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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`
172 transmit_next (void *cls)
174 struct GNUNET_FRAGMENT_Context *fc = cls;
177 struct FragmentHeader *fh;
178 struct GNUNET_TIME_Relative delay;
185 GNUNET_assert (GNUNET_NO == fc->proc_busy);
187 return; /* all done */
188 /* calculate delay */
190 while (0 == (fc->acks & (1LLU << fc->next_transmission)))
192 fc->next_transmission = (fc->next_transmission + 1) % 64;
193 wrap |= (0 == fc->next_transmission);
195 bit = fc->next_transmission;
196 size = ntohs (fc->msg->size);
197 if (bit == size / (fc->mtu - sizeof (struct FragmentHeader)))
199 (size % (fc->mtu - sizeof (struct FragmentHeader))) +
200 sizeof (struct FragmentHeader);
203 if (NULL != fc->tracker)
204 delay = GNUNET_BANDWIDTH_tracker_get_delay (fc->tracker,
207 delay = GNUNET_TIME_UNIT_ZERO;
208 if (delay.rel_value_us > 0)
210 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
211 "Fragmentation logic delays transmission of next fragment by %s\n",
212 GNUNET_STRINGS_relative_time_to_string (delay,
214 fc->task = GNUNET_SCHEDULER_add_delayed (delay,
219 fc->next_transmission = (fc->next_transmission + 1) % 64;
220 wrap |= (0 == fc->next_transmission);
221 while (0 == (fc->acks & (1LLU << fc->next_transmission)))
223 fc->next_transmission = (fc->next_transmission + 1) % 64;
224 wrap |= (0 == fc->next_transmission);
227 /* assemble fragmentation message */
228 mbuf = (const char *) &fc[1];
229 fh = (struct FragmentHeader *) msg;
230 fh->header.size = htons (fsize);
231 fh->header.type = htons (GNUNET_MESSAGE_TYPE_FRAGMENT);
232 fh->fragment_id = htonl (fc->fragment_id);
233 fh->total_size = fc->msg->size; /* already in big-endian */
234 fh->offset = htons ((fc->mtu - sizeof (struct FragmentHeader)) * bit);
235 GNUNET_memcpy (&fh[1], &mbuf[bit * (fc->mtu - sizeof (struct FragmentHeader))],
236 fsize - sizeof (struct FragmentHeader));
237 if (NULL != fc->tracker)
238 GNUNET_BANDWIDTH_tracker_consume (fc->tracker, fsize);
239 GNUNET_STATISTICS_update (fc->stats,
240 _("# fragments transmitted"),
243 if (0 != fc->last_round.abs_value_us)
244 GNUNET_STATISTICS_update (fc->stats,
245 _("# fragments retransmitted"),
249 /* select next message to calculate delay */
250 bit = fc->next_transmission;
251 size = ntohs (fc->msg->size);
252 if (bit == size / (fc->mtu - sizeof (struct FragmentHeader)))
253 fsize = size % (fc->mtu - sizeof (struct FragmentHeader));
256 if (NULL != fc->tracker)
257 delay = GNUNET_BANDWIDTH_tracker_get_delay (fc->tracker,
260 delay = GNUNET_TIME_UNIT_ZERO;
261 if (fc->num_rounds < 64)
262 delay = GNUNET_TIME_relative_max (delay,
263 GNUNET_TIME_relative_saturating_multiply
265 (1ULL << fc->num_rounds)));
267 delay = GNUNET_TIME_UNIT_FOREVER_REL;
270 /* full round transmitted wait 2x delay for ACK before going again */
272 delay = GNUNET_TIME_relative_saturating_multiply (fc->ack_delay, 2);
273 /* never use zero, need some time for ACK always */
274 delay = GNUNET_TIME_relative_max (MIN_ACK_DELAY, delay);
275 fc->wack = GNUNET_YES;
276 fc->last_round = GNUNET_TIME_absolute_get ();
277 GNUNET_STATISTICS_update (fc->stats,
278 _("# fragments wrap arounds"),
282 fc->proc_busy = GNUNET_YES;
283 fc->delay_until = GNUNET_TIME_relative_to_absolute (delay);
284 fc->num_transmissions++;
285 fc->proc (fc->proc_cls,
291 * Create a fragmentation context for the given message.
