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