mptcp: sockopt: support IP_LOCAL_PORT_RANGE and IP_BIND_ADDRESS_NO_PORT

mptcp: sockopt: support IP_LOCAL_PORT_RANGE and IP_BIND_ADDRESS_NO_PORT

Support for IP_BIND_ADDRESS_NO_PORT sockopt was introduced in [1].
Recently [2] allowed its value to be accessed without locking the
socket.

Support for (newer) IP_LOCAL_PORT_RANGE sockopt was introduced in [3].
In the same series a selftest was added in [4]. This selftest also
covers the IP_BIND_ADDRESS_NO_PORT sockopt.

This patch enables getsockopt()/setsockopt() on MPTCP sockets for these
socket options, syncing set values to subflows in sync_socket_options().
Ephemeral port range is synced to subflows, enabling NAT usecase
described in [3].

[1] commit 90c337da1524 ("inet: add IP_BIND_ADDRESS_NO_PORT to overcome
bind(0) limitations")
[2] commit ca571e2eb7eb ("inet: move inet->bind_address_no_port to
inet->inet_flags")
[3] commit 91d0b78c5177 ("inet: Add IP_LOCAL_PORT_RANGE socket option")
[4] commit ae5439658cce ("selftests/net: Cover the IP_LOCAL_PORT_RANGE
socket option")

Signed-off-by: Maxim Galaganov <max@internet.ru>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>