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Annotation of qemu/slirp/ip_icmp.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1982, 1986, 1988, 1993
        !             3:  *     The Regents of the University of California.  All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms, with or without
        !             6:  * modification, are permitted provided that the following conditions
        !             7:  * are met:
        !             8:  * 1. Redistributions of source code must retain the above copyright
        !             9:  *    notice, this list of conditions and the following disclaimer.
        !            10:  * 2. Redistributions in binary form must reproduce the above copyright
        !            11:  *    notice, this list of conditions and the following disclaimer in the
        !            12:  *    documentation and/or other materials provided with the distribution.
        !            13:  * 3. All advertising materials mentioning features or use of this software
        !            14:  *    must display the following acknowledgement:
        !            15:  *     This product includes software developed by the University of
        !            16:  *     California, Berkeley and its contributors.
        !            17:  * 4. Neither the name of the University nor the names of its contributors
        !            18:  *    may be used to endorse or promote products derived from this software
        !            19:  *    without specific prior written permission.
        !            20:  *
        !            21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            31:  * SUCH DAMAGE.
        !            32:  *
        !            33:  *     @(#)ip_icmp.c   8.2 (Berkeley) 1/4/94
        !            34:  * ip_icmp.c,v 1.7 1995/05/30 08:09:42 rgrimes Exp
        !            35:  */
        !            36: 
        !            37: #include "slirp.h"
        !            38: #include "ip_icmp.h"
        !            39: 
        !            40: struct icmpstat icmpstat;
        !            41: 
        !            42: /* The message sent when emulating PING */
        !            43: /* Be nice and tell them it's just a psuedo-ping packet */
        !            44: char icmp_ping_msg[] = "This is a psuedo-PING packet used by Slirp to emulate ICMP ECHO-REQUEST packets.\n";
        !            45: 
        !            46: /* list of actions for icmp_error() on RX of an icmp message */
        !            47: static int icmp_flush[19] = {
        !            48: /*  ECHO REPLY (0)  */   0,
        !            49:                         1,
        !            50:                         1,
        !            51: /* DEST UNREACH (3) */   1,
        !            52: /* SOURCE QUENCH (4)*/   1,
        !            53: /* REDIRECT (5) */       1,
        !            54:                         1,
        !            55:                         1,
        !            56: /* ECHO (8) */           0,
        !            57: /* ROUTERADVERT (9) */   1,
        !            58: /* ROUTERSOLICIT (10) */ 1,
        !            59: /* TIME EXCEEDED (11) */ 1,
        !            60: /* PARAMETER PROBLEM (12) */ 1,
        !            61: /* TIMESTAMP (13) */     0,
        !            62: /* TIMESTAMP REPLY (14) */ 0,
        !            63: /* INFO (15) */          0,
        !            64: /* INFO REPLY (16) */    0,
        !            65: /* ADDR MASK (17) */     0,
        !            66: /* ADDR MASK REPLY (18) */ 0 
        !            67: };
        !            68: 
        !            69: /*
        !            70:  * Process a received ICMP message.
        !            71:  */
        !            72: void
        !            73: icmp_input(m, hlen)
        !            74:      struct mbuf *m;
        !            75:      int hlen;
        !            76: {
        !            77:   register struct icmp *icp;
        !            78:   register struct ip *ip=mtod(m, struct ip *);
        !            79:   int icmplen=ip->ip_len;
        !            80:   /* int code; */
        !            81:        
        !            82:   DEBUG_CALL("icmp_input");
        !            83:   DEBUG_ARG("m = %lx", (long )m);
        !            84:   DEBUG_ARG("m_len = %d", m->m_len);
        !            85: 
        !            86:   icmpstat.icps_received++;
        !            87:        
        !            88:   /*
        !            89:    * Locate icmp structure in mbuf, and check
        !            90:    * that its not corrupted and of at least minimum length.
