X-Git-Url: http://git.meshlink.io/?a=blobdiff_plain;f=utcp.c;h=13f46584484bef5fd71ae74a77792671c1fb7637;hb=16ecd6d75bfabb97193581bcc8095652759cdb8e;hp=ad19982ba95afdb613eb780e6ac8d8eff6511ee3;hpb=7d8a65c11dd4b0555575ff75efab859236c4964f;p=utcp

diff --git a/utcp.c b/utcp.c
index ad19982..13f4658 100644
--- a/utcp.c
+++ b/utcp.c
@@ -49,13 +49,13 @@
 	(r)->tv_sec = (a)->tv_sec - (b)->tv_sec;\
 	(r)->tv_usec = (a)->tv_usec - (b)->tv_usec;\
 	if((r)->tv_usec < 0)\
-		(r)->tv_sec--, (r)->tv_usec += 1000000;\
+		(r)->tv_sec--, (r)->tv_usec += USEC_PER_SEC;\
 } while (0)
 #endif
 
-#ifndef max
-#define max(a, b) ((a) > (b) ? (a) : (b))
-#endif
+static inline size_t max(size_t a, size_t b) {
+	return a > b ? a : b;
+}
 
 #ifdef UTCP_DEBUG
 #include <stdarg.h>
@@ -86,11 +86,28 @@ static void print_packet(struct utcp *utcp, const char *dir, const void *pkt, si
 		debug("ACK");
 
 	if(len > sizeof hdr) {
-		debug(" data=");
-		for(int i = sizeof hdr; i < len; i++) {
-			const char *data = pkt;
-			debug("%c", data[i] >= 32 ? data[i] : '.');
+		uint32_t datalen = len - sizeof hdr;
+		uint8_t *str = malloc((datalen << 1) + 7);
+		if(!str) {
+			debug("out of memory");
+			return;
+		}
+		memcpy(str, " data=", 6);
+		uint8_t *strptr = str + 6;
+		const uint8_t *data = pkt;
+		const uint8_t *dataend = data + datalen;
+
+		while(data != dataend) {
+			*strptr = (*data >> 4) > 9? (*data >> 4) + 55 : (*data >> 4) + 48;
+			++strptr;
+			*strptr = (*data & 0xf) > 9? (*data & 0xf) + 55 : (*data & 0xf) + 48;
+			++strptr;
+			++data;
 		}
+		*strptr = 0;
+
+		debug(str);
+		free(str);
 	}
 
 	debug("\n");
@@ -156,7 +173,7 @@ static ssize_t buffer_put_at(struct buffer *buf, size_t offset, const void *data
 		} else {
 			do {
 				newsize *= 2;
-			} while(newsize < buf->used + len);
+			} while(newsize < required);
 		}
 		if(newsize > buf->maxsize)
 			newsize = buf->maxsize;
@@ -260,6 +277,7 @@ static void free_connection(struct utcp_connection *c) {
 	memmove(cp, cp + 1, (utcp->nconnections - i - 1) * sizeof *cp);
 	utcp->nconnections--;
 
+	buffer_exit(&c->rcvbuf);
 	buffer_exit(&c->sndbuf);
 	free(c);
 }
@@ -305,6 +323,7 @@ static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t s
 	}
 
 	if(!buffer_init(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
+		buffer_exit(&c->sndbuf);
 		free(c);
 		return NULL;
 	}
@@ -314,7 +333,6 @@ static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t s
 	c->src = src;
 	c->dst = dst;
 #ifdef UTCP_DEBUG
-#warning debugging
 	c->snd.iss = 0;
 #else
 	c->snd.iss = rand();
@@ -334,6 +352,46 @@ static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t s
 	return c;
 }
 
