1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * IPv6 fragment reassembly for connection tracking 4 * 5 * Copyright (C)2004 USAGI/WIDE Project 6 * 7 * Author: 8 * Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp> 9 * 10 * Based on: net/ipv6/reassembly.c 11 */ 12 13 #define pr_fmt(fmt) "IPv6-nf: " fmt 14 15 #include <linux/errno.h> 16 #include <linux/types.h> 17 #include <linux/string.h> 18 #include <linux/net.h> 19 #include <linux/netdevice.h> 20 #include <linux/ipv6.h> 21 #include <linux/slab.h> 22 23 #include <net/ipv6_frag.h> 24 25 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h> 26 #include <linux/sysctl.h> 27 #include <linux/netfilter.h> 28 #include <linux/netfilter_ipv6.h> 29 #include <linux/kernel.h> 30 #include <linux/module.h> 31 #include <net/netfilter/ipv6/nf_defrag_ipv6.h> 32 #include <net/netns/generic.h> 33 34 static const char nf_frags_cache_name[] = "nf-frags"; 35 36 static unsigned int nf_frag_pernet_id __read_mostly; 37 static struct inet_frags nf_frags; 38 39 static struct nft_ct_frag6_pernet *nf_frag_pernet(struct net *net) 40 { 41 return net_generic(net, nf_frag_pernet_id); 42 } 43 44 #ifdef CONFIG_SYSCTL 45 46 static struct ctl_table nf_ct_frag6_sysctl_table[] = { 47 { 48 .procname = "nf_conntrack_frag6_timeout", 49 .maxlen = sizeof(unsigned int), 50 .mode = 0644, 51 .proc_handler = proc_dointvec_jiffies, 52 }, 53 { 54 .procname = "nf_conntrack_frag6_low_thresh", 55 .maxlen = sizeof(unsigned long), 56 .mode = 0644, 57 .proc_handler = proc_doulongvec_minmax, 58 }, 59 { 60 .procname = "nf_conntrack_frag6_high_thresh", 61 .maxlen = sizeof(unsigned long), 62 .mode = 0644, 63 .proc_handler = proc_doulongvec_minmax, 64 }, 65 { } 66 }; 67 68 static int nf_ct_frag6_sysctl_register(struct net *net) 69 { 70 struct nft_ct_frag6_pernet *nf_frag; 71 struct ctl_table *table; 72 struct ctl_table_header *hdr; 73 74 table = nf_ct_frag6_sysctl_table; 75 if (!net_eq(net, &init_net)) { 76 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table), 77 GFP_KERNEL); 78 if (table == NULL) 79 goto err_alloc; 80 } 81 82 nf_frag = nf_frag_pernet(net); 83 84 table[0].data = &nf_frag->fqdir->timeout; 85 table[1].data = &nf_frag->fqdir->low_thresh; 86 table[1].extra2 = &nf_frag->fqdir->high_thresh; 87 table[2].data = &nf_frag->fqdir->high_thresh; 88 table[2].extra1 = &nf_frag->fqdir->low_thresh; 89 90 hdr = register_net_sysctl(net, "net/netfilter", table); 91 if (hdr == NULL) 92 goto err_reg; 93 94 nf_frag->nf_frag_frags_hdr = hdr; 95 return 0; 96 97 err_reg: 98 if (!net_eq(net, &init_net)) 99 kfree(table); 100 err_alloc: 101 return -ENOMEM; 102 } 103 104 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net) 105 { 106 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net); 107 struct ctl_table *table; 108 109 table = nf_frag->nf_frag_frags_hdr->ctl_table_arg; 110 unregister_net_sysctl_table(nf_frag->nf_frag_frags_hdr); 111 if (!net_eq(net, &init_net)) 112 kfree(table); 113 } 114 115 #else 116 static int nf_ct_frag6_sysctl_register(struct net *net) 117 { 118 return 0; 119 } 120 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net) 121 { 122 } 123 #endif 124 125 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb, 126 struct sk_buff *prev_tail, struct net_device *dev); 127 128 static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h) 129 { 130 return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK); 131 } 132 133 static void nf_ct_frag6_expire(struct timer_list *t) 134 { 135 struct inet_frag_queue *frag = from_timer(frag, t, timer); 136 struct frag_queue *fq; 137 138 fq = container_of(frag, struct frag_queue, q); 139 140 ip6frag_expire_frag_queue(fq->q.fqdir->net, fq); 141 } 142 143 /* Creation primitives. */ 144 static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user, 145 const struct