1 /* Copyright (C) 2013-2014 B.A.T.M.A.N. contributors: 2 * 3 * Martin Hundebøll <martin@hundeboll.net> 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of version 2 of the GNU General Public 7 * License as published by the Free Software Foundation. 8 * 9 * This program is distributed in the hope that it will be useful, but 10 * WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 * General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, see <http://www.gnu.org/licenses/>. 16 */ 17 18 #include "main.h" 19 #include "fragmentation.h" 20 #include "send.h" 21 #include "originator.h" 22 #include "routing.h" 23 #include "hard-interface.h" 24 #include "soft-interface.h" 25 26 27 /** 28 * batadv_frag_clear_chain - delete entries in the fragment buffer chain 29 * @head: head of chain with entries. 30 * 31 * Free fragments in the passed hlist. Should be called with appropriate lock. 32 */ 33 static void batadv_frag_clear_chain(struct hlist_head *head) 34 { 35 struct batadv_frag_list_entry *entry; 36 struct hlist_node *node; 37 38 hlist_for_each_entry_safe(entry, node, head, list) { 39 hlist_del(&entry->list); 40 kfree_skb(entry->skb); 41 kfree(entry); 42 } 43 } 44 45 /** 46 * batadv_frag_purge_orig - free fragments associated to an orig 47 * @orig_node: originator to free fragments from 48 * @check_cb: optional function to tell if an entry should be purged 49 */ 50 void batadv_frag_purge_orig(struct batadv_orig_node *orig_node, 51 bool (*check_cb)(struct batadv_frag_table_entry *)) 52 { 53 struct batadv_frag_table_entry *chain; 54 uint8_t i; 55 56 for (i = 0; i < BATADV_FRAG_BUFFER_COUNT; i++) { 57 chain = &orig_node->fragments[i]; 58 spin_lock_bh(&orig_node->fragments[i].lock); 59 60 if (!check_cb || check_cb(chain)) { 61 batadv_frag_clear_chain(&orig_node->fragments[i].head); 62 orig_node->fragments[i].size = 0; 63 } 64 65 spin_unlock_bh(&orig_node->fragments[i].lock); 66 } 67 } 68 69 /** 70 * batadv_frag_size_limit - maximum possible size of packet to be fragmented 71 * 72 * Returns the maximum size of payload that can be fragmented. 73 */ 74 static int batadv_frag_size_limit(void) 75 { 76 int limit = BATADV_FRAG_MAX_FRAG_SIZE; 77 78 limit -= sizeof(struct batadv_frag_packet); 79 limit *= BATADV_FRAG_MAX_FRAGMENTS; 80 81 return limit; 82 } 83 84 /** 85 * batadv_frag_init_chain - check and prepare fragment chain for new fragment 86 * @chain: chain in fragments table to init 87 * @seqno: sequence number of the received fragment 88 * 89 * Make chain ready for a fragment with sequence number "seqno". Delete existing 90 * entries if they have an "old" sequence number. 91 * 92 * Caller must hold chain->lock. 93 * 94 * Returns true if chain is empty and caller can just insert the new fragment 95 * without searching for the right position. 96 */ 97 static bool batadv_frag_init_chain(struct batadv_frag_table_entry *chain, 98 uint16_t seqno) 99 { 100 if (chain->seqno == seqno) 101 return false; 102 103 if (!hlist_empty(&chain->head)) 104 batadv_frag_clear_chain(&chain->head); 105 106 chain->size = 0; 107 chain->seqno = seqno; 108 109 return true; 110 } 111 112 /** 113 * batadv_frag_insert_packet - insert a fragment into a fragment chain 114 * @orig_node: originator that the fragment was received from 115 * @skb: skb to insert 116 * @chain_out: list head to attach complete chains of fragments to 117 * 118 * Insert a new fragment into the reverse ordered chain in the right table 119 * entry. The hash table entry is cleared if "old" fragments exist in it. 120 * 121 * Returns true if skb is buffered, false on error. If the chain has all the 122 * fragments needed to merge the packet, the chain is moved to the passed head 123 * to avoid locking the chain in the table. 