2 This file is part of GNUnet
3 (C) 2009, 2011 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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11 WITHOUT ANY WARRANTY; without even the implied warranty of
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 delay;
58 * Next allowed transmission time.
60 struct GNUNET_TIME_Absolute delay_until;
63 * Time we transmitted the last message of the last round.
65 struct GNUNET_TIME_Absolute last_round;
68 * Message to fragment (allocated at the end of this struct).
70 const struct GNUNET_MessageHeader *msg;
73 * Function to call for transmissions.
75 GNUNET_FRAGMENT_MessageProcessor proc;
83 * Bitfield, set to 1 for each unacknowledged fragment.
88 * Bitfield with all possible bits for 'acks' (used to mask the
94 * Task performing work for the fragmenter.
96 GNUNET_SCHEDULER_TaskIdentifier task;
99 * Our fragmentation ID. (chosen at random)
101 uint32_t fragment_id;
104 * Round-robin selector for the next transmission.
106 unsigned int next_transmission;
109 * How many rounds of transmission have we completed so far?
111 unsigned int num_rounds;
114 * GNUNET_YES if we called 'proc' and are now waiting for 'GNUNET_FRAGMENT_transmission_done'
119 * GNUNET_YES if we are waiting for an ACK.
124 * Target fragment size.
132 * Transmit the next fragment to the other peer.
134 * @param cls the 'struct GNUNET_FRAGMENT_Context'
135 * @param tc scheduler context
138 transmit_next (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
140 struct GNUNET_FRAGMENT_Context *fc = cls;
143 struct FragmentHeader *fh;
144 struct GNUNET_TIME_Relative delay;
150 fc->task = GNUNET_SCHEDULER_NO_TASK;
151 GNUNET_assert (GNUNET_NO == fc->proc_busy);
153 return; /* all done */
155 /* calculate delay */
157 while (0 == (fc->acks & (1LL << fc->next_transmission)))
159 fc->next_transmission = (fc->next_transmission + 1) % 64;
160 wrap |= (fc->next_transmission == 0);
162 bit = fc->next_transmission;
163 size = ntohs (fc->msg->size);
164 if (bit == size / (fc->mtu - sizeof (struct FragmentHeader)))
166 (size % (fc->mtu - sizeof (struct FragmentHeader))) +
167 sizeof (struct FragmentHeader);
170 if (fc->tracker != NULL)
171 delay = GNUNET_BANDWIDTH_tracker_get_delay (fc->tracker, fsize);
173 delay = GNUNET_TIME_UNIT_ZERO;
174 if (delay.rel_value > 0)
176 fc->task = GNUNET_SCHEDULER_add_delayed (delay, &transmit_next, fc);
179 fc->next_transmission = (fc->next_transmission + 1) % 64;
180 wrap |= (fc->next_transmission == 0);
181 while (0 == (fc->acks & (1LL << fc->next_transmission)))
183 fc->next_transmission = (fc->next_transmission + 1) % 64;
184 wrap |= (fc->next_transmission == 0);
187 /* assemble fragmentation message */
188 mbuf = (const char *) &fc[1];
189 fh = (struct FragmentHeader *) msg;
190 fh->header.size = htons (fsize);
191 fh->header.type = htons (GNUNET_MESSAGE_TYPE_FRAGMENT);
192 fh->fragment_id = htonl (fc->fragment_id);
193 fh->total_size = fc->msg->size; /* already in big-endian */
194 fh->offset = htons ((fc->mtu - sizeof (struct FragmentHeader)) * bit);
195 memcpy (&fh[1], &mbuf[bit * (fc->mtu - sizeof (struct FragmentHeader))],
196 fsize - sizeof (struct FragmentHeader));
197 if (NULL != fc->tracker)
198 GNUNET_BANDWIDTH_tracker_consume (fc->tracker, fsize);
199 GNUNET_STATISTICS_update (fc->stats, _("# fragments transmitted"), 1,
201 if (0 != fc->last_round.abs_value)
202 GNUNET_STATISTICS_update (fc->stats, _("# fragments retransmitted"), 1,
205 /* select next message to calculate delay */
206 bit = fc->next_transmission;
207 size = ntohs (fc->msg->size);
208 if (bit == size / (fc->mtu - sizeof (struct FragmentHeader)))
209 fsize = size % (fc->mtu - sizeof (struct FragmentHeader));
212 if (NULL != fc->tracker)
213 delay = GNUNET_BANDWIDTH_tracker_get_delay (fc->tracker, fsize);
215 delay = GNUNET_TIME_UNIT_ZERO;
218 /* full round transmitted wait 2x delay for ACK before going again */
221 GNUNET_TIME_relative_max (GNUNET_TIME_relative_multiply (delay, 2),
222 GNUNET_TIME_relative_multiply (fc->delay,
224 /* never use zero, need some time for ACK always */
225 delay = GNUNET_TIME_relative_max (MIN_ACK_DELAY, delay);
226 fc->last_round = GNUNET_TIME_absolute_get ();
227 fc->wack = GNUNET_YES;
229 fc->proc_busy = GNUNET_YES;
230 fc->delay_until = GNUNET_TIME_relative_to_absolute (delay);
231 fc->proc (fc->proc_cls, &fh->header);
236 * Create a fragmentation context for the given message.
237 * Fragments the message into fragments of size "mtu" or
238 * less. Calls 'proc' on each un-acknowledged fragment,
239 * using both the expected 'delay' between messages and
240 * acknowledgements and the given 'tracker' to guide the
241 * frequency of calls to 'proc'.
