netdev - Re: [PATCH v2.41 5/5] datapath: Add basic MPLS support to kernel

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Date:	Thu, 3 Oct 2013 19:46:46 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Simon Horman <horms@...ge.net.au>
Cc:	"dev@...nvswitch.org" <dev@...nvswitch.org>,
	netdev <netdev@...r.kernel.org>, Jesse Gross <jesse@...ira.com>,
	Ben Pfaff <blp@...ira.com>, Ravi K <rkerur@...il.com>,
	Isaku Yamahata <yamahata@...inux.co.jp>,
	Joe Stringer <joe@...d.net.nz>
Subject: Re: [PATCH v2.41 5/5] datapath: Add basic MPLS support to kernel

On Wed, Oct 2, 2013 at 5:20 PM, Simon Horman <horms@...ge.net.au> wrote:
> On Wed, Oct 02, 2013 at 11:03:57AM -0700, Pravin Shelar wrote:
>> On Mon, Sep 30, 2013 at 11:47 PM, Simon Horman <horms@...ge.net.au> wrote:
>> > Allow datapath to recognize and extract MPLS labels into flow keys
>> > and execute actions which push, pop, and set labels on packets.
>> >
>> > Based heavily on work by Leo Alterman, Ravi K, Isaku Yamahata and Joe Stringer.
>> >
>> > Cc: Ravi K <rkerur@...il.com>
>> > Cc: Leo Alterman <lalterman@...ira.com>
>> > Cc: Isaku Yamahata <yamahata@...inux.co.jp>
>> > Cc: Joe Stringer <joe@...d.net.nz>
>> > Signed-off-by: Simon Horman <horms@...ge.net.au>
>> >
>> > ---
>> >
>> > +
>> > +       /* this hack needed to get regular skb_gso_segment() */
>> > +#ifdef HAVE___SKB_GSO_SEGMENT
>> > +#undef __skb_gso_segment
>> > +       skb_gso = __skb_gso_segment(skb, features, tx_path);
>> > +#else
>> > +#undef skb_gso_segment
>> > +       skb_gso = skb_gso_segment(skb, features);
>> > +#endif
>> > +
>>
>> We can get rid of #ifdefs by just using different name for
>> rpl___skb_gso_segment(), something like mpls_vlan_skb_gso_segment().
>> The way it is done for tnl-gso.
>
> Thanks.
>
> The reason that I had the code arranged this way was so that
> calls to __skb_gso_segment() would go via rpl___skb_gso_segment()
> on kernels older than v3.11. In particular calls outside of gso.c.
>
> On closer examination the only such case is in ovs_dp_upcall().
> Currently there should be no need to perform MPLS GSO segmentation in that
> case because MPLS GSO segmentation can only be needed after actions are
> applied.
>
> However, I am concerned that it may be necessary later when
> recirculation is introduced as in that case an upcall may occur
> on a packet which has had actions applied.

good point.

currently we define __skb_gso_segment using skb_gso_segemt(). You have
reversed it. Is there any reason?
if you keep it as it is, it can simplify code a bit.
--
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