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 24 #include <net/sock.h> 25 #include <net/inet_frag.h> 26 #include <net/inet_ecn.h> 27 28 #define INETFRAGS_EVICT_BUCKETS 128 29 #define INETFRAGS_EVICT_MAX 512 30 31 /* don't rebuild inetfrag table with new secret more often than this */ 32 #define INETFRAGS_MIN_REBUILD_INTERVAL (5 * HZ) 33 34 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements 35 * Value : 0xff if frame should be dropped. 36 * 0 or INET_ECN_CE value, to be ORed in to final iph->tos field 37 */ 38 const u8 ip_frag_ecn_table[16] = { 39 /* at least one fragment had CE, and others ECT_0 or ECT_1 */ 40 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = INET_ECN_CE, 41 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = INET_ECN_CE, 42 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = INET_ECN_CE, 43 44 /* invalid combinations : drop frame */ 45 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff, 46 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff, 47 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff, 48 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff, 49 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff, 50 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff, 51 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff, 52 }; 53 EXPORT_SYMBOL(ip_frag_ecn_table); 54 55 static unsigned int 56 inet_frag_hashfn(const struct inet_frags *f, const struct inet_frag_queue *q) 57 { 58 return f->hashfn(q) & (INETFRAGS_HASHSZ - 1); 59 } 60 61 static bool inet_frag_may_rebuild(struct inet_frags *f) 62 { 63 return time_after(jiffies, 64 f->last_rebuild_jiffies + INETFRAGS_MIN_REBUILD_INTERVAL); 65 } 66 67 static void inet_frag_secret_rebuild(struct inet_frags *f) 68 { 69 int i; 70 71 write_seqlock_bh(&f->rnd_seqlock); 72 73 if (!inet_frag_may_rebuild(f)) 74 goto out; 75 76 get_random_bytes(&f->rnd, sizeof(u32)); 77 78 for (i = 0; i < INETFRAGS_HASHSZ; i++) { 79 struct inet_frag_bucket *hb; 80 struct inet_frag_queue *q; 81 struct hlist_node *n; 82 83 hb = &f->hash[i]; 84 spin_lock(&hb->chain_lock); 85 86 hlist_for_each_entry_safe(q, n, &hb->chain, list) { 87 unsigned int hval = inet_frag_hashfn(f, q); 88 89 if (hval != i) { 90 struct inet_frag_bucket *hb_dest; 91 92 hlist_del(&q->list); 93 94 /* Relink to new hash chain. */ 95 hb_dest = &f->hash[hval]; 96 97 /* This is the only place where we take 98 * another chain_lock while already holding 99 * one. As this will not run concurrently, 100 * we cannot deadlock on hb_dest lock below, if its 101 * already locked it will be released soon since 102 * other caller cannot be waiting for hb lock 103 * that we've taken above. 104 */ 105 spin_lock_nested(&hb_dest->chain_lock, 106 SINGLE_DEPTH_NESTING); 107 hlist_add_head(&q->list, &hb_dest->chain); 108 spin_unlock(&hb_dest->chain_lock); 109 } 110 } 111 spin_unlock(&hb->chain_lock); 112 } 113 114 f->rebuild = false; 115 f->last_rebuild_jiffies = jiffies; 116 out: 117 write_sequnlock_bh(&f->rnd_seqlock); 118 } 119 120 static bool inet_fragq_should_evict(const struct inet_frag_queue *q) 121 { 122 return q->net->low_thresh == 0 || 123 frag_mem_limit(q->net) >= q->net->low_thresh; 124 } 125 126 static unsigned int 127 inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb) 128 { 129 struct inet_frag_queue *fq; 130 struct hlist_node *n; 131 unsigned int evicted = 0; 132 HLIST_HEAD(expired); 133 134 evict_again: 135 spin_lock(&hb->chain_lock); 136 137 hlist_for_each_entry_safe(fq, n, &hb->chain, list) { 138 if (!inet_fragq_should_evict(fq)) 139 continue; 140 141 if (!del_timer(&fq->timer)) { 142 /* q expiring right now thus increment its refcount so 143 * it won't be freed under us and wait until the timer 144 * has finished executing then destroy it 145 */ 146 atomic_inc(&fq->refcnt); 147 