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TOMOYO Linux Cross Reference
Linux/net/batman-adv/tp_meter.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /* Copyright (C) 2012-2019  B.A.T.M.A.N. contributors:
  3  *
  4  * Edo Monticelli, Antonio Quartulli
  5  */
  6 
  7 #include "tp_meter.h"
  8 #include "main.h"
  9 
 10 #include <linux/atomic.h>
 11 #include <linux/build_bug.h>
 12 #include <linux/byteorder/generic.h>
 13 #include <linux/cache.h>
 14 #include <linux/compiler.h>
 15 #include <linux/err.h>
 16 #include <linux/etherdevice.h>
 17 #include <linux/gfp.h>
 18 #include <linux/if_ether.h>
 19 #include <linux/init.h>
 20 #include <linux/jiffies.h>
 21 #include <linux/kernel.h>
 22 #include <linux/kref.h>
 23 #include <linux/kthread.h>
 24 #include <linux/limits.h>
 25 #include <linux/list.h>
 26 #include <linux/netdevice.h>
 27 #include <linux/param.h>
 28 #include <linux/printk.h>
 29 #include <linux/random.h>
 30 #include <linux/rculist.h>
 31 #include <linux/rcupdate.h>
 32 #include <linux/sched.h>
 33 #include <linux/skbuff.h>
 34 #include <linux/slab.h>
 35 #include <linux/spinlock.h>
 36 #include <linux/stddef.h>
 37 #include <linux/string.h>
 38 #include <linux/timer.h>
 39 #include <linux/wait.h>
 40 #include <linux/workqueue.h>
 41 #include <uapi/linux/batadv_packet.h>
 42 #include <uapi/linux/batman_adv.h>
 43 
 44 #include "hard-interface.h"
 45 #include "log.h"
 46 #include "netlink.h"
 47 #include "originator.h"
 48 #include "send.h"
 49 
 50 /**
 51  * BATADV_TP_DEF_TEST_LENGTH - Default test length if not specified by the user
 52  *  in milliseconds
 53  */
 54 #define BATADV_TP_DEF_TEST_LENGTH 10000
 55 
 56 /**
 57  * BATADV_TP_AWND - Advertised window by the receiver (in bytes)
 58  */
 59 #define BATADV_TP_AWND 0x20000000
 60 
 61 /**
 62  * BATADV_TP_RECV_TIMEOUT - Receiver activity timeout. If the receiver does not
 63  *  get anything for such amount of milliseconds, the connection is killed
 64  */
 65 #define BATADV_TP_RECV_TIMEOUT 1000
 66 
 67 /**
 68  * BATADV_TP_MAX_RTO - Maximum sender timeout. If the sender RTO gets beyond
 69  * such amound of milliseconds, the receiver is considered unreachable and the
 70  * connection is killed
 71  */
 72 #define BATADV_TP_MAX_RTO 30000
 73 
 74 /**
 75  * BATADV_TP_FIRST_SEQ - First seqno of each session. The number is rather high
 76  *  in order to immediately trigger a wrap around (test purposes)
 77  */
 78 #define BATADV_TP_FIRST_SEQ ((u32)-1 - 2000)
 79 
 80 /**
 81  * BATADV_TP_PLEN - length of the payload (data after the batadv_unicast header)
 82  *  to simulate
 83  */
 84 #define BATADV_TP_PLEN (BATADV_TP_PACKET_LEN - ETH_HLEN - \
 85                         sizeof(struct batadv_unicast_packet))
 86 
 87 static u8 batadv_tp_prerandom[4096] __read_mostly;
 88 
 89 /**
 90  * batadv_tp_session_cookie() - generate session cookie based on session ids
 91  * @session: TP session identifier
 92  * @icmp_uid: icmp pseudo uid of the tp session
 93  *
 94  * Return: 32 bit tp_meter session cookie
 95  */
 96 static u32 batadv_tp_session_cookie(const u8 session[2], u8 icmp_uid)
 97 {
 98         u32 cookie;
 99 
100         cookie = icmp_uid << 16;
101         cookie |= session[0] << 8;
102         cookie |= session[1];
103 
104         return cookie;
105 }
106 
107 /**
108  * batadv_tp_cwnd() - compute the new cwnd size
109  * @base: base cwnd size value
110  * @increment: the value to add to base to get the new size
111  * @min: minumim cwnd value (usually MSS)
112  *
113  * Return the new cwnd size and ensures it does not exceed the Advertised
114  * Receiver Window size. It is wrap around safe.
115  * For details refer to Section 3.1 of RFC5681
116  *
117  * Return: new congestion window size in bytes
118  */
119 static u32 batadv_tp_cwnd(u32 base, u32 increment, u32 min)
120 {
121         u32 new_size = base + increment;
122 
123         /* check for wrap-around */
124         if (new_size < base)
125                 new_size = (u32)ULONG_MAX;
126 
127         new_size = min_t(u32, new_size, BATADV_TP_AWND);
128 
129         return max_t(u32, new_size, min);
130 }
131 
132 /**
133  * batadv_tp_updated_cwnd() - update the Congestion Windows
134  * @tp_vars: the private data of the current TP meter session
135  * @mss: maximum segment size of transmission
136  *
137  * 1) if the session is in Slow Start, the CWND has to be increased by 1
138  * MSS every unique received ACK
139  * 2) if the session is in Congestion Avoidance, the CWND has to be
140  * increased by MSS * MSS / CWND for every unique received ACK
141  */
142 static void batadv_tp_update_cwnd(struct batadv_tp_vars *tp_vars, u32 mss)
143 {
144         spin_lock_bh(&tp_vars->cwnd_lock);
145 
146         /* slow start... */
147         if (tp_vars->cwnd <= tp_vars->ss_threshold) {
148                 tp_vars->dec_cwnd = 0;
149                 tp_vars->cwnd = batadv_tp_cwnd(tp_vars->cwnd, mss, mss);
150                 spin_unlock_bh(&tp_vars->cwnd_lock);
151                 return;
152         }
153 
154         /* increment CWND at least of 1 (section 3.1 of RFC5681) */
155         tp_vars->dec_cwnd += max_t(u32, 1U << 3,
156                                    ((mss * mss) << 6) / (tp_vars->cwnd << 3));
157         if (tp_vars->dec_cwnd < (mss << 3)) {
158                 spin_unlock_bh(&tp_vars->cwnd_lock);
159                 return;
160         }
161 
162         tp_vars->cwnd = batadv_tp_cwnd(tp_vars->cwnd, mss, mss);
163         tp_vars->dec_cwnd = 0;
164 
165         spin_unlock_bh(&tp_vars->cwnd_lock);
166 }
167 
168 /**
169  * batadv_tp_update_rto() - calculate new retransmission timeout
170  * @tp_vars: the private data of the current TP meter session
171  * @new_rtt: new roundtrip time in msec
172  */
173 static void batadv_tp_update_rto(struct batadv_tp_vars *tp_vars,
174                                  u32 new_rtt)
175 {
176         long m = new_rtt;
177 
178         /* RTT update
179          * Details in Section 2.2 and 2.3 of RFC6298
180          *
181          * It's tricky to understand. Don't lose hair please.
182          * Inspired by tcp_rtt_estimator() tcp_input.c
183          */
184         if (tp_vars->srtt != 0) {
185                 m -= (tp_vars->srtt >> 3); /* m is now error in rtt est */
186                 tp_vars->srtt += m; /* rtt = 7/8 srtt + 1/8 new */
187                 if (m < 0)
188                         m = -m;
189 
190                 m -= (tp_vars->rttvar >> 2);
191                 tp_vars->rttvar += m; /* mdev ~= 3/4 rttvar + 1/4 new */
192         } else {
193                 /* first measure getting in */
194                 tp_vars->srtt = m << 3; /* take the measured time to be srtt */
195                 tp_vars->rttvar = m << 1; /* new_rtt / 2 */
196         }
197 
198         /* rto = srtt + 4 * rttvar.
