1 /* ip_input.c 1.34 82/03/23 */ 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 q = q->ipf_next; 302 while (q != (struct ipasfrag *)fp) { 303 t = dtom(q); 304 q = q->ipf_next; 305 m_cat(m, t); 306 } 307 308 /* 309 * Create header for new ip packet by 310 * modifying header of first packet; 311 * dequeue and discard fragment reassembly header. 312 * Make header visible. 313 */ 314 ip = fp->ipq_next; 315 ip->ip_len = next; 316 ((struct ip *)ip)->ip_src = fp->ipq_src; 317 ((struct ip *)ip)->ip_dst = fp->ipq_dst; 318 remque(fp); 319 (void) m_free(dtom(fp)); 320 m = dtom(ip); 321 m->m_len += sizeof (struct ipasfrag); 322 m->m_off -= sizeof (struct ipasfrag); 323 return ((struct ip *)ip); 324 325 dropfrag: 326 m_freem(m); 327 return (0); 328 } 329 330 /* 331 * Free a fragment reassembly header and all 332 * associated datagrams. 333 */ 334 struct ipq * 335 ip_freef(fp) 336 struct ipq *fp; 337 { 338 register struct ipasfrag *q; 339 struct mbuf *m; 340 COUNT(IP_FREEF); 341 342 for (q = fp->ipq_next; q != (struct ipasfrag *)fp; q = q->ipf_next) 343 m_freem(dtom(q)); 344 m = dtom(fp); 345 fp = fp->next; 346 remque(fp->prev); 347 (void) m_free(m); 348 return (fp); 349 } 350 351 /* 352 * Put an ip fragment on a reassembly chain. 353 * Like insque, but pointers in middle of structure. 354 */ 355 ip_enq(p, prev) 356 register struct ipasfrag *p, *prev; 357 { 358 359 COUNT(IP_ENQ); 360 p->ipf_prev = prev; 361 p->ipf_next = prev->ipf_next; 362 prev->ipf_next->ipf_prev = p; 363 prev->ipf_next = p; 364 } 365 366 /* 367 * To ip_enq as remque is to insque. 368 */ 369 ip_deq(p) 370 register struct ipasfrag *p; 371 { 372 373 COUNT(IP_DEQ); 374 p->ipf_prev->ipf_next = p->ipf_next; 375 p->ipf_next->ipf_prev = p->ipf_prev; 376 } 377 378 /* 379 * IP timer processing; 380 * if a timer expires on a reassembly 381 * queue, discard it. 382 */ 383 ip_slowtimo() 384 { 385 register struct ipq *fp; 386 int s = splnet(); 387 388 COUNT(IP_SLOWTIMO); 389 fp = ipq.next; 390 if (fp == 0) { 391 splx(s); 392 return; 393 } 394 while (fp != &ipq) 395 if (--fp->ipq_ttl == 0) 396 fp = ip_freef(fp); 397 else 398 fp = fp->next; 399 splx(s); 400 } 401 402 /* 403 * Drain off all datagram fragments. 404 */ 405 ip_drain() 406 { 407 408 COUNT(IP_DRAIN); 409 while (ipq.next != &ipq) 410 (void) ip_freef(ipq.next); 411 } 412 413 /* 414 * Do option processing on a datagram, 415 * possibly discarding it if bad options 416 * are encountered. 417 */ 418 ip_dooptions(ip) 419 struct ip *ip; 420 { 421 register u_char *cp; 422 int opt, optlen, cnt; 423 struct in_addr *sin; 424 register struct ip_timestamp *ipt; 425 register struct ifnet *ifp; 426 struct in_addr t; 427 428 COUNT(IP_DOOPTIONS); 429 cp = (u_char *)(ip + 1); 430 cnt = (ip->ip_hl << 2) - sizeof (struct ip); 431 for (; cnt > 0; cnt -= optlen, cp += optlen) { 432 opt = cp[0]; 433 if (opt == IPOPT_EOL) 434 break; 435 if (opt == IPOPT_NOP) 436 optlen = 1; 437 else 438 optlen = cp[1]; 439 switch (opt) { 440 441 default: 442 break; 443 444 /* 445 * Source routing with record. 446 * Find interface with current destination address. 447 * If none on this machine then drop if strictly routed, 448 * or do nothing if loosely routed. 449 * Record interface address and bring up next address 450 * component. If strictly routed make sure next 451 * address on directly accessible net. 452 */ 453 case IPOPT_LSRR: 454 if (cp[2] < 4 || cp[2] > optlen - (sizeof (long) - 1)) 455 break; 456 sin = (struct in_addr *)(cp + cp[2]); 457 ifp = if_ifwithaddr(*sin); 458 if (ifp == 0) { 459 if (opt == IPOPT_SSRR) 460 goto bad; 461 break; 462 } 463 t = ip->ip_dst; ip->ip_dst = *sin; *sin = t; 464 cp[2] += 4; 465 if (cp[2] > optlen - (sizeof (long) - 1)) 466 break; 467 ip->ip_dst = sin[1]; 468 if (opt == IPOPT_SSRR && if_ifonnetof(ip->ip_dst)==0) 469 goto bad; 470 break; 471 472 case IPOPT_TS: 473 ipt = (struct ip_timestamp *)cp; 474 if (ipt->ipt_len < 5) 475 goto bad; 476 if (ipt->ipt_ptr > ipt->ipt_len - sizeof (long)) { 477 if (++ipt->ipt_oflw == 0) 478 goto bad; 479 break; 480 } 481 sin = (struct in_addr *)(cp+cp[2]); 482 switch (ipt->ipt_flg) { 483 484 case IPOPT_TS_TSONLY: 485 break; 486 487 case IPOPT_TS_TSANDADDR: 488 if (ipt->ipt_ptr + 8 > ipt->ipt_len) 489 goto bad; 490 /* stamp with ``first'' interface address */ 491 *sin++ = ifnet->if_addr; 492 break; 493 494 case IPOPT_TS_PRESPEC: 495 if (if_ifwithaddr(*sin) == 0) 496 continue; 497 if (ipt->ipt_ptr + 8 > ipt->ipt_len) 498 goto bad; 499 ipt->ipt_ptr += 4; 500 break; 501 502 default: 503 goto bad; 504 } 505 *(n_time *)sin = iptime(); 506 ipt->ipt_ptr += 4; 507 } 508 } 509 return; 510 bad: 511 /* SHOULD FORCE ICMP MESSAGE */ 512 return; 513 } 514 515 /* 516 * Strip out IP options, at higher 517 * level protocol in the kernel. 518 * Second argument is buffer to which options 519 * will be moved, and return value is their length. 520 */ 521 ip_stripoptions(ip, mopt) 522 struct ip *ip; 523 struct mbuf *mopt; 524 { 525 register int i; 526 register struct mbuf *m; 527 int olen; 528 COUNT(IP_STRIPOPTIONS); 529 530 olen = (ip->ip_hl<<2) - sizeof (struct ip); 531 m = dtom(ip); 532 ip++; 533 if (mopt) { 534 mopt->m_len = olen; 535 mopt->m_off = MMINOFF; 536 bcopy((caddr_t)ip, mtod(m, caddr_t), (unsigned)olen); 537 } 538 i = m->m_len - (sizeof (struct ip) + olen); 539 bcopy((caddr_t)ip+olen, (caddr_t)ip, (unsigned)i); 540 m->m_len -= olen; 541 } 542