The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: 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  * 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("$FreeBSD$");
   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 
   47 #include <net/if.h>
   48 #include <net/if_types.h>
   49 #include <net/route.h>
   50 
   51 #include <netinet/in.h>
   52 #include <netinet/in_pcb.h>
   53 #include <netinet/in_systm.h>
   54 #include <netinet/in_var.h>
   55 #include <netinet/ip.h>
   56 #include <netinet/ip_icmp.h>
   57 #include <netinet/ip_var.h>
   58 #include <netinet/ip_options.h>
   59 #include <netinet/tcp.h>
   60 #include <netinet/tcp_var.h>
   61 #include <netinet/tcpip.h>
   62 #include <netinet/icmp_var.h>
   63 
   64 #ifdef IPSEC
   65 #include <netipsec/ipsec.h>
   66 #include <netipsec/key.h>
   67 #endif
   68 
   69 #include <machine/in_cksum.h>
   70 
   71 #include <security/mac/mac_framework.h>
   72 
   73 /*
   74  * ICMP routines: error generation, receive packet processing, and
   75  * routines to turnaround packets back to the originator, and
   76  * host table maintenance routines.
   77  */
   78 
   79 struct  icmpstat icmpstat;
   80 SYSCTL_STRUCT(_net_inet_icmp, ICMPCTL_STATS, stats, CTLFLAG_RW,
   81         &icmpstat, icmpstat, "");
   82 
   83 static int      icmpmaskrepl = 0;
   84 SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_RW,
   85         &icmpmaskrepl, 0, "Reply to ICMP Address Mask Request packets.");
   86 
   87 static u_int    icmpmaskfake = 0;
   88 SYSCTL_UINT(_net_inet_icmp, OID_AUTO, maskfake, CTLFLAG_RW,
   89         &icmpmaskfake, 0, "Fake reply to ICMP Address Mask Request packets.");
   90 
   91 static int      drop_redirect = 0;
   92 SYSCTL_INT(_net_inet_icmp, OID_AUTO, drop_redirect, CTLFLAG_RW,
   93         &drop_redirect, 0, "Ignore ICMP redirects");
   94 
   95 static int      log_redirect = 0;
   96 SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_RW,
   97         &log_redirect, 0, "Log ICMP redirects to the console");
   98 
   99 static int      icmplim = 200;
  100 SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RW,
  101         &icmplim, 0, "Maximum number of ICMP responses per second");
  102 
  103 static int      icmplim_output = 1;
  104 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_RW,
  105         &icmplim_output, 0, "Enable rate limiting of ICMP responses");
  106 
  107 static char     reply_src[IFNAMSIZ];
  108 SYSCTL_STRING(_net_inet_icmp, OID_AUTO, reply_src, CTLFLAG_RW,
  109         &reply_src, IFNAMSIZ, "icmp reply source for non-local packets.");
  110 
  111 static int      icmp_rfi = 0;
  112 SYSCTL_INT(_net_inet_icmp, OID_AUTO, reply_from_interface, CTLFLAG_RW,
  113         &icmp_rfi, 0, "ICMP reply from incoming interface for "
  114         "non-local packets");
  115 
  116 static int      icmp_quotelen = 8;
  117 SYSCTL_INT(_net_inet_icmp, OID_AUTO, quotelen, CTLFLAG_RW,
  118         &icmp_quotelen, 0, "Number of bytes from original packet to "
  119         "quote in ICMP reply");
  120 
  121 /*
  122  * ICMP broadcast echo sysctl
  123  */
  124 
  125 static int      icmpbmcastecho = 0;
  126 SYSCTL_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_RW,
  127         &icmpbmcastecho, 0, "");
  128 
  129 
  130 #ifdef ICMPPRINTFS
  131 int     icmpprintfs = 0;
  132 #endif
  133 
  134 static void     icmp_reflect(struct mbuf *);
  135 static void     icmp_send(struct mbuf *, struct mbuf *);
  136 
  137 extern  struct protosw inetsw[];
  138 
  139 /*
  140  * Generate an error packet of type error
  141  * in response to bad packet ip.
