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_inet.h"
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/mbuf.h>
   40 #include <sys/protosw.h>
   41 #include <sys/socket.h>
   42 #include <sys/time.h>
   43 #include <sys/kernel.h>
   44 #include <sys/sysctl.h>
   45 #include <sys/syslog.h>
   46 
   47 #include <net/if.h>
   48 #include <net/if_types.h>
   49 #include <net/route.h>
   50 #include <net/vnet.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 INET
   66 
   67 #include <machine/in_cksum.h>
   68 
   69 #include <security/mac/mac_framework.h>
   70 #endif /* INET */
   71 
   72 /*
   73  * ICMP routines: error generation, receive packet processing, and
   74  * routines to turnaround packets back to the originator, and
   75  * host table maintenance routines.
   76  */
   77 static VNET_DEFINE(int, icmplim) = 200;
   78 #define V_icmplim                       VNET(icmplim)
   79 SYSCTL_VNET_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RW,
   80         &VNET_NAME(icmplim), 0,
   81         "Maximum number of ICMP responses per second");
   82 
   83 static VNET_DEFINE(int, icmplim_output) = 1;
   84 #define V_icmplim_output                VNET(icmplim_output)
   85 SYSCTL_VNET_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_RW,
   86         &VNET_NAME(icmplim_output), 0,
   87         "Enable logging of ICMP response rate limiting");
   88 
   89 #ifdef INET
   90 VNET_PCPUSTAT_DEFINE(struct icmpstat, icmpstat);
   91 VNET_PCPUSTAT_SYSINIT(icmpstat);
   92 SYSCTL_VNET_PCPUSTAT(_net_inet_icmp, ICMPCTL_STATS, stats, struct icmpstat,
   93     icmpstat, "ICMP statistics (struct icmpstat, netinet/icmp_var.h)");
   94 
   95 #ifdef VIMAGE
   96 VNET_PCPUSTAT_SYSUNINIT(icmpstat);
   97 #endif /* VIMAGE */
   98 
   99 static VNET_DEFINE(int, icmpmaskrepl) = 0;
  100 #define V_icmpmaskrepl                  VNET(icmpmaskrepl)
  101 SYSCTL_VNET_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_RW,
  102         &VNET_NAME(icmpmaskrepl), 0,
  103         "Reply to ICMP Address Mask Request packets.");
  104 
  105 static VNET_DEFINE(u_int, icmpmaskfake) = 0;
  106 #define V_icmpmaskfake                  VNET(icmpmaskfake)
  107 SYSCTL_VNET_UINT(_net_inet_icmp, OID_AUTO, maskfake, CTLFLAG_RW,
  108         &VNET_NAME(icmpmaskfake), 0,
  109         "Fake reply to ICMP Address Mask Request packets.");
  110 
  111 VNET_DEFINE(int, drop_redirect) = 0;
  112 
  113 static VNET_DEFINE(int, log_redirect) = 0;
  114 #define V_log_redirect                  VNET(log_redirect)
  115 SYSCTL_VNET_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_RW,
  116         &VNET_NAME(log_redirect), 0,
  117         "Log ICMP redirects to the console");
  118 
  119 static VNET_DEFINE(char, reply_src[IFNAMSIZ]);
  120 #define V_reply_src                     VNET(reply_src)
  121 SYSCTL_VNET_STRING(_net_inet_icmp, OID_AUTO, reply_src, CTLFLAG_RW,
  122         &VNET_NAME(reply_src), IFNAMSIZ,
  123         "icmp reply source for non-local packets.");
  124 
  125 static VNET_DEFINE(int, icmp_rfi) = 0;
  126 #define V_icmp_rfi                      VNET(icmp_rfi)
  127 SYSCTL_VNET_INT(_net_inet_icmp, OID_AUTO, reply_from_interface, CTLFLAG_RW,
  128         &VNET_NAME(icmp_rfi), 0,
  129         "ICMP reply from incoming interface for non-local packets");
  130 
  131 static VNET_DEFINE(int, icmp_quotelen) = 8;
  132 #define V_icmp_quotelen                 VNET(icmp_quotelen)
  133 SYSCTL_VNET_INT(_net_inet_icmp, OID_AUTO, quotelen, CTLFLAG_RW,
  134         &VNET_NAME(icmp_quotelen), 0,
  135         "Number of bytes from original packet to quote in ICMP reply");
  136 
  137 /*
  138  * ICMP broadcast echo sysctl
  139  */
  140 static VNET_DEFINE(int, icmpbmcastecho) = 0;
  141 #define V_icmpbmcastecho                VNET(icmpbmcastecho)
  142 SYSCTL_VNET_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_RW,
  143         &VNET_NAME(icmpbmcastecho), 0,
  144         "");
  145 
  146 static VNET_DEFINE(int, icmptstamprepl) = 1;
  147 #define V_icmptstamprepl                VNET(icmptstamprepl)
  148 SYSCTL_INT(_net_inet_icmp, OID_AUTO, tstamprepl, CTLFLAG_RW,
  149         &VNET_NAME(icmptstamprepl), 0, "Respond to ICMP Timestamp packets");
  150 
  151 static VNET_DEFINE(int, error_keeptags) = 0;
