2 utcp.c -- Userspace TCP
3 Copyright (C) 2014-2017 Guus Sliepen <guus@tinc-vpn.org>
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License along
16 with this program; if not, write to the Free Software Foundation, Inc.,
17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
32 #include "utcp_priv.h"
47 #if defined(CLOCK_MONOTONIC_RAW) && defined(__x86_64__)
48 #define UTCP_CLOCK CLOCK_MONOTONIC_RAW
50 #define UTCP_CLOCK CLOCK_MONOTONIC
54 static void timespec_sub(const struct timespec *a, const struct timespec *b, struct timespec *r) {
55 r->tv_sec = a->tv_sec - b->tv_sec;
56 r->tv_nsec = a->tv_nsec - b->tv_nsec;
59 r->tv_sec--, r->tv_nsec += NSEC_PER_SEC;
63 static int32_t timespec_diff_usec(const struct timespec *a, const struct timespec *b) {
64 return (a->tv_sec - b->tv_sec) * 1000000 + (a->tv_nsec - b->tv_nsec) / 1000;
67 static bool timespec_lt(const struct timespec *a, const struct timespec *b) {
68 if(a->tv_sec == b->tv_sec) {
69 return a->tv_nsec < b->tv_nsec;
71 return a->tv_sec < b->tv_sec;
75 static void timespec_clear(struct timespec *a) {
80 static bool timespec_isset(const struct timespec *a) {
84 static long CLOCK_GRANULARITY; // usec
86 static inline size_t min(size_t a, size_t b) {
90 static inline size_t max(size_t a, size_t b) {
97 #ifndef UTCP_DEBUG_DATALEN
98 #define UTCP_DEBUG_DATALEN 20
101 static void debug(struct utcp_connection *c, const char *format, ...) {
106 clock_gettime(CLOCK_REALTIME, &tv);
107 len = snprintf(buf, sizeof(buf), "%ld.%06lu %u:%u ", (long)tv.tv_sec, tv.tv_nsec / 1000, c ? c->src : 0, c ? c->dst : 0);
109 va_start(ap, format);
110 len += vsnprintf(buf + len, sizeof(buf) - len, format, ap);
113 if(len > 0 && (size_t)len < sizeof(buf)) {
114 fwrite(buf, len, 1, stderr);
118 static void print_packet(struct utcp_connection *c, const char *dir, const void *pkt, size_t len) {
121 if(len < sizeof(hdr)) {
122 debug(c, "%s: short packet (%lu bytes)\n", dir, (unsigned long)len);
126 memcpy(&hdr, pkt, sizeof(hdr));
130 if(len > sizeof(hdr)) {
131 datalen = min(len - sizeof(hdr), UTCP_DEBUG_DATALEN);
137 const uint8_t *data = (uint8_t *)pkt + sizeof(hdr);
138 char str[datalen * 2 + 1];
141 for(uint32_t i = 0; i < datalen; i++) {
142 *p++ = "0123456789ABCDEF"[data[i] >> 4];
143 *p++ = "0123456789ABCDEF"[data[i] & 15];
148 debug(c, "%s: len %lu src %u dst %u seq %u ack %u wnd %u aux %x ctl %s%s%s%s%s data %s\n",
149 dir, (unsigned long)len, hdr.src, hdr.dst, hdr.seq, hdr.ack, hdr.wnd, hdr.aux,
150 hdr.ctl & SYN ? "SYN" : "",
151 hdr.ctl & RST ? "RST" : "",
152 hdr.ctl & FIN ? "FIN" : "",
153 hdr.ctl & ACK ? "ACK" : "",
154 hdr.ctl & MF ? "MF" : "",
159 static void debug_cwnd(struct utcp_connection *c) {
160 debug(c, "snd.cwnd %u snd.ssthresh %u\n", c->snd.cwnd, ~c->snd.ssthresh ? c->snd.ssthresh : 0);
163 #define debug(...) do {} while(0)
164 #define print_packet(...) do {} while(0)
165 #define debug_cwnd(...) do {} while(0)
168 static void set_state(struct utcp_connection *c, enum state state) {
171 if(state == ESTABLISHED) {
172 timespec_clear(&c->conn_timeout);
175 debug(c, "state %s\n", strstate[state]);
178 static bool fin_wanted(struct utcp_connection *c, uint32_t seq) {
179 if(seq != c->snd.last) {
194 static bool is_reliable(struct utcp_connection *c) {
195 return c->flags & UTCP_RELIABLE;
198 static int32_t seqdiff(uint32_t a, uint32_t b) {
203 static bool buffer_wraps(struct buffer *buf) {
204 return buf->size - buf->offset < buf->used;
207 static bool buffer_resize(struct buffer *buf, uint32_t newsize) {
208 char *newdata = realloc(buf->data, newsize);
216 if(buffer_wraps(buf)) {
217 // Shift the right part of the buffer until it hits the end of the new buffer.
221 // [345.........|........012]
222 uint32_t tailsize = buf->size - buf->offset;
223 uint32_t newoffset = newsize - tailsize;
224 memmove(buf->data + newoffset, buf->data + buf->offset, tailsize);
225 buf->offset = newoffset;
232 // Store data into the buffer
233 static ssize_t buffer_put_at(struct buffer *buf, size_t offset, const void *data, size_t len) {
234 debug(NULL, "buffer_put_at %lu %lu %lu\n", (unsigned long)buf->used, (unsigned long)offset, (unsigned long)len);
236 // Ensure we don't store more than maxsize bytes in total
237 size_t required = offset + len;
239 if(required > buf->maxsize) {
240 if(offset >= buf->maxsize) {
244 len = buf->maxsize - offset;
245 required = buf->maxsize;
248 // Check if we need to resize the buffer
249 if(required > buf->size) {
250 size_t newsize = buf->size;
258 } while(newsize < required);
260 if(newsize > buf->maxsize) {
261 newsize = buf->maxsize;
264 if(!buffer_resize(buf, newsize)) {
269 uint32_t realoffset = buf->offset + offset;
271 if(buf->size - buf->offset <= offset) {
272 // The offset wrapped
273 realoffset -= buf->size;
276 if(buf->size - realoffset < len) {
277 // The new chunk of data must be wrapped
278 memcpy(buf->data + realoffset, data, buf->size - realoffset);
279 memcpy(buf->data, (char *)data + buf->size - realoffset, len - (buf->size - realoffset));
281 memcpy(buf->data + realoffset, data, len);
284 if(required > buf->used) {
285 buf->used = required;
291 static ssize_t buffer_put(struct buffer *buf, const void *data, size_t len) {
292 return buffer_put_at(buf, buf->used, data, len);
295 // Copy data from the buffer without removing it.
