1 /* 2 * inet fragments management 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License 6 * as published by the Free Software Foundation; either version 7 * 2 of the License, or (at your option) any later version. 8 * 9 * Authors: Pavel Emelyanov <xemul@openvz.org> 10 * Started as consolidation of ipv4/ip_fragment.c, 11 * ipv6/reassembly. and ipv6 nf conntrack reassembly 12 */ 13 14 #include <linux/list.h> 15 #include <linux/spinlock.h> 16 #include <linux/module.h> 17 #include <linux/timer.h> 18 #include <linux/mm.h> 19 #include <linux/random.h> 20 #include <linux/skbuff.h> 21 #include <linux/rtnetlink.h> 22 #include <linux/slab.h> 23 #include <linux/rhashtable.h> 24 25 #include <net/sock.h> 26 #include <net/inet_frag.h> 27 #include <net/inet_ecn.h> 28 #include <net/ip.h> 29 #include <net/ipv6.h> 30 31 /* Use skb->cb to track consecutive/adjacent fragments coming at 32 * the end of the queue. Nodes in the rb-tree queue will 33 * contain "runs" of one or more adjacent fragments. 34 * 35 * Invariants: 36 * - next_frag is NULL at the tail of a "run"; 37 * - the head of a "run" has the sum of all fragment lengths in frag_run_len. 38 */ 39 struct ipfrag_skb_cb { 40 union { 41 struct inet_skb_parm h4; 42 struct inet6_skb_parm h6; 43 }; 44 struct sk_buff *next_frag; 45 int frag_run_len; 46 }; 47 48 #define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb)) 49 50 static void fragcb_clear(struct sk_buff *skb) 51 { 52 RB_CLEAR_NODE(&skb->rbnode); 53 FRAG_CB(skb)->next_frag = NULL; 54 FRAG_CB(skb)->frag_run_len = skb->len; 55 } 56 57 /* Append skb to the last "run". */ 58 static void fragrun_append_to_last(struct inet_frag_queue *q, 59 struct sk_buff *skb) 60 { 61 fragcb_clear(skb); 62 63 FRAG_CB(q->last_run_head)->frag_run_len += skb->len; 64 FRAG_CB(q->fragments_tail)->next_frag = skb; 65 q->fragments_tail = skb; 66 } 67 68 /* Create a new "run" with the skb. */ 69 static void fragrun_create(struct inet_frag_queue *q, struct sk_buff *skb) 70 { 71 BUILD_BUG_ON(sizeof(struct ipfrag_skb_cb) > sizeof(skb->cb)); 72 fragcb_clear(skb); 73 74 if (q->last_run_head) 75 rb_link_node(&skb->rbnode, &q->last_run_head->rbnode, 76 &q->last_run_head->rbnode.rb_right); 77 else 78 rb_link_node(&skb->rbnode, NULL, &q->rb_fragments.rb_node); 79 rb_insert_color(&skb->rbnode, &q->rb_fragments); 80 81 q->fragments_tail = skb; 82 q->last_run_head = skb; 83 } 84 85 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements 86 * Value : 0xff if frame should be dropped. 87 * 0 or INET_ECN_CE value, to be ORed in to final iph->tos field 88 */ 89 const u8 ip_frag_ecn_table[16] = { 90 /* at least one fragment had CE, and others ECT_0 or ECT_1 */ 91 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = INET_ECN_CE, 92 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = INET_ECN_CE, 93 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = INET_ECN_CE, 94 95 /* invalid combinations : drop frame */ 96 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff, 97 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff, 98 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff, 99 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff, 100 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff, 