  152 #define V_error_keeptags                VNET(error_keeptags)
  153 SYSCTL_INT(_net_inet_icmp, OID_AUTO, error_keeptags, CTLFLAG_VNET | CTLFLAG_RW,
  154         &VNET_NAME(error_keeptags), 0,
  155         "ICMP error response keeps copy of mbuf_tags of original packet");
  156 
  157 #ifdef ICMPPRINTFS
  158 int     icmpprintfs = 0;
  159 #endif
  160 
  161 static void     icmp_reflect(struct mbuf *);
  162 static void     icmp_send(struct mbuf *, struct mbuf *);
  163 
  164 extern  struct protosw inetsw[];
  165 
  166 static int
  167 sysctl_net_icmp_drop_redir(SYSCTL_HANDLER_ARGS)
  168 {
  169         int error, new;
  170         int i;
  171         struct radix_node_head *rnh;
  172 
  173         new = V_drop_redirect;
  174         error = sysctl_handle_int(oidp, &new, 0, req);
  175         if (error == 0 && req->newptr) {
  176                 new = (new != 0) ? 1 : 0;
  177 
  178                 if (new == V_drop_redirect)
  179                         return (0);
  180 
  181                 for (i = 0; i < rt_numfibs; i++) {
  182                         if ((rnh = rt_tables_get_rnh(i, AF_INET)) == NULL)
  183                                 continue;
  184                         RADIX_NODE_HEAD_LOCK(rnh);
  185                         in_setmatchfunc(rnh, new);
  186                         RADIX_NODE_HEAD_UNLOCK(rnh);
  187                 }
  188                 
  189                 V_drop_redirect = new;
  190         }
  191 
  192         return (error);
  193 }
  194 
  195 SYSCTL_VNET_PROC(_net_inet_icmp, OID_AUTO, drop_redirect,
  196     CTLTYPE_INT|CTLFLAG_RW, 0, 0,
  197     sysctl_net_icmp_drop_redir, "I", "Ignore ICMP redirects");
  198 
  199 /*
  200  * Kernel module interface for updating icmpstat.  The argument is an index
  201  * into icmpstat treated as an array of u_long.  While this encodes the
  202  * general layout of icmpstat into the caller, it doesn't encode its
  203  * location, so that future changes to add, for example, per-CPU stats
  204  * support won't cause binary compatibility problems for kernel modules.
  205  */
  206 void
  207 kmod_icmpstat_inc(int statnum)
  208 {
  209 
  210         counter_u64_add(VNET(icmpstat)[statnum], 1);
  211 }
  212 
  213 /*
  214  * Generate an error packet of type error
  215  * in response to bad packet ip.
  216  */
  217 void
  218 icmp_error(struct mbuf *n, int type, int code, uint32_t dest, int mtu)
  219 {
  220         register struct ip *oip = mtod(n, struct ip *), *nip;
  221         register unsigned oiphlen = oip->ip_hl << 2;
  222         register struct icmp *icp;
  223         register struct mbuf *m;
  224         unsigned icmplen, icmpelen, nlen;
  225 
  226         KASSERT((u_int)type <= ICMP_MAXTYPE, ("%s: illegal ICMP type", __func__));
  227 #ifdef ICMPPRINTFS
  228         if (icmpprintfs)
  229                 printf("icmp_error(%p, %x, %d)\n", oip, type, code);
  230 #endif
  231         if (type != ICMP_REDIRECT)
  232                 ICMPSTAT_INC(icps_error);
  233         /*
  234          * Don't send error:
  235          *  if the original packet was encrypted.
  236          *  if not the first fragment of message.
  237          *  in response to a multicast or broadcast packet.
  238          *  if the old packet protocol was an ICMP error message.
  239          */
  240         if (n->m_flags & M_DECRYPTED)
  241                 goto freeit;
  242         if (oip->ip_off & htons(~(IP_MF|IP_DF)))
  243                 goto freeit;
  244         if (n->m_flags & (M_BCAST|M_MCAST))
  245                 goto freeit;
  246         if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
  247           n->m_len >= oiphlen + ICMP_MINLEN &&
  248           !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip + oiphlen))->icmp_type)) {
  249                 ICMPSTAT_INC(icps_oldicmp);
  250                 goto freeit;
  251         }
  252         /* Drop if IP header plus 8 bytes is not contignous in first mbuf. */
  253         if (oiphlen + 8 > n->m_len)
  254                 goto freeit;
  255         /*
  256          * Calculate length to quote from original packet and
  257          * prevent the ICMP mbuf from overflowing.
  258          * Unfortunatly this is non-trivial since ip_forward()
  259          * sends us truncated packets.
