1 /* Copyright (C) 2013-2017 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 "fragmentation.h" 19 #include "main.h" 20 21 #include <linux/atomic.h> 22 #include <linux/byteorder/generic.h> 23 #include <linux/errno.h> 24 #include <linux/etherdevice.h> 25 #include <linux/fs.h> 26 #include <linux/if_ether.h> 27 #include <linux/jiffies.h> 28 #include <linux/kernel.h> 29 #include <linux/lockdep.h> 30 #include <linux/netdevice.h> 31 #include <linux/skbuff.h> 32 #include <linux/slab.h> 33 #include <linux/spinlock.h> 34 #include <linux/string.h> 35 36 #include "hard-interface.h" 37 #include "originator.h" 38 #include "packet.h" 39 #include "routing.h" 40 #include "send.h" 41 #include "soft-interface.h" 42 43 /** 44 * batadv_frag_clear_chain - delete entries in the fragment buffer chain 45 * @head: head of chain with entries. 46 * @dropped: whether the chain is cleared because all fragments are dropped 47 * 48 * Free fragments in the passed hlist. Should be called with appropriate lock. 49 */ 50 static void batadv_frag_clear_chain(struct hlist_head *head, bool dropped) 51 { 52 struct batadv_frag_list_entry *entry; 53 struct hlist_node *node; 54 55 hlist_for_each_entry_safe(entry, node, head, list) { 56 hlist_del(&entry->list); 57 58 if (dropped) 59 kfree_skb(entry->skb); 60 else 61 consume_skb(entry->skb); 62 63 kfree(entry); 64 } 65 } 66 67 /** 68 * batadv_frag_purge_orig - free fragments associated to an orig 69 * @orig_node: originator to free fragments from 70 * @check_cb: optional function to tell if an entry should be purged 71 */ 72 void batadv_frag_purge_orig(struct batadv_orig_node *orig_node, 73 bool (*check_cb)(struct batadv_frag_table_entry *)) 74 { 75 struct batadv_frag_table_entry *chain; 76 u8 i; 77 78 for (i = 0; i < BATADV_FRAG_BUFFER_COUNT; i++) { 79 chain = &orig_node->fragments[i]; 80 spin_lock_bh(&chain->lock); 81 82 if (!check_cb || check_cb(chain)) { 83 batadv_frag_clear_chain(&chain->fragment_list, true); 84 chain->size = 0; 85 } 86 87 spin_unlock_bh(&chain->lock); 88 } 89 } 90 91 /** 92 * batadv_frag_size_limit - maximum possible size of packet to be fragmented 93 * 94 * Return: the maximum size of payload that can be fragmented. 95 */ 96 static int batadv_frag_size_limit(void) 97 { 98 int limit = BATADV_FRAG_MAX_FRAG_SIZE; 99 100 limit -= sizeof(struct batadv_frag_packet); 101 limit *= BATADV_FRAG_MAX_FRAGMENTS; 102 103 return limit; 104 } 105 106 /** 107 * batadv_frag_init_chain - check and prepare fragment chain for new fragment 108 * @chain: chain in fragments table to init 109 * @seqno: sequence number of the received fragment 110 * 111 * Make chain ready for a fragment with sequence number "seqno". Delete existing 112 * entries if they have an "old" sequence number. 113 * 114 * Caller must hold chain->lock. 115 * 116 * Return: true if chain is empty and caller can just insert the new fragment 117 * without searching for the right position. 