ipv6hdr *hdr, int iif) 146 { 147 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net); 148 struct frag_v6_compare_key key = { 149 .id = id, 150 .saddr = hdr->saddr, 151 .daddr = hdr->daddr, 152 .user = user, 153 .iif = iif, 154 }; 155 struct inet_frag_queue *q; 156 157 q = inet_frag_find(nf_frag->fqdir, &key); 158 if (!q) 159 return NULL; 160 161 return container_of(q, struct frag_queue, q); 162 } 163 164 165 static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb, 166 const struct frag_hdr *fhdr, int nhoff) 167 { 168 unsigned int payload_len; 169 struct net_device *dev; 170 struct sk_buff *prev; 171 int offset, end, err; 172 u8 ecn; 173 174 if (fq->q.flags & INET_FRAG_COMPLETE) { 175 pr_debug("Already completed\n"); 176 goto err; 177 } 178 179 payload_len = ntohs(ipv6_hdr(skb)->payload_len); 180 181 offset = ntohs(fhdr->frag_off) & ~0x7; 182 end = offset + (payload_len - 183 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1))); 184 185 if ((unsigned int)end > IPV6_MAXPLEN) { 186 pr_debug("offset is too large.\n"); 187 return -EINVAL; 188 } 189 190 ecn = ip6_frag_ecn(ipv6_hdr(skb)); 191 192 if (skb->ip_summed == CHECKSUM_COMPLETE) { 193 const unsigned char *nh = skb_network_header(skb); 194 skb->csum = csum_sub(skb->csum, 195 csum_partial(nh, (u8 *)(fhdr + 1) - nh, 196 0)); 197 } 198 199 /* Is this the final fragment? */ 200 if (!(fhdr->frag_off & htons(IP6_MF))) { 201 /* If we already have some bits beyond end 202 * or have different end, the segment is corrupted. 203 */ 204 if (end < fq->q.len || 205 ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) { 206 pr_debug("already received last fragment\n"); 207 goto err; 208 } 209 fq->q.flags |= INET_FRAG_LAST_IN; 210 fq->q.len = end; 211 } else { 212 /* Check if the fragment is rounded to 8 bytes. 213 * Required by the RFC. 214 */ 215 if (end & 0x7) { 216 /* RFC2460 says always send parameter problem in 217 * this case. -DaveM 218 */ 219 pr_debug("end of fragment not rounded to 8 bytes.\n"); 220 inet_frag_kill(&fq->q); 221 return -EPROTO; 222 } 223 if (end > fq->q.len) { 224 /* Some bits beyond end -> corruption. */ 225 if (fq->q.flags & INET_FRAG_LAST_IN) { 226 pr_debug("last packet already reached.\n"); 227 goto err; 228 } 229 fq->q.len = end; 230 } 231 } 232 233 if (end == offset) 234 goto err; 235 236 /* Point into the IP datagram 'data' part. */ 237 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) { 238 pr_debug("queue: message is too short.\n"); 239 goto err; 240 } 241 if (pskb_trim_rcsum(skb, end - offset)) { 242 pr_debug("Can't trim\n"); 243 goto err; 244 } 245 246 /* Note : skb->rbnode and skb->dev share the same location. */ 247 dev = skb->dev; 248 /* Makes sure compiler wont do silly aliasing games */ 249 barrier(); 250 251 prev = fq->q.fragments_tail; 252 err = inet_frag_queue_insert(&fq->q, skb, offset, end); 253 if (err) { 254 if (err == IPFRAG_DUP) { 255 /* No error for duplicates, pretend they got queued. */ 256 kfree_skb_reason(skb, SKB_DROP_REASON_DUP_FRAG); 257 return -EINPROGRESS; 258 } 259 goto insert_error; 260 } 261 262 if (dev) 263 fq->iif = dev->ifindex; 264 265 fq->q.stamp = skb->tstamp; 266 fq->q.mono_delivery_time = skb->mono_delivery_time; 267 fq->q.meat += skb->len; 268 fq->ecn |= ecn; 269 if (payload_len > fq->q.max_size) 270 fq->q.max_size = payload_len; 271 add_frag_mem_limit(fq->q.fqdir, skb->truesize); 272 273 /* The first fragment. 274 * nhoffset is obtained from the first fragment, of course. 275 */ 276 if (offset == 0) { 277 fq->nhoffset = nhoff; 278 fq->q.flags |= INET_FRAG_FIRST_IN; 279 } 280 281 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && 282 fq->q.meat == fq->q.len) { 283 unsigned long orefdst = skb->_skb_refdst; 284 285 skb->_skb_refdst = 0UL; 286 err = nf_ct_frag6_reasm(fq, skb, prev, dev); 287 skb->_skb_refdst = orefdst; 288 289 /* After queue has assumed skb ownership, only 0 or 290 * -EINPROGRESS must be returned. 