mptcp: sockopt: fix getting freebind & transparent

commit e2f4ac7b upstream.

When adding a socket option support in MPTCP, both the get and set parts
are supposed to be implemented.

IP(V6)_FREEBIND and IP(V6)_TRANSPARENT support for the setsockopt part
has been added a while ago, but it looks like the get part got
forgotten. It should have been present as a way to verify a setting has
been set as expected, and not to act differently from TCP or any other
socket types.

Everything was in place to expose it, just the last step was missing.
Only new code is added to cover these specific getsockopt(), that seems
safe.

Fixes: c9406a23 ("mptcp: sockopt: add SOL_IP freebind & transparent options")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250314-net-mptcp-fix-data-stream-corr-sockopt-v1-3-122dbb249db3@kernel.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>
[ Conflict in sockopt.c due to commit e08d0b3d ("inet: implement
  lockless IP_TOS") not being in this version. The conflict is in the
  context and the modification can still be applied in
  mptcp_getsockopt_v4() after the IP_TOS case.
  Also, get the values without 'inet_test_bit()' like it was done in
  this version. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>