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/socket.h> 19 #include <linux/sockios.h> 20 #include <linux/jiffies.h> 21 #include <linux/net.h> 22 #include <linux/list.h> 23 #include <linux/netdevice.h> 24 #include <linux/in6.h> 25 #include <linux/ipv6.h> 26 #include <linux/icmpv6.h> 27 #include <linux/random.h> 28 #include <linux/slab.h> 29 30 #include <net/sock.h> 31 #include <net/snmp.h> 32 #include <net/ipv6_frag.h> 33 34 #include <net/protocol.h> 35 #include <net/transp_v6.h> 36 #include <net/rawv6.h> 37 #include <net/ndisc.h> 38 #include <net/addrconf.h> 39 #include <net/inet_ecn.h> 40 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h> 41 #include <linux/sysctl.h> 42 #include <linux/netfilter.h> 43 #include <linux/netfilter_ipv6.h> 44 #include <linux/kernel.h> 45 #include <linux/module.h> 46 #include <net/netfilter/ipv6/nf_defrag_ipv6.h> 47 48 static const char nf_frags_cache_name[] = "nf-frags"; 49 50 static struct inet_frags nf_frags; 51 52 #ifdef CONFIG_SYSCTL 53 54 static struct ctl_table nf_ct_frag6_sysctl_table[] = { 55 { 56 .procname = "nf_conntrack_frag6_timeout", 57 .maxlen = sizeof(unsigned int), 58 .mode = 0644, 59 .proc_handler = proc_dointvec_jiffies, 60 }, 61 { 62 .procname = "nf_conntrack_frag6_low_thresh", 63 .maxlen = sizeof(unsigned long), 64 .mode = 0644, 65 .proc_handler = proc_doulongvec_minmax, 66 }, 67 { 68 .procname = "nf_conntrack_frag6_high_thresh", 69 .maxlen = sizeof(unsigned long), 70 .mode = 0644, 71 .proc_handler = proc_doulongvec_minmax, 72 }, 73 { } 74 }; 75 76 static int nf_ct_frag6_sysctl_register(struct net *net) 77 { 78 struct ctl_table *table; 79 struct ctl_table_header *hdr; 80 81 table = nf_ct_frag6_sysctl_table; 82 if (!net_eq(net, &init_net)) { 83 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table), 84 GFP_KERNEL); 85 if (table == NULL) 86 goto err_alloc; 87 } 88 89 table[0].data = &net->nf_frag.fqdir->timeout; 90 table[1].data = &net->nf_frag.fqdir->low_thresh; 91 table[1].extra2 = &net->nf_frag.fqdir->high_thresh; 92 table[2].data = &net->nf_frag.fqdir->high_thresh; 93 table[2].extra1 = &net->nf_frag.fqdir->low_thresh; 94 table[2].extra2 = &init_net.nf_frag.fqdir->high_thresh; 95 96 hdr = register_net_sysctl(net, "net/netfilter", table); 97 if (hdr == NULL) 98 goto err_reg; 99 100 net->nf_frag_frags_hdr = hdr; 101 return 0; 102 103 err_reg: 104 if (!net_eq(net, &init_net)) 105 kfree(table); 106 err_alloc: 107 return -ENOMEM; 108 } 109 110 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net) 111 { 112 struct ctl_table *table; 113 114 table = net->nf_frag_frags_hdr->ctl_table_arg; 115 unregister_net_sysctl_table(net->nf_frag_frags_hdr); 116 if (!net_eq(net, &init_net)) 117 kfree(table); 118 } 119 120 #else 121 static int nf_ct_frag6_sysctl_register(struct net *net) 122 { 123 return 0; 124 } 125 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net) 126 { 127 } 128 #endif 129 130 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb, 131 struct sk_buff *prev_tail, struct net_device *dev); 132 133 static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h) 134 { 135 return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK); 136 } 137 138 static void nf_ct_frag6_expire(struct timer_list *t) 139 { 140 struct inet_frag_queue *frag = from_timer(frag, t, timer); 141 struct frag_queue *fq; 142 143 fq = container_of(frag, struct frag_queue, q); 144 145 ip6frag_expire_frag_queue(fq->q.fqdir->net, fq); 146 } 147 148 /* Creation primitives. */ 149 static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user, 150 const struct ipv6hdr *hdr, int iif) 151 { 152 struct frag_v6_compare_key key = { 153 .id = id, 154 .saddr = hdr->saddr, 155 .daddr = hdr->daddr, 156 .user = user, 157 .iif = iif, 158 }; 159 struct inet_frag_queue *q; 160 161 q = inet_frag_find(net->nf_frag.fqdir, &key); 162 if (!q) 163 return NULL; 164 165 return container_of(q, struct frag_queue, q); 166 } 167 168 169 static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb, 170 const struct frag_hdr *fhdr, int nhoff) 171 { 172 unsigned int payload_len; 173 struct net_device *dev; 174 struct sk_buff *prev; 175 int offset, end, err; 176 u8 ecn; 177 178 if (fq->q.flags & INET_FRAG_COMPLETE) { 179 pr_debug("Already completed\n"); 180 goto err; 181 } 182 183 payload_len = ntohs(ipv6_hdr(skb)->payload_len); 184 185 offset = ntohs(fhdr->frag_off) & ~0x7; 186 end = offset + (payload_len - 187 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1))); 188 189 if ((unsigned int)end > IPV6_MAXPLEN) { 190 pr_debug("offset is too large.\n"); 191 return -EINVAL; 192 } 193 194 ecn = ip6_frag_ecn(ipv6_hdr(skb)); 195 196 if (skb->ip_summed == CHECKSUM_COMPLETE) { 197 const unsigned char *nh = skb_network_header(skb); 198 skb->csum = csum_sub(skb->csum, 199 csum_partial(nh, (u8 *)(fhdr + 1) - nh, 200 0)); 201 } 202 203 /* Is this the final fragment? */ 204 if (!(fhdr->frag_off & htons(IP6_MF))) { 205 /* If we already have some bits beyond end 206 * or have different end, the segment is corrupted. 207 */ 208 if (end < fq->q.len || 209 ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) { 210 pr_debug("already received last fragment\n"); 211 goto err; 212 } 213 fq->q.flags |= INET_FRAG_LAST_IN; 214 fq->q.len = end; 215 } else { 216 /* Check if the fragment is rounded to 8 bytes. 217 * Required by the RFC. 218 */ 219 if (end & 0x7) { 220 /* RFC2460 says always send parameter problem in 221 * this case. -DaveM 222 */ 223 pr_debug("end of fragment not rounded to 8 bytes.\n"); 224 inet_frag_kill(&fq->q); 225 return -EPROTO; 226 } 227 if (end > fq->q.len) { 228 /* Some bits beyond end -> corruption. */ 229 if (fq->q.flags & INET_FRAG_LAST_IN) { 230 pr_debug("last packet already reached.\n"); 231 goto err; 232 } 233 fq->q.len = end; 234 } 235 } 236 237 if (end == offset) 238 goto err; 239 240 /* Point into the IP datagram 'data' part. */ 241 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) { 242 pr_debug("queue: message is too short.\n"); 243 goto err; 244 } 245 if (pskb_trim_rcsum(skb, end - offset)) { 246 pr_debug("Can't trim\n"); 247 goto err; 248 } 249 250 /* Note : skb->rbnode and skb->dev share the same location. */ 251 dev = skb->dev; 252 /* Makes sure compiler wont do silly aliasing games */ 253 barrier(); 254 255 prev = fq->q.fragments_tail; 256 err = inet_frag_queue_insert(&fq->q, skb, offset, end); 257 if (err) { 258 if (err == IPFRAG_DUP) { 259 /* No error for duplicates, pretend they got queued. */ 260 kfree_skb(skb); 261 return -EINPROGRESS; 262 } 263 goto insert_error; 264 } 265 266 if (dev) 267 fq->iif = dev->ifindex; 268 269 fq->q.stamp = skb->tstamp; 270 fq->q.meat += skb->len; 271 fq->ecn |= ecn; 272 if (payload_len > fq->q.max_size) 273 fq->q.max_size = payload_len; 274 add_frag_mem_limit(fq->q.fqdir, skb->truesize); 275 276 /* The first fragment. 277 * nhoffset is obtained from the first fragment, of course. 278 */ 279 if (offset == 0) { 280 fq->nhoffset = nhoff; 281 fq->q.flags |= INET_FRAG_FIRST_IN; 282 } 283 284 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && 285 fq->q.meat == fq->q.len) { 286 unsigned long orefdst = skb->_skb_refdst; 287 288 skb->_skb_refdst = 0UL; 289 err = nf_ct_frag6_reasm(fq, skb, prev, dev); 290 skb->_skb_refdst = orefdst; 291 292 /* After queue has assumed skb ownership, only 0 or 293 * -EINPROGRESS must be returned. 