bareudp: Pull inner IP header in bareudp_udp_encap_recv().

[ Upstream commit 45fa29c8 ]

Bareudp reads the inner IP header to get the ECN value. Therefore, it
needs to ensure that it's part of the skb's linear data.

This is similar to the vxlan and geneve fixes for that same problem:
  * commit f7789419 ("vxlan: Pull inner IP header in vxlan_rcv().")
  * commit 1ca1ba46 ("geneve: make sure to pull inner header in
    geneve_rx()")

Fixes: 571912c6 ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/5205940067c40218a70fbb888080466b2fc288db.1726046181.git.gnault@redhat.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>