1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (C) 2013-2019 B.A.T.M.A.N. contributors:
3 *
4 * Martin Hundebøll <martin@hundeboll.net>
5 */
6
7 #include "fragmentation.h"
8 #include "main.h"
9
10 #include <linux/atomic.h>
11 #include <linux/byteorder/generic.h>
12 #include <linux/errno.h>
13 #include <linux/etherdevice.h>
14 #include <linux/gfp.h>
15 #include <linux/if_ether.h>
16 #include <linux/jiffies.h>
17 #include <linux/kernel.h>
18 #include <linux/lockdep.h>
19 #include <linux/netdevice.h>
20 #include <linux/skbuff.h>
21 #include <linux/slab.h>
22 #include <linux/spinlock.h>
23 #include <linux/string.h>
24 #include <uapi/linux/batadv_packet.h>
25
26 #include "hard-interface.h"
27 #include "originator.h"
28 #include "routing.h"
29 #include "send.h"
30 #include "soft-interface.h"
31
32 /**
33 * batadv_frag_clear_chain() - delete entries in the fragment buffer chain
34 * @head: head of chain with entries.
35 * @dropped: whether the chain is cleared because all fragments are dropped
36 *
37 * Free fragments in the passed hlist. Should be called with appropriate lock.
38 */
batadv_frag_clear_chain(struct hlist_head * head,bool dropped)39 static void batadv_frag_clear_chain(struct hlist_head *head, bool dropped)
40 {
41 struct batadv_frag_list_entry *entry;
42 struct hlist_node *node;
43
44 hlist_for_each_entry_safe(entry, node, head, list) {
45 hlist_del(&entry->list);
46
47 if (dropped)
48 kfree_skb(entry->skb);
49 else
50 consume_skb(entry->skb);
51
52 kfree(entry);
53 }
54 }
55
56 /**
57 * batadv_frag_purge_orig() - free fragments associated to an orig
58 * @orig_node: originator to free fragments from
59 * @check_cb: optional function to tell if an entry should be purged
60 */
batadv_frag_purge_orig(struct batadv_orig_node * orig_node,bool (* check_cb)(struct batadv_frag_table_entry *))61 void batadv_frag_purge_orig(struct batadv_orig_node *orig_node,
62 bool (*check_cb)(struct batadv_frag_table_entry *))
63 {
64 struct batadv_frag_table_entry *chain;
65 u8 i;
66
67 for (i = 0; i < BATADV_FRAG_BUFFER_COUNT; i++) {
68 chain = &orig_node->fragments[i];
69 spin_lock_bh(&chain->lock);
70
71 if (!check_cb || check_cb(chain)) {
72 batadv_frag_clear_chain(&chain->fragment_list, true);
73 chain->size = 0;
74 }
75
76 spin_unlock_bh(&chain->lock);
77 }
78 }
79
80 /**
81 * batadv_frag_size_limit() - maximum possible size of packet to be fragmented
82 *
83 * Return: the maximum size of payload that can be fragmented.
84 */
batadv_frag_size_limit(void)85 static int batadv_frag_size_limit(void)
86 {
87 int limit = BATADV_FRAG_MAX_FRAG_SIZE;
88
89 limit -= sizeof(struct batadv_frag_packet);
90 limit *= BATADV_FRAG_MAX_FRAGMENTS;
91
92 return limit;
93 }
94
95 /**
96 * batadv_frag_init_chain() - check and prepare fragment chain for new fragment
97 * @chain: chain in fragments table to init
98 * @seqno: sequence number of the received fragment
99 *
100 * Make chain ready for a fragment with sequence number "seqno". Delete existing
101 * entries if they have an "old" sequence number.
102 *
103 * Caller must hold chain->lock.
104 *
105 * Return: true if chain is empty and caller can just insert the new fragment
106 * without searching for the right position.
