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 if (!hlist_unhashed(&q->list_evictor)) 123 return false; 124 125 return q->net->low_thresh == 0 || 126 frag_mem_limit(q->net) >= q->net->low_thresh; 127 } 128 129 static unsigned int 130 inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb) 131 { 132 struct inet_frag_queue *fq; 133 struct hlist_node *n; 134 unsigned int evicted = 0; 135 HLIST_HEAD(expired); 136 137 spin_lock(&hb->chain_lock); 138 139 hlist_for_each_entry_safe(fq, n, &hb->chain, list) { 140 if (!inet_fragq_should_evict(fq)) 141 continue; 142 143 if (!del_timer(&fq->timer)) 144 continue; 145 146 hlist_add_head(&fq->list_evictor, &expired); 147 ++evicted; 148 } 149 150 spin_unlock(&hb->chain_lock); 151 152 hlist_for_each_entry_safe(fq, n, &expired, list_evictor) 153 f->frag_expire(&fq->timer); 154 155 return evicted; 156 } 157 158 static void inet_frag_worker(struct work_struct *work) 159 { 160 unsigned int budget = INETFRAGS_EVICT_BUCKETS; 161 unsigned int i, evicted = 0; 162 struct inet_frags *f; 163 164 f = container_of(work, struct inet_frags, frags_work); 165 166 BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ); 167 168 local_bh_disable(); 169 170 for (i = READ_ONCE(f->next_bucket); budget; --budget) { 171 evicted += inet_evict_bucket(f, &f->hash[i]); 172 i = (i + 1) & (INETFRAGS_HASHSZ - 1); 173 if (evicted > INETFRAGS_EVICT_MAX) 174 break; 175 } 176 177 f->next_bucket = i; 178 179 local_bh_enable(); 180 181 if (f->rebuild && inet_frag_may_rebuild(f)) 182 inet_frag_secret_rebuild(f); 183 } 184 185 static void inet_frag_schedule_worker(struct inet_frags *f) 186 { 187 if (unlikely(!work_pending(&f->frags_work))) 188 schedule_work(&f->frags_work); 189 } 190 191 int inet_frags_init(struct inet_frags *f) 192 { 193 int i; 194 195 INIT_WORK(&f->frags_work, inet_frag_worker); 196 197 for (i = 0; i < INETFRAGS_HASHSZ; i++) { 198 struct inet_frag_bucket *hb = &f->hash[i]; 199 200 spin_lock_init(&hb->chain_lock); 201 INIT_HLIST_HEAD(&hb->chain); 202 } 203 204 seqlock_init(&f->rnd_seqlock); 205 f->last_rebuild_jiffies = 0; 206 f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0, 207 NULL); 208 if (!f->frags_cachep) 209 return -ENOMEM; 210 211 return 0; 212 } 213 EXPORT_SYMBOL(inet_frags_init); 214 215 void inet_frags_fini(struct inet_frags *f) 216 { 217 cancel_work_sync(&f->frags_work); 218 kmem_cache_destroy(f->frags_cachep); 219 } 220 EXPORT_SYMBOL(inet_frags_fini); 221 222 void inet_frags_exit_net(struct netns_frags *nf) 223 { 224 struct inet_frags *f =nf->f; 225 unsigned int seq; 226 int i; 227 228 nf->low_thresh = 0; 229 230 evict_again: 231 local_bh_disable(); 232 seq = read_seqbegin(&f->rnd_seqlock); 233 234 for (i = 0; i < INETFRAGS_HASHSZ ; i++) 235 inet_evict_bucket(f, &f->hash[i]); 236 237 local_bh_enable(); 238 cond_resched(); 239 240 if (read_seqretry(&f->rnd_seqlock, seq) || 241 sum_frag_mem_limit(nf)) 242 goto evict_again; 243 } 244 EXPORT_SYMBOL(inet_frags_exit_net); 245 246 static struct inet_frag_bucket * 247 get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f) 248 __acquires(hb->chain_lock) 249 { 250 struct inet_frag_bucket *hb; 251 unsigned int seq, hash; 252 253 restart: 254 seq = read_seqbegin(&f->rnd_seqlock); 255 256 hash = inet_frag_hashfn(f, fq); 257 hb = &f->hash[hash]; 258 259 spin_lock(&hb->chain_lock); 260 if (read_seqretry(&f->rnd_seqlock, seq)) { 261 spin_unlock(&hb->chain_lock); 262 goto restart; 263 } 264 265 return hb; 266 } 267 268 static inline void fq_unlink(struct inet_frag_queue *fq) 269 { 270 struct inet_frag_bucket *hb; 271 272 hb = get_frag_bucket_locked(fq, fq->net->f); 273 hlist_del(&fq->list); 274 fq->flags |= INET_FRAG_COMPLETE; 275 spin_unlock(&hb->chain_lock); 276 } 277 278 void inet_frag_kill(struct inet_frag_queue *fq) 279 { 280 if (del_timer(&fq->timer)) 281 refcount_dec(&fq->refcnt); 282 283 if (!