tree 1fccceab4bf4efff1957a80358f7487cbbf69c53
parent cf1a6474f80735ff4a5d99f3dd68a94dbec8455f
author David Howells <dhowells@redhat.com> 1474500571 +0100
committer David Howells <dhowells@redhat.com> 1474528884 +0100

rxrpc: Send pings to get RTT data

Send a PING ACK packet to the peer when we get a new incoming call from a
peer we don't have a record for.  The PING RESPONSE ACK packet will tell us
the following about the peer:

 (1) its receive window size

 (2) its MTU sizes

 (3) its support for jumbo DATA packets

 (4) if it supports slow start (similar to RFC 5681)

 (5) an estimate of the RTT

This is necessary because the peer won't normally send us an ACK until it
gets to the Rx phase and we send it a packet, but we would like to know
some of this information before we start sending packets.

A pair of tracepoints are added so that RTT determination can be observed.

Signed-off-by: David Howells <dhowells@redhat.com>