[Qemu-devel] [PATCH] Allow default network type to be determined from an environmental variable

[Anthony Liguori]

One typically wants to use the same networking type on a given system.  
For instance, if you have a bridge set up for taps, you'll generally 
pass -net tap to the guest.  If you're an unprivileged user, you'll 
typically use -net user.

In the absence of a global configuration file, a reasonably sane way to 
support this configuration system wide is to use an environmental 
variable.  QEMU already uses a number of global variables for 
configuring audio options.

This patch introduces a global variable (QEMU_NET_DEFAULT) which allows 
a user to set a system-wide default networking type.  This saves a lot 
of typing for me as I no longer have to specify -net tap every time I 
launch QEMU.

Regards,

Anthony Liguori

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;
     }