  142  */
  143 void
  144 icmp_error(struct mbuf *n, int type, int code, uint32_t dest, int mtu)
  145 {
  146         register struct ip *oip = mtod(n, struct ip *), *nip;
  147         register unsigned oiphlen = oip->ip_hl << 2;
  148         register struct icmp *icp;
  149         register struct mbuf *m;
  150         unsigned icmplen, icmpelen, nlen;
  151 
  152         KASSERT((u_int)type <= ICMP_MAXTYPE, ("%s: illegal ICMP type", __func__));
  153 #ifdef ICMPPRINTFS
  154         if (icmpprintfs)
  155                 printf("icmp_error(%p, %x, %d)\n", oip, type, code);
  156 #endif
  157         if (type != ICMP_REDIRECT)
  158                 icmpstat.icps_error++;
  159         /*
  160          * Don't send error:
  161          *  if the original packet was encrypted.
  162          *  if not the first fragment of message.
  163          *  in response to a multicast or broadcast packet.
  164          *  if the old packet protocol was an ICMP error message.
  165          */
  166         if (n->m_flags & M_DECRYPTED)
  167                 goto freeit;
  168         if (oip->ip_off & ~(IP_MF|IP_DF))
  169                 goto freeit;
  170         if (n->m_flags & (M_BCAST|M_MCAST))
  171                 goto freeit;
  172         if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
  173           n->m_len >= oiphlen + ICMP_MINLEN &&
  174           !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip + oiphlen))->icmp_type)) {
  175                 icmpstat.icps_oldicmp++;
  176                 goto freeit;
  177         }
  178         /* Drop if IP header plus 8 bytes is not contignous in first mbuf. */
  179         if (oiphlen + 8 > n->m_len)
  180                 goto freeit;
  181         /*
  182          * Calculate length to quote from original packet and
  183          * prevent the ICMP mbuf from overflowing.
  184          * Unfortunatly this is non-trivial since ip_forward()
  185          * sends us truncated packets.
  186          */
  187         nlen = m_length(n, NULL);
  188         if (oip->ip_p == IPPROTO_TCP) {
  189                 struct tcphdr *th;
  190                 int tcphlen;
  191 
  192                 if (oiphlen + sizeof(struct tcphdr) > n->m_len &&
  193                     n->m_next == NULL)
  194                         goto stdreply;
  195                 if (n->m_len < oiphlen + sizeof(struct tcphdr) &&
  196                     ((n = m_pullup(n, oiphlen + sizeof(struct tcphdr))) == NULL))
  197                         goto freeit;
  198                 th = (struct tcphdr *)((caddr_t)oip + oiphlen);
  199                 tcphlen = th->th_off << 2;
  200                 if (tcphlen < sizeof(struct tcphdr))
  201                         goto freeit;
  202                 if (oip->ip_len < oiphlen + tcphlen)
  203                         goto freeit;
  204                 if (oiphlen + tcphlen > n->m_len && n->m_next == NULL)
  205                         goto stdreply;
  206                 if (n->m_len < oiphlen + tcphlen && 
  207                     ((n = m_pullup(n, oiphlen + tcphlen)) == NULL))
  208                         goto freeit;
  209                 icmpelen = max(tcphlen, min(icmp_quotelen, oip->ip_len - oiphlen));
  210         } else
  211 stdreply:       icmpelen = max(8, min(icmp_quotelen, oip->ip_len - oiphlen));
  212 
  213         icmplen = min(oiphlen + icmpelen, nlen);
  214         if (icmplen < sizeof(struct ip))
  215                 goto freeit;
  216 
  217         if (MHLEN > sizeof(struct ip) + ICMP_MINLEN + icmplen)
  218                 m = m_gethdr(M_DONTWAIT, MT_DATA);
  219         else
  220                 m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
  221         if (m == NULL)
  222                 goto freeit;
  223 #ifdef MAC
  224         mac_create_mbuf_netlayer(n, m);
  225 #endif
  226         icmplen = min(icmplen, M_TRAILINGSPACE(m) - sizeof(struct ip) - ICMP_MINLEN);
  227         m_align(m, ICMP_MINLEN + icmplen);
  228         m->m_len = ICMP_MINLEN + icmplen;
  229 
  230         /* XXX MRT  make the outgoing packet use the same FIB
  231          * that was associated with the incoming packet
  232          */
  233         M_SETFIB(m, M_GETFIB(n));
  234         icp = mtod(m, struct icmp *);
  235         icmpstat.icps_outhist[type]++;
  236         icp->icmp_type = type;
  237         if (type == ICMP_REDIRECT)
  238                 icp->icmp_gwaddr.s_addr = dest;
  239         else {
  240                 icp->icmp_void = 0;
  241                 /*
  242                  * The following assignments assume an overlay with the
  243                  * just zeroed icmp_void field.
