From 526d314266f1648ae79d8cdd380edb371fb69e4b Mon Sep 17 00:00:00 2001
From: Michael Brown
Date: Sat, 13 Jan 2007 17:36:17 +0000
Subject: Advertise a larger MSS to improve TCP performance.

---
 src/include/gpxe/tcp.h | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

(limited to 'src/include')

diff --git a/src/include/gpxe/tcp.h b/src/include/gpxe/tcp.h
index f9cd41390..c8988cf52 100644
--- a/src/include/gpxe/tcp.h
+++ b/src/include/gpxe/tcp.h
@@ -27,6 +27,18 @@ struct tcp_header {
 	uint16_t urg;		/* Urgent pointer */
 };
 
+/**
+ * TCP MSS option
+ */
+struct tcp_mss_option {
+	uint8_t kind;
+	uint8_t length;
+	uint16_t mss;
+};
+
+/** Code for the TCP MSS option */
+#define TCP_OPTION_MSS 2
+
 /*
  * TCP flags
  */
@@ -212,7 +224,17 @@ struct tcp_header {
  * guess an arbitrary number that is empirically as large as possible
  * while avoiding retransmissions due to dropped packets.
  */
-#define TCP_WINDOW_SIZE	2048
+#define TCP_WINDOW_SIZE	4096
+
+/**
+ * Advertised TCP MSS
+ *
+ * We currently hardcode this to a reasonable value and hope that the
+ * sender uses path MTU discovery.  The alternative is breaking the
+ * abstraction layer so that we can find out the MTU from the IP layer
+ * (which would have to find out from the net device layer).
+ */
+#define TCP_MSS 1460
 
 /** TCP maximum segment lifetime
  *
-- 
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