296 static ssize_t buffer_copy(struct buffer *buf, void *data, size_t offset, size_t len) {
297 // Ensure we don't copy more than is actually stored in the buffer
298 if(offset >= buf->used) {
302 if(buf->used - offset < len) {
303 len = buf->used - offset;
306 uint32_t realoffset = buf->offset + offset;
308 if(buf->size - buf->offset <= offset) {
309 // The offset wrapped
310 realoffset -= buf->size;
313 if(buf->size - realoffset < len) {
314 // The data is wrapped
315 memcpy(data, buf->data + realoffset, buf->size - realoffset);
316 memcpy((char *)data + buf->size - realoffset, buf->data, len - (buf->size - realoffset));
318 memcpy(data, buf->data + realoffset, len);
324 // Copy data from the buffer without removing it.
325 static ssize_t buffer_call(struct utcp_connection *c, struct buffer *buf, size_t offset, size_t len) {
330 // Ensure we don't copy more than is actually stored in the buffer
331 if(offset >= buf->used) {
335 if(buf->used - offset < len) {
336 len = buf->used - offset;
339 uint32_t realoffset = buf->offset + offset;
341 if(buf->size - buf->offset <= offset) {
342 // The offset wrapped
343 realoffset -= buf->size;
346 if(buf->size - realoffset < len) {
347 // The data is wrapped
348 ssize_t rx1 = c->recv(c, buf->data + realoffset, buf->size - realoffset);
350 if(rx1 < buf->size - realoffset) {
354 // The channel might have been closed by the previous callback
359 ssize_t rx2 = c->recv(c, buf->data, len - (buf->size - realoffset));
367 return c->recv(c, buf->data + realoffset, len);
371 // Discard data from the buffer.
372 static ssize_t buffer_discard(struct buffer *buf, size_t len) {
373 if(buf->used < len) {
377 if(buf->size - buf->offset <= len) {
378 buf->offset -= buf->size;
381 if(buf->used == len) {
392 static void buffer_clear(struct buffer *buf) {
397 static bool buffer_set_size(struct buffer *buf, uint32_t minsize, uint32_t maxsize) {
398 if(maxsize < minsize) {
402 buf->maxsize = maxsize;
404 return buf->size >= minsize || buffer_resize(buf, minsize);
407 static void buffer_exit(struct buffer *buf) {
409 memset(buf, 0, sizeof(*buf));
412 static uint32_t buffer_free(const struct buffer *buf) {
413 return buf->maxsize > buf->used ? buf->maxsize - buf->used : 0;
416 // Connections are stored in a sorted list.
417 // This gives O(log(N)) lookup time, O(N log(N)) insertion time and O(N) deletion time.
419 static int compare(const void *va, const void *vb) {
422 const struct utcp_connection *a = *(struct utcp_connection **)va;
423 const struct utcp_connection *b = *(struct utcp_connection **)vb;
426 assert(a->src && b->src);
428 int c = (int)a->src - (int)b->src;
434 c = (int)a->dst - (int)b->dst;
438 static struct utcp_connection *find_connection(const struct utcp *utcp, uint16_t src, uint16_t dst) {
439 if(!utcp->nconnections) {
443 struct utcp_connection key = {
447 struct utcp_connection **match = bsearch(&keyp, utcp->connections, utcp->nconnections, sizeof(*utcp->connections), compare);
448 return match ? *match : NULL;
451 static void free_connection(struct utcp_connection *c) {
452 struct utcp *utcp = c->utcp;
453 struct utcp_connection **cp = bsearch(&c, utcp->connections, utcp->nconnections, sizeof(*utcp->connections), compare);
457 int i = cp - utcp->connections;
458 memmove(cp, cp + 1, (utcp->nconnections - i - 1) * sizeof(*cp));
459 utcp->nconnections--;
461 buffer_exit(&c->rcvbuf);
462 buffer_exit(&c->sndbuf);
466 static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t src, uint16_t dst) {
467 // Check whether this combination of src and dst is free
470 if(find_connection(utcp, src, dst)) {
474 } else { // If src == 0, generate a random port number with the high bit set
475 if(utcp->nconnections >= 32767) {
480 src = rand() | 0x8000;
482 while(find_connection(utcp, src, dst)) {
487 // Allocate memory for the new connection
489 if(utcp->nconnections >= utcp->nallocated) {
490 if(!utcp->nallocated) {
491 utcp->nallocated = 4;
493 utcp->nallocated *= 2;
496 struct utcp_connection **new_array = realloc(utcp->connections, utcp->nallocated * sizeof(*utcp->connections));
502 utcp->connections = new_array;
505 struct utcp_connection *c = calloc(1, sizeof(*c));
511 if(!buffer_set_size(&c->sndbuf, DEFAULT_SNDBUFSIZE, DEFAULT_MAXSNDBUFSIZE)) {
516 if(!buffer_set_size(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
517 buffer_exit(&c->sndbuf);
522 // Fill in the details
531 c->snd.una = c->snd.iss;
532 c->snd.nxt = c->snd.iss + 1;
533 c->snd.last = c->snd.nxt;
534 c->snd.cwnd = (utcp->mss > 2190 ? 2 : utcp->mss > 1095 ? 3 : 4) * utcp->mss;
535 c->snd.ssthresh = ~0;
542 // Add it to the sorted list of connections
544 utcp->connections[utcp->nconnections++] = c;
545 qsort(utcp->connections, utcp->nconnections, sizeof(*utcp->connections), compare);
550 static inline uint32_t absdiff(uint32_t a, uint32_t b) {
558 // Update RTT variables. See RFC 6298.
