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 sum_frag_mem_limit(&net->ipv4.frags); 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 bool 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 static void ip4_frag_init(struct inet_frag_queue *q, void *a) 165 { 166 struct ipq *qp = container_of(q, struct ipq, q); 167 struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4, 168 frags); 169 struct net *net = container_of(ipv4, struct net, ipv4); 170 171 struct ip4_create_arg *arg = a; 172 173 qp->protocol = arg->iph->protocol; 174 qp->id = arg->iph->id; 175 qp->ecn = ip4_frag_ecn(arg->iph->tos); 176 qp->saddr = arg->iph->saddr; 177 qp->daddr = arg->iph->daddr; 178 qp->user = arg->user; 179 qp->peer = sysctl_ipfrag_max_dist ? 180 inet_getpeer_v4(net->ipv4.peers, arg->iph->saddr, 1) : NULL; 181 } 182 183 static __inline__ void ip4_frag_free(struct inet_frag_queue *q) 184 { 185 struct ipq *qp; 186 187 qp = container_of(q, struct ipq, q); 188 if (qp->peer) 189 inet_putpeer(qp->peer); 190 } 191 192 193 /* Destruction primitives. */ 194 195 static __inline__ void ipq_put(struct ipq *ipq) 196 { 197 inet_frag_put(&ipq->q, &ip4_frags); 198 } 199 200 /* Kill ipq entry. It is not destroyed immediately, 201 * because caller (and someone more) holds reference count. 202 */ 203 static void ipq_kill(struct ipq *ipq) 204 { 205 inet_frag_kill(&ipq->q, &ip4_frags); 206 } 207 208 /* Memory limiting on fragments. Evictor trashes the oldest 209 * fragment queue until we are back under the threshold. 210 */ 211 static void ip_evictor(struct net *net) 212 { 213 int evicted; 214 215 evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags, false); 216 if (evicted) 217 IP_ADD_STATS_BH(net, IPSTATS_MIB_REASMFAILS, evicted); 218 } 219 220 /* 221 * Oops, a fragment queue timed out. Kill it and send an ICMP reply. 222 */ 223 static void ip_expire(unsigned long arg) 224 { 225 struct ipq *qp; 226 struct net *net; 227 228 qp = container_of((struct inet_frag_queue *) arg, struct ipq, q); 229 net = container_of(qp->q.net, struct net, ipv4.frags); 230 231 spin_lock(&qp->q.lock); 232 233 if (qp->q.last_in & INET_FRAG_COMPLETE) 234 goto out; 235 236 ipq_kill(qp); 237 238 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT); 239 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); 240 241 if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) { 242 struct sk_buff *head = qp->q.fragments; 243 const struct iphdr *iph; 244 int err; 245 246 rcu_read_lock(); 247 head->dev = dev_get_by_index_rcu(net, qp->iif); 248 if (!head->dev) 249 goto out_rcu_unlock; 250 251 /* skb dst is stale, drop it, and perform route lookup again */ 252 skb_dst_drop(head); 253 iph = ip_hdr(head); 254 err = ip_route_input_noref(head, iph->daddr, iph->saddr, 255 iph->tos, head->dev); 256 if (err) 257 goto out_rcu_unlock; 258 259 /* 260 * Only an end host needs to send an ICMP 261 * "Fragment Reassembly Timeout" message, per RFC792. 262 */ 263 if (qp->user == IP_DEFRAG_AF_PACKET || 264 (qp->user == IP_DEFRAG_CONNTRACK_IN && 265 skb_rtable(head)->rt_type != RTN_LOCAL)) 266 goto out_rcu_unlock; 267 268 269 /* Send an ICMP "Fragment Reassembly Timeout" message. */ 270 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); 271 out_rcu_unlock: 272 rcu_read_unlock(); 273 } 274 out: 275 spin_unlock(&qp->q.lock); 276 ipq_put(qp); 277 } 278 279 /* Find the correct entry in the "incomplete datagrams" queue for 280 * this IP datagram, and create new one, if nothing is found. 