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3 (C) 2009, 2011 Christian Grothoff (and other contributing authors)
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21 * @file src/fragmentation/defragmentation.c
22 * @brief library to help defragment messages
23 * @author Christian Grothoff
26 #include "gnunet_fragmentation_lib.h"
27 #include "fragmentation.h"
30 * Timestamps for fragments.
35 * The time the fragment was received.
37 struct GNUNET_TIME_Absolute time;
40 * Number of the bit for the fragment (in [0,..,63]).
47 * Information we keep for one message that is being assembled. Note
48 * that we keep the context around even after the assembly is done to
49 * handle 'stray' messages that are received 'late'. A message
50 * context is ONLY discarded when the queue gets too big.
57 struct MessageContext *next;
62 struct MessageContext *prev;
65 * Associated defragmentation context.
67 struct GNUNET_DEFRAGMENT_Context *dc;
70 * Pointer to the assembled message, allocated at the
73 const struct GNUNET_MessageHeader *msg;
76 * Last time we received any update for this message
77 * (least-recently updated message will be discarded
78 * if we hit the queue size).
80 struct GNUNET_TIME_Absolute last_update;
83 * Task scheduled for transmitting the next ACK to the
86 GNUNET_SCHEDULER_TaskIdentifier ack_task;
89 * When did we receive which fragment? Used to calculate
90 * the time we should send the ACK.
92 struct FragTimes frag_times[64];
95 * Which fragments have we gotten yet? bits that are 1
96 * indicate missing fragments.
101 * Unique ID for this message.
103 uint32_t fragment_id;
106 * Which 'bit' did the last fragment we received correspond to?
108 unsigned int last_bit;
111 * For the current ACK round, which is the first relevant
112 * offset in 'frag_times'?
114 unsigned int frag_times_start_offset;
117 * Which offset whould we write the next frag value into
118 * in the 'frag_times' array? All smaller entries are valid.
120 unsigned int frag_times_write_offset;
123 * Total size of the message that we are assembling.
131 * Defragmentation context (one per connection).
133 struct GNUNET_DEFRAGMENT_Context
139 struct GNUNET_STATISTICS_Handle *stats;
142 * Head of list of messages we're defragmenting.
144 struct MessageContext *head;
147 * Tail of list of messages we're defragmenting.
149 struct MessageContext *tail;
152 * Closure for 'proc' and 'ackp'.
157 * Function to call with defragmented messages.
159 GNUNET_FRAGMENT_MessageProcessor proc;
162 * Function to call with acknowledgements.
164 GNUNET_DEFRAGMENT_AckProcessor ackp;
167 * Running average of the latency (delay between messages) for this
170 struct GNUNET_TIME_Relative latency;
173 * num_msgs how many fragmented messages
174 * to we defragment at most at the same time?
176 unsigned int num_msgs;
179 * Current number of messages in the 'struct MessageContext'
180 * DLL (smaller or equal to 'num_msgs').
182 unsigned int list_size;
185 * Maximum message size for each fragment.
192 * Create a defragmentation context.
194 * @param stats statistics context
195 * @param mtu the maximum message size for each fragment
196 * @param num_msgs how many fragmented messages
197 * to we defragment at most at the same time?
198 * @param cls closure for proc and ackp
199 * @param proc function to call with defragmented messages
200 * @param ackp function to call with acknowledgements (to send
201 * back to the other side)
202 * @return the defragmentation context
204 struct GNUNET_DEFRAGMENT_Context *
205 GNUNET_DEFRAGMENT_context_create (struct GNUNET_STATISTICS_Handle *stats,
207 unsigned int num_msgs,
209 GNUNET_FRAGMENT_MessageProcessor proc,
210 GNUNET_DEFRAGMENT_AckProcessor ackp)
212 struct GNUNET_DEFRAGMENT_Context *dc;
214 dc = GNUNET_malloc (sizeof (struct GNUNET_DEFRAGMENT_Context));
219 dc->num_msgs = num_msgs;
221 dc->latency = GNUNET_TIME_UNIT_SECONDS; /* start with likely overestimate */
227 * Destroy the given defragmentation context.
229 * @param dc defragmentation context
232 GNUNET_DEFRAGMENT_context_destroy (struct GNUNET_DEFRAGMENT_Context *dc)
234 struct MessageContext *mc;
236 while (NULL != (mc = dc->head))
238 GNUNET_CONTAINER_DLL_remove (dc->head,
242 if (GNUNET_SCHEDULER_NO_TASK != mc->ack_task)
244 GNUNET_SCHEDULER_cancel (mc->ack_task);
245 mc->ack_task = GNUNET_SCHEDULER_NO_TASK;
249 GNUNET_assert (0 == dc->list_size);
255 * Send acknowledgement to the other peer now.
