1 /* 2 * INET An implementation of the TCP/IP protocol suite for the LINUX 3 * operating system. INET is implemented using the BSD Socket 4 * interface as the means of communication with the user level. 5 * 6 * The IP fragmentation functionality. 7 * 8 * Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG> 9 * Alan Cox <alan@lxorguk.ukuu.org.uk> 10 * 11 * Fixes: 12 * Alan Cox : Split from ip.c , see ip_input.c for history. 13 * David S. Miller : Begin massive cleanup... 14 * Andi Kleen : Add sysctls. 15 * xxxx : Overlapfrag bug. 16 * Ultima : ip_expire() kernel panic. 17 * Bill Hawes : Frag accounting and evictor fixes. 18 * John McDonald : 0 length frag bug. 19 * Alexey Kuznetsov: SMP races, threading, cleanup. 20 * Patrick McHardy : LRU queue of frag heads for evictor. 21 */ 22 23 #define pr_fmt(fmt) "IPv4: " fmt 24 25 #include <linux/compiler.h> 26 #include <linux/module.h> 27 #include <linux/types.h> 28 #include <linux/mm.h> 29 #include <linux/jiffies.h> 30 #include <linux/skbuff.h> 31 #include <linux/list.h> 32 #include <linux/ip.h> 33 #include <linux/icmp.h> 34 #include <linux/netdevice.h> 35 #include <linux/jhash.h> 36 #include <linux/random.h> 37 #include <linux/slab.h> 38 #include <net/route.h> 39 #include <net/dst.h> 40 #include <net/sock.h> 41 #include <net/ip.h> 42 #include <net/icmp.h> 43 #include <net/checksum.h> 44 #include <net/inetpeer.h> 45 #include <net/inet_frag.h> 46 #include <linux/tcp.h> 47 #include <linux/udp.h> 48 #include <linux/inet.h> 49 #include <linux/netfilter_ipv4.h> 50 #include <net/inet_ecn.h> 51 52 /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6 53 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c 54 * as well. Or notify me, at least. --ANK 55 */ 56 57 static int sysctl_ipfrag_max_dist __read_mostly = 64; 58 59 struct ipfrag_skb_cb 60 { 61 struct inet_skb_parm h; 62 int offset; 63 }; 64 65 #define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb)) 66 67 /* Describe an entry in the "incomplete datagrams" queue. */ 68 struct ipq { 69 struct inet_frag_queue q; 70 71 u32 user; 72 __be32 saddr; 73 __be32 daddr; 74 __be16 id; 75 u8 protocol; 76 u8 ecn; /* RFC3168 support */ 77 int iif; 78 unsigned int rid; 79 struct inet_peer *peer; 80 }; 81 82 /* RFC 3168 support : 83 * We want to check ECN values of all fragments, do detect invalid combinations. 84 * In ipq->ecn, we store the OR value of each ip4_frag_ecn() fragment value. 85 */ 86 #define IPFRAG_ECN_NOT_ECT 0x01 /* one frag had ECN_NOT_ECT */ 87 #define IPFRAG_ECN_ECT_1 0x02 /* one frag had ECN_ECT_1 */ 88 #define IPFRAG_ECN_ECT_0 0x04 /* one frag had ECN_ECT_0 */ 89 #define IPFRAG_ECN_CE 0x08 /* one frag had ECN_CE */ 90 91 static inline u8 ip4_frag_ecn(u8 tos) 92 { 93 return 1 << (tos & INET_ECN_MASK); 94 } 95 96 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements 97 * Value : 0xff if frame should be dropped. 