sctp: add SCTP_AUTH_FREE_KEY type for AUTHENTICATION_EVENT

This patch is to add SCTP_AUTH_FREE_KEY type for AUTHENTICATION_EVENT,
as described in section 6.1.8 of RFC6458.

      SCTP_AUTH_FREE_KEY:  This report indicates that the SCTP
         implementation will no longer use the key identifier specified
         in auth_keynumber.

After deactivating a key, it would never be used again, which means
it's refcnt can't be held/increased by new chunks. But there may be
some chunks in out queue still using it. So only when refcnt is 1,
which means no chunk in outqueue is using/holding this key either,
this EVENT would be sent.

When users receive this notification, they could do DEL_KEY sockopt to
remove this shkey, and also tell the peer that this key won't be used
in any chunk thoroughly from now on, then the peer can remove it as
well safely.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 0 deletions

diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index a073123fc485..e64630cd3331 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -992,6 +992,20 @@ int sctp_auth_deact_key_id(struct sctp_endpoint *ep,
 	if (!found)
 		return -EINVAL;
 
+	/* refcnt == 1 and !list_empty mean it's not being used anywhere
+	 * and deactivated will be set, so it's time to notify userland
+	 * that this shkey can be freed.
+	 */
+	if (asoc && !list_empty(&key->key_list) &&
+	    refcount_read(&key->refcnt) == 1) {
+		struct sctp_ulpevent *ev;
+
+		ev = sctp_ulpevent_make_authkey(asoc, key->key_id,
+						SCTP_AUTH_FREE_KEY, GFP_KERNEL);
+		if (ev)
+			asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
+	}
+
 	key->deactivated = 1;
 
 	return 0;