netdev - Re: virt-manager broken by bind(0) in net-next.

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Date:	Sat, 31 Jan 2009 21:29:09 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	Evgeniy Polyakov <zbr@...emap.net>, berrange@...hat.com,
	et-mgmt-tools@...hat.com, davem@...emloft.net,
	netdev@...r.kernel.org
Subject: Re: virt-manager broken by bind(0) in net-next.

On Fri, 30 Jan 2009 19:41:59 +0100
Eric Dumazet <dada1@...mosbay.com> wrote:

> Stephen Hemminger a écrit :
> > On Fri, 30 Jan 2009 23:53:37 +1100
> > Herbert Xu <herbert@...dor.apana.org.au> wrote:
> > 
> >> Evgeniy Polyakov <zbr@...emap.net> wrote:
> >>> So it is not explicit bind call, but port autoselection in the
> >>> connect(). Can you check what errno is returned?
> >>> Did I understand it right, that connect fails, you try different
> >>> address, but then suddenly all those sockets become 'alive'?
> >> Yes, I think a good strace vs. a bad strace would be really helpful
> >> in these cases.
> >>
> >> Thanks,
> > 
> > I have the strace but it comes up no different.
> > What is different is that in the broken case (net-next), I see
> > IPV6 being used:
> > 
> > State      Recv-Q Send-Q      Local Address:Port          Peer Address:Port   
> > ESTAB      23769  0        ::ffff:127.0.0.1:5900      ::ffff:127.0.0.1:55987   
> > ESTAB      0      0               127.0.0.1:55987            127.0.0.1:5900
> > 
> > and in the working case (2.6.29-rc3), IPV4 is being used
> > State      Recv-Q Send-Q      Local Address:Port          Peer Address:Port   
> > ESTAB      0      0               127.0.0.1:58894            127.0.0.1:5901    
> > ESTAB      0      0               127.0.0.1:5901             127.0.0.1:58894 
> > 
> 
> Reviewing commit a9d8f9110d7e953c2f2b521087a4179677843c2a
> 
> I see use of a hashinfo->bsockets field that :
> 
> - lacks proper lock/synchronization
> - suffers from cache line ping pongs on SMP
> 
> Also there might be a problem at line 175
> 
> if (sk->sk_reuse && sk->sk_state != TCP_LISTEN && --attempts >= 0) { 
> 	spin_unlock(&head->lock);
> 	goto again;
> 
> If we entered inet_csk_get_port() with a non null snum, we can "goto again"
> while it was not expected.
> 
> diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
> index df8e72f..752c6b2 100644
> --- a/net/ipv4/inet_connection_sock.c
> +++ b/net/ipv4/inet_connection_sock.c
> @@ -172,7 +172,8 @@ tb_found:
>  		} else {
>  			ret = 1;
>  			if (inet_csk(sk)->icsk_af_ops->bind_conflict(sk, tb)) {
> -				if (sk->sk_reuse && sk->sk_state != TCP_LISTEN && --attempts >= 0) {
> +				if (sk->sk_reuse && sk->sk_state != TCP_LISTEN &&
> +					smallest_size == -1 &&  --attempts >= 0) {
>  					spin_unlock(&head->lock);
>  					goto again;
>  				}
> 
> 

That didn't fix it.
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