[SCTP]: Implement sac_info field in SCTP_ASSOC_CHANGE notification.

As stated in the sctp socket api draft:

   sac_info: variable

   If the sac_state is SCTP_COMM_LOST and an ABORT chunk was received
   for this association, sac_info[] contains the complete ABORT chunk as
   defined in the SCTP specification RFC2960 [RFC2960] section 3.3.7.

We now save received ABORT chunks into the sac_info field and pass that
to the user.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sctp/user.h b/include/net/sctp/user.h
index 80b7afe..1b3153c 100644
--- a/include/net/sctp/user.h
+++ b/include/net/sctp/user.h
@@ -217,6 +217,7 @@
 	__u16 sac_outbound_streams;
 	__u16 sac_inbound_streams;
 	sctp_assoc_t sac_assoc_id;
+	__u8 sac_info[0];
 };
 
 /*