1 /* ip_input.c 1.33 82/03/19 */ 2 3 #include "../h/param.h" 4 #include "../h/systm.h" 5 #include "../h/clock.h" 6 #include "../h/mbuf.h" 7 #include "../h/protosw.h" 8 #include "../h/socket.h" 9 #include "../net/in.h" 10 #include "../net/in_systm.h" 11 #include "../net/if.h" 12 #include "../net/ip.h" /* belongs before in.h */ 13 #include "../net/ip_var.h" 14 #include "../net/ip_icmp.h" 15 #include "../net/tcp.h" 16 17 u_char ip_protox[IPPROTO_MAX]; 18 int ipqmaxlen = IFQ_MAXLEN; 19 20 /* 21 * IP initialization: fill in IP protocol switch table. 22 * All protocols not implemented in kernel go to raw IP protocol handler. 23 */ 24 ip_init() 25 { 26 register struct protosw *pr; 27 register int i; 28 29 COUNT(IP_INIT); 30 pr = pffindproto(PF_INET, IPPROTO_RAW); 31 if (pr == 0) 32 panic("ip_init"); 33 for (i = 0; i < IPPROTO_MAX; i++) 34 ip_protox[i] = pr - protosw; 35 for (pr = protosw; pr <= protoswLAST; pr++) 36 if (pr->pr_family == PF_INET && 37 pr->pr_protocol && pr->pr_protocol != IPPROTO_RAW) 38 ip_protox[pr->pr_protocol] = pr - protosw; 39 ipq.next = ipq.prev = &ipq; 40 ip_id = time & 0xffff; 41 ipintrq.ifq_maxlen = ipqmaxlen; 42 } 43 44 u_char ipcksum = 1; 45 struct ip *ip_reass(); 46 47 /* 48 * Ip input routine. Checksum and byte swap header. If fragmented 49 * try to reassamble. If complete and fragment queue exists, discard. 50 * Process options. Pass to next level. 51 */ 52 ipintr() 53 { 54 register struct ip *ip; 55 register struct mbuf *m; 56 struct mbuf *m0, *mopt; 57 register int i; 58 register struct ipq *fp; 59 int hlen, s; 60 61 COUNT(IPINTR); 62 next: 63 /* 64 * Get next datagram off input queue and get IP header 65 * in first mbuf. 66 */ 67 s = splimp(); 68 IF_DEQUEUE(&ipintrq, m); 69 splx(s); 70 if (m == 0) 71 return; 72 if ((m->m_off > MMAXOFF || m->m_len < sizeof (struct ip)) && 73 (m = m_pullup(m, sizeof (struct ip))) == 0) 74 return; 75 ip = mtod(m, struct ip *); 76 if ((hlen = ip->ip_hl << 2) > m->m_len) { 77 if ((m = m_pullup(m, hlen)) == 0) 78 return; 79 ip = mtod(m, struct ip *); 80 } 81 if (ipcksum) 82 if (ip->ip_sum = in_cksum(m, hlen)) { 83 printf("ip_sum %x\n", ip->ip_sum); /* XXX */ 84 ipstat.ips_badsum++; 85 goto bad; 86 } 87 88 #if vax 89 /* 90 * Convert fields to host representation. 91 */ 92 ip->ip_len = ntohs((u_short)ip->ip_len); 93 ip->ip_id = ntohs(ip->ip_id); 94 ip->ip_off = ntohs((u_short)ip->ip_off); 95 #endif 96 97 /* 98 * Check that the amount of data in the buffers 99 * is as at least much as the IP header would have us expect. 100 * Trim mbufs if longer than we expect. 101 * Drop packet if shorter than we expect. 102 */ 103 i = 0; 104 m0 = m; 105 for (; m != NULL; m = m->m_next) { 106 if (m->m_free) panic("ipinput already free"); 107 i += m->m_len; 108 } 109 m = m0; 110 if (i != ip->ip_len) { 111 if (i < ip->ip_len) { 112 ipstat.ips_tooshort++; 113 goto bad; 114 } 115 m_adj(m, ip->ip_len - i); 116 } 117 118 /* 119 * Process options and, if not destined for us, 120 * ship it on. 121 */ 122 if (hlen > sizeof (struct ip)) 123 ip_dooptions(ip); 124 if (ifnet && ip->ip_dst.s_addr != ifnet->if_addr.s_addr && 125 if_ifwithaddr(ip->ip_dst) == 0) { 126 127 goto bad; 128 #ifdef notdef 129 printf("ip->ip_dst %x ip->ip_ttl %x\n", 130 ip->ip_dst, ip->ip_ttl); 131 if (--ip->ip_ttl == 0) { 132 icmp_error(ip, ICMP_TIMXCEED, 0); 133 goto next; 134 } 135 mopt = m_get(M_DONTWAIT); 136 if (mopt == 0) 137 goto bad; 138 ip_stripoptions(ip, mopt); 139 /* 0 here means no directed broadcast */ 140 (void) ip_output(m0, mopt, 0); 141 goto next; 142 #endif 143 } 144 145 /* 146 * Look for queue of fragments 147 * of this datagram. 