291 */ 292 return err ? -EINPROGRESS : 0; 293 } 294 295 skb_dst_drop(skb); 296 return -EINPROGRESS; 297 298 insert_error: 299 inet_frag_kill(&fq->q); 300 err: 301 skb_dst_drop(skb); 302 return -EINVAL; 303 } 304 305 /* 306 * Check if this packet is complete. 307 * 308 * It is called with locked fq, and caller must check that 309 * queue is eligible for reassembly i.e. it is not COMPLETE, 310 * the last and the first frames arrived and all the bits are here. 311 */ 312 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb, 313 struct sk_buff *prev_tail, struct net_device *dev) 314 { 315 void *reasm_data; 316 int payload_len; 317 u8 ecn; 318 319 inet_frag_kill(&fq->q); 320 321 ecn = ip_frag_ecn_table[fq->ecn]; 322 if (unlikely(ecn == 0xff)) 323 goto err; 324 325 reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail); 326 if (!reasm_data) 327 goto err; 328 329 payload_len = ((skb->data - skb_network_header(skb)) - 330 sizeof(struct ipv6hdr) + fq->q.len - 331 sizeof(struct frag_hdr)); 332 if (payload_len > IPV6_MAXPLEN) { 333 net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n", 334 payload_len); 335 goto err; 336 } 337 338 /* We have to remove fragment header from datagram and to relocate 339 * header in order to calculate ICV correctly. */ 340 skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0]; 341 memmove(skb->head + sizeof(struct frag_hdr), skb->head, 342 (skb->data - skb->head) - sizeof(struct frag_hdr)); 343 skb->mac_header += sizeof(struct frag_hdr); 344 skb->network_header += sizeof(struct frag_hdr); 345 346 skb_reset_transport_header(skb); 347 348 inet_frag_reasm_finish(&fq->q, skb, reasm_data, false); 349 350 skb->ignore_df = 1; 351 skb->dev = dev; 352 ipv6_hdr(skb)->payload_len = htons(payload_len); 353 ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn); 354 IP6CB(skb)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size; 355 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED; 356 357 /* Yes, and fold redundant checksum back. 8) */ 358 if (skb->ip_summed == CHECKSUM_COMPLETE) 359 skb->csum = csum_partial(skb_network_header(skb), 360 skb_network_header_len(skb), 361 skb->csum); 362 363 fq->q.rb_fragments = RB_ROOT; 364 fq->q.fragments_tail = NULL; 365 fq->q.last_run_head = NULL; 366 367 return 0; 368 369 err: 370 inet_frag_kill(&fq->q); 371 return -EINVAL; 372 } 373 374 /* 375 * find the header just before Fragment Header. 376 * 377 * if success return 0 and set ... 378 * (*prevhdrp): the value of "Next Header Field" in the header 379 * just before Fragment Header. 380 * (*prevhoff): the offset of "Next Header Field" in the header 381 * just before Fragment Header. 382 * (*fhoff) : the offset of Fragment Header. 383 * 384 * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c 385 * 386 */ 387 static int 388 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff) 389 { 390 u8 nexthdr = ipv6_hdr(skb)->nexthdr; 391 const int netoff = skb_network_offset(skb); 392 u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr); 393 int start = netoff + sizeof(struct ipv6hdr); 394 int len = skb->len - start; 395 u8 prevhdr = NEXTHDR_IPV6; 396 397 while (nexthdr != NEXTHDR_FRAGMENT) { 398 struct ipv6_opt_hdr hdr; 399 int hdrlen; 400 401 if (!ipv6_ext_hdr(nexthdr)) { 402 return -1; 403 } 404 if (nexthdr == NEXTHDR_NONE) { 405 pr_debug("next header is none\n"); 406 return -1; 407 } 408 if (len < (int)sizeof(struct ipv6_opt_hdr)) { 409 pr_debug("too short\n"); 410 return -1; 411 } 412 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr))) 413 BUG(); 414 if (nexthdr == NEXTHDR_AUTH) 415 hdrlen = ipv6_authlen(&hdr); 416 else 417 hdrlen = ipv6_optlen(&hdr); 418 419 prevhdr = nexthdr; 420 