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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 & (1LL << 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 & (1LL << 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 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 delay = GNUNET_TIME_relative_max (delay,
262 GNUNET_TIME_relative_multiply (fc->msg_delay,
263 (1ULL << fc->num_rounds)));
266 /* full round transmitted wait 2x delay for ACK before going again */
268 delay = GNUNET_TIME_relative_multiply (fc->ack_delay, 2);
269 /* never use zero, need some time for ACK always */
270 delay = GNUNET_TIME_relative_max (MIN_ACK_DELAY, delay);
271 fc->wack = GNUNET_YES;
272 fc->last_round = GNUNET_TIME_absolute_get ();
273 GNUNET_STATISTICS_update (fc->stats,
274 _("# fragments wrap arounds"),
278 fc->proc_busy = GNUNET_YES;
279 fc->delay_until = GNUNET_TIME_relative_to_absolute (delay);
280 fc->num_transmissions++;
281 fc->proc (fc->proc_cls,
287 * Create a fragmentation context for the given message.
288 * Fragments the message into fragments of size @a mtu or
289 * less. Calls @a proc on each un-acknowledged fragment,
290 * using both the expected @a msg_delay between messages and
291 * acknowledgements and the given @a tracker to guide the
292 * frequency of calls to @a proc.
294 * @param stats statistics context
295 * @param mtu the maximum message size for each fragment
296 * @param tracker bandwidth tracker to use for flow control (can be NULL)
297 * @param msg_delay initial delay to insert between fragment transmissions
298 * based on previous messages
299 * @param ack_delay expected delay between fragment transmission
300 * and ACK based on previous messages
301 * @param msg the message to fragment
302 * @param proc function to call for each fragment to transmit
303 * @param proc_cls closure for @a proc
304 * @return the fragmentation context
306 struct GNUNET_FRAGMENT_Context *
307 GNUNET_FRAGMENT_context_create (struct GNUNET_STATISTICS_Handle *stats,
309 struct GNUNET_BANDWIDTH_Tracker *tracker,
310 struct GNUNET_TIME_Relative msg_delay,
311 struct GNUNET_TIME_Relative ack_delay,
312 const struct GNUNET_MessageHeader *msg,
313 GNUNET_FRAGMENT_MessageProcessor proc,
316 struct GNUNET_FRAGMENT_Context *fc;
320 GNUNET_STATISTICS_update (stats,
321 _("# messages fragmented"),
324 GNUNET_assert (mtu >= 1024 + sizeof (struct FragmentHeader));
325 size = ntohs (msg->size);
326 GNUNET_STATISTICS_update (stats,
327 _("# total size of fragmented messages"),
329 GNUNET_assert (size >= sizeof (struct GNUNET_MessageHeader));
330 fc = GNUNET_malloc (sizeof (struct GNUNET_FRAGMENT_Context) + size);
333 fc->tracker = tracker;
334 fc->ack_delay = ack_delay;
335 fc->msg_delay = msg_delay;
336 fc->msg = (const struct GNUNET_MessageHeader *) &fc[1];
338 fc->proc_cls = proc_cls;
340 GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
342 memcpy (&fc[1], msg, size);
344 (size + mtu - sizeof (struct FragmentHeader) - 1) / (mtu -
347 GNUNET_assert (bits <= 64);
349 fc->acks_mask = UINT64_MAX; /* set all 64 bit */
351 fc->acks_mask = (1LL << bits) - 1; /* set lowest 'bits' bit */
352 fc->acks = fc->acks_mask;
353 fc->task = GNUNET_SCHEDULER_add_now (&transmit_next, fc);
359 * Continuation to call from the 'proc' function after the fragment
360 * has been transmitted (and hence the next fragment can now be
363 * @param fc fragmentation context
366 GNUNET_FRAGMENT_context_transmission_done (struct GNUNET_FRAGMENT_Context *fc)
368 GNUNET_assert (fc->proc_busy == GNUNET_YES);
369 fc->proc_busy = GNUNET_NO;
370 GNUNET_assert (fc->task == NULL);
372 GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_absolute_get_remaining
373 (fc->delay_until), &transmit_next, fc);
378 * Process an acknowledgement message we got from the other
379 * side (to control re-transmits).
