1 /* Copyright (C) 2013-2015 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/etherdevice.h> 24 #include <linux/fs.h> 25 #include <linux/if_ether.h> 26 #include <linux/jiffies.h> 27 #include <linux/kernel.h> 28 #include <linux/lockdep.h> 29 #include <linux/netdevice.h> 30 #include <linux/pkt_sched.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 * 47 * Free fragments in the passed hlist. Should be called with appropriate lock. 48 */ 49 static void batadv_frag_clear_chain(struct hlist_head *head) 50 { 51 struct batadv_frag_list_entry *entry; 52 struct hlist_node *node; 53 54 hlist_for_each_entry_safe(entry, node, head, list) { 55 hlist_del(&entry->list); 56 kfree_skb(entry->skb); 57 kfree(entry); 58 } 59 } 60 61 /** 62 * batadv_frag_purge_orig - free fragments associated to an orig 63 * @orig_node: originator to free fragments from 64 * @check_cb: optional function to tell if an entry should be purged 65 */ 66 void batadv_frag_purge_orig(struct batadv_orig_node *orig_node, 67 bool (*check_cb)(struct batadv_frag_table_entry *)) 68 { 69 struct batadv_frag_table_entry *chain; 70 u8 i; 71 72 for (i = 0; i < BATADV_FRAG_BUFFER_COUNT; i++) { 73 chain = &orig_node->fragments[i]; 74 spin_lock_bh(&orig_node->fragments[i].lock); 75 76 if (!check_cb || check_cb(chain)) { 77 batadv_frag_clear_chain(&orig_node->fragments[i].head); 78 orig_node->fragments[i].size = 0; 79 } 80 81 spin_unlock_bh(&orig_node->fragments[i].lock); 82 } 83 } 84 85 /** 86 * batadv_frag_size_limit - maximum possible size of packet to be fragmented 87 * 88 * Returns the maximum size of payload that can be fragmented. 89 */ 90 static int batadv_frag_size_limit(void) 91 { 92 int limit = BATADV_FRAG_MAX_FRAG_SIZE; 93 94 limit -= sizeof(struct batadv_frag_packet); 95 limit *= BATADV_FRAG_MAX_FRAGMENTS; 96 97 return limit; 98 } 99 100 /** 101 * batadv_frag_init_chain - check and prepare fragment chain for new fragment 102 * @chain: chain in fragments table to init 103 * @seqno: sequence number of the received fragment 104 * 105 * Make chain ready for a fragment with sequence number "seqno". Delete existing 106 * entries if they have an "old" sequence number. 107 * 108 * Caller must hold chain->lock. 109 * 110 * Returns true if chain is empty and caller can just insert the new fragment 111 * without searching for the right position. 112 */ 113 static bool batadv_frag_init_chain(struct batadv_frag_table_entry *chain, 114 u16 seqno) 115 { 116 lockdep_assert_held(&chain->lock); 117 118 if (chain->seqno == seqno) 119 return false; 120 121 if (!hlist_empty(&chain->head)) 122 batadv_frag_clear_chain(&chain->head); 123 124 chain->size = 0; 125 chain->seqno = seqno; 126 127 return true; 128 } 129 130 /** 131 * batadv_frag_insert_packet - insert a fragment into a fragment chain 132 * @orig_node: originator that the fragment was received from 133 * @skb: skb to insert 134 * @chain_out: list head to attach complete chains of fragments to 135 * 136 * Insert a new fragment into the reverse ordered chain in the right table 137 * entry. The hash table entry is cleared if "old" fragments exist in it. 138 * 139 * Returns true if skb is buffered, false on error. If the chain has all the 140 * fragments needed to merge the packet, the chain is moved to the passed head 141 * to avoid locking the chain in the table. 142 */ 143 static bool batadv_frag_insert_packet(struct batadv_orig_node *orig_node, 144 struct sk_buff *skb, 145 struct hlist_head *chain_out) 146 { 147 struct batadv_frag_table_entry *chain; 148 struct batadv_frag_list_entry *frag_entry_new = NULL, *frag_entry_curr; 149 struct batadv_frag_list_entry *frag_entry_last = NULL; 150 struct batadv_frag_packet *frag_packet; 151 u8 bucket; 152 u16 seqno, hdr_size = sizeof(struct batadv_frag_packet); 153 bool ret = false; 154 155 /* Linearize packet to avoid linearizing 16 packets in a row when doing 156 * the later merge. Non-linear merge should be added to remove this 157 * linearization. 