Fix IPv6 support in AF_RXRPC in the following ways:
(1) When extracting the address from a received IPv4 packet, if the local
transport socket is open for IPv6 then fill out the sockaddr_rxrpc
struct for an IPv4-mapped-to-IPv6 AF_INET6 transport address instead
of an AF_INET one.
(2) When sending CHALLENGE or RESPONSE packets, the transport length needs
to be set from the sockaddr_rxrpc::transport_len field rather than
sizeof() on the IPv4 transport address.
(3) When processing an IPv4 ICMP packet received by an IPv6 socket, set up
the address correctly before searching for the affected peer.
Signed-off-by: David Howells <dhowells@redhat.com>
7b674e390e