rxrpc: Fix transport sockopts to get IPv4 errors on an IPv6 socket

rxrpc: Fix transport sockopts to get IPv4 errors on an IPv6 socket

BugLink: https://bugs.launchpad.net/bugs/1836654
[ Upstream commit 37a675e768d7606fe8a53e0c459c9b53e121ac20 ]

It seems that enabling IPV6_RECVERR on an IPv6 socket doesn't also turn on
IP_RECVERR, so neither local errors nor ICMP-transported remote errors from
IPv4 peer addresses are returned to the AF_RXRPC protocol.

Make the sockopt setting code in rxrpc_open_socket() fall through from the
AF_INET6 case to the AF_INET case to turn on all the AF_INET options too in
the AF_INET6 case.

Fixes: f2aeed3a591f ("rxrpc: Fix error reception on AF_INET6 sockets")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>