98 * 0 or INET_ECN_CE value, to be ORed in to final iph->tos field 99 */ 100 static const u8 ip4_frag_ecn_table[16] = { 101 /* at least one fragment had CE, and others ECT_0 or ECT_1 */ 102 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = INET_ECN_CE, 103 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = INET_ECN_CE, 104 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = INET_ECN_CE, 105 106 /* invalid combinations : drop frame */ 107 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff, 108 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff, 109 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff, 110 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff, 111 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff, 112 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff, 113 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff, 114 }; 115 116 static struct inet_frags ip4_frags; 117 118 int ip_frag_nqueues(struct net *net) 119 { 120 return net->ipv4.frags.nqueues; 121 } 122 123 int ip_frag_mem(struct net *net) 124 { 125 return atomic_read(&net->ipv4.frags.mem); 126 } 127 128 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, 129 struct net_device *dev); 130 131 struct ip4_create_arg { 132 struct iphdr *iph; 133 u32 user; 134 }; 135 136 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot) 137 { 138 return jhash_3words((__force u32)id << 16 | prot, 139 (__force u32)saddr, (__force u32)daddr, 140 ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1); 141 } 142 143 static unsigned int ip4_hashfn(struct inet_frag_queue *q) 144 { 145 struct ipq *ipq; 146 147 ipq = container_of(q, struct ipq, q); 148 return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol); 149 } 150 151 static int ip4_frag_match(struct inet_frag_queue *q, void *a) 152 { 153 struct ipq *qp; 154 struct ip4_create_arg *arg = a; 155 156 qp = container_of(q, struct ipq, q); 157 return qp->id == arg->iph->id && 158 qp->saddr == arg->iph->saddr && 159 qp->daddr == arg->iph->daddr && 160 qp->protocol == arg->iph->protocol && 161 qp->user == arg->user; 162 } 163 164 /* Memory Tracking Functions. */ 165 static void frag_kfree_skb(struct netns_frags *nf, struct sk_buff *skb) 166 { 167 atomic_sub(skb->truesize, &nf->mem); 168 kfree_skb(skb); 169 } 170 171 static void ip4_frag_init(struct inet_frag_queue *q, void *a) 172 { 173 struct ipq *qp = container_of(q, struct ipq, q); 174 struct ip4_create_arg *arg = a; 175 176 qp->protocol = arg->iph->protocol; 177 qp->id = arg->iph->id; 178 qp->ecn = ip4_frag_ecn(arg->iph->tos); 179 qp->saddr = arg->iph->saddr; 180 qp->daddr = arg->iph->daddr; 181 qp->user = arg->user; 182 qp->peer = sysctl_ipfrag_max_dist ? 183 inet_getpeer_v4(arg->iph->saddr, 1) : NULL; 184 } 185 186 static __inline__ void ip4_frag_free(struct inet_frag_queue *q) 187 { 188 struct ipq *qp; 189 190 qp = container_of(q, struct ipq, q); 191 if (qp->peer) 192 inet_putpeer(qp->peer); 193 } 194 195 196 /* Destruction primitives. */ 197 198 static __inline__ void ipq_put(struct ipq *ipq) 199 { 200 inet_frag_put(&ipq->q, &ip4_frags); 201 } 202 203 /* Kill ipq entry. It is not destroyed immediately, 204 * because caller (and someone more) holds reference count. 205 */ 206 static void ipq_kill(struct ipq *ipq) 207 { 208 inet_frag_kill(&ipq->q, &ip4_frags); 209 } 210 211 /* Memory limiting on fragments. Evictor trashes the oldest 212 * fragment queue until we are back under the threshold. 213 */ 214 static void ip_evictor(struct net *net) 215 { 216 int evicted; 217 218 evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags); 219 if (evicted) 220 IP_ADD_STATS_BH(net, IPSTATS_MIB_REASMFAILS, evicted); 221 } 222 223 /* 224 * Oops, a fragment queue timed out. Kill it and send an ICMP reply. 