[PATCH v2] network: add an option to make dns public

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In some use cases we don't want the virtual network's DNS to only
listen to the vnet interface. Adding a publiclyAccessible attribute
to the dns element in the configuration allows the DNS to listen to
all interfaces.

It simply disables the bind-dynamic option of dnsmasq for the network.
---

 This patch is v2 for this one:
 https://www.redhat.com/archives/libvir-list/2015-June/msg00018.html

 Diff to v1:
   * Use bind-interface if public DNS is requested
   * Add more tests
   * Write out the public value in the format function
   * Fixed the rng
   * Renamed the attribute to public: shouldn't mislead users

 I tested this patch with several configurations of running networks.
 The only thing I noted though is that the user may need to adapt the system
 dnsmasq to avoid address:port conflicts... but hey, when one uses such a
 hacky feature of the libvirt network, he needs to take care of the rest ;)

 docs/formatnetwork.html.in                         |  9 +++++++
 docs/schemas/network.rng                           |  5 ++++
 src/conf/network_conf.c                            | 28 ++++++++++++++++++++--
 src/conf/network_conf.h                            |  1 +
 src/network/bridge_driver.c                        |  3 ++-
 .../nat-network-dns-not-public.conf                | 15 ++++++++++++
 .../nat-network-dns-not-public.xml                 | 15 ++++++++++++
 .../nat-network-dns-public.conf                    | 15 ++++++++++++
 .../networkxml2confdata/nat-network-dns-public.xml | 15 ++++++++++++
 tests/networkxml2xmlin/nat-network-dns-public.xml  |  9 +++++++
 tests/networkxml2xmlout/nat-network-dns-public.xml | 11 +++++++++
 tests/networkxml2xmltest.c                         |  1 +
 12 files changed, 124 insertions(+), 3 deletions(-)
 create mode 100644 tests/networkxml2confdata/nat-network-dns-not-public.conf
 create mode 100644 tests/networkxml2confdata/nat-network-dns-not-public.xml
 create mode 100644 tests/networkxml2confdata/nat-network-dns-public.conf
 create mode 100644 tests/networkxml2confdata/nat-network-dns-public.xml
 create mode 100644 tests/networkxml2xmlin/nat-network-dns-public.xml
 create mode 100644 tests/networkxml2xmlout/nat-network-dns-public.xml

diff --git a/docs/formatnetwork.html.in b/docs/formatnetwork.html.in
index 6abed8f..0141d93 100644
--- a/docs/formatnetwork.html.in
+++ b/docs/formatnetwork.html.in
@@ -851,6 +851,15 @@
           DNS server.
         </p>
 
+        <p>
+          The dns element
+          can have an optional <code>public</code> attribute
+          <span class="since">Since 1.2.17</span>. If <code>public</code>
+          is "yes", then the DNS server will handle requests for all interfaces.
+          If <code>public</code> is not set or "no", the DNS server will
+          only handle requests for the interface of the virtual network.
+        </p>
+
         Currently supported sub-elements of <code>&lt;dns&gt;</code> are:
         <dl>
           <dt><code>forwarder</code></dt>
diff --git a/docs/schemas/network.rng b/docs/schemas/network.rng
index 4edb6eb..f70e3dc 100644
--- a/docs/schemas/network.rng
+++ b/docs/schemas/network.rng
@@ -249,6 +249,11 @@
                 <ref name="virYesNo"/>
               </attribute>
             </optional>
+            <optional>
+              <attribute name="public">
+                <ref name="virYesNo"/>
+              </attribute>
+            </optional>
             <interleave>
               <zeroOrMore>
                 <element name="forwarder">
diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index 72006e9..e90c004 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -1332,9 +1332,14 @@ virNetworkDNSDefParseXML(const char *networkName,
     size_t i;
     int ret = -1;
     xmlNodePtr save = ctxt->node;
+    char *public = NULL;
 
     ctxt->node = node;
 