124 */ 125 static bool batadv_frag_insert_packet(struct batadv_orig_node *orig_node, 126 struct sk_buff *skb, 127 struct hlist_head *chain_out) 128 { 129 struct batadv_frag_table_entry *chain; 130 struct batadv_frag_list_entry *frag_entry_new = NULL, *frag_entry_curr; 131 struct batadv_frag_packet *frag_packet; 132 uint8_t bucket; 133 uint16_t seqno, hdr_size = sizeof(struct batadv_frag_packet); 134 bool ret = false; 135 136 /* Linearize packet to avoid linearizing 16 packets in a row when doing 137 * the later merge. Non-linear merge should be added to remove this 138 * linearization. 139 */ 140 if (skb_linearize(skb) < 0) 141 goto err; 142 143 frag_packet = (struct batadv_frag_packet *)skb->data; 144 seqno = ntohs(frag_packet->seqno); 145 bucket = seqno % BATADV_FRAG_BUFFER_COUNT; 146 147 frag_entry_new = kmalloc(sizeof(*frag_entry_new), GFP_ATOMIC); 148 if (!frag_entry_new) 149 goto err; 150 151 frag_entry_new->skb = skb; 152 frag_entry_new->no = frag_packet->no; 153 154 /* Select entry in the "chain table" and delete any prior fragments 155 * with another sequence number. batadv_frag_init_chain() returns true, 156 * if the list is empty at return. 157 */ 158 chain = &orig_node->fragments[bucket]; 159 spin_lock_bh(&chain->lock); 160 if (batadv_frag_init_chain(chain, seqno)) { 161 hlist_add_head(&frag_entry_new->list, &chain->head); 162 chain->size = skb->len - hdr_size; 163 chain->timestamp = jiffies; 164 ret = true; 165 goto out; 166 } 167 168 /* Find the position for the new fragment. */ 169 hlist_for_each_entry(frag_entry_curr, &chain->head, list) { 170 /* Drop packet if fragment already exists. */ 171 if (frag_entry_curr->no == frag_entry_new->no) 172 goto err_unlock; 173 174 /* Order fragments from highest to lowest. */ 175 if (frag_entry_curr->no < frag_entry_new->no) { 176 hlist_add_before(&frag_entry_new->list, 177 &frag_entry_curr->list); 178 chain->size += skb->len - hdr_size; 179 chain->timestamp = jiffies; 180 ret = true; 181 goto out; 182 } 183 } 184 185 /* Reached the end of the list, so insert after 'frag_entry_curr'. */ 186 if (likely(frag_entry_curr)) { 187 hlist_add_after(&frag_entry_curr->list, &frag_entry_new->list); 188 chain->size += skb->len - hdr_size; 189 chain->timestamp = jiffies; 190 ret = true; 191 } 192 193 out: 194 if (chain->size > batadv_frag_size_limit() || 195 ntohs(frag_packet->total_size) > batadv_frag_size_limit()) { 196 /* Clear chain if total size of either the list or the packet 197 * exceeds the maximum size of one merged packet. 198 */ 199 batadv_frag_clear_chain(&chain->head); 200 chain->size = 0; 201 } else if (ntohs(frag_packet->total_size) == chain->size) { 202 /* All fragments received. Hand over chain to caller. */ 203 hlist_move_list(&chain->head, chain_out); 204 chain->size = 0; 205 } 206 207 err_unlock: 208 spin_unlock_bh(&chain->lock); 209 210 err: 211 if (!ret) 212 kfree(frag_entry_new); 213 214 return ret; 215 } 216 217 /** 218 * batadv_frag_merge_packets - merge a chain of fragments 219 * @chain: head of chain with fragments 220 * @skb: packet with total size of skb after merging 221 * 222 * Expand the first skb in the chain and copy the content of the remaining 223 * skb's into the expanded one. After doing so, clear the chain. 224 * 225 * Returns the merged skb or NULL on error. 226 */ 227 static struct sk_buff * 228 batadv_frag_merge_packets(struct hlist_head *chain, struct sk_buff *skb) 229 { 230 struct batadv_frag_packet *packet; 231 struct batadv_frag_list_entry *entry; 232 struct sk_buff *skb_out = NULL; 233 int size, hdr_size = sizeof(struct batadv_frag_packet); 234 235 /* Make sure incoming skb has non-bogus data. */ 236 packet = (struct batadv_frag_packet *)skb->data; 237 size = ntohs(packet->total_size); 238 if (size > batadv_frag_size_limit()) 239 goto free; 240 241 /* Remove first entry, as this is the destination for the rest of the 242 * fragments. 243 */ 244 entry = hlist_entry(chain->first, struct batadv_frag_list_entry, list); 245 hlist_del(&entry->list); 246 skb_out = entry->skb; 247 kfree(entry); 248 249 /* Make room for the rest of the fragments. */ 250 if (pskb_expand_head(skb_out, 0, size - skb->len, GFP_ATOMIC) < 0) { 251 kfree_skb(skb_out); 252 skb_out = NULL; 253 goto free; 254 } 255 256 /* Move the existing MAC header to just before the payload. (Override 257 * the fragment header.) 