225 */ 226 static void ip_expire(unsigned long arg) 227 { 228 struct ipq *qp; 229 struct net *net; 230 231 qp = container_of((struct inet_frag_queue *) arg, struct ipq, q); 232 net = container_of(qp->q.net, struct net, ipv4.frags); 233 234 spin_lock(&qp->q.lock); 235 236 if (qp->q.last_in & INET_FRAG_COMPLETE) 237 goto out; 238 239 ipq_kill(qp); 240 241 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT); 242 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); 243 244 if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) { 245 struct sk_buff *head = qp->q.fragments; 246 const struct iphdr *iph; 247 int err; 248 249 rcu_read_lock(); 250 head->dev = dev_get_by_index_rcu(net, qp->iif); 251 if (!head->dev) 252 goto out_rcu_unlock; 253 254 /* skb dst is stale, drop it, and perform route lookup again */ 255 skb_dst_drop(head); 256 iph = ip_hdr(head); 257 err = ip_route_input_noref(head, iph->daddr, iph->saddr, 258 iph->tos, head->dev); 259 if (err) 260 goto out_rcu_unlock; 261 262 /* 263 * Only an end host needs to send an ICMP 264 * "Fragment Reassembly Timeout" message, per RFC792. 265 */ 266 if (qp->user == IP_DEFRAG_AF_PACKET || 267 (qp->user == IP_DEFRAG_CONNTRACK_IN && 268 skb_rtable(head)->rt_type != RTN_LOCAL)) 269 goto out_rcu_unlock; 270 271 272 /* Send an ICMP "Fragment Reassembly Timeout" message. */ 273 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); 274 out_rcu_unlock: 275 rcu_read_unlock(); 276 } 277 out: 278 spin_unlock(&qp->q.lock); 279 ipq_put(qp); 280 } 281 282 /* Find the correct entry in the "incomplete datagrams" queue for 283 * this IP datagram, and create new one, if nothing is found. 284 */ 285 static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user) 286 { 287 struct inet_frag_queue *q; 288 struct ip4_create_arg arg; 289 unsigned int hash; 290 291 arg.iph = iph; 292 arg.user = user; 293 294 read_lock(&ip4_frags.lock); 295 hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol); 296 297 q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash); 298 if (q == NULL) 299 goto out_nomem; 300 301 return container_of(q, struct ipq, q); 302 303 out_nomem: 304 LIMIT_NETDEBUG(KERN_ERR pr_fmt("ip_frag_create: no memory left !\n")); 305 return NULL; 306 } 307 308 /* Is the fragment too far ahead to be part of ipq? */ 309 static inline int ip_frag_too_far(struct ipq *qp) 310 { 311 struct inet_peer *peer = qp->peer; 312 unsigned int max = sysctl_ipfrag_max_dist; 313 unsigned int start, end; 314 315 int rc; 316 317 if (!peer || !max) 318 return 0; 319 320 start = qp->rid; 321 end = atomic_inc_return(&peer->rid); 322 qp->rid = end; 323 324 rc = qp->q.fragments && (end - start) > max; 325 326 if (rc) { 327 struct net *net; 328 329 net = container_of(qp->q.net, struct net, ipv4.frags); 330 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); 331 } 332 333 return rc; 334 } 335 336 static int ip_frag_reinit(struct ipq *qp) 337 { 338 struct sk_buff *fp; 339 340 if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) { 341 atomic_inc(&qp->q.refcnt); 342 return -ETIMEDOUT; 343 } 344 345 fp = qp->q.fragments; 346 do { 347 struct sk_buff *xp = fp->next; 348 frag_kfree_skb(qp->q.net, fp); 349 fp = xp; 350 } while (fp); 351 352 qp->q.last_in = 0; 353 qp->q.len = 0; 354 qp->q.meat = 0; 355 qp->q.fragments = NULL; 356 qp->q.fragments_tail = NULL; 357 qp->iif = 0; 358 qp->ecn = 