sctp: add encap_port for netns sock asoc and transport

encap_port is added as per netns/sock/assoc/transport, and the
latter one's encap_port inherits the former one's by default.
The transport's encap_port value would mostly decide if one
packet should go out with udp encapsulated or not.

This patch also allows users to set netns' encap_port by sysctl.

v1->v2:
  - Change to define encap_port as __be16 for sctp_sock, asoc and
    transport.
v2->v3:
  - No change.
v3->v4:
  - Add 'encap_port' entry in ip-sysctl.rst.
v4->v5:
  - Improve the description of encap_port in ip-sysctl.rst.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index fdb69d46276d..336df4b36655 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -99,6 +99,8 @@ static struct sctp_association *sctp_association_init(
 	 */
 	asoc->hbinterval = msecs_to_jiffies(sp->hbinterval);
 
+	asoc->encap_port = sp->encap_port;
+
 	/* Initialize path max retrans value. */
 	asoc->pathmaxrxt = sp->pathmaxrxt;
 
@@ -624,6 +626,8 @@ struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
 	 */
 	peer->hbinterval = asoc->hbinterval;
 
+	peer->encap_port = asoc->encap_port;
+
 	/* Set the path max_retrans.  */
 	peer->pathmaxrxt = asoc->pathmaxrxt;