  260          */
  261         nlen = m_length(n, NULL);
  262         if (oip->ip_p == IPPROTO_TCP) {
  263                 struct tcphdr *th;
  264                 int tcphlen;
  265 
  266                 if (oiphlen + sizeof(struct tcphdr) > n->m_len &&
  267                     n->m_next == NULL)
  268                         goto stdreply;
  269                 if (n->m_len < oiphlen + sizeof(struct tcphdr) &&
  270                     ((n = m_pullup(n, oiphlen + sizeof(struct tcphdr))) == NULL))
  271                         goto freeit;
  272                 th = (struct tcphdr *)((caddr_t)oip + oiphlen);
  273                 tcphlen = th->th_off << 2;
  274                 if (tcphlen < sizeof(struct tcphdr))
  275                         goto freeit;
  276                 if (ntohs(oip->ip_len) < oiphlen + tcphlen)
  277                         goto freeit;
  278                 if (oiphlen + tcphlen > n->m_len && n->m_next == NULL)
  279                         goto stdreply;
  280                 if (n->m_len < oiphlen + tcphlen && 
  281                     ((n = m_pullup(n, oiphlen + tcphlen)) == NULL))
  282                         goto freeit;
  283                 icmpelen = max(tcphlen, min(V_icmp_quotelen,
  284                     ntohs(oip->ip_len) - oiphlen));
  285         } else
  286 stdreply:       icmpelen = max(8, min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen));
  287 
  288         icmplen = min(oiphlen + icmpelen, nlen);
  289         if (icmplen < sizeof(struct ip))
  290                 goto freeit;
  291 
  292         if (MHLEN > sizeof(struct ip) + ICMP_MINLEN + icmplen)
  293                 m = m_gethdr(M_NOWAIT, MT_DATA);
  294         else
  295                 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
  296         if (m == NULL)
  297                 goto freeit;
  298 #ifdef MAC
  299         mac_netinet_icmp_reply(n, m);
  300 #endif
  301         icmplen = min(icmplen, M_TRAILINGSPACE(m) - sizeof(struct ip) - ICMP_MINLEN);
  302         m_align(m, sizeof(struct ip) + ICMP_MINLEN + icmplen);
  303         m->m_data += sizeof(struct ip);
  304         m->m_len = ICMP_MINLEN + icmplen;
  305 
  306         /* XXX MRT  make the outgoing packet use the same FIB
  307          * that was associated with the incoming packet
  308          */
  309         M_SETFIB(m, M_GETFIB(n));
  310         icp = mtod(m, struct icmp *);
  311         ICMPSTAT_INC(icps_outhist[type]);
  312         icp->icmp_type = type;
  313         if (type == ICMP_REDIRECT)
  314                 icp->icmp_gwaddr.s_addr = dest;
  315         else {
  316                 icp->icmp_void = 0;
  317                 /*
  318                  * The following assignments assume an overlay with the
  319                  * just zeroed icmp_void field.
  320                  */
  321                 if (type == ICMP_PARAMPROB) {
  322                         icp->icmp_pptr = code;
  323                         code = 0;
  324                 } else if (type == ICMP_UNREACH &&
  325                         code == ICMP_UNREACH_NEEDFRAG && mtu) {
  326                         icp->icmp_nextmtu = htons(mtu);
  327                 }
  328         }
  329         icp->icmp_code = code;
  330 
  331         /*
  332          * Copy the quotation into ICMP message and
  333          * convert quoted IP header back to network representation.
  334          */
  335         m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip);
  336         nip = &icp->icmp_ip;
  337 
  338         /*
  339          * Set up ICMP message mbuf and copy old IP header (without options
  340          * in front of ICMP message.
  341          * If the original mbuf was meant to bypass the firewall, the error
  342          * reply should bypass as well.
  343          */
  344         m->m_flags |= n->m_flags & M_SKIP_FIREWALL;
  345         KASSERT(M_LEADINGSPACE(m) >= sizeof(struct ip),
  346             ("insufficient space for ip header"));
  347         m->m_data -= sizeof(struct ip);
  348         m->m_len += sizeof(struct ip);
  349         m->m_pkthdr.len = m->m_len;
  350         m->m_pkthdr.rcvif = n->m_pkthdr.rcvif;
  351         nip = mtod(m, struct ip *);
  352         bcopy((caddr_t)oip, (caddr_t)nip, sizeof(struct ip));
  353         nip->ip_len = htons(m->m_len);
  354         nip->ip_v = IPVERSION;
  355         nip->ip_hl = 5;
  356         nip->ip_p = IPPROTO_ICMP;
  357         nip->ip_tos = 0;
  358         nip->ip_off = 0;
  359 
  360         if (V_error_keeptags)
  361                 m_tag_copy_chain(m, n, M_NOWAIT);
  362 
  363         icmp_reflect(m);
  364 
  365 freeit:
  366         m_freem(n);
  367 }
  368 
  369 /*
  370  * Process a received ICMP message.