101 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff, 102 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff, 103 }; 104 EXPORT_SYMBOL(ip_frag_ecn_table); 105 106 int inet_frags_init(struct inet_frags *f) 107 { 108 f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0, 109 NULL); 110 if (!f->frags_cachep) 111 return -ENOMEM; 112 113 refcount_set(&f->refcnt, 1); 114 init_completion(&f->completion); 115 return 0; 116 } 117 EXPORT_SYMBOL(inet_frags_init); 118 119 void inet_frags_fini(struct inet_frags *f) 120 { 121 if (refcount_dec_and_test(&f->refcnt)) 122 complete(&f->completion); 123 124 wait_for_completion(&f->completion); 125 126 kmem_cache_destroy(f->frags_cachep); 127 f->frags_cachep = NULL; 128 } 129 EXPORT_SYMBOL(inet_frags_fini); 130 131 /* called from rhashtable_free_and_destroy() at netns_frags dismantle */ 132 static void inet_frags_free_cb(void *ptr, void *arg) 133 { 134 struct inet_frag_queue *fq = ptr; 135 int count; 136 137 count = del_timer_sync(&fq->timer) ? 1 : 0; 138 139 spin_lock_bh(&fq->lock); 140 if (!(fq->flags & INET_FRAG_COMPLETE)) { 141 fq->flags |= INET_FRAG_COMPLETE; 142 count++; 143 } else if (fq->flags & INET_FRAG_HASH_DEAD) { 144 count++; 145 } 146 spin_unlock_bh(&fq->lock); 147 148 if (refcount_sub_and_test(count, &fq->refcnt)) 149 inet_frag_destroy(fq); 150 } 151 152 static void fqdir_rwork_fn(struct work_struct *work) 153 { 154 struct fqdir *fqdir = container_of(to_rcu_work(work), 155 struct fqdir, destroy_rwork); 156 struct inet_frags *f = fqdir->f; 157 158 rhashtable_free_and_destroy(&fqdir->rhashtable, inet_frags_free_cb, NULL); 159 160 /* We need to make sure all ongoing call_rcu(..., inet_frag_destroy_rcu) 161 * have completed, since they need to dereference fqdir. 162 * Would it not be nice to have kfree_rcu_barrier() ? :) 163 */ 164 rcu_barrier(); 165 166 if (refcount_dec_and_test(&f->refcnt)) 167 complete(&f->completion); 168 169 kfree(fqdir); 170 } 171 172 int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net) 173 { 174 struct fqdir *fqdir = kzalloc(sizeof(*fqdir), GFP_KERNEL); 175 int res; 176 177 if (!fqdir) 178 return -ENOMEM; 179 fqdir->f = f; 180 fqdir->net = net; 181 res = rhashtable_init(&fqdir->rhashtable, &fqdir->f->rhash_params); 182 if (res < 0) { 183 kfree(fqdir); 184 return res; 185 } 186 refcount_inc(&f->refcnt); 187 *fqdirp = fqdir; 188 return 0; 189 } 190 EXPORT_SYMBOL(fqdir_init); 191 192 void fqdir_exit(struct fqdir *fqdir) 193 { 194 fqdir->high_thresh = 0; /* prevent creation of new frags */ 195 196 fqdir->dead = true; 197 198 /* call_rcu is supposed to provide memory barrier semantics, 199 * separating the setting of fqdir->dead with the destruction 200 * work. This implicit barrier is paired with inet_frag_kill(). 201 */ 202 203 INIT_RCU_WORK(&fqdir->destroy_rwork, fqdir_rwork_fn); 204 queue_rcu_work(system_wq, &fqdir->destroy_rwork); 205 206 } 207 EXPORT_SYMBOL(fqdir_exit); 208 209 void inet_frag_kill(struct inet_frag_queue *fq) 210 { 211 if (del_timer(&fq->timer)) 212 refcount_dec(&fq->refcnt); 213 214 if (!