292 * Fragments the message into fragments of size @a mtu or
293 * less. Calls @a proc on each un-acknowledged fragment,
294 * using both the expected @a msg_delay between messages and
295 * acknowledgements and the given @a tracker to guide the
296 * frequency of calls to @a proc.
298 * @param stats statistics context
299 * @param mtu the maximum message size for each fragment
300 * @param tracker bandwidth tracker to use for flow control (can be NULL)
301 * @param msg_delay initial delay to insert between fragment transmissions
302 * based on previous messages
303 * @param ack_delay expected delay between fragment transmission
304 * and ACK based on previous messages
305 * @param msg the message to fragment
306 * @param proc function to call for each fragment to transmit
307 * @param proc_cls closure for @a proc
308 * @return the fragmentation context
310 struct GNUNET_FRAGMENT_Context *
311 GNUNET_FRAGMENT_context_create (struct GNUNET_STATISTICS_Handle *stats,
313 struct GNUNET_BANDWIDTH_Tracker *tracker,
314 struct GNUNET_TIME_Relative msg_delay,
315 struct GNUNET_TIME_Relative ack_delay,
316 const struct GNUNET_MessageHeader *msg,
317 GNUNET_FRAGMENT_MessageProcessor proc,
320 struct GNUNET_FRAGMENT_Context *fc;
324 GNUNET_STATISTICS_update (stats,
325 _("# messages fragmented"),
328 GNUNET_assert (mtu >= 1024 + sizeof (struct FragmentHeader));
329 size = ntohs (msg->size);
330 GNUNET_STATISTICS_update (stats,
331 _("# total size of fragmented messages"),
333 GNUNET_assert (size >= sizeof (struct GNUNET_MessageHeader));
334 fc = GNUNET_malloc (sizeof (struct GNUNET_FRAGMENT_Context) + size);
337 fc->tracker = tracker;
338 fc->ack_delay = ack_delay;
339 fc->msg_delay = msg_delay;
340 fc->msg = (const struct GNUNET_MessageHeader *) &fc[1];
342 fc->proc_cls = proc_cls;
344 GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
346 GNUNET_memcpy (&fc[1], msg, size);
348 (size + mtu - sizeof (struct FragmentHeader) - 1) / (mtu -
351 GNUNET_assert (bits <= 64);
353 fc->acks_mask = UINT64_MAX; /* set all 64 bit */
355 fc->acks_mask = (1LLU << bits) - 1; /* set lowest 'bits' bit */
356 fc->acks = fc->acks_mask;
357 fc->task = GNUNET_SCHEDULER_add_now (&transmit_next, fc);
363 * Continuation to call from the 'proc' function after the fragment
364 * has been transmitted (and hence the next fragment can now be
367 * @param fc fragmentation context
370 GNUNET_FRAGMENT_context_transmission_done (struct GNUNET_FRAGMENT_Context *fc)
372 GNUNET_assert (fc->proc_busy == GNUNET_YES);
373 fc->proc_busy = GNUNET_NO;
374 GNUNET_assert (fc->task == NULL);
376 GNUNET_SCHEDULER_add_at (fc->delay_until,
383 * Process an acknowledgement message we got from the other
384 * side (to control re-transmits).