        !            91:    */
        !            92:   if (icmplen < ICMP_MINLEN) {          /* min 8 bytes payload */
        !            93:     icmpstat.icps_tooshort++;
        !            94:   freeit:
        !            95:     m_freem(m);
        !            96:     goto end_error;
        !            97:   }
        !            98: 
        !            99:   m->m_len -= hlen;
        !           100:   m->m_data += hlen;
        !           101:   icp = mtod(m, struct icmp *);
        !           102:   if (cksum(m, icmplen)) {
        !           103:     icmpstat.icps_checksum++;
        !           104:     goto freeit;
        !           105:   }
        !           106:   m->m_len += hlen;
        !           107:   m->m_data -= hlen;
        !           108:   
        !           109:   /*   icmpstat.icps_inhist[icp->icmp_type]++; */
        !           110:   /* code = icp->icmp_code; */
        !           111: 
        !           112:   DEBUG_ARG("icmp_type = %d", icp->icmp_type);
        !           113:   switch (icp->icmp_type) {
        !           114:   case ICMP_ECHO:
        !           115:     icp->icmp_type = ICMP_ECHOREPLY;
        !           116:     ip->ip_len += hlen;                     /* since ip_input subtracts this */
        !           117:     if (ip->ip_dst.s_addr == our_addr.s_addr || 
        !           118:        (ip->ip_dst.s_addr == (special_addr.s_addr|htonl(CTL_ALIAS))) ) {
        !           119:       icmp_reflect(m);
        !           120:     } else {
        !           121:       struct socket *so;
        !           122:       struct sockaddr_in addr;
        !           123:       if ((so = socreate()) == NULL) goto freeit;
        !           124:       if(udp_attach(so) == -1) {
        !           125:        DEBUG_MISC((dfd,"icmp_input udp_attach errno = %d-%s\n", 
        !           126:                    errno,strerror(errno)));
        !           127:        sofree(so);
        !           128:        m_free(m);
        !           129:        goto end_error;
        !           130:       }
        !           131:       so->so_m = m;
        !           132:       so->so_faddr = ip->ip_dst;
        !           133:       so->so_fport = htons(7);
        !           134:       so->so_laddr = ip->ip_src;
        !           135:       so->so_lport = htons(9);
        !           136:       so->so_iptos = ip->ip_tos;
        !           137:       so->so_type = IPPROTO_ICMP;
        !           138:       so->so_state = SS_ISFCONNECTED;
        !           139:       
        !           140:       /* Send the packet */
        !           141:       addr.sin_family = AF_INET;
        !           142:       if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr) {
        !           143:        /* It's an alias */
        !           144:        switch(ntohl(so->so_faddr.s_addr) & 0xff) {
        !           145:        case CTL_DNS:
        !           146:          addr.sin_addr = dns_addr;
        !           147:          break;
        !           148:        case CTL_ALIAS:
        !           149:        default:
        !           150:          addr.sin_addr = loopback_addr;
        !           151:          break;
        !           152:        }
        !           153:       } else {
        !           154:        addr.sin_addr = so->so_faddr;
        !           155:       }
        !           156:       addr.sin_port = so->so_fport;
        !           157:       if(sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
        !           158:                (struct sockaddr *)&addr, sizeof(addr)) == -1) {
        !           159:        DEBUG_MISC((dfd,"icmp_input udp sendto tx errno = %d-%s\n",
        !           160:                    errno,strerror(errno)));
        !           161:        icmp_error(m, ICMP_UNREACH,ICMP_UNREACH_NET, 0,strerror(errno)); 
        !           162:        udp_detach(so);
        !           163:       }
        !           164:     } /* if ip->ip_dst.s_addr == our_addr.s_addr */
        !           165:     break;
        !           166:   case ICMP_UNREACH:
        !           167:     /* XXX? report error? close socket? */
        !           168:   case ICMP_TIMXCEED:
        !           169:   case ICMP_PARAMPROB:
        !           170:   case ICMP_SOURCEQUENCH:
        !           171:   case ICMP_TSTAMP:
        !           172:   case ICMP_MASKREQ:
        !           173:   case ICMP_REDIRECT:
        !           174:     icmpstat.icps_notsupp++;
        !           175:     m_freem(m);
        !           176:     break;
        !           177:     
        !           178:   default:
        !           179:     icmpstat.icps_badtype++;
        !           180:     m_freem(m);
        !           181:   } /* swith */
        !           182: 
        !           183: end_error:
        !           184:   /* m is m_free()'d xor put in a socket xor or given to ip_send */
        !           185:   return;
        !           186: }
        !           187: 
        !           188: 
        !           189: /*
        !           190:  *     Send an ICMP message in response to a situation
        !           191:  *
        !           192:  *     RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
        !           193:  *                     MUST NOT change this header information.
