From: Shmulik Ladkani <shmulik.ladkani@gmail.com>
To: Eli Cooper <elicooper@gmx.com>
Cc: Tom Herbert <tom@herbertland.com>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
"David S . Miller" <davem@davemloft.net>
Subject: Re: [PATCH v2] ip6_tunnel: Clear IP6CB in ip6_tnl_xmit() after encapsulation
Date: Fri, 28 Oct 2016 19:07:57 +0300 [thread overview]
Message-ID: <20161028190757.26be756c@halley> (raw)
In-Reply-To: <9a1bb72b-246d-021a-236c-f523832964ac@gmx.com>
Hi,
On Fri, 28 Oct 2016 13:13:45 +0800 Eli Cooper <elicooper@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
next prev parent reply other threads:[~2016-10-28 16:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-28 1:52 [PATCH v2] ip6_tunnel: Clear IP6CB in ip6_tnl_xmit() after encapsulation Eli Cooper
2016-10-28 2:17 ` Tom Herbert
2016-10-28 5:13 ` Eli Cooper
2016-10-28 16:07 ` Shmulik Ladkani [this message]
2016-10-31 18:18 ` David Miller
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