Re: Connect hangs for a while before returns -1 with ECONNREFUSED on 3.2 for loopback

Julian Anastasov
2012-02-04T15:48:15Z

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Hello,

On Sat, 4 Feb 2012, Eric Dumazet wrote:

> Le vendredi 03 février 2012 à 16:15 +0100, Eric Dumazet a écrit :
>
> > We omit to send RST packet in tcp_v4_send_reset()
> >
> > because of this test :
> >
> > if (skb_rtable(skb)->rt_type != RTN_LOCAL)
> > return
> >
> > At this point rt_type is RTN_UNICAST
>
> Here is the fix, thanks again !
>
> [PATCH] ipv4: fix a route regression
>
> commit 813b3b5db83 (ipv4: Use caller's on-stack flowi as-is in output
> route lookups.) added a regression.
>
> Some callers of ip_route_output_slow() assumed their flow argument was
> constant.

Problem with ip_route_connect?

> ip_route_output_slow() must leave with original content of various
> fields.

There were attempts to provide more results for
xfrm purposes:

http://marc.info/?t=132251214300008&r=1&w=2

So, may be we need to go in this direction, not
to restore original values but to provide more results.
And callers should initialize all input arguments.

> Thanks to Yurij M. Plotnikov for providing a bug report including a
> program to reproduce the problem.
>
> Reported-by: Yurij M. Plotnikov <Yurij.Plotnikov@oktetlabs.ru>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> ---
> net/ipv4/route.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index bcacf54..0f63240 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -2633,19 +2633,15 @@ static struct rtable *ip_route_output_slow(struct net *net, struct flowi4 *fl4)
> unsigned int flags = 0;
> struct fib_result res;
> struct rtable *rth;
> - __be32 orig_daddr;
> - __be32 orig_saddr;
> - int orig_oif;
> + __be32 orig_daddr = fl4->daddr;
> + __be32 orig_saddr = fl4->saddr;
> + int orig_oif = fl4->flowi4_oif;
>
> res.fi = NULL;
> #ifdef CONFIG_IP_MULTIPLE_TABLES
> res.r = NULL;
> #endif
>
> - orig_daddr = fl4->daddr;
> - orig_saddr = fl4->saddr;
> - orig_oif = fl4->flowi4_oif;
> -
> fl4->flowi4_iif = net->loopback_dev->ifindex;
> fl4->flowi4_tos = tos & IPTOS_RT_MASK;
> fl4->flowi4_scope = ((tos & RTO_ONLINK) ?
> @@ -2816,6 +2812,9 @@ make_route:
>
> out:
> rcu_read_unlock();
> + fl4->flowi4_oif = orig_oif;
> + fl4->daddr = orig_daddr;
> + fl4->saddr = orig_saddr;

flowi4_tos is missing from this list but anyways,
it looks wrong because __ip_route_output_key returns data
in saddr and daddr, such change will break source address
autoselection and destination address autoselection. That is
what ip_route_connect is trying to do. May be
ip_route_connect should be fixed instead?

> return rth;
> }

Regards

--
Julian Anastasov <ja@ssi.bg>