        !           194:  *                     MUST NOT reply to a multicast/broadcast IP address.
        !           195:  *                     MUST NOT reply to a multicast/broadcast MAC address.
        !           196:  *                     MUST reply to only the first fragment.
        !           197:  */
        !           198: /*
        !           199:  * Send ICMP_UNREACH back to the source regarding msrc.
        !           200:  * mbuf *msrc is used as a template, but is NOT m_free()'d.
        !           201:  * It is reported as the bad ip packet.  The header should
        !           202:  * be fully correct and in host byte order.
        !           203:  * ICMP fragmentation is illegal.  All machines must accept 576 bytes in one 
        !           204:  * packet.  The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
        !           205:  */
        !           206: 
        !           207: #define ICMP_MAXDATALEN (IP_MSS-28)
        !           208: void
        !           209: icmp_error(msrc, type, code, minsize, message)
        !           210:      struct mbuf *msrc;
        !           211:      u_char type;
        !           212:      u_char code;
        !           213:      int minsize;
        !           214:      char *message;
        !           215: {
        !           216:   unsigned hlen, shlen, s_ip_len;
        !           217:   register struct ip *ip;
        !           218:   register struct icmp *icp;
        !           219:   register struct mbuf *m;
        !           220: 
        !           221:   DEBUG_CALL("icmp_error");
        !           222:   DEBUG_ARG("msrc = %lx", (long )msrc);
        !           223:   DEBUG_ARG("msrc_len = %d", msrc->m_len);
        !           224: 
        !           225:   if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
        !           226: 
        !           227:   /* check msrc */
        !           228:   if(!msrc) goto end_error;
        !           229:   ip = mtod(msrc, struct ip *);
        !           230: #if DEBUG  
        !           231:   { char bufa[20], bufb[20];
        !           232:     strcpy(bufa, inet_ntoa(ip->ip_src));
        !           233:     strcpy(bufb, inet_ntoa(ip->ip_dst));
        !           234:     DEBUG_MISC((dfd, " %.16s to %.16s\n", bufa, bufb));
        !           235:   }
        !           236: #endif
        !           237:   if(ip->ip_off & IP_OFFMASK) goto end_error;    /* Only reply to fragment 0 */
        !           238: 
        !           239:   shlen=ip->ip_hl << 2;
        !           240:   s_ip_len=ip->ip_len;
        !           241:   if(ip->ip_p == IPPROTO_ICMP) {
        !           242:     icp = (struct icmp *)((char *)ip + shlen);
        !           243:     /*
        !           244:      * Assume any unknown ICMP type is an error. This isn't
        !           245:      * specified by the RFC, but think about it..
        !           246:      */
        !           247:     if(icp->icmp_type>18 || icmp_flush[icp->icmp_type]) goto end_error;
        !           248:   }
        !           249: 
        !           250:   /* make a copy */
        !           251:   if(!(m=m_get())) goto end_error;               /* get mbuf */
        !           252:   { int new_m_size;
        !           253:     new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
        !           254:     if(new_m_size>m->m_size) m_inc(m, new_m_size);
        !           255:   }
        !           256:   memcpy(m->m_data, msrc->m_data, msrc->m_len);
        !           257:   m->m_len = msrc->m_len;                        /* copy msrc to m */
        !           258: 
        !           259:   /* make the header of the reply packet */
        !           260:   ip  = mtod(m, struct ip *);
        !           261:   hlen= sizeof(struct ip );     /* no options in reply */
        !           262:   
        !           263:   /* fill in icmp */
        !           264:   m->m_data += hlen;                  
        !           265:   m->m_len -= hlen;
        !           266: 
        !           267:   icp = mtod(m, struct icmp *);
        !           268: 
        !           269:   if(minsize) s_ip_len=shlen+ICMP_MINLEN;   /* return header+8b only */
        !           270:   else if(s_ip_len>ICMP_MAXDATALEN)         /* maximum size */
        !           271:     s_ip_len=ICMP_MAXDATALEN;
        !           272: 
        !           273:   m->m_len=ICMP_MINLEN+s_ip_len;        /* 8 bytes ICMP header */  
        !           274: 
        !           275:   /* min. size = 8+sizeof(struct ip)+8 */
        !           276: 
        !           277:   icp->icmp_type = type;