(fq->flags & INET_FRAG_COMPLETE)) { 215 struct fqdir *fqdir = fq->fqdir; 216 217 fq->flags |= INET_FRAG_COMPLETE; 218 rcu_read_lock(); 219 /* The RCU read lock provides a memory barrier 220 * guaranteeing that if fqdir->dead is false then 221 * the hash table destruction will not start until 222 * after we unlock. Paired with inet_frags_exit_net(). 223 */ 224 if (!fqdir->dead) { 225 rhashtable_remove_fast(&fqdir->rhashtable, &fq->node, 226 fqdir->f->rhash_params); 227 refcount_dec(&fq->refcnt); 228 } else { 229 fq->flags |= INET_FRAG_HASH_DEAD; 230 } 231 rcu_read_unlock(); 232 } 233 } 234 EXPORT_SYMBOL(inet_frag_kill); 235 236 static void inet_frag_destroy_rcu(struct rcu_head *head) 237 { 238 struct inet_frag_queue *q = container_of(head, struct inet_frag_queue, 239 rcu); 240 struct inet_frags *f = q->fqdir->f; 241 242 if (f->destructor) 243 f->destructor(q); 244 kmem_cache_free(f->frags_cachep, q); 245 } 246 247 unsigned int inet_frag_rbtree_purge(struct rb_root *root) 248 { 249 struct rb_node *p = rb_first(root); 250 unsigned int sum = 0; 251 252 while (p) { 253 struct sk_buff *skb = rb_entry(p, struct sk_buff, rbnode); 254 255 p = rb_next(p); 256 rb_erase(&skb->rbnode, root); 257 while (skb) { 258 struct sk_buff *next = FRAG_CB(skb)->next_frag; 259 260 sum += skb->truesize; 261 kfree_skb(skb); 262 skb = next; 263 } 264 } 265 return sum; 266 } 267 EXPORT_SYMBOL(inet_frag_rbtree_purge); 268 269 void inet_frag_destroy(struct inet_frag_queue *q) 270 { 271 struct fqdir *fqdir; 272 unsigned int sum, sum_truesize = 0; 273 struct inet_frags *f; 274 275 WARN_ON(!(q->flags & INET_FRAG_COMPLETE)); 276 WARN_ON(del_timer(&q->timer) != 0); 277 278 /* Release all fragment data. */ 279 fqdir = q->fqdir; 280 f = fqdir->f; 281 sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments); 282 sum = sum_truesize + f->qsize; 283 284 call_rcu(&q->rcu, inet_frag_destroy_rcu); 285 286 sub_frag_mem_limit(fqdir, sum); 287 } 288 EXPORT_SYMBOL(inet_frag_destroy); 289 290 static struct inet_frag_queue *inet_frag_alloc(struct fqdir *fqdir, 291 struct inet_frags *f, 292 void *arg) 293 { 294 struct inet_frag_queue *q; 295 296 q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC); 297 if (!q) 298 return NULL; 299 300 q->fqdir = fqdir; 301 f->constructor(q, arg); 302 add_frag_mem_limit(fqdir, f->qsize); 303 304 timer_setup(&q->timer, f->frag_expire, 0); 305 spin_lock_init(&q->lock); 306 refcount_set(&q->refcnt, 3); 307 308 return q; 309 } 310 311 static struct inet_frag_queue *inet_frag_create(struct fqdir *fqdir, 312 void *arg, 313 struct inet_frag_queue **prev) 314 { 315 struct inet_frags *f = fqdir->f; 316 struct inet_frag_queue *q; 317 318 q = inet_frag_alloc(fqdir, f, arg); 319 if (!q) { 320 *prev = ERR_PTR(-ENOMEM); 321 return NULL; 322 } 323 mod_timer(&q->timer, jiffies + fqdir->timeout); 324 325 *prev = rhashtable_lookup_get_insert_key(&fqdir->rhashtable, &q->key, 326 &q->node, f->rhash_params); 327 if (*prev) { 328 q->flags |= INET_FRAG_COMPLETE; 329 inet_frag_kill(q); 330 inet_frag_destroy(q); 331 return NULL; 332 } 333 return q; 334 } 335 336 /* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */ 337 struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key) 338 { 339 struct inet_frag_queue *fq = NULL, *prev; 340 341 if (!fqdir->high_thresh || frag_mem_limit(fqdir) > fqdir->high_thresh) 342 return NULL; 343 344 rcu_read_lock(); 345 346 prev = rhashtable_lookup(&fqdir->rhashtable, key, fqdir->f->rhash_params); 347 if (!prev) 348 fq = inet_frag_create(fqdir, key, &prev); 349 if (prev && !IS_ERR(prev)) { 350 fq = prev; 351 if (!refcount_inc_not_zero(&fq->refcnt)) 352 fq = NULL; 353 } 354 rcu_read_unlock(); 355 return fq; 356 } 357 EXPORT_SYMBOL(inet_frag_find); 358 359 int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb, 360 int offset, int end) 361 { 362 struct sk_buff *last = q->fragments_tail; 363 364 /* RFC5722, Section 4, amended by Errata ID : 3089 365 * When reassembling an IPv6 datagram, if 366 * one or more its constituent fragments is determined to be an 367 * overlapping fragment, the entire datagram (and any constituent 368 * fragments) MUST be silently discarded. 369 * 370 * Duplicates, however, should be ignored (i.e. skb dropped, but the 371 * queue/fragments kept for later reassembly). 372 */ 373 if (!last) 374 fragrun_create(q, skb); /* First fragment. */ 375 else if (last->ip_defrag_offset + last->len < end) { 376 /* This is the common case: skb goes to the end. */ 377 /* Detect and discard overlaps. */ 378 if (offset < last->ip_defrag_offset + last->len) 379 return IPFRAG_OVERLAP; 380 if (offset == last->ip_defrag_offset + last->len) 381 fragrun_append_to_last(q, skb); 382 else 383 fragrun_create(q, skb); 384 } else { 385 /* Binary search. Note that skb can become the first fragment, 386 * but not the last (covered above). 387 */ 388 struct rb_node **rbn, *parent; 389 390 rbn = &q->rb_fragments.rb_node; 391 do { 392 struct sk_buff *curr; 393 int curr_run_end; 394 395 parent = *rbn; 396 curr = rb_to_skb(parent); 397 curr_run_end = curr->ip_defrag_offset + 398 FRAG_CB(curr)->frag_run_len; 399 if (end <= curr->ip_defrag_offset) 400 rbn = &parent->rb_left; 401 else if (offset >= curr_run_end) 402 rbn = &parent->rb_right; 403 else if (offset >= curr->ip_defrag_offset && 404 end <= curr_run_end) 405 return IPFRAG_DUP; 406 else 407 return IPFRAG_OVERLAP; 408 } while (*rbn); 409 /* Here we have parent properly set, and rbn pointing to 410 * one of its NULL left/right children. Insert skb. 411 */ 412 fragcb_clear(skb); 413 rb_link_node(&skb->rbnode, parent, rbn); 414 rb_insert_color(&skb->rbnode, &q->rb_fragments); 415 } 416 417 skb->ip_defrag_offset = offset; 418 419 return IPFRAG_OK; 420 } 421 EXPORT_SYMBOL(inet_frag_queue_insert); 422 423 void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb, 424 struct sk_buff *parent) 425 { 426 struct sk_buff *fp, *head = skb_rb_first(&q->rb_fragments); 427 struct sk_buff **nextp; 428 int delta; 429 430 if (head != skb) { 431 fp = skb_clone(skb, GFP_ATOMIC); 432 if (!fp) 433 return NULL; 434 FRAG_CB(fp)->next_frag = FRAG_CB(skb)->next_frag; 435 if (RB_EMPTY_NODE(&skb->rbnode)) 436 FRAG_CB(parent)->next_frag = fp; 437 else 438 rb_replace_node(&skb->rbnode, &fp->rbnode, 439 &q->rb_fragments); 440 if (q->fragments_tail == skb) 441 q->fragments_tail = fp; 442 skb_morph(skb, head); 443 FRAG_CB(skb)->next_frag = FRAG_CB(head)->next_frag; 444 rb_replace_node(&head->rbnode, &skb->rbnode, 445 &q->rb_fragments); 446 consume_skb(head); 447 head = skb; 448 } 449 WARN_ON(head->ip_defrag_offset != 0); 450 451 delta = -head->truesize; 452 453 /* Head of list must not be cloned. */ 454 if (skb_unclone(head, GFP_ATOMIC)) 455 return NULL; 456 457 delta += head->truesize; 458 if (delta) 459 add_frag_mem_limit(q->fqdir, delta); 460 461 /* If the first fragment is fragmented itself, we split 462 * it to two chunks: the first with data and paged part 463 * and the second, holding only fragments. 