  371  */
  372 void
  373 icmp_input(struct mbuf *m, int off)
  374 {
  375         struct icmp *icp;
  376         struct in_ifaddr *ia;
  377         struct ip *ip = mtod(m, struct ip *);
  378         struct sockaddr_in icmpsrc, icmpdst, icmpgw;
  379         int hlen = off;
  380         int icmplen = ntohs(ip->ip_len) - off;
  381         int i, code;
  382         void (*ctlfunc)(int, struct sockaddr *, void *);
  383         int fibnum;
  384 
  385         /*
  386          * Locate icmp structure in mbuf, and check
  387          * that not corrupted and of at least minimum length.
  388          */
  389 #ifdef ICMPPRINTFS
  390         if (icmpprintfs) {
  391                 char buf[4 * sizeof "123"];
  392                 strcpy(buf, inet_ntoa(ip->ip_src));
  393                 printf("icmp_input from %s to %s, len %d\n",
  394                        buf, inet_ntoa(ip->ip_dst), icmplen);
  395         }
  396 #endif
  397         if (icmplen < ICMP_MINLEN) {
  398                 ICMPSTAT_INC(icps_tooshort);
  399                 goto freeit;
  400         }
  401         i = hlen + min(icmplen, ICMP_ADVLENMIN);
  402         if (m->m_len < i && (m = m_pullup(m, i)) == NULL)  {
  403                 ICMPSTAT_INC(icps_tooshort);
  404                 return;
  405         }
  406         ip = mtod(m, struct ip *);
  407         m->m_len -= hlen;
  408         m->m_data += hlen;
  409         icp = mtod(m, struct icmp *);
  410         if (in_cksum(m, icmplen)) {
  411                 ICMPSTAT_INC(icps_checksum);
  412                 goto freeit;
  413         }
  414         m->m_len += hlen;
  415         m->m_data -= hlen;
  416 
  417         if (m->m_pkthdr.rcvif && m->m_pkthdr.rcvif->if_type == IFT_FAITH) {
  418                 /*
  419                  * Deliver very specific ICMP type only.
  420                  */
  421                 switch (icp->icmp_type) {
  422                 case ICMP_UNREACH:
  423                 case ICMP_TIMXCEED:
  424                         break;
  425                 default:
  426                         goto freeit;
  427                 }
  428         }
  429 
  430 #ifdef ICMPPRINTFS
  431         if (icmpprintfs)
  432                 printf("icmp_input, type %d code %d\n", icp->icmp_type,
  433                     icp->icmp_code);
  434 #endif
  435 
  436         /*
  437          * Message type specific processing.
  438          */
  439         if (icp->icmp_type > ICMP_MAXTYPE)
  440                 goto raw;
  441 
  442         /* Initialize */
  443         bzero(&icmpsrc, sizeof(icmpsrc));
  444         icmpsrc.sin_len = sizeof(struct sockaddr_in);
  445         icmpsrc.sin_family = AF_INET;
  446         bzero(&icmpdst, sizeof(icmpdst));
  447         icmpdst.sin_len = sizeof(struct sockaddr_in);
  448         icmpdst.sin_family = AF_INET;
  449         bzero(&icmpgw, sizeof(icmpgw));
  450         icmpgw.sin_len = sizeof(struct sockaddr_in);
  451         icmpgw.sin_family = AF_INET;
  452 
  453         ICMPSTAT_INC(icps_inhist[icp->icmp_type]);
  454         code = icp->icmp_code;
  455         switch (icp->icmp_type) {
  456 
  457         case ICMP_UNREACH:
  458                 switch (code) {
  459                         case ICMP_UNREACH_NET:
  460                         case ICMP_UNREACH_HOST:
  461                         case ICMP_UNREACH_SRCFAIL:
  462                         case ICMP_UNREACH_NET_UNKNOWN:
  463                         case ICMP_UNREACH_HOST_UNKNOWN:
  464                         case ICMP_UNREACH_ISOLATED:
  465                         case ICMP_UNREACH_TOSNET:
  466                         case ICMP_UNREACH_TOSHOST:
  467                         case ICMP_UNREACH_HOST_PRECEDENCE:
  468                         case ICMP_UNREACH_PRECEDENCE_CUTOFF:
  469                                 code = PRC_UNREACH_NET;
  470                                 break;
  471 
  472                         case ICMP_UNREACH_NEEDFRAG:
  473                                 code = PRC_MSGSIZE;
  474                                 break;
  475 
  476                         /*
  477                          * RFC 1122, Sections 3.2.2.1 and 4.2.3.9.
  478                          * Treat subcodes 2,3 as immediate RST
  479                          */
  480                         case ICMP_UNREACH_PROTOCOL:
  481                         case ICMP_UNREACH_PORT:
  482                                 code = PRC_UNREACH_PORT;
  483                                 break;
  484 
  485                         case ICMP_UNREACH_NET_PROHIB:
  486                         case ICMP_UNREACH_HOST_PROHIB:
  487                         case ICMP_UNREACH_FILTER_PROHIB:
  488                                 code = PRC_UNREACH_ADMIN_PROHIB;
  489                                 break;
  490 
  491                         default:
  492                                 goto badcode;
  493                 }
  494                 goto deliver;
  495 
  496         case ICMP_TIMXCEED:
  497                 if (code > 1)
  498                         goto badcode;
  499                 code += PRC_TIMXCEED_INTRANS;
  500                 goto deliver;
  501 
  502         case ICMP_PARAMPROB:
  503                 if (code > 1)
  504                         goto badcode;
  505                 code = PRC_PARAMPROB;
  506                 goto deliver;
  507 
  508         case ICMP_SOURCEQUENCH:
  509                 if (code)
  510                         goto badcode;
  511                 code = PRC_QUENCH;
  512         deliver:
  513                 /*
  514                  * Problem with datagram; advise higher level routines.