        !           278:   icp->icmp_code = code;
        !           279:   icp->icmp_id = 0;
        !           280:   icp->icmp_seq = 0;
        !           281: 
        !           282:   memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len);   /* report the ip packet */
        !           283:   HTONS(icp->icmp_ip.ip_len);
        !           284:   HTONS(icp->icmp_ip.ip_id);
        !           285:   HTONS(icp->icmp_ip.ip_off);
        !           286: 
        !           287: #if DEBUG
        !           288:   if(message) {           /* DEBUG : append message to ICMP packet */
        !           289:     int message_len;
        !           290:     char *cpnt;
        !           291:     message_len=strlen(message);
        !           292:     if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
        !           293:     cpnt=(char *)m->m_data+m->m_len;
        !           294:     memcpy(cpnt, message, message_len);
        !           295:     m->m_len+=message_len;
        !           296:   }
        !           297: #endif
        !           298: 
        !           299:   icp->icmp_cksum = 0;
        !           300:   icp->icmp_cksum = cksum(m, m->m_len);
        !           301: 
        !           302:   m->m_data -= hlen;
        !           303:   m->m_len += hlen;
        !           304: 
        !           305:   /* fill in ip */
        !           306:   ip->ip_hl = hlen >> 2;
        !           307:   ip->ip_len = m->m_len;
        !           308:   
        !           309:   ip->ip_tos=((ip->ip_tos & 0x1E) | 0xC0);  /* high priority for errors */
        !           310: 
        !           311:   ip->ip_ttl = MAXTTL;
        !           312:   ip->ip_p = IPPROTO_ICMP;
        !           313:   ip->ip_dst = ip->ip_src;    /* ip adresses */
        !           314:   ip->ip_src = our_addr;
        !           315: 
        !           316:   (void ) ip_output((struct socket *)NULL, m);
        !           317:   
        !           318:   icmpstat.icps_reflect++;
        !           319: 
        !           320: end_error:
        !           321:   return;
        !           322: }
        !           323: #undef ICMP_MAXDATALEN
        !           324: 
        !           325: /*
        !           326:  * Reflect the ip packet back to the source
        !           327:  */
        !           328: void
        !           329: icmp_reflect(m)
        !           330:      struct mbuf *m;
        !           331: {
        !           332:   register struct ip *ip = mtod(m, struct ip *);
        !           333:   int hlen = ip->ip_hl << 2;
        !           334:   int optlen = hlen - sizeof(struct ip );
        !           335:   register struct icmp *icp;
        !           336: 
        !           337:   /*
        !           338:    * Send an icmp packet back to the ip level,
        !           339:    * after supplying a checksum.
        !           340:    */
        !           341:   m->m_data += hlen;
        !           342:   m->m_len -= hlen;
        !           343:   icp = mtod(m, struct icmp *);
        !           344: 
        !           345:   icp->icmp_cksum = 0;
        !           346:   icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
        !           347: 
        !           348:   m->m_data -= hlen;
        !           349:   m->m_len += hlen;
        !           350: 
        !           351:   /* fill in ip */
        !           352:   if (optlen > 0) {
        !           353:     /*
        !           354:      * Strip out original options by copying rest of first
        !           355:      * mbuf's data back, and adjust the IP length.
        !           356:      */
        !           357:     memmove((caddr_t)(ip + 1), (caddr_t)ip + hlen,
        !           358:            (unsigned )(m->m_len - hlen));
        !           359:     hlen -= optlen;
        !           360:     ip->ip_hl = hlen >> 2;
        !           361:     ip->ip_len -= optlen;
        !           362:     m->m_len -= optlen;
        !           363:   }
        !           364: 
        !           365:   ip->ip_ttl = MAXTTL;
        !           366:   { /* swap */
        !           367:     struct in_addr icmp_dst;
        !           368:     icmp_dst = ip->ip_dst;
        !           369:     ip->ip_dst = ip->ip_src;
        !           370:     ip->ip_src = icmp_dst;
        !           371:   }
        !           372: 
        !           373:   (void ) ip_output((struct socket *)NULL, m);
        !           374: 
        !           375:   icmpstat.icps_reflect++;
        !           376: }

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