If the network becomes (partially) unavailable, say by disabling IPv6, the
background ACK transmission routine can get itself into a tizzy by
proposing immediate ACK retransmission. Since we're in the call event
processor, that happens immediately without returning to the workqueue
manager.
The condition should clear after a while when either the network comes back
or the call times out.
Fix this by:
(1) When re-proposing an ACK on failed Tx, don't schedule it immediately.
This will allow a certain amount of time to elapse before we try
again.
(2) Enforce a return to the workqueue manager after a certain number of
iterations of the call processing loop.
(3) Add a backoff delay that increases the delay on deferred ACKs by a
jiffy per failed transmission to a limit of HZ. The backoff delay is
cleared on a successful return from kernel_sendmsg().
(4) Cancel calls immediately if the opening sendmsg fails. The layer
above can arrange retransmission or rotate to another server.
Fixes: 248f219cb8 ("rxrpc: Rewrite the data and ack handling code")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
c7e86acfce