381 * @param fc fragmentation context
382 * @param msg acknowledgement message we received
383 * @return #GNUNET_OK if this ack completes the work of the 'fc'
384 * (all fragments have been received);
385 * #GNUNET_NO if more messages are pending
386 * #GNUNET_SYSERR if this ack is not valid for this fc
389 GNUNET_FRAGMENT_process_ack (struct GNUNET_FRAGMENT_Context *fc,
390 const struct GNUNET_MessageHeader *msg)
392 const struct FragmentAcknowledgement *fa;
394 struct GNUNET_TIME_Relative ndelay;
395 unsigned int ack_cnt;
396 unsigned int snd_cnt;
399 if (sizeof (struct FragmentAcknowledgement) != ntohs (msg->size))
402 return GNUNET_SYSERR;
404 fa = (const struct FragmentAcknowledgement *) msg;
405 if (ntohl (fa->fragment_id) != fc->fragment_id)
406 return GNUNET_SYSERR; /* not our ACK */
407 abits = GNUNET_ntohll (fa->bits);
408 if ( (GNUNET_YES == fc->wack) &&
409 (0 != fc->num_transmissions) )
411 /* normal ACK, can update running average of delay... */
412 fc->wack = GNUNET_NO;
413 ndelay = GNUNET_TIME_absolute_get_duration (fc->last_round);
414 fc->ack_delay.rel_value_us =
415 (ndelay.rel_value_us / fc->num_transmissions + 3 * fc->ack_delay.rel_value_us) / 4;
416 /* calculate ratio msg sent vs. msg acked */
421 if (1 == (fc->acks_mask & (1ULL << i)))
424 if (0 == (abits & (1ULL << i)))
431 fc->msg_delay = GNUNET_TIME_relative_multiply (fc->msg_delay,
434 else if (snd_cnt > ack_cnt)
436 /* some loss, slow down proportionally */
437 fc->msg_delay.rel_value_us = ((fc->msg_delay.rel_value_us * ack_cnt) / snd_cnt);
439 else if (snd_cnt == ack_cnt)
441 fc->msg_delay.rel_value_us =
442 (ndelay.rel_value_us / fc->num_transmissions + 3 * fc->msg_delay.rel_value_us) / 5;
444 fc->num_transmissions = 0;
445 fc->msg_delay = GNUNET_TIME_relative_min (fc->msg_delay,
446 GNUNET_TIME_UNIT_SECONDS);
447 fc->ack_delay = GNUNET_TIME_relative_min (fc->ack_delay,
448 GNUNET_TIME_UNIT_SECONDS);
450 GNUNET_STATISTICS_update (fc->stats,
451 _("# fragment acknowledgements received"),
454 if (abits != (fc->acks & abits))
456 /* ID collission or message reordering, count! This should be rare! */
457 GNUNET_STATISTICS_update (fc->stats,
458 _("# bits removed from fragmentation ACKs"), 1,
461 fc->acks = abits & fc->acks_mask;
464 /* more to transmit, do so right now (if tracker permits...) */
465 if (fc->task != NULL)
467 /* schedule next transmission now, no point in waiting... */
468 GNUNET_SCHEDULER_cancel (fc->task);
469 fc->task = GNUNET_SCHEDULER_add_now (&transmit_next, fc);
473 /* only case where there is no task should be if we're waiting
474 * for the right to transmit again (proc_busy set to YES) */
475 GNUNET_assert (GNUNET_YES == fc->proc_busy);
481 GNUNET_STATISTICS_update (fc->stats,
482 _("# fragmentation transmissions completed"),
485 if (NULL != fc->task)
487 GNUNET_SCHEDULER_cancel (fc->task);
495 * Destroy the given fragmentation context (stop calling 'proc', free
498 * @param fc fragmentation context
499 * @param msg_delay where to store average delay between individual message transmissions the
500 * last message (OUT only)
501 * @param ack_delay where to store average delay between transmission and ACK for the
502 * last message, set to FOREVER if the message was not fully transmitted (OUT only)
505 GNUNET_FRAGMENT_context_destroy (struct GNUNET_FRAGMENT_Context *fc,
506 struct GNUNET_TIME_Relative *msg_delay,
507 struct GNUNET_TIME_Relative *ack_delay)
509 if (fc->task != NULL)
510 GNUNET_SCHEDULER_cancel (fc->task);
511 if (NULL != ack_delay)
512 *ack_delay = fc->ack_delay;
513 if (NULL != msg_delay)
514 *msg_delay = GNUNET_TIME_relative_multiply (fc->msg_delay,
520 /* end of fragmentation.c */