158 */ 159 if (skb_linearize(skb) < 0) 160 goto err; 161 162 frag_packet = (struct batadv_frag_packet *)skb->data; 163 seqno = ntohs(frag_packet->seqno); 164 bucket = seqno % BATADV_FRAG_BUFFER_COUNT; 165 166 frag_entry_new = kmalloc(sizeof(*frag_entry_new), GFP_ATOMIC); 167 if (!frag_entry_new) 168 goto err; 169 170 frag_entry_new->skb = skb; 171 frag_entry_new->no = frag_packet->no; 172 173 /* Select entry in the "chain table" and delete any prior fragments 174 * with another sequence number. batadv_frag_init_chain() returns true, 175 * if the list is empty at return. 176 */ 177 chain = &orig_node->fragments[bucket]; 178 spin_lock_bh(&chain->lock); 179 if (batadv_frag_init_chain(chain, seqno)) { 180 hlist_add_head(&frag_entry_new->list, &chain->head); 181 chain->size = skb->len - hdr_size; 182 chain->timestamp = jiffies; 183 chain->total_size = ntohs(frag_packet->total_size); 184 ret = true; 185 goto out; 186 } 187 188 /* Find the position for the new fragment. */ 189 hlist_for_each_entry(frag_entry_curr, &chain->head, list) { 190 /* Drop packet if fragment already exists. */ 191 if (frag_entry_curr->no == frag_entry_new->no) 192 goto err_unlock; 193 194 /* Order fragments from highest to lowest. */ 195 if (frag_entry_curr->no < frag_entry_new->no) { 196 hlist_add_before(&frag_entry_new->list, 197 &frag_entry_curr->list); 198 chain->size += skb->len - hdr_size; 199 chain->timestamp = jiffies; 200 ret = true; 201 goto out; 202 } 203 204 /* store current entry because it could be the last in list */ 205 frag_entry_last = frag_entry_curr; 206 } 207 208 /* Reached the end of the list, so insert after 'frag_entry_last'. */ 209 if (likely(frag_entry_last)) { 210 hlist_add_behind(&frag_entry_new->list, &frag_entry_last->list); 211 chain->size += skb->len - hdr_size; 212 chain->timestamp = jiffies; 213 ret = true; 214 } 215 216 out: 217 if (chain->size > batadv_frag_size_limit() || 218 chain->total_size != ntohs(frag_packet->total_size) || 219 chain->total_size > batadv_frag_size_limit()) { 220 /* Clear chain if total size of either the list or the packet 221 * exceeds the maximum size of one merged packet. Don't allow 222 * packets to have different total_size. 223 */ 224 batadv_frag_clear_chain(&chain->head); 225 chain->size = 0; 226 } else if (ntohs(frag_packet->total_size) == chain->size) { 227 /* All fragments received. Hand over chain to caller. */ 228 hlist_move_list(&chain->head, chain_out); 229 chain->size = 0; 230 } 231 232 err_unlock: 233 spin_unlock_bh(&chain->lock); 234 235 err: 236 if (!ret) 237 kfree(frag_entry_new); 238 239 return ret; 240 } 241 242 /** 243 * batadv_frag_merge_packets - merge a chain of fragments 244 * @chain: head of chain with fragments 245 * @skb: packet with total size of skb after merging 246 * 247 * Expand the first skb in the chain and copy the content of the remaining 248 * skb's into the expanded one. After doing so, clear the chain. 249 * 250 * Returns the merged skb or NULL on error. 251 */ 252 static struct sk_buff * 253 batadv_frag_merge_packets(struct hlist_head *chain) 254 { 255 struct batadv_frag_packet *packet; 256 struct batadv_frag_list_entry *entry; 257 struct sk_buff *skb_out = NULL; 258 int size, hdr_size = sizeof(struct batadv_frag_packet); 259 260 /* Remove first entry, as this is the destination for the rest of the 261 * fragments. 262 */ 263 entry = hlist_entry(chain->first, struct batadv_frag_list_entry, list); 264 hlist_del(&entry->list); 265 skb_out = entry->skb; 266 kfree(entry); 267 268 packet = (struct batadv_frag_packet *)skb_out->data; 269 size = ntohs(packet->total_size); 270 271 /* Make room for the rest of the fragments. */ 272 if (pskb_expand_head(skb_out, 0, size - skb_out->len, GFP_ATOMIC) < 0) { 273 kfree_skb(skb_out); 274 skb_out = NULL; 275 goto free; 276 } 277 278 /* Move the existing MAC header to just before the payload. (Override 279 * the fragment header.) 