizeof(struct ip));
  278         nip->ip_len = m->m_len;
  279         nip->ip_v = IPVERSION;
  280         nip->ip_hl = 5;
  281         nip->ip_p = IPPROTO_ICMP;
  282         nip->ip_tos = 0;
  283         icmp_reflect(m);
  284 
  285 freeit:
  286         m_freem(n);
  287 }
  288 
  289 /*
  290  * Process a received ICMP message.
  291  */
  292 void
  293 icmp_input(struct mbuf *m, int off)
  294 {
  295         struct icmp *icp;
  296         struct in_ifaddr *ia;
  297         struct ip *ip = mtod(m, struct ip *);
  298         struct sockaddr_in icmpsrc, icmpdst, icmpgw;
  299         int hlen = off;
  300         int icmplen = ip->ip_len;
  301         int i, code;
  302         void (*ctlfunc)(int, struct sockaddr *, void *);
  303         int fibnum;
  304 
  305         /*
  306          * Locate icmp structure in mbuf, and check
  307          * that not corrupted and of at least minimum length.
  308          */
  309 #ifdef ICMPPRINTFS
  310         if (icmpprintfs) {
  311                 char buf[4 * sizeof "123"];
  312                 strcpy(buf, inet_ntoa(ip->ip_src));
  313                 printf("icmp_input from %s to %s, len %d\n",
  314                        buf, inet_ntoa(ip->ip_dst), icmplen);
  315         }
  316 #endif
  317         if (icmplen < ICMP_MINLEN) {
  318                 icmpstat.icps_tooshort++;
  319                 goto freeit;
  320         }
  321         i = hlen + min(icmplen, ICMP_ADVLENMIN);
  322         if (m->m_len < i && (m = m_pullup(m, i)) == 0)  {
  323                 icmpstat.icps_tooshort++;
  324                 return;
  325         }
  326         ip = mtod(m, struct ip *);
  327         m->m_len -= hlen;
  328         m->m_data += hlen;
  329         icp = mtod(m, struct icmp *);
  330         if (in_cksum(m, icmplen)) {
  331                 icmpstat.icps_checksum++;
  332                 goto freeit;
  333         }
  334         m->m_len += hlen;
  335         m->m_data -= hlen;
  336 
  337         if (m->m_pkthdr.rcvif && m->m_pkthdr.rcvif->if_type == IFT_FAITH) {
  338                 /*
  339                  * Deliver very specific ICMP type only.
  340                  */
  341                 switch (icp->icmp_type) {
  342                 case ICMP_UNREACH:
  343                 case ICMP_TIMXCEED:
  344                         break;
  345                 default:
  346                         goto freeit;
  347                 }
  348         }
  349 
  350 #ifdef ICMPPRINTFS
  351         if (icmpprintfs)
  352                 printf("icmp_input, type %d code %d\n", icp->icmp_type,
  353                     icp->icmp_code);
  354 #endif
  355 
  356         /*
  357          * Message type specific processing.