+    public = virXPathString("string(./@public)", ctxt);
+    if (public)
+        def->public = virTristateBoolTypeFromString(public);
+
     forwardPlainNames = virXPathString("string(./@forwardPlainNames)", ctxt);
     if (forwardPlainNames) {
         def->forwardPlainNames = virTristateBoolTypeFromString(forwardPlainNames);
@@ -1433,6 +1438,7 @@ virNetworkDNSDefParseXML(const char *networkName,
 
     ret = 0;
  cleanup:
+    VIR_FREE(public);
     VIR_FREE(forwardPlainNames);
     VIR_FREE(fwdNodes);
     VIR_FREE(hostNodes);
@@ -2416,7 +2422,7 @@ virNetworkDNSDefFormat(virBufferPtr buf,
     size_t i, j;
 
     if (!(def->forwardPlainNames || def->nfwds || def->nhosts ||
-          def->nsrvs || def->ntxts))
+          def->nsrvs || def->ntxts || def->public))
         return 0;
 
     virBufferAddLit(buf, "<dns");
@@ -2431,7 +2437,25 @@ virNetworkDNSDefFormat(virBufferPtr buf,
             return -1;
         }
         virBufferAsprintf(buf, " forwardPlainNames='%s'", fwd);
-        if (!(def->nfwds || def->nhosts || def->nsrvs || def->ntxts)) {
+        if (!(def->nfwds || def->nhosts || def->nsrvs || def->ntxts ||
+              def->public)) {
+            virBufferAddLit(buf, "/>\n");
+            return 0;
+        }
+    }
+
+    if (def->public) {
+        const char *public = virTristateBoolTypeToString(def->public);
+
+        if (!public) {
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("Unknown public type %d in network"),
+                           def->public);
+            return -1;
+        }
+        virBufferAsprintf(buf, " public='%s'", public);
+        if (!(def->nfwds || def->nhosts || def->nsrvs || def->ntxts ||
+              def->forwardPlainNames)) {
             virBufferAddLit(buf, "/>\n");
             return 0;
         }
diff --git a/src/conf/network_conf.h b/src/conf/network_conf.h
index 1cd5100..ae239b8 100644
--- a/src/conf/network_conf.h
+++ b/src/conf/network_conf.h
@@ -136,6 +136,7 @@ struct _virNetworkDNSDef {
     virNetworkDNSSrvDefPtr srvs;
     size_t nfwds;
     char **forwarders;
+    int public; /* enum virTristateBool */
 };
 
 typedef struct _virNetworkIpDef virNetworkIpDef;
diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index 3d6721b..8b11b51 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -991,7 +991,8 @@ networkDnsmasqConfContents(virNetworkObjPtr network,
     /* dnsmasq will *always* listen on localhost unless told otherwise */
     virBufferAddLit(&configbuf, "except-interface=lo\n");
 