107 */
batadv_frag_init_chain(struct batadv_frag_table_entry * chain,u16 seqno)108 static bool batadv_frag_init_chain(struct batadv_frag_table_entry *chain,
109 u16 seqno)
110 {
111 lockdep_assert_held(&chain->lock);
112
113 if (chain->seqno == seqno)
114 return false;
115
116 if (!hlist_empty(&chain->fragment_list))
117 batadv_frag_clear_chain(&chain->fragment_list, true);
118
119 chain->size = 0;
120 chain->seqno = seqno;
121
122 return true;
123 }
124
125 /**
126 * batadv_frag_insert_packet() - insert a fragment into a fragment chain
127 * @orig_node: originator that the fragment was received from
128 * @skb: skb to insert
129 * @chain_out: list head to attach complete chains of fragments to
130 *
131 * Insert a new fragment into the reverse ordered chain in the right table
132 * entry. The hash table entry is cleared if "old" fragments exist in it.
133 *
134 * Return: true if skb is buffered, false on error. If the chain has all the
135 * fragments needed to merge the packet, the chain is moved to the passed head
136 * to avoid locking the chain in the table.
137 */
batadv_frag_insert_packet(struct batadv_orig_node * orig_node,struct sk_buff * skb,struct hlist_head * chain_out)138 static bool batadv_frag_insert_packet(struct batadv_orig_node *orig_node,
139 struct sk_buff *skb,
140 struct hlist_head *chain_out)
141 {
142 struct batadv_frag_table_entry *chain;
143 struct batadv_frag_list_entry *frag_entry_new = NULL, *frag_entry_curr;
144 struct batadv_frag_list_entry *frag_entry_last = NULL;
145 struct batadv_frag_packet *frag_packet;
146 u8 bucket;
147 u16 seqno, hdr_size = sizeof(struct batadv_frag_packet);
148 bool ret = false;
149
150 /* Linearize packet to avoid linearizing 16 packets in a row when doing
151 * the later merge. Non-linear merge should be added to remove this
152 * linearization.
153 */
154 if (skb_linearize(skb) < 0)
155 goto err;
156
157 frag_packet = (struct batadv_frag_packet *)skb->data;
158 seqno = ntohs(frag_packet->seqno);
159 bucket = seqno % BATADV_FRAG_BUFFER_COUNT;
160
161 frag_entry_new = kmalloc(sizeof(*frag_entry_new), GFP_ATOMIC);
162 if (!frag_entry_new)
163 goto err;
164
165 frag_entry_new->skb = skb;
166 frag_entry_new->no = frag_packet->no;
167
168 /* Select entry in the "chain table" and delete any prior fragments
169 * with another sequence number. batadv_frag_init_chain() returns true,
170 * if the list is empty at return.
171 */
172 chain = &orig_node->fragments[bucket];
173 spin_lock_bh(&chain->lock);
174 if (batadv_frag_init_chain(chain, seqno)) {
175 hlist_add_head(&frag_entry_new->list, &chain->fragment_list);
176 chain->size = skb->len - hdr_size;
177 chain->timestamp = jiffies;
178 chain->total_size = ntohs(frag_packet->total_size);
179 ret = true;
180 goto out;
181 }
182
183 /* Find the position for the new fragment. */
184 hlist_for_each_entry(frag_entry_curr, &chain->fragment_list, list) {
185 /* Drop packet if fragment already exists. */
186 if (frag_entry_curr->no == frag_entry_new->no)
187 goto err_unlock;
188
189 /* Order fragments from highest to lowest. */
190 if (frag_entry_curr->no < frag_entry_new->no) {
191 hlist_add_before(&frag_entry_new->list,
192 &frag_entry_curr->list);
193 chain->size += skb->len - hdr_size;
194 chain->timestamp = jiffies;
195 ret = true;
196 goto out;
197 }
198
199 /* store current entry because it could be the last in list */
200 frag_entry_last = frag_entry_curr;
201 }
202
203 /* Reached the end of the list, so insert after 'frag_entry_last'. */
204 if (likely(frag_entry_last)) {
205 hlist_add_behind(&frag_entry_new->list, &frag_entry_last->list);
206 chain->size += skb->len - hdr_size;
207 chain->timestamp = jiffies;
208 ret = true;
209 }
210
211 out:
212 if (chain->size > batadv_frag_size_limit() ||
213 chain->total_size != ntohs(frag_packet->total_size) ||
214 chain->total_size > batadv_frag_size_limit()) {
215 /* Clear chain if total size of either the list or the packet
216 * exceeds the maximum size of one merged packet. Don't allow
217 * packets to have different total_size.
