X-Git-Url: http://git.meshlink.io/?a=blobdiff_plain;f=utcp.c;h=802d95a2ba87ea3de46d9235176f5273361e6ca7;hb=eb85ec4ae5f32102430e0622e3855aaba110c032;hp=7e28f9e27e3aef2a7f0937597eabbd5bd3c36f7a;hpb=b92868c9f1e00601c1cb5cccc6dc01fdb79de4ca;p=utcp

diff --git a/utcp.c b/utcp.c
index 7e28f9e..802d95a 100644
--- a/utcp.c
+++ b/utcp.c
@@ -415,13 +415,13 @@ static void update_rtt(struct utcp_connection *c, uint32_t rtt) {
 	if(!utcp->srtt) {
 		utcp->srtt = rtt;
 		utcp->rttvar = rtt / 2;
-		utcp->rto = rtt + max(2 * rtt, CLOCK_GRANULARITY);
 	} else {
 		utcp->rttvar = (utcp->rttvar * 3 + absdiff(utcp->srtt, rtt)) / 4;
 		utcp->srtt = (utcp->srtt * 7 + rtt) / 8;
-		utcp->rto = utcp->srtt + max(utcp->rttvar, CLOCK_GRANULARITY);
 	}
 
+	utcp->rto = utcp->srtt + max(4 * utcp->rttvar, CLOCK_GRANULARITY);
+
 	if(utcp->rto > MAX_RTO) {
 		utcp->rto = MAX_RTO;
 	}
@@ -1011,6 +1011,8 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 		ptr += 2;
 	}
 
+	bool has_data = len || (hdr.ctl & (SYN | FIN));
+
 	// Try to match the packet to an existing connection
 
 	struct utcp_connection *c = find_connection(utcp, hdr.dst, hdr.src);
@@ -1053,6 +1055,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 				c->flags = UTCP_TCP;
 			}
 
+synack:
 			// Return SYN+ACK, go to SYN_RECEIVED state
 			c->snd.wnd = hdr.wnd;
 			c->rcv.irs = hdr.seq;
@@ -1105,8 +1108,6 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
 	// It is for an existing connection.
 
-	uint32_t prevrcvnxt = c->rcv.nxt;
-
 	// 1. Drop invalid packets.
 
 	// 1a. Drop packets that should not happen in our current state.
@@ -1130,7 +1131,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 		break;
 	}
 
-	// 1b. Drop packets with a sequence number not in our receive window.
+	// 1b. Discard data that is not in our receive window.
 
 	if(is_reliable(c)) {
 		bool acceptable;
@@ -1282,7 +1283,6 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 	// 3. Advance snd.una
 
 	advanced = seqdiff(hdr.ack, c->snd.una);
-	prevrcvnxt = c->rcv.nxt;
 
 	if(advanced) {
 		// RTT measurement
@@ -1347,7 +1347,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 		case CLOSING:
 			if(c->snd.una == c->snd.last) {
 				gettimeofday(&c->conn_timeout, NULL);
-				c->conn_timeout.tv_sec += 60;
+				c->conn_timeout.tv_sec += utcp->timeout;
 				set_state(c, TIME_WAIT);
 			}
 
@@ -1411,6 +1411,9 @@ skip_ack:
 			break;
 
 		case SYN_RECEIVED:
+			// This is a retransmit of a SYN, send back the SYNACK.
+			goto synack;
+
 		case ESTABLISHED:
 		case FIN_WAIT_1:
 		case FIN_WAIT_2:
@@ -1506,7 +1509,7 @@ skip_ack:
 
 		case FIN_WAIT_2:
 			gettimeofday(&c->conn_timeout, NULL);
-			c->conn_timeout.tv_sec += 60;
+			c->conn_timeout.tv_sec += utcp->timeout;
 			set_state(c, TIME_WAIT);
 			break;
 
@@ -1536,13 +1539,13 @@ skip_ack:
 	}
 
 	// Now we send something back if:
-	// - we advanced rcv.nxt (ie, we got some data that needs to be ACKed)
+	// - we received data, so we have to send back an ACK
 	//   -> sendatleastone = true
 	// - or we got an ack, so we should maybe send a bit more data
 	//   -> sendatleastone = false
 
 	if(is_reliable(c) || hdr.ctl & SYN || hdr.ctl & FIN) {
-		ack(c, len || prevrcvnxt != c->rcv.nxt);
+		ack(c, has_data);
 	}
 
 	return 0;
@@ -1919,8 +1922,14 @@ void utcp_reset_timers(struct utcp *utcp) {
 			continue;
 		}
 
-		c->rtrx_timeout = now;
-		c->conn_timeout = then;
+		if(timerisset(&c->rtrx_timeout)) {
+			c->rtrx_timeout = now;
+		}
+
+		if(timerisset(&c->conn_timeout)) {
+			c->conn_timeout = then;
+		}
+
 		c->rtt_start.tv_sec = 0;
 	}
 
@@ -2071,19 +2080,24 @@ void utcp_expect_data(struct utcp_connection *c, bool expect) {
 }
 
 void utcp_offline(struct utcp *utcp, bool offline) {
+	struct timeval now;
+	gettimeofday(&now, NULL);
+
 	for(int i = 0; i < utcp->nconnections; i++) {
 		struct utcp_connection *c = utcp->connections[i];
 
-		if(!c->reapable) {
-			utcp_expect_data(c, offline);
-
-			// If we are online again, reset the retransmission timers, but keep the connection timeout as it is,
-			// to prevent peers toggling online/offline state frequently from keeping connections alive
-			// if there is no progress in sending actual data.
-			if(!offline) {
-				gettimeofday(&utcp->connections[i]->rtrx_timeout, NULL);
-				utcp->connections[i]->rtt_start.tv_sec = 0;
+		if(c->reapable) {
+			continue;
+		}
+
+		utcp_expect_data(c, offline);
+
+		if(!offline) {
+			if(timerisset(&c->rtrx_timeout)) {
+				c->rtrx_timeout = now;
 			}
+
+			utcp->connections[i]->rtt_start.tv_sec = 0;
 		}
 	}