netdev - Re: [PATCH net-2.6.22-rc7] xfrm beet interfamily support

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Date:	Tue, 31 Jul 2007 13:39:39 +0300
From:	Joakim Koskela <joakim.koskela@...t.fi>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: [PATCH net-2.6.22-rc7] xfrm beet interfamily support

On Thursday 19 July 2007 17:46:42 Patrick McHardy wrote:
> Joakim Koskela wrote:
> > +		skb_push(skb, hdrlen);
> > +		iphv6 = ipv6_hdr(skb);
> > +
> > +		skb_reset_network_header(skb);
> > +		top_iphv6 = ipv6_hdr(skb);
> > +
> > +		protocol = iphv6->nexthdr;
> > +		skb_pull(skb, delta);
> > +		skb_reset_network_header(skb);
> > +		top_iphv4 = ip_hdr(skb);
> > +		skb_set_transport_header(skb, hdrlen);
> > +		top_iphv4->ihl = (sizeof(struct iphdr) >> 2);
> > +		top_iphv4->version = 4;
> > +		top_iphv4->id = 0;
> > +		top_iphv4->frag_off = htons(IP_DF);
> > +		top_iphv4->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
> > +		top_iphv4->saddr = x->props.saddr.a4;
> > +		top_iphv4->daddr = x->id.daddr.a4;
> > +		skb->transport_header += top_iphv4->ihl*4;
> > +		top_iphv4->protocol = protocol;
> > +
> > +		skb->protocol = htons(ETH_P_IP);
> > +#endif
>
> The output function in the IPv6/IPv4 case is called from
> xfrm6_output_one, which loops until after a tunnel mode
> encapsulation is done and then returns to the outer loop
> in xfrm6_output_finish2, which passes the packet through
> the netfilter hooks and continues with the next transform.
>

I'm not sure I really got this. IPv6/IPv4 means IPv6 inner, IPv4 outer, right? 
Isn't that called from xfrm4_output_one and subsequently passed through the 
right filters as well (as it has a ipv4 header by then)?

> There are multiple problems resulting from the inter-family
> encapsulation. First of all, the inner loop continues after
> beet mode encapsulation, skipping the netfilter hooks in
> case there are more transforms. It should (as with decaps = 1
> on input) at least call netfilter hooks after an inter-family
> transform. If the beet transform is the last one, the IPv4
> skb will be passed through the IPv6 netfilter hooks, which is
> clearly wrong. To fix these problems some restructuring in
> xfrm[46]_output.c seems to be necessary.

Couldn't this be solved just by ending the inner loop in case of beet mode (as 
it is done for tunnel)?

br, j

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