Merge branch 'sctp-rfc7496-support'

Xin Long says:

====================
sctp: implement rfc7496 in sctp

This patchset implements "Additional Policies for the Partially Reliable
Stream Control Transmission Protocol Extension" described on RFC7496.

The Partially Reliable SCTP (PR-SCTP) extension defined in [RFC3758]
provides a generic method for senders to abandon user messages. The
decision to abandon a user message is sender side only, and the exact
condition is called a "PR-SCTP policy". This patchset implements 3
policies:

 1. Timed Reliability:  This allows the sender to specify a timeout for
    a user message after which the SCTP stack abandons the user message.

 2. Limited Retransmission Policy:  Allows limitation of the number of
    retransmissions.

 3. Priority Policy:  Allows removal of lower-priority messages if space
    for higher-priority messages is needed in the send buffer.

Patch 1-3 add some sockopts in sctp to set/get pr_sctp policy status.
Patch 4-6 implement these 3 policies one by one.
====================

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>