  358          */
  359         if (icp->icmp_type > ICMP_MAXTYPE)
  360                 goto raw;
  361 
  362         /* Initialize */
  363         bzero(&icmpsrc, sizeof(icmpsrc));
  364         icmpsrc.sin_len = sizeof(struct sockaddr_in);
  365         icmpsrc.sin_family = AF_INET;
  366         bzero(&icmpdst, sizeof(icmpdst));
  367         icmpdst.sin_len = sizeof(struct sockaddr_in);
  368         icmpdst.sin_family = AF_INET;
  369         bzero(&icmpgw, sizeof(icmpgw));
  370         icmpgw.sin_len = sizeof(struct sockaddr_in);
  371         icmpgw.sin_family = AF_INET;
  372 
  373         icmpstat.icps_inhist[icp->icmp_type]++;
  374         code = icp->icmp_code;
  375         switch (icp->icmp_type) {
  376 
  377         case ICMP_UNREACH:
  378                 switch (code) {
  379                         case ICMP_UNREACH_NET:
  380                         case ICMP_UNREACH_HOST:
  381                         case ICMP_UNREACH_SRCFAIL:
  382                         case ICMP_UNREACH_NET_UNKNOWN:
  383                         case ICMP_UNREACH_HOST_UNKNOWN:
  384                         case ICMP_UNREACH_ISOLATED:
  385                         case ICMP_UNREACH_TOSNET:
  386                         case ICMP_UNREACH_TOSHOST:
  387                         case ICMP_UNREACH_HOST_PRECEDENCE:
  388                         case ICMP_UNREACH_PRECEDENCE_CUTOFF:
  389                                 code = PRC_UNREACH_NET;
  390                                 break;
  391 
  392                         case ICMP_UNREACH_NEEDFRAG:
  393                                 code = PRC_MSGSIZE;
  394                                 break;
  395 
  396                         /*
  397                          * RFC 1122, Sections 3.2.2.1 and 4.2.3.9.
  398                          * Treat subcodes 2,3 as immediate RST
  399                          */
  400                         case ICMP_UNREACH_PROTOCOL:
  401                         case ICMP_UNREACH_PORT:
  402                                 code = PRC_UNREACH_PORT;
  403                                 break;
  404 
  405                         case ICMP_UNREACH_NET_PROHIB:
  406                         case ICMP_UNREACH_HOST_PROHIB:
  407                         case ICMP_UNREACH_FILTER_PROHIB:
  408                                 code = PRC_UNREACH_ADMIN_PROHIB;
  409                                 break;
  410 
  411                         default:
  412                                 goto badcode;
  413                 }
  414                 goto deliver;
  415 
  416         case ICMP_TIMXCEED:
  417                 if (code > 1)
  418                         goto badcode;
  419                 code += PRC_TIMXCEED_INTRANS;
  420                 goto deliver;
  421 
  422         case ICMP_PARAMPROB:
  423                 if (code > 1)
  424                         goto badcode;
  425                 code = PRC_PARAMPROB;
  426                 goto deliver;
  427 
  428         case ICMP_SOURCEQUENCH:
  429                 if (code)
  430                         goto badcode;
  431                 code = PRC_QUENCH;
  432         deliver:
  433                 /*
  434                  * Problem with datagram; advise higher level routines.
  435                  */
  436                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  437                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
  438                         icmpstat.icps_badlen++;
  439                         goto freeit;
  440                 }
  441                 icp->icmp_ip.ip_len = ntohs(icp->icmp_ip.ip_len);
  442                 /* Discard ICMP's in response to multicast packets */
  443                 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
  444                         goto badcode;
  445 #ifdef ICMPPRINTFS
  446                 if (icmpprintfs)
  447                         printf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
  448 #endif
  449                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  450                 /*
  451                  * XXX if the packet contains [IPv4 AH TCP], we can't make a
  452                  * notification to TCP layer.
  453                  */
  454                 ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput;
  455                 if (ctlfunc)
  456                         (*ctlfunc)(code, (struct sockaddr *)&icmpsrc,
  457                                    (void *)&icp->icmp_ip);
  458                 break;
  459 
  460         badcode:
  461                 icmpstat.icps_badcode++;
  462                 break;
  463 
  464         case ICMP_ECHO:
  465                 if (!icmpbmcastecho
  466                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
  467                         icmpstat.icps_bmcastecho++;
  468                         break;
  469                 }
  470                 icp->icmp_type = ICMP_ECHOREPLY;
  471                 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
  472                         goto freeit;
  473                 else
  474                         goto reflect;
  475 
  476         case ICMP_TSTAMP:
  477                 if (!icmpbmcastecho
  478                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
  479                         icmpstat.icps_bmcasttstamp++;
  480                         break;
  481                 }
  482                 if (icmplen < ICMP_TSLEN) {
  483                         icmpstat.icps_badlen++;
  484                         break;
  485                 }
  486                 icp->icmp_type = ICMP_TSTAMPREPLY;
  487                 icp->icmp_rtime = iptime();
  488                 icp->icmp_ttime = icp->icmp_rtime;      /* bogus, do later! */
  489                 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
  490                         goto freeit;
  491                 else
  492                         goto reflect;
  493 
  494         case ICMP_MASKREQ:
  495                 if (icmpmaskrepl == 0)
  496                         break;
  497                 /*
  498                  * We are not able to respond with all ones broadcast
  499                  * unless we receive it over a point-to-point interface.
