network: Make virtual domains resolvable from the host

This patch adds a new attribute "register" to the <domain> element. If
set to "yes", the DNS server created for the virtual network is
registered with systemd-resolved as a name server for the associated
domain. The names known to the dnsmasq process serving DNS and DHCP
requests for the virtual network will then be resolvable from the host
by appending the domain name to them.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

diff --git a/docs/formatnetwork.rst b/docs/formatnetwork.rst
index 16e81246facdb1c3c8b8d2db120d1780d6dbcaa5..dcdaf1e5a559ae40724911ce4d5ee28f9e9fd601 100644 (file)
--- a/docs/formatnetwork.rst
+++ b/docs/formatnetwork.rst
@@ -88,7 +88,7 @@ to the physical LAN (if at all).
    ...
    <bridge name="virbr0" stp="on" delay="5" macTableManager="libvirt"/>
    <mtu size="9000"/>
-   <domain name="example.com" localOnly="no"/>
+   <domain name="example.com" localOnly="no" register="no"/>
    <forward mode="nat" dev="eth0"/>
    ...
 
@@ -162,6 +162,13 @@ to the physical LAN (if at all).
    DNS server. If ``localOnly`` is "no", and by default, unresolved requests
    **will** be forwarded. :since:`Since 1.2.12`
 
+   :since:`Since 10.1.0` the optional ``register`` attribute can be used to
+   request registering the DNS server for resolving this domain with the host's
+   DNS resolver. When set to "yes", the host resolver will forward all requests
+   for domain names from this domain to the DNS server created for this virtual
+   network. To avoid DNS loops ``localOnly`` has to be set to "yes" as well.
+   This feature requires ``systemd-resolved`` to be running on the host.
+
 ``forward``
    Inclusion of the ``forward`` element indicates that the virtual network is to
    be connected to the physical LAN. :since:`Since 0.3.0.` The ``mode``

diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index ef3415cd89271c32b919e33ed8a96d1aadc1eb8f..cc92ed0b038b962daf0c2b06fa77a9c5e70d77aa 100644 (file)
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -1582,6 +1582,19 @@ virNetworkDefParseXML(xmlXPathContextPtr ctxt,
                                &def->domainLocalOnly) < 0)
         return NULL;
 
+    if (virXMLPropTristateBool(domain_node, "register",
+                               VIR_XML_PROP_NONE,
+                               &def->domainRegister) < 0)
+        return NULL;
+
+    if (def->domainRegister == VIR_TRISTATE_BOOL_YES &&
+        def->domainLocalOnly != VIR_TRISTATE_BOOL_YES) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("attribute 'register=yes' in <domain> element requires 'localOnly=yes' in network %1$s"),
+                       def->name);
+        return NULL;
+    }
+
     if ((bandwidthNode = virXPathNode("./bandwidth", ctxt)) &&
         virNetDevBandwidthParse(&def->bandwidth, NULL, bandwidthNode, false) < 0)
         return NULL;
@@ -2405,6 +2418,11 @@ virNetworkDefFormatBuf(virBuffer *buf,
             virBufferAsprintf(buf, " localOnly='%s'", local);
         }
 
+        if (def->domainRegister) {
+            virBufferAsprintf(buf, " register='%s'",
+                              virTristateBoolTypeToString(def->domainRegister));
+        }
+
         virBufferAddLit(buf, "/>\n");
     }
 

diff --git a/src/conf/network_conf.h b/src/conf/network_conf.h
index 1d7fd3ab6a37a041a2f9bc609f5054368006c20f..c2a4198abc5314e5ceadf7ebc8b3a42f3fcadc88 100644 (file)
--- a/src/conf/network_conf.h
+++ b/src/conf/network_conf.h
@@ -245,6 +245,7 @@ struct _virNetworkDef {
     int  macTableManager; /* enum virNetworkBridgeMACTableManager */
     char *domain;
     virTristateBool domainLocalOnly; /* yes disables dns forwarding */
+    virTristateBool domainRegister;
     unsigned long delay;   /* Bridge forward delay (ms) */
     bool stp; /* Spanning tree protocol */
     unsigned int mtu; /* MTU for bridge, 0 means "default" i.e. unset in config */

diff --git a/src/conf/schemas/network.rng b/src/conf/schemas/network.rng
index e56e07d13059151a930e6b3dded78e1a05becada..b7c8551fad51321eeb782975540899bd12b2872d 100644 (file)
--- a/src/conf/schemas/network.rng
+++ b/src/conf/schemas/network.rng
@@ -258,6 +258,9 @@
             <optional>
               <attribute name="localOnly"><ref name="virYesNo"/></attribute>
             </optional>
+            <optional>
+              <attribute name="register"><ref name="virYesNo"/></attribute>
+            </optional>
           </element>
         </optional>
 

diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index 9921c7cd140babf98bdc427feafa1cf026bcba2c..d89700c6ee2e2be4953e21ce1e9acfd04c9153a4 100644 (file)
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -63,7 +63,7 @@
 #include "virjson.h"
 #include "virnetworkportdef.h"
 #include "virutil.h"
-
+#include "virsystemd.h"
 #include "netdev_bandwidth_conf.h"
 
 #define VIR_FROM_THIS VIR_FROM_NETWORK
@@ -1902,6 +1902,7 @@ networkStartNetworkVirtual(virNetworkDriverState *driver,
     bool dnsmasqStarted = false;
     bool devOnline = false;
     bool firewalRulesAdded = false;
+    virSocketAddr *dnsServer = NULL;
 
     /* Check to see if any network IP collides with an existing route */
     if (networkCheckRouteCollision(def) < 0)
@@ -1958,6 +1959,9 @@ networkStartNetworkVirtual(virNetworkDriverState *driver,
         if (VIR_SOCKET_ADDR_IS_FAMILY(&ipdef->address, AF_INET6))
             v6present = true;
 
+        if (!dnsServer)
+            dnsServer = &ipdef->address;
+
         /* Add the IP address/netmask to the bridge */
         if (networkAddAddrToBridge(obj, ipdef) < 0)
             goto error;
@@ -2011,6 +2015,32 @@ networkStartNetworkVirtual(virNetworkDriverState *driver,
             goto error;
 
         dnsmasqStarted = true;
+
+        if (def->domain && def->domainRegister && dnsServer) {
+            unsigned int link;
+            int rc;
+
+            if ((link = if_nametoindex(def->bridge)) == 0) {
+                virReportSystemError(ENODEV,
+                                     _("unable to get interface index for %1$s"),
+                                     def->bridge);
+                goto error;
+            }
+
+            rc = virSystemdResolvedRegisterNameServer(link, def->domain,
+                                                      dnsServer);
+            if (rc == -2) {
+                virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                               _("failed to register name server: systemd-resolved is not available"));
+                goto error;
+            }
+
+            if (rc < 0) {
+                virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                               _("failed to register name server"));
+                goto error;
+            }
+        }
     }
 
     if (virNetDevBandwidthSet(def->bridge, def->bandwidth, true, true) < 0)