  244                  */
  245                 if (type == ICMP_PARAMPROB) {
  246                         icp->icmp_pptr = code;
  247                         code = 0;
  248                 } else if (type == ICMP_UNREACH &&
  249                         code == ICMP_UNREACH_NEEDFRAG && mtu) {
  250                         icp->icmp_nextmtu = htons(mtu);
  251                 }
  252         }
  253         icp->icmp_code = code;
  254 
  255         /*
  256          * Copy the quotation into ICMP message and
  257          * convert quoted IP header back to network representation.
  258          */
  259         m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip);
  260         nip = &icp->icmp_ip;
  261         nip->ip_len = htons(nip->ip_len);
  262         nip->ip_off = htons(nip->ip_off);
  263 
  264         /*
  265          * Set up ICMP message mbuf and copy old IP header (without options
  266          * in front of ICMP message.
  267          * If the original mbuf was meant to bypass the firewall, the error
  268          * reply should bypass as well.
  269          */
  270         m->m_flags |= n->m_flags & M_SKIP_FIREWALL;
  271         m->m_data -= sizeof(struct ip);
  272         m->m_len += sizeof(struct ip);
  273         m->m_pkthdr.len = m->m_len;
  274         m->m_pkthdr.rcvif = n->m_pkthdr.rcvif;
  275         nip = mtod(m, struct ip *);
  276         bcopy((caddr_t)oip, (caddr_t)nip, sizeof(struct ip));
  277         nip->ip_len = m->m_len;
  278         nip->ip_v = IPVERSION;
  279         nip->ip_hl = 5;
  280         nip->ip_p = IPPROTO_ICMP;
  281         nip->ip_tos = 0;
  282         icmp_reflect(m);
  283 
  284 freeit:
  285         m_freem(n);
  286 }
  287 
  288 /*
  289  * Process a received ICMP message.
  290  */
  291 void
  292 icmp_input(struct mbuf *m, int off)
  293 {
  294         struct icmp *icp;
  295         struct in_ifaddr *ia;
  296         struct ip *ip = mtod(m, struct ip *);
  297         struct sockaddr_in icmpsrc, icmpdst, icmpgw;
  298         int hlen = off;
  299         int icmplen = ip->ip_len;
  300         int i, code;
  301         void (*ctlfunc)(int, struct sockaddr *, void *);
  302         int fibnum;
  303 
  304         /*
  305          * Locate icmp structure in mbuf, and check
  306          * that not corrupted and of at least minimum length.
  307          */
  308 #ifdef ICMPPRINTFS
  309         if (icmpprintfs) {
  310                 char buf[4 * sizeof "123"];
  311                 strcpy(buf, inet_ntoa(ip->ip_src));
  312                 printf("icmp_input from %s to %s, len %d\n",
  313                        buf, inet_ntoa(ip->ip_dst), icmplen);
  314         }
  315 #endif
  316         if (icmplen < ICMP_MINLEN) {
  317                 icmpstat.icps_tooshort++;
  318                 goto freeit;
  319         }
  320         i = hlen + min(icmplen, ICMP_ADVLENMIN);
  321         if (m->m_len < i && (m = m_pullup(m, i)) == 0)  {
  322                 icmpstat.icps_tooshort++;
  323                 return;
  324         }
  325         ip = mtod(m, struct ip *);
  326         m->m_len -= hlen;
  327         m->m_data += hlen;
  328         icp = mtod(m, struct icmp *);
  329         if (in_cksum(m, icmplen)) {
  330                 icmpstat.icps_checksum++;
  331                 goto freeit;
  332         }
  333         m->m_len += hlen;
  334         m->m_data -= hlen;
  335 
  336         if (m->m_pkthdr.rcvif && m->m_pkthdr.rcvif->if_type == IFT_FAITH) {
  337                 /*
  338                  * Deliver very specific ICMP type only.
  339                  */
  340                 switch (icp->icmp_type) {
  341                 case ICMP_UNREACH:
  342                 case ICMP_TIMXCEED:
  343                         break;
  344                 default:
  345                         goto freeit;
  346                 }
  347         }
  348 
  349 #ifdef ICMPPRINTFS
  350         if (icmpprintfs)
  351                 printf("icmp_input, type %d code %d\n", icp->icmp_type,
  352                     icp->icmp_code);
  353 #endif
  354 
  355         /*
  356          * Message type specific processing.
  357          */
  358         if (icp->icmp_type > ICMP_MAXTYPE)
  359                 goto raw;
  360 
  361         /* Initialize */
  362         bzero(&icmpsrc, sizeof(icmpsrc));
  363         icmpsrc.sin_len = sizeof(struct sockaddr_in);
  364         icmpsrc.sin_family = AF_INET;
  365         bzero(&icmpdst, sizeof(icmpdst));
  366         icmpdst.sin_len = sizeof(struct sockaddr_in);
  367         icmpdst.sin_family = AF_INET;
  368         bzero(&icmpgw, sizeof(icmpgw));
  369         icmpgw.sin_len = sizeof(struct sockaddr_in);
  370         icmpgw.sin_family = AF_INET;
  371 
  372         icmpstat.icps_inhist[icp->icmp_type]++;
  373         code = icp->icmp_code;
  374         switch (icp->icmp_type) {
  375 
  376         case ICMP_UNREACH:
  377                 switch (code) {
  378                         case ICMP_UNREACH_NET:
  379                         case ICMP_UNREACH_HOST:
  380                         case ICMP_UNREACH_SRCFAIL:
  381                         case ICMP_UNREACH_NET_UNKNOWN:
  382                         case ICMP_UNREACH_HOST_UNKNOWN:
  383                         case ICMP_UNREACH_ISOLATED:
  384                         case ICMP_UNREACH_TOSNET:
  385                         case ICMP_UNREACH_TOSHOST:
  386                         case ICMP_UNREACH_HOST_PRECEDENCE:
  387                         case ICMP_UNREACH_PRECEDENCE_CUTOFF:
  388                                 code = PRC_UNREACH_NET;
  389                                 break;
  390 
  391                         case ICMP_UNREACH_NEEDFRAG:
  392                                 code = PRC_MSGSIZE;
  393                                 break;
  394 
  395                         /*
  396                          * RFC 1122, Sections 3.2.2.1 and 4.2.3.9.
  397                          * Treat subcodes 2,3 as immediate RST
  398                          */
  399                         case ICMP_UNREACH_PROTOCOL:
  400                         case ICMP_UNREACH_PORT:
  401                                 code = PRC_UNREACH_PORT;
  402                                 break;
  403 
  404                         case ICMP_UNREACH_NET_PROHIB:
  405                         case ICMP_UNREACH_HOST_PROHIB:
  406                         case ICMP_UNREACH_FILTER_PROHIB:
  407                                 code = PRC_UNREACH_ADMIN_PROHIB;
  408                                 break;
  409 
  410                         default:
  411                                 goto badcode;
  412                 }
  413                 goto deliver;
  414 
  415         case ICMP_TIMXCEED:
  416                 if (code > 1)
  417                         goto badcode;
  418                 code += PRC_TIMXCEED_INTRANS;
  419                 goto deliver;
  420 
  421         case ICMP_PARAMPROB:
  422                 if (code > 1)
  423                         goto badcode;
  424                 code = PRC_PARAMPROB;
  425                 goto deliver;
  426 
  427         case ICMP_SOURCEQUENCH:
  428                 if (code)
  429                         goto badcode;
  430                 code = PRC_QUENCH;
  431         deliver:
  432                 /*
  433                  * Problem with datagram; advise higher level routines.
  434                  */
  435                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  436                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
  437                         icmpstat.icps_badlen++;
  438                         goto freeit;
  439                 }
  440                 icp->icmp_ip.ip_len = ntohs(icp->icmp_ip.ip_len);
  441                 /* Discard ICMP's in response to multicast packets */
  442                 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
  443                         goto badcode;
  444 #ifdef ICMPPRINTFS
  445                 if (icmpprintfs)
  446                         printf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
  447 #endif
  448                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  449                 /*
  450                  * XXX if the packet contains [IPv4 AH TCP], we can't make a
  451                  * notification to TCP layer.
  452                  */
  453                 ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput;
  454                 if (ctlfunc)
  455                         (*ctlfunc)(code, (struct sockaddr *)&icmpsrc,
  456                                    (void *)&icp->icmp_ip);
  457                 break;
  458 
  459         badcode:
  460                 icmpstat.icps_badcode++;
  461                 break;
  462 
  463         case ICMP_ECHO:
  464                 if (!icmpbmcastecho
  465                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
  466                         icmpstat.icps_bmcastecho++;
  467                         break;
  468                 }
  469                 icp->icmp_type = ICMP_ECHOREPLY;
  470                 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
  471                         goto freeit;
  472                 else
  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                 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
  489                         goto freeit;
  490                 else
  491                         goto reflect;
  492 
  493         case ICMP_MASKREQ:
  494                 if (icmpmaskrepl == 0)
  495                         break;
  496                 /*
  497                  * We are not able to respond with all ones broadcast
  498                  * unless we receive it over a point-to-point interface.
  499                  */
  500                 if (icmplen < ICMP_MASKLEN)
  501                         break;
  502                 switch (ip->ip_dst.s_addr) {
  503 
  504                 case INADDR_BROADCAST:
  505                 case INADDR_ANY:
  506                         icmpdst.sin_addr = ip->ip_src;
  507                         break;
  508 
  509                 default:
  510                         icmpdst.sin_addr = ip->ip_dst;
  511                 }
  512                 ia = (struct in_ifaddr *)ifaof_ifpforaddr(
  513                             (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
  514                 if (ia == 0)
  515                         break;
  516                 if (ia->ia_ifp == 0)
  517                         break;
  518                 icp->icmp_type = ICMP_MASKREPLY;
  519                 if (icmpmaskfake == 0)
  520                         icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr;
  521                 else
  522                         icp->icmp_mask = icmpmaskfake;
  523                 if (ip->ip_src.s_addr == 0) {
  524                         if (ia->ia_ifp->if_flags & IFF_BROADCAST)
  525                             ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr;
  526                         else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT)
  527                             ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr;
  528                 }
  529 reflect:
  530                 ip->ip_len += hlen;     /* since ip_input deducts this */
  531                 icmpstat.icps_reflect++;
  532                 icmpstat.icps_outhist[icp->icmp_type]++;
  533                 icmp_reflect(m);
  534                 return;
  535 
  536         case ICMP_REDIRECT:
  537                 if (log_redirect) {
  538                         u_long src, dst, gw;
  539 
  540                         src = ntohl(ip->ip_src.s_addr);
  541                         dst = ntohl(icp->icmp_ip.ip_dst.s_addr);
  542                         gw = ntohl(icp->icmp_gwaddr.s_addr);
  543                         printf("icmp redirect from %d.%d.%d.%d: "
  544                                "%d.%d.%d.%d => %d.%d.%d.%d\n",
  545                                (int)(src >> 24), (int)((src >> 16) & 0xff),
  546                                (int)((src >> 8) & 0xff), (int)(src & 0xff),
  547                                (int)(dst >> 24), (int)((dst >> 16) & 0xff),
  548                                (int)((dst >> 8) & 0xff), (int)(dst & 0xff),
  549                                (int)(gw >> 24), (int)((gw >> 16) & 0xff),
  550                                (int)((gw >> 8) & 0xff), (int)(gw & 0xff));
  551                 }
  552                 /*
  553                  * RFC1812 says we must ignore ICMP redirects if we
  554                  * are acting as router.
  555                  */
  556                 if (drop_redirect || ipforwarding)
  557                         break;
  558                 if (code > 3)
  559                         goto badcode;
  560                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  561                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
  562                         icmpstat.icps_badlen++;
  563                         break;
  564                 }
  565                 /*
  566                  * Short circuit routing redirects to force
  567                  * immediate change in the kernel's routing
  568                  * tables.  The message is also handed to anyone
  569                  * listening on a raw socket (e.g. the routing
  570                  * daemon for use in updating its tables).
  571                  */
  572                 icmpgw.sin_addr = ip->ip_src;
  573                 icmpdst.sin_addr = icp->icmp_gwaddr;
  574 #ifdef  ICMPPRINTFS
  575                 if (icmpprintfs) {
  576                         char buf[4 * sizeof "123"];
  577                         strcpy(buf, inet_ntoa(icp->icmp_ip.ip_dst));
  578 
  579                         printf("redirect dst %s to %s\n",
  580                                buf, inet_ntoa(icp->icmp_gwaddr));
  581                 }
  582 #endif
  583                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  584                 for ( fibnum = 0; fibnum < rt_numfibs; fibnum++) {
  585                         in_rtredirect((struct sockaddr *)&icmpsrc,
  586                           (struct sockaddr *)&icmpdst,
  587                           (struct sockaddr *)0, RTF_GATEWAY | RTF_HOST,
  588                           (struct sockaddr *)&icmpgw, fibnum);
  589                 }
  590                 pfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
  591 #ifdef IPSEC
  592                 key_sa_routechange((struct sockaddr *)&icmpsrc);
  593 #endif
  594                 break;
  595 
  596         /*
  597          * No kernel processing for the following;
  598          * just fall through to send to raw listener.
  599          */
  600         case ICMP_ECHOREPLY:
  601         case ICMP_ROUTERADVERT:
  602         case ICMP_ROUTERSOLICIT:
  603         case ICMP_TSTAMPREPLY:
  604         case ICMP_IREQREPLY:
  605         case ICMP_MASKREPLY:
  606         default:
  607                 break;
  608         }
  609 
  610 raw:
  611         rip_input(m, off);
  612         return;
  613 
  614 freeit:
  615         m_freem(m);
  616 }
  617 
  618 /*
  619  * Reflect the ip packet back to the source
  620  */
  621 static void
  622 icmp_reflect(struct mbuf *m)
  623 {
  624         struct ip *ip = mtod(m, struct ip *);
  625         struct ifaddr *ifa;
  626         struct ifnet *ifn;
  627         struct in_ifaddr *ia;
  628         struct in_addr t;
  629         struct mbuf *opts = 0;
  630         int optlen = (ip->ip_hl << 2) - sizeof(struct ip);
  631 
  632         if (IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
  633             IN_EXPERIMENTAL(ntohl(ip->ip_src.s_addr)) ||
  634             IN_ZERONET(ntohl(ip->ip_src.s_addr)) ) {
  635                 m_freem(m);     /* Bad return address */
  636                 icmpstat.icps_badaddr++;
  637                 goto done;      /* Ip_output() will check for broadcast */
  638         }
  639 
  640         t = ip->ip_dst;
  641         ip->ip_dst = ip->ip_src;
  642 
  643         /*
  644          * Source selection for ICMP replies:
  645          *
  646          * If the incoming packet was addressed directly to one of our
  647          * own addresses, use dst as the src for the reply.
  648          */
  649         LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash)
  650                 if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr)
  651                         goto match;
  652         /*
  653          * If the incoming packet was addressed to one of our broadcast
  654          * addresses, use the first non-broadcast address which corresponds
  655          * to the incoming interface.
  656          */
  657         if (m->m_pkthdr.rcvif != NULL &&
  658             m->m_pkthdr.rcvif->if_flags & IFF_BROADCAST) {
  659                 TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
  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 && m->m_pkthdr.rcvif != NULL) {
  675                 TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
  676                         if (ifa->ifa_addr->sa_family != AF_INET)
  677                                 continue;
  678                         ia = ifatoia(ifa);
  679                         goto match;
  680                 }
  681         }
  682         /*
  683          * If the incoming packet was not addressed directly to us, use
  684          * designated interface for icmp replies specified by sysctl
  685          * net.inet.icmp.reply_src (default not set). Otherwise continue
  686          * with normal source selection.
  687          */
  688         if (reply_src[0] != '\0' && (ifn = ifunit(reply_src))) {
  689                 TAILQ_FOREACH(ifa, &ifn->if_addrhead, ifa_link) {
  690                         if (ifa->ifa_addr->sa_family != AF_INET)
  691                                 continue;
  692                         ia = ifatoia(ifa);
  693                         goto match;
  694                 }
  695         }
  696         /*
  697          * If the packet was transiting through us, use the address of
  698          * the interface that is the closest to the packet source.
  699          * When we don't have a route back to the packet source, stop here
  700          * and drop the packet.
