Re: [PATCH net-next v6 2/2] selftests: net: add FOU multicast encapsulation resubmit test

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Anton Danilov wrote:
> Add a selftest to verify that FOU-encapsulated packets addressed to a
> multicast destination are correctly resubmitted to the inner protocol
> handler (GRE) via the UDP multicast delivery path.  Both IPv4 and IPv6
> paths are tested.
> 
> The test creates two network namespaces connected by a veth pair with
> a FOU/GRETAP (IPv4) and FOU/ip6gretap (IPv6) tunnel using multicast
> remote addresses (239.0.0.1 and ff0e::1).  Ping is sent through each
> tunnel and received packets are counted on the receiver's tunnel
> interface.
> 
> The veth pair is created directly inside the namespaces to avoid
> possible name collisions with devices in the root namespace.
> 
> Static neighbor entries are configured on the sender because ARP/ND
> replies from the receiver cannot traverse the unidirectional multicast
> tunnel back to the sender.
> 
> The early demux optimization (net.ipv4.ip_early_demux, which controls
> both IPv4 and IPv6) is disabled on the receiver to force packets
> through __udp4_lib_mcast_deliver() / __udp6_lib_mcast_deliver(), which
> is the code path being tested.
> 
> Signed-off-by: Anton Danilov <littlesmilingcloud@gmail.com>
> Assisted-by: Claude:claude-opus-4-6

Reviewed-by: Willem de Bruijn <willemb@google.com>

> +setup_ipv4() {
> +	# IPv4 FOU (CONFIG_NET_FOU) is built in on kernels configured for

Instead of this distinction and modprobe for IPv6, also set those new
CONFIGs to =Y, so that the two are equivalent?

Not important enough to respin.