On Fri, Jan 30, 2026 at 5:15 AM Hirokazu MORIKAWA [off-list ref] 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/ (local))
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.