BGP: Send hold timer

Implement BGP Send hold timer according to draft-ietf-idr-bgp-sendholdtimer.
The Send hold timer drops the session if the neighbor is sending keepalives,
but does not receive our messages, causing the TCP connection to stall.

1 files changed, 17 insertions, 0 deletions

diff --git a/doc/bird.sgml b/doc/bird.sgml
index 10c6f121..8834c1cb 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -3157,6 +3157,23 @@ using the following configuration parameters:
 	negotiation. If the proposed hold time would lead to a lower value of
 	the keepalive time, the session is rejected with error. Default: none.
 
+	<tag><label id="bgp-send-hold-time">send hold time <m/number/</tag>
+	Maximum time in seconds betweeen successfull transmissions of BGP messages.
+	Send hold timer drops the session if the neighbor is sending keepalives,
+	but does not receive our messages, causing the TCP connection to stall.
+	This may happen due to malfunctioning or overwhelmed neighbor. See
+	<HTMLURL URL="https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-sendholdtimer/"
+	name="draft-ietf-idr-bgp-sendholdtimer"> for more details.
+
+	Like the option <cf/keepalive time/, the effective value depends on the
+	negotiated hold time, as it is scaled to maintain proportion between the
+	send hold time and the keepalive time. If it is set to zero, the timer
+	is disabled. Default: double of the hold timer limit.
+
+	The option <cf/disable rx/ is intended only for testing this feature and
+	should not be used anywhere else. It discards received messages and
+	disables the hold timer.
+
 	<tag><label id="bgp-connect-delay-time">connect delay time <m/number/</tag>
 	Delay in seconds between protocol startup and the first attempt to
 	connect. Default: 5 seconds.