sctp: make ecn flag per netns and endpoint

This patch is to add ecn flag for both netns_sctp and sctp_endpoint,
net->sctp.ecn_enable is set 1 by default, and ep->ecn_enable will
be initialized with net->sctp.ecn_enable.

asoc->peer.ecn_capable will be set during negotiation only when
ep->ecn_enable is set on both sides.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netns/sctp.h b/include/net/netns/sctp.h
index 0db7fb3..bdc0f27 100644
--- a/include/net/netns/sctp.h
+++ b/include/net/netns/sctp.h
@@ -128,6 +128,9 @@ struct netns_sctp {
 	/* Flag to indicate if stream interleave is enabled */
 	int intl_enable;
 
+	/* Flag to indicate if ecn is enabled */
+	int ecn_enable;
+
 	/*
 	 * Policy to control SCTP IPv4 address scoping
 	 * 0   - Disable IPv4 address scoping