1/* 2 * IPv6 fragment reassembly for connection tracking 3 * 4 * Copyright (C)2004 USAGI/WIDE Project 5 * 6 * Author: 7 * Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp> 8 * 9 * Based on: net/ipv6/reassembly.c 10 * 11 * This program is free software; you can redistribute it and/or 12 * modify it under the terms of the GNU General Public License 13 * as published by the Free Software Foundation; either version 14 * 2 of the License, or (at your option) any later version. 15 */ 16 17#define pr_fmt(fmt) "IPv6-nf: " fmt 18 19#include <linux/errno.h> 20#include <linux/types.h> 21#include <linux/string.h> 22#include <linux/socket.h> 23#include <linux/sockios.h> 24#include <linux/jiffies.h> 25#include <linux/net.h> 26#include <linux/list.h> 27#include <linux/netdevice.h> 28#include <linux/in6.h> 29#include <linux/ipv6.h> 30#include <linux/icmpv6.h> 31#include <linux/random.h> 32#include <linux/slab.h> 33 34#include <net/sock.h> 35#include <net/snmp.h> 36#include <net/inet_frag.h> 37 38#include <net/ipv6.h> 39#include <net/protocol.h> 40#include <net/transp_v6.h> 41#include <net/rawv6.h> 42#include <net/ndisc.h> 43#include <net/addrconf.h> 44#include <net/inet_ecn.h> 45#include <net/netfilter/ipv6/nf_conntrack_ipv6.h> 46#include <linux/sysctl.h> 47#include <linux/netfilter.h> 48#include <linux/netfilter_ipv6.h> 49#include <linux/kernel.h> 50#include <linux/module.h> 51#include <net/netfilter/ipv6/nf_defrag_ipv6.h> 52 53static const char nf_frags_cache_name[] = "nf-frags"; 54 55struct nf_ct_frag6_skb_cb 56{ 57 struct inet6_skb_parm h; 58 int offset; 59 struct sk_buff *orig; 60}; 61 62#define NFCT_FRAG6_CB(skb) ((struct nf_ct_frag6_skb_cb*)((skb)->cb)) 63 64static struct inet_frags nf_frags; 65 66#ifdef CONFIG_SYSCTL 67static int zero; 68 69static struct ctl_table nf_ct_frag6_sysctl_table[] = { 70 { 71 .procname = "nf_conntrack_frag6_timeout", 72 .data = &init_net.nf_frag.frags.timeout, 73 .maxlen = sizeof(unsigned int), 74 .mode = 0644, 75 .proc_handler = proc_dointvec_jiffies, 76 }, 77 { 78 .procname = "nf_conntrack_frag6_low_thresh", 79 .data = &init_net.nf_frag.frags.low_thresh, 80 .maxlen = sizeof(unsigned int), 81 .mode = 0644, 82 .proc_handler = proc_dointvec_minmax, 83 .extra1 = &zero, 84 .extra2 = &init_net.nf_frag.frags.high_thresh 85 }, 86 { 87 .procname = "nf_conntrack_frag6_high_thresh", 88 .data = &init_net.nf_frag.frags.high_thresh, 89 .maxlen = sizeof(unsigned int), 90 .mode = 0644, 91 .proc_handler = proc_dointvec_minmax, 92 .extra1 = &init_net.nf_frag.frags.low_thresh 93 }, 94 { } 95}; 96 97static int nf_ct_frag6_sysctl_register(struct net *net) 98{ 99 struct ctl_table *table; 100 struct ctl_table_header *hdr; 101 102 table = nf_ct_frag6_sysctl_table; 103 if (!net_eq(net, &init_net)) { 104 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table), 105 GFP_KERNEL); 106 if (table == NULL) 107 goto err_alloc; 108 109 table[0].data = &net->nf_frag.frags.timeout; 110 table[1].data = &net->nf_frag.frags.low_thresh; 111 table[1].extra2 = &net->nf_frag.frags.high_thresh; 112 table[2].data = &net->nf_frag.frags.high_thresh; 113 table[2].extra1 = &net->nf_frag.frags.low_thresh; 114 table[2].extra2 = &init_net.nf_frag.frags.high_thresh; 115 } 116 117 hdr = register_net_sysctl(net, "net/netfilter", table); 118 if (hdr == NULL) 119 goto err_reg; 120 121 net->nf_frag.sysctl.frags_hdr = hdr; 122 return 0; 123 124err_reg: 125 if (!net_eq(net, &init_net)) 126 kfree(table); 127err_alloc: 128 return -ENOMEM; 129} 130 131static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net) 132{ 133 struct ctl_table *table; 134 135 table = net->nf_frag.sysctl.frags_hdr->ctl_table_arg; 136 unregister_net_sysctl_table(net->nf_frag.sysctl.frags_hdr); 137 if (!net_eq(net, &init_net)) 138 kfree(table); 139} 140 141#else 142static int nf_ct_frag6_sysctl_register(struct net *net) 143{ 144 return 0; 145} 146static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net) 147{ 148} 149#endif 150 151static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h) 152{ 153 return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK); 154} 155 156static unsigned int nf_hash_frag(__be32 id, const struct in6_addr *saddr, 157 const struct in6_addr *daddr) 158{ 159 net_get_random_once(&nf_frags.rnd, sizeof(nf_frags.rnd)); 160 return jhash_3words(ipv6_addr_hash(saddr), ipv6_addr_hash(daddr), 161 (__force u32)id, nf_frags.rnd); 162} 163 164 165static unsigned int nf_hashfn(const struct inet_frag_queue *q) 166{ 167 const struct frag_queue *nq; 168 169 nq = container_of(q, struct frag_queue, q); 170 return nf_hash_frag(nq->id, &nq->saddr, &nq->daddr); 171} 172 173static void nf_skb_free(struct sk_buff *skb) 174{ 175 if (NFCT_FRAG6_CB(skb)->orig) 176 kfree_skb(NFCT_FRAG6_CB(skb)->orig); 177} 178 179static void nf_ct_frag6_expire(unsigned long data) 180{ 181 struct frag_queue *fq; 182 struct net *net; 183 184 fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q); 185 net = container_of(fq->q.net, struct net, nf_frag.frags); 186 187 ip6_expire_frag_queue(net, fq, &nf_frags); 188} 189 190/* Creation primitives. */ 191static inline struct frag_queue *fq_find(struct net *net, __be32 id, 192 u32 user, struct in6_addr *src, 193 struct in6_addr *dst, u8 ecn) 194{ 195 struct inet_frag_queue *q; 196 struct ip6_create_arg arg; 197 unsigned int hash; 198 199 arg.id = id; 200 arg.user = user; 201 arg.src = src; 202 arg.dst = dst; 203 arg.ecn = ecn; 204 205 local_bh_disable(); 206 hash = nf_hash_frag(id, src, dst); 207 208 q = inet_frag_find(&net->nf_frag.frags, &nf_frags, &arg, hash); 209 local_bh_enable(); 210 if (IS_ERR_OR_NULL(q)) { 211 inet_frag_maybe_warn_overflow(q, pr_fmt()); 212 return NULL; 213 } 214 return container_of(q, struct frag_queue, q); 215} 216 217 218static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb, 219 const struct frag_hdr *fhdr, int nhoff) 220{ 221 struct sk_buff *prev, *next; 222 unsigned int payload_len; 223 int offset, end; 224 u8 ecn; 225 226 if (fq->q.flags & INET_FRAG_COMPLETE) { 227 pr_debug("Already completed\n"); 228 goto err; 229 } 230 231 payload_len = ntohs(ipv6_hdr(skb)->payload_len); 232 233 offset = ntohs(fhdr->frag_off) & ~0x7; 234 end = offset + (payload_len - 235 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1))); 236 237 if ((unsigned int)end > IPV6_MAXPLEN) { 238 pr_debug("offset is too large.