netdev - Re: [PATCH v2] sctp: Implement quick failover draft from tsvwg

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Date:	Thu, 19 Jul 2012 09:54:19 -0700
From:	Joe Perches <joe@...ches.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	netdev@...r.kernel.org, Vlad Yasevich <vyasevich@...il.com>,
	Sridhar Samudrala <sri@...ibm.com>,
	"David S. Miller" <davem@...emloft.net>, linux-sctp@...r.kernel.org
Subject: Re: [PATCH v2] sctp: Implement quick failover draft from tsvwg

On Thu, 2012-07-19 at 06:45 -0400, Neil Horman wrote:
> On Wed, Jul 18, 2012 at 01:30:58PM -0700, Joe Perches wrote:
> > On Wed, 2012-07-18 at 14:01 -0400, Neil Horman wrote:
> > > I've seen several attempts recently made to do quick failover of sctp transports
> > > by reducing various retransmit timers and counters.  While its possible to
> > > implement a faster failover on multihomed sctp associations, its not
> > > particularly robust, in that it can lead to unneeded retransmits, as well as
> > > false connection failures due to intermittent latency on a network.
[]
> > > @@ -878,12 +896,15 @@ void sctp_assoc_control_transport(struct sctp_association *asoc,
> > []
> > > +	if (ulp_notify) {
> > > +		memset(&addr, 0, sizeof(struct sockaddr_storage));
> > > +		memcpy(&addr, &transport->ipaddr,
> > > +		       transport->af_specific->sockaddr_len);
> > 
> > Perhaps it's better to do the memcpy then the memset of the
> > space left instead.
> > 
> > 		memcpy(&addr, &transport->ipaddr, transport->af_specific->sockaddr_len);
> > 		memset((char *)&addr) + transport->af_specific->sockaddr_len, 0,
> > 		       sizeof(struct sockaddr_storage) - transport->af_specific->sockaddr_len);
> > 
> hmm, not sure about that. It works either way for me, but I've not changed that
> code, just the condition under which it was executed.  I'd rather save cleanups
> like that for a separate patch if you don't mind.

Not a bit.

It's almost certain reversing the order is slower for v4
addresses anyway.  It might be slower for v6 too given
the arithmetic.

cheers, Joe

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