From: Simon Horman <horms@kernel.org>
To: "Ricardo B. Marlière" <rbm@suse.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Shuah Khan <shuah@kernel.org>, Xu Du <xudu@redhat.com>,
netdev@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] selftests/net: Fix tun IPv6 test addresses to avoid 6to4 range
Date: Mon, 13 Jul 2026 14:12:18 +0100 [thread overview]
Message-ID: <20260713131218.GE1364329@horms.kernel.org> (raw)
In-Reply-To: <20260706-b4-net_tun_addr-v1-1-3d3cb2473560@suse.com>
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 <rbm@suse.com>
Reviewed-by: Simon Horman <horms@kernel.org>
prev parent reply other threads:[~2026-07-13 13:12 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-06 16:24 [PATCH net] selftests/net: Fix tun IPv6 test addresses to avoid 6to4 range Ricardo B. Marlière
2026-07-13 13:12 ` Simon Horman [this message]
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