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Date:   Mon, 27 Apr 2020 23:12:01 +0200
From:   Florent Fourcot <>
To:     Eric Dumazet <>,
        Heiner Kallweit <>
Cc:     Charles DAYMAND <>,
        netdev <>
Subject: Re: [PATCH net] r8169: fix multicast tx issue with macvlan interface

Hello Eric, Hello Heiner,

Just for a small follow-up on your questions and current status on our 
side for this strange topic:

  * As explained by Charles, the setup includes a mix of macvlan + vlan. 
So 802.1q frames are not a typo in the topic (in our real case, the 
second macvlan interface is sent to a network namespace, but it does not 
matter for the current issue).

  * We tested the same setup with other networking driver (bnx2, tg3) 
with tx-checksum enabled (exactly same configuration than the failing 
one on r8169 for checksum offloading), and it's perfectly working.

  * Packets are seen as valid by tcpdump on the sender (buggy) host.

  * Multicast *and* unicast packets are buggy. We detected it first on 
multicast (since the relevant hardware was sending RIP packets), but all 
tcp/udp packets are corrupted. ICMP packets are valid.

  * We expected as well a "simple" checksum failure, but it does not 
look so simple. Something, on our opinion probably the driver or 
hardware, is corrupting the packet.

  * Experimental patches from Heiner are not solving issue.

  * We have the same behavior on at least RTL8168d/8111d, 
RTL8169sc/8110sc and RTL8168h/8111h variants.

As proposed by Heiner, we will try to debug step by step packet path 
inside the kernel to find where it's become corrupted. But it looks time 
consuming for people like us, not really experts in driver development. 
If you have any tips or ideas concerning this topic, it could help us a lot.

Best regards,


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