  515                  */
  516                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  517                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
  518                         ICMPSTAT_INC(icps_badlen);
  519                         goto freeit;
  520                 }
  521                 /* Discard ICMP's in response to multicast packets */
  522                 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
  523                         goto badcode;
  524 #ifdef ICMPPRINTFS
  525                 if (icmpprintfs)
  526                         printf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
  527 #endif
  528                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  529                 /*
  530                  * XXX if the packet contains [IPv4 AH TCP], we can't make a
  531                  * notification to TCP layer.
  532                  */
  533                 ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput;
  534                 if (ctlfunc)
  535                         (*ctlfunc)(code, (struct sockaddr *)&icmpsrc,
  536                                    (void *)&icp->icmp_ip);
  537                 break;
  538 
  539         badcode:
  540                 ICMPSTAT_INC(icps_badcode);
  541                 break;
  542 
  543         case ICMP_ECHO:
  544                 if (!V_icmpbmcastecho
  545                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
  546                         ICMPSTAT_INC(icps_bmcastecho);
  547                         break;
  548                 }
  549                 icp->icmp_type = ICMP_ECHOREPLY;
  550                 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
  551                         goto freeit;
  552                 else
  553                         goto reflect;
  554 
  555         case ICMP_TSTAMP:
  556                 if (V_icmptstamprepl == 0)
  557                         break;
  558                 if (!V_icmpbmcastecho
  559                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
  560                         ICMPSTAT_INC(icps_bmcasttstamp);
  561                         break;
  562                 }
  563                 if (icmplen < ICMP_TSLEN) {
  564                         ICMPSTAT_INC(icps_badlen);
  565                         break;
  566                 }
  567                 icp->icmp_type = ICMP_TSTAMPREPLY;
  568                 icp->icmp_rtime = iptime();
  569                 icp->icmp_ttime = icp->icmp_rtime;      /* bogus, do later! */
  570                 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
  571                         goto freeit;
  572                 else
  573                         goto reflect;
  574 
  575         case ICMP_MASKREQ:
  576                 if (V_icmpmaskrepl == 0)
  577                         break;
  578                 /*
  579                  * We are not able to respond with all ones broadcast
  580                  * unless we receive it over a point-to-point interface.
  581                  */
  582                 if (icmplen < ICMP_MASKLEN)
  583                         break;
  584                 switch (ip->ip_dst.s_addr) {
  585 
  586                 case INADDR_BROADCAST:
  587                 case INADDR_ANY:
  588                         icmpdst.sin_addr = ip->ip_src;
  589                         break;
  590 
  591                 default:
  592                         icmpdst.sin_addr = ip->ip_dst;
  593                 }
  594                 ia = (struct in_ifaddr *)ifaof_ifpforaddr(
  595                             (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
  596                 if (ia == NULL)
  597                         break;
  598                 if (ia->ia_ifp == NULL) {
  599                         ifa_free(&ia->ia_ifa);
  600                         break;
  601                 }
  602                 icp->icmp_type = ICMP_MASKREPLY;
  603                 if (V_icmpmaskfake == 0)
  604                         icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr;
  605                 else
  606                         icp->icmp_mask = V_icmpmaskfake;
  607                 if (ip->ip_src.s_addr == 0) {
  608                         if (ia->ia_ifp->if_flags & IFF_BROADCAST)
  609                             ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr;
  610                         else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT)
  611                             ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr;
  612                 }
  613                 ifa_free(&ia->ia_ifa);
  614 reflect:
  615                 ICMPSTAT_INC(icps_reflect);
  616                 ICMPSTAT_INC(icps_outhist[icp->icmp_type]);
  617                 icmp_reflect(m);
  618                 return;
  619 
  620         case ICMP_REDIRECT:
  621                 if (V_log_redirect) {
  622                         u_long src, dst, gw;
  623 
  624                         src = ntohl(ip->ip_src.s_addr);
  625                         dst = ntohl(icp->icmp_ip.ip_dst.s_addr);
  626                         gw = ntohl(icp->icmp_gwaddr.s_addr);
  627                         printf("icmp redirect from %d.%d.%d.%d: "
  628                                "%d.%d.%d.%d => %d.%d.%d.%d\n",
  629                                (int)(src >> 24), (int)((src >> 16) & 0xff),
  630                                (int)((src >> 8) & 0xff), (int)(src & 0xff),
  631                                (int)(dst >> 24), (int)((dst >> 16) & 0xff),
  632                                (int)((dst >> 8) & 0xff), (int)(dst & 0xff),
  633                                (int)(gw >> 24), (int)((gw >> 16) & 0xff),
  634                                (int)((gw >> 8) & 0xff), (int)(gw & 0xff));
  635                 }
  636                 /*
  637                  * RFC1812 says we must ignore ICMP redirects if we
  638                  * are acting as router.