prev_nhoff = start; 421 422 nexthdr = hdr.nexthdr; 423 len -= hdrlen; 424 start += hdrlen; 425 } 426 427 if (len < 0) 428 return -1; 429 430 *prevhdrp = prevhdr; 431 *prevhoff = prev_nhoff; 432 *fhoff = start; 433 434 return 0; 435 } 436 437 int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user) 438 { 439 u16 savethdr = skb->transport_header; 440 u8 nexthdr = NEXTHDR_FRAGMENT; 441 int fhoff, nhoff, ret; 442 struct frag_hdr *fhdr; 443 struct frag_queue *fq; 444 struct ipv6hdr *hdr; 445 u8 prevhdr; 446 447 /* Jumbo payload inhibits frag. header */ 448 if (ipv6_hdr(skb)->payload_len == 0) { 449 pr_debug("payload len = 0\n"); 450 return 0; 451 } 452 453 if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0) 454 return 0; 455 456 /* Discard the first fragment if it does not include all headers 457 * RFC 8200, Section 4.5 458 */ 459 if (ipv6frag_thdr_truncated(skb, fhoff, &nexthdr)) { 460 pr_debug("Drop incomplete fragment\n"); 461 return 0; 462 } 463 464 if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr))) 465 return -ENOMEM; 466 467 skb_set_transport_header(skb, fhoff); 468 hdr = ipv6_hdr(skb); 469 fhdr = (struct frag_hdr *)skb_transport_header(skb); 470 471 skb_orphan(skb); 472 fq = fq_find(net, fhdr->identification, user, hdr, 473 skb->dev ? skb->dev->ifindex : 0); 474 if (fq == NULL) { 475 pr_debug("Can't find and can't create new queue\n"); 476 return -ENOMEM; 477 } 478 479 spin_lock_bh(&fq->q.lock); 480 481 ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff); 482 if (ret == -EPROTO) { 483 skb->transport_header = savethdr; 484 ret = 0; 485 } 486 487 spin_unlock_bh(&fq->q.lock); 488 inet_frag_put(&fq->q); 489 return ret; 490 } 491 EXPORT_SYMBOL_GPL(nf_ct_frag6_gather); 492 493 static int nf_ct_net_init(struct net *net) 494 { 495 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net); 496 int res; 497 498 res = fqdir_init(&nf_frag->fqdir, &nf_frags, net); 499 if (res < 0) 500 return res; 501 502 nf_frag->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH; 503 nf_frag->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH; 504 nf_frag->fqdir->timeout = IPV6_FRAG_TIMEOUT; 505 506 res = nf_ct_frag6_sysctl_register(net); 507 if (res < 0) 508 fqdir_exit(nf_frag->fqdir); 509 return res; 510 } 511 512 static void nf_ct_net_pre_exit(struct net *net) 513 { 514 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net); 515 516 fqdir_pre_exit(nf_frag->fqdir); 517 } 518 519 static void nf_ct_net_exit(struct net *net) 520 { 521 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net); 522 523 nf_ct_frags6_sysctl_unregister(net); 524 fqdir_exit(nf_frag->fqdir); 525 } 526 527 static struct pernet_operations nf_ct_net_ops = { 528 .init = nf_ct_net_init, 529 .pre_exit = nf_ct_net_pre_exit, 530 .exit = nf_ct_net_exit, 531 .id = &nf_frag_pernet_id, 532 .size = sizeof(struct nft_ct_frag6_pernet), 533 }; 534 535 static const struct rhashtable_params nfct_rhash_params = { 536 .head_offset = offsetof(struct inet_frag_queue, node), 537 .hashfn = ip6frag_key_hashfn, 538 .obj_hashfn = ip6frag_obj_hashfn, 539 .obj_cmpfn = ip6frag_obj_cmpfn, 540 .automatic_shrinking = true, 541 }; 542 543 int nf_ct_frag6_init(void) 544 { 545 int ret = 0; 546 547 nf_frags.constructor = ip6frag_init; 548 nf_frags.destructor = NULL; 549 nf_frags.qsize = sizeof(struct frag_queue); 550 nf_frags.frag_expire = nf_ct_frag6_expire; 551 nf_frags.frags_cache_name = nf_frags_cache_name; 552 nf_frags.rhash_params = nfct_rhash_params; 553 ret = inet_frags_init(&nf_frags); 554 if (ret) 555 goto out; 556 ret = register_pernet_subsys(&nf_ct_net_ops); 557 if (ret) 558 inet_frags_fini(&nf_frags); 559 560 out: 561 return ret; 562 } 563 564 void nf_ct_frag6_cleanup(void) 565 { 566 unregister_pernet_subsys(&nf_ct_net_ops); 567 inet_frags_fini(&nf_frags); 568 } 569