From: Guus Sliepen <guus@meshlink.io>
Date: Fri, 5 Dec 2014 21:10:37 +0000 (+0100)
Subject: Send ACKs without a payload upon receiving an out-of-order packet.
X-Git-Url: http://git.meshlink.io/?p=utcp;a=commitdiff_plain;h=2ae2f9bbb7502589f279c329815d55ec526baffd

Send ACKs without a payload upon receiving an out-of-order packet.

This is necessary so the peer can detect "triplicate ACKs", which signal dropped packets, and at the
same time keeps the TCP self-clocking active.
---

diff --git a/utcp.c b/utcp.c
index 2ef56ea..db775a9 100644
--- a/utcp.c
+++ b/utcp.c
@@ -587,12 +587,13 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 #endif
 
 	if(!acceptable) {
-		debug("Packet not acceptable, %u  <= %u + %zu < %u\n", c->rcv.nxt, hdr.seq, len, c->rcv.nxt + c->rcv.wnd);
+		debug("Packet not acceptable, %u <= %u + %zu < %u\n", c->rcv.nxt, hdr.seq, len, c->rcv.nxt + c->rcv.wnd);
 		// Ignore unacceptable RST packets.
 		if(hdr.ctl & RST)
 			return 0;
 		// Otherwise, send an ACK back in the hope things improve.
-		goto ack;
+		ack(c, true);
+		return 0;
 	}
 
 	c->snd.wnd = hdr.wnd; // TODO: move below