Hi,
On Fri, 28 Oct 2016 13:13:45 +0800 Eli Cooper <elicoo...@gmx.com> wrote:
> So I think it is best that all the
> IP6CB gets cleared before it is pushed to the next layer.
Just a comparison to the ipv4 world:
All tunnels (udp/ip based) end up calling iptunnel_xmit(), which:
- scrubs the skb
- clears any IPCB residues
- installs the iphdr
- invokes ip_local_out()
OTOH ip6_tnl_xmit:
- scrubs the skb
- installs the ipv6hdr
- invokes ip6tunnel_xmit() - a thin wrapper to ip6_local_out()
* missing: clearing cb
And OTOH udp_tunnel6_xmit_skb:
- clears IPCB(skb)->opt and some IPCB(skb)->flags
(why these 2 explicitly? and why at this point? and IPCB is no longer
relevant...)
- installs the ipv6hdr
- invokes ip6tunnel_xmit() - a thin wrapper to ip6_local_out()
* missing: scrub, clearing cb
> Maybe we
> should clear IP6CB in ip6tunnel_xmit(), rather than in every tunnel's codes?
This seems reasonable.
A potential issue might be whether it needs to be done earlier, although
I've reviewed current versions of both 'ip6_tnl_xmit' and
'udp_tunnel6_xmit_skb' and it looks okay. But please verify.
> By the way, I don't see any point in setting IPCB(skb)->flags in
> udp_tunnel6_xmit_skb(). It will not be interpreted as IPCB any further
> past ip6tunnel_xmit(), even if it were not cleared. Plus, nothing seems
> to use these flags anyway.
This seems right.
It was introduced in 6a93cc9052 "udp-tunnel: Add a few more UDP tunnel APIs".
If you checkout that tree, you'll notice same treatment to
IPCB(skb)->opt and IPCB(skb)->flags in l2tp_xmit_skb... maybe it was
just copied ;-)
Best,
Shmulik