+// Update RTT variables. See RFC 6298.
+static void update_rtt(struct utcp_connection *c, uint32_t rtt) {
+	if(!rtt) {
+		debug("invalid rtt\n");
+		return;
+	}
+
+	struct utcp *utcp = c->utcp;
+
+	if(!utcp->srtt) {
+		utcp->srtt = rtt;
+		utcp->rttvar = rtt / 2;
+		utcp->rto = rtt + max(2 * rtt, CLOCK_GRANULARITY);
+	} else {
+		utcp->rttvar = (utcp->rttvar * 3 + abs(utcp->srtt - rtt)) / 4;
+		utcp->srtt = (utcp->srtt * 7 + rtt) / 8;
+		utcp->rto = utcp->srtt + max(utcp->rttvar, CLOCK_GRANULARITY);
+	}
+
+	if(utcp->rto > MAX_RTO)
+		utcp->rto = MAX_RTO;
+
+	debug("rtt %u srtt %u rttvar %u rto %u\n", rtt, utcp->srtt, utcp->rttvar, utcp->rto);
+}
+
+static void start_retransmit_timer(struct utcp_connection *c) {
+	gettimeofday(&c->rtrx_timeout, NULL);
+	c->rtrx_timeout.tv_usec += c->utcp->rto;
+	while(c->rtrx_timeout.tv_usec >= 1000000) {
+		c->rtrx_timeout.tv_usec -= 1000000;
+		c->rtrx_timeout.tv_sec++;
+	}
+	debug("timeout set to %lu.%06lu (%u)\n", c->rtrx_timeout.tv_sec, c->rtrx_timeout.tv_usec, c->utcp->rto);
+}
+
+static void stop_retransmit_timer(struct utcp_connection *c) {
+	timerclear(&c->rtrx_timeout);
+	debug("timeout cleared\n");
+}
+
 struct utcp_connection *utcp_connect(struct utcp *utcp, uint16_t dst, utcp_recv_t recv, void *priv) {
 	struct utcp_connection *c = allocate_connection(utcp, 0, dst);
 	if(!c)
@@ -421,6 +479,13 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
 			pkt->hdr.ctl |= FIN;
 		}
 
+		if(!c->rtt_start.tv_sec) {
+			// Start RTT measurement
+			gettimeofday(&c->rtt_start, NULL);
+			c->rtt_seq = pkt->hdr.seq + seglen;
+			debug("Starting RTT measurement, expecting ack %u\n", c->rtt_seq);
+		}
+
 		print_packet(c->utcp, "send", pkt, sizeof pkt->hdr + seglen);
 		c->utcp->send(c->utcp, pkt, sizeof pkt->hdr + seglen);
 	} while(left);
@@ -474,6 +539,8 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
 
 	c->snd.last += len;
 	ack(c, false);
+	if(!timerisset(&c->rtrx_timeout))
+		start_retransmit_timer(c);
 	return len;
 }
 
@@ -484,8 +551,11 @@ static void swap_ports(struct hdr *hdr) {
 }
 
 static void retransmit(struct utcp_connection *c) {
-	if(c->state == CLOSED || c->snd.nxt == c->snd.una)
+	if(c->state == CLOSED || c->snd.last == c->snd.una) {
+		debug("Retransmit() called but nothing to retransmit!\n");
+		stop_retransmit_timer(c);
 		return;
+	}
 
 	struct utcp *utcp = c->utcp;
 
@@ -500,13 +570,14 @@ static void retransmit(struct utcp_connection *c) {
 
 	pkt->hdr.src = c->src;
 	pkt->hdr.dst = c->dst;
+	pkt->hdr.wnd = c->rcv.wnd;
+	pkt->hdr.aux = 0;
 
 	switch(c->state) {
 		case SYN_SENT:
 			// Send our SYN again
 			pkt->hdr.seq = c->snd.iss;
 			pkt->hdr.ack = 0;
-			pkt->hdr.wnd = c->rcv.wnd;
 			pkt->hdr.ctl = SYN;
 			print_packet(c->utcp, "rtrx", pkt, sizeof pkt->hdr);
 			utcp->send(utcp, pkt, sizeof pkt->hdr);
@@ -552,14 +623,38 @@ static void retransmit(struct utcp_connection *c) {
 #ifdef UTCP_DEBUG
 			abort();
 #endif
-			timerclear(&c->rtrx_timeout);
-			break;
+			stop_retransmit_timer(c);
+			goto cleanup;
 	}
 
+	start_retransmit_timer(c);
+	utcp->rto *= 2;
+	if(utcp->rto > MAX_RTO)
+		utcp->rto = MAX_RTO;
+	c->rtt_start.tv_sec = 0; // invalidate RTT timer
+
+cleanup:
 	free(pkt);
 }
 