559 static void update_rtt(struct utcp_connection *c, uint32_t rtt) {
561 debug(c, "invalid rtt\n");
569 c->rttvar = (c->rttvar * 3 + absdiff(c->srtt, rtt)) / 4;
570 c->srtt = (c->srtt * 7 + rtt) / 8;
573 c->rto = c->srtt + max(4 * c->rttvar, CLOCK_GRANULARITY);
575 if(c->rto > MAX_RTO) {
579 debug(c, "rtt %u srtt %u rttvar %u rto %u\n", rtt, c->srtt, c->rttvar, c->rto);
582 static void start_retransmit_timer(struct utcp_connection *c) {
583 clock_gettime(UTCP_CLOCK, &c->rtrx_timeout);
585 uint32_t rto = c->rto;
587 while(rto > USEC_PER_SEC) {
588 c->rtrx_timeout.tv_sec++;
592 c->rtrx_timeout.tv_nsec += rto * 1000;
594 if(c->rtrx_timeout.tv_nsec >= NSEC_PER_SEC) {
595 c->rtrx_timeout.tv_nsec -= NSEC_PER_SEC;
596 c->rtrx_timeout.tv_sec++;
599 debug(c, "rtrx_timeout %ld.%06lu\n", c->rtrx_timeout.tv_sec, c->rtrx_timeout.tv_nsec);
602 static void stop_retransmit_timer(struct utcp_connection *c) {
603 timespec_clear(&c->rtrx_timeout);
604 debug(c, "rtrx_timeout cleared\n");
607 struct utcp_connection *utcp_connect_ex(struct utcp *utcp, uint16_t dst, utcp_recv_t recv, void *priv, uint32_t flags) {
608 struct utcp_connection *c = allocate_connection(utcp, 0, dst);
614 assert((flags & ~0x1f) == 0);
625 pkt.hdr.src = c->src;
626 pkt.hdr.dst = c->dst;
627 pkt.hdr.seq = c->snd.iss;
629 pkt.hdr.wnd = c->rcvbuf.maxsize;
631 pkt.hdr.aux = 0x0101;
635 pkt.init[3] = flags & 0x7;
637 set_state(c, SYN_SENT);
639 print_packet(c, "send", &pkt, sizeof(pkt));
640 utcp->send(utcp, &pkt, sizeof(pkt));
642 clock_gettime(UTCP_CLOCK, &c->conn_timeout);
643 c->conn_timeout.tv_sec += utcp->timeout;
645 start_retransmit_timer(c);
650 struct utcp_connection *utcp_connect(struct utcp *utcp, uint16_t dst, utcp_recv_t recv, void *priv) {
651 return utcp_connect_ex(utcp, dst, recv, priv, UTCP_TCP);
654 void utcp_accept(struct utcp_connection *c, utcp_recv_t recv, void *priv) {
655 if(c->reapable || c->state != SYN_RECEIVED) {
656 debug(c, "accept() called on invalid connection in state %s\n", c, strstate[c->state]);
660 debug(c, "accepted %p %p\n", c, recv, priv);
663 set_state(c, ESTABLISHED);
666 static void ack(struct utcp_connection *c, bool sendatleastone) {
667 int32_t left = seqdiff(c->snd.last, c->snd.nxt);
668 int32_t cwndleft = is_reliable(c) ? min(c->snd.cwnd, c->snd.wnd) - seqdiff(c->snd.nxt, c->snd.una) : MAX_UNRELIABLE_SIZE;
674 } else if(cwndleft < left) {
677 if(!sendatleastone || cwndleft > c->utcp->mss) {
678 left -= left % c->utcp->mss;
682 debug(c, "cwndleft %d left %d\n", cwndleft, left);
684 if(!left && !sendatleastone) {
691 } *pkt = c->utcp->pkt;
693 pkt->hdr.src = c->src;
694 pkt->hdr.dst = c->dst;
695 pkt->hdr.ack = c->rcv.nxt;
696 pkt->hdr.wnd = is_reliable(c) ? c->rcvbuf.maxsize : 0;
701 uint32_t seglen = left > c->utcp->mss ? c->utcp->mss : left;
702 pkt->hdr.seq = c->snd.nxt;
704 buffer_copy(&c->sndbuf, pkt->data, seqdiff(c->snd.nxt, c->snd.una), seglen);
706 c->snd.nxt += seglen;
709 if(!is_reliable(c)) {
717 if(seglen && fin_wanted(c, c->snd.nxt)) {
722 if(!c->rtt_start.tv_sec) {
723 // Start RTT measurement
724 clock_gettime(UTCP_CLOCK, &c->rtt_start);
725 c->rtt_seq = pkt->hdr.seq + seglen;
726 debug(c, "starting RTT measurement, expecting ack %u\n", c->rtt_seq);
729 print_packet(c, "send", pkt, sizeof(pkt->hdr) + seglen);
730 c->utcp->send(c->utcp, pkt, sizeof(pkt->hdr) + seglen);
732 if(left && !is_reliable(c)) {
733 pkt->hdr.wnd += seglen;
738 ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
740 debug(c, "send() called on closed connection\n");
748 debug(c, "send() called on unconnected connection\n");
763 debug(c, "send() called on closed connection\n");
768 // Exit early if we have nothing to send.
779 // Check if we need to be able to buffer all data
781 if(c->flags & UTCP_NO_PARTIAL) {
782 if(len > buffer_free(&c->sndbuf)) {
783 if(len > c->sndbuf.maxsize) {
793 // Add data to send buffer.
796 len = buffer_put(&c->sndbuf, data, len);
797 } else if(c->state != SYN_SENT && c->state != SYN_RECEIVED) {
798 if(len > MAX_UNRELIABLE_SIZE || buffer_put(&c->sndbuf, data, len) != (ssize_t)len) {
817 // Don't send anything yet if the connection has not fully established yet
819 if(c->state == SYN_SENT || c->state == SYN_RECEIVED) {
825 if(!is_reliable(c)) {
826 c->snd.una = c->snd.nxt = c->snd.last;
827 buffer_discard(&c->sndbuf, c->sndbuf.used);
830 if(is_reliable(c) && !timespec_isset(&c->rtrx_timeout)) {
831 start_retransmit_timer(c);
834 if(is_reliable(c) && !timespec_isset(&c->conn_timeout)) {
835 clock_gettime(UTCP_CLOCK, &c->conn_timeout);
836 c->conn_timeout.tv_sec += c->utcp->timeout;
842 static void swap_ports(struct hdr *hdr) {
843 uint16_t tmp = hdr->src;
848 static void fast_retransmit(struct utcp_connection *c) {
849 if(c->state == CLOSED || c->snd.last == c->snd.una) {
850 debug(c, "fast_retransmit() called but nothing to retransmit!\n");
854 struct utcp *utcp = c->utcp;
859 } *pkt = c->utcp->pkt;
861 pkt->hdr.src = c->src;
862 pkt->hdr.dst = c->dst;
863 pkt->hdr.wnd = c->rcvbuf.maxsize;
872 // Send unacked data again.
