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      1 /*
      2  * Copyright (c) 1982, 1986, 1988, 1993
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. Neither the name of the University nor the names of its contributors
     14  *    may be used to endorse or promote products derived from this software
     15  *    without specific prior written permission.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     27  * SUCH DAMAGE.
     28  *
     29  *	@(#)ip_icmp.c	8.2 (Berkeley) 1/4/94
     30  * ip_icmp.c,v 1.7 1995/05/30 08:09:42 rgrimes Exp
     31  */
     32 
     33 #include "slirp.h"
     34 #include "ip_icmp.h"
     35 #include "android/sockets.h"
     36 
     37 #ifdef LOG_ENABLED
     38 struct icmpstat icmpstat;
     39 #endif
     40 
     41 /* The message sent when emulating PING */
     42 /* Be nice and tell them it's just a pseudo-ping packet */
     43 static const char icmp_ping_msg[] = "This is a pseudo-PING packet used by Slirp to emulate ICMP ECHO-REQUEST packets.\n";
     44 
     45 /* list of actions for icmp_error() on RX of an icmp message */
     46 static const int icmp_flush[19] = {
     47 /*  ECHO REPLY (0)  */   0,
     48 		         1,
     49 		         1,
     50 /* DEST UNREACH (3) */   1,
     51 /* SOURCE QUENCH (4)*/   1,
     52 /* REDIRECT (5) */       1,
     53 		         1,
     54 		         1,
     55 /* ECHO (8) */           0,
     56 /* ROUTERADVERT (9) */   1,
     57 /* ROUTERSOLICIT (10) */ 1,
     58 /* TIME EXCEEDED (11) */ 1,
     59 /* PARAMETER PROBLEM (12) */ 1,
     60 /* TIMESTAMP (13) */     0,
     61 /* TIMESTAMP REPLY (14) */ 0,
     62 /* INFO (15) */          0,
     63 /* INFO REPLY (16) */    0,
     64 /* ADDR MASK (17) */     0,
     65 /* ADDR MASK REPLY (18) */ 0
     66 };
     67 
     68 /*
     69  * Process a received ICMP message.
     70  */
     71 void
     72 icmp_input(struct mbuf *m, int hlen)
     73 {
     74   register struct icmp *icp;
     75   register struct ip *ip=mtod(m, struct ip *);
     76   int icmplen=ip->ip_len;
     77   /* int code; */
     78 
     79   DEBUG_CALL("icmp_input");
     80   DEBUG_ARG("m = %lx", (long )m);
     81   DEBUG_ARG("m_len = %d", m->m_len);
     82 
     83   STAT(icmpstat.icps_received++);
     84 
     85   /*
     86    * Locate icmp structure in mbuf, and check
     87    * that its not corrupted and of at least minimum length.
     88    */
     89   if (icmplen < ICMP_MINLEN) {          /* min 8 bytes payload */
     90     STAT(icmpstat.icps_tooshort++);
     91   freeit:
     92     m_freem(m);
     93     goto end_error;
     94   }
     95 
     96   m->m_len -= hlen;
     97   m->m_data += hlen;
     98   icp = mtod(m, struct icmp *);
     99   if (cksum(m, icmplen)) {
    100     STAT(icmpstat.icps_checksum++);
    101     goto freeit;
    102   }
    103   m->m_len += hlen;
    104   m->m_data -= hlen;
    105 
    106   /*	icmpstat.icps_inhist[icp->icmp_type]++; */
    107   /* code = icp->icmp_code; */
    108 
    109   DEBUG_ARG("icmp_type = %d", icp->icmp_type);
    110   switch (icp->icmp_type) {
    111   case ICMP_ECHO:
    112     icp->icmp_type = ICMP_ECHOREPLY;
    113     ip->ip_len += hlen;	             /* since ip_input subtracts this */
    114     if (ip_geth(ip->ip_dst) == alias_addr_ip) {
    115       icmp_reflect(m);
    116     } else {
    117       struct socket *so;
    118       SockAddress  addr;
    119       uint32_t     addr_ip;
    120       uint16_t     addr_port;
    121 
    122       if ((so = socreate()) == NULL) goto freeit;
    123       if(udp_attach(so) == -1) {
    124 	DEBUG_MISC((dfd,"icmp_input udp_attach errno = %d-%s\n",
    125 		    errno,errno_str));
    126 	sofree(so);
    127 	m_free(m);
    128 	goto end_error;
    129       }
    130       so->so_m = m;
    131       so->so_faddr_ip   = ip_geth(ip->ip_dst);
    132       so->so_faddr_port = 7;
    133       so->so_laddr_ip   = ip_geth(ip->ip_src);