\n"); 239 return -1; 240 } 241 242 ecn = ip6_frag_ecn(ipv6_hdr(skb)); 243 244 if (skb->ip_summed == CHECKSUM_COMPLETE) { 245 const unsigned char *nh = skb_network_header(skb); 246 skb->csum = csum_sub(skb->csum, 247 csum_partial(nh, (u8 *)(fhdr + 1) - nh, 248 0)); 249 } 250 251 /* Is this the final fragment? */ 252 if (!(fhdr->frag_off & htons(IP6_MF))) { 253 /* If we already have some bits beyond end 254 * or have different end, the segment is corrupted. 255 */ 256 if (end < fq->q.len || 257 ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) { 258 pr_debug("already received last fragment\n"); 259 goto err; 260 } 261 fq->q.flags |= INET_FRAG_LAST_IN; 262 fq->q.len = end; 263 } else { 264 /* Check if the fragment is rounded to 8 bytes. 265 * Required by the RFC. 266 */ 267 if (end & 0x7) { 268 /* RFC2460 says always send parameter problem in 269 * this case. -DaveM 270 */ 271 pr_debug("end of fragment not rounded to 8 bytes.\n"); 272 return -1; 273 } 274 if (end > fq->q.len) { 275 /* Some bits beyond end -> corruption. */ 276 if (fq->q.flags & INET_FRAG_LAST_IN) { 277 pr_debug("last packet already reached.\n"); 278 goto err; 279 } 280 fq->q.len = end; 281 } 282 } 283 284 if (end == offset) 285 goto err; 286 287 /* Point into the IP datagram 'data' part. */ 288 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) { 289 pr_debug("queue: message is too short.\n"); 290 goto err; 291 } 292 if (pskb_trim_rcsum(skb, end - offset)) { 293 pr_debug("Can't trim\n"); 294 goto err; 295 } 296 297 /* Find out which fragments are in front and at the back of us 298 * in the chain of fragments so far. We must know where to put 299 * this fragment, right? 300 */ 301 prev = fq->q.fragments_tail; 302 if (!prev || NFCT_FRAG6_CB(prev)->offset < offset) { 303 next = NULL; 304 goto found; 305 } 306 prev = NULL; 307 for (next = fq->q.fragments; next != NULL; next = next->next) { 308 if (NFCT_FRAG6_CB(next)->offset >= offset) 309 break; /* bingo! */ 310 prev = next; 311 } 312 313found: 314 /* RFC5722, Section 4: 315 * When reassembling an IPv6 datagram, if 316 * one or more its constituent fragments is determined to be an 317 * overlapping fragment, the entire datagram (and any constituent 318 * fragments, including those not yet received) MUST be silently 319 * discarded. 320 */ 321 322 /* Check for overlap with preceding fragment. */ 323 if (prev && 324 (NFCT_FRAG6_CB(prev)->offset + prev->len) > offset) 325 goto discard_fq; 326 327 /* Look for overlap with succeeding segment. */ 328 if (next && NFCT_FRAG6_CB(next)->offset < end) 329 goto discard_fq; 330 331 NFCT_FRAG6_CB(skb)->offset = offset; 332 333 /* Insert this fragment in the chain of fragments. */ 334 skb->next = next; 335 if (!next) 336 fq->q.fragments_tail = skb; 337 if (prev) 338 prev->next = skb; 339 else 340 fq->q.fragments = skb; 341 342 if (skb->dev) { 343 fq->iif = skb->dev->ifindex; 344 skb->dev = NULL; 345 } 346 fq->q.stamp = skb->tstamp; 347 fq->q.meat += skb->len; 348 fq->ecn |= ecn; 349 if (payload_len > fq->q.max_size) 350 fq->q.max_size = payload_len; 351 add_frag_mem_limit(&fq->q, skb->truesize); 352 353 /* The first fragment. 354 * nhoffset is obtained from the first fragment, of course. 