873 pkt->hdr.seq = c->snd.una;
874 pkt->hdr.ack = c->rcv.nxt;
876 uint32_t len = min(seqdiff(c->snd.last, c->snd.una), utcp->mss);
878 if(fin_wanted(c, c->snd.una + len)) {
883 buffer_copy(&c->sndbuf, pkt->data, 0, len);
884 print_packet(c, "rtrx", pkt, sizeof(pkt->hdr) + len);
885 utcp->send(utcp, pkt, sizeof(pkt->hdr) + len);
893 static void retransmit(struct utcp_connection *c) {
894 if(c->state == CLOSED || c->snd.last == c->snd.una) {
895 debug(c, "retransmit() called but nothing to retransmit!\n");
896 stop_retransmit_timer(c);
900 struct utcp *utcp = c->utcp;
902 if(utcp->retransmit) {
909 } *pkt = c->utcp->pkt;
911 pkt->hdr.src = c->src;
912 pkt->hdr.dst = c->dst;
913 pkt->hdr.wnd = c->rcvbuf.maxsize;
918 // Send our SYN again
919 pkt->hdr.seq = c->snd.iss;
922 pkt->hdr.aux = 0x0101;
926 pkt->data[3] = c->flags & 0x7;
927 print_packet(c, "rtrx", pkt, sizeof(pkt->hdr) + 4);
928 utcp->send(utcp, pkt, sizeof(pkt->hdr) + 4);
933 pkt->hdr.seq = c->snd.nxt;
934 pkt->hdr.ack = c->rcv.nxt;
935 pkt->hdr.ctl = SYN | ACK;
936 print_packet(c, "rtrx", pkt, sizeof(pkt->hdr));
937 utcp->send(utcp, pkt, sizeof(pkt->hdr));
945 // Send unacked data again.
946 pkt->hdr.seq = c->snd.una;
947 pkt->hdr.ack = c->rcv.nxt;
949 uint32_t len = min(seqdiff(c->snd.last, c->snd.una), utcp->mss);
951 if(fin_wanted(c, c->snd.una + len)) {
956 // RFC 5681 slow start after timeout
957 uint32_t flightsize = seqdiff(c->snd.nxt, c->snd.una);
958 c->snd.ssthresh = max(flightsize / 2, utcp->mss * 2); // eq. 4
959 c->snd.cwnd = utcp->mss;
962 buffer_copy(&c->sndbuf, pkt->data, 0, len);
963 print_packet(c, "rtrx", pkt, sizeof(pkt->hdr) + len);
964 utcp->send(utcp, pkt, sizeof(pkt->hdr) + len);
966 c->snd.nxt = c->snd.una + len;
973 // We shouldn't need to retransmit anything in this state.
977 stop_retransmit_timer(c);
981 start_retransmit_timer(c);
984 if(c->rto > MAX_RTO) {
988 c->rtt_start.tv_sec = 0; // invalidate RTT timer
989 c->dupack = 0; // cancel any ongoing fast recovery
995 /* Update receive buffer and SACK entries after consuming data.
999 * |.....0000..1111111111.....22222......3333|
1002 * 0..3 represent the SACK entries. The ^ indicates up to which point we want
1003 * to remove data from the receive buffer. The idea is to substract "len"
1004 * from the offset of all the SACK entries, and then remove/cut down entries
1005 * that are shifted to before the start of the receive buffer.
1007 * There are three cases:
1008 * - the SACK entry is after ^, in that case just change the offset.
1009 * - the SACK entry starts before and ends after ^, so we have to
1010 * change both its offset and size.
1011 * - the SACK entry is completely before ^, in that case delete it.
1013 static void sack_consume(struct utcp_connection *c, size_t len) {
1014 debug(c, "sack_consume %lu\n", (unsigned long)len);
1016 if(len > c->rcvbuf.used) {
1017 debug(c, "all SACK entries consumed\n");
1018 c->sacks[0].len = 0;
1022 buffer_discard(&c->rcvbuf, len);
1024 for(int i = 0; i < NSACKS && c->sacks[i].len;) {
1025 if(len < c->sacks[i].offset) {
1026 c->sacks[i].offset -= len;
1028 } else if(len < c->sacks[i].offset + c->sacks[i].len) {
1029 c->sacks[i].len -= len - c->sacks[i].offset;
1030 c->sacks[i].offset = 0;
1033 if(i < NSACKS - 1) {
1034 memmove(&c->sacks[i], &c->sacks[i + 1], (NSACKS - 1 - i) * sizeof(c->sacks)[i]);
1035 c->sacks[NSACKS - 1].len = 0;
1037 c->sacks[i].len = 0;
1043 for(int i = 0; i < NSACKS && c->sacks[i].len; i++) {
1044 debug(c, "SACK[%d] offset %u len %u\n", i, c->sacks[i].offset, c->sacks[i].len);
1048 static void handle_out_of_order(struct utcp_connection *c, uint32_t offset, const void *data, size_t len) {
1049 debug(c, "out of order packet, offset %u\n", offset);
1050 // Packet loss or reordering occured. Store the data in the buffer.
1051 ssize_t rxd = buffer_put_at(&c->rcvbuf, offset, data, len);
1054 debug(c, "packet outside receive buffer, dropping\n");
1058 if((size_t)rxd < len) {
1059 debug(c, "packet partially outside receive buffer\n");
1063 // Make note of where we put it.
1064 for(int i = 0; i < NSACKS; i++) {
1065 if(!c->sacks[i].len) { // nothing to merge, add new entry
1066 debug(c, "new SACK entry %d\n", i);
1067 c->sacks[i].offset = offset;
1068 c->sacks[i].len = rxd;
1070 } else if(offset < c->sacks[i].offset) {
1071 if(offset + rxd < c->sacks[i].offset) { // insert before
1072 if(!c->sacks[NSACKS - 1].len) { // only if room left
1073 debug(c, "insert SACK entry at %d\n", i);
1074 memmove(&c->sacks[i + 1], &c->sacks[i], (NSACKS - i - 1) * sizeof(c->sacks)[i]);
1075 c->sacks[i].offset = offset;
1076 c->sacks[i].len = rxd;
1078 debug(c, "SACK entries full, dropping packet\n");
1083 debug(c, "merge with start of SACK entry at %d\n", i);
1084 c->sacks[i].offset = offset;
1087 } else if(offset <= c->sacks[i].offset + c->sacks[i].len) {
1088 if(offset + rxd > c->sacks[i].offset + c->sacks[i].len) { // merge
1089 debug(c, "merge with end of SACK entry at %d\n", i);
1090 c->sacks[i].len = offset + rxd - c->sacks[i].offset;
1091 // TODO: handle potential merge with next entry
1098 for(int i = 0; i < NSACKS && c->sacks[i].len; i++) {
1099 debug(c, "SACK[%d] offset %u len %u\n", i, c->sacks[i].offset, c->sacks[i].len);
1103 static void handle_in_order(struct utcp_connection *c, const void *data, size_t len) {
1105 ssize_t rxd = c->recv(c, data, len);
1107 if(rxd != (ssize_t)len) {
1108 // TODO: handle the application not accepting all data.
