2 This file is part of GNUnet
3 Copyright (C) 2009-2013 Christian Grothoff (and other contributing authors)
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6 it under the terms of the GNU General Public License as published
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
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21 * @file src/fragmentation/fragmentation.c
22 * @brief library to help fragment messages
23 * @author Christian Grothoff
26 #include "gnunet_fragmentation_lib.h"
27 #include "gnunet_protocols.h"
28 #include "fragmentation.h"
32 * Absolute minimum delay we impose between sending and expecting ACK to arrive.
34 #define MIN_ACK_DELAY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS, 1)
38 * Fragmentation context.
40 struct GNUNET_FRAGMENT_Context
45 struct GNUNET_STATISTICS_Handle *stats;
48 * Tracker for flow control.
50 struct GNUNET_BANDWIDTH_Tracker *tracker;
53 * Current expected delay for ACKs.
55 struct GNUNET_TIME_Relative ack_delay;
58 * Current expected delay between messages.
60 struct GNUNET_TIME_Relative msg_delay;
63 * Next allowed transmission time.
65 struct GNUNET_TIME_Absolute delay_until;
68 * Time we transmitted the last message of the last round.
70 struct GNUNET_TIME_Absolute last_round;
73 * Message to fragment (allocated at the end of this struct).
75 const struct GNUNET_MessageHeader *msg;
78 * Function to call for transmissions.
80 GNUNET_FRAGMENT_MessageProcessor proc;
83 * Closure for @e proc.
88 * Bitfield, set to 1 for each unacknowledged fragment.
93 * Bitfield with all possible bits for @e acks (used to mask the
99 * Task performing work for the fragmenter.
101 struct GNUNET_SCHEDULER_Task *task;
104 * Our fragmentation ID. (chosen at random)
106 uint32_t fragment_id;
109 * Round-robin selector for the next transmission.
111 unsigned int next_transmission;
114 * How many rounds of transmission have we completed so far?
116 unsigned int num_rounds;
119 * How many transmission have we completed in this round?
121 unsigned int num_transmissions;
124 * #GNUNET_YES if we called @e proc and are now waiting for #GNUNET_FRAGMENT_context_transmission_done()
129 * #GNUNET_YES if we are waiting for an ACK.
134 * Target fragment size.
142 * Convert an ACK message to a printable format suitable for logging.
144 * @param ack message to print
145 * @return ack in human-readable format
148 GNUNET_FRAGMENT_print_ack (const struct GNUNET_MessageHeader *ack)
150 static char buf[128];
151 const struct FragmentAcknowledgement *fa;
153 if (sizeof (struct FragmentAcknowledgement) !=
155 return "<malformed ack>";
156 fa = (const struct FragmentAcknowledgement *) ack;
157 GNUNET_snprintf (buf,
160 ntohl (fa->fragment_id),
161 GNUNET_ntohll (fa->bits));
167 * Transmit the next fragment to the other peer.
169 * @param cls the `struct GNUNET_FRAGMENT_Context`
170 * @param tc scheduler context
173 transmit_next (void *cls,
174 const struct GNUNET_SCHEDULER_TaskContext *tc)
176 struct GNUNET_FRAGMENT_Context *fc = cls;
179 struct FragmentHeader *fh;
180 struct GNUNET_TIME_Relative delay;
187 GNUNET_assert (GNUNET_NO == fc->proc_busy);
189 return; /* all done */
190 /* calculate delay */
192 while (0 == (fc->acks & (1LL << fc->next_transmission)))
194 fc->next_transmission = (fc->next_transmission + 1) % 64;
195 wrap |= (0 == fc->next_transmission);
197 bit = fc->next_transmission;
198 size = ntohs (fc->msg->size);
199 if (bit == size / (fc->mtu - sizeof (struct FragmentHeader)))
201 (size % (fc->mtu - sizeof (struct FragmentHeader))) +
202 sizeof (struct FragmentHeader);
205 if (NULL != fc->tracker)
206 delay = GNUNET_BANDWIDTH_tracker_get_delay (fc->tracker,
209 delay = GNUNET_TIME_UNIT_ZERO;
210 if (delay.rel_value_us > 0)
212 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
213 "Fragmentation logic delays transmission of next fragment by %s\n",
214 GNUNET_STRINGS_relative_time_to_string (delay,
216 fc->task = GNUNET_SCHEDULER_add_delayed (delay,
221 fc->next_transmission = (fc->next_transmission + 1) % 64;
222 wrap |= (0 == fc->next_transmission);
223 while (0 == (fc->acks & (1LL << fc->next_transmission)))
225 fc->next_transmission = (fc->next_transmission + 1) % 64;
226 wrap |= (0 == fc->next_transmission);
229 /* assemble fragmentation message */
230 mbuf = (const char *) &fc[1];
231 fh = (struct FragmentHeader *) msg;
232 fh->header.size = htons (fsize);
233 fh->header.type = htons (GNUNET_MESSAGE_TYPE_FRAGMENT);
234 fh->fragment_id = htonl (fc->fragment_id);
