Re: [Qemu-devel] tun/tap networking: patch for existing tun

[Jean-Christian de Rivaz <jc@eclis.ch>]

[-- Attachment #1: Type: text/plain, Size: 306 bytes --]

Attached is a patch proposition to allow opennig an existing tun 
(already configured by root).

This patch can work only on Linux as it make no change into the code for 
BSD.

Please make open comment about this to improve it or to let my know why 
this if not a good thing...
-- 
Jean-Christian de Rivaz

[-- Attachment #2: tun2.patch --]
[-- Type: text/x-patch, Size: 5680 bytes --]

Index: qemu-doc.texi
===================================================================
RCS file: /cvsroot/qemu/qemu/qemu-doc.texi,v
retrieving revision 1.65
diff -u -r1.65 qemu-doc.texi
--- qemu-doc.texi	28 Jul 2005 22:27:28 -0000	1.65
+++ qemu-doc.texi	1 Oct 2005 20:38:16 -0000
@@ -222,6 +222,22 @@
 aa:bb:cc:dd:ee:ff in hexa). The mac address is incremented for each
 new network interface.
 
+@item -tun devname
+Try to use @var{devname} while opening a tap/tun host network interface and use
+it. If it work, the network init script is not executed for this
+interface. If it don't work, the interface will use the name assigned
+by the operating system and the network init script is executed.
+
+This option permit the use of preconfigured interface. For example, as
+root you can assign a tun interface to a user and configure it like this:
+@example
+tunctl -u bob -t tun2
+ifconfig tun2 192.168.2.1
+@end example
+Then bob can use this interface with the option "-tun tun2". Note that
+option permit the use of a DHCP server on the host to configure the
+guest interface.
+
 @item -tun-fd fd
 Assumes @var{fd} talks to a tap/tun host network interface and use
 it. Read @url{http://bellard.org/qemu/tetrinet.html} to have an
Index: vl.c
===================================================================
RCS file: /cvsroot/qemu/qemu/vl.c,v
retrieving revision 1.136
diff -u -r1.136 vl.c
--- vl.c	3 Sep 2005 21:33:43 -0000	1.136
+++ vl.c	1 Oct 2005 20:38:17 -0000
@@ -1663,7 +1663,7 @@
     }
     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) ? 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");
@@ -1689,7 +1689,7 @@
     qemu_add_fd_read_handler(nd->fd, fd_can_read, fd_read, opaque);
 }
 
-static int net_tun_init(NetDriverState *nd)
+static int net_tun_init(NetDriverState *nd, int script)
 {
     int pid, status;
     char *args[3];
@@ -1700,7 +1700,7 @@
         return -1;
 
     /* try to launch network init script */
-    pid = fork();
+    pid = script ? fork() : -1;
     if (pid >= 0) {
         if (pid == 0) {
             parg = args;
@@ -2851,6 +2851,7 @@
            "-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"
+           "-tun devname    try to use devname while opening tap/tun interface\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"
@@ -2940,6 +2941,7 @@
     QEMU_OPTION_nics,
     QEMU_OPTION_macaddr,
     QEMU_OPTION_n,
+    QEMU_OPTION_tun,
     QEMU_OPTION_tun_fd,
     QEMU_OPTION_user_net,
     QEMU_OPTION_tftp,
@@ -3003,6 +3005,7 @@
     { "nics", HAS_ARG, QEMU_OPTION_nics},
     { "macaddr", HAS_ARG, QEMU_OPTION_macaddr},
     { "n", HAS_ARG, QEMU_OPTION_n },
+    { "tun", HAS_ARG, QEMU_OPTION_tun },
     { "tun-fd", HAS_ARG, QEMU_OPTION_tun_fd },
 #ifdef CONFIG_SLIRP
     { "user-net", 0, QEMU_OPTION_user_net },
@@ -3136,7 +3139,7 @@
     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_tun, nb_tun_fds, cnt_tun_fds, tun_fds[MAX_NICS];
     int optind;
     const char *r, *optarg;
     CharDriverState *monitor_hd;
@@ -3190,7 +3193,12 @@
         parallel_devices[i][0] = '\0';
     parallel_device_index = 0;
     
+    for(i = 0; i < MAX_NICS; i++) {
+	nd_table[i].ifname[0] = '\0';
+    }
+    nb_tun = 0;
     nb_tun_fds = 0;
+    cnt_tun_fds = 0;
     net_if_type = -1;
     nb_nics = 1;
     /* default mac address of the first network interface */
@@ -3313,18 +3321,25 @@
             case QEMU_OPTION_append:
                 kernel_cmdline = optarg;
                 break;
+	    case QEMU_OPTION_tun:
+		net_if_type = NET_IF_TUN;
+		if (nb_tun+nb_tun_fds < MAX_NICS) {
+		    pstrcpy(nd_table[nb_tun++].ifname, IFNAMSIZ, optarg);
+		}
+		break;
 	    case QEMU_OPTION_tun_fd:
                 {
                     const char *p;
                     int fd;
                     net_if_type = NET_IF_TUN;
-                    if (nb_tun_fds < MAX_NICS) {
+                    if (nb_tun+nb_tun_fds < MAX_NICS) {
                         fd = strtol(optarg, (char **)&p, 0);
                         if (*p != '\0') {
                             fprintf(stderr, "qemu: invalid fd for network interface %d\n", nb_tun_fds);
                             exit(1);
                         }
                         tun_fds[nb_tun_fds++] = fd;
+			nb_tun++;
                     }
                 }
 		break;
@@ -3603,12 +3618,20 @@
 #endif
 #if !defined(_WIN32)
         case NET_IF_TUN:
-            if (i < nb_tun_fds) {
-                net_fd_init(nd, tun_fds[i]);
-            } else {
-                if (net_tun_init(nd) < 0)
-                    net_dummy_init(nd);
-            }
+	    if (nd->ifname && *(nd->ifname)) {
+		if (net_tun_init(nd, 0) < 0) {
+		    nd->ifname[0] = '\0';
+		    if (net_tun_init(nd, 1) < 0)
+		      net_dummy_init(nd);
+		}
+	    } else {
+		if (cnt_tun_fds < nb_tun_fds) {
+		    net_fd_init(nd, tun_fds[cnt_tun_fds++]);
+		} else {
+		    if (net_tun_init(nd, 1) < 0)
+		      net_dummy_init(nd);
+		}
+	    }
             break;
 #endif
         case NET_IF_DUMMY: