Re: linux-ipsec: possibly bogus value passed to skb->dst->output

[Richard Guy Briggs]

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> On Sun, 22 Aug 1999, Richard Guy Briggs wrote:
> > I wrote:
> > > James Morris wrote:
> > > > I'll start looking at the other tunnels (ipip, gre, sit) in the 2.2 kernel
> > > > to see if there's anything simple we can try, as they use standard ip
> > > > output functions without any of these problems.
> > > 
> > > I will look at them carefully again, IPIP has changed considerably
> > > in 2.2, merging drivers/net/new_tunnel.c in with net/ipv4/ipip.c.
> > 
> > I will have to chew on this one for a while, indeed a lot has
> > changed...
> > 
> 
> I think we have some progress here.
> 
> Below is a patch which makes use of ip_send() and route/dst semantics
> for newer kernels.  

Hmmm, ip_send() has changed since 2.0.xx....this is the sort of
solution I was hoping for!

> It's pretty rough at this stage, although it does allow the large MTU
> trick to be used, and sending fragments in transport mode now works.

I noticed this.  I used your ideas, but it oopsed on the udp/500 and
IPIP/0 cases, for which I kept the original code and only called the
ip_route_output() stuff for the changed packet.  It is still oopsing
occasionally.  Perhaps it is my platform?

The headroom issue is a little odd, I had a skb_put() panic without
it.

> The next step will be to hack MSS for TCP, as per Alan's suggestion, and
> find out if anything is broken.

Right...

> I'm not experienced with this area of the kernel, so any input from
> (non-us, alas) network people would be most appreciated.

Thanks for the ideas...and time to study ipip.c some more.

> - James
> --
> James Morris
> <[e-mail]>

> +	/* new route/dst cache stuff */
> +        if (ip_route_output(&rt, skb->nh.iph->daddr, skb->nh.iph->saddr, 
> +                            RT_TOS(skb->nh.iph->tos), physdev->iflink)) {
> +		stats->tx_errors++;
> +		goto cleanup;
> +	}
> +	dst_release(skb->dst);
> +	skb->dst = &rt->u.dst;
> +	stats->tx_bytes += skb->len;
> +	ip_send(skb);

	slainte mhath, RGB
- -- 
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