netdev - Re: IPv6-UDP 0x0000 checksum

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Message-ID: <1485444476.5145.136.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Thu, 26 Jan 2017 07:27:56 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     netdev@...r.kernel.org,
        linux-wireless <linux-wireless@...r.kernel.org>
Subject: Re: IPv6-UDP 0x0000 checksum

On Thu, 2017-01-26 at 07:24 -0800, Eric Dumazet wrote:
> On Thu, 2017-01-26 at 15:49 +0100, Johannes Berg wrote:
> 
> > Unfortunately, I haven't been able to actually test this yet. I also
> > didn't find the code that would drop frames with CSUM 0 either, so I'm
> > thinking - for now - that if all the csum handling is skipped, dropping
> > 0 csum frames would also be, and then we'd accept a frame we should
> > actually have dropped.
> > 
> > I'll go test this I guess :)
> > 
> > Any pointers to where 0 csum frames are dropped?
> 
> Probably in udp6_csum_init()

vi +804 net/ipv6/udp.c

                if (!uh->check && !udp_sk(sk)->no_check6_rx) {
                        udp6_csum_zero_error(skb);
                        goto csum_error;
                }