tree 0f7f5950374804f8336aa0506c171ebcb989fb1e
parent abc5fa7ad02123a41f02bf1391c9760f7586e608
author Han-Wen Nienhuys <hanwen@google.com> 1484065815 +0100
committer Han-Wen Nienhuys <hanwen@google.com> 1484572111 +0000

ssh: rewrite (re)keying logic.

Use channels and a dedicated write loop for managing the rekeying
process.  This lets us collect packets to be written while a key
exchange is in progress.

Previously, the read loop ran the key exchange, and writers would
block if a key exchange was going on. If a reader wrote back a packet
while processing a read packet, it could block, stopping the read
loop, thus causing a deadlock.  Such coupled read/writes are inherent
with handling requests that want a response (eg. keepalive,
opening/closing channels etc.). The buffered channels (most channels
have capacity 16) papered over these problems, but under load SSH
connections would occasionally deadlock.

Fixes #18439.

Change-Id: I7c14ff4991fa3100a5d36025125d0cf1119c471d
Reviewed-on: https://go-review.googlesource.com/35012
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>