0; 359 360 return 0; 361 } 362 363 /* Add new segment to existing queue. */ 364 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb) 365 { 366 struct sk_buff *prev, *next; 367 struct net_device *dev; 368 int flags, offset; 369 int ihl, end; 370 int err = -ENOENT; 371 u8 ecn; 372 373 if (qp->q.last_in & INET_FRAG_COMPLETE) 374 goto err; 375 376 if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) && 377 unlikely(ip_frag_too_far(qp)) && 378 unlikely(err = ip_frag_reinit(qp))) { 379 ipq_kill(qp); 380 goto err; 381 } 382 383 ecn = ip4_frag_ecn(ip_hdr(skb)->tos); 384 offset = ntohs(ip_hdr(skb)->frag_off); 385 flags = offset & ~IP_OFFSET; 386 offset &= IP_OFFSET; 387 offset <<= 3; /* offset is in 8-byte chunks */ 388 ihl = ip_hdrlen(skb); 389 390 /* Determine the position of this fragment. */ 391 end = offset + skb->len - ihl; 392 err = -EINVAL; 393 394 /* Is this the final fragment? */ 395 if ((flags & IP_MF) == 0) { 396 /* If we already have some bits beyond end 397 * or have different end, the segment is corrupted. 398 */ 399 if (end < qp->q.len || 400 ((qp->q.last_in & INET_FRAG_LAST_IN) && end != qp->q.len)) 401 goto err; 402 qp->q.last_in |= INET_FRAG_LAST_IN; 403 qp->q.len = end; 404 } else { 405 if (end&7) { 406 end &= ~7; 407 if (skb->ip_summed != CHECKSUM_UNNECESSARY) 408 skb->ip_summed = CHECKSUM_NONE; 409 } 410 if (end > qp->q.len) { 411 /* Some bits beyond end -> corruption. */ 412 if (qp->q.last_in & INET_FRAG_LAST_IN) 413 goto err; 414 qp->q.len = end; 415 } 416 } 417 if (end == offset) 418 goto err; 419 420 err = -ENOMEM; 421 if (pskb_pull(skb, ihl) == NULL) 422 goto err; 423 424 err = pskb_trim_rcsum(skb, end - offset); 425 if (err) 426 goto err; 427 428 /* Find out which fragments are in front and at the back of us 429 * in the chain of fragments so far. We must know where to put 430 * this fragment, right? 431 */ 432 prev = qp->q.fragments_tail; 433 if (!prev || FRAG_CB(prev)->offset < offset) { 434 next = NULL; 435 goto found; 436 } 437 prev = NULL; 438 for (next = qp->q.fragments; next != NULL; next = next->next) { 439 if (FRAG_CB(next)->offset >= offset) 440 break; /* bingo! */ 441 prev = next; 442 } 443 444 found: 445 /* We found where to put this one. Check for overlap with 446 * preceding fragment, and, if needed, align things so that 447 * any overlaps are eliminated. 448 */ 449 if (prev) { 450 int i = (FRAG_CB(prev)->offset + prev->len) - offset; 451 452 if (i > 0) { 453 offset += i; 454 err = -EINVAL; 455 if (end <= offset) 456 goto err; 457 err = -ENOMEM; 458 if (!pskb_pull(skb, i)) 459 goto err; 460 if (skb->ip_summed != CHECKSUM_UNNECESSARY) 461 skb->ip_summed = CHECKSUM_NONE; 462 } 463 } 464 465 err = -ENOMEM; 466 467 while (next && FRAG_CB(next)->offset < end) { 468 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */ 469 470 if (i < next->len) { 471 /* Eat head of the next overlapped fragment 472 * and leave the loop. The next ones cannot overlap. 