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