118 */ 119 static bool batadv_frag_init_chain(struct batadv_frag_table_entry *chain, 120 u16 seqno) 121 { 122 lockdep_assert_held(&chain->lock); 123 124 if (chain->seqno == seqno) 125 return false; 126 127 if (!hlist_empty(&chain->fragment_list)) 128 batadv_frag_clear_chain(&chain->fragment_list, true); 129 130 chain->size = 0; 131 chain->seqno = seqno; 132 133 return true; 134 } 135 136 /** 137 * batadv_frag_insert_packet - insert a fragment into a fragment chain 138 * @orig_node: originator that the fragment was received from 139 * @skb: skb to insert 140 * @chain_out: list head to attach complete chains of fragments to 141 * 142 * Insert a new fragment into the reverse ordered chain in the right table 143 * entry. The hash table entry is cleared if "old" fragments exist in it. 144 * 145 * Return: true if skb is buffered, false on error. If the chain has all the 146 * fragments needed to merge the packet, the chain is moved to the passed head 147 * to avoid locking the chain in the table. 148 */ 149 static bool batadv_frag_insert_packet(struct batadv_orig_node *orig_node, 150 struct sk_buff *skb, 151 struct hlist_head *chain_out) 152 { 153 struct batadv_frag_table_entry *chain; 154 struct batadv_frag_list_entry *frag_entry_new = NULL, *frag_entry_curr; 155 struct batadv_frag_list_entry *frag_entry_last = NULL; 156 struct batadv_frag_packet *frag_packet; 157 u8 bucket; 158 u16 seqno, hdr_size = sizeof(struct batadv_frag_packet); 159 bool ret = false; 160 161 /* Linearize packet to avoid linearizing 16 packets in a row when doing 162 * the later merge. Non-linear merge should be added to remove this 163 * linearization. 164 */ 165 if (skb_linearize(skb) < 0) 166 goto err; 167 168 frag_packet = (struct batadv_frag_packet *)skb->data; 169 seqno = ntohs(frag_packet->seqno); 170 bucket = seqno % BATADV_FRAG_BUFFER_COUNT; 171 172 frag_entry_new = kmalloc(sizeof(*frag_entry_new), GFP_ATOMIC); 173 if (!frag_entry_new) 174 goto err; 175 176 frag_entry_new->skb = skb; 177 frag_entry_new->no = frag_packet->no; 178 179 /* Select entry in the "chain table" and delete any prior fragments 180 * with another sequence number. batadv_frag_init_chain() returns true, 181 * if the list is empty at return. 182 */ 183 chain = &orig_node->fragments[bucket]; 184 spin_lock_bh(&chain->lock); 185 if (batadv_frag_init_chain(chain, seqno)) { 186 hlist_add_head(&frag_entry_new->list, &chain->fragment_list); 187 chain->size = skb->len - hdr_size; 188 chain->timestamp = jiffies; 189 chain->total_size = ntohs(frag_packet->total_size); 190 ret = true; 191 goto out; 192 } 193 194 /* Find the position for the new fragment. */ 195 hlist_for_each_entry(frag_entry_curr, &chain->fragment_list, list) { 196 /* Drop packet if fragment already exists. */ 197 if (frag_entry_curr->no == frag_entry_new->no) 198 goto err_unlock; 199 200 /* Order fragments from highest to lowest. */ 201 if (frag_entry_curr->no < frag_entry_new->no) { 202 hlist_add_before(&frag_entry_new->list, 203 &frag_entry_curr->list); 204 chain->size += skb->len - hdr_size; 205 chain->timestamp = jiffies; 206 ret = true; 207 goto out; 208 } 209 210 /* store current entry because it could be the last in list */ 211 frag_entry_last = frag_entry_curr; 212 } 213 214 /* Reached the end of the list, so insert after 'frag_entry_last'. */ 215 if (likely(frag_entry_last)) { 216 hlist_add_behind(&frag_entry_new->list, &frag_entry_last->list); 217 chain->size += skb->len - hdr_size; 218 chain->timestamp = jiffies; 219 ret = true; 220 } 221 222 out: 223 if (chain->size > batadv_frag_size_limit() || 224 chain->total_size != ntohs(frag_packet->total_size) || 225 chain->total_size > batadv_frag_size_limit()) { 226 /* Clear chain if total size of either the list or the packet 227 * exceeds the maximum size of one merged packet. Don't allow 228 * packets to have different total_size. 229 */ 230 