    134       so->so_laddr_port = 9;
    135       so->so_iptos = ip->ip_tos;
    136       so->so_type = IPPROTO_ICMP;
    137       so->so_state = SS_ISFCONNECTED;
    138 
    139       /* Send the packet */
    140       if ((so->so_faddr_ip & 0xffffff00) == special_addr_ip) {
    141         /* It's an alias */
    142         int  low = so->so_faddr_ip & 0xff;
    143 
    144         if (low >= CTL_DNS && low < CTL_DNS + dns_addr_count)
    145             addr_ip = dns_addr[low - CTL_DNS];
    146         else
    147             addr_ip = loopback_addr_ip;
    148       } else {
    149             addr_ip = so->so_faddr_ip;
    150       }
    151       addr_port = so->so_faddr_port;
    152 
    153       sock_address_init_inet( &addr, addr_ip, addr_port );
    154 
    155       if(socket_sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), &addr) < 0) {
    156         DEBUG_MISC((dfd,"icmp_input udp sendto tx errno = %d-%s\n",
    157                     errno,errno_str));
    158         icmp_error(m, ICMP_UNREACH,ICMP_UNREACH_NET, 0,errno_str);
    159         udp_detach(so);
    160       }
    161     } /* if ip->ip_dst.s_addr == alias_addr.s_addr */
    162     break;
    163   case ICMP_UNREACH:
    164     /* XXX? report error? close socket? */
    165   case ICMP_TIMXCEED:
    166   case ICMP_PARAMPROB:
    167   case ICMP_SOURCEQUENCH:
    168   case ICMP_TSTAMP:
    169   case ICMP_MASKREQ:
    170   case ICMP_REDIRECT:
    171     STAT(icmpstat.icps_notsupp++);
    172     m_freem(m);
    173     break;
    174 
    175   default:
    176     STAT(icmpstat.icps_badtype++);
    177     m_freem(m);
    178   } /* swith */
    179 
    180 end_error:
    181   /* m is m_free()'d xor put in a socket xor or given to ip_send */
    182   return;
    183 }
    184 
    185 
    186 /*
    187  *	Send an ICMP message in response to a situation
    188  *
    189  *	RFC 1122: 3.2.2	MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
    190  *			MUST NOT change this header information.
    191  *			MUST NOT reply to a multicast/broadcast IP address.
    192  *			MUST NOT reply to a multicast/broadcast MAC address.
    193  *			MUST reply to only the first fragment.
    194  */
    195 /*
    196  * Send ICMP_UNREACH back to the source regarding msrc.
    197  * mbuf *msrc is used as a template, but is NOT m_free()'d.
    198  * It is reported as the bad ip packet.  The header should
    199  * be fully correct and in host byte order.
    200  * ICMP fragmentation is illegal.  All machines must accept 576 bytes in one
    201  * packet.  The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
    202  */
    203 
    204 #define ICMP_MAXDATALEN (IP_MSS-28)
    205 void
    206 icmp_error(struct mbuf *msrc, u_char type, u_char code, int minsize,
    207            const char *message)
    208 {
    209   unsigned hlen, shlen, s_ip_len;
    210   register struct ip *ip;
    211   register struct icmp *icp;
    212   register struct mbuf *m;
    213 
    214   DEBUG_CALL("icmp_error");
    215   DEBUG_ARG("msrc = %lx", (long )msrc);
    216   DEBUG_ARG("msrc_len = %d", msrc->m_len);
    217 
    218   if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
    219 
    220   /* check msrc */
    221   if(!msrc) goto end_error;
    222   ip = mtod(msrc, struct ip *);
    223 #ifdef DEBUG
    224   { char bufa[20], bufb[20];
    225     strcpy(bufa, inet_iptostr(ip_geth(ip->ip_src)));
    226     strcpy(bufb, inet_iptostr(ip_geth(ip->ip_dst)));
    227     DEBUG_MISC((dfd, " %.16s to %.16s\n", bufa, bufb));
    228   }
    229 #endif
    230   if(ip->ip_off & IP_OFFMASK) goto end_error;    /* Only reply to fragment 0 */
    231 
    232   shlen=ip->ip_hl << 2;
    233   s_ip_len=ip->ip_len;
    234   if(ip->ip_p == IPPROTO_ICMP) {
    235     icp = (struct icmp *)((char *)ip + shlen);
    236     /*
    237      *	Assume any unknown ICMP type is an error. This isn't
    238      *	specified by the RFC, but think about it..
