Re: [Qemu-devel] [PATCH] Use existing tun/tap network interface

[Thomas Schwinge <schwinge-qemu-devel@nic-nac-project.de>]

[-- Attachment #1: Type: text/plain, Size: 1356 bytes --]

On Sat, Nov 27, 2004 at 11:54:30AM +0100, Lars Munch wrote:
> The attached patch adds a new option '-tun-if' which will enable you to
> use preconfigured tun/tap network interfaces as described here:
> http://user-mode-linux.sourceforge.net/UserModeLinux-HOWTO-6.html#ss6.7

I've been preparing a patch to achieve the same functionality some days
ago, but didn't have the time to finish it, yet.
It is, however, working: 'qemu-net-if.patch' is attached.

Things to be done:
* Make it possible to use '-net-if ...' and '-tun-fd ...' at the same
  time without interfering with each other - albeit I don't know if
  anybody will use both of them at the same time, ever.
* Disable the invocation of a tap/tun network init script when
  specifying '-net-if ...' or '-tun-fd ...'

> To use it, first configure your interface by using for example tunctl
> from UML:
> 
> # tunctl -t qemu0 -u OWNER
> # ifconfig qemu0 xxx.xxx.xxx.xxx up
> 
> Now you will have a network interface called 'qemu0'.

Wrapping that in other words:
You configure the network interfaces to be used by qemu in your system's
network configuration script (or anywhere else) and can use that
interface later without starting qemu (or a wrapper script) as root.

> Then start qemu with something like this:
> 
> # qemu -tun-if qemu0 .....

I'm adding '-n /bin/true' here.


Regards,
 Thomas

[-- Attachment #2: qemu-net-if.patch --]
[-- Type: text/plain, Size: 2665 bytes --]

diff -Nru qemu-0.o/vl.c qemu-0/vl.c
--- qemu-0.o/vl.c	2004-11-16 14:16:22.000000000 +0100
+++ qemu-0/vl.c	2004-11-19 18:42:49.811154272 +0100
@@ -1596,7 +1596,7 @@
     }
     memset(&ifr, 0, sizeof(ifr));
     ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
-    pstrcpy(ifr.ifr_name, IFNAMSIZ, "tun%d");
+    pstrcpy(ifr.ifr_name, IFNAMSIZ, *ifname ? ifname : "tun%d");
     ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
     if (ret != 0) {
         fprintf(stderr, "warning: could not configure /dev/net/tun: no virtual network emulation\n");
@@ -2513,6 +2513,8 @@
            "-nics n         simulate 'n' network cards [default=1]\n"
            "-macaddr addr   set the mac address of the first interface\n"
            "-n script       set tap/tun network init script [default=%s]\n"
+           "-net-if interface\n"
+           "                set the network interface to use [default=tun%%d]\n"
            "-tun-fd fd      use this fd as already opened tap/tun interface\n"
 #ifdef CONFIG_SLIRP
            "-user-net       use user mode network stack [default if no tap/tun script]\n"
@@ -2596,6 +2598,7 @@
     QEMU_OPTION_nics,
     QEMU_OPTION_macaddr,
     QEMU_OPTION_n,
+    QEMU_OPTION_net_if,
     QEMU_OPTION_tun_fd,
     QEMU_OPTION_user_net,
     QEMU_OPTION_tftp,
@@ -2652,6 +2655,7 @@
     { "nics", HAS_ARG, QEMU_OPTION_nics},
     { "macaddr", HAS_ARG, QEMU_OPTION_macaddr},
     { "n", HAS_ARG, QEMU_OPTION_n },
+    { "net-if", HAS_ARG, QEMU_OPTION_net_if },
     { "tun-fd", HAS_ARG, QEMU_OPTION_tun_fd },
 #ifdef CONFIG_SLIRP
     { "user-net", 0, QEMU_OPTION_user_net },
@@ -2757,7 +2761,7 @@
     int cyls, heads, secs, translation;
     int start_emulation = 1;
     uint8_t macaddr[6];
-    int net_if_type, nb_tun_fds, tun_fds[MAX_NICS];
+    int net_if_type, nb_net_ifs, nb_tun_fds, tun_fds[MAX_NICS];
     int optind;
     const char *r, *optarg;
     CharDriverState *monitor_hd;
@@ -2798,6 +2802,7 @@
     serial_device_index = 0;
     
     nb_tun_fds = 0;
+    nb_net_ifs = 0;
     net_if_type = -1;
     nb_nics = 1;
     /* default mac address of the first network interface */
@@ -3026,6 +3031,13 @@
             case QEMU_OPTION_n:
                 pstrcpy(network_script, sizeof(network_script), optarg);
                 break;
+            case QEMU_OPTION_net_if:
+                net_if_type = NET_IF_TUN;
+                if (nb_net_ifs < MAX_NICS) {
+                    pstrcpy (nd_table[nb_net_ifs].ifname, sizeof(nd_table[nb_net_ifs].ifname), optarg);
+                    nb_net_ifs++;
+                }
+                break;
 #ifdef CONFIG_GDBSTUB
             case QEMU_OPTION_s:
                 use_gdbstub = 1;