netdev - RE: [PATCH] net: clear local_df when passing skb between namespaces

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Message-ID: <2134F8430051B64F815C691A62D9831816F994@XCH-BLV-504.nw.nos.boeing.com>
Date:	Thu, 5 Dec 2013 22:52:42 +0000
From:	"Templin, Fred L" <Fred.L.Templin@...ing.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] net: clear local_df when passing skb between namespaces

Concur - testing on an earlier kernel version shows that clearing
local_df solves the problem.

Fred

> -----Original Message-----
> From: Hannes Frederic Sowa [mailto:hannes@...essinduktion.org]
> Sent: Thursday, December 05, 2013 2:29 PM
> To: Templin, Fred L; netdev@...r.kernel.org
> Subject: [PATCH] net: clear local_df when passing skb between namespaces
> 
> We must clear local_df when passing the skb between namespaces as the
> packet is not local to the new namespace any more and thus may not get
> fragmented by local rules. Fred Templin noticed that other namespaces
> do fragment IPv6 packets while forwarding. Instead they should have send
> back a PTB.
> 
> The same problem should be present when forwarding DF-IPv4 packets
> between namespaces.
> 
> Reported-by: Templin, Fred L <Fred.L.Templin@...ing.com>
> Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
> ---
>  net/core/skbuff.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 2718fed..06e72d3 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -3584,6 +3584,7 @@ void skb_scrub_packet(struct sk_buff *skb, bool xnet)
>  	skb->tstamp.tv64 = 0;
>  	skb->pkt_type = PACKET_HOST;
>  	skb->skb_iif = 0;
> +	skb->local_df = 0;
>  	skb_dst_drop(skb);
>  	skb->mark = 0;
>  	secpath_reset(skb);
> --
> 1.8.3.1