batadv_frag_clear_chain(&chain->fragment_list, true); 231 chain->size = 0; 232 } else if (ntohs(frag_packet->total_size) == chain->size) { 233 /* All fragments received. Hand over chain to caller. */ 234 hlist_move_list(&chain->fragment_list, chain_out); 235 chain->size = 0; 236 } 237 238 err_unlock: 239 spin_unlock_bh(&chain->lock); 240 241 err: 242 if (!ret) 243 kfree(frag_entry_new); 244 245 return ret; 246 } 247 248 /** 249 * batadv_frag_merge_packets - merge a chain of fragments 250 * @chain: head of chain with fragments 251 * 252 * Expand the first skb in the chain and copy the content of the remaining 253 * skb's into the expanded one. After doing so, clear the chain. 254 * 255 * Return: the merged skb or NULL on error. 256 */ 257 static struct sk_buff * 258 batadv_frag_merge_packets(struct hlist_head *chain) 259 { 260 struct batadv_frag_packet *packet; 261 struct batadv_frag_list_entry *entry; 262 struct sk_buff *skb_out; 263 int size, hdr_size = sizeof(struct batadv_frag_packet); 264 bool dropped = false; 265 266 /* Remove first entry, as this is the destination for the rest of the 267 * fragments. 268 */ 269 entry = hlist_entry(chain->first, struct batadv_frag_list_entry, list); 270 hlist_del(&entry->list); 271 skb_out = entry->skb; 272 kfree(entry); 273 274 packet = (struct batadv_frag_packet *)skb_out->data; 275 size = ntohs(packet->total_size); 276 277 /* Make room for the rest of the fragments. */ 278 if (pskb_expand_head(skb_out, 0, size - skb_out->len, GFP_ATOMIC) < 0) { 279 kfree_skb(skb_out); 280 skb_out = NULL; 281 dropped = true; 282 goto free; 283 } 284 285 /* Move the existing MAC header to just before the payload. (Override 286 * the fragment header.) 287 */ 288 skb_pull_rcsum(skb_out, hdr_size); 289 memmove(skb_out->data - ETH_HLEN, skb_mac_header(skb_out), ETH_HLEN); 290 skb_set_mac_header(skb_out, -ETH_HLEN); 291 skb_reset_network_header(skb_out); 292 skb_reset_transport_header(skb_out); 293 294 /* Copy the payload of the each fragment into the last skb */ 295 hlist_for_each_entry(entry, chain, list) { 296 size = entry->skb->len - hdr_size; 297 memcpy(skb_put(skb_out, size), entry->skb->data + hdr_size, 298 size); 299 } 300 301 free: 302 /* Locking is not needed, because 'chain' is not part of any orig. */ 303 batadv_frag_clear_chain(chain, dropped); 304 return skb_out; 305 } 306 307 /** 308 * batadv_frag_skb_buffer - buffer fragment for later merge 309 * @skb: skb to buffer 310 * @orig_node_src: originator that the skb is received from 311 * 312 * Add fragment to buffer and merge fragments if possible. 313 * 314 * There are three possible outcomes: 1) Packet is merged: Return true and 315 * set *skb to merged packet; 2) Packet is buffered: Return true and set *skb 316 * to NULL; 3) Error: Return false and leave skb as is. 317 * 318 * Return: true when packet is merged or buffered, false when skb is not not 319 * used. 320 */ 321 bool batadv_frag_skb_buffer(struct sk_buff **skb, 322 struct batadv_orig_node *orig_node_src) 323 { 324 struct sk_buff *skb_out = NULL; 325 struct hlist_head head = HLIST_HEAD_INIT; 326 bool ret = false; 327 328 /* Add packet to buffer and table entry if merge is possible. */ 329 if (!batadv_frag_insert_packet(orig_node_src, *skb, &head)) 330 goto out_err; 331 332 /* Leave if more fragments are needed to merge. */ 333 if (hlist_empty(&head)) 334 goto out; 335 336 skb_out = batadv_frag_merge_packets(&head); 337 if (!skb_out) 338 goto out_err; 339 340 out: 341 *skb = skb_out; 342 ret = true; 343 out_err: 344 return ret; 345 } 346 347 /** 348 * batadv_frag_skb_fwd - forward fragments that would exceed MTU when merged 349 * @skb: skb to forward 350 * @recv_if: interface that the skb is received on 351 * @orig_node_src: originator that the skb is received from 352 * 353 * Look up the next-hop of the fragments payload and check if the merged packet 354 * will exceed the MTU towards the next-hop. If so, the fragment is forwarded 355 * without merging it. 356 * 357 * Return: true if the fragment is consumed/forwarded, false otherwise. 358 */ 359 bool batadv_frag_skb_fwd(struct sk_buff *skb, 360 struct batadv_hard_iface *recv_if, 361 struct batadv_orig_node *orig_node_src) 362 { 363 struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface); 364 struct batadv_orig_node *orig_node_dst; 365 struct batadv_neigh_node *neigh_node = NULL; 366 struct batadv_frag_packet *packet; 367 u16 total_size; 368 bool ret = false; 369 370 packet = (struct batadv_frag_packet *)skb->data; 371 orig_node_dst = batadv_orig_hash_find(bat_priv, packet->dest); 372 if (!orig_node_dst) 373 goto out; 374 375 neigh_node = batadv_find_router(bat_priv, orig_node_dst, recv_if); 376 if (!neigh_node) 377 goto out; 378 379 /* Forward the fragment, if the merged packet would be too big to 380 * be assembled. 381 */ 382 total_size = ntohs(packet->total_size); 383 if (total_size > neigh_node->if_incoming->net_dev->mtu) { 384 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_FWD); 385 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_FWD_BYTES, 386 skb->len + ETH_HLEN); 387 388 packet->ttl--; 389 batadv_send_unicast_skb(skb, neigh_node); 390 ret = true; 391 } 392 393 out: 394 if (orig_node_dst) 395 batadv_orig_node_put(orig_node_dst); 396 if (neigh_node) 397 batadv_neigh_node_put(neigh_node); 398 return ret; 399 } 400 401 /** 402 * batadv_frag_create - create a fragment from skb 403 * @skb: skb to create fragment from 404 * @frag_head: header to use in new fragment 405 * @mtu: size of new fragment 406 * 407 * Split the passed skb into two fragments: A new one with size matching the 408 * passed mtu and the old one with the rest. The new skb contains data from the 409 * tail of the old skb. 410 * 411 * Return: the new fragment, NULL on error. 412 */ 413 static struct sk_buff *batadv_frag_create(struct sk_buff *skb, 414 struct batadv_frag_packet *frag_head, 415 unsigned int mtu) 416 { 417 struct sk_buff *skb_fragment; 418 unsigned int header_size = sizeof(*frag_head); 419 unsigned int fragment_size = mtu - header_size; 420 421 skb_fragment = netdev_alloc_skb(NULL, mtu + ETH_HLEN); 422 if (!skb_fragment) 423 goto err; 424 425 skb_fragment->priority = skb->priority; 426 427 /* Eat the last mtu-bytes of the skb */ 428 skb_reserve(skb_fragment, header_size + ETH_HLEN); 429 skb_split(skb, skb_fragment, skb->len - fragment_size); 430 431 /* Add the header */ 432 skb_push(skb_fragment, header_size); 433 memcpy(skb_fragment->data, frag_head, header_size); 434 435 err: 436 return skb_fragment; 437 } 438 439 /** 440 * batadv_frag_send_packet - create up to 16 fragments from the passed skb 441 * @skb: skb to create fragments from 442 * @orig_node: final destination of the created fragments 443 * @neigh_node: next-hop of the created fragments 444 * 445 * Return: the netdev tx status or a negative errno