235 fh->total_size = fc->msg->size; /* already in big-endian */
236 fh->offset = htons ((fc->mtu - sizeof (struct FragmentHeader)) * bit);
237 memcpy (&fh[1], &mbuf[bit * (fc->mtu - sizeof (struct FragmentHeader))],
238 fsize - sizeof (struct FragmentHeader));
239 if (NULL != fc->tracker)
240 GNUNET_BANDWIDTH_tracker_consume (fc->tracker, fsize);
241 GNUNET_STATISTICS_update (fc->stats,
242 _("# fragments transmitted"),
245 if (0 != fc->last_round.abs_value_us)
246 GNUNET_STATISTICS_update (fc->stats,
247 _("# fragments retransmitted"),
251 /* select next message to calculate delay */
252 bit = fc->next_transmission;
253 size = ntohs (fc->msg->size);
254 if (bit == size / (fc->mtu - sizeof (struct FragmentHeader)))
255 fsize = size % (fc->mtu - sizeof (struct FragmentHeader));
258 if (NULL != fc->tracker)
259 delay = GNUNET_BANDWIDTH_tracker_get_delay (fc->tracker,
262 delay = GNUNET_TIME_UNIT_ZERO;
263 delay = GNUNET_TIME_relative_max (delay,
264 GNUNET_TIME_relative_multiply (fc->msg_delay,
265 (1 << fc->num_rounds)));
268 /* full round transmitted wait 2x delay for ACK before going again */
270 delay = GNUNET_TIME_relative_multiply (fc->ack_delay, 2);
271 /* never use zero, need some time for ACK always */
272 delay = GNUNET_TIME_relative_max (MIN_ACK_DELAY, delay);
273 fc->wack = GNUNET_YES;
274 fc->last_round = GNUNET_TIME_absolute_get ();
275 GNUNET_STATISTICS_update (fc->stats,
276 _("# fragments wrap arounds"),
280 fc->proc_busy = GNUNET_YES;
281 fc->delay_until = GNUNET_TIME_relative_to_absolute (delay);
282 fc->num_transmissions++;
283 fc->proc (fc->proc_cls,
289 * Create a fragmentation context for the given message.
290 * Fragments the message into fragments of size @a mtu or
291 * less. Calls @a proc on each un-acknowledged fragment,
292 * using both the expected @a msg_delay between messages and
293 * acknowledgements and the given @a tracker to guide the
294 * frequency of calls to @a proc.
296 * @param stats statistics context
297 * @param mtu the maximum message size for each fragment
298 * @param tracker bandwidth tracker to use for flow control (can be NULL)
299 * @param msg_delay initial delay to insert between fragment transmissions
300 * based on previous messages
301 * @param ack_delay expected delay between fragment transmission
302 * and ACK based on previous messages
303 * @param msg the message to fragment
304 * @param proc function to call for each fragment to transmit
305 * @param proc_cls closure for @a proc
306 * @return the fragmentation context
308 struct GNUNET_FRAGMENT_Context *
309 GNUNET_FRAGMENT_context_create (struct GNUNET_STATISTICS_Handle *stats,
311 struct GNUNET_BANDWIDTH_Tracker *tracker,
312 struct GNUNET_TIME_Relative msg_delay,
313 struct GNUNET_TIME_Relative ack_delay,
314 const struct GNUNET_MessageHeader *msg,
315 GNUNET_FRAGMENT_MessageProcessor proc,
318 struct GNUNET_FRAGMENT_Context *fc;
322 GNUNET_STATISTICS_update (stats,
323 _("# messages fragmented"),
326 GNUNET_assert (mtu >= 1024 + sizeof (struct FragmentHeader));
327 size = ntohs (msg->size);
328 GNUNET_STATISTICS_update (stats,
329 _("# total size of fragmented messages"),
331 GNUNET_assert (size >= sizeof (struct GNUNET_MessageHeader));
332 fc = GNUNET_malloc (sizeof (struct GNUNET_FRAGMENT_Context) + size);
335 fc->tracker = tracker;
336 fc->ack_delay = ack_delay;
337 fc->msg_delay = msg_delay;
338 fc->msg = (const struct GNUNET_MessageHeader *) &fc[1];
340 fc->proc_cls = proc_cls;
342 GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
344 memcpy (&fc[1], msg, size);
346 (size + mtu - sizeof (struct FragmentHeader) - 1) / (mtu -
349 GNUNET_assert (bits <= 64);
351 fc->acks_mask = UINT64_MAX; /* set all 64 bit */
353 fc->acks_mask = (1LL << bits) - 1; /* set lowest 'bits' bit */
354 fc->acks = fc->acks_mask;
355 fc->task = GNUNET_SCHEDULER_add_now (&transmit_next, fc);
361 * Continuation to call from the 'proc' function after the fragment
362 * has been transmitted (and hence the next fragment can now be
365 * @param fc fragmentation context
368 GNUNET_FRAGMENT_context_transmission_done (struct GNUNET_FRAGMENT_Context *fc)
370 GNUNET_assert (fc->proc_busy == GNUNET_YES);
371 fc->proc_busy = GNUNET_NO;
372 GNUNET_assert (fc->task == NULL);
374 GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_absolute_get_remaining
375 (fc->delay_until), &transmit_next, fc);
380 * Process an acknowledgement message we got from the other
381 * side (to control re-transmits).