294 */ 295 return err ? -EINPROGRESS : 0; 296 } 297 298 skb_dst_drop(skb); 299 return -EINPROGRESS; 300 301 insert_error: 302 inet_frag_kill(&fq->q); 303 err: 304 skb_dst_drop(skb); 305 return -EINVAL; 306 } 307 308 /* 309 * Check if this packet is complete. 310 * 311 * It is called with locked fq, and caller must check that 312 * queue is eligible for reassembly i.e. it is not COMPLETE, 313 * the last and the first frames arrived and all the bits are here. 314 */ 315 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb, 316 struct sk_buff *prev_tail, struct net_device *dev) 317 { 318 void *reasm_data; 319 int payload_len; 320 u8 ecn; 321 322 inet_frag_kill(&fq->q); 323 324 ecn = ip_frag_ecn_table[fq->ecn]; 325 if (unlikely(ecn == 0xff)) 326 goto err; 327 328 reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail); 329 if (!reasm_data) 330 goto err; 331 332 payload_len = ((skb->data - skb_network_header(skb)) - 333 sizeof(struct ipv6hdr) + fq->q.len - 334 sizeof(struct frag_hdr)); 335 if (payload_len > IPV6_MAXPLEN) { 336 net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n", 337 payload_len); 338 goto err; 339 } 340 341 /* We have to remove fragment header from datagram and to relocate 342 * header in order to calculate ICV correctly. */ 343 skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0]; 344 memmove(skb->head + sizeof(struct frag_hdr), skb->head, 345 (skb->data - skb->head) - sizeof(struct frag_hdr)); 346 skb->mac_header += sizeof(struct frag_hdr); 347 skb->network_header += sizeof(struct frag_hdr); 348 349 skb_reset_transport_header(skb); 350 351 inet_frag_reasm_finish(&fq->q, skb, reasm_data, false); 352 353 skb->ignore_df = 1; 354 skb->dev = dev; 355 ipv6_hdr(skb)->payload_len = htons(payload_len); 356 ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn); 357 IP6CB(skb)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size; 358 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED; 359 360 /* Yes, and fold redundant checksum back. 8) */ 361 if (skb->ip_summed == CHECKSUM_COMPLETE) 362 skb->csum = csum_partial(skb_network_header(skb), 363 skb_network_header_len(skb), 364 skb->csum); 365 366 fq->q.rb_fragments = RB_ROOT; 367 fq->q.fragments_tail = NULL; 368 fq->q.last_run_head = NULL; 369 370 return 0; 371 372 err: 373 inet_frag_kill(&fq->q); 374 return -EINVAL; 375 } 376 377 /* 378 * find the header just before Fragment Header. 379 * 380 * if success return 0 and set ... 381 * (*prevhdrp): the value of "Next Header Field" in the header 382 * just before Fragment Header. 383 * (*prevhoff): the offset of "Next Header Field" in the header 384 * just before Fragment Header. 385 * (*fhoff) : the offset of Fragment Header. 386 * 387 * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c 388 * 389 */ 390 static int 391 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff) 392 { 393 u8 nexthdr = ipv6_hdr(skb)->nexthdr; 394 const int netoff = skb_network_offset(skb); 395 u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr); 396 int start = netoff + sizeof(struct ipv6hdr); 397 int len = skb->len - start; 398 u8 prevhdr = NEXTHDR_IPV6; 399 400 while (nexthdr != NEXTHDR_FRAGMENT) { 401 struct ipv6_opt_hdr hdr; 402 int hdrlen; 403 404 if (!ipv6_ext_hdr(nexthdr)) { 405 return -1; 406 } 407 if (nexthdr == NEXTHDR_NONE) { 408 pr_debug("next header is none\n"); 409 return -1; 410 } 411 if (len < (int)sizeof(struct ipv6_opt_hdr)) { 412 pr_debug("too short\n"); 413 return -1; 414 } 415 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr))) 416 BUG(); 417 if (nexthdr == NEXTHDR_AUTH) 418 hdrlen = ipv6_authlen(&hdr); 419 else 420 