  639                  */
  640                 if (V_drop_redirect || V_ipforwarding)
  641                         break;
  642                 if (code > 3)
  643                         goto badcode;
  644                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
  645                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
  646                         ICMPSTAT_INC(icps_badlen);
  647                         break;
  648                 }
  649                 /*
  650                  * Short circuit routing redirects to force
  651                  * immediate change in the kernel's routing
  652                  * tables.  The message is also handed to anyone
  653                  * listening on a raw socket (e.g. the routing
  654                  * daemon for use in updating its tables).
  655                  */
  656                 icmpgw.sin_addr = ip->ip_src;
  657                 icmpdst.sin_addr = icp->icmp_gwaddr;
  658 #ifdef  ICMPPRINTFS
  659                 if (icmpprintfs) {
  660                         char buf[4 * sizeof "123"];
  661                         strcpy(buf, inet_ntoa(icp->icmp_ip.ip_dst));
  662 
  663                         printf("redirect dst %s to %s\n",
  664                                buf, inet_ntoa(icp->icmp_gwaddr));
  665                 }
  666 #endif
  667                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
  668                 for ( fibnum = 0; fibnum < rt_numfibs; fibnum++) {
  669                         in_rtredirect((struct sockaddr *)&icmpsrc,
  670                           (struct sockaddr *)&icmpdst,
  671                           (struct sockaddr *)0, RTF_GATEWAY | RTF_HOST,
  672                           (struct sockaddr *)&icmpgw, fibnum);
  673                 }
  674                 pfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
  675                 break;
  676 
  677         /*
  678          * No kernel processing for the following;
  679          * just fall through to send to raw listener.
  680          */
  681         case ICMP_ECHOREPLY:
  682         case ICMP_ROUTERADVERT:
  683         case ICMP_ROUTERSOLICIT:
  684         case ICMP_TSTAMPREPLY:
  685         case ICMP_IREQREPLY:
  686         case ICMP_MASKREPLY:
  687         default:
  688                 break;
  689         }
  690 
  691 raw:
  692         rip_input(m, off);
  693         return;
  694 
  695 freeit:
  696         m_freem(m);
  697 }
  698 
  699 /*
  700  * Reflect the ip packet back to the source
  701  */
  702 static void
  703 icmp_reflect(struct mbuf *m)
  704 {
  705         struct ip *ip = mtod(m, struct ip *);
  706         struct ifaddr *ifa;
  707         struct ifnet *ifp;
  708         struct in_ifaddr *ia;
  709         struct in_addr t;
  710         struct mbuf *opts = 0;
  711         int optlen = (ip->ip_hl << 2) - sizeof(struct ip);
  712 
  713         if (IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
  714             IN_EXPERIMENTAL(ntohl(ip->ip_src.s_addr)) ||
  715             IN_ZERONET(ntohl(ip->ip_src.s_addr)) ) {
  716                 m_freem(m);     /* Bad return address */
  717                 ICMPSTAT_INC(icps_badaddr);
  718                 goto done;      /* Ip_output() will check for broadcast */
  719         }
  720 
  721         t = ip->ip_dst;
  722         ip->ip_dst = ip->ip_src;
  723 
  724         /*
  725          * Source selection for ICMP replies:
  726          *
  727          * If the incoming packet was addressed directly to one of our
  728          * own addresses, use dst as the src for the reply.
  729          */
  730         IN_IFADDR_RLOCK();
  731         LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash) {
  732                 if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr) {
  733                         t = IA_SIN(ia)->sin_addr;
  734                         IN_IFADDR_RUNLOCK();
  735                         goto match;
  736                 }
  737         }
  738         IN_IFADDR_RUNLOCK();
  739 
  740         /*
  741          * If the incoming packet was addressed to one of our broadcast
  742          * addresses, use the first non-broadcast address which corresponds
  743          * to the incoming interface.
  744          */
  745         ifp = m->m_pkthdr.rcvif;
  746         if (ifp != NULL && ifp->if_flags & IFF_BROADCAST) {
  747                 IF_ADDR_RLOCK(ifp);
  748                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
  749                         if (ifa->ifa_addr->sa_family != AF_INET)
  750                                 continue;
  751                         ia = ifatoia(ifa);
  752                         if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
  753                             t.s_addr) {
  754                                 t = IA_SIN(ia)->sin_addr;
  755                                 IF_ADDR_RUNLOCK(ifp);
  756                                 goto match;
  757                         }
  758                 }
  759                 IF_ADDR_RUNLOCK(ifp);
  760         }
  761         /*
  762          * If the packet was transiting through us, use the address of
  763          * the interface the packet came through in.  If that interface
  764          * doesn't have a suitable IP address, the normal selection
  765          * criteria apply.