-// Update receive buffer and SACK entries after consuming data.
+/* Update receive buffer and SACK entries after consuming data.
+ *
+ * Situation:
+ *
+ * |.....0000..1111111111.....22222......3333|
+ * |---------------^
+ *
+ * 0..3 represent the SACK entries. The ^ indicates up to which point we want
+ * to remove data from the receive buffer. The idea is to substract "len"
+ * from the offset of all the SACK entries, and then remove/cut down entries
+ * that are shifted to before the start of the receive buffer.
+ *
+ * There are three cases:
+ * - the SACK entry is after ^, in that case just change the offset.
+ * - the SACK entry starts before and ends after ^, so we have to
+ *   change both its offset and size.
+ * - the SACK entry is completely before ^, in that case delete it.
+ */
 static void sack_consume(struct utcp_connection *c, size_t len) {
 	debug("sack_consume %zu\n", len);
 	if(len > c->rcvbuf.used)
@@ -572,13 +667,13 @@ static void sack_consume(struct utcp_connection *c, size_t len) {
 			c->sacks[i].offset -= len;
 			i++;
 		} else if(len < c->sacks[i].offset + c->sacks[i].len) {
-			c->sacks[i].offset = 0;
 			c->sacks[i].len -= len - c->sacks[i].offset;
+			c->sacks[i].offset = 0;
 			i++;
 		} else {
 			if(i < NSACKS - 1) {
 				memmove(&c->sacks[i], &c->sacks[i + 1], (NSACKS - 1 - i) * sizeof c->sacks[i]);
-				c->sacks[i + 1].len = 0;
+				c->sacks[NSACKS - 1].len = 0;
 			} else {
 				c->sacks[i].len = 0;
 				break;
@@ -611,6 +706,8 @@ static void handle_out_of_order(struct utcp_connection *c, uint32_t offset, cons
 					memmove(&c->sacks[i + 1], &c->sacks[i], (NSACKS - i - 1) * sizeof c->sacks[i]);
 					c->sacks[i].offset = offset;
 					c->sacks[i].len = rxd;
+				} else {
+					debug("SACK entries full, dropping packet\n");
 				}
 				break;
 			} else { // merge
@@ -760,8 +857,10 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 	// In case this is for a CLOSED connection, ignore the packet.
 	// TODO: make it so incoming packets can never match a CLOSED connection.
 
-	if(c->state == CLOSED)
+	if(c->state == CLOSED) {
+		debug("Got packet for closed connection\n");
 		return 0;
+	}
 
 	// It is for an existing connection.
 
@@ -795,18 +894,22 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
 	if(c->state == SYN_SENT)
 		acceptable = true;
-
-	// TODO: handle packets overlapping c->rcv.nxt.
-#if 1
-	// Only use this when accepting out-of-order packets.
 	else if(len == 0)
 		acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0;
-	else
+	else {
+		int32_t rcv_offset = seqdiff(hdr.seq, c->rcv.nxt);
+
+		// cut already accepted front overlapping
+		if(rcv_offset < 0) {
+			acceptable = rcv_offset + len >= 0;
+			if(acceptable) {
+				data -= rcv_offset;
+				len += rcv_offset;
+			}
+		}
+
 		acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt) + len <= c->rcvbuf.maxsize;
-#else
-	if(c->state != SYN_SENT)
-		acceptable = hdr.seq == c->rcv.nxt;
-#endif
+	}
 
 	if(!acceptable) {
 		debug("Packet not acceptable, %u <= %u + %zu < %u\n", c->rcv.nxt, hdr.seq, len, c->rcv.nxt + c->rcvbuf.maxsize);
@@ -824,10 +927,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 	// ackno should not roll back, and it should also not be bigger than what we ever could have sent
 	// (= snd.una + c->sndbuf.used).
 
-	if(hdr.ctl & ACK &&
-			((seqdiff(hdr.ack, c->snd.una + c->sndbuf.used) > 0 &&
-			  seqdiff(hdr.ack, c->snd.nxt) > 0) // TODO: simplify this if
-			 || seqdiff(hdr.ack, c->snd.una) < 0)) {
+	if(hdr.ctl & ACK && (seqdiff(hdr.ack, c->snd.last) > 0 || seqdiff(hdr.ack, c->snd.una) < 0)) {
 		debug("Packet ack seqno out of range, %u <= %u < %u\n", c->snd.una, hdr.ack, c->snd.una + c->sndbuf.used);
 		// Ignore unacceptable RST packets.
 		if(hdr.ctl & RST)
@@ -894,6 +994,20 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 	prevrcvnxt = c->rcv.nxt;
 