281 */ 282 static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user) 283 { 284 struct inet_frag_queue *q; 285 struct ip4_create_arg arg; 286 unsigned int hash; 287 288 arg.iph = iph; 289 arg.user = user; 290 291 read_lock(&ip4_frags.lock); 292 hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol); 293 294 q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash); 295 if (IS_ERR_OR_NULL(q)) { 296 inet_frag_maybe_warn_overflow(q, pr_fmt()); 297 return NULL; 298 } 299 return container_of(q, struct ipq, q); 300 } 301 302 /* Is the fragment too far ahead to be part of ipq? */ 303 static inline int ip_frag_too_far(struct ipq *qp) 304 { 305 struct inet_peer *peer = qp->peer; 306 unsigned int max = sysctl_ipfrag_max_dist; 307 unsigned int start, end; 308 309 int rc; 310 311 if (!peer || !max) 312 return 0; 313 314 start = qp->rid; 315 end = atomic_inc_return(&peer->rid); 316 qp->rid = end; 317 318 rc = qp->q.fragments && (end - start) > max; 319 320 if (rc) { 321 struct net *net; 322 323 net = container_of(qp->q.net, struct net, ipv4.frags); 324 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); 325 } 326 327 return rc; 328 } 329 330 static int ip_frag_reinit(struct ipq *qp) 331 { 332 struct sk_buff *fp; 333 unsigned int sum_truesize = 0; 334 335 if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) { 336 atomic_inc(&qp->q.refcnt); 337 return -ETIMEDOUT; 338 } 339 340 fp = qp->q.fragments; 341 do { 342 struct sk_buff *xp = fp->next; 343 344 sum_truesize += fp->truesize; 345 kfree_skb(fp); 346 fp = xp; 347 } while (fp); 348 sub_frag_mem_limit(&qp->q, sum_truesize); 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 corrupted. 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 sub_frag_mem_limit(&qp->q, free_it->truesize); 494 kfree_skb(free_it); 495 } 496 } 497 498 FRAG_CB(skb)->offset = offset; 499 500 /* Insert this fragment in the chain of fragments. */ 501 skb->next = next; 502 if (!next) 503 qp->q.fragments_tail = skb; 504 if (prev) 505 prev->next = skb; 506 else 507 qp->q.fragments = skb; 508 509 dev = skb->dev; 510 if (dev) { 511 qp->iif = dev->ifindex; 512 skb->dev = NULL; 513 } 514 qp->q.stamp = skb->tstamp; 515 qp->q.meat += skb->len; 516 qp->ecn |= ecn; 517 add_frag_mem_limit(&qp->q, skb->truesize); 518 if (offset == 0) 519 qp->q.last_in |= INET_FRAG_FIRST_IN; 520 521 if (ip_hdr(skb)->frag_off & htons(IP_DF) && 522 skb->len + ihl > qp->q.max_size) 523 qp->q.max_size = skb->len + ihl; 524 525 if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && 526 qp->q.meat == qp->q.len) 527 return ip_frag_reasm(qp, prev, dev); 528 529 inet_frag_lru_move(&qp->q); 530 return -EINPROGRESS; 531 532 err: 533 kfree_skb(skb); 534 return err; 535 } 536 537 538 /* Build a new IP datagram from all its fragments. */ 539 540 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, 541 struct net_device *dev) 542 { 543 struct net *net = container_of(qp->q.net, struct net, ipv4.frags); 544 struct iphdr *iph; 545 struct sk_buff *fp, *head = qp->q.fragments; 546 int len; 547 int ihlen; 548 int err; 549 int sum_truesize; 550 u8 ecn; 551 552 ipq_kill(qp); 553 554 ecn = ip4_frag_ecn_table[qp->ecn]; 555 if (unlikely(ecn == 0xff)) { 556 err = -EINVAL; 557 goto out_fail; 558 } 559 /* Make the one we just received the head. */ 560 if (prev) { 561 head = prev->next; 562 fp = skb_clone(head, GFP_ATOMIC); 563 if (!fp) 564 goto out_nomem; 565 566 fp->next = head->next; 567 if (!fp->next) 568 qp->q.fragments_tail = fp; 569 prev->next = fp; 570 571 skb_morph(head, qp->q.fragments); 572 head->next = qp->q.fragments->next; 573 574 consume_skb(qp->q.fragments); 575 qp->q.fragments = head; 576 } 577 578 WARN_ON(head == NULL); 579 WARN_ON(FRAG_CB(head)->offset != 0); 580 581 /* Allocate a new buffer for the datagram. */ 582 ihlen = ip_hdrlen(head); 583 len = ihlen + qp->q.len; 584 585 err = -E2BIG; 586 if (len > 65535) 587 goto out_oversize; 588 589 /* Head of list must not be cloned. */ 590 if (skb_unclone(head, GFP_ATOMIC)) 591 goto out_nomem; 592 593 /* If the first fragment is fragmented itself, we split 594 * it to two chunks: the first with data and paged part 595 * and the second, holding only fragments. */ 596 if (skb_has_frag_list(head)) { 597 struct sk_buff *clone; 598 int i, plen = 0; 599 600 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL) 601 goto out_nomem; 602 clone->next = head->next; 603 head->next = clone; 604 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list; 