464 */ 465 if (skb_has_frag_list(head)) { 466 struct sk_buff *clone; 467 int i, plen = 0; 468 469 clone = alloc_skb(0, GFP_ATOMIC); 470 if (!clone) 471 return NULL; 472 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list; 473 skb_frag_list_init(head); 474 for (i = 0; i < skb_shinfo(head)->nr_frags; i++) 475 plen += skb_frag_size(&skb_shinfo(head)->frags[i]); 476 clone->data_len = head->data_len - plen; 477 clone->len = clone->data_len; 478 head->truesize += clone->truesize; 479 clone->csum = 0; 480 clone->ip_summed = head->ip_summed; 481 add_frag_mem_limit(q->fqdir, clone->truesize); 482 skb_shinfo(head)->frag_list = clone; 483 nextp = &clone->next; 484 } else { 485 nextp = &skb_shinfo(head)->frag_list; 486 } 487 488 return nextp; 489 } 490 EXPORT_SYMBOL(inet_frag_reasm_prepare); 491 492 void inet_frag_reasm_finish(struct inet_frag_queue *q, struct sk_buff *head, 493 void *reasm_data) 494 { 495 struct sk_buff **nextp = (struct sk_buff **)reasm_data; 496 struct rb_node *rbn; 497 struct sk_buff *fp; 498 499 skb_push(head, head->data - skb_network_header(head)); 500 501 /* Traverse the tree in order, to build frag_list. */ 502 fp = FRAG_CB(head)->next_frag; 503 rbn = rb_next(&head->rbnode); 504 rb_erase(&head->rbnode, &q->rb_fragments); 505 while (rbn || fp) { 506 /* fp points to the next sk_buff in the current run; 507 * rbn points to the next run. 508 */ 509 /* Go through the current run. */ 510 while (fp) { 511 *nextp = fp; 512 nextp = &fp->next; 513 fp->prev = NULL; 514 memset(&fp->rbnode, 0, sizeof(fp->rbnode)); 515 fp->sk = NULL; 516 head->data_len += fp->len; 517 head->len += fp->len; 518 if (head->ip_summed != fp->ip_summed) 519 head->ip_summed = CHECKSUM_NONE; 520 else if (head->ip_summed == CHECKSUM_COMPLETE) 521 head->csum = csum_add(head->csum, fp->csum); 522 head->truesize += fp->truesize; 523 fp = FRAG_CB(fp)->next_frag; 524 } 525 /* Move to the next run. */ 526 if (rbn) { 527 struct rb_node *rbnext = rb_next(rbn); 528 529 fp = rb_to_skb(rbn); 530 rb_erase(rbn, &q->rb_fragments); 531 rbn = rbnext; 532 } 533 } 534 sub_frag_mem_limit(q->fqdir, head->truesize); 535 536 *nextp = NULL; 537 skb_mark_not_on_list(head); 538 head->prev = NULL; 539 head->tstamp = q->stamp; 540 } 541 EXPORT_SYMBOL(inet_frag_reasm_finish); 542 543 struct sk_buff *inet_frag_pull_head(struct inet_frag_queue *q) 544 { 545 struct sk_buff *head, *skb; 546 547 head = skb_rb_first(&q->rb_fragments); 548 if (!head) 549 return NULL; 550 skb = FRAG_CB(head)->next_frag; 551 if (skb) 552 rb_replace_node(&head->rbnode, &skb->rbnode, 553 &q->rb_fragments); 554 else 555 rb_erase(&head->rbnode, &q->rb_fragments); 556 memset(&head->rbnode, 0, sizeof(head->rbnode)); 557 barrier(); 558 559 if (head == q->fragments_tail) 560 q->fragments_tail = NULL; 561 562 sub_frag_mem_limit(q->fqdir, head->truesize); 563 564 return head; 565 } 566 EXPORT_SYMBOL(inet_frag_pull_head); 567