1113 // Check if we can process out-of-order data now.
1114 if(c->sacks[0].len && len >= c->sacks[0].offset) {
1115 debug(c, "incoming packet len %lu connected with SACK at %u\n", (unsigned long)len, c->sacks[0].offset);
1117 if(len < c->sacks[0].offset + c->sacks[0].len) {
1118 size_t offset = len;
1119 len = c->sacks[0].offset + c->sacks[0].len;
1120 size_t remainder = len - offset;
1122 ssize_t rxd = buffer_call(c, &c->rcvbuf, offset, remainder);
1124 if(rxd != (ssize_t)remainder) {
1125 // TODO: handle the application not accepting all data.
1131 if(c->rcvbuf.used) {
1132 sack_consume(c, len);
1138 static void handle_unreliable(struct utcp_connection *c, const struct hdr *hdr, const void *data, size_t len) {
1139 // Fast path for unfragmented packets
1140 if(!hdr->wnd && !(hdr->ctl & MF)) {
1142 c->recv(c, data, len);
1145 c->rcv.nxt = hdr->seq + len;
1149 // Ensure reassembled packet are not larger than 64 kiB
1150 if(hdr->wnd >= MAX_UNRELIABLE_SIZE || hdr->wnd + len > MAX_UNRELIABLE_SIZE) {
1154 // Don't accept out of order fragments
1155 if(hdr->wnd && hdr->seq != c->rcv.nxt) {
1159 // Reset the receive buffer for the first fragment
1161 buffer_clear(&c->rcvbuf);
1164 ssize_t rxd = buffer_put_at(&c->rcvbuf, hdr->wnd, data, len);
1166 if(rxd != (ssize_t)len) {
1170 // Send the packet if it's the final fragment
1171 if(!(hdr->ctl & MF)) {
1172 buffer_call(c, &c->rcvbuf, 0, hdr->wnd + len);
1175 c->rcv.nxt = hdr->seq + len;
1178 static void handle_incoming_data(struct utcp_connection *c, const struct hdr *hdr, const void *data, size_t len) {
1179 if(!is_reliable(c)) {
1180 handle_unreliable(c, hdr, data, len);
1184 uint32_t offset = seqdiff(hdr->seq, c->rcv.nxt);
1187 handle_out_of_order(c, offset, data, len);
1189 handle_in_order(c, data, len);
1194 ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
1195 const uint8_t *ptr = data;
1211 // Drop packets smaller than the header
1215 if(len < sizeof(hdr)) {
1216 print_packet(NULL, "recv", data, len);
1221 // Make a copy from the potentially unaligned data to a struct hdr
1223 memcpy(&hdr, ptr, sizeof(hdr));
1225 // Try to match the packet to an existing connection
1227 struct utcp_connection *c = find_connection(utcp, hdr.dst, hdr.src);
1228 print_packet(c, "recv", data, len);
1230 // Process the header
1235 // Drop packets with an unknown CTL flag
1237 if(hdr.ctl & ~(SYN | ACK | RST | FIN | MF)) {
1238 print_packet(NULL, "recv", data, len);
1243 // Check for auxiliary headers
1245 const uint8_t *init = NULL;
1247 uint16_t aux = hdr.aux;
1250 size_t auxlen = 4 * (aux >> 8) & 0xf;
1251 uint8_t auxtype = aux & 0xff;
1260 if(!(hdr.ctl & SYN) || auxlen != 4) {
1276 if(!(aux & 0x800)) {
1285 memcpy(&aux, ptr, 2);
1290 bool has_data = len || (hdr.ctl & (SYN | FIN));
1292 // Is it for a new connection?
1295 // Ignore RST packets
1301 // Is it a SYN packet and are we LISTENing?
1303 if(hdr.ctl & SYN && !(hdr.ctl & ACK) && utcp->accept) {
1304 // If we don't want to accept it, send a RST back
1305 if((utcp->pre_accept && !utcp->pre_accept(utcp, hdr.dst))) {
1310 // Try to allocate memory, otherwise send a RST back
1311 c = allocate_connection(utcp, hdr.dst, hdr.src);
1318 // Parse auxilliary information
1325 c->flags = init[3] & 0x7;
1327 c->flags = UTCP_TCP;
1331 // Return SYN+ACK, go to SYN_RECEIVED state
1332 c->snd.wnd = hdr.wnd;
1333 c->rcv.irs = hdr.seq;
1334 c->rcv.nxt = c->rcv.irs + 1;
1335 set_state(c, SYN_RECEIVED);
1342 pkt.hdr.src = c->src;
1343 pkt.hdr.dst = c->dst;
1344 pkt.hdr.ack = c->rcv.irs + 1;
1345 pkt.hdr.seq = c->snd.iss;
1346 pkt.hdr.wnd = c->rcvbuf.maxsize;
1347 pkt.hdr.ctl = SYN | ACK;
1350 pkt.hdr.aux = 0x0101;
1354 pkt.data[3] = c->flags & 0x7;
1355 print_packet(c, "send", &pkt, sizeof(hdr) + 4);
1356 utcp->send(utcp, &pkt, sizeof(hdr) + 4);
1359 print_packet(c, "send", &pkt, sizeof(hdr));
1360 utcp->send(utcp, &pkt, sizeof(hdr));
1363 start_retransmit_timer(c);
1365 // No, we don't want your packets, send a RST back
1373 debug(c, "state %s\n", strstate[c->state]);
1375 // In case this is for a CLOSED connection, ignore the packet.
1376 // TODO: make it so incoming packets can never match a CLOSED connection.
1378 if(c->state == CLOSED) {
1379 debug(c, "got packet for closed connection\n");
1383 // It is for an existing connection.
1385 // 1. Drop invalid packets.
1387 // 1a. Drop packets that should not happen in our current state.
1408 // 1b. Discard data that is not in our receive window.
