Improved Debug

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Fix: Support receiving DSS without CSUM - even if it has been negotiated.

RFC 6824, Section 3.3:
If a checksum is not present when its use has been negotiated, the
receiver MUST close the subflow with a RST as it is considered broken.

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Update version-info

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Fix: Don't fallback if subflow-only fin is acked

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Fix: Correctly check for SYN-flag in mptcp_data_ack

The tcp_flags are not set for incoming packets. We thus cannot check
there for a SYN-packet. We have to check the tcp-header.

Similar fix in mptcp_skb_split_tail. The fin-flag is handled some lines
higher within this function.

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Fix: Initialize last_rbuf_opti correctly

It must be set to the correct timestamp as we create the mptcp_tcp_sock.

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Update window on all subflows for fast recovery

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Random Cleanup

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