  500                  */
  501                 if (icmplen < ICMP_MASKLEN)
  502                         break;
  503                 switch (ip->ip_dst.s_addr) {
  504 
  505                 case INADDR_BROADCAST:
  506                 case INADDR_ANY:
  507                         icmpdst.sin_addr = ip->ip_src;
  508                         break;
  509 
  510                 default:
  511                         icmpdst.sin_addr = ip->ip_dst;
  512                 }
  513                 ia = (struct in_ifaddr *)ifaof_ifpforaddr(
  514                             (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
  515                 if (ia == 0)
  516                         break;
  517                 if (ia->ia_ifp == 0)
  518                         break;
  519                 icp->icmp_type = ICMP_MASKREPLY;
  520                 if (icmpmaskfake == 0)
  521                         icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr;
  522                 else
  523                         icp->icmp_mask = icmpmaskfake;
  524                 if (ip->ip_src.s_addr == 0) {
  525                         if (ia->ia_ifp->if_flags & IFF_BROADCAST)
  526                             ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr;
  527                         else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT)
  528                             ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr;
  529                 }
  530 reflect:
  531                 ip->ip_len += hlen;     /* since ip_input deducts this */
  532                 icmpstat.icps_reflect++;
  533                 icmpstat.icps_outhist[icp->icmp_type]++;
  534                 icmp_reflect(m);
  535                 return;
  536 
  537         case ICMP_REDIRECT:
  538                 if (log_redirect) {
  539                         u_long src, dst, gw;
  540 
  541                         src = ntohl(ip->ip_src.s_addr);
  542                         dst = ntohl(icp->icmp_ip.ip_dst.s_addr);
  543                         gw = ntohl(icp->icmp_gwaddr.s_addr);
  544                         printf("icmp redirect from %d.%d.%d.%d: "
  545                                "%d.%d.%d.%d => %d.%d.%d.%d\n",
  546                                (int)(src >> 24), (int)((src >> 16) & 0xff),
  547                                (int)((src >> 8) & 0xff), (int)(src & 0xff),
  548                                (int)(dst >> 24), (int)((dst >> 16) & 0xff),
  549                                (int)((dst >> 8) & 0xff), (int)(dst & 0xff),
  550                                (int)(gw >> 24), (int)((gw >> 16) & 0xff),
  551                                (int)((gw >> 8) & 0xff), (int)(gw & 0xff));
  552                 }
  553                 /*
  554                  * RFC1812 says we must ignore ICMP redirects if we
  555                  * are acting as router.
  556                  */
  557                 if (drop_redirect || ipforwarding)
  558                         break;
  559                 if (code > 3)
  560                         goto badcode;
  561                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  562                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
  563                         icmpstat.icps_badlen++;
  564                         break;
  565                 }
  566                 /*
  567                  * Short circuit routing redirects to force
  568                  * immediate change in the kernel's routing
  569                  * tables.  The message is also handed to anyone
  570                  * listening on a raw socket (e.g. the routing
  571                  * daemon for use in updating its tables).
  572                  */
  573                 icmpgw.sin_addr = ip->ip_src;
  574                 icmpdst.sin_addr = icp->icmp_gwaddr;
  575 #ifdef  ICMPPRINTFS
  576                 if (icmpprintfs) {
  577                         char buf[4 * sizeof "123"];
  578                         strcpy(buf, inet_ntoa(icp->icmp_ip.ip_dst));
  579 
  580                         printf("redirect dst %s to %s\n",
  581                                buf, inet_ntoa(icp->icmp_gwaddr));
  582                 }
  583 #endif
  584                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  585                 for ( fibnum = 0; fibnum < rt_numfibs; fibnum++) {
  586                         in_rtredirect((struct sockaddr *)&icmpsrc,
  587                           (struct sockaddr *)&icmpdst,
  588                           (struct sockaddr *)0, RTF_GATEWAY | RTF_HOST,
  589                           (struct sockaddr *)&icmpgw, fibnum);
  590                 }
  591                 pfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
  592 #ifdef IPSEC
  593                 key_sa_routechange((struct sockaddr *)&icmpsrc);
  594 #endif
  595                 break;
  596 
  597         /*
  598          * No kernel processing for the following;
  599          * just fall through to send to raw listener.
  600          */
  601         case ICMP_ECHOREPLY:
  602         case ICMP_ROUTERADVERT:
  603         case ICMP_ROUTERSOLICIT:
  604         case ICMP_TSTAMPREPLY:
  605         case ICMP_IREQREPLY:
  606         case ICMP_MASKREPLY:
  607         default:
  608                 break;
  609         }
  610 
  611 raw:
  612         rip_input(m, off);
  613         return;
  614 
  615 freeit:
  616         m_freem(m);
  617 }
  618 
  619 /*
  620  * Reflect the ip packet back to the source
  621  */
  622 static void
  623 icmp_reflect(struct mbuf *m)
  624 {
  625         struct ip *ip = mtod(m, struct ip *);
  626         struct ifaddr *ifa;
  627         struct ifnet *ifn;
  628         struct in_ifaddr *ia;
  629         struct in_addr t;
  630         struct mbuf *opts = 0;
  631         int optlen = (ip->ip_hl << 2) - sizeof(struct ip);
  632 
  633         if (IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
  634             IN_EXPERIMENTAL(ntohl(ip->ip_src.s_addr)) ||
  635             IN_ZERONET(ntohl(ip->ip_src.s_addr)) ) {
  636                 m_freem(m);     /* Bad return address */
  637                 icmpstat.icps_badaddr++;
  638                 goto done;      /* Ip_output() will check for broadcast */
  639         }
  640 
  641         t = ip->ip_dst;
  642         ip->ip_dst = ip->ip_src;
  643 
  644         /*
  645          * Source selection for ICMP replies:
  646          *
  647          * If the incoming packet was addressed directly to one of our
  648          * own addresses, use dst as the src for the reply.
  649          */
  650         LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash)
  651                 if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr)
  652                         goto match;
  653         /*
  654          * If the incoming packet was addressed to one of our broadcast
  655          * addresses, use the first non-broadcast address which corresponds
  656          * to the incoming interface.
  657          */
  658         if (m->m_pkthdr.rcvif != NULL &&
  659             m->m_pkthdr.rcvif->if_flags & IFF_BROADCAST) {
  660                 TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
  661                         if (ifa->ifa_addr->sa_family != AF_INET)
  662                                 continue;
  663                         ia = ifatoia(ifa);
  664                         if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
  665                             t.s_addr)
  666                                 goto match;
  667                 }
  668         }
  669         /*
  670          * If the packet was transiting through us, use the address of
  671          * the interface the packet came through in.  If that interface
  672          * doesn't have a suitable IP address, the normal selection
  673          * criteria apply.
  674          */
  675         if (icmp_rfi && m->m_pkthdr.rcvif != NULL) {
  676                 TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
  677                         if (ifa->ifa_addr->sa_family != AF_INET)
  678                                 continue;
  679                         ia = ifatoia(ifa);
  680                         goto match;
  681                 }
  682         }
  683         /*
  684          * If the incoming packet was not addressed directly to us, use
  685          * designated interface for icmp replies specified by sysctl
  686          * net.inet.icmp.reply_src (default not set). Otherwise continue
  687          * with normal source selection.
