On Mon, Jul 06, 2026 at 01:24:04PM -0300, Ricardo B. Marlière wrote:
> The IPv6 addresses used for the tun_vnet_udptnl fixture currently fall in
> the 2002::/16 prefix, which is reserved for the 6to4 transition mechanism
> (RFC 3056).
>
> On systems where the sit module is loaded, the kernel automatically claims
> 2002::/16 as a 6to4 tunnel prefix. When the test assigns a 2002:: address
> to a TUN interface, sit registers a competing local route for the same
> address. This ambiguity breaks the GENEVE decapsulation path: packets
> injected via the TUN fd are not delivered to the test socket, causing the
> IPv6-outer gtgso send_gso_packet variants to fail.
>
> Replace all four IPv6 test addresses with addresses from the fd00:db8::/32
> range, which is part of the ULA space (fc00::/7, RFC 4193) and carries no
> special kernel semantics.
>
> Fixes: 24e59f26eef2 ("selftest: tun: Add helpers for GSO over UDP tunnel")
> Signed-off-by: Ricardo B. Marlière <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