199          * rttvar is scaled by 4, therefore doesn't need to be multiplied
200          */
201         tp_vars->rto = (tp_vars->srtt >> 3) + tp_vars->rttvar;
202 }
203 
204 /**
205  * batadv_tp_batctl_notify() - send client status result to client
206  * @reason: reason for tp meter session stop
207  * @dst: destination of tp_meter session
208  * @bat_priv: the bat priv with all the soft interface information
209  * @start_time: start of transmission in jiffies
210  * @total_sent: bytes acked to the receiver
211  * @cookie: cookie of tp_meter session
212  */
213 static void batadv_tp_batctl_notify(enum batadv_tp_meter_reason reason,
214                                     const u8 *dst, struct batadv_priv *bat_priv,
215                                     unsigned long start_time, u64 total_sent,
216                                     u32 cookie)
217 {
218         u32 test_time;
219         u8 result;
220         u32 total_bytes;
221 
222         if (!batadv_tp_is_error(reason)) {
223                 result = BATADV_TP_REASON_COMPLETE;
224                 test_time = jiffies_to_msecs(jiffies - start_time);
225                 total_bytes = total_sent;
226         } else {
227                 result = reason;
228                 test_time = 0;
229                 total_bytes = 0;
230         }
231 
232         batadv_netlink_tpmeter_notify(bat_priv, dst, result, test_time,
233                                       total_bytes, cookie);
234 }
235 
236 /**
237  * batadv_tp_batctl_error_notify() - send client error result to client
238  * @reason: reason for tp meter session stop
239  * @dst: destination of tp_meter session
240  * @bat_priv: the bat priv with all the soft interface information
241  * @cookie: cookie of tp_meter session
242  */
243 static void batadv_tp_batctl_error_notify(enum batadv_tp_meter_reason reason,
244                                           const u8 *dst,
245                                           struct batadv_priv *bat_priv,
246                                           u32 cookie)
247 {
248         batadv_tp_batctl_notify(reason, dst, bat_priv, 0, 0, cookie);
249 }
250 
251 /**
252  * batadv_tp_list_find() - find a tp_vars object in the global list
253  * @bat_priv: the bat priv with all the soft interface information
254  * @dst: the other endpoint MAC address to look for
255  *
256  * Look for a tp_vars object matching dst as end_point and return it after
257  * having incremented the refcounter. Return NULL is not found
258  *
259  * Return: matching tp_vars or NULL when no tp_vars with @dst was found
260  */
261 static struct batadv_tp_vars *batadv_tp_list_find(struct batadv_priv *bat_priv,
262                                                   const u8 *dst)
263 {
264         struct batadv_tp_vars *pos, *tp_vars = NULL;
265 
266         rcu_read_lock();
267         hlist_for_each_entry_rcu(pos, &bat_priv->tp_list, list) {
268                 if (!batadv_compare_eth(pos->other_end, dst))
269                         continue;
270 
271                 /* most of the time this function is invoked during the normal
272                  * process..it makes sens to pay more when the session is
273                  * finished and to speed the process up during the measurement
274                  */
275                 if (unlikely(!kref_get_unless_zero(&pos->refcount)))
276                         continue;
277 
278                 tp_vars = pos;
279                 break;
280         }
281         rcu_read_unlock();
282 
283         return tp_vars;
284 }
285 
286 /**
287  * batadv_tp_list_find_session() - find tp_vars session object in the global
288  *  list
289  * @bat_priv: the bat priv with all the soft interface information
290  * @dst: the other endpoint MAC address to look for
291  * @session: session identifier
292  *
293  * Look for a tp_vars object matching dst as end_point, session as tp meter
294  * session and return it after having incremented the refcounter. Return NULL
295  * is not found
296  *
297  * Return: matching tp_vars or NULL when no tp_vars was found
298  */
299 static struct batadv_tp_vars *
300 batadv_tp_list_find_session(struct batadv_priv *bat_priv, const u8 *dst,
301                             const u8 *session)
302 {
303         struct batadv_tp_vars *pos, *tp_vars = NULL;
304 
305         rcu_read_lock();
306         hlist_for_each_entry_rcu(pos, &bat_priv->tp_list, list) {
307                 if (!batadv_compare_eth(pos->other_end, dst))
308                         continue;
309 
310                 if (memcmp(pos->session, session, sizeof(pos->session)) != 0)
311                         continue;
312 
313                 /* most of the time this function is invoked during the normal
314                  * process..it makes sense to pay more when the session is
315                  * finished and to speed the process up during the measurement
316                  */
317                 if (unlikely(!kref_get_unless_zero(&pos->refcount)))
318                         continue;
319 
320                 tp_vars = pos;
321                 break;
322         }
323         rcu_read_unlock();
324 
325         return tp_vars;
326 }
327 
328 /**
329  * batadv_tp_vars_release() - release batadv_tp_vars from lists and queue for
330  *  free after rcu grace period
331  * @ref: kref pointer of the batadv_tp_vars
332  */
333 static void batadv_tp_vars_release(struct kref *ref)
334 {
335         struct batadv_tp_vars *tp_vars;
336         struct batadv_tp_unacked *un, *safe;
337 
338         tp_vars = container_of(ref, struct batadv_tp_vars, refcount);
339 
340         /* lock should not be needed because this object is now out of any
341          * context!