218 */
219 batadv_frag_clear_chain(&chain->fragment_list, true);
220 chain->size = 0;
221 } else if (ntohs(frag_packet->total_size) == chain->size) {
222 /* All fragments received. Hand over chain to caller. */
223 hlist_move_list(&chain->fragment_list, chain_out);
224 chain->size = 0;
225 }
226
227 err_unlock:
228 spin_unlock_bh(&chain->lock);
229
230 err:
231 if (!ret) {
232 kfree(frag_entry_new);
233 kfree_skb(skb);
234 }
235
236 return ret;
237 }
238
239 /**
240 * batadv_frag_merge_packets() - merge a chain of fragments
241 * @chain: head of chain with fragments
242 *
243 * Expand the first skb in the chain and copy the content of the remaining
244 * skb's into the expanded one. After doing so, clear the chain.
245 *
246 * Return: the merged skb or NULL on error.
247 */
248 static struct sk_buff *
batadv_frag_merge_packets(struct hlist_head * chain)249 batadv_frag_merge_packets(struct hlist_head *chain)
250 {
251 struct batadv_frag_packet *packet;
252 struct batadv_frag_list_entry *entry;
253 struct sk_buff *skb_out;
254 int size, hdr_size = sizeof(struct batadv_frag_packet);
255 bool dropped = false;
256
257 /* Remove first entry, as this is the destination for the rest of the
258 * fragments.
259 */
260 entry = hlist_entry(chain->first, struct batadv_frag_list_entry, list);
261 hlist_del(&entry->list);
262 skb_out = entry->skb;
263 kfree(entry);
264
265 packet = (struct batadv_frag_packet *)skb_out->data;
266 size = ntohs(packet->total_size) + hdr_size;
267
268 /* Make room for the rest of the fragments. */
269 if (pskb_expand_head(skb_out, 0, size - skb_out->len, GFP_ATOMIC) < 0) {
270 kfree_skb(skb_out);
271 skb_out = NULL;
272 dropped = true;
273 goto free;
274 }
275
276 /* Move the existing MAC header to just before the payload. (Override
277 * the fragment header.)
278 */
279 skb_pull(skb_out, hdr_size);
280 skb_out->ip_summed = CHECKSUM_NONE;
281 memmove(skb_out->data - ETH_HLEN, skb_mac_header(skb_out), ETH_HLEN);
282 skb_set_mac_header(skb_out, -ETH_HLEN);
283 skb_reset_network_header(skb_out);
284 skb_reset_transport_header(skb_out);
285
286 /* Copy the payload of the each fragment into the last skb */
287 hlist_for_each_entry(entry, chain, list) {
288 size = entry->skb->len - hdr_size;
289 skb_put_data(skb_out, entry->skb->data + hdr_size, size);
290 }
291
292 free:
293 /* Locking is not needed, because 'chain' is not part of any orig. */
294 batadv_frag_clear_chain(chain, dropped);
295 return skb_out;
296 }
297
298 /**
299 * batadv_frag_skb_buffer() - buffer fragment for later merge
300 * @skb: skb to buffer
301 * @orig_node_src: originator that the skb is received from
302 *
303 * Add fragment to buffer and merge fragments if possible.
304 *
305 * There are three possible outcomes: 1) Packet is merged: Return true and
306 * set *skb to merged packet; 2) Packet is buffered: Return true and set *skb
307 * to NULL; 3) Error: Return false and free skb.
