X-Git-Url: http://git.meshlink.io/?a=blobdiff_plain;f=utcp.c;h=c21d6ab664b0146030c44d60e6feb730e924f0d8;hb=7034cc75e0324210e96b3da5ac09c979b73173b7;hp=ad19982ba95afdb613eb780e6ac8d8eff6511ee3;hpb=7d8a65c11dd4b0555575ff75efab859236c4964f;p=utcp

diff --git a/utcp.c b/utcp.c
index ad19982..c21d6ab 100644
--- a/utcp.c
+++ b/utcp.c
@@ -314,7 +314,6 @@ 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 +333,46 @@ 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 +460,13 @@ 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 +520,8 @@ 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;
 }
 
@@ -552,10 +600,17 @@ 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);
 }
 
@@ -824,10 +879,7 @@ 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 +946,20 @@ 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) {
@@ -959,8 +1025,10 @@ 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
@@ -1096,7 +1164,6 @@ 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);
 	return 0;
 
@@ -1254,6 +1321,7 @@ 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 +1340,7 @@ struct timeval utcp_timeout(struct utcp *utcp) {
 		}
 
 		if(timerisset(&c->rtrx_timeout) && timercmp(&c->rtrx_timeout, &now, <)) {
+			debug("retransmit()\n");
 			retransmit(c);
 		}
 
@@ -1281,13 +1350,6 @@ 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 +1384,9 @@ 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; // s
+	utcp->rto = START_RTO; // us
 
 	return utcp;
 }