    239      */
    240     if(icp->icmp_type>18 || icmp_flush[icp->icmp_type]) goto end_error;
    241   }
    242 
    243   /* make a copy */
    244   if(!(m=m_get())) goto end_error;               /* get mbuf */
    245   { int new_m_size;
    246     new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
    247     if(new_m_size>m->m_size) m_inc(m, new_m_size);
    248   }
    249   memcpy(m->m_data, msrc->m_data, msrc->m_len);
    250   m->m_len = msrc->m_len;                        /* copy msrc to m */
    251 
    252   /* make the header of the reply packet */
    253   ip  = mtod(m, struct ip *);
    254   hlen= sizeof(struct ip );     /* no options in reply */
    255 
    256   /* fill in icmp */
    257   m->m_data += hlen;
    258   m->m_len -= hlen;
    259 
    260   icp = mtod(m, struct icmp *);
    261 
    262   if(minsize) s_ip_len=shlen+ICMP_MINLEN;   /* return header+8b only */
    263   else if(s_ip_len>ICMP_MAXDATALEN)         /* maximum size */
    264     s_ip_len=ICMP_MAXDATALEN;
    265 
    266   m->m_len=ICMP_MINLEN+s_ip_len;        /* 8 bytes ICMP header */
    267 
    268   /* min. size = 8+sizeof(struct ip)+8 */
    269 
    270   icp->icmp_type = type;
    271   icp->icmp_code = code;
    272   icp->icmp_id = 0;
    273   icp->icmp_seq = 0;
    274 
    275   memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len);   /* report the ip packet */
    276   HTONS(icp->icmp_ip.ip_len);
    277   HTONS(icp->icmp_ip.ip_id);
    278   HTONS(icp->icmp_ip.ip_off);
    279 
    280 #ifdef DEBUG
    281   if(message) {           /* DEBUG : append message to ICMP packet */
    282     int message_len;
    283     char *cpnt;
    284     message_len=strlen(message);
    285     if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
    286     cpnt=(char *)m->m_data+m->m_len;
    287     memcpy(cpnt, message, message_len);
    288     m->m_len+=message_len;
    289   }
    290 #endif
    291 
    292   icp->icmp_cksum = 0;
    293   icp->icmp_cksum = cksum(m, m->m_len);
    294 
    295   m->m_data -= hlen;
    296   m->m_len += hlen;
    297 
    298   /* fill in ip */
    299   ip->ip_hl = hlen >> 2;
    300   ip->ip_len = m->m_len;
    301 
    302   ip->ip_tos=((ip->ip_tos & 0x1E) | 0xC0);  /* high priority for errors */
    303 
    304   ip->ip_ttl = MAXTTL;
    305   ip->ip_p = IPPROTO_ICMP;
    306   ip->ip_dst = ip->ip_src;    /* ip adresses */
    307   ip->ip_src = ip_setn(alias_addr_ip);
    308 
    309   (void ) ip_output((struct socket *)NULL, m);
    310 
    311   STAT(icmpstat.icps_reflect++);
    312 
    313 end_error:
    314   return;
    315 }
    316 #undef ICMP_MAXDATALEN
    317 
    318 /*
    319  * Reflect the ip packet back to the source
    320  */
    321 void
    322 icmp_reflect(struct mbuf *m)
    323 {
    324   register struct ip *ip = mtod(m, struct ip *);
    325   int hlen = ip->ip_hl << 2;
    326   int optlen = hlen - sizeof(struct ip );
    327   register struct icmp *icp;
    328 
    329   /*
    330    * Send an icmp packet back to the ip level,
    331    * after supplying a checksum.
    332    */
    333   m->m_data += hlen;
    334   m->m_len -= hlen;
    335   icp = mtod(m, struct icmp *);
    336 
    337   icp->icmp_cksum = 0;
    338   icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
    339 
    340   m->m_data -= hlen;
    341   m->m_len += hlen;
    342 
    343   /* fill in ip */
    344   if (optlen > 0) {
    345     /*
    346      * Strip out original options by copying rest of first
    347      * mbuf's data back, and adjust the IP length.
    348      */
    349     memmove((caddr_t)(ip + 1), (caddr_t)ip + hlen,
    350 	    (unsigned )(m->m_len - hlen));
    351     hlen -= optlen;
    352     ip->ip_hl = hlen >> 2;
    353     ip->ip_len -= optlen;
    354     m->m_len -= optlen;
    355   }
    356 
    357   ip->ip_ttl = MAXTTL;
    358   { /* swap */
    359     ipaddr_t icmp_dst;
    360     icmp_dst   = ip->ip_dst;
    361     ip->ip_dst = ip->ip_src;
    362     ip->ip_src = icmp_dst;
    363   }
    364 
    365   (void ) ip_output((struct socket *)NULL, m);
    366 
    367   STAT(icmpstat.icps_reflect++);
    368 }
    369