473 */ 474 if (!pskb_pull(next, i)) 475 goto err; 476 FRAG_CB(next)->offset += i; 477 qp->q.meat -= i; 478 if (next->ip_summed != CHECKSUM_UNNECESSARY) 479 next->ip_summed = CHECKSUM_NONE; 480 break; 481 } else { 482 struct sk_buff *free_it = next; 483 484 /* Old fragment is completely overridden with 485 * new one drop it. 486 */ 487 next = next->next; 488 489 if (prev) 490 prev->next = next; 491 else 492 qp->q.fragments = next; 493 494 qp->q.meat -= free_it->len; 495 frag_kfree_skb(qp->q.net, free_it); 496 } 497 } 498 499 FRAG_CB(skb)->offset = offset; 500 501 /* Insert this fragment in the chain of fragments. */ 502 skb->next = next; 503 if (!next) 504 qp->q.fragments_tail = skb; 505 if (prev) 506 prev->next = skb; 507 else 508 qp->q.fragments = skb; 509 510 dev = skb->dev; 511 if (dev) { 512 qp->iif = dev->ifindex; 513 skb->dev = NULL; 514 } 515 qp->q.stamp = skb->tstamp; 516 qp->q.meat += skb->len; 517 qp->ecn |= ecn; 518 atomic_add(skb->truesize, &qp->q.net->mem); 519 if (offset == 0) 520 qp->q.last_in |= INET_FRAG_FIRST_IN; 521 522 if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && 523 qp->q.meat == qp->q.len) 524 return ip_frag_reasm(qp, prev, dev); 525 526 write_lock(&ip4_frags.lock); 527 list_move_tail(&qp->q.lru_list, &qp->q.net->lru_list); 528 write_unlock(&ip4_frags.lock); 529 return -EINPROGRESS; 530 531 err: 532 kfree_skb(skb); 533 return err; 534 } 535 536 537 /* Build a new IP datagram from all its fragments. */ 538 539 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, 540 struct net_device *dev) 541 { 542 struct net *net = container_of(qp->q.net, struct net, ipv4.frags); 543 struct iphdr *iph; 544 struct sk_buff *fp, *head = qp->q.fragments; 545 int len; 546 int ihlen; 547 int err; 548 u8 ecn; 549 550 ipq_kill(qp); 551 552 ecn = ip4_frag_ecn_table[qp->ecn]; 553 if (unlikely(ecn == 0xff)) { 554 err = -EINVAL; 555 goto out_fail; 556 } 557 /* Make the one we just received the head. */ 558 if (prev) { 559 head = prev->next; 560 fp = skb_clone(head, GFP_ATOMIC); 561 if (!fp) 562 goto out_nomem; 563 564 fp->next = head->next; 565 if (!fp->next) 566 qp->q.fragments_tail = fp; 567 prev->next = fp; 568 569 skb_morph(head, qp->q.fragments); 570 head->next = qp->q.fragments->next; 571 572 kfree_skb(qp->q.fragments); 573 qp->q.fragments = head; 574 } 575 576 WARN_ON(head == NULL); 577 WARN_ON(FRAG_CB(head)->offset != 0); 578 579 /* Allocate a new buffer for the datagram. */ 580 ihlen = ip_hdrlen(head); 581 len = ihlen + qp->q.len; 582 583 err = -E2BIG; 584 if (len > 65535) 585 goto out_oversize; 586 587 /* Head of list must not be cloned. */ 588 if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC)) 589 goto out_nomem; 590 591 /* If the first fragment is fragmented itself, we split 592 * it to two chunks: the first with data and paged part 593 * and the second, holding only fragments. */ 594 if (skb_has_frag_list(head)) { 595 struct sk_buff *clone; 596 int i, plen = 0; 597 598 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL) 599 goto out_nomem; 600 clone->next = head->next; 601 head->next = clone; 602 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list; 603 skb_frag_list_init(head); 604 for (i = 0; i < skb_shinfo(head)->nr_frags; i++) 605 plen += skb_frag_size(&skb_shinfo(head)->frags[i]); 606 clone->len = clone->data_len = head->data_len - plen; 607 head->data_len -= clone->len; 608 head->len -= clone->len; 609 clone->csum = 0; 610 clone->ip_summed = head->ip_summed; 611 atomic_add(clone->truesize, &qp->q.net->mem); 612 } 613 614 skb_shinfo(head)->frag_list = head->next; 615 skb_push(head, head->data - skb_network_header(head)); 616 617 for (fp=head->next; fp; fp = fp->next) { 618 head->data_len += fp->len; 619 head->len += fp->len; 620 if (head->ip_summed != fp->ip_summed) 621 head->ip_summed = CHECKSUM_NONE; 622 else if (head->ip_summed == CHECKSUM_COMPLETE) 623 head->csum = csum_add(head->csum, fp->csum); 624 head->truesize += fp->truesize; 625 } 626 atomic_sub(head->truesize, &qp->q.net->mem); 627 628 head->next = NULL; 629 head->dev = dev; 630 head->tstamp = qp->q.stamp; 631 632 iph = ip_hdr(head); 633 iph->frag_off = 0; 634 iph->tot_len = htons(len); 635 iph->tos |= ecn; 636 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS); 637 qp->q.fragments = NULL; 638 qp->q.fragments_tail = NULL; 639 return 0; 640 641 out_nomem: 642 LIMIT_NETDEBUG(KERN_ERR pr_fmt("queue_glue: no memory for gluing queue %p\n"), 643 qp); 644 err = -ENOMEM; 645 goto out_fail; 646 out_oversize: 647 if (net_ratelimit()) 648 pr_info("Oversized IP packet from %pI4\n", &qp->saddr); 649 out_fail: 650 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); 651 return err; 652 } 653 654 /* Process an incoming IP datagram fragment. */ 655 int ip_defrag(struct sk_buff *skb, u32 user) 656 { 657 struct ipq *qp; 658 struct net *net; 659 660 net = skb->dev ? dev_net(skb->dev) : dev_net(skb_dst(skb)->dev); 661 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS); 662 663 /* Start by cleaning up the memory. */ 664 if (atomic_read(&net->ipv4.frags.mem) > net->ipv4.frags.high_thresh) 665 ip_evictor(net); 666 667 /* Lookup (or create) queue header */ 668 if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) { 669 int ret; 670 671 spin_lock(&qp->q.lock); 672 673 ret = ip_frag_queue(qp, skb); 674 675 spin_unlock(&qp->q.lock); 676 ipq_put(qp); 677 return ret; 678 } 679 680 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); 681 kfree_skb(skb); 682 return -ENOMEM; 683 } 684 EXPORT_SYMBOL(ip_defrag); 685 686 struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user) 687 { 688 const struct iphdr *iph; 689 u32 len; 690 691 if (skb->protocol != htons(ETH_P_IP)) 692 return skb; 693 694 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 695 return skb; 696 697 iph = ip_hdr(skb); 698 if (iph->ihl < 5 || iph->version != 4) 699 return skb; 700 if (!pskb_may_pull(skb, iph->ihl*4)) 701 return skb; 702 iph = ip_hdr(skb); 703 len = ntohs(iph->tot_len); 704 if (skb->len < len || len < (iph->ihl * 4)) 705 return skb; 706 707 if (ip_is_fragment(ip_hdr(skb))) { 708 skb = skb_share_check(skb, GFP_ATOMIC); 709 if (skb) { 710 if (pskb_trim_rcsum(skb, len)) 711 return skb; 712 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 713 if (ip_defrag(skb, user)) 714 return NULL; 715 skb->rxhash = 0; 716 } 717 } 718 return skb; 719 } 720 EXPORT_SYMBOL(ip_check_defrag); 721 722 #ifdef CONFIG_SYSCTL 723 static int zero; 724 725 static struct ctl_table ip4_frags_ns_ctl_table[] = { 726 { 727 .procname = "ipfrag_high_thresh", 728 .data = &init_net.ipv4.frags.high_thresh, 729 .maxlen = sizeof(int), 730 .mode = 0644, 731 .proc_handler = proc_dointvec 732 }, 733 { 734 .procname = "ipfrag_low_thresh", 735 .data = &init_net.ipv4.frags.low_thresh, 736 .maxlen = sizeof(int), 737 .mode = 0644, 738 .proc_handler = proc_dointvec 739 }, 740 { 741 .procname = "ipfrag_time", 742 .data = &init_net.ipv4.frags.timeout, 743 .maxlen = sizeof(int), 744 .mode = 0644, 745 .proc_handler = proc_dointvec_jiffies, 746 }, 747 { } 748 }; 749 750 static struct ctl_table