  688          */
  689         if (reply_src[0] != '\0' && (ifn = ifunit(reply_src))) {
  690                 TAILQ_FOREACH(ifa, &ifn->if_addrhead, ifa_link) {
  691                         if (ifa->ifa_addr->sa_family != AF_INET)
  692                                 continue;
  693                         ia = ifatoia(ifa);
  694                         goto match;
  695                 }
  696         }
  697         /*
  698          * If the packet was transiting through us, use the address of
  699          * the interface that is the closest to the packet source.
  700          * When we don't have a route back to the packet source, stop here
  701          * and drop the packet.
  702          */
  703         ia = ip_rtaddr(ip->ip_dst, M_GETFIB(m));
  704         if (ia == NULL) {
  705                 m_freem(m);
  706                 icmpstat.icps_noroute++;
  707                 goto done;
  708         }
  709 match:
  710 #ifdef MAC
  711         mac_reflect_mbuf_icmp(m);
  712 #endif
  713         t = IA_SIN(ia)->sin_addr;
  714         ip->ip_src = t;
  715         ip->ip_ttl = ip_defttl;
  716 
  717         if (optlen > 0) {
  718                 register 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)) == 0 &&
  728                     (opts = m_gethdr(M_DONTWAIT, MT_DATA))) {
  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                             printf("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 "can't happen"
  754                              */
  755                             if (opt == IPOPT_RR || opt == IPOPT_TS ||
  756                                 opt == IPOPT_SECURITY) {
  757                                     bcopy((caddr_t)cp,
  758                                         mtod(opts, caddr_t) + opts->m_len, len);
  759                                     opts->m_len += len;
  760                             }
  761                     }
  762                     /* Terminate & pad, if necessary */
  763                     cnt = opts->m_len % 4;
  764                     if (cnt) {
  765                             for (; cnt < 4; cnt++) {
  766                                     *(mtod(opts, caddr_t) + opts->m_len) =
  767                                         IPOPT_EOL;
  768                                     opts->m_len++;
  769                             }
  770                     }
  771 #ifdef ICMPPRINTFS
  772                     if (icmpprintfs)
  773                             printf("%d\n", opts->m_len);
  774 #endif
  775                 }
  776                 /*
  777                  * Now strip out original options by copying rest of first
  778                  * mbuf's data back, and adjust the IP length.
  779                  */
  780                 ip->ip_len -= optlen;
  781                 ip->ip_v = IPVERSION;
  782                 ip->ip_hl = 5;
  783                 m->m_len -= optlen;
  784                 if (m->m_flags & M_PKTHDR)
  785                         m->m_pkthdr.len -= optlen;
  786                 optlen += sizeof(struct ip);
  787                 bcopy((caddr_t)ip + optlen, (caddr_t)(ip + 1),
  788                          (unsigned)(m->m_len - sizeof(struct ip)));
  789         }
  790         m_tag_delete_nonpersistent(m);
  791         m->m_flags &= ~(M_BCAST|M_MCAST);
  792         icmp_send(m, opts);
  793 done:
  794         if (opts)
  795                 (void)m_free(opts);
  796 }
  797 
  798 /*
  799  * Send an icmp packet back to the ip level,
  800  * after supplying a checksum.
  801  */
  802 static void
  803 icmp_send(struct mbuf *m, struct mbuf *opts)
  804 {
  805         register struct ip *ip = mtod(m, struct ip *);
  806         register int hlen;
  807         register struct icmp *icp;
  808 
  809         hlen = ip->ip_hl << 2;
  810         m->m_data += hlen;
  811         m->m_len -= hlen;
  812         icp = mtod(m, struct icmp *);
  813         icp->icmp_cksum = 0;
  814         icp->icmp_cksum = in_cksum(m, ip->ip_len - hlen);
  815         m->m_data -= hlen;
  816         m->m_len += hlen;
  817         m->m_pkthdr.rcvif = (struct ifnet *)0;
  818 #ifdef ICMPPRINTFS
  819         if (icmpprintfs) {
  820                 char buf[4 * sizeof "123"];
  821                 strcpy(buf, inet_ntoa(ip->ip_dst));
  822                 printf("icmp_send dst %s src %s\n",
  823                        buf, inet_ntoa(ip->ip_src));
  824         }
  825 #endif
  826         (void) ip_output(m, opts, NULL, 0, NULL, NULL);
  827 }
  828 
  829 /*
  830  * Return milliseconds since 00:00 GMT in network format.
