From d6f18182c43287c180e637046c044e8bff5e7064 Mon Sep 17 00:00:00 2001
From: Guus Sliepen <guus@sliepen.org>
Date: Sun, 8 Mar 2020 21:52:23 +0100
Subject: [PATCH] Always announce the receive window size as the size of the
 receive buffer.

Since UTCP requires the application to handle incoming in-sequence data
immediately, the start of the receive buffer is always right after the
last ACKed byte, so we can always announce the size of the receive buffer
as the maximum receive window size.
---
 utcp.c      | 9 ++++-----
 utcp_priv.h | 1 -
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/utcp.c b/utcp.c
index 5d63069..d2a777c 100644
--- a/utcp.c
+++ b/utcp.c
@@ -382,7 +382,6 @@ static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t s
 #endif
 	c->snd.una = c->snd.iss;
 	c->snd.nxt = c->snd.iss + 1;
-	c->rcv.wnd = utcp->mtu;
 	c->snd.last = c->snd.nxt;
 	c->snd.cwnd = utcp->mtu;
 	c->utcp = utcp;
@@ -468,7 +467,7 @@ struct utcp_connection *utcp_connect_ex(struct utcp *utcp, uint16_t dst, utcp_re
 	pkt.hdr.dst = c->dst;
 	pkt.hdr.seq = c->snd.iss;
 	pkt.hdr.ack = 0;
-	pkt.hdr.wnd = c->rcv.wnd;
+	pkt.hdr.wnd = c->rcvbuf.maxsize;
 	pkt.hdr.ctl = SYN;
 	pkt.hdr.aux = 0x0101;
 	pkt.init[0] = 1;
@@ -538,7 +537,7 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
 	pkt->hdr.src = c->src;
 	pkt->hdr.dst = c->dst;
 	pkt->hdr.ack = c->rcv.nxt;
-	pkt->hdr.wnd = c->snd.wnd;
+	pkt->hdr.wnd = c->rcvbuf.maxsize;
 	pkt->hdr.ctl = ACK;
 	pkt->hdr.aux = 0;
 
@@ -697,7 +696,7 @@ 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.wnd = c->rcvbuf.maxsize;
 	pkt->hdr.aux = 0;
 
 	switch(c->state) {
@@ -1073,7 +1072,7 @@ synack:
 			pkt.hdr.dst = c->dst;
 			pkt.hdr.ack = c->rcv.irs + 1;
 			pkt.hdr.seq = c->snd.iss;
-			pkt.hdr.wnd = c->rcv.wnd;
+			pkt.hdr.wnd = c->rcvbuf.maxsize;
 			pkt.hdr.ctl = SYN | ACK;
 
 			if(init) {
diff --git a/utcp_priv.h b/utcp_priv.h
index 6c5c1f8..c23279d 100644
--- a/utcp_priv.h
+++ b/utcp_priv.h
@@ -129,7 +129,6 @@ struct utcp_connection {
 
 	struct {
 		uint32_t nxt;
-		uint32_t wnd;
 		uint32_t irs;
 	} rcv;
 
-- 
2.39.2