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

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Date:	Tue, 27 Jan 2015 02:47:54 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Vladislav Yasevich <vyasevich@...il.com>
Cc:	netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	mst@...hat.com, edumazet@...gle.com,
	Vladislav Yasevich <vyasevic@...hat.com>
Subject: Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO
 segmentation if not set.

On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich wrote:
> If the IPv6 fragment id has not been set and we perform
> fragmentation due to UFO, select a new fragment id.
> When we store the fragment id into skb_shinfo, set the bit
> in the skb so we can re-use the selected id.
> This preserves the behavior of UFO packets generated on the
> host and solves the issue of id generation for packet sockets
> and tap/macvtap devices.
> 
> This patch moves ipv6_select_ident() back in to the header file.  
> It also provides the helper function that sets skb_shinfo() frag
> id and sets the bit.
> 
> It also makes sure that we select the fragment id when doing
> just gso validation, since it's possible for the packet to
> come from an untrusted source (VM) and be forwarded through
> a UFO enabled device which will expect the fragment id.
> 
> CC: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Vladislav Yasevich <vyasevic@...hat.com>
> ---
>  include/linux/skbuff.h |  3 ++-
>  include/net/ipv6.h     |  2 ++
>  net/ipv6/ip6_output.c  |  4 ++--
>  net/ipv6/output_core.c |  9 ++++++++-
>  net/ipv6/udp_offload.c | 10 +++++++++-
>  5 files changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 85ab7d7..3ad5203 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -605,7 +605,8 @@ struct sk_buff {
>  	__u8			ipvs_property:1;
>  	__u8			inner_protocol_type:1;
>  	__u8			remcsum_offload:1;
> -	/* 3 or 5 bit hole */
> +	__u8			ufo_fragid_set:1;
[...]

Doesn't the flag belong in struct skb_shared_info, rather than struct
sk_buff?  Otherwise this looks fine.

Ben.

-- 
Ben Hutchings
When in doubt, use brute force. - Ken Thompson

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