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>

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

include/net/sctp/structs.h

@@ -1322,7 +1322,8 @@ struct sctp_endpoint {
 	/* SCTP-AUTH: endpoint shared keys */
 	struct list_head endpoint_shared_keys;
 	__u16 active_key_id;
-	__u8  auth_enable:1,
+	__u8  ecn_enable:1,
+	      auth_enable:1,
 	      intl_enable:1,
 	      prsctp_enable:1,
 	      asconf_enable:1,