rds: rdma: add consumer reject

For legacy protocol version incompatibility with non linux RDS,
consumer reject reason being used to convey it to peer. But the
choice of reject reason value as '1' was really poor.

Anyway for interoperability reasons with shipping products,
it needs to be supported. For any future versions, properly
encoded reject reason should to be used.

Reviewed-by: Sowmini Varadhan <[e-mail]>
Signed-off-by: Santosh Shilimkar <[e-mail]>
[[e-mail]: Adapted original patch with ipv6 changes]
Signed-off-by: Zhu Yanjun <[e-mail]>

net/rds/ib_cm.c

···
 
 	/* Check whether the remote protocol version matches ours. */
 	version = rds_ib_protocol_compatible(event, isv6);
-	if (!version)
+	if (!version) {
+		err = RDS_RDMA_REJ_INCOMPAT;
 		goto out;
+	}
 
 	dp = event->param.conn.private_data;
 	if (isv6) {
···
 	if (conn)
 		mutex_unlock(&conn->c_cm_lock);
 	if (err)
-		rdma_reject(cm_id, NULL, 0);
+		rdma_reject(cm_id, &err, sizeof(int));
 	return destroy;
 }
 

net/rds/rdma_transport.c

···
 	struct rds_connection *conn = cm_id->context;
 	struct rds_transport *trans;
 	int ret = 0;
+	int *err;
+	u8 len;
 
 	rdsdebug("conn %p id %p handling event %u (%s)\n", conn, cm_id,
 		 event->event, rdma_event_msg(event->event));
···
 		break;
 
 	case RDMA_CM_EVENT_REJECTED:
+		if (!conn)
+			break;
+		err = (int *)rdma_consumer_reject_data(cm_id, event, &len);
+		if (!err || (err && ((*err) == RDS_RDMA_REJ_INCOMPAT))) {
+			pr_warn("RDS/RDMA: conn <%pI6c, %pI6c> rejected, dropping connection\n",
+				&conn->c_laddr, &conn->c_faddr);
+			conn->c_proposed_version = RDS_PROTOCOL_COMPAT_VERSION;
+			rds_conn_drop(conn);
+		}
 		rdsdebug("Connection rejected: %s\n",
 			 rdma_reject_msg(cm_id, event->status));
+		break;
 		/* FALLTHROUGH */
 	case RDMA_CM_EVENT_ADDR_ERROR:
 	case RDMA_CM_EVENT_ROUTE_ERROR:

net/rds/rdma_transport.h

···
 
 #define RDS_RDMA_RESOLVE_TIMEOUT_MS     5000
 
+/* Below reject reason is for legacy interoperability issue with non-linux
+ * RDS endpoints where older version incompatibility is conveyed via value 1.
+ * For future version(s), proper encoded reject reason should be be used.
+ */
+#define RDS_RDMA_REJ_INCOMPAT		1
+
 int rds_rdma_conn_connect(struct rds_connection *conn);
 int rds_rdma_cm_event_handler(struct rdma_cm_id *cm_id,
 			      struct rdma_cm_event *event);