(fq->flags & INET_FRAG_COMPLETE)) { 284 fq_unlink(fq); 285 refcount_dec(&fq->refcnt); 286 } 287 } 288 EXPORT_SYMBOL(inet_frag_kill); 289 290 void inet_frag_destroy(struct inet_frag_queue *q) 291 { 292 struct sk_buff *fp; 293 struct netns_frags *nf; 294 unsigned int sum, sum_truesize = 0; 295 struct inet_frags *f; 296 297 WARN_ON(!(q->flags & INET_FRAG_COMPLETE)); 298 WARN_ON(del_timer(&q->timer) != 0); 299 300 /* Release all fragment data. */ 301 fp = q->fragments; 302 nf = q->net; 303 f = nf->f; 304 while (fp) { 305 struct sk_buff *xp = fp->next; 306 307 sum_truesize += fp->truesize; 308 kfree_skb(fp); 309 fp = xp; 310 } 311 sum = sum_truesize + f->qsize; 312 313 if (f->destructor) 314 f->destructor(q); 315 kmem_cache_free(f->frags_cachep, q); 316 317 sub_frag_mem_limit(nf, sum); 318 } 319 EXPORT_SYMBOL(inet_frag_destroy); 320 321 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf, 322 struct inet_frag_queue *qp_in, 323 struct inet_frags *f, 324 void *arg) 325 { 326 struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f); 327 struct inet_frag_queue *qp; 328 329 #ifdef CONFIG_SMP 330 /* With SMP race we have to recheck hash table, because 331 * such entry could have been created on other cpu before 332 * we acquired hash bucket lock. 333 */ 334 hlist_for_each_entry(qp, &hb->chain, list) { 335 if (qp->net == nf && f->match(qp, arg)) { 336 refcount_inc(&qp->refcnt); 337 spin_unlock(&hb->chain_lock); 338 qp_in->flags |= INET_FRAG_COMPLETE; 339 inet_frag_put(qp_in); 340 return qp; 341 } 342 } 343 #endif 344 qp = qp_in; 345 if (!mod_timer(&qp->timer, jiffies + nf->timeout)) 346 refcount_inc(&qp->refcnt); 347 348 refcount_inc(&qp->refcnt); 349 hlist_add_head(&qp->list, &hb->chain); 350 351 spin_unlock(&hb->chain_lock); 352 353 return qp; 354 } 355 356 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf, 357 struct inet_frags *f, 358 void *arg) 359 { 360 struct inet_frag_queue *q; 361 362 if (!nf->high_thresh || frag_mem_limit(nf) > nf->high_thresh) { 363 inet_frag_schedule_worker(f); 364 return NULL; 365 } 366 367 q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC); 368 if (!q) 369 return NULL; 370 371 q->net = nf; 372 f->constructor(q, arg); 373 add_frag_mem_limit(nf, f->qsize); 374 375 timer_setup(&q->timer, f->frag_expire, 0); 376 spin_lock_init(&q->lock); 377 refcount_set(&q->refcnt, 1); 378 379 return q; 380 } 381 382 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf, 383 struct inet_frags *f, 384 void *arg) 385 { 386 struct inet_frag_queue *q; 387 388 q = inet_frag_alloc(nf, f, arg); 389 if (!q) 390 return NULL; 391 392 return inet_frag_intern(nf, q, f, arg); 393 } 394 395 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, 396 struct inet_frags *f, void *key, 397 unsigned int hash) 398 { 399 struct inet_frag_bucket *hb; 400 struct inet_frag_queue *q; 401 int depth = 0; 402 403 if (frag_mem_limit(nf) > nf->low_thresh) 404 inet_frag_schedule_worker(f); 405 406 hash &= (INETFRAGS_HASHSZ - 1); 407 hb = &f->hash[hash]; 408 409 spin_lock(&hb->chain_lock); 410 hlist_for_each_entry(q, &hb->chain, list) { 411 if (q->net == nf && f->match(q, key)) { 412 refcount_inc(&q->refcnt); 413 spin_unlock(&hb->chain_lock); 414 return q; 415 } 416 depth++; 417 } 418 spin_unlock(&hb->chain_lock); 419 420 if (depth <= INETFRAGS_MAXDEPTH) 421 return inet_frag_create(nf, f, key); 422 423 if (inet_frag_may_rebuild(f)) { 424 if (!f->rebuild) 425 f->rebuild = true; 426 inet_frag_schedule_worker(f); 427 } 428 429 return ERR_PTR(-ENOBUFS); 430 } 431 EXPORT_SYMBOL(inet_frag_find); 432 433 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q, 434 const char *prefix) 435 { 436 static const char msg[] = "inet_frag_find: Fragment hash bucket" 437 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH) 438 ". Dropping fragment.\n"; 439 440 if (PTR_ERR(q) == -ENOBUFS) 441 net_dbg_ratelimited("%s%s", prefix, msg); 442 } 443 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow); 444