258 */ 259 skb_pull_rcsum(skb_out, hdr_size); 260 memmove(skb_out->data - ETH_HLEN, skb_mac_header(skb_out), ETH_HLEN); 261 skb_set_mac_header(skb_out, -ETH_HLEN); 262 skb_reset_network_header(skb_out); 263 skb_reset_transport_header(skb_out); 264 265 /* Copy the payload of the each fragment into the last skb */ 266 hlist_for_each_entry(entry, chain, list) { 267 size = entry->skb->len - hdr_size; 268 memcpy(skb_put(skb_out, size), entry->skb->data + hdr_size, 269 size); 270 } 271 272 free: 273 /* Locking is not needed, because 'chain' is not part of any orig. */ 274 batadv_frag_clear_chain(chain); 275 return skb_out; 276 } 277 278 /** 279 * batadv_frag_skb_buffer - buffer fragment for later merge 280 * @skb: skb to buffer 281 * @orig_node_src: originator that the skb is received from 282 * 283 * Add fragment to buffer and merge fragments if possible. 284 * 285 * There are three possible outcomes: 1) Packet is merged: Return true and 286 * set *skb to merged packet; 2) Packet is buffered: Return true and set *skb 287 * to NULL; 3) Error: Return false and leave skb as is. 288 */ 289 bool batadv_frag_skb_buffer(struct sk_buff **skb, 290 struct batadv_orig_node *orig_node_src) 291 { 292 struct sk_buff *skb_out = NULL; 293 struct hlist_head head = HLIST_HEAD_INIT; 294 bool ret = false; 295 296 /* Add packet to buffer and table entry if merge is possible. */ 297 if (!batadv_frag_insert_packet(orig_node_src, *skb, &head)) 298 goto out_err; 299 300 /* Leave if more fragments are needed to merge. */ 301 if (hlist_empty(&head)) 302 goto out; 303 304 skb_out = batadv_frag_merge_packets(&head, *skb); 305 if (!skb_out) 306 goto out_err; 307 308 out: 309 *skb = skb_out; 310 ret = true; 311 out_err: 312 return ret; 313 } 314 315 /** 316 * batadv_frag_skb_fwd - forward fragments that would exceed MTU when merged 317 * @skb: skb to forward 318 * @recv_if: interface that the skb is received on 319 * @orig_node_src: originator that the skb is received from 320 * 321 * Look up the next-hop of the fragments payload and check if the merged packet 322 * will exceed the MTU towards the next-hop. If so, the fragment is forwarded 323 * without merging it. 324 * 325 * Returns true if the fragment is consumed/forwarded, false otherwise. 326 */ 327 bool batadv_frag_skb_fwd(struct sk_buff *skb, 328 struct batadv_hard_iface *recv_if, 329 struct batadv_orig_node *orig_node_src) 330 { 331 struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface); 332 struct batadv_orig_node *orig_node_dst = NULL; 333 struct batadv_neigh_node *neigh_node = NULL; 334 struct batadv_frag_packet *packet; 335 uint16_t total_size; 336 bool ret = false; 337 338 packet = (struct batadv_frag_packet *)skb->data; 339 orig_node_dst = batadv_orig_hash_find(bat_priv, packet->dest); 340 if (!orig_node_dst) 341 goto out; 342 343 neigh_node = batadv_find_router(bat_priv, orig_node_dst, recv_if); 344 if (!neigh_node) 345 goto out; 346 347 /* Forward the fragment, if the merged packet would be too big to 348 * be assembled. 349 */ 350 total_size = ntohs(packet->total_size); 351 if (total_size > neigh_node->if_incoming->net_dev->mtu) { 352 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_FWD); 353 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_FWD_BYTES, 354 skb->len + ETH_HLEN); 355 356 packet->ttl--; 357 batadv_send_skb_packet(skb, neigh_node->if_incoming, 358 neigh_node->addr); 359 ret = true; 360 } 361 362 out: 363 if (orig_node_dst) 364 batadv_orig_node_free_ref(orig_node_dst); 365 if (neigh_node) 366 batadv_neigh_node_free_ref(neigh_node); 367 return ret; 368 } 369 370 /** 371 * batadv_frag_create - create a fragment from skb 372 * @skb: skb to create fragment from 373 * @frag_head: header to use in new fragment 374 * @mtu: size of new fragment 375 * 376 * Split the passed skb into two fragments: A new one with size matching the 377 * passed mtu and the old one with the rest. The new skb contains data from the 378 * tail of the old skb. 379 * 380 * Returns the new fragment, NULL on error. 