355 */ 356 if (offset == 0) { 357 fq->nhoffset = nhoff; 358 fq->q.flags |= INET_FRAG_FIRST_IN; 359 } 360 361 return 0; 362 363discard_fq: 364 inet_frag_kill(&fq->q, &nf_frags); 365err: 366 return -1; 367} 368 369/* 370 * Check if this packet is complete. 371 * Returns NULL on failure by any reason, and pointer 372 * to current nexthdr field in reassembled frame. 373 * 374 * It is called with locked fq, and caller must check that 375 * queue is eligible for reassembly i.e. it is not COMPLETE, 376 * the last and the first frames arrived and all the bits are here. 377 */ 378static struct sk_buff * 379nf_ct_frag6_reasm(struct frag_queue *fq, struct net_device *dev) 380{ 381 struct sk_buff *fp, *op, *head = fq->q.fragments; 382 int payload_len; 383 u8 ecn; 384 385 inet_frag_kill(&fq->q, &nf_frags); 386 387 WARN_ON(head == NULL); 388 WARN_ON(NFCT_FRAG6_CB(head)->offset != 0); 389 390 ecn = ip_frag_ecn_table[fq->ecn]; 391 if (unlikely(ecn == 0xff)) 392 goto out_fail; 393 394 /* Unfragmented part is taken from the first segment. */ 395 payload_len = ((head->data - skb_network_header(head)) - 396 sizeof(struct ipv6hdr) + fq->q.len - 397 sizeof(struct frag_hdr)); 398 if (payload_len > IPV6_MAXPLEN) { 399 pr_debug("payload len is too large.\n"); 400 goto out_oversize; 401 } 402 403 /* Head of list must not be cloned. */ 404 if (skb_unclone(head, GFP_ATOMIC)) { 405 pr_debug("skb is cloned but can't expand head"); 406 goto out_oom; 407 } 408 409 /* If the first fragment is fragmented itself, we split 410 * it to two chunks: the first with data and paged part 411 * and the second, holding only fragments. */ 412 if (skb_has_frag_list(head)) { 413 struct sk_buff *clone; 414 int i, plen = 0; 415 416 clone = alloc_skb(0, GFP_ATOMIC); 417 if (clone == NULL) 418 goto out_oom; 419 420 clone->next = head->next; 421 head->next = clone; 422 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list; 423 skb_frag_list_init(head); 424 for (i = 0; i < skb_shinfo(head)->nr_frags; i++) 425 plen += skb_frag_size(&skb_shinfo(head)->frags[i]); 426 clone->len = clone->data_len = head->data_len - plen; 427 head->data_len -= clone->len; 428 head->len -= clone->len; 429 clone->csum = 0; 430 clone->ip_summed = head->ip_summed; 431 432 NFCT_FRAG6_CB(clone)->orig = NULL; 433 add_frag_mem_limit(&fq->q, clone->truesize); 434 } 435 436 /* We have to remove fragment header from datagram and to relocate 437 * header in order to calculate ICV correctly. */ 438 skb_network_header(head)[fq->nhoffset] = skb_transport_header(head)[0]; 439 memmove(head->head + sizeof(struct frag_hdr), head->head, 440 (head->data - head->head) - sizeof(struct frag_hdr)); 441 head->mac_header += sizeof(struct frag_hdr); 442 head->network_header += sizeof(struct frag_hdr); 443 444 skb_shinfo(head)->frag_list = head->next; 445 skb_reset_transport_header(head); 446 skb_push(head, head->data - skb_network_header(head)); 447 448 for (fp=head->next; fp; fp = fp->next) { 449 head->data_len += fp->len; 450 head->len += fp->len; 451 if (head->ip_summed != fp->ip_summed) 452 head->ip_summed = CHECKSUM_NONE; 453 else if (head->ip_summed == CHECKSUM_COMPLETE) 454 head->csum = csum_add(head->csum, fp->csum); 455 head->truesize += fp->truesize; 456 } 457 sub_frag_mem_limit(&fq->q, head->truesize); 458 459 head->ignore_df = 1; 460 head->next = NULL; 461 head->dev = dev; 462 head->tstamp = fq->q.stamp; 463 ipv6_hdr(head)->payload_len = htons(payload_len); 464 ipv6_change_dsfield(ipv6_hdr(head), 0xff, ecn); 465 IP6CB(head)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size; 466 467 /* Yes, and fold redundant checksum back. 8) */ 468 if (head->ip_summed == CHECKSUM_COMPLETE) 469 head->csum = csum_partial(skb_network_header(head), 470 skb_network_header_len(head), 471 head->csum); 472 473 fq->q.fragments = NULL; 474 fq->q.fragments_tail = NULL; 475 476 /* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */ 477 fp = skb_shinfo(head)->frag_list; 478 if (fp && NFCT_FRAG6_CB(fp)->orig == NULL) 479 /* at above code, head skb is divided into two skbs. */ 480 fp = fp->next; 481 482 op = NFCT_FRAG6_CB(head)->orig; 483 for (; fp; fp = fp->next) { 484 struct sk_buff *orig = NFCT_FRAG6_CB(fp)->orig; 485 486 op->next = orig; 487 op = orig; 488 NFCT_FRAG6_CB(fp)->orig = NULL; 489 } 490 491 return head; 492 493out_oversize: 494 net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n", 495 payload_len); 496 goto out_fail; 497out_oom: 498 net_dbg_ratelimited("nf_ct_frag6_reasm: no memory for reassembly\n"); 499out_fail: 500 return NULL; 501} 502 503/* 504 * find the header just before Fragment Header. 505 * 506 * if success return 0 and set ... 507 * (*prevhdrp): the value of "Next Header Field" in the header 508 * just before Fragment Header. 509 * (*prevhoff): the offset of "Next Header Field" in the header 510 * just before Fragment Header. 511 * (*fhoff) : the offset of Fragment Header. 512 * 513 * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c 514 * 515 */ 516static int 517find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff) 518{ 519 u8 nexthdr = ipv6_hdr(skb)->nexthdr; 520 const int netoff = skb_network_offset(skb); 521 u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr); 522 int start = netoff + sizeof(struct ipv6hdr); 523 int len = skb->len - start; 524 u8 prevhdr = NEXTHDR_IPV6; 525 526 while (nexthdr != NEXTHDR_FRAGMENT) { 527 struct ipv6_opt_hdr hdr; 528 int hdrlen; 529 530 if (!ipv6_ext_hdr(nexthdr)) { 531 return -1; 532 } 533 if (nexthdr == NEXTHDR_NONE) { 534 pr_debug("next header is none\n"); 535 return -1; 536 } 537 if (len < (int)sizeof(struct ipv6_opt_hdr)) { 538 pr_debug("too short\n"); 539 return -1; 540 } 541 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr))) 542 BUG(); 543 if (nexthdr == NEXTHDR_AUTH) 544 hdrlen = (hdr.hdrlen+2)<<2; 545 else 546 hdrlen = ipv6_optlen(&hdr); 547 548 prevhdr = nexthdr; 549 prev_nhoff = start; 550 551 nexthdr = hdr.nexthdr; 552 len -= hdrlen; 553 start += hdrlen; 554 } 555 556 if (len < 0) 557 return -1; 558 559 *prevhdrp = prevhdr; 560 *prevhoff = prev_nhoff; 561 *fhoff = start; 562 563 return 0; 564} 565 566struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb, u32 user) 567{ 568 struct sk_buff *clone; 569 struct net_device *dev = skb->dev; 570 struct net *net = skb_dst(skb) ? dev_net(skb_dst(skb)->dev) 571 : dev_net(skb->dev); 