342          */
343         spin_lock_bh(&tp_vars->unacked_lock);
344         list_for_each_entry_safe(un, safe, &tp_vars->unacked_list, list) {
345                 list_del(&un->list);
346                 kfree(un);
347         }
348         spin_unlock_bh(&tp_vars->unacked_lock);
349 
350         kfree_rcu(tp_vars, rcu);
351 }
352 
353 /**
354  * batadv_tp_vars_put() - decrement the batadv_tp_vars refcounter and possibly
355  *  release it
356  * @tp_vars: the private data of the current TP meter session to be free'd
357  */
358 static void batadv_tp_vars_put(struct batadv_tp_vars *tp_vars)
359 {
360         kref_put(&tp_vars->refcount, batadv_tp_vars_release);
361 }
362 
363 /**
364  * batadv_tp_sender_cleanup() - cleanup sender data and drop and timer
365  * @bat_priv: the bat priv with all the soft interface information
366  * @tp_vars: the private data of the current TP meter session to cleanup
367  */
368 static void batadv_tp_sender_cleanup(struct batadv_priv *bat_priv,
369                                      struct batadv_tp_vars *tp_vars)
370 {
371         cancel_delayed_work(&tp_vars->finish_work);
372 
373         spin_lock_bh(&tp_vars->bat_priv->tp_list_lock);
374         hlist_del_rcu(&tp_vars->list);
375         spin_unlock_bh(&tp_vars->bat_priv->tp_list_lock);
376 
377         /* drop list reference */
378         batadv_tp_vars_put(tp_vars);
379 
380         atomic_dec(&tp_vars->bat_priv->tp_num);
381 
382         /* kill the timer and remove its reference */
383         del_timer_sync(&tp_vars->timer);
384         /* the worker might have rearmed itself therefore we kill it again. Note
385          * that if the worker should run again before invoking the following
386          * del_timer(), it would not re-arm itself once again because the status
387          * is OFF now
388          */
389         del_timer(&tp_vars->timer);
390         batadv_tp_vars_put(tp_vars);
391 }
392 
393 /**
394  * batadv_tp_sender_end() - print info about ended session and inform client
395  * @bat_priv: the bat priv with all the soft interface information
396  * @tp_vars: the private data of the current TP meter session
397  */
398 static void batadv_tp_sender_end(struct batadv_priv *bat_priv,
399                                  struct batadv_tp_vars *tp_vars)
400 {
401         u32 session_cookie;
402 
403         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
404                    "Test towards %pM finished..shutting down (reason=%d)\n",
405                    tp_vars->other_end, tp_vars->reason);
406 
407         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
408                    "Last timing stats: SRTT=%ums RTTVAR=%ums RTO=%ums\n",
409                    tp_vars->srtt >> 3, tp_vars->rttvar >> 2, tp_vars->rto);
410 
411         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
412                    "Final values: cwnd=%u ss_threshold=%u\n",
413                    tp_vars->cwnd, tp_vars->ss_threshold);
414 
415         session_cookie = batadv_tp_session_cookie(tp_vars->session,
416                                                   tp_vars->icmp_uid);
417 
418         batadv_tp_batctl_notify(tp_vars->reason,
419                                 tp_vars->other_end,
420                                 bat_priv,
421                                 tp_vars->start_time,
422                                 atomic64_read(&tp_vars->tot_sent),
423                                 session_cookie);
424 }
425 
426 /**
427  * batadv_tp_sender_shutdown() - let sender thread/timer stop gracefully
428  * @tp_vars: the private data of the current TP meter session
429  * @reason: reason for tp meter session stop
430  */
431 static void batadv_tp_sender_shutdown(struct batadv_tp_vars *tp_vars,
432                                       enum batadv_tp_meter_reason reason)
433 {
434         if (!atomic_dec_and_test(&tp_vars->sending))
435                 return;
436 
437         tp_vars->reason = reason;
438 }
439 
440 /**
441  * batadv_tp_sender_finish() - stop sender session after test_length was reached
442  * @work: delayed work reference of the related tp_vars
443  */
444 static void batadv_tp_sender_finish(struct work_struct *work)
445 {
446         struct delayed_work *delayed_work;
447         struct batadv_tp_vars *tp_vars;
448 
449         delayed_work = to_delayed_work(work);
450         tp_vars = container_of(delayed_work, struct batadv_tp_vars,
451                                finish_work);
452 
453         batadv_tp_sender_shutdown(tp_vars, BATADV_TP_REASON_COMPLETE);
454 }
455 
456 /**
457  * batadv_tp_reset_sender_timer() - reschedule the sender timer
458  * @tp_vars: the private TP meter data for this session
459  *
460  * Reschedule the timer using tp_vars->rto as delay
461  */
462 static void batadv_tp_reset_sender_timer(struct batadv_tp_vars *tp_vars)
463 {
464         /* most of the time this function is invoked while normal packet
465          * reception...
466          */
467         if (unlikely(atomic_read(&tp_vars->sending) == 0))
468                 /* timer ref will be dropped in batadv_tp_sender_cleanup */
469                 return;
470 
471         mod_timer(&tp_vars->timer, jiffies + msecs_to_jiffies(tp_vars->rto));
472 }
473 
474 /**
475  * batadv_tp_sender_timeout() - timer that fires in case of packet loss
476  * @t: address to timer_list inside tp_vars
477  *
478  * If fired it means that there was packet loss.
479  * Switch to Slow Start, set the ss_threshold to half of the current cwnd and
480  * reset the cwnd to 3*MSS
481  */
482 static void batadv_tp_sender_timeout(struct timer_list *t)
483 {
484         struct batadv_tp_vars *tp_vars = from_timer(tp_vars, t, timer);
485         struct batadv_priv *bat_priv = tp_vars->bat_priv;
486 
487         if (atomic_read(&tp_vars->sending) == 0)
488                 return;
489 
490         /* if the user waited long enough...shutdown the test */
491         if (unlikely(tp_vars->rto >= BATADV_TP_MAX_RTO)) {
492                 batadv_tp_sender_shutdown(tp_vars,
493                                           BATADV_TP_REASON_DST_UNREACHABLE);
494                 return;
495         }
496 
497         /* RTO exponential backoff
498          * Details in Section 5.5 of RFC6298
499          */
500         tp_vars->rto <<= 1;
501 
502         spin_lock_bh(&tp_vars->cwnd_lock);
503 
504         tp_vars->ss_threshold = tp_vars->cwnd >> 1;
505         if (tp_vars->ss_threshold < BATADV_TP_PLEN * 2)
506                 tp_vars->ss_threshold = BATADV_TP_PLEN * 2;
507 
508         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
509                    "Meter: RTO fired during test towards %pM! cwnd=%u new ss_thr=%u, resetting last_sent to %u\n",
510                    tp_vars->other_end, tp_vars->cwnd, tp_vars->ss_threshold,
511                    atomic_read(&tp_vars->last_acked));
512 
513         tp_vars->cwnd = BATADV_TP_PLEN * 3;
514 
515         spin_unlock_bh(&tp_vars->cwnd_lock);
516 
517         /* resend the non-ACKed packets.. */
518         tp_vars->last_sent = atomic_read(&tp_vars->last_acked);
519         wake_up(&tp_vars->more_bytes);
520 
521         batadv_tp_reset_sender_timer(tp_vars);
522 }
523 
524 /**
525  * batadv_tp_fill_prerandom() - Fill buffer with prefetched random bytes
526  * @tp_vars: the private TP meter data for this session
527  * @buf: Buffer to fill with bytes
528  * @nbytes: amount of pseudorandom bytes
529  */
530 static void batadv_tp_fill_prerandom(struct batadv_tp_vars *tp_vars,
531                                      u8 *buf, size_t nbytes)
532 {
533         u32 local_offset;
534         size_t bytes_inbuf;
535         size_t to_copy;
536         size_t pos = 0;
537 
538         spin_lock_bh(&tp_vars->prerandom_lock);
539         local_offset = tp_vars->prerandom_offset;
540         tp_vars->prerandom_offset += nbytes;
541         tp_vars->prerandom_offset %= sizeof(batadv_tp_prerandom);
542         spin_unlock_bh(&tp_vars->prerandom_lock);
543 
544         while (nbytes) {
545                 local_offset %= sizeof(batadv_tp_prerandom);
546                 bytes_inbuf = sizeof(batadv_tp_prerandom) - local_offset;
547                 to_copy = min(nbytes, bytes_inbuf);
548 
549                 memcpy(&buf[pos], &batadv_tp_prerandom[local_offset], to_copy);
550                 pos += to_copy;
551                 nbytes -= to_copy;
552                 local_offset = 0;
553         }
554 }
555 
556 /**
557  * batadv_tp_send_msg() - send a single message
558  * @tp_vars: the private TP meter data for this session
559  * @src: source mac address
560  * @orig_node: the originator of the destination
561  * @seqno: sequence number of this packet
562  * @len: length of the entire packet
563  * @session: session identifier
564  * @uid: local ICMP "socket" index
565  * @timestamp: timestamp in jiffies which is replied in ack
566  *
567  * Create and send a single TP Meter message.
