netdev - Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set.

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Message-ID: <1422369481.29618.34.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 27 Jan 2015 06:38:01 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	vyasevic@...hat.com
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Vladislav Yasevich <vyasevich@...il.com>,
	netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	edumazet@...gle.com
Subject: Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO
 segmentation if not set.

On Tue, 2015-01-27 at 09:26 -0500, Vlad Yasevich wrote:

> That's what I originally wanted to do, but had to move and grow txflags thus
> skb_shinfo ended up growing.  I wanted to avoid that, so stole an skb flag.
> 
> I considered treating fragid == 0 as unset, but a 0 fragid is perfectly valid
> from the protocol perspective and could actually be generated by the id generator
> functions.  This may cause us to call the id generation multiple times.

With 32bit ID, you certainly can replace fragid=0 by fragid=0x80000000
and nobody will notice.

I certainly vote for not adding an extra bit in skb or skb_shared_info,
considering we already consume 32bits for this thing.

fragid are best effort, otherwise they would have 128bits.


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