280 */ 281 skb_pull_rcsum(skb_out, hdr_size); 282 memmove(skb_out->data - ETH_HLEN, skb_mac_header(skb_out), ETH_HLEN); 283 skb_set_mac_header(skb_out, -ETH_HLEN); 284 skb_reset_network_header(skb_out); 285 skb_reset_transport_header(skb_out); 286 287 /* Copy the payload of the each fragment into the last skb */ 288 hlist_for_each_entry(entry, chain, list) { 289 size = entry->skb->len - hdr_size; 290 memcpy(skb_put(skb_out, size), entry->skb->data + hdr_size, 291 size); 292 } 293 294 free: 295 /* Locking is not needed, because 'chain' is not part of any orig. */ 296 batadv_frag_clear_chain(chain); 297 return skb_out; 298 } 299 300 /** 301 * batadv_frag_skb_buffer - buffer fragment for later merge 302 * @skb: skb to buffer 303 * @orig_node_src: originator that the skb is received from 304 * 305 * Add fragment to buffer and merge fragments if possible. 306 * 307 * There are three possible outcomes: 1) Packet is merged: Return true and 308 * set *skb to merged packet; 2) Packet is buffered: Return true and set *skb 309 * to NULL; 3) Error: Return false and leave skb as is. 310 */ 311 bool batadv_frag_skb_buffer(struct sk_buff **skb, 312 struct batadv_orig_node *orig_node_src) 313 { 314 struct sk_buff *skb_out = NULL; 315 struct hlist_head head = HLIST_HEAD_INIT; 316 bool ret = false; 317 318 /* Add packet to buffer and table entry if merge is possible. */ 319 if (!batadv_frag_insert_packet(orig_node_src, *skb, &head)) 320 goto out_err; 321 322 /* Leave if more fragments are needed to merge. */ 323 if (hlist_empty(&head)) 324 goto out; 325 326 skb_out = batadv_frag_merge_packets(&head); 327 if (!skb_out) 328 goto out_err; 329 330 out: 331 *skb = skb_out; 332 ret = true; 333 out_err: 334 return ret; 335 } 336 337 /** 338 * batadv_frag_skb_fwd - forward fragments that would exceed MTU when merged 339 * @skb: skb to forward 340 * @recv_if: interface that the skb is received on 341 * @orig_node_src: originator that the skb is received from 342 * 343 * Look up the next-hop of the fragments payload and check if the merged packet 344 * will exceed the MTU towards the next-hop. If so, the fragment is forwarded 345 * without merging it. 346 * 347 * Returns true if the fragment is consumed/forwarded, false otherwise. 348 */ 349 bool batadv_frag_skb_fwd(struct sk_buff *skb, 350 struct batadv_hard_iface *recv_if, 351 struct batadv_orig_node *orig_node_src) 352 { 353 struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface); 354 struct batadv_orig_node *orig_node_dst = NULL; 355 struct batadv_neigh_node *neigh_node = NULL; 356 struct batadv_frag_packet *packet; 357 u16 total_size; 358 bool ret = false; 359 360 packet = (struct batadv_frag_packet *)skb->data; 361 orig_node_dst = batadv_orig_hash_find(bat_priv, packet->dest); 362 if (!orig_node_dst) 363 goto out; 364 365 neigh_node = batadv_find_router(bat_priv, orig_node_dst, recv_if); 366 if (!neigh_node) 367 goto out; 368 369 /* Forward the fragment, if the merged packet would be too big to 370 * be assembled. 371 */ 372 total_size = ntohs(packet->total_size); 373 if (total_size > neigh_node->if_incoming->net_dev->mtu) { 374 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_FWD); 375 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_FWD_BYTES, 376 skb->len + ETH_HLEN); 377 378 packet->ttl--; 379 batadv_send_skb_packet(skb, neigh_node->if_incoming, 380 neigh_node->addr); 381 ret = true; 382 } 383 384 out: 385 if (orig_node_dst) 386 batadv_orig_node_free_ref(orig_node_dst); 387 if (neigh_node) 388 batadv_neigh_node_free_ref(neigh_node); 389 return ret; 390 } 391 392 /** 393 * batadv_frag_create - create a fragment from skb 394 * @skb: skb to create fragment from 395 * @frag_head: header to use in new fragment 396 * @mtu: size of new fragment 397 * 398 * Split the passed skb into two fragments: A new one with size matching the 399 * passed mtu and the old one with the rest. The new skb contains data from the 400 * tail of the old skb. 401 * 402 * Returns the new fragment, NULL on error. 