  831  */
  832 uint32_t
  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 /*
  844  * Return the next larger or smaller MTU plateau (table from RFC 1191)
  845  * given current value MTU.  If DIR is less than zero, a larger plateau
  846  * is returned; otherwise, a smaller value is returned.
  847  */
  848 int
  849 ip_next_mtu(int mtu, int dir)
  850 {
  851         static int mtutab[] = {
  852                 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1280, 1006, 508,
  853                 296, 68, 0
  854         };
  855         int i, size;
  856 
  857         size = (sizeof mtutab) / (sizeof mtutab[0]);
  858         if (dir >= 0) {
  859                 for (i = 0; i < size; i++)
  860                         if (mtu > mtutab[i])
  861                                 return mtutab[i];
  862         } else {
  863                 for (i = size - 1; i >= 0; i--)
  864                         if (mtu < mtutab[i])
  865                                 return mtutab[i];
  866                 if (mtu == mtutab[0])
  867                         return mtutab[0];
  868         }
  869         return 0;
  870 }
  871 
  872 
  873 /*
  874  * badport_bandlim() - check for ICMP bandwidth limit
  875  *
  876  *      Return 0 if it is ok to send an ICMP error response, -1 if we have
  877  *      hit our bandwidth limit and it is not ok.
  878  *
  879  *      If icmplim is <= 0, the feature is disabled and 0 is returned.
  880  *
  881  *      For now we separate the TCP and UDP subsystems w/ different 'which'
  882  *      values.  We may eventually remove this separation (and simplify the
  883  *      code further).
  884  *
  885  *      Note that the printing of the error message is delayed so we can
  886  *      properly print the icmp error rate that the system was trying to do
  887  *      (i.e. 22000/100 pps, etc...).  This can cause long delays in printing
  888  *      the 'final' error, but it doesn't make sense to solve the printing
  889  *      delay with more complex code.
  890  */
  891 
  892 int
  893 badport_bandlim(int which)
  894 {
  895 #define N(a)    (sizeof (a) / sizeof (a[0]))
  896         static struct rate {
  897                 const char      *type;
  898                 struct timeval  lasttime;
  899                 int             curpps;
  900         } rates[BANDLIM_MAX+1] = {
  901                 { "icmp unreach response" },
  902                 { "icmp ping response" },
  903                 { "icmp tstamp response" },
  904                 { "closed port RST response" },
  905                 { "open port RST response" },
  906                 { "icmp6 unreach response" }
  907         };
  908 
  909         /*
  910          * Return ok status if feature disabled or argument out of range.
  911          */
  912         if (icmplim > 0 && (u_int) which < N(rates)) {
  913                 struct rate *r = &rates[which];
  914                 int opps = r->curpps;
  915 
  916                 if (!ppsratecheck(&r->lasttime, &r->curpps, icmplim))
  917                         return -1;      /* discard packet */
  918                 /*
  919                  * If we've dropped below the threshold after having
  920                  * rate-limited traffic print the message.  This preserves
  921                  * the previous behaviour at the expense of added complexity.
  922                  */
  923                 if (icmplim_output && opps > icmplim)
  924                         log(LOG_NOTICE, "Limiting %s from %d to %d packets/sec\n",
  925                                 r->type, opps, icmplim);
  926         }
  927         return 0;                       /* okay to send packet */
  928 #undef N
  929 }

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