308 *
309 * Return: true when packet is merged or buffered, false when skb is not not
310 * used.
311 */
batadv_frag_skb_buffer(struct sk_buff ** skb,struct batadv_orig_node * orig_node_src)312 bool batadv_frag_skb_buffer(struct sk_buff **skb,
313 struct batadv_orig_node *orig_node_src)
314 {
315 struct sk_buff *skb_out = NULL;
316 struct hlist_head head = HLIST_HEAD_INIT;
317 bool ret = false;
318
319 /* Add packet to buffer and table entry if merge is possible. */
320 if (!batadv_frag_insert_packet(orig_node_src, *skb, &head))
321 goto out_err;
322
323 /* Leave if more fragments are needed to merge. */
324 if (hlist_empty(&head))
325 goto out;
326
327 skb_out = batadv_frag_merge_packets(&head);
328 if (!skb_out)
329 goto out_err;
330
331 out:
332 ret = true;
333 out_err:
334 *skb = skb_out;
335 return ret;
336 }
337
338 /**
339 * batadv_frag_skb_fwd() - forward fragments that would exceed MTU when merged
340 * @skb: skb to forward
341 * @recv_if: interface that the skb is received on
342 * @orig_node_src: originator that the skb is received from
343 *
344 * Look up the next-hop of the fragments payload and check if the merged packet
345 * will exceed the MTU towards the next-hop. If so, the fragment is forwarded
346 * without merging it.
347 *
348 * Return: true if the fragment is consumed/forwarded, false otherwise.
349 */
batadv_frag_skb_fwd(struct sk_buff * skb,struct batadv_hard_iface * recv_if,struct batadv_orig_node * orig_node_src)350 bool batadv_frag_skb_fwd(struct sk_buff *skb,
351 struct batadv_hard_iface *recv_if,
352 struct batadv_orig_node *orig_node_src)
353 {
354 struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
355 struct batadv_orig_node *orig_node_dst;
356 struct batadv_neigh_node *neigh_node = NULL;
357 struct batadv_frag_packet *packet;
358 u16 total_size;
359 bool ret = false;
360
361 packet = (struct batadv_frag_packet *)skb->data;
362 orig_node_dst = batadv_orig_hash_find(bat_priv, packet->dest);
363 if (!orig_node_dst)
364 goto out;
365
366 neigh_node = batadv_find_router(bat_priv, orig_node_dst, recv_if);
367 if (!neigh_node)
368 goto out;
369
370 /* Forward the fragment, if the merged packet would be too big to
371 * be assembled.
372 */
373 total_size = ntohs(packet->total_size);
374 if (total_size > neigh_node->if_incoming->net_dev->mtu) {
375 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_FWD);
376 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_FWD_BYTES,
377 skb->len + ETH_HLEN);
378
379 packet->ttl--;
380 batadv_send_unicast_skb(skb, neigh_node);
381 ret = true;
382 }
383
384 out:
385 if (orig_node_dst)
386 batadv_orig_node_put(orig_node_dst);
387 if (neigh_node)
388 batadv_neigh_node_put(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 * @fragment_size: 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 * Return: the new fragment, NULL on error.