  701          */
  702         ia = ip_rtaddr(ip->ip_dst, M_GETFIB(m));
  703         if (ia == NULL) {
  704                 m_freem(m);
  705                 icmpstat.icps_noroute++;
  706                 goto done;
  707         }
  708 match:
  709 #ifdef MAC
  710         mac_reflect_mbuf_icmp(m);
  711 #endif
  712         t = IA_SIN(ia)->sin_addr;
  713         ip->ip_src = t;
  714         ip->ip_ttl = ip_defttl;
  715 
  716         if (optlen > 0) {
  717                 register u_char *cp;
  718                 int opt, cnt;
  719                 u_int len;
  720 
  721                 /*
  722                  * Retrieve any source routing from the incoming packet;
  723                  * add on any record-route or timestamp options.
  724                  */
  725                 cp = (u_char *) (ip + 1);
  726                 if ((opts = ip_srcroute(m)) == 0 &&
  727                     (opts = m_gethdr(M_DONTWAIT, MT_DATA))) {
  728                         opts->m_len = sizeof(struct in_addr);
  729                         mtod(opts, struct in_addr *)->s_addr = 0;
  730                 }
  731                 if (opts) {
  732 #ifdef ICMPPRINTFS
  733                     if (icmpprintfs)
  734                             printf("icmp_reflect optlen %d rt %d => ",
  735                                 optlen, opts->m_len);
  736 #endif
  737                     for (cnt = optlen; cnt > 0; cnt -= len, cp += len) {
  738                             opt = cp[IPOPT_OPTVAL];
  739                             if (opt == IPOPT_EOL)
  740                                     break;
  741                             if (opt == IPOPT_NOP)
  742                                     len = 1;
  743                             else {
  744                                     if (cnt < IPOPT_OLEN + sizeof(*cp))
  745                                             break;
  746                                     len = cp[IPOPT_OLEN];
  747                                     if (len < IPOPT_OLEN + sizeof(*cp) ||
  748                                         len > cnt)
  749                                             break;
  750                             }
  751                             /*
  752                              * Should check for overflow, but it "can't happen"
  753                              */
  754                             if (opt == IPOPT_RR || opt == IPOPT_TS ||
  755                                 opt == IPOPT_SECURITY) {
  756                                     bcopy((caddr_t)cp,
  757                                         mtod(opts, caddr_t) + opts->m_len, len);
  758                                     opts->m_len += len;
  759                             }
  760                     }
  761                     /* Terminate & pad, if necessary */
  762                     cnt = opts->m_len % 4;
  763                     if (cnt) {
  764                             for (; cnt < 4; cnt++) {
  765                                     *(mtod(opts, caddr_t) + opts->m_len) =
  766                                         IPOPT_EOL;
  767                                     opts->m_len++;
  768                             }
  769                     }
  770 #ifdef ICMPPRINTFS
  771                     if (icmpprintfs)
  772                             printf("%d\n", opts->m_len);
  773 #endif
  774                 }
  775                 /*
  776                  * Now strip out original options by copying rest of first
  777                  * mbuf's data back, and adjust the IP length.
  778                  */
  779                 ip->ip_len -= optlen;
  780                 ip->ip_v = IPVERSION;
  781                 ip->ip_hl = 5;
  782                 m->m_len -= optlen;
  783                 if (m->m_flags & M_PKTHDR)
  784                         m->m_pkthdr.len -= optlen;
  785                 optlen += sizeof(struct ip);
  786                 bcopy((caddr_t)ip + optlen, (caddr_t)(ip + 1),
  787                          (unsigned)(m->m_len - sizeof(struct ip)));
  788         }
  789         m_tag_delete_nonpersistent(m);
  790         m->m_flags &= ~(M_BCAST|M_MCAST);
  791         icmp_send(m, opts);
  792 done:
  793         if (opts)
  794                 (void)m_free(opts);
  795 }
  796 
  797 /*
  798  * Send an icmp packet back to the ip level,
  799  * after supplying a checksum.
