netdev - Re: [PATCH net] Revert "ipv6: Allow for partial checksums on non-ufo packets"

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Date:	Tue, 12 May 2015 12:07:38 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Vlad Yasevich <vyasevich@...il.com>
Cc:	Wolfgang Walter <linux@...m.de>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] Revert "ipv6: Allow for partial checksums on
 non-ufo packets"

On Tue, 2015-05-12 at 14:05 -0400, Vlad Yasevich wrote:
> On 05/08/2015 06:22 PM, Eric Dumazet wrote:
> > From: Eric Dumazet <edumazet@...gle.com>
> > 
> > Wolfgang Walter reported crashes using traceroute6, root caused to this
> > commit.
> > 
> > UDP packets can be sent from RAW sockets.
> > 
> > Note that the faulty commit addressed a non problem, as normal
> > UDP v6 packets use udp_v6_send_skb() which correctly setup
> > CHECKSUM_PARTIAL properly if device has the correct feature.
> 
> Actually, they didn't.  udp_v6_send_skb() uses ip_summed from
> the skb, which is populated by __ip6_append_data.  That in turn
> always set it CHECKSUM_NONE.
> 
> The code in question looks identically to that of __ip_append_data().
> The problem is similar in both places.

Well, one is crashing the host. IPv4 raw must have been OK, not IPv6.

As I explained in the changelog, you can try to fix
rawv6_push_pending_frames()

My opinion is that a reasonable strategy is to revert for stable
kernels.

Then if you can fix rawv6_push_pending_frames() for net-next, I will be
happy to review your patch.



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