code on a failure 446 */ 447 int batadv_frag_send_packet(struct sk_buff *skb, 448 struct batadv_orig_node *orig_node, 449 struct batadv_neigh_node *neigh_node) 450 { 451 struct batadv_priv *bat_priv; 452 struct batadv_hard_iface *primary_if = NULL; 453 struct batadv_frag_packet frag_header; 454 struct sk_buff *skb_fragment; 455 unsigned int mtu = neigh_node->if_incoming->net_dev->mtu; 456 unsigned int header_size = sizeof(frag_header); 457 unsigned int max_fragment_size, max_packet_size; 458 int ret; 459 460 /* To avoid merge and refragmentation at next-hops we never send 461 * fragments larger than BATADV_FRAG_MAX_FRAG_SIZE 462 */ 463 mtu = min_t(unsigned int, mtu, BATADV_FRAG_MAX_FRAG_SIZE); 464 max_fragment_size = mtu - header_size; 465 max_packet_size = max_fragment_size * BATADV_FRAG_MAX_FRAGMENTS; 466 467 /* Don't even try to fragment, if we need more than 16 fragments */ 468 if (skb->len > max_packet_size) { 469 ret = -EAGAIN; 470 goto free_skb; 471 } 472 473 bat_priv = orig_node->bat_priv; 474 primary_if = batadv_primary_if_get_selected(bat_priv); 475 if (!primary_if) { 476 ret = -EINVAL; 477 goto free_skb; 478 } 479 480 /* Create one header to be copied to all fragments */ 481 frag_header.packet_type = BATADV_UNICAST_FRAG; 482 frag_header.version = BATADV_COMPAT_VERSION; 483 frag_header.ttl = BATADV_TTL; 484 frag_header.seqno = htons(atomic_inc_return(&bat_priv->frag_seqno)); 485 frag_header.reserved = 0; 486 frag_header.no = 0; 487 frag_header.total_size = htons(skb->len); 488 489 /* skb->priority values from 256->263 are magic values to 490 * directly indicate a specific 802.1d priority. This is used 491 * to allow 802.1d priority to be passed directly in from VLAN 492 * tags, etc. 493 */ 494 if (skb->priority >= 256 && skb->priority <= 263) 495 frag_header.priority = skb->priority - 256; 496 497 ether_addr_copy(frag_header.orig, primary_if->net_dev->dev_addr); 498 ether_addr_copy(frag_header.dest, orig_node->orig); 499 500 /* Eat and send fragments from the tail of skb */ 501 while (skb->len > max_fragment_size) { 502 skb_fragment = batadv_frag_create(skb, &frag_header, mtu); 503 if (!skb_fragment) { 504 ret = -ENOMEM; 505 goto put_primary_if; 506 } 507 508 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX); 509 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES, 510 skb_fragment->len + ETH_HLEN); 511 ret = batadv_send_unicast_skb(skb_fragment, neigh_node); 512 if (ret != NET_XMIT_SUCCESS) { 513 ret = NET_XMIT_DROP; 514 goto put_primary_if; 515 } 516 517 frag_header.no++; 518 519 /* The initial check in this function should cover this case */ 520 if (frag_header.no == BATADV_FRAG_MAX_FRAGMENTS - 1) { 521 ret = -EINVAL; 522 goto put_primary_if; 523 } 524 } 525 526 /* Make room for the fragment header. */ 527 if (batadv_skb_head_push(skb, header_size) < 0 || 528 pskb_expand_head(skb, header_size + ETH_HLEN, 0, GFP_ATOMIC) < 0) { 529 ret = -ENOMEM; 530 goto put_primary_if; 531 } 532 533 memcpy(skb->data, &frag_header, header_size); 534 535 /* Send the last fragment */ 536 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX); 537 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES, 538 skb->len + ETH_HLEN); 539 ret = batadv_send_unicast_skb(skb, neigh_node); 540 /* skb was consumed */ 541 skb = NULL; 542 543 put_primary_if: 544 batadv_hardif_put(primary_if); 545 free_skb: 546 kfree_skb(skb); 547 548 return ret; 549 } 550