events: support server-side flag

This flag is being added in the kernel [1].

It is going to replace the server-side attribute. Check both to be
future proof.

Link: https://lore.kernel.org/20250909-mptcp-pm-user-server-side-flag-v1-0-cb8e2b8d1c0c@kernel.org [1]
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

Author: matttbe

include/linux/mptcp_upstream.h

@@ -32,6 +32,7 @@
 #define MPTCP_INFO_FLAG_REMOTE_KEY_RECEIVED	_BITUL(1)
 
 #define MPTCP_PM_EV_FLAG_DENY_JOIN_ID0		_BITUL(0)
+#define MPTCP_PM_EV_FLAG_SERVER_SIDE		_BITUL(1)
 
 #define MPTCP_PM_ADDR_FLAG_SIGNAL                      (1 << 0)
 #define MPTCP_PM_ADDR_FLAG_SUBFLOW                     (1 << 1)

include/linux/mptcp_upstream_pm.h

@@ -16,10 +16,10 @@
  *   good time to allocate memory and send ADD_ADDR if needed. Depending on the
  *   traffic-patterns it can take a long time until the MPTCP_EVENT_ESTABLISHED
  *   is sent. Attributes: token, family, saddr4 | saddr6, daddr4 | daddr6,
- *   sport, dport, server-side, [flags].
+ *   sport, dport, [server-side], [flags].
  * @MPTCP_EVENT_ESTABLISHED: A MPTCP connection is established (can start new
  *   subflows). Attributes: token, family, saddr4 | saddr6, daddr4 | daddr6,
- *   sport, dport, server-side, [flags].
+ *   sport, dport, [server-side], [flags].
  * @MPTCP_EVENT_CLOSED: A MPTCP connection has stopped. Attribute: token.
  * @MPTCP_EVENT_ANNOUNCED: A new address has been announced by the peer.
  *   Attributes: token, rem_id, family, daddr4 | daddr6 [, dport].

src/path_manager.c

@@ -258,7 +258,9 @@ static void handle_connection_created(struct pm_event_attrs const *attrs,
 
         static char const *const pm_name = NULL;
         bool const server_side =
-                (attrs->server_side != NULL ? *attrs->server_side : false);
+                (attrs->flags != NULL &&
+                 *attrs->flags & MPTCP_PM_EV_FLAG_SERVER_SIDE) ||
+                (attrs->server_side != NULL && *attrs->server_side);
         bool const deny_join_id0 =
                 attrs->flags != NULL &&
                 *attrs->flags & MPTCP_PM_EV_FLAG_DENY_JOIN_ID0;
@@ -314,7 +316,9 @@ static void handle_connection_established(struct pm_event_attrs const *attrs,
 
         // Assume server_side is false if event attribute is unavailable.
         bool const server_side =
-                (attrs->server_side != NULL ? *attrs->server_side : false);
+                (attrs->flags != NULL &&
+                 *attrs->flags & MPTCP_PM_EV_FLAG_SERVER_SIDE) ||
+                (attrs->server_side != NULL && *attrs->server_side);
         bool const deny_join_id0 =
                 attrs->flags != NULL &&
                 *attrs->flags & MPTCP_PM_EV_FLAG_DENY_JOIN_ID0;