Backport of trunk fix to 3.2
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commit d663e5f092504733e9b857a7fe9a319a8a5303f5
Author: Christoph Paasch <christoph.paasch@uclouvain.be>
Date:   Mon Feb 25 09:20:35 2013 +0100

    Cleanup tcp_v4_destroy_sock

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

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Backport of trunk fix to 3.2
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commit 050a9707db6d366be53c1d9d807e621ed8e8ba8c
Author: Christoph Paasch <christoph.paasch@uclouvain.be>
Date:   Thu Feb 28 17:33:59 2013 +0100

    Fix: Stall if SACK is disabled and an RTO happens

    RFC6582 specifies that TCP should not exit the loss-state unless
    something more than high_seq has been acknowledged. (high_seq is the
    snd_nxt when the RTO occured)
    However, as soon as an RTO occurs MPTCP will stop sending on this
    subflow. Thus, the snd_una can NEVER EVER go beyond high_seq. So, MPTCP
    will stall on this subflow.

    This commit fixes it by taking this here into consideration.

    Reported-by: David Zats <dzats2008@gmail.com>
    Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>

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