+static int
+choose_port(struct dp_netdev *dp, const char *name)
+{
+ int port_no;
+
+ if (dp->class != &dpif_netdev_class) {
+ const char *p;
+ int start_no = 0;
+
+ /* If the port name begins with "br", start the number search at
+ * 100 to make writing tests easier. */
+ if (!strncmp(name, "br", 2)) {
+ start_no = 100;
+ }
+
+ /* If the port name contains a number, try to assign that port number.
+ * This can make writing unit tests easier because port numbers are
+ * predictable. */
+ for (p = name; *p != '\0'; p++) {
+ if (isdigit((unsigned char) *p)) {
+ port_no = start_no + strtol(p, NULL, 10);
+ if (port_no > 0 && port_no < MAX_PORTS
+ && !dp->ports[port_no]) {
+ return port_no;
+ }
+ break;
+ }
+ }
+ }
+
+ for (port_no = 1; port_no < MAX_PORTS; port_no++) {
+ if (!dp->ports[port_no]) {
+ return port_no;
+ }
+ }
+
+ return -1;
+}
+