  766          */
  767         if (V_icmp_rfi && ifp != NULL) {
  768                 IF_ADDR_RLOCK(ifp);
  769                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
  770                         if (ifa->ifa_addr->sa_family != AF_INET)
  771                                 continue;
  772                         ia = ifatoia(ifa);
  773                         t = IA_SIN(ia)->sin_addr;
  774                         IF_ADDR_RUNLOCK(ifp);
  775                         goto match;
  776                 }
  777                 IF_ADDR_RUNLOCK(ifp);
  778         }
  779         /*
  780          * If the incoming packet was not addressed directly to us, use
  781          * designated interface for icmp replies specified by sysctl
  782          * net.inet.icmp.reply_src (default not set). Otherwise continue
  783          * with normal source selection.
  784          */
  785         if (V_reply_src[0] != '\0' && (ifp = ifunit(V_reply_src))) {
  786                 IF_ADDR_RLOCK(ifp);
  787                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
  788                         if (ifa->ifa_addr->sa_family != AF_INET)
  789                                 continue;
  790                         ia = ifatoia(ifa);
  791                         t = IA_SIN(ia)->sin_addr;
  792                         IF_ADDR_RUNLOCK(ifp);
  793                         goto match;
  794                 }
  795                 IF_ADDR_RUNLOCK(ifp);
  796         }
  797         /*
  798          * If the packet was transiting through us, use the address of
  799          * the interface that is the closest to the packet source.
  800          * When we don't have a route back to the packet source, stop here
  801          * and drop the packet.
  802          */
  803         ia = ip_rtaddr(ip->ip_dst, M_GETFIB(m));
  804         if (ia == NULL) {
  805                 m_freem(m);
  806                 ICMPSTAT_INC(icps_noroute);
  807                 goto done;
  808         }
  809         t = IA_SIN(ia)->sin_addr;
  810         ifa_free(&ia->ia_ifa);
  811 match:
  812 #ifdef MAC
  813         mac_netinet_icmp_replyinplace(m);
  814 #endif
  815         ip->ip_src = t;
  816         ip->ip_ttl = V_ip_defttl;
  817 
  818         if (optlen > 0) {
  819                 register u_char *cp;
  820                 int opt, cnt;
  821                 u_int len;
  822 
  823                 /*
  824                  * Retrieve any source routing from the incoming packet;
  825                  * add on any record-route or timestamp options.
  826                  */
  827                 cp = (u_char *) (ip + 1);
  828                 if ((opts = ip_srcroute(m)) == 0 &&
  829                     (opts = m_gethdr(M_NOWAIT, MT_DATA))) {
  830                         opts->m_len = sizeof(struct in_addr);
  831                         mtod(opts, struct in_addr *)->s_addr = 0;
  832                 }
  833                 if (opts) {
  834 #ifdef ICMPPRINTFS
  835                     if (icmpprintfs)
  836                             printf("icmp_reflect optlen %d rt %d => ",
  837                                 optlen, opts->m_len);
  838 #endif
  839                     for (cnt = optlen; cnt > 0; cnt -= len, cp += len) {
  840                             opt = cp[IPOPT_OPTVAL];
  841                             if (opt == IPOPT_EOL)
  842                                     break;
  843                             if (opt == IPOPT_NOP)
  844                                     len = 1;
  845                             else {
  846                                     if (cnt < IPOPT_OLEN + sizeof(*cp))
  847                                             break;
  848                                     len = cp[IPOPT_OLEN];
  849                                     if (len < IPOPT_OLEN + sizeof(*cp) ||
  850                                         len > cnt)
  851                                             break;
  852                             }
  853                             /*
  854                              * Should check for overflow, but it "can't happen"
  855                              */
  856                             if (opt == IPOPT_RR || opt == IPOPT_TS ||
  857                                 opt == IPOPT_SECURITY) {
  858                                     bcopy((caddr_t)cp,
  859                                         mtod(opts, caddr_t) + opts->m_len, len);
  860                                     opts->m_len += len;
  861                             }
  862                     }
  863                     /* Terminate & pad, if necessary */
  864                     cnt = opts->m_len % 4;
  865                     if (cnt) {
  866                             for (; cnt < 4; cnt++) {
  867                                     *(mtod(opts, caddr_t) + opts->m_len) =
  868                                         IPOPT_EOL;
  869                                     opts->m_len++;
  870                             }
  871                     }
  872 #ifdef ICMPPRINTFS
  873                     if (icmpprintfs)
  874                             printf("%d\n", opts->m_len);
  875 #endif
  876                 }
  877                 ip_stripoptions(m);
  878         }
  879         m_tag_delete_nonpersistent(m);
  880         m->m_flags &= ~(M_BCAST|M_MCAST);
  881         icmp_send(m, opts);
  882 done:
  883         if (opts)
  884                 (void)m_free(opts);
  885 }
  886 
  887 /*
  888  * Send an icmp packet back to the ip level,
  889  * after supplying a checksum.