1410 if(is_reliable(c)) {
1413 if(c->state == SYN_SENT) {
1415 } else if(len == 0) {
1416 acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0;
1418 int32_t rcv_offset = seqdiff(hdr.seq, c->rcv.nxt);
1420 // cut already accepted front overlapping
1421 if(rcv_offset < 0) {
1422 acceptable = len > (size_t) - rcv_offset;
1427 hdr.seq -= rcv_offset;
1430 acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt) + len <= c->rcvbuf.maxsize;
1435 debug(c, "packet not acceptable, %u <= %u + %lu < %u\n", c->rcv.nxt, hdr.seq, (unsigned long)len, c->rcv.nxt + c->rcvbuf.maxsize);
1437 // Ignore unacceptable RST packets.
1442 // Otherwise, continue processing.
1447 int32_t rcv_offset = seqdiff(hdr.seq, c->rcv.nxt);
1450 debug(c, "packet out of order, offset %u bytes", rcv_offset);
1456 c->snd.wnd = hdr.wnd; // TODO: move below
1458 // 1c. Drop packets with an invalid ACK.
1459 // ackno should not roll back, and it should also not be bigger than what we ever could have sent
1460 // (= snd.una + c->sndbuf.used).
1462 if(!is_reliable(c)) {
1463 if(hdr.ack != c->snd.last && c->state >= ESTABLISHED) {
1464 hdr.ack = c->snd.una;
1468 if(hdr.ctl & ACK && (seqdiff(hdr.ack, c->snd.last) > 0 || seqdiff(hdr.ack, c->snd.una) < 0)) {
1469 debug(c, "packet ack seqno out of range, %u <= %u < %u\n", c->snd.una, hdr.ack, c->snd.una + c->sndbuf.used);
1471 // Ignore unacceptable RST packets.
1479 // 2. Handle RST packets
1484 if(!(hdr.ctl & ACK)) {
1488 // The peer has refused our connection.
1489 set_state(c, CLOSED);
1490 errno = ECONNREFUSED;
1493 c->recv(c, NULL, 0);
1496 if(c->poll && !c->reapable) {
1507 // We haven't told the application about this connection yet. Silently delete.
1519 // The peer has aborted our connection.
1520 set_state(c, CLOSED);
1524 c->recv(c, NULL, 0);
1527 if(c->poll && !c->reapable) {
1540 // As far as the application is concerned, the connection has already been closed.
1541 // If it has called utcp_close() already, we can immediately free this connection.
1547 // Otherwise, immediately move to the CLOSED state.
1548 set_state(c, CLOSED);
1561 if(!(hdr.ctl & ACK)) {
1566 // 3. Advance snd.una
1568 advanced = seqdiff(hdr.ack, c->snd.una);
1572 if(c->rtt_start.tv_sec) {
1573 if(c->rtt_seq == hdr.ack) {
1574 struct timespec now;
1575 clock_gettime(UTCP_CLOCK, &now);
1576 int32_t diff = timespec_diff_usec(&now, &c->rtt_start);
1577 update_rtt(c, diff);
1578 c->rtt_start.tv_sec = 0;
1579 } else if(c->rtt_seq < hdr.ack) {
1580 debug(c, "cancelling RTT measurement: %u < %u\n", c->rtt_seq, hdr.ack);
1581 c->rtt_start.tv_sec = 0;
1585 int32_t data_acked = advanced;
1593 // TODO: handle FIN as well.
1598 assert(data_acked >= 0);
1601 int32_t bufused = seqdiff(c->snd.last, c->snd.una);
1602 assert(data_acked <= bufused);
1606 buffer_discard(&c->sndbuf, data_acked);
1608 if(is_reliable(c)) {
1613 // Also advance snd.nxt if possible
1614 if(seqdiff(c->snd.nxt, hdr.ack) < 0) {
1615 c->snd.nxt = hdr.ack;
1618 c->snd.una = hdr.ack;
1621 if(c->dupack >= 3) {
1622 debug(c, "fast recovery ended\n");
1623 c->snd.cwnd = c->snd.ssthresh;
1629 // Increase the congestion window according to RFC 5681
1630 if(c->snd.cwnd < c->snd.ssthresh) {
1631 c->snd.cwnd += min(advanced, utcp->mss); // eq. 2
1633 c->snd.cwnd += max(1, (utcp->mss * utcp->mss) / c->snd.cwnd); // eq. 3
1636 if(c->snd.cwnd > c->sndbuf.maxsize) {
1637 c->snd.cwnd = c->sndbuf.maxsize;
1642 // Check if we have sent a FIN that is now ACKed.
1645 if(c->snd.una == c->snd.last) {
1646 set_state(c, FIN_WAIT_2);
1652 if(c->snd.una == c->snd.last) {
1653 clock_gettime(UTCP_CLOCK, &c->conn_timeout);
1654 c->conn_timeout.tv_sec += utcp->timeout;
1655 set_state(c, TIME_WAIT);
1664 if(!len && is_reliable(c) && c->snd.una != c->snd.last) {
1666 debug(c, "duplicate ACK %d\n", c->dupack);
1668 if(c->dupack == 3) {
1669 // RFC 5681 fast recovery
1670 debug(c, "fast recovery started\n", c->dupack);
1671 uint32_t flightsize = seqdiff(c->snd.nxt, c->snd.una);
1672 c->snd.ssthresh = max(flightsize / 2, utcp->mss * 2); // eq. 4
1673 c->snd.cwnd = min(c->snd.ssthresh + 3 * utcp->mss, c->sndbuf.maxsize);
1675 if(c->snd.cwnd > c->sndbuf.maxsize) {
1676 c->snd.cwnd = c->sndbuf.maxsize;
1682 } else if(c->dupack > 3) {
1683 c->snd.cwnd += utcp->mss;
1685 if(c->snd.cwnd > c->sndbuf.maxsize) {
1686 c->snd.cwnd = c->sndbuf.maxsize;
1692 // We got an ACK which indicates the other side did get one of our packets.
1693 // Reset the retransmission timer to avoid going to slow start,
1694 // but don't touch the connection timeout.
1695 start_retransmit_timer(c);
1702 if(c->snd.una == c->snd.last) {
1703 stop_retransmit_timer(c);
1704 timespec_clear(&c->conn_timeout);
1705 } else if(is_reliable(c)) {
1706 start_retransmit_timer(c);
1707 clock_gettime(UTCP_CLOCK, &c->conn_timeout);
1708 c->conn_timeout.tv_sec += utcp->timeout;
1713 // 5. Process SYN stuff
1719 // This is a SYNACK. It should always have ACKed the SYN.
