Re: sockets affected by IPsec always block (2.6.23)

[David Miller <davem@davemloft.net>]

From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Wed, 5 Dec 2007 18:39:27 +1100

> On Tue, Dec 04, 2007 at 11:34:32PM -0800, David Miller wrote:
> > 
> > TCP has some built-in assumptions about characteristics of
> > interent links and what constitutes a timeout which is "too long"
> > and should thus result in a full connection failure.
> > 
> > IPSEC changes this because of IPSEC route resolution via
> > ISAKMP.
> > 
> > With this in mind I can definitely see people preferring
> > the "block until IPSEC resolves" behavior, especially for
> > something like, say, periodic remote backups and stuff like
> > that where you really want the thing to just sit and wait
> > for the connect() to succeed instead of failing.
> 
> Hmm, but connect(2) should succeed in that case thanks to the
> blackhole route, no? The subsequent SYNs will then be dropped
> until the IPsec SAs are in place.

If it hits sysctl_tcp_syn_retries SYN attempts, the connect will hard
fail.