403 */
batadv_frag_create(struct sk_buff * skb,struct batadv_frag_packet * frag_head,unsigned int fragment_size)404 static struct sk_buff *batadv_frag_create(struct sk_buff *skb,
405 struct batadv_frag_packet *frag_head,
406 unsigned int fragment_size)
407 {
408 struct sk_buff *skb_fragment;
409 unsigned int header_size = sizeof(*frag_head);
410 unsigned int mtu = fragment_size + header_size;
411
412 skb_fragment = netdev_alloc_skb(NULL, mtu + ETH_HLEN);
413 if (!skb_fragment)
414 goto err;
415
416 skb_fragment->priority = skb->priority;
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 * Return: the netdev tx status or a negative errno code on a failure
437 */
batadv_frag_send_packet(struct sk_buff * skb,struct batadv_orig_node * orig_node,struct batadv_neigh_node * neigh_node)438 int 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 int mtu = neigh_node->if_incoming->net_dev->mtu;
447 unsigned int header_size = sizeof(frag_header);
448 unsigned int max_fragment_size, num_fragments;
449 int ret;
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 int, mtu, BATADV_FRAG_MAX_FRAG_SIZE);
455 max_fragment_size = mtu - header_size;
456
457 if (skb->len == 0 || max_fragment_size == 0)
458 return -EINVAL;
459
460 num_fragments = (skb->len - 1) / max_fragment_size + 1;
461 max_fragment_size = (skb->len - 1) / num_fragments + 1;
462
463 /* Don't even try to fragment, if we need more than 16 fragments */
464 if (num_fragments > BATADV_FRAG_MAX_FRAGMENTS) {
465 ret = -EAGAIN;
466 goto free_skb;
467 }
468
469 bat_priv = orig_node->bat_priv;
470 primary_if = batadv_primary_if_get_selected(bat_priv);
471 if (!primary_if) {
472 ret = -EINVAL;
473 goto free_skb;
474 }
475
476 /* Create one header to be copied to all fragments */
477 frag_header.packet_type = BATADV_UNICAST_FRAG;
478 frag_header.version = BATADV_COMPAT_VERSION;
479 frag_header.ttl = BATADV_TTL;
480 frag_header.seqno = htons(atomic_inc_return(&bat_priv->frag_seqno));
481 frag_header.reserved = 0;
482 frag_header.no = 0;
483 frag_header.total_size = htons(skb->len);
484
485 /* skb->priority values from 256->263 are magic values to
486 * directly indicate a specific 802.1d priority. This is used
487 * to allow 802.1d priority to be passed directly in from VLAN
488 * tags, etc.
489 */
490 if (skb->priority >= 256 && skb->priority <= 263)
491 frag_header.priority = skb->priority - 256;
492 else
493 frag_header.priority = 0;
494
495 ether_addr_copy(frag_header.orig, primary_if->net_dev->dev_addr);
496 ether_addr_copy(frag_header.dest, orig_node->orig);
497
498 /* Eat and send fragments from the tail of skb */
499 while (skb->len > max_fragment_size) {
500 /* The initial check in this function should cover this case */
501 if (unlikely(frag_header.no == BATADV_FRAG_MAX_FRAGMENTS - 1)) {
502 ret = -EINVAL;
503 goto put_primary_if;
504 }
505
506 skb_fragment = batadv_frag_create(skb, &frag_header,
507 max_fragment_size);
508 if (!skb_fragment) {
509 ret = -ENOMEM;
510 goto put_primary_if;
511 }
512
513 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX);
514 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES,
515 skb_fragment->len + ETH_HLEN);
516 ret = batadv_send_unicast_skb(skb_fragment, neigh_node);
517 if (ret != NET_XMIT_SUCCESS) {
518 ret = NET_XMIT_DROP;
519 goto put_primary_if;
520 }
521
522 frag_header.no++;
523 }
524
525 /* Make room for the fragment header. */
526 if (batadv_skb_head_push(skb, header_size) < 0 ||
527 pskb_expand_head(skb, header_size + ETH_HLEN, 0, GFP_ATOMIC) < 0) {
528 ret = -ENOMEM;
529 goto put_primary_if;
530 }
531
532 memcpy(skb->data, &frag_header, header_size);
533
534 /* Send the last fragment */
535 batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX);
536 batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES,
537 skb->len + ETH_HLEN);
538 ret = batadv_send_unicast_skb(skb, neigh_node);
539 /* skb was consumed */
540 skb = NULL;
541
542 put_primary_if:
543 batadv_hardif_put(primary_if);
544 free_skb:
545 kfree_skb(skb);
546
547 return ret;
548 }
549