hdrlen = ipv6_optlen(&hdr); 421 422 prevhdr = nexthdr; 423 prev_nhoff = start; 424 425 nexthdr = hdr.nexthdr; 426 len -= hdrlen; 427 start += hdrlen; 428 } 429 430 if (len < 0) 431 return -1; 432 433 *prevhdrp = prevhdr; 434 *prevhoff = prev_nhoff; 435 *fhoff = start; 436 437 return 0; 438 } 439 440 int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user) 441 { 442 u16 savethdr = skb->transport_header; 443 u8 nexthdr = NEXTHDR_FRAGMENT; 444 int fhoff, nhoff, ret; 445 struct frag_hdr *fhdr; 446 struct frag_queue *fq; 447 struct ipv6hdr *hdr; 448 u8 prevhdr; 449 450 /* Jumbo payload inhibits frag. header */ 451 if (ipv6_hdr(skb)->payload_len == 0) { 452 pr_debug("payload len = 0\n"); 453 return 0; 454 } 455 456 if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0) 457 return 0; 458 459 /* Discard the first fragment if it does not include all headers 460 * RFC 8200, Section 4.5 461 */ 462 if (ipv6frag_thdr_truncated(skb, fhoff, &nexthdr)) { 463 pr_debug("Drop incomplete fragment\n"); 464 return 0; 465 } 466 467 if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr))) 468 return -ENOMEM; 469 470 skb_set_transport_header(skb, fhoff); 471 hdr = ipv6_hdr(skb); 472 fhdr = (struct frag_hdr *)skb_transport_header(skb); 473 474 skb_orphan(skb); 475 fq = fq_find(net, fhdr->identification, user, hdr, 476 skb->dev ? skb->dev->ifindex : 0); 477 if (fq == NULL) { 478 pr_debug("Can't find and can't create new queue\n"); 479 return -ENOMEM; 480 } 481 482 spin_lock_bh(&fq->q.lock); 483 484 ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff); 485 if (ret == -EPROTO) { 486 skb->transport_header = savethdr; 487 ret = 0; 488 } 489 490 spin_unlock_bh(&fq->q.lock); 491 inet_frag_put(&fq->q); 492 return ret; 493 } 494 EXPORT_SYMBOL_GPL(nf_ct_frag6_gather); 495 496 static int nf_ct_net_init(struct net *net) 497 { 498 int res; 499 500 res = fqdir_init(&net->nf_frag.fqdir, &nf_frags, net); 501 if (res < 0) 502 return res; 503 504 net->nf_frag.fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH; 505 net->nf_frag.fqdir->low_thresh = IPV6_FRAG_LOW_THRESH; 506 net->nf_frag.fqdir->timeout = IPV6_FRAG_TIMEOUT; 507 508 res = nf_ct_frag6_sysctl_register(net); 509 if (res < 0) 510 fqdir_exit(net->nf_frag.fqdir); 511 return res; 512 } 513 514 static void nf_ct_net_pre_exit(struct net *net) 515 { 516 fqdir_pre_exit(net->nf_frag.fqdir); 517 } 518 519 static void nf_ct_net_exit(struct net *net) 520 { 521 nf_ct_frags6_sysctl_unregister(net); 522 fqdir_exit(net->nf_frag.fqdir); 523 } 524 525 static struct pernet_operations nf_ct_net_ops = { 526 .init = nf_ct_net_init, 527 .pre_exit = nf_ct_net_pre_exit, 528 .exit = nf_ct_net_exit, 529 }; 530 531 static const struct rhashtable_params nfct_rhash_params = { 532 .head_offset = offsetof(struct inet_frag_queue, node), 533 .hashfn = ip6frag_key_hashfn, 534 .obj_hashfn = ip6frag_obj_hashfn, 535 .obj_cmpfn = ip6frag_obj_cmpfn, 536 .automatic_shrinking = true, 537 }; 538 539 int nf_ct_frag6_init(void) 540 { 541 int ret = 0; 542 543 nf_frags.constructor = ip6frag_init; 544 nf_frags.destructor = NULL; 545 nf_frags.qsize = sizeof(struct frag_queue); 546 nf_frags.frag_expire = nf_ct_frag6_expire; 547 nf_frags.frags_cache_name = nf_frags_cache_name; 548 nf_frags.rhash_params = nfct_rhash_params; 549 ret = inet_frags_init(&nf_frags); 550 if (ret) 551 goto out; 552 ret = register_pernet_subsys(&nf_ct_net_ops); 553 if (ret) 554 inet_frags_fini(&nf_frags); 555 556 out: 557 return ret; 558 } 559 560 void nf_ct_frag6_cleanup(void) 561 { 562 unregister_pernet_subsys(&nf_ct_net_ops); 563 inet_frags_fini(&nf_frags); 564 } 565
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