[infiniband] Handle duplicate Communication Management REPs

We will terminate our transaction as soon as we receive the first CM
REP, since that provides all the state that we need.  However, the
peer may resend the REP if it didn't see our RTU, and if we don't
respond with another RTU we risk being disconnected.  (This protocol
appears not to handle retries gracefully.)

Fix by adding a management agent that will listen for these duplicate
REPs and send back an RTU.

src/include/gpxe/ib_cm.h

@@ -46,6 +46,9 @@ struct ib_connection {
 	/** Connection operations */
 	struct ib_connection_operations *op;
 
+	/** List of connections */
+	struct list_head list;
+
 	/** Path to target */
 	struct ib_path *path;
 	/** Connection request management transaction */

src/net/infiniband/ib_cm.c

@@ -36,6 +36,9 @@ FILE_LICENCE ( GPL2_OR_LATER );
  *
  */
 
+/** List of connections */
+static LIST_HEAD ( ib_cm_conns );
+
 /**
  * Send "ready to use" response
  *
@@ -71,6 +74,54 @@ static int ib_cm_send_rtu ( struct ib_device *ibdev,
 	return 0;
 }
 
+/**
+ * Handle duplicate connection replies
+ *
+ * @v ibdev		Infiniband device
+ * @v mi		Management interface
+ * @v mad		Received MAD
+ * @v av		Source address vector
+ * @ret rc		Return status code
+ *
+ * If a "ready to use" MAD is lost, the peer may resend the connection
+ * reply.  We have to respond to these with duplicate "ready to use"
+ * MADs, otherwise the peer may time out and drop the connection.
+ */
+static void ib_cm_connect_rep ( struct ib_device *ibdev,
+				struct ib_mad_interface *mi,
+				union ib_mad *mad,
+				struct ib_address_vector *av ) {
+	struct ib_cm_connect_reply *connect_rep =
+		&mad->cm.cm_data.connect_reply;
+	struct ib_connection *conn;
+	int rc;
+
+	/* Identify connection */
+	list_for_each_entry ( conn, &ib_cm_conns, list ) {
+		if ( ntohl ( connect_rep->remote_id ) != conn->local_id )
+			continue;
+		/* Try to send "ready to use" reply */
+		if ( ( rc = ib_cm_send_rtu ( ibdev, mi, conn, av ) ) != 0 ) {
+			/* Ignore errors */
+			return;
+		}
+		return;
+	}
+
+	DBG ( "CM unidentified connection %08x\n",
+	      ntohl ( connect_rep->remote_id ) );
+}
+
+/** Communication management agents */
+struct ib_mad_agent ib_cm_agent[] __ib_mad_agent = {
+	{
+		.mgmt_class = IB_MGMT_CLASS_CM,
+		.class_version = IB_CM_CLASS_VERSION,
+		.attr_id = htons ( IB_CM_ATTR_CONNECT_REPLY ),
+		.handle = ib_cm_connect_rep,
+	},
+};
+
 /**
  * Handle connection request transaction completion
  *
@@ -296,6 +347,9 @@ ib_create_conn ( struct ib_device *ibdev, struct ib_queue_pair *qp,
 		goto err_create_path;
 	ib_path_set_ownerdata ( conn->path, conn );
 
+	/* Add to list of connections */
+	list_add ( &conn->list, &ib_cm_conns );
+
 	DBGC ( conn, "CM %p created for IBDEV %p QPN %lx\n",
 	       conn, ibdev, qp->qpn );
 	DBGC ( conn, "CM %p connecting to %08x:%08x:%08x:%08x %08x:%08x\n",
@@ -324,6 +378,7 @@ void ib_destroy_conn ( struct ib_device *ibdev,
 		       struct ib_queue_pair *qp __unused,
 		       struct ib_connection *conn ) {
 
+	list_del ( &conn->list );
 	if ( conn->madx )
 		ib_destroy_madx ( ibdev, ibdev->gsi, conn->madx );
 	if ( conn->path )