1724 c->rcv.irs = hdr.seq;
1725 c->rcv.nxt = hdr.seq + 1;
1729 set_state(c, FIN_WAIT_1);
1731 set_state(c, ESTABLISHED);
1737 // This is a retransmit of a SYN, send back the SYNACK.
1747 // This could be a retransmission. Ignore the SYN flag, but send an ACK back.
1758 // 6. Process new data
1760 if(c->state == SYN_RECEIVED) {
1761 // This is the ACK after the SYNACK. It should always have ACKed the SYNACK.
1766 // Are we still LISTENing?
1768 utcp->accept(c, c->src);
1771 if(c->state != ESTABLISHED) {
1772 set_state(c, CLOSED);
1782 // This should never happen.
1797 // Ehm no, We should never receive more data after a FIN.
1807 handle_incoming_data(c, &hdr, ptr, len);
1810 // 7. Process FIN stuff
1812 if((hdr.ctl & FIN) && (!is_reliable(c) || hdr.seq + len == c->rcv.nxt)) {
1816 // This should never happen.
1823 set_state(c, CLOSE_WAIT);
1827 set_state(c, CLOSING);
1831 clock_gettime(UTCP_CLOCK, &c->conn_timeout);
1832 c->conn_timeout.tv_sec += utcp->timeout;
1833 set_state(c, TIME_WAIT);
1840 // Ehm, no. We should never receive a second FIN.
1850 // FIN counts as one sequence number
1854 // Inform the application that the peer closed its end of the connection.
1857 c->recv(c, NULL, 0);
1861 // Now we send something back if:
1862 // - we received data, so we have to send back an ACK
1863 // -> sendatleastone = true
1864 // - or we got an ack, so we should maybe send a bit more data
1865 // -> sendatleastone = false
1867 if(is_reliable(c) || hdr.ctl & SYN || hdr.ctl & FIN) {
1882 hdr.ack = hdr.seq + len;
1884 hdr.ctl = RST | ACK;
1887 print_packet(c, "send", &hdr, sizeof(hdr));
1888 utcp->send(utcp, &hdr, sizeof(hdr));
1893 int utcp_shutdown(struct utcp_connection *c, int dir) {
1894 debug(c, "shutdown %d at %u\n", dir, c ? c->snd.last : 0);
1902 debug(c, "shutdown() called on closed connection\n");
1907 if(!(dir == UTCP_SHUT_RD || dir == UTCP_SHUT_WR || dir == UTCP_SHUT_RDWR)) {
1912 // TCP does not have a provision for stopping incoming packets.
1913 // The best we can do is to just ignore them.
1914 if(dir == UTCP_SHUT_RD || dir == UTCP_SHUT_RDWR) {
1918 // The rest of the code deals with shutting down writes.
1919 if(dir == UTCP_SHUT_RD) {
1923 // Only process shutting down writes once.
1941 set_state(c, FIN_WAIT_1);
1949 set_state(c, CLOSING);
1962 if(!timespec_isset(&c->rtrx_timeout)) {
1963 start_retransmit_timer(c);
1969 static bool reset_connection(struct utcp_connection *c) {
1976 debug(c, "abort() called on closed connection\n");
1993 set_state(c, CLOSED);
2001 set_state(c, CLOSED);
2011 hdr.seq = c->snd.nxt;
2016 print_packet(c, "send", &hdr, sizeof(hdr));
2017 c->utcp->send(c->utcp, &hdr, sizeof(hdr));
2021 // Closes all the opened connections
2022 void utcp_abort_all_connections(struct utcp *utcp) {
2028 for(int i = 0; i < utcp->nconnections; i++) {
2029 struct utcp_connection *c = utcp->connections[i];
2031 if(c->reapable || c->state == CLOSED) {
2035 utcp_recv_t old_recv = c->recv;
2036 utcp_poll_t old_poll = c->poll;
2038 reset_connection(c);
2042 old_recv(c, NULL, 0);
2045 if(old_poll && !c->reapable) {
2054 int utcp_close(struct utcp_connection *c) {
2055 if(utcp_shutdown(c, SHUT_RDWR) && errno != ENOTCONN) {
2065 int utcp_abort(struct utcp_connection *c) {
2066 if(!reset_connection(c)) {
2075 * One call to this function will loop through all connections,
2076 * checking if something needs to be resent or not.
2077 * The return value is the time to the next timeout in milliseconds,
2078 * or maybe a negative value if the timeout is infinite.
2080 struct timespec utcp_timeout(struct utcp *utcp) {
2081 struct timespec now;
2082 clock_gettime(UTCP_CLOCK, &now);
2083 struct timespec next = {now.tv_sec + 3600, now.tv_nsec};
2085 for(int i = 0; i < utcp->nconnections; i++) {
2086 struct utcp_connection *c = utcp->connections[i];
2092 // delete connections that have been utcp_close()d.