spin_unlock(&hb->chain_lock); 148 del_timer_sync(&fq->timer); 149 inet_frag_put(fq, f); 150 goto evict_again; 151 } 152 153 fq->flags |= INET_FRAG_EVICTED; 154 hlist_del(&fq->list); 155 hlist_add_head(&fq->list, &expired); 156 ++evicted; 157 } 158 159 spin_unlock(&hb->chain_lock); 160 161 hlist_for_each_entry_safe(fq, n, &expired, list) 162 f->frag_expire((unsigned long) fq); 163 164 return evicted; 165 } 166 167 static void inet_frag_worker(struct work_struct *work) 168 { 169 unsigned int budget = INETFRAGS_EVICT_BUCKETS; 170 unsigned int i, evicted = 0; 171 struct inet_frags *f; 172 173 f = container_of(work, struct inet_frags, frags_work); 174 175 BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ); 176 177 local_bh_disable(); 178 179 for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) { 180 evicted += inet_evict_bucket(f, &f->hash[i]); 181 i = (i + 1) & (INETFRAGS_HASHSZ - 1); 182 if (evicted > INETFRAGS_EVICT_MAX) 183 break; 184 } 185 186 f->next_bucket = i; 187 188 local_bh_enable(); 189 190 if (f->rebuild && inet_frag_may_rebuild(f)) 191 inet_frag_secret_rebuild(f); 192 } 193 194 static void inet_frag_schedule_worker(struct inet_frags *f) 195 { 196 if (unlikely(!work_pending(&f->frags_work))) 197 schedule_work(&f->frags_work); 198 } 199 200 int inet_frags_init(struct inet_frags *f) 201 { 202 int i; 203 204 INIT_WORK(&f->frags_work, inet_frag_worker); 205 206 for (i = 0; i < INETFRAGS_HASHSZ; i++) { 207 struct inet_frag_bucket *hb = &f->hash[i]; 208 209 spin_lock_init(&hb->chain_lock); 210 INIT_HLIST_HEAD(&hb->chain); 211 } 212 213 seqlock_init(&f->rnd_seqlock); 214 f->last_rebuild_jiffies = 0; 215 f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0, 216 NULL); 217 if (!f->frags_cachep) 218 return -ENOMEM; 219 220 return 0; 221 } 222 EXPORT_SYMBOL(inet_frags_init); 223 224 void inet_frags_init_net(struct netns_frags *nf) 225 { 226 init_frag_mem_limit(nf); 227 } 228 EXPORT_SYMBOL(inet_frags_init_net); 229 230 void inet_frags_fini(struct inet_frags *f) 231 { 232 cancel_work_sync(&f->frags_work); 233 kmem_cache_destroy(f->frags_cachep); 234 } 235 EXPORT_SYMBOL(inet_frags_fini); 236 237 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f) 238 { 239 unsigned int seq; 240 int i; 241 242 nf->low_thresh = 0; 243 local_bh_disable(); 244 245 evict_again: 246 seq = read_seqbegin(&f->rnd_seqlock); 247 248 for (i = 0; i < INETFRAGS_HASHSZ ; i++) 249 inet_evict_bucket(f, &f->hash[i]); 250 251 if (read_seqretry(&f->rnd_seqlock, seq)) 252 goto evict_again; 253 254 local_bh_enable(); 255 256 percpu_counter_destroy(&nf->mem); 257 } 258 EXPORT_SYMBOL(inet_frags_exit_net); 259 260 static struct inet_frag_bucket * 261 get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f) 262 __acquires(hb->chain_lock) 263 { 264 struct inet_frag_bucket *hb; 265 unsigned int seq, hash; 266 267 restart: 268 seq = read_seqbegin(&f->rnd_seqlock); 269 270 hash = inet_frag_hashfn(f, fq); 271 hb = &f->hash[hash]; 272 273 spin_lock(&hb->chain_lock); 274 if (read_seqretry(&f->rnd_seqlock, seq)) { 275 spin_unlock(&hb->chain_lock); 276 goto restart; 277 } 278 279 return hb; 280 } 281 282 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f) 283 { 284 struct inet_frag_bucket *hb; 285 286 hb = get_frag_bucket_locked(fq, f); 287 if (!(fq->flags & INET_FRAG_EVICTED)) 288 hlist_del(&fq->list); 289 spin_unlock(&hb->chain_lock); 290 } 291 292 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f) 293 { 294 if (del_timer(&fq->timer)) 295 atomic_dec(&fq->refcnt); 296 297 if (!(fq->flags & INET_FRAG_COMPLETE)) { 298 fq_unlink(fq, f); 299 atomic_dec(&fq->refcnt); 300 fq->flags |= INET_FRAG_COMPLETE; 301 } 302 } 303 EXPORT_SYMBOL(inet_frag_kill); 304 305 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f, 306 struct sk_buff *skb) 307 { 308 if (f->skb_free) 309 f->skb_free(skb); 310 kfree_skb(skb); 311 } 312 313 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f) 314 { 315 struct sk_buff *fp; 316 struct netns_frags *nf; 317 unsigned int sum, sum_truesize = 0; 318 319 WARN_ON(!