-    if (dnsmasqCapsGet(caps, DNSMASQ_CAPS_BIND_DYNAMIC)) {
+    if (dnsmasqCapsGet(caps, DNSMASQ_CAPS_BIND_DYNAMIC) &&
+        network->def->dns.public != VIR_TRISTATE_BOOL_YES) {
         /* using --bind-dynamic with only --interface (no
          * --listen-address) prevents dnsmasq from responding to dns
          * queries that arrive on some interface other than our bridge
diff --git a/tests/networkxml2confdata/nat-network-dns-not-public.conf b/tests/networkxml2confdata/nat-network-dns-not-public.conf
new file mode 100644
index 0000000..021316f
--- /dev/null
+++ b/tests/networkxml2confdata/nat-network-dns-not-public.conf
@@ -0,0 +1,15 @@
+##WARNING:  THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
+##OVERWRITTEN AND LOST.  Changes to this configuration should be made using:
+##    virsh net-edit default
+## or other application using the libvirt API.
+##
+## dnsmasq conf file created by libvirt
+strict-order
+domain=example.com
+expand-hosts
+domain-needed
+local=//
+except-interface=lo
+bind-dynamic
+interface=virbr0
+addn-hosts=/var/lib/libvirt/dnsmasq/default.addnhosts
diff --git a/tests/networkxml2confdata/nat-network-dns-not-public.xml b/tests/networkxml2confdata/nat-network-dns-not-public.xml
new file mode 100644
index 0000000..cc78f34
--- /dev/null
+++ b/tests/networkxml2confdata/nat-network-dns-not-public.xml
@@ -0,0 +1,15 @@
+<network>
+  <name>default</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a9c</uuid>
+  <forward dev='eth0' mode='nat'/>
+  <bridge name='virbr0' stp='on' delay='0'/>
+  <domain name="example.com"/>
+  <dns forwardPlainNames='no' public='no'>
+    <host ip='192.168.122.1'>
+      <hostname>host</hostname>
+      <hostname>gateway</hostname>
+    </host>
+  </dns>
+  <ip address='192.168.122.1' netmask='255.255.255.0'>
+  </ip>
+</network>
diff --git a/tests/networkxml2confdata/nat-network-dns-public.conf b/tests/networkxml2confdata/nat-network-dns-public.conf
new file mode 100644
index 0000000..05cbf43
--- /dev/null
+++ b/tests/networkxml2confdata/nat-network-dns-public.conf
@@ -0,0 +1,15 @@
+##WARNING:  THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
+##OVERWRITTEN AND LOST.  Changes to this configuration should be made using:
+##    virsh net-edit default
+## or other application using the libvirt API.
+##
+## dnsmasq conf file created by libvirt
+strict-order
+domain=example.com
+expand-hosts
+domain-needed
+local=//
+except-interface=lo
+bind-interfaces
+interface=virbr0
+addn-hosts=/var/lib/libvirt/dnsmasq/default.addnhosts
diff --git a/tests/networkxml2confdata/nat-network-dns-public.xml b/tests/networkxml2confdata/nat-network-dns-public.xml
new file mode 100644
index 0000000..9c59c7b
--- /dev/null
+++ b/tests/networkxml2confdata/nat-network-dns-public.xml
@@ -0,0 +1,15 @@
+<network>
+  <name>default</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a9c</uuid>
+  <forward dev='eth0' mode='nat'/>
+  <bridge name='virbr0' stp='on' delay='0'/>
+  <domain name="example.com"/>
+  <dns forwardPlainNames='no' public='yes'>
+    <host ip='192.168.122.1'>
+      <hostname>host</hostname>
+      <hostname>gateway</hostname>
+    </host>
+  </dns>
+  <ip address='192.168.122.1' netmask='255.255.255.0'>
+  </ip>
+</network>
diff --git a/tests/networkxml2xmlin/nat-network-dns-public.xml b/tests/networkxml2xmlin/nat-network-dns-public.xml
new file mode 100644
index 0000000..0765a83
--- /dev/null
+++ b/tests/networkxml2xmlin/nat-network-dns-public.xml
@@ -0,0 +1,9 @@
+<network>
+  <name>default</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a9c</uuid>
+  <forward dev='eth0' mode='nat'/>
+  <bridge name='virbr0' stp='on' delay='0' />
+  <dns public='yes'/>
+  <ip address='192.168.122.1' netmask='255.255.255.0'>
+  </ip>
+</network>
diff --git a/tests/networkxml2xmlout/nat-network-dns-public.xml b/tests/networkxml2xmlout/nat-network-dns-public.xml
new file mode 100644
index 0000000..66caacd
--- /dev/null
+++ b/tests/networkxml2xmlout/nat-network-dns-public.xml
@@ -0,0 +1,11 @@
+<network>
+  <name>default</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a9c</uuid>
+  <forward dev='eth0' mode='nat'>
+    <interface dev='eth0'/>
+  </forward>
+  <bridge name='virbr0' stp='on' delay='0'/>
+  <dns public='yes'/>
+  <ip address='192.168.122.1' netmask='255.255.255.0'>
+  </ip>
+</network>
diff --git a/tests/networkxml2xmltest.c b/tests/networkxml2xmltest.c
index 290336e..ba565bc 100644
--- a/tests/networkxml2xmltest.c
+++ b/tests/networkxml2xmltest.c
@@ -97,6 +97,7 @@ mymain(void)
     DO_TEST("nat-network-dns-srv-record-minimal");
     DO_TEST("nat-network-dns-hosts");
     DO_TEST("nat-network-dns-forward-plain");
+    DO_TEST("nat-network-dns-public");
     DO_TEST("nat-network-dns-forwarders");
     DO_TEST("nat-network-forward-nat-address");
     DO_TEST("8021Qbh-net");
-- 
2.1.4

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