mptcp: Add MPTCP socket stubs

Implements the infrastructure for MPTCP sockets.

MPTCP sockets open one in-kernel TCP socket per subflow. These subflow
sockets are only managed by the MPTCP socket that owns them and are not
visible from userspace. This commit allows a userspace program to open
an MPTCP socket with:

  sock = socket(AF_INET, SOCK_STREAM, IPPROTO_MPTCP);

The resulting socket is simply a wrapper around a single regular TCP
socket, without any of the MPTCP protocol implemented over the wire.

Co-developed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Co-developed-by: Peter Krystad <peter.krystad@linux.intel.com>
Signed-off-by: Peter Krystad <peter.krystad@linux.intel.com>
Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Co-developed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/net/Kconfig b/net/Kconfig
index 54916b7adb9b..b0937a700f01 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -91,6 +91,7 @@ if INET
 source "net/ipv4/Kconfig"
 source "net/ipv6/Kconfig"
 source "net/netlabel/Kconfig"
+source "net/mptcp/Kconfig"
 
 endif # if INET