383 * @param fc fragmentation context
384 * @param msg acknowledgement message we received
385 * @return #GNUNET_OK if this ack completes the work of the 'fc'
386 * (all fragments have been received);
387 * #GNUNET_NO if more messages are pending
388 * #GNUNET_SYSERR if this ack is not valid for this fc
391 GNUNET_FRAGMENT_process_ack (struct GNUNET_FRAGMENT_Context *fc,
392 const struct GNUNET_MessageHeader *msg)
394 const struct FragmentAcknowledgement *fa;
396 struct GNUNET_TIME_Relative ndelay;
397 unsigned int ack_cnt;
398 unsigned int snd_cnt;
401 if (sizeof (struct FragmentAcknowledgement) != ntohs (msg->size))
404 return GNUNET_SYSERR;
406 fa = (const struct FragmentAcknowledgement *) msg;
407 if (ntohl (fa->fragment_id) != fc->fragment_id)
408 return GNUNET_SYSERR; /* not our ACK */
409 abits = GNUNET_ntohll (fa->bits);
410 if ( (GNUNET_YES == fc->wack) &&
411 (0 != fc->num_transmissions) )
413 /* normal ACK, can update running average of delay... */
414 fc->wack = GNUNET_NO;
415 ndelay = GNUNET_TIME_absolute_get_duration (fc->last_round);
416 fc->ack_delay.rel_value_us =
417 (ndelay.rel_value_us / fc->num_transmissions + 3 * fc->ack_delay.rel_value_us) / 4;
418 /* calculate ratio msg sent vs. msg acked */
423 if (1 == (fc->acks_mask & (1 << i)))
426 if (0 == (abits & (1 << i)))
433 fc->msg_delay = GNUNET_TIME_relative_multiply (fc->msg_delay,
436 else if (snd_cnt > ack_cnt)
438 /* some loss, slow down proportionally */
439 fc->msg_delay.rel_value_us = ((fc->msg_delay.rel_value_us * ack_cnt) / snd_cnt);
441 else if (snd_cnt == ack_cnt)
443 fc->msg_delay.rel_value_us =
444 (ndelay.rel_value_us / fc->num_transmissions + 3 * fc->msg_delay.rel_value_us) / 5;
446 fc->num_transmissions = 0;
447 fc->msg_delay = GNUNET_TIME_relative_min (fc->msg_delay,
448 GNUNET_TIME_UNIT_SECONDS);
449 fc->ack_delay = GNUNET_TIME_relative_min (fc->ack_delay,
450 GNUNET_TIME_UNIT_SECONDS);
452 GNUNET_STATISTICS_update (fc->stats,
453 _("# fragment acknowledgements received"),
456 if (abits != (fc->acks & abits))
458 /* ID collission or message reordering, count! This should be rare! */
459 GNUNET_STATISTICS_update (fc->stats,
460 _("# bits removed from fragmentation ACKs"), 1,
463 fc->acks = abits & fc->acks_mask;
466 /* more to transmit, do so right now (if tracker permits...) */
467 if (fc->task != NULL)
469 /* schedule next transmission now, no point in waiting... */
470 GNUNET_SCHEDULER_cancel (fc->task);
471 fc->task = GNUNET_SCHEDULER_add_now (&transmit_next, fc);
475 /* only case where there is no task should be if we're waiting
476 * for the right to transmit again (proc_busy set to YES) */
477 GNUNET_assert (GNUNET_YES == fc->proc_busy);
483 GNUNET_STATISTICS_update (fc->stats,
484 _("# fragmentation transmissions completed"),
487 if (NULL != fc->task)
489 GNUNET_SCHEDULER_cancel (fc->task);
497 * Destroy the given fragmentation context (stop calling 'proc', free
500 * @param fc fragmentation context
501 * @param msg_delay where to store average delay between individual message transmissions the
502 * last message (OUT only)
503 * @param ack_delay where to store average delay between transmission and ACK for the
504 * last message, set to FOREVER if the message was not fully transmitted (OUT only)
507 GNUNET_FRAGMENT_context_destroy (struct GNUNET_FRAGMENT_Context *fc,
508 struct GNUNET_TIME_Relative *msg_delay,
509 struct GNUNET_TIME_Relative *ack_delay)
511 if (fc->task != NULL)
512 GNUNET_SCHEDULER_cancel (fc->task);
513 if (NULL != ack_delay)
514 *ack_delay = fc->ack_delay;
515 if (NULL != msg_delay)
516 *msg_delay = GNUNET_TIME_relative_multiply (fc->msg_delay,
522 /* end of fragmentation.c */