403 */ 404 static struct sk_buff *batadv_frag_create(struct sk_buff *skb, 405 struct batadv_frag_packet *frag_head, 406 unsigned int mtu) 407 { 408 struct sk_buff *skb_fragment; 409 unsigned header_size = sizeof(*frag_head); 410 unsigned fragment_size = mtu - header_size; 411 412 skb_fragment = netdev_alloc_skb(NULL, mtu + ETH_HLEN); 413 if (!skb_fragment) 414 goto err; 415 416 skb->priority = TC_PRIO_CONTROL; 417 418 /* Eat the last mtu-bytes of the skb */ 419 skb_reserve(skb_fragment, header_size + ETH_HLEN); 420 skb_split(skb, skb_fragment, skb->len - fragment_size); 421 422 /* Add the header */ 423 skb_push(skb_fragment, header_size); 424 memcpy(skb_fragment->data, frag_head, header_size); 425 426 err: 427 return skb_fragment; 428 } 429 430 /** 431 * batadv_frag_send_packet - create up to 16 fragments from the passed skb 432 * @skb: skb to create fragments from 433 * @orig_node: final destination of the created fragments 434 * @neigh_node: next-hop of the created fragments 435 * 436 * Returns true on success, false otherwise. 437 */ 438 bool batadv_frag_send_packet(struct sk_buff *skb, 439 struct batadv_orig_node *orig_node, 440 struct batadv_neigh_node *neigh_node) 441 { 442 struct batadv_priv *bat_priv; 443 struct batadv_hard_iface *primary_if = NULL; 444 struct batadv_frag_packet frag_header; 445 struct sk_buff *skb_fragment; 446 unsigned mtu = neigh_node->if_incoming->net_dev->mtu; 447 unsigned header_size = sizeof(frag_header); 448 unsigned max_fragment_size, max_packet_size; 449 bool ret = false; 450 451 /* To avoid merge and refragmentation at next-hops we never send 452 * fragments larger than BATADV_FRAG_MAX_FRAG_SIZE 453 */ 454 mtu = min_t(unsigned, mtu, BATADV_FRAG_MAX_FRAG_SIZE); 455 max_fragment_size = mtu - header_size; 456 max_packet_size = max_fragment_size * BATADV_FRAG_MAX_FRAGMENTS; 457 458 /* Don't even try to fragment, if we need more than 16 fragments */ 459 if (skb->len > max_packet_size) 460 goto out_err; 461 462 bat_priv = orig_node->bat_priv; 463 primary_if = batadv_primary_if_get_selected(bat_priv); 464 if (!primary_if) 465 goto out_err; 466 467 /* Create one header to be copied to all fragments */ 468 frag_header.packet_type = BATADV_UNICAST_FRAG; 469 frag_header.version = BATADV_COMPAT_VERSION; 470 frag_header.ttl = BATADV_TTL; 471 frag_header.seqno = htons(atomic_inc_return(&bat_priv->frag_seqno)); 472 frag_header.reserved = 0; 473 frag_header.no = 0; 474 frag_header.total_size = htons(skb->len); 475 ether_addr_copy(frag_header.orig, primary_if->net_dev->dev_addr); 476 ether_addr_copy(frag_header.dest, orig_node->orig); 477 478 /* Eat and send fragments from the tail of skb */ 479 while (skb->len > max_fragment_size) { 480 skb_fragment = batadv_frag_create(skb, &frag_header, mtu); 481 if (!skb_fragment) 482 goto out_err; 483 484 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX); 485 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES, 486 skb_fragment->len + ETH_HLEN); 487 batadv_send_skb_packet(skb_fragment, neigh_node->if_incoming, 488 neigh_node->addr); 489 frag_header.no++; 490 491 /* The initial check in this function should cover this case */ 492 if (frag_header.no == BATADV_FRAG_MAX_FRAGMENTS - 1) 493 goto out_err; 494 } 495 496 /* Make room for the fragment header. */ 497 if (batadv_skb_head_push(skb, header_size) < 0 || 498 pskb_expand_head(skb, header_size + ETH_HLEN, 0, GFP_ATOMIC) < 0) 499 goto out_err; 500 501 memcpy(skb->data, &frag_header, header_size); 502 503 /* Send the last fragment */ 504 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX); 505 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES, 506 skb->len + ETH_HLEN); 507 batadv_send_skb_packet(skb, neigh_node->if_incoming, neigh_node->addr); 508 509 ret = true; 510 511 out_err: 512 if (primary_if) 513 batadv_hardif_free_ref(primary_if); 514 515 return ret; 516 } 517