X-Git-Url: http://git.meshlink.io/?a=blobdiff_plain;f=utcp.c;h=ac598ddae28667fd9a40c28ace29255b7dd22f66;hb=83f65f2eee2d5c7d58b27021770926d53f0f193e;hp=b53541d5e3e6bab3400daf70ed8141e9b018b01c;hpb=488a66580c31a873b93ed541505e1525607bbed8;p=utcp

diff --git a/utcp.c b/utcp.c
index b53541d..ac598dd 100644
--- a/utcp.c
+++ b/utcp.c
@@ -808,27 +808,24 @@ static void retransmit(struct utcp_connection *c) {
 		pkt->hdr.seq = c->snd.una;
 		pkt->hdr.ack = c->rcv.nxt;
 		pkt->hdr.ctl = ACK;
-		uint32_t len = seqdiff(c->snd.last, c->snd.una);
-
-		if(len > utcp->mtu) {
-			len = utcp->mtu;
-		}
+		uint32_t len = min(seqdiff(c->snd.last, c->snd.una), utcp->mtu);
 
 		if(fin_wanted(c, c->snd.una + len)) {
 			len--;
 			pkt->hdr.ctl |= FIN;
 		}
 
-		c->snd.nxt = c->snd.una + len;
-
 		// RFC 5681 slow start after timeout
-		c->snd.ssthresh = max(c->snd.cwnd / 2, utcp->mtu * 2); // eq. 4
+		uint32_t flightsize = seqdiff(c->snd.nxt, c->snd.una);
+		c->snd.ssthresh = max(flightsize / 2, utcp->mtu * 2); // eq. 4
 		c->snd.cwnd = utcp->mtu;
 		debug_cwnd(c);
 
 		buffer_copy(&c->sndbuf, pkt->data, 0, len);
 		print_packet(c, "rtrx", pkt, sizeof(pkt->hdr) + len);
 		utcp->send(utcp, pkt, sizeof(pkt->hdr) + len);
+
+		c->snd.nxt = c->snd.una + len;
 		break;
 
 	case CLOSED:
@@ -851,6 +848,7 @@ static void retransmit(struct utcp_connection *c) {
 	}
 
 	c->rtt_start.tv_sec = 0; // invalidate RTT timer
+	c->dupack = 0; // cancel any ongoing fast recovery
 
 cleanup:
 	free(pkt);
@@ -1460,14 +1458,15 @@ synack:
 			break;
 		}
 	} else {
-		if(!len && is_reliable(c)) {
+		if(!len && is_reliable(c) && c->snd.una != c->snd.last) {
 			c->dupack++;
 			debug(c, "duplicate ACK %d\n", c->dupack);
 
 			if(c->dupack == 3) {
 				// RFC 5681 fast recovery
 				debug(c, "fast recovery started\n", c->dupack);
-				c->snd.ssthresh = max(c->snd.cwnd / 2, utcp->mtu * 2); // eq. 4
+				uint32_t flightsize = seqdiff(c->snd.nxt, c->snd.una);
+				c->snd.ssthresh = max(flightsize / 2, utcp->mtu * 2); // eq. 4
 				c->snd.cwnd = min(c->snd.ssthresh + 3 * utcp->mtu, c->sndbuf.maxsize);
 
 				if(c->snd.cwnd > c->sndbuf.maxsize) {
@@ -1486,6 +1485,11 @@ synack:
 
 				debug_cwnd(c);
 			}
+
+			// We got an ACK which indicates the other side did get one of our packets.
+			// Reset the retransmission timer to avoid going to slow start,
+			// but don't touch the connection timeout.
+			start_retransmit_timer(c);
 		}
 	}