572 struct frag_hdr *fhdr; 573 struct frag_queue *fq; 574 struct ipv6hdr *hdr; 575 int fhoff, nhoff; 576 u8 prevhdr; 577 struct sk_buff *ret_skb = NULL; 578 579 /* Jumbo payload inhibits frag. header */ 580 if (ipv6_hdr(skb)->payload_len == 0) { 581 pr_debug("payload len = 0\n"); 582 return skb; 583 } 584 585 if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0) 586 return skb; 587 588 clone = skb_clone(skb, GFP_ATOMIC); 589 if (clone == NULL) { 590 pr_debug("Can't clone skb\n"); 591 return skb; 592 } 593 594 NFCT_FRAG6_CB(clone)->orig = skb; 595 596 if (!pskb_may_pull(clone, fhoff + sizeof(*fhdr))) { 597 pr_debug("message is too short.\n"); 598 goto ret_orig; 599 } 600 601 skb_set_transport_header(clone, fhoff); 602 hdr = ipv6_hdr(clone); 603 fhdr = (struct frag_hdr *)skb_transport_header(clone); 604 605 fq = fq_find(net, fhdr->identification, user, &hdr->saddr, &hdr->daddr, 606 ip6_frag_ecn(hdr)); 607 if (fq == NULL) { 608 pr_debug("Can't find and can't create new queue\n"); 609 goto ret_orig; 610 } 611 612 spin_lock_bh(&fq->q.lock); 613 614 if (nf_ct_frag6_queue(fq, clone, fhdr, nhoff) < 0) { 615 spin_unlock_bh(&fq->q.lock); 616 pr_debug("Can't insert skb to queue\n"); 617 inet_frag_put(&fq->q, &nf_frags); 618 goto ret_orig; 619 } 620 621 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && 622 fq->q.meat == fq->q.len) { 623 ret_skb = nf_ct_frag6_reasm(fq, dev); 624 if (ret_skb == NULL) 625 pr_debug("Can't reassemble fragmented packets\n"); 626 } 627 spin_unlock_bh(&fq->q.lock); 628 629 inet_frag_put(&fq->q, &nf_frags); 630 return ret_skb; 631 632ret_orig: 633 kfree_skb(clone); 634 return skb; 635} 636 637void nf_ct_frag6_consume_orig(struct sk_buff *skb) 638{ 639 struct sk_buff *s, *s2; 640 641 for (s = NFCT_FRAG6_CB(skb)->orig; s;) { 642 s2 = s->next; 643 s->next = NULL; 644 consume_skb(s); 645 s = s2; 646 } 647} 648 649static int nf_ct_net_init(struct net *net) 650{ 651 net->nf_frag.frags.high_thresh = IPV6_FRAG_HIGH_THRESH; 652 net->nf_frag.frags.low_thresh = IPV6_FRAG_LOW_THRESH; 653 net->nf_frag.frags.timeout = IPV6_FRAG_TIMEOUT; 654 inet_frags_init_net(&net->nf_frag.frags); 655 656 return nf_ct_frag6_sysctl_register(net); 657} 658 659static void nf_ct_net_exit(struct net *net) 660{ 661 nf_ct_frags6_sysctl_unregister(net); 662 inet_frags_exit_net(&net->nf_frag.frags, &nf_frags); 663} 664 665static struct pernet_operations nf_ct_net_ops = { 666 .init = nf_ct_net_init, 667 .exit = nf_ct_net_exit, 668}; 669 670int nf_ct_frag6_init(void) 671{ 672 int ret = 0; 673 674 nf_frags.hashfn = nf_hashfn; 675 nf_frags.constructor = ip6_frag_init; 676 nf_frags.destructor = NULL; 677 nf_frags.skb_free = nf_skb_free; 678 nf_frags.qsize = sizeof(struct frag_queue); 679 nf_frags.match = ip6_frag_match; 680 nf_frags.frag_expire = nf_ct_frag6_expire; 681 nf_frags.frags_cache_name = nf_frags_cache_name; 682 ret = inet_frags_init(&nf_frags); 683 if (ret) 684 goto out; 685 ret = register_pernet_subsys(&nf_ct_net_ops); 686 if (ret) 687 inet_frags_fini(&nf_frags); 688 689out: 690 return ret; 691} 692 693void nf_ct_frag6_cleanup(void) 694{ 695 unregister_pernet_subsys(&nf_ct_net_ops); 696 inet_frags_fini(&nf_frags); 697} 698