ip4_frags_ctl_table[] = { 751 { 752 .procname = "ipfrag_secret_interval", 753 .data = &ip4_frags.secret_interval, 754 .maxlen = sizeof(int), 755 .mode = 0644, 756 .proc_handler = proc_dointvec_jiffies, 757 }, 758 { 759 .procname = "ipfrag_max_dist", 760 .data = &sysctl_ipfrag_max_dist, 761 .maxlen = sizeof(int), 762 .mode = 0644, 763 .proc_handler = proc_dointvec_minmax, 764 .extra1 = &zero 765 }, 766 { } 767 }; 768 769 static int __net_init ip4_frags_ns_ctl_register(struct net *net) 770 { 771 struct ctl_table *table; 772 struct ctl_table_header *hdr; 773 774 table = ip4_frags_ns_ctl_table; 775 if (!net_eq(net, &init_net)) { 776 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL); 777 if (table == NULL) 778 goto err_alloc; 779 780 table[0].data = &net->ipv4.frags.high_thresh; 781 table[1].data = &net->ipv4.frags.low_thresh; 782 table[2].data = &net->ipv4.frags.timeout; 783 } 784 785 hdr = register_net_sysctl_table(net, net_ipv4_ctl_path, table); 786 if (hdr == NULL) 787 goto err_reg; 788 789 net->ipv4.frags_hdr = hdr; 790 return 0; 791 792 err_reg: 793 if (!net_eq(net, &init_net)) 794 kfree(table); 795 err_alloc: 796 return -ENOMEM; 797 } 798 799 static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net) 800 { 801 struct ctl_table *table; 802 803 table = net->ipv4.frags_hdr->ctl_table_arg; 804 unregister_net_sysctl_table(net->ipv4.frags_hdr); 805 kfree(table); 806 } 807 808 static void ip4_frags_ctl_register(void) 809 { 810 register_net_sysctl_rotable(net_ipv4_ctl_path, ip4_frags_ctl_table); 811 } 812 #else 813 static inline int ip4_frags_ns_ctl_register(struct net *net) 814 { 815 return 0; 816 } 817 818 static inline void ip4_frags_ns_ctl_unregister(struct net *net) 819 { 820 } 821 822 static inline void ip4_frags_ctl_register(void) 823 { 824 } 825 #endif 826 827 static int __net_init ipv4_frags_init_net(struct net *net) 828 { 829 /* 830 * Fragment cache limits. We will commit 256K at one time. Should we 831 * cross that limit we will prune down to 192K. This should cope with 832 * even the most extreme cases without allowing an attacker to 833 * measurably harm machine performance. 834 */ 835 net->ipv4.frags.high_thresh = 256 * 1024; 836 net->ipv4.frags.low_thresh = 192 * 1024; 837 /* 838 * Important NOTE! Fragment queue must be destroyed before MSL expires. 839 * RFC791 is wrong proposing to prolongate timer each fragment arrival 840 * by TTL. 841 */ 842 net->ipv4.frags.timeout = IP_FRAG_TIME; 843 844 inet_frags_init_net(&net->ipv4.frags); 845 846 return ip4_frags_ns_ctl_register(net); 847 } 848 849 static void __net_exit ipv4_frags_exit_net(struct net *net) 850 { 851 ip4_frags_ns_ctl_unregister(net); 852 inet_frags_exit_net(&net->ipv4.frags, &ip4_frags); 853 } 854 855 static struct pernet_operations ip4_frags_ops = { 856 .init = ipv4_frags_init_net, 857 .exit = ipv4_frags_exit_net, 858 }; 859 860 void __init ipfrag_init(void) 861 { 862 ip4_frags_ctl_register(); 863 register_pernet_subsys(&ip4_frags_ops); 864 ip4_frags.hashfn = ip4_hashfn; 865 ip4_frags.constructor = ip4_frag_init; 866 ip4_frags.destructor = ip4_frag_free; 867 ip4_frags.skb_free = NULL; 868 ip4_frags.qsize = sizeof(struct ipq); 869 ip4_frags.match = ip4_frag_match; 870 ip4_frags.frag_expire = ip_expire; 871 ip4_frags.secret_interval = 10 * 60 * HZ; 872 inet_frags_init(&ip4_frags); 873 } 874