381 */ 382 static struct sk_buff *batadv_frag_create(struct sk_buff *skb, 383 struct batadv_frag_packet *frag_head, 384 unsigned int mtu) 385 { 386 struct sk_buff *skb_fragment; 387 unsigned header_size = sizeof(*frag_head); 388 unsigned fragment_size = mtu - header_size; 389 390 skb_fragment = netdev_alloc_skb(NULL, mtu + ETH_HLEN); 391 if (!skb_fragment) 392 goto err; 393 394 skb->priority = TC_PRIO_CONTROL; 395 396 /* Eat the last mtu-bytes of the skb */ 397 skb_reserve(skb_fragment, header_size + ETH_HLEN); 398 skb_split(skb, skb_fragment, skb->len - fragment_size); 399 400 /* Add the header */ 401 skb_push(skb_fragment, header_size); 402 memcpy(skb_fragment->data, frag_head, header_size); 403 404 err: 405 return skb_fragment; 406 } 407 408 /** 409 * batadv_frag_send_packet - create up to 16 fragments from the passed skb 410 * @skb: skb to create fragments from 411 * @orig_node: final destination of the created fragments 412 * @neigh_node: next-hop of the created fragments 413 * 414 * Returns true on success, false otherwise. 415 */ 416 bool batadv_frag_send_packet(struct sk_buff *skb, 417 struct batadv_orig_node *orig_node, 418 struct batadv_neigh_node *neigh_node) 419 { 420 struct batadv_priv *bat_priv; 421 struct batadv_hard_iface *primary_if; 422 struct batadv_frag_packet frag_header; 423 struct sk_buff *skb_fragment; 424 unsigned mtu = neigh_node->if_incoming->net_dev->mtu; 425 unsigned header_size = sizeof(frag_header); 426 unsigned max_fragment_size, max_packet_size; 427 428 /* To avoid merge and refragmentation at next-hops we never send 429 * fragments larger than BATADV_FRAG_MAX_FRAG_SIZE 430 */ 431 mtu = min_t(unsigned, mtu, BATADV_FRAG_MAX_FRAG_SIZE); 432 max_fragment_size = (mtu - header_size - ETH_HLEN); 433 max_packet_size = max_fragment_size * BATADV_FRAG_MAX_FRAGMENTS; 434 435 /* Don't even try to fragment, if we need more than 16 fragments */ 436 if (skb->len > max_packet_size) 437 goto out_err; 438 439 bat_priv = orig_node->bat_priv; 440 primary_if = batadv_primary_if_get_selected(bat_priv); 441 if (!primary_if) 442 goto out_err; 443 444 /* Create one header to be copied to all fragments */ 445 frag_header.packet_type = BATADV_UNICAST_FRAG; 446 frag_header.version = BATADV_COMPAT_VERSION; 447 frag_header.ttl = BATADV_TTL; 448 frag_header.seqno = htons(atomic_inc_return(&bat_priv->frag_seqno)); 449 frag_header.reserved = 0; 450 frag_header.no = 0; 451 frag_header.total_size = htons(skb->len); 452 ether_addr_copy(frag_header.orig, primary_if->net_dev->dev_addr); 453 ether_addr_copy(frag_header.dest, orig_node->orig); 454 455 /* Eat and send fragments from the tail of skb */ 456 while (skb->len > max_fragment_size) { 457 skb_fragment = batadv_frag_create(skb, &frag_header, mtu); 458 if (!skb_fragment) 459 goto out_err; 460 461 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX); 462 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES, 463 skb_fragment->len + ETH_HLEN); 464 batadv_send_skb_packet(skb_fragment, neigh_node->if_incoming, 465 neigh_node->addr); 466 frag_header.no++; 467 468 /* The initial check in this function should cover this case */ 469 if (frag_header.no == BATADV_FRAG_MAX_FRAGMENTS - 1) 470 goto out_err; 471 } 472 473 /* Make room for the fragment header. */ 474 if (batadv_skb_head_push(skb, header_size) < 0 || 475 pskb_expand_head(skb, header_size + ETH_HLEN, 0, GFP_ATOMIC) < 0) 476 goto out_err; 477 478 memcpy(skb->data, &frag_header, header_size); 479 480 /* Send the last fragment */ 481 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX); 482 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES, 483 skb->len + ETH_HLEN); 484 batadv_send_skb_packet(skb, neigh_node->if_incoming, neigh_node->addr); 485 486 return true; 487 out_err: 488 return false; 489 } 490