2093 if(c->state == CLOSED) {
2095 debug(c, "reaping\n");
2103 if(timespec_isset(&c->conn_timeout) && timespec_lt(&c->conn_timeout, &now)) {
2108 c->recv(c, NULL, 0);
2111 if(c->poll && !c->reapable) {
2118 if(timespec_isset(&c->rtrx_timeout) && timespec_lt(&c->rtrx_timeout, &now)) {
2119 debug(c, "retransmitting after timeout\n");
2124 if((c->state == ESTABLISHED || c->state == CLOSE_WAIT) && c->do_poll) {
2126 uint32_t len = buffer_free(&c->sndbuf);
2131 } else if(c->state == CLOSED) {
2136 if(timespec_isset(&c->conn_timeout) && timespec_lt(&c->conn_timeout, &next)) {
2137 next = c->conn_timeout;
2140 if(timespec_isset(&c->rtrx_timeout) && timespec_lt(&c->rtrx_timeout, &next)) {
2141 next = c->rtrx_timeout;
2145 struct timespec diff;
2147 timespec_sub(&next, &now, &diff);
2152 bool utcp_is_active(struct utcp *utcp) {
2157 for(int i = 0; i < utcp->nconnections; i++)
2158 if(utcp->connections[i]->state != CLOSED && utcp->connections[i]->state != TIME_WAIT) {
2165 struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_send_t send, void *priv) {
2171 struct utcp *utcp = calloc(1, sizeof(*utcp));
2177 utcp_set_mtu(utcp, DEFAULT_MTU);
2184 if(!CLOCK_GRANULARITY) {
2185 struct timespec res;
2186 clock_getres(UTCP_CLOCK, &res);
2187 CLOCK_GRANULARITY = res.tv_sec * USEC_PER_SEC + res.tv_nsec / 1000;
2190 utcp->accept = accept;
2191 utcp->pre_accept = pre_accept;
2194 utcp->timeout = DEFAULT_USER_TIMEOUT; // sec
2199 void utcp_exit(struct utcp *utcp) {
2204 for(int i = 0; i < utcp->nconnections; i++) {
2205 struct utcp_connection *c = utcp->connections[i];
2209 c->recv(c, NULL, 0);
2212 if(c->poll && !c->reapable) {
2217 buffer_exit(&c->rcvbuf);
2218 buffer_exit(&c->sndbuf);
2222 free(utcp->connections);
2227 uint16_t utcp_get_mtu(struct utcp *utcp) {
2228 return utcp ? utcp->mtu : 0;
2231 uint16_t utcp_get_mss(struct utcp *utcp) {
2232 return utcp ? utcp->mss : 0;
2235 void utcp_set_mtu(struct utcp *utcp, uint16_t mtu) {
2240 if(mtu <= sizeof(struct hdr)) {
2244 if(mtu > utcp->mtu) {
2245 char *new = realloc(utcp->pkt, mtu + sizeof(struct hdr));
2255 utcp->mss = mtu - sizeof(struct hdr);
2258 void utcp_reset_timers(struct utcp *utcp) {
2263 struct timespec now, then;
2265 clock_gettime(UTCP_CLOCK, &now);
2269 then.tv_sec += utcp->timeout;
2271 for(int i = 0; i < utcp->nconnections; i++) {
2272 struct utcp_connection *c = utcp->connections[i];
2278 if(timespec_isset(&c->rtrx_timeout)) {
2279 c->rtrx_timeout = now;
2282 if(timespec_isset(&c->conn_timeout)) {
2283 c->conn_timeout = then;
2286 c->rtt_start.tv_sec = 0;
2288 if(c->rto > START_RTO) {
2294 int utcp_get_user_timeout(struct utcp *u) {
2295 return u ? u->timeout : 0;
2298 void utcp_set_user_timeout(struct utcp *u, int timeout) {
2300 u->timeout = timeout;
2304 size_t utcp_get_sndbuf(struct utcp_connection *c) {
2305 return c ? c->sndbuf.maxsize : 0;
2308 size_t utcp_get_sndbuf_free(struct utcp_connection *c) {
2318 return buffer_free(&c->sndbuf);
2325 void utcp_set_sndbuf(struct utcp_connection *c, size_t size) {
2330 c->sndbuf.maxsize = size;
2332 if(c->sndbuf.maxsize != size) {
2333 c->sndbuf.maxsize = -1;
2336 c->do_poll = is_reliable(c) && buffer_free(&c->sndbuf);
2339 size_t utcp_get_rcvbuf(struct utcp_connection *c) {
2340 return c ? c->rcvbuf.maxsize : 0;
2343 size_t utcp_get_rcvbuf_free(struct utcp_connection *c) {
2344 if(c && (c->state == ESTABLISHED || c->state == CLOSE_WAIT)) {
2345 return buffer_free(&c->rcvbuf);
2351 void utcp_set_rcvbuf(struct utcp_connection *c, size_t size) {
2356 c->rcvbuf.maxsize = size;
2358 if(c->rcvbuf.maxsize != size) {
2359 c->rcvbuf.maxsize = -1;
2363 size_t utcp_get_sendq(struct utcp_connection *c) {
2364 return c->sndbuf.used;
2367 size_t utcp_get_recvq(struct utcp_connection *c) {
2368 return c->rcvbuf.used;
2371 bool utcp_get_nodelay(struct utcp_connection *c) {
2372 return c ? c->nodelay : false;
2375 void utcp_set_nodelay(struct utcp_connection *c, bool nodelay) {
2377 c->nodelay = nodelay;
2381 bool utcp_get_keepalive(struct utcp_connection *c) {
2382 return c ? c->keepalive : false;
2385 void utcp_set_keepalive(struct utcp_connection *c, bool keepalive) {
2387 c->keepalive = keepalive;
2391 size_t utcp_get_outq(struct utcp_connection *c) {
2392 return c ? seqdiff(c->snd.nxt, c->snd.una) : 0;
2395 void utcp_set_recv_cb(struct utcp_connection *c, utcp_recv_t recv) {
2401 void utcp_set_poll_cb(struct utcp_connection *c, utcp_poll_t poll) {
2404 c->do_poll = is_reliable(c) && buffer_free(&c->sndbuf);
2408 void utcp_set_accept_cb(struct utcp *utcp, utcp_accept_t accept, utcp_pre_accept_t pre_accept) {
2410 utcp->accept = accept;
2411 utcp->pre_accept = pre_accept;
2415 void utcp_expect_data(struct utcp_connection *c, bool expect) {
2416 if(!c || c->reapable) {
2420 if(!(c->state == ESTABLISHED || c->state == FIN_WAIT_1 || c->state == FIN_WAIT_2)) {
2425 // If we expect data, start the connection timer.
2426 if(!timespec_isset(&c->conn_timeout)) {
2427 clock_gettime(UTCP_CLOCK, &c->conn_timeout);
2428 c->conn_timeout.tv_sec += c->utcp->timeout;
2431 // If we want to cancel expecting data, only clear the timer when there is no unACKed data.
2432 if(c->snd.una == c->snd.last) {
2433 timespec_clear(&c->conn_timeout);
2438 void utcp_offline(struct utcp *utcp, bool offline) {
2439 struct timespec now;
2440 clock_gettime(UTCP_CLOCK, &now);
2442 for(int i = 0; i < utcp->nconnections; i++) {
2443 struct utcp_connection *c = utcp->connections[i];
2449 utcp_expect_data(c, offline);
2452 if(timespec_isset(&c->rtrx_timeout)) {
2453 c->rtrx_timeout = now;
2456 utcp->connections[i]->rtt_start.tv_sec = 0;
2458 if(c->rto > START_RTO) {
2465 void utcp_set_retransmit_cb(struct utcp *utcp, utcp_retransmit_t retransmit) {
2466 utcp->retransmit = retransmit;
2469 void utcp_set_clock_granularity(long granularity) {
2470 CLOCK_GRANULARITY = granularity;