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