For the QEMU / KVM driver, if the user doesn't specify an explicit name for
the TAP device associated with a virtual NIC, we auto-generate one with a
name vnetXXX. You can see this if you dump XML for a running QEMU guest.
Unfortunately if you dump XML, make a change and then feed it back in with
the define XML API, you have now persisted this auto-generated VIF name.
Do this for several domains at varying times and you'll eventually get
2 domains which have persisted the same auto-generated vnetXXX device
name. You can now not start both of these VMs at once.
The fix for this is simple - simply strip any TAP device name starting with
the string 'vnet' when defining a new VM. It will thus get assigned a new
automatically generate name which doesn't clash. The patch also strips out
hardcoded vnetXXX names when starting a VM to proactively deal with any
existing VMs whose config has been broken in this way.
Dan.
--
|=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=|
|=- Perl modules: http://search.cpan.org/~danberr/ -=|
|=- Projects: http://freshmeat.net/~danielpb/ -=|
|=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|
Index: src/qemu_conf.c
===================================================================
RCS file: /data/cvs/libvirt/src/qemu_conf.c,v
retrieving revision 1.21
diff -u -p -r1.21 qemu_conf.c
--- src/qemu_conf.c 3 Dec 2007 14:30:47 -0000 1.21
+++ src/qemu_conf.c 4 Dec 2007 16:56:42 -0000
@@ -657,6 +657,11 @@ static int qemudParseInterfaceXML(virCon
(net->type == QEMUD_NET_BRIDGE)) &&
xmlStrEqual(cur->name, BAD_CAST "target")) {
ifname = xmlGetProp(cur, BAD_CAST "dev");
+ if (STREQLEN("vnet", (const char*)ifname, 4)) {
+ /* An auto-generated target name, blank it out */
+ xmlFree(ifname);
+ ifname = NULL;
+ }
} else if ((script == NULL) &&
(net->type == QEMUD_NET_ETHERNET) &&
xmlStrEqual(cur->name, BAD_CAST "script")) {
@@ -1411,6 +1416,7 @@ qemudNetworkIfaceConnect(virConnectPtr c
}
brname = network->bridge;
if (net->dst.network.ifname[0] == '\0' ||
+ STREQLEN(net->dst.network.ifname, "vnet", 4) ||
strchr(net->dst.network.ifname, '%')) {
strcpy(net->dst.network.ifname, "vnet%d");
}
@@ -1418,6 +1424,7 @@ qemudNetworkIfaceConnect(virConnectPtr c
} else if (net->type == QEMUD_NET_BRIDGE) {
brname = net->dst.bridge.brname;
if (net->dst.bridge.ifname[0] == '\0' ||
+ STREQLEN(net->dst.bridge.ifname, "vnet", 4) ||
strchr(net->dst.bridge.ifname, '%')) {
strcpy(net->dst.bridge.ifname, "vnet%d");
}
--
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