148 */ 149 for (fp = ipq.next; fp != &ipq; fp = fp->next) 150 if (ip->ip_id == fp->ipq_id && 151 ip->ip_src.s_addr == fp->ipq_src.s_addr && 152 ip->ip_dst.s_addr == fp->ipq_dst.s_addr && 153 ip->ip_p == fp->ipq_p) 154 goto found; 155 fp = 0; 156 found: 157 158 /* 159 * Adjust ip_len to not reflect header, 160 * set ip_mff if more fragments are expected, 161 * convert offset of this to bytes. 162 */ 163 ip->ip_len -= hlen; 164 ((struct ipasfrag *)ip)->ipf_mff = 0; 165 if (ip->ip_off & IP_MF) 166 ((struct ipasfrag *)ip)->ipf_mff = 1; 167 ip->ip_off <<= 3; 168 169 /* 170 * If datagram marked as having more fragments 171 * or if this is not the first fragment, 172 * attempt reassembly; if it succeeds, proceed. 173 */ 174 if (((struct ipasfrag *)ip)->ipf_mff || ip->ip_off) { 175 ip = ip_reass((struct ipasfrag *)ip, fp); 176 if (ip == 0) 177 goto next; 178 hlen = ip->ip_hl << 2; 179 m = dtom(ip); 180 } else 181 if (fp) 182 (void) ip_freef(fp); 183 184 /* 185 * Switch out to protocol's input routine. 186 */ 187 (*protosw[ip_protox[ip->ip_p]].pr_input)(m); 188 goto next; 189 bad: 190 m_freem(m); 191 goto next; 192 } 193 194 /* 195 * Take incoming datagram fragment and try to 196 * reassemble it into whole datagram. If a chain for 197 * reassembly of this datagram already exists, then it 198 * is given as fp; otherwise have to make a chain. 199 */ 200 struct ip * 201 ip_reass(ip, fp) 202 register struct ipasfrag *ip; 203 register struct ipq *fp; 204 { 205 register struct mbuf *m = dtom(ip); 206 register struct ipasfrag *q; 207 struct mbuf *t; 208 int hlen = ip->ip_hl << 2; 209 int i, next; 210 COUNT(IP_REASS); 211 212 /* 213 * Presence of header sizes in mbufs 214 * would confuse code below. 215 */ 216 m->m_off += hlen; 217 m->m_len -= hlen; 218 219 /* 220 * If first fragment to arrive, create a reassembly queue. 221 */ 222 if (fp == 0) { 223 if ((t = m_get(M_WAIT)) == NULL) 224 goto dropfrag; 225 t->m_off = MMINOFF; 226 fp = mtod(t, struct ipq *); 227 insque(fp, &ipq); 228 fp->ipq_ttl = IPFRAGTTL; 229 fp->ipq_p = ip->ip_p; 230 fp->ipq_id = ip->ip_id; 231 fp->ipq_next = fp->ipq_prev = (struct ipasfrag *)fp; 232 fp->ipq_src = ((struct ip *)ip)->ip_src; 233 fp->ipq_dst = ((struct ip *)ip)->ip_dst; 234 q = (struct ipasfrag *)fp; 235 goto insert; 236 } 237 238 /* 239 * Find a segment which begins after this one does. 240 */ 241 for (q = fp->ipq_next; q != (struct ipasfrag *)fp; q = q->ipf_next) 242 if (q->ip_off > ip->ip_off) 243 break; 244 245 /* 246 * If there is a preceding segment, it may provide some of 247 * our data already. If so, drop the data from the incoming 248 * segment. If it provides all of our data, drop us. 249 */ 250 if (q->ipf_prev != (struct ipasfrag *)fp) { 251 i = q->ipf_prev->ip_off + q->ipf_prev->ip_len - ip->ip_off; 252 if (i > 0) { 253 if (i >= ip->ip_len) 254 goto dropfrag; 255 m_adj(dtom(ip), i); 256 ip->ip_off += i; 257 ip->ip_len -= i; 258 } 259 } 260 261 /* 262 * While we overlap succeeding segments trim them or, 263 * if they are completely covered, dequeue them. 264 */ 265 while (q != (struct ipasfrag *)fp && ip->ip_off + ip->ip_len > q->ip_off) { 266 i = (ip->ip_off + ip->ip_len) - q->ip_off; 267 if (i < q->ip_len) { 268 q->ip_len -= i; 269 q->ip_off += i; 270 m_adj(dtom(q), i); 271 break; 272 } 273 q = q->ipf_next; 274 m_freem(dtom(q->ipf_prev)); 275 ip_deq(q->ipf_prev); 276 } 277 278 insert: 279 /* 280 * Stick new segment in its place; 281 * check for complete reassembly. 282 */ 283 ip_enq(ip, q->ipf_prev); 284 next = 0; 285 for (q = fp->ipq_next; q != (struct ipasfrag *)fp; q = q->ipf_next) { 286 if (q->ip_off != next) 287 return (0); 288 next += q->ip_len; 289 } 290 if (q->ipf_prev->ipf_mff) 291 return (0); 292 293 /* 294 * Reassembly is complete; concatenate fragments. 295 */ 296 q = fp->ipq_next; 297 m = dtom(q); 298 t = m->m_next; 299 m->m_next = 0; 300 m_cat(m, t); 301 while ((q = q->ipf_next) != (struct ipasfrag *)fp) 302 m_cat(m, dtom(q)); 303 304 /* 305 * Create header for new ip packet by 306 * modifying header of first packet; 307 * dequeue and discard fragment reassembly header. 308 * Make header visible. 309 */ 310 ip = fp->ipq_next; 311 ip->ip_len = next; 312 ((struct ip *)ip)->ip_src = fp->ipq_src; 313 ((struct ip *)ip)->ip_dst = fp->ipq_dst; 314 remque(fp); 315 (void) m_free(dtom(fp)); 316 m = dtom(ip); 317 m->m_len += sizeof (struct ipasfrag); 318 m->m_off -= sizeof (struct ipasfrag); 319 return ((struct ip *)ip); 320 321 dropfrag: 322 m_freem(m); 323 return (0); 324 } 325 326 /* 327 * Free a fragment reassembly header and all 328 * associated datagrams. 329 */ 330 struct ipq * 331 ip_freef(fp) 332 struct ipq *fp; 333 { 334 register struct ipasfrag *q; 335 struct mbuf *m; 336 COUNT(IP_FREEF); 337 338 for (q = fp->ipq_next; q != (struct ipasfrag *)fp; q = q->ipf_next) 339 m_freem(dtom(q)); 340 m = dtom(fp); 341 fp = fp->next; 342 remque(fp->prev); 343 (void) m_free(m); 344 return (fp); 345 } 346 347 /* 348 * Put an ip fragment on a reassembly chain. 349 * Like insque, but pointers in middle of structure. 350 */ 351 ip_enq(p, prev) 352 register struct ipasfrag *p, *prev; 353 { 354 355 COUNT(IP_ENQ); 356 p->ipf_prev = prev; 357 p->ipf_next = prev->ipf_next; 358 prev->ipf_next->ipf_prev = p; 359 prev->ipf_next = p; 360 } 361 362 /* 363 * To ip_enq as remque is to insque. 364 */ 365 ip_deq(p) 366 register struct ipasfrag *p; 367 { 368 369 COUNT(IP_DEQ); 370 p->ipf_prev->ipf_next = p->ipf_next; 371 p->ipf_next->ipf_prev = p->ipf_prev; 372 } 373 374 /* 375 * IP timer processing; 376 * if a timer expires on a reassembly 377 * queue, discard it. 378 */ 379 ip_slowtimo() 380 { 381 register struct ipq *fp; 382 int s = splnet(); 383 384 COUNT(IP_SLOWTIMO); 385 fp = ipq.next; 386 if (fp == 0) { 387 splx(s); 388 return; 389 } 390 while (fp != &ipq) 391 if (--fp->ipq_ttl == 0) 392 fp = ip_freef(fp); 393 else 394 fp = fp->next; 395 splx(s); 396 } 397 398 /* 399 * Drain off all datagram fragments. 