[Linux-cluster] Add option SO_LINGER to dlm sctp socket when the other endpoint is down.

[David Teigland]

On Wed, Nov 13, 2013 at 03:03:43PM +0800, Dongmao Zhang wrote:
> If I "echo b > /proc/sysrq-trigger" on cls4, cls5 will find cls4 is gone
> and try to close the sctp association.  The graceful shutdown of
> the SCTP is extremely slow, because the other endpoint has gone and can
> not answer SHUTDOWN-ACK thing.

> I suggest if we can add SO_LINGER to abort the association quickly,
> because this is not necessary to shutdown gracefully, when the endpoint
> is down. I have this patch:

There are significant subtleties involved in using SO_LINGER with tcp.
I do not know whether applying it here would be good or bad in the tcp
case, much less the sctp case.  I assume that the default tcp/sctp
behavior exists for some good reasons, and I'd like any change to be
reviewed by experts in the area.

Also, your example (sysrq) is not a compelling reason to make a change.
We do not want to risk harming any common situations for the sake of
this uncommon and avoidable one.

Dave