568  *
569  * Return: 0 on success, BATADV_TP_REASON_DST_UNREACHABLE if the destination is
570  * not reachable, BATADV_TP_REASON_MEMORY_ERROR if the packet couldn't be
571  * allocated
572  */
573 static int batadv_tp_send_msg(struct batadv_tp_vars *tp_vars, const u8 *src,
574                               struct batadv_orig_node *orig_node,
575                               u32 seqno, size_t len, const u8 *session,
576                               int uid, u32 timestamp)
577 {
578         struct batadv_icmp_tp_packet *icmp;
579         struct sk_buff *skb;
580         int r;
581         u8 *data;
582         size_t data_len;
583 
584         skb = netdev_alloc_skb_ip_align(NULL, len + ETH_HLEN);
585         if (unlikely(!skb))
586                 return BATADV_TP_REASON_MEMORY_ERROR;
587 
588         skb_reserve(skb, ETH_HLEN);
589         icmp = skb_put(skb, sizeof(*icmp));
590 
591         /* fill the icmp header */
592         ether_addr_copy(icmp->dst, orig_node->orig);
593         ether_addr_copy(icmp->orig, src);
594         icmp->version = BATADV_COMPAT_VERSION;
595         icmp->packet_type = BATADV_ICMP;
596         icmp->ttl = BATADV_TTL;
597         icmp->msg_type = BATADV_TP;
598         icmp->uid = uid;
599 
600         icmp->subtype = BATADV_TP_MSG;
601         memcpy(icmp->session, session, sizeof(icmp->session));
602         icmp->seqno = htonl(seqno);
603         icmp->timestamp = htonl(timestamp);
604 
605         data_len = len - sizeof(*icmp);
606         data = skb_put(skb, data_len);
607         batadv_tp_fill_prerandom(tp_vars, data, data_len);
608 
609         r = batadv_send_skb_to_orig(skb, orig_node, NULL);
610         if (r == NET_XMIT_SUCCESS)
611                 return 0;
612 
613         return BATADV_TP_REASON_CANT_SEND;
614 }
615 
616 /**
617  * batadv_tp_recv_ack() - ACK receiving function
618  * @bat_priv: the bat priv with all the soft interface information
619  * @skb: the buffer containing the received packet
620  *
621  * Process a received TP ACK packet
622  */
623 static void batadv_tp_recv_ack(struct batadv_priv *bat_priv,
624                                const struct sk_buff *skb)
625 {
626         struct batadv_hard_iface *primary_if = NULL;
627         struct batadv_orig_node *orig_node = NULL;
628         const struct batadv_icmp_tp_packet *icmp;
629         struct batadv_tp_vars *tp_vars;
630         size_t packet_len, mss;
631         u32 rtt, recv_ack, cwnd;
632         unsigned char *dev_addr;
633 
634         packet_len = BATADV_TP_PLEN;
635         mss = BATADV_TP_PLEN;
636         packet_len += sizeof(struct batadv_unicast_packet);
637 
638         icmp = (struct batadv_icmp_tp_packet *)skb->data;
639 
640         /* find the tp_vars */
641         tp_vars = batadv_tp_list_find_session(bat_priv, icmp->orig,
642                                               icmp->session);
643         if (unlikely(!tp_vars))
644                 return;
645 
646         if (unlikely(atomic_read(&tp_vars->sending) == 0))
647                 goto out;
648 
649         /* old ACK? silently drop it.. */
650         if (batadv_seq_before(ntohl(icmp->seqno),
651                               (u32)atomic_read(&tp_vars->last_acked)))
652                 goto out;
653 
654         primary_if = batadv_primary_if_get_selected(bat_priv);
655         if (unlikely(!primary_if))
656                 goto out;
657 
658         orig_node = batadv_orig_hash_find(bat_priv, icmp->orig);
659         if (unlikely(!orig_node))
660                 goto out;
661 
662         /* update RTO with the new sampled RTT, if any */
663         rtt = jiffies_to_msecs(jiffies) - ntohl(icmp->timestamp);
664         if (icmp->timestamp && rtt)
665                 batadv_tp_update_rto(tp_vars, rtt);
666 
667         /* ACK for new data... reset the timer */
668         batadv_tp_reset_sender_timer(tp_vars);
669 
670         recv_ack = ntohl(icmp->seqno);
671 
672         /* check if this ACK is a duplicate */
673         if (atomic_read(&tp_vars->last_acked) == recv_ack) {
674                 atomic_inc(&tp_vars->dup_acks);
675                 if (atomic_read(&tp_vars->dup_acks) != 3)
676                         goto out;
677 
678                 if (recv_ack >= tp_vars->recover)
679                         goto out;
680 
681                 /* if this is the third duplicate ACK do Fast Retransmit */
682                 batadv_tp_send_msg(tp_vars, primary_if->net_dev->dev_addr,
683                                    orig_node, recv_ack, packet_len,
684                                    icmp->session, icmp->uid,
685                                    jiffies_to_msecs(jiffies));
686 
687                 spin_lock_bh(&tp_vars->cwnd_lock);
688 
689                 /* Fast Recovery */
690                 tp_vars->fast_recovery = true;
691                 /* Set recover to the last outstanding seqno when Fast Recovery
692                  * is entered. RFC6582, Section 3.2, step 1
693                  */
694                 tp_vars->recover = tp_vars->last_sent;
695                 tp_vars->ss_threshold = tp_vars->cwnd >> 1;
696                 batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
697                            "Meter: Fast Recovery, (cur cwnd=%u) ss_thr=%u last_sent=%u recv_ack=%u\n",
698                            tp_vars->cwnd, tp_vars->ss_threshold,
699                            tp_vars->last_sent, recv_ack);
700                 tp_vars->cwnd = batadv_tp_cwnd(tp_vars->ss_threshold, 3 * mss,
701                                                mss);
702                 tp_vars->dec_cwnd = 0;
703                 tp_vars->last_sent = recv_ack;
704 
705                 spin_unlock_bh(&tp_vars->cwnd_lock);
706         } else {
707                 /* count the acked data */
708                 atomic64_add(recv_ack - atomic_read(&tp_vars->last_acked),
709                              &tp_vars->tot_sent);
710                 /* reset the duplicate ACKs counter */
711                 atomic_set(&tp_vars->dup_acks, 0);
712 
713                 if (tp_vars->fast_recovery) {
714                         /* partial ACK */
715                         if (batadv_seq_before(recv_ack, tp_vars->recover)) {
716                                 /* this is another hole in the window. React
717                                  * immediately as specified by NewReno (see
718                                  * Section 3.2 of RFC6582 for details)
719                                  */
720                                 dev_addr = primary_if->net_dev->dev_addr;
721                                 batadv_tp_send_msg(tp_vars, dev_addr,
722                                                    orig_node, recv_ack,
723                                                    packet_len, icmp->session,
724                                                    icmp->uid,
725                                                    jiffies_to_msecs(jiffies));
726                                 tp_vars->cwnd = batadv_tp_cwnd(tp_vars->cwnd,
727                                                                mss, mss);
728                         } else {
729                                 tp_vars->fast_recovery = false;
730                                 /* set cwnd to the value of ss_threshold at the
731                                  * moment that Fast Recovery was entered.
