Merge branch 'sctp_csum'

Vlad Yasevich says:

====================
sctp: Use software checksum under certain circumstances.

There are some cards that support SCTP checksum offloading.  When using
these cards with IPSec or forcing IP fragmentation of SCTP traffic,
the checksum is computed incorrectly due to the fact that xfrm and IP/IPv6
fragmentation code do not know that this is SCTP traffic and do not
know that checksum has to be computed differently.

To fix this, we let SCTP detect these conditions and perform software
checksum calculation.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>