257 * @param cls the message context
258 * @param tc the scheduler context
262 const struct GNUNET_SCHEDULER_TaskContext *tc)
264 struct MessageContext *mc = cls;
265 struct GNUNET_DEFRAGMENT_Context *dc = mc->dc;
266 struct FragmentAcknowledgement fa;
268 mc->ack_task = GNUNET_SCHEDULER_NO_TASK;
269 fa.header.size = htons (sizeof (struct FragmentAcknowledgement));
270 fa.header.type = htons (GNUNET_MESSAGE_TYPE_FRAGMENT_ACK);
271 fa.fragment_id = htonl (mc->fragment_id);
272 fa.bits = GNUNET_htonll (mc->bits);
273 GNUNET_STATISTICS_update (mc->dc->stats,
274 _("# acknowledgements sent for fragment"),
277 dc->ackp (dc->cls, mc->fragment_id, &fa.header);
282 * This function is from the GNU Scientific Library, linear/fit.c,
283 * (C) 2000 Brian Gough
286 gsl_fit_mul (const double *x, const size_t xstride,
287 const double *y, const size_t ystride,
289 double *c1, double *cov_11, double *sumsq)
291 double m_x = 0, m_y = 0, m_dx2 = 0, m_dxdy = 0;
295 for (i = 0; i < n; i++)
297 m_x += (x[i * xstride] - m_x) / (i + 1.0);
298 m_y += (y[i * ystride] - m_y) / (i + 1.0);
301 for (i = 0; i < n; i++)
303 const double dx = x[i * xstride] - m_x;
304 const double dy = y[i * ystride] - m_y;
306 m_dx2 += (dx * dx - m_dx2) / (i + 1.0);
307 m_dxdy += (dx * dy - m_dxdy) / (i + 1.0);
310 /* In terms of y = b x */
313 double s2 = 0, d2 = 0;
314 double b = (m_x * m_y + m_dxdy) / (m_x * m_x + m_dx2);
318 /* Compute chi^2 = \sum (y_i - b * x_i)^2 */
320 for (i = 0; i < n; i++)
322 const double dx = x[i * xstride] - m_x;
323 const double dy = y[i * ystride] - m_y;
324 const double d = (m_y - b * m_x) + dy - b * dx;
328 s2 = d2 / (n - 1.0); /* chisq per degree of freedom */
330 *cov_11 = s2 * 1.0 / (n * (m_x * m_x + m_dx2));
338 * Estimate the latency between messages based on the most recent
339 * message time stamps.
341 * @param mc context with time stamps
342 * @return average delay between time stamps (based on least-squares fit)
344 static struct GNUNET_TIME_Relative
345 estimate_latency (struct MessageContext *mc)
347 struct FragTimes *first;
348 size_t total = mc->frag_times_write_offset - mc->frag_times_start_offset;
355 struct GNUNET_TIME_Relative ret;
357 first = &mc->frag_times[mc->frag_times_start_offset];
358 GNUNET_assert (total > 1);
359 for (i=0;i<total;i++)
362 y[i] = (double) (first[i].time.abs_value - first[0].time.abs_value);
364 gsl_fit_mul (x, 1, y, 1, total, &c1, &cov11, &sumsq);
365 c1 += sqrt (sumsq); /* add 1 std dev */
366 ret.rel_value = (uint64_t) c1;
367 if (ret.rel_value == 0)
368 ret = GNUNET_TIME_UNIT_MILLISECONDS; /* always at least 1 */
374 * Discard the message context that was inactive for the longest time.
376 * @param dc defragmentation context
379 discard_oldest_mc (struct GNUNET_DEFRAGMENT_Context *dc)
381 struct MessageContext *old;
382 struct MessageContext *pos;
388 if ( (old == NULL) ||
389 (old->last_update.abs_value > pos->last_update.abs_value) )
393 GNUNET_assert (NULL != old);
394 GNUNET_CONTAINER_DLL_remove (dc->head,
398 if (GNUNET_SCHEDULER_NO_TASK != old->ack_task)
400 GNUNET_SCHEDULER_cancel (old->ack_task);
401 old->ack_task = GNUNET_SCHEDULER_NO_TASK;
408 * We have received a fragment. Process it.