(q->flags & INET_FRAG_COMPLETE)); 320 WARN_ON(del_timer(&q->timer) != 0); 321 322 /* Release all fragment data. */ 323 fp = q->fragments; 324 nf = q->net; 325 while (fp) { 326 struct sk_buff *xp = fp->next; 327 328 sum_truesize += fp->truesize; 329 frag_kfree_skb(nf, f, fp); 330 fp = xp; 331 } 332 sum = sum_truesize + f->qsize; 333 sub_frag_mem_limit(q, sum); 334 335 if (f->destructor) 336 f->destructor(q); 337 kmem_cache_free(f->frags_cachep, q); 338 } 339 EXPORT_SYMBOL(inet_frag_destroy); 340 341 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf, 342 struct inet_frag_queue *qp_in, 343 struct inet_frags *f, 344 void *arg) 345 { 346 struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f); 347 struct inet_frag_queue *qp; 348 349 #ifdef CONFIG_SMP 350 /* With SMP race we have to recheck hash table, because 351 * such entry could have been created on other cpu before 352 * we acquired hash bucket lock. 353 */ 354 hlist_for_each_entry(qp, &hb->chain, list) { 355 if (qp->net == nf && f->match(qp, arg)) { 356 atomic_inc(&qp->refcnt); 357 spin_unlock(&hb->chain_lock); 358 qp_in->flags |= INET_FRAG_COMPLETE; 359 inet_frag_put(qp_in, f); 360 return qp; 361 } 362 } 363 #endif 364 qp = qp_in; 365 if (!mod_timer(&qp->timer, jiffies + nf->timeout)) 366 atomic_inc(&qp->refcnt); 367 368 atomic_inc(&qp->refcnt); 369 hlist_add_head(&qp->list, &hb->chain); 370 371 spin_unlock(&hb->chain_lock); 372 373 return qp; 374 } 375 376 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf, 377 struct inet_frags *f, 378 void *arg) 379 { 380 struct inet_frag_queue *q; 381 382 if (frag_mem_limit(nf) > nf->high_thresh) { 383 inet_frag_schedule_worker(f); 384 return NULL; 385 } 386 387 q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC); 388 if (q == NULL) 389 return NULL; 390 391 q->net = nf; 392 f->constructor(q, arg); 393 add_frag_mem_limit(q, f->qsize); 394 395 setup_timer(&q->timer, f->frag_expire, (unsigned long)q); 396 spin_lock_init(&q->lock); 397 atomic_set(&q->refcnt, 1); 398 399 return q; 400 } 401 402 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf, 403 struct inet_frags *f, 404 void *arg) 405 { 406 struct inet_frag_queue *q; 407 408 q = inet_frag_alloc(nf, f, arg); 409 if (q == NULL) 410 return NULL; 411 412 return inet_frag_intern(nf, q, f, arg); 413 } 414 415 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, 416 struct inet_frags *f, void *key, 417 unsigned int hash) 418 { 419 struct inet_frag_bucket *hb; 420 struct inet_frag_queue *q; 421 int depth = 0; 422 423 if (frag_mem_limit(nf) > nf->low_thresh) 424 inet_frag_schedule_worker(f); 425 426 hash &= (INETFRAGS_HASHSZ - 1); 427 hb = &f->hash[hash]; 428 429 spin_lock(&hb->chain_lock); 430 hlist_for_each_entry(q, &hb->chain, list) { 431 if (q->net == nf && f->match(q, key)) { 432 atomic_inc(&q->refcnt); 433 spin_unlock(&hb->chain_lock); 434 return q; 435 } 436 depth++; 437 } 438 spin_unlock(&hb->chain_lock); 439 440 if (depth <= INETFRAGS_MAXDEPTH) 441 return inet_frag_create(nf, f, key); 442 443 if (inet_frag_may_rebuild(f)) { 444 if (!f->rebuild) 445 f->rebuild = true; 446 inet_frag_schedule_worker(f); 447 } 448 449 return ERR_PTR(-ENOBUFS); 450 } 451 EXPORT_SYMBOL(inet_frag_find); 452 453 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q, 454 const char *prefix) 455 { 456 static const char msg[] = "inet_frag_find: Fragment hash bucket" 457 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH) 458 ". Dropping fragment.\n"; 459 460 if (PTR_ERR(q) == -ENOBUFS) 461 net_dbg_ratelimited("%s%s", prefix, msg); 462 } 463 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow); 464