243 * @param stats statistics context
244 * @param mtu the maximum message size for each fragment
245 * @param tracker bandwidth tracker to use for flow control (can be NULL)
246 * @param delay expected delay between fragment transmission
247 * and ACK based on previous messages
248 * @param msg the message to fragment
249 * @param proc function to call for each fragment to transmit
250 * @param proc_cls closure for proc
251 * @return the fragmentation context
253 struct GNUNET_FRAGMENT_Context *
254 GNUNET_FRAGMENT_context_create (struct GNUNET_STATISTICS_Handle *stats,
256 struct GNUNET_BANDWIDTH_Tracker *tracker,
257 struct GNUNET_TIME_Relative delay,
258 const struct GNUNET_MessageHeader *msg,
259 GNUNET_FRAGMENT_MessageProcessor proc,
262 struct GNUNET_FRAGMENT_Context *fc;
266 GNUNET_STATISTICS_update (stats, _("# messages fragmented"), 1, GNUNET_NO);
267 GNUNET_assert (mtu >= 1024 + sizeof (struct FragmentHeader));
268 size = ntohs (msg->size);
269 GNUNET_STATISTICS_update (stats, _("# total size of fragmented messages"),
271 GNUNET_assert (size >= sizeof (struct GNUNET_MessageHeader));
272 fc = GNUNET_malloc (sizeof (struct GNUNET_FRAGMENT_Context) + size);
275 fc->tracker = tracker;
277 fc->msg = (const struct GNUNET_MessageHeader *) &fc[1];
279 fc->proc_cls = proc_cls;
281 GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, UINT32_MAX);
282 memcpy (&fc[1], msg, size);
284 (size + mtu - sizeof (struct FragmentHeader) - 1) / (mtu -
287 GNUNET_assert (bits <= 64);
289 fc->acks_mask = UINT64_MAX; /* set all 64 bit */
291 fc->acks_mask = (1LL << bits) - 1; /* set lowest 'bits' bit */
292 fc->acks = fc->acks_mask;
293 fc->task = GNUNET_SCHEDULER_add_now (&transmit_next, fc);
299 * Continuation to call from the 'proc' function after the fragment
300 * has been transmitted (and hence the next fragment can now be
303 * @param fc fragmentation context
306 GNUNET_FRAGMENT_context_transmission_done (struct GNUNET_FRAGMENT_Context *fc)
308 GNUNET_assert (fc->proc_busy == GNUNET_YES);
309 fc->proc_busy = GNUNET_NO;
310 GNUNET_assert (fc->task == GNUNET_SCHEDULER_NO_TASK);
312 GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_absolute_get_remaining
313 (fc->delay_until), &transmit_next, fc);
318 * Process an acknowledgement message we got from the other
319 * side (to control re-transmits).
321 * @param fc fragmentation context
322 * @param msg acknowledgement message we received
323 * @return GNUNET_OK if this ack completes the work of the 'fc'
324 * (all fragments have been received);
325 * GNUNET_NO if more messages are pending
326 * GNUNET_SYSERR if this ack is not valid for this fc
329 GNUNET_FRAGMENT_process_ack (struct GNUNET_FRAGMENT_Context *fc,
330 const struct GNUNET_MessageHeader *msg)
332 const struct FragmentAcknowledgement *fa;
334 struct GNUNET_TIME_Relative ndelay;
336 if (sizeof (struct FragmentAcknowledgement) != ntohs (msg->size))
339 return GNUNET_SYSERR;
341 fa = (const struct FragmentAcknowledgement *) msg;
342 if (ntohl (fa->fragment_id) != fc->fragment_id)
343 return GNUNET_SYSERR; /* not our ACK */
344 abits = GNUNET_ntohll (fa->bits);
345 if ((GNUNET_YES == fc->wack) && (abits == (fc->acks & abits)))
347 /* normal ACK, can update running average of delay... */
348 fc->wack = GNUNET_NO;
349 ndelay = GNUNET_TIME_absolute_get_duration (fc->last_round);
350 fc->delay.rel_value =
351 (ndelay.rel_value * fc->num_rounds + 3 * fc->delay.rel_value) / 4;
353 GNUNET_STATISTICS_update (fc->stats,
354 _("# fragment acknowledgements received"), 1,
356 if (abits != (fc->acks & abits))
358 /* ID collission or message reordering, count! This should be rare! */
359 GNUNET_STATISTICS_update (fc->stats,
360 _("# bits removed from fragmentation ACKs"), 1,
363 fc->acks = abits & fc->acks_mask;
366 /* more to transmit, do so right now (if tracker permits...) */
367 if (fc->task != GNUNET_SCHEDULER_NO_TASK)
369 /* schedule next transmission now, no point in waiting... */
370 GNUNET_SCHEDULER_cancel (fc->task);
371 fc->task = GNUNET_SCHEDULER_add_now (&transmit_next, fc);
375 /* only case where there is no task should be if we're waiting
376 * for the right to transmit again (proc_busy set to YES) */
377 GNUNET_assert (GNUNET_YES == fc->proc_busy);
383 GNUNET_STATISTICS_update (fc->stats,
384 _("# fragmentation transmissions completed"), 1,
386 if (fc->task != GNUNET_SCHEDULER_NO_TASK)
388 GNUNET_SCHEDULER_cancel (fc->task);
389 fc->task = GNUNET_SCHEDULER_NO_TASK;
396 * Destroy the given fragmentation context (stop calling 'proc', free
399 * @param fc fragmentation context
400 * @return average delay between transmission and ACK for the
401 * last message, FOREVER if the message was not fully transmitted
403 struct GNUNET_TIME_Relative
404 GNUNET_FRAGMENT_context_destroy (struct GNUNET_FRAGMENT_Context *fc)
406 struct GNUNET_TIME_Relative ret;
408 if (fc->task != GNUNET_SCHEDULER_NO_TASK)
409 GNUNET_SCHEDULER_cancel (fc->task);
416 /* end of fragmentation.c */