410 * @param dc the context
411 * @param msg the message that was received
412 * @return GNUNET_OK on success, GNUNET_NO if this was a duplicate, GNUNET_SYSERR on error
415 GNUNET_DEFRAGMENT_process_fragment (struct GNUNET_DEFRAGMENT_Context *dc,
416 const struct GNUNET_MessageHeader *msg)
418 struct MessageContext *mc;
419 const struct FragmentHeader *fh;
425 struct GNUNET_TIME_Absolute now;
426 struct GNUNET_TIME_Relative delay;
432 if (ntohs(msg->size) < sizeof (struct FragmentHeader))
435 return GNUNET_SYSERR;
437 if (ntohs (msg->size) > dc->mtu)
440 return GNUNET_SYSERR;
442 fh = (const struct FragmentHeader*) msg;
443 msize = ntohs (fh->total_size);
444 if (msize < sizeof (struct GNUNET_MessageHeader))
447 return GNUNET_SYSERR;
449 fid = ntohl (fh->fragment_id);
450 foff = ntohs (fh->offset);
454 return GNUNET_SYSERR;
456 if (0 != (foff % (dc->mtu - sizeof (struct FragmentHeader))))
459 return GNUNET_SYSERR;
461 GNUNET_STATISTICS_update (dc->stats,
462 _("# fragments received"),
466 while ( (NULL != mc) &&
467 (fid != mc->fragment_id) )
469 bit = foff / (dc->mtu - sizeof (struct FragmentHeader));
470 if (bit * (dc->mtu - sizeof (struct FragmentHeader)) + ntohs (msg->size)
471 - sizeof (struct FragmentHeader) > msize)
473 /* payload extends past total message size */
475 return GNUNET_SYSERR;
477 if ( (NULL != mc) && (msize != mc->total_size) )
479 /* inconsistent message size */
481 return GNUNET_SYSERR;
483 now = GNUNET_TIME_absolute_get ();
486 mc = GNUNET_malloc (sizeof (struct MessageContext) + msize);
487 mc->msg = (const struct GNUNET_MessageHeader*) &mc[1];
489 mc->total_size = msize;
490 mc->fragment_id = fid;
491 mc->last_update = now;
492 n = (msize + dc->mtu - sizeof (struct FragmentHeader) - 1) / (dc->mtu - sizeof (struct FragmentHeader));
494 mc->bits = UINT64_MAX; /* set all 64 bit */
496 mc->bits = (1LL << n) - 1; /* set lowest 'bits' bit */
497 if (dc->list_size >= dc->num_msgs)
498 discard_oldest_mc (dc);
499 GNUNET_CONTAINER_DLL_insert (dc->head,
505 /* copy data to 'mc' */
506 if (0 != (mc->bits & (1LL << bit)))
508 mc->bits -= 1LL << bit;
509 mbuf = (char* )&mc[1];
510 memcpy (&mbuf[bit * (dc->mtu - sizeof (struct FragmentHeader))],
512 ntohs (msg->size) - sizeof (struct FragmentHeader));
513 mc->last_update = now;
514 if (bit < mc->last_bit)
515 mc->frag_times_start_offset = mc->frag_times_write_offset;
517 mc->frag_times[mc->frag_times_write_offset].time = now;
518 mc->frag_times[mc->frag_times_write_offset].bit = bit;
519 mc->frag_times_write_offset++;
520 duplicate = GNUNET_NO;
524 duplicate = GNUNET_YES;
525 GNUNET_STATISTICS_update (dc->stats,
526 _("# duplicate fragments received"),
531 /* count number of missing fragments */
534 if (0 != (mc->bits & (1LL << b))) bc++;
535 if (mc->frag_times_write_offset - mc->frag_times_start_offset > 1)
536 dc->latency = estimate_latency (mc);
537 delay = GNUNET_TIME_relative_multiply (dc->latency,
539 if ( (0 == mc->bits) || (GNUNET_YES == duplicate) ) /* message complete or duplicate, ACK now! */
540 delay = GNUNET_TIME_UNIT_ZERO;
541 if (GNUNET_SCHEDULER_NO_TASK != mc->ack_task)
542 GNUNET_SCHEDULER_cancel (mc->ack_task);
543 mc->ack_task = GNUNET_SCHEDULER_add_delayed (delay,
546 if ( (duplicate == GNUNET_NO) &&
549 GNUNET_STATISTICS_update (dc->stats,
550 _("# messages defragmented"),
553 /* message complete, notify! */
557 if (duplicate == GNUNET_YES)
562 /* end of defragmentation.c */