  800  */
  801 static void
  802 icmp_send(struct mbuf *m, struct mbuf *opts)
  803 {
  804         register struct ip *ip = mtod(m, struct ip *);
  805         register int hlen;
  806         register struct icmp *icp;
  807 
  808         hlen = ip->ip_hl << 2;
  809         m->m_data += hlen;
  810         m->m_len -= hlen;
  811         icp = mtod(m, struct icmp *);
  812         icp->icmp_cksum = 0;
  813         icp->icmp_cksum = in_cksum(m, ip->ip_len - hlen);
  814         m->m_data -= hlen;
  815         m->m_len += hlen;
  816         m->m_pkthdr.rcvif = (struct ifnet *)0;
  817 #ifdef ICMPPRINTFS
  818         if (icmpprintfs) {
  819                 char buf[4 * sizeof "123"];
  820                 strcpy(buf, inet_ntoa(ip->ip_dst));
  821                 printf("icmp_send dst %s src %s\n",
  822                        buf, inet_ntoa(ip->ip_src));
  823         }
  824 #endif
  825         (void) ip_output(m, opts, NULL, 0, NULL, NULL);
  826 }
  827 
  828 /*
  829  * Return milliseconds since 00:00 GMT in network format.
  830  */
  831 uint32_t
  832 iptime(void)
  833 {
  834         struct timeval atv;
  835         u_long t;
  836 
  837         getmicrotime(&atv);
  838         t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000;
  839         return (htonl(t));
  840 }
  841 
  842 /*
  843  * Return the next larger or smaller MTU plateau (table from RFC 1191)
  844  * given current value MTU.  If DIR is less than zero, a larger plateau
  845  * is returned; otherwise, a smaller value is returned.
  846  */
  847 int
  848 ip_next_mtu(int mtu, int dir)
  849 {
  850         static int mtutab[] = {
  851                 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1280, 1006, 508,
  852                 296, 68, 0
  853         };
  854         int i, size;
  855 
  856         size = (sizeof mtutab) / (sizeof mtutab[0]);
  857         if (dir >= 0) {
  858                 for (i = 0; i < size; i++)
  859                         if (mtu > mtutab[i])
  860                                 return mtutab[i];
  861         } else {
  862                 for (i = size - 1; i >= 0; i--)
  863                         if (mtu < mtutab[i])
  864                                 return mtutab[i];
  865                 if (mtu == mtutab[0])
  866                         return mtutab[0];
  867         }
  868         return 0;
  869 }
  870 
  871 
  872 /*
  873  * badport_bandlim() - check for ICMP bandwidth limit
  874  *
  875  *      Return 0 if it is ok to send an ICMP error response, -1 if we have
  876  *      hit our bandwidth limit and it is not ok.
  877  *
  878  *      If icmplim is <= 0, the feature is disabled and 0 is returned.
  879  *
  880  *      For now we separate the TCP and UDP subsystems w/ different 'which'
  881  *      values.  We may eventually remove this separation (and simplify the
  882  *      code further).
  883  *
  884  *      Note that the printing of the error message is delayed so we can
  885  *      properly print the icmp error rate that the system was trying to do
  886  *      (i.e. 22000/100 pps, etc...).  This can cause long delays in printing
  887  *      the 'final' error, but it doesn't make sense to solve the printing
  888  *      delay with more complex code.
  889  */
  890 
  891 int
  892 badport_bandlim(int which)
  893 {
  894 #define N(a)    (sizeof (a) / sizeof (a[0]))
  895         static struct rate {
  896                 const char      *type;
  897                 struct timeval  lasttime;
  898                 int             curpps;
  899         } rates[BANDLIM_MAX+1] = {
  900                 { "icmp unreach response" },
  901                 { "icmp ping response" },
  902                 { "icmp tstamp response" },
  903                 { "closed port RST response" },
  904                 { "open port RST response" },
  905                 { "icmp6 unreach response" }
  906         };
  907 
  908         /*
  909          * Return ok status if feature disabled or argument out of range.
  910          */
  911         if (icmplim > 0 && (u_int) which < N(rates)) {
  912                 struct rate *r = &rates[which];
  913                 int opps = r->curpps;
  914 
  915                 if (!ppsratecheck(&r->lasttime, &r->curpps, icmplim))
  916                         return -1;      /* discard packet */
  917                 /*
  918                  * If we've dropped below the threshold after having
  919                  * rate-limited traffic print the message.  This preserves
  920                  * the previous behaviour at the expense of added complexity.
  921                  */
  922                 if (icmplim_output && opps > icmplim)
  923                         printf("Limiting %s from %d to %d packets/sec\n",
  924                                 r->type, opps, icmplim);
  925         }
  926         return 0;                       /* okay to send packet */
  927 #undef N
  928 }

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