sctp: introduce SCTP_FUTURE/CURRENT/ALL_ASSOC

This patch is to add 3 constants SCTP_FUTURE_ASSOC,
SCTP_CURRENT_ASSOC and SCTP_ALL_ASSOC for reserved
assoc_ids, as defined in rfc6458#section-7.2.

And add the process for them when doing lookup and
inserting in sctp_id2assoc and sctp_assoc_set_id.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 10 insertions, 3 deletions

diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
index d584073532b8..b8f2c4d56532 100644
--- a/include/uapi/linux/sctp.h
+++ b/include/uapi/linux/sctp.h
@@ -59,6 +59,10 @@
 
 typedef __s32 sctp_assoc_t;
 
+#define SCTP_FUTURE_ASSOC       0
+#define SCTP_CURRENT_ASSOC      1
+#define SCTP_ALL_ASSOC          2
+
 /* The following symbols come from the Sockets API Extensions for
  * SCTP <draft-ietf-tsvwg-sctpsocket-07.txt>.
  */
diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index 201c888604e4..b99f163e33ac 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -1651,8 +1651,11 @@ int sctp_assoc_set_id(struct sctp_association *asoc, gfp_t gfp)
         if (preload)
                 idr_preload(gfp);
         spin_lock_bh(&sctp_assocs_id_lock);
-        /* 0 is not a valid assoc_id, must be >= 1 */
-        ret = idr_alloc_cyclic(&sctp_assocs_id, asoc, 1, 0, GFP_NOWAIT);
+        /* 0, 1, 2 are used as SCTP_FUTURE_ASSOC, SCTP_CURRENT_ASSOC and
+         * SCTP_ALL_ASSOC, so an available id must be > SCTP_ALL_ASSOC.
+         */
+        ret = idr_alloc_cyclic(&sctp_assocs_id, asoc, SCTP_ALL_ASSOC + 1, 0,
+                               GFP_NOWAIT);
         spin_unlock_bh(&sctp_assocs_id_lock);
         if (preload)
                 idr_preload_end();
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index f93c3cf9e567..a52d132470ea 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -248,7 +248,7 @@ struct sctp_association *sctp_id2assoc(struct sock *sk, sctp_assoc_t id)
         }
 
         /* Otherwise this is a UDP-style socket. */
-        if (!id || (id == (sctp_assoc_t)-1))
+        if (id <= SCTP_ALL_ASSOC)
                 return NULL;
 
         spin_lock_bh(&sctp_assocs_id_lock);