732                                  * RFC6582, Section 3.2, step 3
733                                  */
734                                 cwnd = batadv_tp_cwnd(tp_vars->ss_threshold, 0,
735                                                       mss);
736                                 tp_vars->cwnd = cwnd;
737                         }
738                         goto move_twnd;
739                 }
740 
741                 if (recv_ack - atomic_read(&tp_vars->last_acked) >= mss)
742                         batadv_tp_update_cwnd(tp_vars, mss);
743 move_twnd:
744                 /* move the Transmit Window */
745                 atomic_set(&tp_vars->last_acked, recv_ack);
746         }
747 
748         wake_up(&tp_vars->more_bytes);
749 out:
750         if (likely(primary_if))
751                 batadv_hardif_put(primary_if);
752         if (likely(orig_node))
753                 batadv_orig_node_put(orig_node);
754         if (likely(tp_vars))
755                 batadv_tp_vars_put(tp_vars);
756 }
757 
758 /**
759  * batadv_tp_avail() - check if congestion window is not full
760  * @tp_vars: the private data of the current TP meter session
761  * @payload_len: size of the payload of a single message
762  *
763  * Return: true when congestion window is not full, false otherwise
764  */
765 static bool batadv_tp_avail(struct batadv_tp_vars *tp_vars,
766                             size_t payload_len)
767 {
768         u32 win_left, win_limit;
769 
770         win_limit = atomic_read(&tp_vars->last_acked) + tp_vars->cwnd;
771         win_left = win_limit - tp_vars->last_sent;
772 
773         return win_left >= payload_len;
774 }
775 
776 /**
777  * batadv_tp_wait_available() - wait until congestion window becomes free or
778  *  timeout is reached
779  * @tp_vars: the private data of the current TP meter session
780  * @plen: size of the payload of a single message
781  *
782  * Return: 0 if the condition evaluated to false after the timeout elapsed,
783  *  1 if the condition evaluated to true after the timeout elapsed, the
784  *  remaining jiffies (at least 1) if the condition evaluated to true before
785  *  the timeout elapsed, or -ERESTARTSYS if it was interrupted by a signal.
786  */
787 static int batadv_tp_wait_available(struct batadv_tp_vars *tp_vars, size_t plen)
788 {
789         int ret;
790 
791         ret = wait_event_interruptible_timeout(tp_vars->more_bytes,
792                                                batadv_tp_avail(tp_vars, plen),
793                                                HZ / 10);
794 
795         return ret;
796 }
797 
798 /**
799  * batadv_tp_send() - main sending thread of a tp meter session
800  * @arg: address of the related tp_vars
801  *
802  * Return: nothing, this function never returns
803  */
804 static int batadv_tp_send(void *arg)
805 {
806         struct batadv_tp_vars *tp_vars = arg;
807         struct batadv_priv *bat_priv = tp_vars->bat_priv;
808         struct batadv_hard_iface *primary_if = NULL;
809         struct batadv_orig_node *orig_node = NULL;
810         size_t payload_len, packet_len;
811         int err = 0;
812 
813         if (unlikely(tp_vars->role != BATADV_TP_SENDER)) {
814                 err = BATADV_TP_REASON_DST_UNREACHABLE;
815                 tp_vars->reason = err;
816                 goto out;
817         }
818 
819         orig_node = batadv_orig_hash_find(bat_priv, tp_vars->other_end);
820         if (unlikely(!orig_node)) {
821                 err = BATADV_TP_REASON_DST_UNREACHABLE;
822                 tp_vars->reason = err;
823                 goto out;
824         }
825 
826         primary_if = batadv_primary_if_get_selected(bat_priv);
827         if (unlikely(!primary_if)) {
828                 err = BATADV_TP_REASON_DST_UNREACHABLE;
829                 tp_vars->reason = err;
830                 goto out;
831         }
832 
833         /* assume that all the hard_interfaces have a correctly
834          * configured MTU, so use the soft_iface MTU as MSS.
835          * This might not be true and in that case the fragmentation
836          * should be used.
837          * Now, try to send the packet as it is
838          */
839         payload_len = BATADV_TP_PLEN;
840         BUILD_BUG_ON(sizeof(struct batadv_icmp_tp_packet) > BATADV_TP_PLEN);
841 
842         batadv_tp_reset_sender_timer(tp_vars);
843 
844         /* queue the worker in charge of terminating the test */
845         queue_delayed_work(batadv_event_workqueue, &tp_vars->finish_work,
846                            msecs_to_jiffies(tp_vars->test_length));
847 
848         while (atomic_read(&tp_vars->sending) != 0) {
849                 if (unlikely(!batadv_tp_avail(tp_vars, payload_len))) {
850                         batadv_tp_wait_available(tp_vars, payload_len);
851                         continue;
852                 }
853 
854                 /* to emulate normal unicast traffic, add to the payload len
855                  * the size of the unicast header
856                  */
857                 packet_len = payload_len + sizeof(struct batadv_unicast_packet);
858 
859                 err = batadv_tp_send_msg(tp_vars, primary_if->net_dev->dev_addr,
860                                          orig_node, tp_vars->last_sent,
861                                          packet_len,
862                                          tp_vars->session, tp_vars->icmp_uid,
863                                          jiffies_to_msecs(jiffies));
864 
865                 /* something went wrong during the preparation/transmission */
866                 if (unlikely(err && err != BATADV_TP_REASON_CANT_SEND)) {
867                         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
868                                    "Meter: %s() cannot send packets (%d)\n",
869                                    __func__, err);
870                         /* ensure nobody else tries to stop the thread now */
871                         if (atomic_dec_and_test(&tp_vars->sending))
872                                 tp_vars->reason = err;
873                         break;
874                 }
875 
876                 /* right-shift the TWND */
877                 if (!err)
878                         tp_vars->last_sent += payload_len;
879 
880                 cond_resched();
881         }
882 
883 out:
884         if (likely(primary_if))
885                 batadv_hardif_put(primary_if);
886         if (likely(orig_node))
887                 batadv_orig_node_put(orig_node);
888 
889         batadv_tp_sender_end(bat_priv, tp_vars);
890         batadv_tp_sender_cleanup(bat_priv, tp_vars);
891 
892         batadv_tp_vars_put(tp_vars);
893 
894         do_exit(0);
895 }
896 
897 /**
898  * batadv_tp_start_kthread() - start new thread which manages the tp meter
899  *  sender
900  * @tp_vars: the private data of the current TP meter session
901  */
902 static void batadv_tp_start_kthread(struct batadv_tp_vars *tp_vars)
903 {
904         struct task_struct *kthread;
905         struct batadv_priv *bat_priv = tp_vars->bat_priv;
906         u32 session_cookie;
907 
908         kref_get(&tp_vars->refcount);
