netdev - Re: [PATCH net] ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl

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Message-ID: <CANn89iJxmiqryxLAXiV9z4uTaCzR7XZns32MGSLOykC2zocW_Q@mail.gmail.com>
Date: Fri, 30 Jan 2026 13:00:52 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Hirokazu MORIKAWA <morikw2@...il.com>
Cc: davem@...emloft.net, eric.dumazet@...il.com, horms@...nel.org, 
	kuba@...nel.org, netdev@...r.kernel.org, pabeni@...hat.com, 
	syzbot+d4dda070f833dc5dc89a@...kaller.appspotmail.com
Subject: Re: [PATCH net] ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv()

On Fri, Jan 30, 2026 at 5:15 AM Hirokazu MORIKAWA <morikw2@...il.com> wrote:
>
> [REGRESSION] ip6_tunnel: IPv4 traffic broken in MAP-E/DS-Lite since
> commit df5ffde96693
>
> Hi,
> I am reporting a regression in the IPv6 tunneling stack (MAP-E and
> DS-Lite) introduced in kernel 6.12.67.
>
> [Description] After upgrading the kernel from 6.12.66 to 6.12.67 in
> the OpenWrt snapshot, IPv4 packets can no longer be sent to the
> external network via MAP-E or DS-Lite interfaces.
> [Environment]
> * Hardware: FriendlyElec NanoPi R6C
> * OS: OpenWrt snapshot
> * Kernel version: 6.12.67 (Broken), 6.12.66 (Working)
> * Protocol: MAP-E and DS-Lite
> [Culprit] By bisecting/reverting individual commits, I have identified
> that the following commit is responsible for this issue:
> "ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv()" (Link to
> the patch: https://lore.kernel.org/netdev/20260107163109.4188620-1-edumazet@google.com/)
> Reverting this specific commit on top of kernel 6.12.67 restores
> normal connectivity for both MAP-E and DS-Lite.
> [Steps to reproduce]
> 1. Set up a MAP-E or DS-Lite connection on kernel 6.12.67.
> 2. Attempt to send IPv4 traffic (e.g., ping 8.8.8.8).
> 3. The packets fail to reach the destination.

Thanks for the report.

Can you provide detailed instructions ?

Apparently none of our selftests caught the issue, it would be great to add one.

I have no idea what MAP-E or DS-Lite are.