mptcp: Fullmesh: events are either v4 or v6

So, as the event is always either v4 or v6 we can always increase
add_addr. The if-statements do not make any sense...

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
mptcp: Remove 0-set of rcvq_space in tcp_create_openreq_child

This is not necessary, as the rcvq_space is already initialized in
tcp_init_buffer_space.

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
mptcp: Remove some indentations in mptcp_rcv_state_process

Like 1f6afc81088a1 (tcp: remove one indentation level in
tcp_rcv_state_process()), we can remove some indentation levels in
mptcp_rcv_state_process.

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
mptcp: Move some extern declarations inside ifdef CONFIG_MPTCP

They are not used outside MPTCP and if, they are surrounded by ifdef
CONFIG_MPTCP.
Also, remove mptcpv6_prot, as it is not used anywhere.

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
mptcp: Checkpatch cleanup

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
mptcp: ndiffports - transform the sysctl to a tunable knob in sysfs

Using sysctl's too extensively is considered bad by the
kernel-community.
Tunables that are per-module should go into the sysfs.

This patch moves the sysctl ndiffports to the sysfs.
It can now be set with:

echo "4" > /sys/module/mptcp_ndiffports/parameters/num_subflows

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
mptcp: Change name of Coupled to Lia

In the literature it is commonly reffered to as "Lia".

Change the name thus from "coupled" to "lia" as suggested by Costin
Raiciu

Suggested-by: Costin Raiciu <costin.raiciu@cs.pub.ro>
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
mptcp: Remove pending request-sockets

In MPTCP, we do not handle retransmissions of SYN/ACK+MP_JOIN, because
in regular TCP this (ab)uses the keepalive timer. So, for MPTCP we
decided to not retransmit these SYN/ACKs, because the reliable third ack
will ensure that SYN/ACK+MP_JOINs reach us.
We did this, because otherwise we cannot use TCP-keepalive in MPTCP, as
the same timer is used for multiple purposes.

However, by doing this, when a request-socket is created it will never
ever be removed from the request-socket queue if the 3-way handshake
never completes. We need to handle this correctly.

Fixes: ba1582e13 (mptcp: Correct support of TCP-Keepalive)
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>