  890  */
  891 static void
  892 icmp_send(struct mbuf *m, struct mbuf *opts)
  893 {
  894         register struct ip *ip = mtod(m, struct ip *);
  895         register int hlen;
  896         register struct icmp *icp;
  897 
  898         hlen = ip->ip_hl << 2;
  899         m->m_data += hlen;
  900         m->m_len -= hlen;
  901         icp = mtod(m, struct icmp *);
  902         icp->icmp_cksum = 0;
  903         icp->icmp_cksum = in_cksum(m, ntohs(ip->ip_len) - hlen);
  904         m->m_data -= hlen;
  905         m->m_len += hlen;
  906         m->m_pkthdr.rcvif = (struct ifnet *)0;
  907 #ifdef ICMPPRINTFS
  908         if (icmpprintfs) {
  909                 char buf[4 * sizeof "123"];
  910                 strcpy(buf, inet_ntoa(ip->ip_dst));
  911                 printf("icmp_send dst %s src %s\n",
  912                        buf, inet_ntoa(ip->ip_src));
  913         }
  914 #endif
  915         (void) ip_output(m, opts, NULL, 0, NULL, NULL);
  916 }
  917 
  918 /*
  919  * Return milliseconds since 00:00 GMT in network format.
  920  */
  921 uint32_t
  922 iptime(void)
  923 {
  924         struct timeval atv;
  925         u_long t;
  926 
  927         getmicrotime(&atv);
  928         t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000;
  929         return (htonl(t));
  930 }
  931 
  932 /*
  933  * Return the next larger or smaller MTU plateau (table from RFC 1191)
  934  * given current value MTU.  If DIR is less than zero, a larger plateau
  935  * is returned; otherwise, a smaller value is returned.
  936  */
  937 int
  938 ip_next_mtu(int mtu, int dir)
  939 {
  940         static int mtutab[] = {
  941                 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1280, 1006, 508,
  942                 296, 68, 0
  943         };
  944         int i, size;
  945 
  946         size = (sizeof mtutab) / (sizeof mtutab[0]);
  947         if (dir >= 0) {
  948                 for (i = 0; i < size; i++)
  949                         if (mtu > mtutab[i])
  950                                 return mtutab[i];
  951         } else {
  952                 for (i = size - 1; i >= 0; i--)
  953                         if (mtu < mtutab[i])
  954                                 return mtutab[i];
  955                 if (mtu == mtutab[0])
  956                         return mtutab[0];
  957         }
  958         return 0;
  959 }
  960 #endif /* INET */
  961 
  962 
  963 /*
  964  * badport_bandlim() - check for ICMP bandwidth limit
  965  *
  966  *      Return 0 if it is ok to send an ICMP error response, -1 if we have
  967  *      hit our bandwidth limit and it is not ok.
  968  *
  969  *      If icmplim is <= 0, the feature is disabled and 0 is returned.
  970  *
  971  *      For now we separate the TCP and UDP subsystems w/ different 'which'
  972  *      values.  We may eventually remove this separation (and simplify the
  973  *      code further).
  974  *
  975  *      Note that the printing of the error message is delayed so we can
  976  *      properly print the icmp error rate that the system was trying to do
  977  *      (i.e. 22000/100 pps, etc...).  This can cause long delays in printing
  978  *      the 'final' error, but it doesn't make sense to solve the printing
  979  *      delay with more complex code.
  980  */
  981 
  982 int
  983 badport_bandlim(int which)
  984 {
  985 
  986 #define N(a)    (sizeof (a) / sizeof (a[0]))
  987         static struct rate {
  988                 const char      *type;
  989                 struct timeval  lasttime;
  990                 int             curpps;
  991         } rates[BANDLIM_MAX+1] = {
  992                 { "icmp unreach response" },
  993                 { "icmp ping response" },
  994                 { "icmp tstamp response" },
  995                 { "closed port RST response" },
  996                 { "open port RST response" },
  997                 { "icmp6 unreach response" },
  998                 { "sctp ootb response" }
  999         };
 1000 
 1001         /*
 1002          * Return ok status if feature disabled or argument out of range.
 1003          */
 1004         if (V_icmplim > 0 && (u_int) which < N(rates)) {
 1005                 struct rate *r = &rates[which];
 1006                 int opps = r->curpps;
 1007 
 1008                 if (!ppsratecheck(&r->lasttime, &r->curpps, V_icmplim))
 1009                         return -1;      /* discard packet */
 1010                 /*
 1011                  * If we've dropped below the threshold after having
 1012                  * rate-limited traffic print the message.  This preserves
 1013                  * the previous behaviour at the expense of added complexity.
 1014                  */
 1015                 if (V_icmplim_output && opps > V_icmplim)
 1016                         log(LOG_NOTICE, "Limiting %s from %d to %d packets/sec\n",
 1017                                 r->type, opps, V_icmplim);
 1018         }
 1019         return 0;                       /* okay to send packet */
 1020 #undef N
 1021 }

Cache object: 64efef52ef1be21c91c56f7cca9fb53c


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