400 */ 401 ip_drain() 402 { 403 404 COUNT(IP_DRAIN); 405 while (ipq.next != &ipq) 406 (void) ip_freef(ipq.next); 407 } 408 409 /* 410 * Do option processing on a datagram, 411 * possibly discarding it if bad options 412 * are encountered. 413 */ 414 ip_dooptions(ip) 415 struct ip *ip; 416 { 417 register u_char *cp; 418 int opt, optlen, cnt; 419 struct in_addr *sin; 420 register struct ip_timestamp *ipt; 421 register struct ifnet *ifp; 422 struct in_addr t; 423 424 COUNT(IP_DOOPTIONS); 425 cp = (u_char *)(ip + 1); 426 cnt = (ip->ip_hl << 2) - sizeof (struct ip); 427 for (; cnt > 0; cnt -= optlen, cp += optlen) { 428 opt = cp[0]; 429 if (opt == IPOPT_EOL) 430 break; 431 if (opt == IPOPT_NOP) 432 optlen = 1; 433 else 434 optlen = cp[1]; 435 switch (opt) { 436 437 default: 438 break; 439 440 /* 441 * Source routing with record. 442 * Find interface with current destination address. 443 * If none on this machine then drop if strictly routed, 444 * or do nothing if loosely routed. 445 * Record interface address and bring up next address 446 * component. If strictly routed make sure next 447 * address on directly accessible net. 448 */ 449 case IPOPT_LSRR: 450 if (cp[2] < 4 || cp[2] > optlen - (sizeof (long) - 1)) 451 break; 452 sin = (struct in_addr *)(cp + cp[2]); 453 ifp = if_ifwithaddr(*sin); 454 if (ifp == 0) { 455 if (opt == IPOPT_SSRR) 456 goto bad; 457 break; 458 } 459 t = ip->ip_dst; ip->ip_dst = *sin; *sin = t; 460 cp[2] += 4; 461 if (cp[2] > optlen - (sizeof (long) - 1)) 462 break; 463 ip->ip_dst = sin[1]; 464 if (opt == IPOPT_SSRR && if_ifonnetof(ip->ip_dst)==0) 465 goto bad; 466 break; 467 468 case IPOPT_TS: 469 ipt = (struct ip_timestamp *)cp; 470 if (ipt->ipt_len < 5) 471 goto bad; 472 if (ipt->ipt_ptr > ipt->ipt_len - sizeof (long)) { 473 if (++ipt->ipt_oflw == 0) 474 goto bad; 475 break; 476 } 477 sin = (struct in_addr *)(cp+cp[2]); 478 switch (ipt->ipt_flg) { 479 480 case IPOPT_TS_TSONLY: 481 break; 482 483 case IPOPT_TS_TSANDADDR: 484 if (ipt->ipt_ptr + 8 > ipt->ipt_len) 485 goto bad; 486 /* stamp with ``first'' interface address */ 487 *sin++ = ifnet->if_addr; 488 break; 489 490 case IPOPT_TS_PRESPEC: 491 if (if_ifwithaddr(*sin) == 0) 492 continue; 493 if (ipt->ipt_ptr + 8 > ipt->ipt_len) 494 goto bad; 495 ipt->ipt_ptr += 4; 496 break; 497 498 default: 499 goto bad; 500 } 501 *(n_time *)sin = iptime(); 502 ipt->ipt_ptr += 4; 503 } 504 } 505 return; 506 bad: 507 /* SHOULD FORCE ICMP MESSAGE */ 508 return; 509 } 510 511 /* 512 * Strip out IP options, at higher 513 * level protocol in the kernel. 514 * Second argument is buffer to which options 515 * will be moved, and return value is their length. 516 */ 517 ip_stripoptions(ip, mopt) 518 struct ip *ip; 519 struct mbuf *mopt; 520 { 521 register int i; 522 register struct mbuf *m; 523 int olen; 524 COUNT(IP_STRIPOPTIONS); 525 526 olen = (ip->ip_hl<<2) - sizeof (struct ip); 527 m = dtom(ip); 528 ip++; 529 if (mopt) { 530 mopt->m_len = olen; 531 mopt->m_off = MMINOFF; 532 bcopy((caddr_t)ip, mtod(m, caddr_t), (unsigned)olen); 533 } 534 i = m->m_len - (sizeof (struct ip) + olen); 535 bcopy((caddr_t)ip+olen, (caddr_t)ip, (unsigned)i); 536 m->m_len -= olen; 537 } 538