386 * @param fc fragmentation context
387 * @param msg acknowledgement message we received
388 * @return #GNUNET_OK if this ack completes the work of the 'fc'
389 * (all fragments have been received);
390 * #GNUNET_NO if more messages are pending
391 * #GNUNET_SYSERR if this ack is not valid for this fc
394 GNUNET_FRAGMENT_process_ack (struct GNUNET_FRAGMENT_Context *fc,
395 const struct GNUNET_MessageHeader *msg)
397 const struct FragmentAcknowledgement *fa;
399 struct GNUNET_TIME_Relative ndelay;
400 unsigned int ack_cnt;
401 unsigned int snd_cnt;
404 if (sizeof (struct FragmentAcknowledgement) != ntohs (msg->size))
407 return GNUNET_SYSERR;
409 fa = (const struct FragmentAcknowledgement *) msg;
410 if (ntohl (fa->fragment_id) != fc->fragment_id)
411 return GNUNET_SYSERR; /* not our ACK */
412 abits = GNUNET_ntohll (fa->bits);
413 if ( (GNUNET_YES == fc->wack) &&
414 (0 != fc->num_transmissions) )
416 /* normal ACK, can update running average of delay... */
417 fc->wack = GNUNET_NO;
418 ndelay = GNUNET_TIME_absolute_get_duration (fc->last_round);
419 fc->ack_delay.rel_value_us =
420 (ndelay.rel_value_us / fc->num_transmissions + 3 * fc->ack_delay.rel_value_us) / 4;
421 /* calculate ratio msg sent vs. msg acked */
426 if (1 == (fc->acks_mask & (1ULL << i)))
429 if (0 == (abits & (1ULL << i)))
436 fc->msg_delay = GNUNET_TIME_relative_saturating_multiply (fc->msg_delay,
439 else if (snd_cnt > ack_cnt)
441 /* some loss, slow down proportionally */
442 fc->msg_delay.rel_value_us = ((fc->msg_delay.rel_value_us * ack_cnt) / snd_cnt);
444 else if (snd_cnt == ack_cnt)
446 fc->msg_delay.rel_value_us =
447 (ndelay.rel_value_us / fc->num_transmissions + 3 * fc->msg_delay.rel_value_us) / 5;
449 fc->num_transmissions = 0;
450 fc->msg_delay = GNUNET_TIME_relative_min (fc->msg_delay,
451 GNUNET_TIME_UNIT_SECONDS);
452 fc->ack_delay = GNUNET_TIME_relative_min (fc->ack_delay,
453 GNUNET_TIME_UNIT_SECONDS);
455 GNUNET_STATISTICS_update (fc->stats,
456 _("# fragment acknowledgements received"),
459 if (abits != (fc->acks & abits))
461 /* ID collission or message reordering, count! This should be rare! */
462 GNUNET_STATISTICS_update (fc->stats,
463 _("# bits removed from fragmentation ACKs"), 1,
466 fc->acks = abits & fc->acks_mask;
469 /* more to transmit, do so right now (if tracker permits...) */
470 if (fc->task != NULL)
472 /* schedule next transmission now, no point in waiting... */
473 GNUNET_SCHEDULER_cancel (fc->task);
474 fc->task = GNUNET_SCHEDULER_add_now (&transmit_next, fc);
478 /* only case where there is no task should be if we're waiting
479 * for the right to transmit again (proc_busy set to YES) */
480 GNUNET_assert (GNUNET_YES == fc->proc_busy);
486 GNUNET_STATISTICS_update (fc->stats,
487 _("# fragmentation transmissions completed"),
490 if (NULL != fc->task)
492 GNUNET_SCHEDULER_cancel (fc->task);
500 * Destroy the given fragmentation context (stop calling 'proc', free
503 * @param fc fragmentation context
504 * @param msg_delay where to store average delay between individual message transmissions the
505 * last message (OUT only)
506 * @param ack_delay where to store average delay between transmission and ACK for the
507 * last message, set to FOREVER if the message was not fully transmitted (OUT only)
510 GNUNET_FRAGMENT_context_destroy (struct GNUNET_FRAGMENT_Context *fc,
511 struct GNUNET_TIME_Relative *msg_delay,
512 struct GNUNET_TIME_Relative *ack_delay)
514 if (fc->task != NULL)
515 GNUNET_SCHEDULER_cancel (fc->task);
516 if (NULL != ack_delay)
517 *ack_delay = fc->ack_delay;
518 if (NULL != msg_delay)
519 *msg_delay = GNUNET_TIME_relative_saturating_multiply (fc->msg_delay,
525 /* end of fragmentation.c */