909         kthread = kthread_create(batadv_tp_send, tp_vars, "kbatadv_tp_meter");
910         if (IS_ERR(kthread)) {
911                 session_cookie = batadv_tp_session_cookie(tp_vars->session,
912                                                           tp_vars->icmp_uid);
913                 pr_err("batadv: cannot create tp meter kthread\n");
914                 batadv_tp_batctl_error_notify(BATADV_TP_REASON_MEMORY_ERROR,
915                                               tp_vars->other_end,
916                                               bat_priv, session_cookie);
917 
918                 /* drop reserved reference for kthread */
919                 batadv_tp_vars_put(tp_vars);
920 
921                 /* cleanup of failed tp meter variables */
922                 batadv_tp_sender_cleanup(bat_priv, tp_vars);
923                 return;
924         }
925 
926         wake_up_process(kthread);
927 }
928 
929 /**
930  * batadv_tp_start() - start a new tp meter session
931  * @bat_priv: the bat priv with all the soft interface information
932  * @dst: the receiver MAC address
933  * @test_length: test length in milliseconds
934  * @cookie: session cookie
935  */
936 void batadv_tp_start(struct batadv_priv *bat_priv, const u8 *dst,
937                      u32 test_length, u32 *cookie)
938 {
939         struct batadv_tp_vars *tp_vars;
940         u8 session_id[2];
941         u8 icmp_uid;
942         u32 session_cookie;
943 
944         get_random_bytes(session_id, sizeof(session_id));
945         get_random_bytes(&icmp_uid, 1);
946         session_cookie = batadv_tp_session_cookie(session_id, icmp_uid);
947         *cookie = session_cookie;
948 
949         /* look for an already existing test towards this node */
950         spin_lock_bh(&bat_priv->tp_list_lock);
951         tp_vars = batadv_tp_list_find(bat_priv, dst);
952         if (tp_vars) {
953                 spin_unlock_bh(&bat_priv->tp_list_lock);
954                 batadv_tp_vars_put(tp_vars);
955                 batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
956                            "Meter: test to or from the same node already ongoing, aborting\n");
957                 batadv_tp_batctl_error_notify(BATADV_TP_REASON_ALREADY_ONGOING,
958                                               dst, bat_priv, session_cookie);
959                 return;
960         }
961 
962         if (!atomic_add_unless(&bat_priv->tp_num, 1, BATADV_TP_MAX_NUM)) {
963                 spin_unlock_bh(&bat_priv->tp_list_lock);
964                 batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
965                            "Meter: too many ongoing sessions, aborting (SEND)\n");
966                 batadv_tp_batctl_error_notify(BATADV_TP_REASON_TOO_MANY, dst,
967                                               bat_priv, session_cookie);
968                 return;
969         }
970 
971         tp_vars = kmalloc(sizeof(*tp_vars), GFP_ATOMIC);
972         if (!tp_vars) {
973                 spin_unlock_bh(&bat_priv->tp_list_lock);
974                 batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
975                            "Meter: %s cannot allocate list elements\n",
976                            __func__);
977                 batadv_tp_batctl_error_notify(BATADV_TP_REASON_MEMORY_ERROR,
978                                               dst, bat_priv, session_cookie);
979                 return;
980         }
981 
982         /* initialize tp_vars */
983         ether_addr_copy(tp_vars->other_end, dst);
984         kref_init(&tp_vars->refcount);
985         tp_vars->role = BATADV_TP_SENDER;
986         atomic_set(&tp_vars->sending, 1);
987         memcpy(tp_vars->session, session_id, sizeof(session_id));
988         tp_vars->icmp_uid = icmp_uid;
989 
990         tp_vars->last_sent = BATADV_TP_FIRST_SEQ;
991         atomic_set(&tp_vars->last_acked, BATADV_TP_FIRST_SEQ);
992         tp_vars->fast_recovery = false;
993         tp_vars->recover = BATADV_TP_FIRST_SEQ;
994 
995         /* initialise the CWND to 3*MSS (Section 3.1 in RFC5681).
996          * For batman-adv the MSS is the size of the payload received by the
997          * soft_interface, hence its MTU
998          */
999         tp_vars->cwnd = BATADV_TP_PLEN * 3;
1000         /* at the beginning initialise the SS threshold to the biggest possible
1001          * window size, hence the AWND size
1002          */
1003         tp_vars->ss_threshold = BATADV_TP_AWND;
1004 
1005         /* RTO initial value is 3 seconds.
1006          * Details in Section 2.1 of RFC6298
1007          */
1008         tp_vars->rto = 1000;
1009         tp_vars->srtt = 0;
1010         tp_vars->rttvar = 0;
1011 
1012         atomic64_set(&tp_vars->tot_sent, 0);
1013 
1014         kref_get(&tp_vars->refcount);
1015         timer_setup(&tp_vars->timer, batadv_tp_sender_timeout, 0);
1016 
1017         tp_vars->bat_priv = bat_priv;
1018         tp_vars->start_time = jiffies;
1019 
1020         init_waitqueue_head(&tp_vars->more_bytes);
1021 
1022         spin_lock_init(&tp_vars->unacked_lock);
1023         INIT_LIST_HEAD(&tp_vars->unacked_list);
1024 
1025         spin_lock_init(&tp_vars->cwnd_lock);
1026 
1027         tp_vars->prerandom_offset = 0;
1028         spin_lock_init(&tp_vars->prerandom_lock);
1029 
1030         kref_get(&tp_vars->refcount);
1031         hlist_add_head_rcu(&tp_vars->list, &bat_priv->tp_list);
1032         spin_unlock_bh(&bat_priv->tp_list_lock);
1033 
1034         tp_vars->test_length = test_length;
1035         if (!tp_vars->test_length)
1036                 tp_vars->test_length = BATADV_TP_DEF_TEST_LENGTH;
1037 
1038         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
1039                    "Meter: starting throughput meter towards %pM (length=%ums)\n",
1040                    dst, test_length);
1041 
1042         /* init work item for finished tp tests */
1043         INIT_DELAYED_WORK(&tp_vars->finish_work, batadv_tp_sender_finish);
1044 
1045         /* start tp kthread. This way the write() call issued from userspace can
1046          * happily return and avoid to block
1047          */
1048         batadv_tp_start_kthread(tp_vars);
1049 
1050         /* don't return reference to new tp_vars */
1051         batadv_tp_vars_put(tp_vars);
1052 }
1053 
1054 /**
1055  * batadv_tp_stop() - stop currently running tp meter session
1056  * @bat_priv: the bat priv with all the soft interface information
1057  * @dst: the receiver MAC address
1058  * @return_value: reason for tp meter session stop
1059  */
1060 void batadv_tp_stop(struct batadv_priv *bat_priv, const u8 *dst,
1061                     u8 return_value)
1062 {
1063         struct batadv_orig_node *orig_node;
1064         struct batadv_tp_vars *tp_vars;
1065 
1066         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
1067                    "Meter: stopping test towards %pM\n", dst);
1068 
1069         orig_node = batadv_orig_hash_find(bat_priv, dst);
1070         if (!orig_node)
1071                 return;
1072 
1073         tp_vars = batadv_tp_list_find(bat_priv, orig_node->orig);
1074         if (!tp_vars) {
1075                 batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