605 skb_frag_list_init(head); 606 for (i = 0; i < skb_shinfo(head)->nr_frags; i++) 607 plen += skb_frag_size(&skb_shinfo(head)->frags[i]); 608 clone->len = clone->data_len = head->data_len - plen; 609 head->data_len -= clone->len; 610 head->len -= clone->len; 611 clone->csum = 0; 612 clone->ip_summed = head->ip_summed; 613 add_frag_mem_limit(&qp->q, clone->truesize); 614 } 615 616 skb_push(head, head->data - skb_network_header(head)); 617 618 sum_truesize = head->truesize; 619 for (fp = head->next; fp;) { 620 bool headstolen; 621 int delta; 622 struct sk_buff *next = fp->next; 623 624 sum_truesize += fp->truesize; 625 if (head->ip_summed != fp->ip_summed) 626 head->ip_summed = CHECKSUM_NONE; 627 else if (head->ip_summed == CHECKSUM_COMPLETE) 628 head->csum = csum_add(head->csum, fp->csum); 629 630 if (skb_try_coalesce(head, fp, &headstolen, &delta)) { 631 kfree_skb_partial(fp, headstolen); 632 } else { 633 if (!skb_shinfo(head)->frag_list) 634 skb_shinfo(head)->frag_list = fp; 635 head->data_len += fp->len; 636 head->len += fp->len; 637 head->truesize += fp->truesize; 638 } 639 fp = next; 640 } 641 sub_frag_mem_limit(&qp->q, sum_truesize); 642 643 head->next = NULL; 644 head->dev = dev; 645 head->tstamp = qp->q.stamp; 646 IPCB(head)->frag_max_size = qp->q.max_size; 647 648 iph = ip_hdr(head); 649 /* max_size != 0 implies at least one fragment had IP_DF set */ 650 iph->frag_off = qp->q.max_size ? htons(IP_DF) : 0; 651 iph->tot_len = htons(len); 652 iph->tos |= ecn; 653 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS); 654 qp->q.fragments = NULL; 655 qp->q.fragments_tail = NULL; 656 return 0; 657 658 out_nomem: 659 LIMIT_NETDEBUG(KERN_ERR pr_fmt("queue_glue: no memory for gluing queue %p\n"), 660 qp); 661 err = -ENOMEM; 662 goto out_fail; 663 out_oversize: 664 net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->saddr); 665 out_fail: 666 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); 667 return err; 668 } 669 670 /* Process an incoming IP datagram fragment. */ 671 int ip_defrag(struct sk_buff *skb, u32 user) 672 { 673 struct ipq *qp; 674 struct net *net; 675 676 net = skb->dev ? dev_net(skb->dev) : dev_net(skb_dst(skb)->dev); 677 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS); 678 679 /* Start by cleaning up the memory. */ 680 ip_evictor(net); 681 682 /* Lookup (or create) queue header */ 683 if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) { 684 int ret; 685 686 spin_lock(&qp->q.lock); 687 688 ret = ip_frag_queue(qp, skb); 689 690 spin_unlock(&qp->q.lock); 691 ipq_put(qp); 692 return ret; 693 } 694 695 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); 696 kfree_skb(skb); 697 return -ENOMEM; 698 } 699 EXPORT_SYMBOL(ip_defrag); 700 701 struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user) 702 { 703 struct iphdr iph; 704 u32 len; 705 706 if (skb->protocol != htons(ETH_P_IP)) 707 return skb; 708 709 if (!skb_copy_bits(skb, 0, &iph, sizeof(iph))) 710 return skb; 711 712 if (iph.ihl < 5 || iph.version != 4) 713 return skb; 714 715 len = ntohs(iph.tot_len); 716 if (skb->len < len || len < (iph.ihl * 4)) 717 return skb; 718 719 if (ip_is_fragment(&iph)) { 720 skb = skb_share_check(skb, GFP_ATOMIC); 721 if (skb) { 722 if (!pskb_may_pull(skb, iph.ihl*4)) 723 return skb; 724 if (pskb_trim_rcsum(skb, len)) 725 return skb; 726 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 727 if (ip_defrag(skb, user)) 728 return NULL; 729 skb->rxhash = 0; 730 } 731 } 732 return skb; 733 } 734 EXPORT_SYMBOL(ip_check_defrag); 735 736 #ifdef CONFIG_SYSCTL 737 static int zero; 738 739 static struct ctl_table ip4_frags_ns_ctl_table[] = { 740 { 741 .procname = "ipfrag_high_thresh", 742 .data = &init_net.ipv4.frags.high_thresh, 743 .maxlen = sizeof(int), 744 .mode = 0644, 745 .proc_handler = proc_dointvec 746 }, 747 { 748 .procname = "ipfrag_low_thresh", 749 .data = &init_net.ipv4.frags.low_thresh, 750 .maxlen = sizeof(int), 751 .mode = 0644, 752 .proc_handler = proc_dointvec 753 }, 754 { 755 .procname = "ipfrag_time", 756 .data = &init_net.ipv4.frags.timeout, 757 .maxlen = sizeof(int), 758 .mode = 0644, 759 .proc_handler = proc_dointvec_jiffies, 760 }, 761 { } 762 }; 763 764 static struct ctl_table ip4_frags_ctl_table[] = { 765 { 766 .procname = "ipfrag_secret_interval", 767 .data = &ip4_frags.secret_interval, 768 .maxlen = sizeof(int), 769 .mode = 0644, 770 .proc_handler = proc_dointvec_jiffies, 771 }, 772 { 773 .procname = "ipfrag_max_dist", 774 .data = &sysctl_ipfrag_max_dist, 775 .maxlen = sizeof(int), 776 .mode = 0644, 777 .proc_handler = proc_dointvec_minmax, 778 .extra1 = &zero 779 }, 780 { } 781 }; 782 783 static int __net_init ip4_frags_ns_ctl_register(struct net *net) 784 { 785 struct ctl_table *table; 786 struct ctl_table_header *hdr; 787 788 table = ip4_frags_ns_ctl_table; 789 if (!net_eq(net, &init_net)) { 790 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL); 791 if (table == NULL) 792 goto err_alloc; 793 794 table[0].data = &net->ipv4.frags.high_thresh; 795 table[1].data = &net->ipv4.frags.low_thresh; 796 table[2].data = &net->ipv4.frags.timeout; 797 798 /* Don't export sysctls to unprivileged users */ 799 if (net->user_ns != &init_user_ns) 800 table[0].procname = NULL; 801 } 802 803 hdr = register_net_sysctl(net, "net/ipv4", table); 804 if (hdr == NULL) 805 goto err_reg; 806 807 net->ipv4.frags_hdr = hdr; 808 return 0; 809 810 err_reg: 811 if (!net_eq(net, &init_net)) 812 kfree(table); 813 err_alloc: 814 return -ENOMEM; 815 } 816 817 static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net) 818 { 819 struct ctl_table *table; 820 821 table = net->ipv4.frags_hdr->ctl_table_arg; 822 unregister_net_sysctl_table(net->ipv4.frags_hdr); 823 kfree(table); 824 } 825 826 static void ip4_frags_ctl_register(void) 827 { 828 register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table); 829 } 830 #else 831 static inline int ip4_frags_ns_ctl_register(struct net *net) 832 { 833 return 0; 834 } 835 836 static inline void ip4_frags_ns_ctl_unregister(struct net *net) 837 { 838 } 839 840 static inline void ip4_frags_ctl_register(void) 841 { 842 } 843 #endif 844 845 static int __net_init ipv4_frags_init_net(struct net *net) 846 { 847 /* Fragment cache limits. 848 * 849 * The fragment memory accounting code, (tries to) account for 850 * the real memory usage, by measuring both the size of frag 851 * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue)) 852 * and the SKB's truesize. 853 * 854 * A 64K fragment consumes 129736 bytes (44*2944)+200 855 * (1500 truesize == 2944, sizeof(struct ipq) == 200) 856 * 857 * We will commit 4MB at one time. Should we cross that limit 858 * we will prune down to 3MB, making room for approx 8 big 64K 859 * fragments 8x128k. 860 */ 861 net->ipv4.frags.high_thresh = 4 * 1024 * 1024; 862 net->ipv4.frags.low_thresh = 3 * 1024 * 1024; 863 /* 864 * Important NOTE! Fragment queue must be destroyed before MSL expires. 865 * RFC791 is wrong proposing to prolongate timer each fragment arrival 866 * by TTL. 867 */ 868 net->ipv4.frags.timeout = IP_FRAG_TIME; 869 870 inet_frags_init_net(&net->ipv4.frags); 871 872 return ip4_frags_ns_ctl_register(net); 873 } 874 875 static void __net_exit ipv4_frags_exit_net(struct net *net) 876 { 877 ip4_frags_ns_ctl_unregister(net); 878 inet_frags_exit_net(&net->ipv4.frags, &ip4_frags); 879 } 880 881 static struct pernet_operations ip4_frags_ops = { 882 .init = ipv4_frags_init_net, 883 .exit = ipv4_frags_exit_net, 884 }; 885 886 void __init ipfrag_init(void) 887 { 888 ip4_frags_ctl_register(); 889 register_pernet_subsys(&ip4_frags_ops); 890 ip4_frags.hashfn = ip4_hashfn; 891 ip4_frags.constructor = ip4_frag_init; 892 ip4_frags.destructor = ip4_frag_free; 893 ip4_frags.skb_free = NULL; 894 ip4_frags.qsize = sizeof(struct ipq); 895 ip4_frags.match = ip4_frag_match; 896 ip4_frags.frag_expire = ip_expire; 897 ip4_frags.secret_interval = 10 * 60 * HZ; 898 inet_frags_init(&ip4_frags); 899 } 900