[libvirt] [PATCH] add a nodnsmasq option for networks

[Serge Hallyn]

Some people want to define a libvirt network but have dns served
by another daemon.  Libvirt used to support that, but hasn't for
several years.  Two long-open bugs on this are

https://bugzilla.redhat.com/show_bug.cgi?id=636115
https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/584862

I'm not certain whether we really want to support this, as another
option is to simply create the bridge with external tools and tell
libvirt vms to use that bridge.  However, if we do want to support
it, this patch provides that support.

This patch allows an admin to set <nodnsmasq>true</nodnsmasq> in a
bridge definition to avoid having libvirt start a dnsmasq.

Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
---
 src/conf/network_conf.c     | 15 +++++++++++++++
 src/conf/network_conf.h     |  1 +
 src/network/bridge_driver.c |  2 +-
 3 files changed, 17 insertions(+), 1 deletion(-)

Index: libvirt-1.2.16/src/conf/network_conf.c
===================================================================
--- libvirt-1.2.16.orig/src/conf/network_conf.c
+++ libvirt-1.2.16/src/conf/network_conf.c
@@ -1985,6 +1985,7 @@ virNetworkDefParseXML(xmlXPathContextPtr
     xmlNodePtr virtPortNode = NULL;
     xmlNodePtr forwardNode = NULL;
     char *ipv6nogwStr = NULL;
+    char *noDnsmasqStr = NULL;
     char *trustGuestRxFilters = NULL;
     xmlNodePtr save = ctxt->node;
     xmlNodePtr bandwidthNode = NULL;
@@ -2018,6 +2019,20 @@ virNetworkDefParseXML(xmlXPathContextPtr
         def->uuid_specified = true;
     }
 
+    /* check if user requested no dnsmasq */
+    noDnsmasqStr = virXPathString("string(./nodnsmasq[1])", ctxt);
+    if (noDnsmasqStr) {
+        if (STREQ(noDnsmasqStr, "yes") || STREQ(noDnsmasqStr, "true")) {
+            def->nodnsmasq = true;
+        } else if (STRNEQ(noDnsmasqStr, "no") && STRNEQ(noDnsmasqStr, "false")) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("Invalid nodnsmasq setting '%s' in network '%s'"),
+                           noDnsmasqStr, def->name);
+            goto error;
+        }
+        VIR_FREE(noDnsmasqStr);
+    }
+
     /* check if definitions with no IPv6 gateway addresses is to
      * allow guest-to-guest communications.
      */
@@ -2660,6 +2675,9 @@ virNetworkDefFormatBuf(virBufferPtr buf,
     virUUIDFormat(uuid, uuidstr);
     virBufferAsprintf(buf, "<uuid>%s</uuid>\n", uuidstr);
 
+    if (def->nodnsmasq)
+	    virBufferAsprintf(buf, "<nodnsmasq>true</nodnsmasq>\n");
+
     if (def->forward.type != VIR_NETWORK_FORWARD_NONE) {
         const char *dev = NULL;
         if (!def->forward.npfs)
Index: libvirt-1.2.16/src/conf/network_conf.h
===================================================================
--- libvirt-1.2.16.orig/src/conf/network_conf.h
+++ libvirt-1.2.16/src/conf/network_conf.h
@@ -231,6 +231,7 @@ struct _virNetworkDef {
     bool stp; /* Spanning tree protocol */
     virMacAddr mac; /* mac address of bridge device */
     bool mac_specified;
+    bool nodnsmasq;
 
     /* specified if ip6tables rules added
      * when no ipv6 gateway addresses specified.
Index: libvirt-1.2.16/src/network/bridge_driver.c
===================================================================
--- libvirt-1.2.16.orig/src/network/bridge_driver.c
+++ libvirt-1.2.16/src/network/bridge_driver.c
@@ -2146,7 +2146,7 @@ networkStartNetworkVirtual(virNetworkDri
 
 
     /* start dnsmasq if there are any IP addresses (v4 or v6) */
-    if ((v4present || v6present) &&
+    if ((v4present || v6present) && !network->def->nodnsmasq &&
         networkStartDhcpDaemon(driver, network) < 0)
         goto err3;