1076                            "Meter: trying to interrupt an already over connection\n");
1077                 goto out;
1078         }
1079 
1080         batadv_tp_sender_shutdown(tp_vars, return_value);
1081         batadv_tp_vars_put(tp_vars);
1082 out:
1083         batadv_orig_node_put(orig_node);
1084 }
1085 
1086 /**
1087  * batadv_tp_reset_receiver_timer() - reset the receiver shutdown timer
1088  * @tp_vars: the private data of the current TP meter session
1089  *
1090  * start the receiver shutdown timer or reset it if already started
1091  */
1092 static void batadv_tp_reset_receiver_timer(struct batadv_tp_vars *tp_vars)
1093 {
1094         mod_timer(&tp_vars->timer,
1095                   jiffies + msecs_to_jiffies(BATADV_TP_RECV_TIMEOUT));
1096 }
1097 
1098 /**
1099  * batadv_tp_receiver_shutdown() - stop a tp meter receiver when timeout is
1100  *  reached without received ack
1101  * @t: address to timer_list inside tp_vars
1102  */
1103 static void batadv_tp_receiver_shutdown(struct timer_list *t)
1104 {
1105         struct batadv_tp_vars *tp_vars = from_timer(tp_vars, t, timer);
1106         struct batadv_tp_unacked *un, *safe;
1107         struct batadv_priv *bat_priv;
1108 
1109         bat_priv = tp_vars->bat_priv;
1110 
1111         /* if there is recent activity rearm the timer */
1112         if (!batadv_has_timed_out(tp_vars->last_recv_time,
1113                                   BATADV_TP_RECV_TIMEOUT)) {
1114                 /* reset the receiver shutdown timer */
1115                 batadv_tp_reset_receiver_timer(tp_vars);
1116                 return;
1117         }
1118 
1119         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
1120                    "Shutting down for inactivity (more than %dms) from %pM\n",
1121                    BATADV_TP_RECV_TIMEOUT, tp_vars->other_end);
1122 
1123         spin_lock_bh(&tp_vars->bat_priv->tp_list_lock);
1124         hlist_del_rcu(&tp_vars->list);
1125         spin_unlock_bh(&tp_vars->bat_priv->tp_list_lock);
1126 
1127         /* drop list reference */
1128         batadv_tp_vars_put(tp_vars);
1129 
1130         atomic_dec(&bat_priv->tp_num);
1131 
1132         spin_lock_bh(&tp_vars->unacked_lock);
1133         list_for_each_entry_safe(un, safe, &tp_vars->unacked_list, list) {
1134                 list_del(&un->list);
1135                 kfree(un);
1136         }
1137         spin_unlock_bh(&tp_vars->unacked_lock);
1138 
1139         /* drop reference of timer */
1140         batadv_tp_vars_put(tp_vars);
1141 }
1142 
1143 /**
1144  * batadv_tp_send_ack() - send an ACK packet
1145  * @bat_priv: the bat priv with all the soft interface information
1146  * @dst: the mac address of the destination originator
1147  * @seq: the sequence number to ACK
1148  * @timestamp: the timestamp to echo back in the ACK
1149  * @session: session identifier
1150  * @socket_index: local ICMP socket identifier
1151  *
1152  * Return: 0 on success, a positive integer representing the reason of the
1153  * failure otherwise
1154  */
1155 static int batadv_tp_send_ack(struct batadv_priv *bat_priv, const u8 *dst,
1156                               u32 seq, __be32 timestamp, const u8 *session,
1157                               int socket_index)
1158 {
1159         struct batadv_hard_iface *primary_if = NULL;
1160         struct batadv_orig_node *orig_node;
1161         struct batadv_icmp_tp_packet *icmp;
1162         struct sk_buff *skb;
1163         int r, ret;
1164 
1165         orig_node = batadv_orig_hash_find(bat_priv, dst);
1166         if (unlikely(!orig_node)) {
1167                 ret = BATADV_TP_REASON_DST_UNREACHABLE;
1168                 goto out;
1169         }
1170 
1171         primary_if = batadv_primary_if_get_selected(bat_priv);
1172         if (unlikely(!primary_if)) {
1173                 ret = BATADV_TP_REASON_DST_UNREACHABLE;
1174                 goto out;
1175         }
1176 
1177         skb = netdev_alloc_skb_ip_align(NULL, sizeof(*icmp) + ETH_HLEN);
1178         if (unlikely(!skb)) {
1179                 ret = BATADV_TP_REASON_MEMORY_ERROR;
1180                 goto out;
1181         }
1182 
1183         skb_reserve(skb, ETH_HLEN);
1184         icmp = skb_put(skb, sizeof(*icmp));
1185         icmp->packet_type = BATADV_ICMP;
1186         icmp->version = BATADV_COMPAT_VERSION;
1187         icmp->ttl = BATADV_TTL;
1188         icmp->msg_type = BATADV_TP;
1189         ether_addr_copy(icmp->dst, orig_node->orig);
1190         ether_addr_copy(icmp->orig, primary_if->net_dev->dev_addr);
1191         icmp->uid = socket_index;
1192 
1193         icmp->subtype = BATADV_TP_ACK;
1194         memcpy(icmp->session, session, sizeof(icmp->session));
1195         icmp->seqno = htonl(seq);
1196         icmp->timestamp = timestamp;
1197 
1198         /* send the ack */
1199         r = batadv_send_skb_to_orig(skb, orig_node, NULL);
1200         if (unlikely(r < 0) || r == NET_XMIT_DROP) {
1201                 ret = BATADV_TP_REASON_DST_UNREACHABLE;
1202                 goto out;
1203         }
1204         ret = 0;
1205 
1206 out:
1207         if (likely(orig_node))
1208                 batadv_orig_node_put(orig_node);
1209         if (likely(primary_if))
1210                 batadv_hardif_put(primary_if);
1211 
1212         return ret;
1213 }
1214 
1215 /**
1216  * batadv_tp_handle_out_of_order() - store an out of order packet
1217  * @tp_vars: the private data of the current TP meter session
1218  * @skb: the buffer containing the received packet
1219  *
1220  * Store the out of order packet in the unacked list for late processing. This
1221  * packets are kept in this list so that they can be ACKed at once as soon as
1222  * all the previous packets have been received
1223  *
1224  * Return: true if the packed has been successfully processed, false otherwise
1225  */
1226 static bool batadv_tp_handle_out_of_order(struct batadv_tp_vars *tp_vars,
1227                                           const struct sk_buff *skb)
1228 {
1229         const struct batadv_icmp_tp_packet *icmp;
1230         struct batadv_tp_unacked *un, *new;
1231         u32 payload_len;
1232         bool added = false;
1233 
1234         new = kmalloc(sizeof(*new), GFP_ATOMIC);
1235         if (unlikely(!new))
1236                 return false;
1237 
1238         icmp = (struct batadv_icmp_tp_packet *)skb->data;
1239 
1240         new->seqno = ntohl(icmp->seqno);
1241         payload_len = skb->len - sizeof(struct batadv_unicast_packet);
1242         new->len = payload_len;
1243 
1244         spin_lock_bh(&tp_vars->unacked_lock);
1245         /* if the list is empty immediately attach this new object */
1246         if (list_empty(&tp_vars->unacked_list)) {
1247                 list_add(&new->list, &tp_vars->unacked_list);
1248                 goto out;
1249         }
1250 
1251         /* otherwise loop over the list and either drop the packet because this
1252          * is a duplicate or store it at the right position.
1253          *
1254          * The iteration is done in the reverse way because it is likely that
1255          * the last received packet (the one being processed now) has a bigger
1256          * seqno than all the others already stored.
1257          */
1258         list_for_each_entry_reverse(un, &tp_vars->unacked_list, list) {
1259                 /* check for duplicates */
1260                 if (new->seqno == un->seqno) {
1261                         if (new->len > un->len)
1262                                 un->len = new->len;
1263                         kfree(new);
1264                         added = true;
1265                         break;
1266                 }
1267 
1268                 /* look for the right position */
1269                 if (batadv_seq_before(new->seqno, un->seqno))
1270                         continue;
1271 
1272                 /* as soon as an entry having a bigger seqno is found, the new
1273                  * one is attached _after_ it. In this way the list is kept in
1274                  * ascending order
1275                  */
1276                 list_add_tail(&new->list, &un->list);
1277                 added = true;
1278                 break;
1279         }
1280 
1281         /* received packet with smallest seqno out of order; add it to front */
1282         if (!added)
1283                 list_add(&new->list, &tp_vars->unacked_list);
1284 
1285 out:
1286         spin_unlock_bh(&tp_vars->unacked_lock);
1287 
1288         return true;
1289 }
1290 
1291 /**
1292  * batadv_tp_ack_unordered() - update number received bytes in current stream
1293  *  without gaps
1294  * @tp_vars: the private data of the current TP meter session
1295  */
1296 static void batadv_tp_ack_unordered(struct batadv_tp_vars *tp_vars)
1297 {
1298         struct batadv_tp_unacked *un, *safe;
1299         u32 to_ack;
1300 
1301         /* go through the unacked packet list and possibly ACK them as
1302          * well
1303          */
1304         spin_lock_bh(&tp_vars->unacked_lock);
1305         list_for_each_entry_safe(un, safe, &tp_vars->unacked_list, list) {
1306                 /* the list is ordered, therefore it is possible to stop as soon
1307                  * there is a gap between the last acked seqno and the seqno of
1308                  * the packet under inspection
1309                  */
1310                 if (batadv_seq_before(tp_vars->last_recv, un->seqno))
1311                         break;
1312 
1313                 to_ack = un->seqno + un->len - tp_vars->last_recv;
1314 
1315                 if (batadv_seq_before(tp_vars->last_recv, un->seqno + un->len))
1316                         tp_vars->last_recv += to_ack;
1317 
1318                 list_del(&un->list);
1319                 kfree(un);
1320         }
1321         spin_unlock_bh(&tp_vars->unacked_lock);
1322 }
1323 
1324 /**
1325  * batadv_tp_init_recv() - return matching or create new receiver tp_vars
1326  * @bat_priv: the bat priv with all the soft interface information
1327  * @icmp: received icmp tp msg
1328  *
1329  * Return: corresponding tp_vars or NULL on errors
1330  */
1331 static struct batadv_tp_vars *
1332 batadv_tp_init_recv(struct batadv_priv *bat_priv,
1333                     const struct batadv_icmp_tp_packet *icmp)
1334 {
1335         struct batadv_tp_vars *tp_vars;
1336 
1337         spin_lock_bh(&bat_priv->tp_list_lock);
1338         tp_vars = batadv_tp_list_find_session(bat_priv, icmp->orig,
1339                                               icmp->session);
1340         if (tp_vars)
1341                 goto out_unlock;
1342 
1343         if (!atomic_add_unless(&bat_priv->tp_num, 1, BATADV_TP_MAX_NUM)) {
1344                 batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
1345                            "Meter: too many ongoing sessions, aborting (RECV)\n");
1346                 goto out_unlock;
1347         }
1348 
1349         tp_vars = kmalloc(sizeof(*tp_vars), GFP_ATOMIC);
1350         if (!tp_vars)
1351                 goto out_unlock;
1352 
1353         ether_addr_copy(tp_vars->other_end, icmp->orig);
1354         tp_vars->role = BATADV_TP_RECEIVER;
1355         memcpy(tp_vars->session, icmp->session, sizeof(tp_vars->session));
1356         tp_vars->last_recv = BATADV_TP_FIRST_SEQ;
1357         tp_vars->bat_priv = bat_priv;
1358         kref_init(&tp_vars->refcount);
1359 
1360         spin_lock_init(&tp_vars->unacked_lock);
1361         INIT_LIST_HEAD(&tp_vars->unacked_list);
1362 
1363         kref_get(&tp_vars->refcount);
1364         hlist_add_head_rcu(&tp_vars->list, &bat_priv->tp_list);
1365 
1366         kref_get(&tp_vars->refcount);
1367         timer_setup(&tp_vars->timer, batadv_tp_receiver_shutdown, 0);
1368 
1369         batadv_tp_reset_receiver_timer(tp_vars);
1370 
1371 out_unlock:
1372         spin_unlock_bh(&bat_priv->tp_list_lock);
1373 
1374         return tp_vars;
1375 }
1376 
1377 /**
1378  * batadv_tp_recv_msg() - process a single data message
1379  * @bat_priv: the bat priv with all the soft interface information
1380  * @skb: the buffer containing the received packet
1381  *
1382  * Process a received TP MSG packet
1383  */
1384 static void batadv_tp_recv_msg(struct batadv_priv *bat_priv,
1385                                const struct sk_buff *skb)
1386 {
1387         const struct batadv_icmp_tp_packet *icmp;
1388         struct batadv_tp_vars *tp_vars;
1389         size_t packet_size;
1390         u32 seqno;
1391 
1392         icmp = (struct batadv_icmp_tp_packet *)skb->data;
1393 
1394         seqno = ntohl(icmp->seqno);
1395         /* check if this is the first seqno. This means that if the
1396          * first packet is lost, the tp meter does not work anymore!
1397          */
1398         if (seqno == BATADV_TP_FIRST_SEQ) {
1399                 tp_vars = batadv_tp_init_recv(bat_priv, icmp);
1400                 if (!tp_vars) {
1401                         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
1402                                    "Meter: seqno != BATADV_TP_FIRST_SEQ cannot initiate connection\n");
1403                         goto out;
1404                 }
1405         } else {
1406                 tp_vars = batadv_tp_list_find_session(bat_priv, icmp->orig,
1407                                                       icmp->session);
1408                 if (!tp_vars) {
1409                         batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
1410                                    "Unexpected packet from %pM!\n",
1411                                    icmp->orig);
1412                         goto out;
1413                 }
1414         }
1415 
1416         if (unlikely(tp_vars->role != BATADV_TP_RECEIVER)) {
1417                 batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
1418                            "Meter: dropping packet: not expected (role=%u)\n",
1419                            tp_vars->role);
1420                 goto out;
1421         }
1422 
1423         tp_vars->last_recv_time = jiffies;
1424 
1425         /* if the packet is a duplicate, it may be the case that an ACK has been
1426          * lost. Resend the ACK
1427          */
1428         if (batadv_seq_before(seqno, tp_vars->last_recv))
1429                 goto send_ack;
1430 
1431         /* if the packet is out of order enqueue it */
1432         if (ntohl(icmp->seqno) != tp_vars->last_recv) {
1433                 /* exit immediately (and do not send any ACK) if the packet has
1434                  * not been enqueued correctly
1435                  */
1436                 if (!batadv_tp_handle_out_of_order(tp_vars, skb))
1437                         goto out;
1438 
1439                 /* send a duplicate ACK */
1440                 goto send_ack;
1441         }
1442 
1443         /* if everything was fine count the ACKed bytes */
1444         packet_size = skb->len - sizeof(struct batadv_unicast_packet);
1445         tp_vars->last_recv += packet_size;
1446 
1447         /* check if this ordered message filled a gap.... */
1448         batadv_tp_ack_unordered(tp_vars);
1449 
1450 send_ack:
1451         /* send the ACK. If the received packet was out of order, the ACK that
1452          * is going to be sent is a duplicate (the sender will count them and
1453          * possibly enter Fast Retransmit as soon as it has reached 3)
1454          */
1455         batadv_tp_send_ack(bat_priv, icmp->orig, tp_vars->last_recv,
1456                            icmp->timestamp, icmp->session, icmp->uid);
1457 out:
1458         if (likely(tp_vars))
1459                 batadv_tp_vars_put(tp_vars);
1460 }
1461 
1462 /**
1463  * batadv_tp_meter_recv() - main TP Meter receiving function
1464  * @bat_priv: the bat priv with all the soft interface information
1465  * @skb: the buffer containing the received packet
1466  */
1467 void batadv_tp_meter_recv(struct batadv_priv *bat_priv, struct sk_buff *skb)
1468 {
1469         struct batadv_icmp_tp_packet *icmp;
1470 
1471         icmp = (struct batadv_icmp_tp_packet *)skb->data;
1472 
1473         switch (icmp->subtype) {
1474         case BATADV_TP_MSG:
1475                 batadv_tp_recv_msg(bat_priv, skb);
1476                 break;
1477         case BATADV_TP_ACK:
1478                 batadv_tp_recv_ack(bat_priv, skb);
1479                 break;
1480         default:
1481                 batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
1482                            "Received unknown TP Metric packet type %u\n",
1483                            icmp->subtype);
1484         }
1485         consume_skb(skb);
1486 }
1487 
1488 /**
1489  * batadv_tp_meter_init() - initialize global tp_meter structures
1490  */
1491 void __init batadv_tp_meter_init(void)
1492 {
1493         get_random_bytes(batadv_tp_prerandom, sizeof(batadv_tp_prerandom));
1494 }
1495 

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