sctp: implement prsctp TTL policy

prsctp TTL policy is a policy to abandon chunks when they expire
at the specific time in local stack. It's similar with expires_at
in struct sctp_datamsg.

This patch uses sinfo->sinfo_timetolive to set the specific time for
TTL policy. sinfo->sinfo_timetolive is also used for msg->expires_at.
So if prsctp_enable or TTL policy is not enabled, msg->expires_at
still works as before.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index c3167c4..0861429 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -7099,7 +7099,7 @@
 
 			if (cmsgs->srinfo->sinfo_flags &
 			    ~(SCTP_UNORDERED | SCTP_ADDR_OVER |
-			      SCTP_SACK_IMMEDIATELY |
+			      SCTP_SACK_IMMEDIATELY | SCTP_PR_SCTP_MASK |
 			      SCTP_ABORT | SCTP_EOF))
 				return -EINVAL;
 			break;
@@ -7123,7 +7123,7 @@
 
 			if (cmsgs->sinfo->snd_flags &
 			    ~(SCTP_UNORDERED | SCTP_ADDR_OVER |
-			      SCTP_SACK_IMMEDIATELY |
+			      SCTP_SACK_IMMEDIATELY | SCTP_PR_SCTP_MASK |
 			      SCTP_ABORT | SCTP_EOF))
 				return -EINVAL;
 			break;