Index: qemu/vl.c
===================================================================
--- qemu.orig/vl.c	2008-01-13 15:12:55.000000000 -0600
+++ qemu/vl.c	2008-01-13 15:15:02.000000000 -0600
@@ -8754,11 +8754,16 @@
 
     /* init network clients */
     if (nb_net_clients == 0) {
+	const char *net_type = getenv("QEMU_NET_DEFAULT");
+
+	if (net_type == NULL)
+	    net_type = "user";
+
         /* if no clients, we use a default config */
         pstrcpy(net_clients[0], sizeof(net_clients[0]),
                 "nic");
         pstrcpy(net_clients[1], sizeof(net_clients[0]),
-                "user");
+                net_type);
         nb_net_clients = 2;
     }