Subject: Re: [PATCH] ip_forward: Drop frames with attached skb->sk

From: Sebastian Poehn <[email-masked]>
Date: Tue, 14 Apr 2015 08:40:08 +0200

On Tue, 2015-04-14 at 14:33 +0800, yzhu1 wrote:
> On 04/14/2015 01:52 PM, Sebastian Poehn wrote:
> > Initial discussion was:
> > [FYI] xfrm: Don't lookup sk_policy for timewait sockets
> >
> > Forwarded frames should not have a socket attached. Especially
> > tw sockets will lead to panics later-on in the stack.
> >
> > This was observed with TPROXY assigning a tw socket and broken
> > policy routing (misconfigured). As a result frame enters
> > forwarding path instead of input. We cannot solve this in
> > TPROXY as it cannot know that policy routing is broken.
> >
> > Signed-off-by: Sebastian Poehn <[email-masked]>
> > ---
> > diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
> > index 939992c..2fc3b3e 100644
> > --- a/net/ipv4/ip_forward.c
> > +++ b/net/ipv4/ip_forward.c
> > @@ -82,6 +82,10 @@ int ip_forward(struct sk_buff *skb)
> >   	if (skb->pkt_type != PACKET_HOST)
> >   		goto drop;
> >   
> > +	/* this should happen neither */
> Sorry. "neither" should be "either"?

        /* that should never happen */
        if (skb->pkt_type != PACKET_HOST)
                goto drop;

        /* this should happen neither */
        if (unlikely(skb->sk))
                goto drop;

Both of them should never happen.

> 
> Zhu Yanjun
> > +	if (unlikely(skb->sk))
> > +		goto drop;
> > +
> >   	if (skb_warn_if_lro(skb))
> >   		goto drop;
> > --
> >
> >
> > --
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> >
>