 	if(advanced) {
+		// RTT measurement
+		if(c->rtt_start.tv_sec) {
+			if(c->rtt_seq == hdr.ack) {
+				struct timeval now, diff;
+				gettimeofday(&now, NULL);
+				timersub(&now, &c->rtt_start, &diff);
+				update_rtt(c, diff.tv_sec * 1000000 + diff.tv_usec);
+				c->rtt_start.tv_sec = 0;
+			} else if(c->rtt_seq < hdr.ack) {
+				debug("Cancelling RTT measurement: %u < %u\n", c->rtt_seq, hdr.ack);
+				c->rtt_start.tv_sec = 0;
+			}
+		}
+
 		int32_t data_acked = advanced;
 
 		switch(c->state) {
@@ -951,6 +1065,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 				//Reset the congestion window so we wait for ACKs.
 				c->snd.nxt = c->snd.una;
 				c->snd.cwnd = utcp->mtu;
+				start_retransmit_timer(c);
 			}
 		}
 	}
@@ -959,8 +1074,10 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
 	if(advanced) {
 		timerclear(&c->conn_timeout); // It will be set anew in utcp_timeout() if c->snd.una != c->snd.nxt.
-		if(c->snd.una == c->snd.nxt)
-			timerclear(&c->rtrx_timeout);
+		if(c->snd.una == c->snd.last)
+			stop_retransmit_timer(c);
+		else
+			start_retransmit_timer(c);
 	}
 
 	// 5. Process SYN stuff
@@ -1096,8 +1213,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 	// - or we got an ack, so we should maybe send a bit more data
 	//   -> sendatleastone = false
 
-ack:
-	ack(c, prevrcvnxt != c->rcv.nxt);
+	ack(c, len || prevrcvnxt != c->rcv.nxt);
 	return 0;
 
 reset:
@@ -1174,11 +1290,13 @@ int utcp_shutdown(struct utcp_connection *c, int dir) {
 	c->snd.last++;
 
 	ack(c, false);
+	if(!timerisset(&c->rtrx_timeout))
+		start_retransmit_timer(c);
 	return 0;
 }
 
 int utcp_close(struct utcp_connection *c) {
-	if(utcp_shutdown(c, SHUT_RDWR))
+	if(utcp_shutdown(c, SHUT_RDWR) && errno != ENOTCONN)
 		return -1;
 	c->recv = NULL;
 	c->poll = NULL;
@@ -1254,6 +1372,7 @@ struct timeval utcp_timeout(struct utcp *utcp) {
 		if(!c)
 			continue;
 
+		// delete connections that have been utcp_close()d.
 		if(c->state == CLOSED) {
 			if(c->reapable) {
 				debug("Reaping %p\n", c);
@@ -1272,6 +1391,7 @@ struct timeval utcp_timeout(struct utcp *utcp) {
 		}
 
 		if(timerisset(&c->rtrx_timeout) && timercmp(&c->rtrx_timeout, &now, <)) {
+			debug("retransmit()\n");
 			retransmit(c);
 		}
 
@@ -1281,13 +1401,6 @@ struct timeval utcp_timeout(struct utcp *utcp) {
 		if(timerisset(&c->conn_timeout) && timercmp(&c->conn_timeout, &next, <))
 			next = c->conn_timeout;
 
-		if(c->snd.nxt != c->snd.una) {
-			c->rtrx_timeout = now;
-			c->rtrx_timeout.tv_sec++;
-		} else {
-			timerclear(&c->rtrx_timeout);
-		}
-
 		if(timerisset(&c->rtrx_timeout) && timercmp(&c->rtrx_timeout, &next, <))
 			next = c->rtrx_timeout;
 	}
@@ -1322,8 +1435,9 @@ struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_
 	utcp->pre_accept = pre_accept;
 	utcp->send = send;
 	utcp->priv = priv;
-	utcp->mtu = 1000;
-	utcp->timeout = 60;
+	utcp->mtu = DEFAULT_MTU;
+	utcp->timeout = DEFAULT_USER_TIMEOUT; // sec
+	utcp->rto = START_RTO; // usec
 
 	return utcp;
 }
@@ -1334,6 +1448,7 @@ void utcp_exit(struct utcp *utcp) {
 	for(int i = 0; i < utcp->nconnections; i++) {
 		if(!utcp->connections[i]->reapable)
 			debug("Warning, freeing unclosed connection %p\n", utcp->connections[i]);
+		buffer_exit(&utcp->connections[i]->rcvbuf);
 		buffer_exit(&utcp->connections[i]->sndbuf);
 		free(utcp->connections[i]);
 	}