link-state: conf: Add element to XML for controling link state

A new element is introduced to XML that allows to control
state of virtual network interfaces in hypervisors.

Live modification of the link state allows networking tools
propagate topology changes to guest OS or testing of
scenarios in complex (virtual) networks.

This patch adds elements to XML grammars and parsing and generating
code.

docs/formatdomain.html.in

@@ -2131,6 +2131,27 @@ qemu-kvm -net nic,model=? /dev/null
       <span class="since">Since 0.9.4</span>
     </p>
 
+    <h5><a name="elementLink">Modyfing virtual link state</a></h5>
+<pre>
+  ...
+  &lt;devices&gt;
+    &lt;interface type='network'&gt;
+      &lt;source network='default'/&gt;
+      &lt;target dev='vnet0'/&gt;
+      <b>&lt;link state='down'/&gt;</b>
+    &lt;/interface&gt;
+  &lt;devices&gt;
+  ...</pre>
+
+    <p>
+      This element provides means of setting state of the virtual network link.
+      Possible values for attribute <code>state</code> are <code>up</code> and
+      <code>down</code>. If <code>down</code> is specified as the value, the interface
+      behaves as if it had the network cable disconnected. Default behavior if this
+      element is unspecified is to have the link state <code>up</code>.
+      <span class="since">Since 0.9.5</span>
+    </p>
+
     <h4><a name="elementsInput">Input devices</a></h4>
 
     <p>

docs/schemas/network.rng

@@ -150,6 +150,17 @@
        <optional>
          <ref name="bandwidth"/>
        </optional>
+       <optional>
+         <element name="link">
+           <attribute name="state">
+             <choice>
+               <value>up</value>
+               <value>down</value>
+             </choice>
+           </attribute>
+           <empty/>
+         </element>
+        </optional>
 
         <!-- <ip> element -->
         <zeroOrMore>

src/conf/domain_conf.c

@@ -257,6 +257,11 @@ VIR_ENUM_IMPL(virDomainNetVirtioTxMode, VIR_DOMAIN_NET_VIRTIO_TX_MODE_LAST,
               "iothread",
               "timer")
 
+VIR_ENUM_IMPL(virDomainNetInterfaceLinkState, VIR_DOMAIN_NET_INTERFACE_LINK_STATE_LAST,
+              "default",
+              "up",
+              "down")
+
 VIR_ENUM_IMPL(virDomainChrChannelTarget,
               VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_LAST,
               "guestfwd",
@@ -2980,6 +2985,7 @@ virDomainNetDefParseXML(virCapsPtr caps,
     char *internal = NULL;
     char *devaddr = NULL;
     char *mode = NULL;
+    char *linkstate = NULL;
     virNWFilterHashTablePtr filterparams = NULL;
     virVirtualPortProfileParamsPtr virtPort = NULL;
     virDomainActualNetDefPtr actual = NULL;
@@ -3056,6 +3062,9 @@ virDomainNetDefParseXML(virCapsPtr caps,
                     /* An auto-generated target name, blank it out */
                     VIR_FREE(ifname);
                 }
+            } else if ((linkstate == NULL) &&
+                       xmlStrEqual(cur->name, BAD_CAST "link")) {
+                linkstate = virXMLPropString(cur, "state");
             } else if ((script == NULL) &&
                        (def->type == VIR_DOMAIN_NET_TYPE_ETHERNET ||
                         def->type == VIR_DOMAIN_NET_TYPE_BRIDGE) &&
@@ -3320,6 +3329,16 @@ virDomainNetDefParseXML(virCapsPtr caps,
         }
     }
 
+    def->linkstate = VIR_DOMAIN_NET_INTERFACE_LINK_STATE_DEFAULT;
+    if (linkstate != NULL) {
+        if ((def->linkstate = virDomainNetInterfaceLinkStateTypeFromString(linkstate)) <= 0) {
+            virDomainReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                                 _("unknown interface link state '%s'"),
+                                 linkstate);
+            goto error;
+        }
+    }
+
     if (filter != NULL) {
         switch (def->type) {
         case VIR_DOMAIN_NET_TYPE_ETHERNET:
@@ -3367,6 +3386,7 @@ cleanup:
     VIR_FREE(internal);
     VIR_FREE(devaddr);
     VIR_FREE(mode);
+    VIR_FREE(linkstate);
     virNWFilterHashTableFree(filterparams);
 
     return def;
@@ -9510,6 +9530,10 @@ virDomainNetDefFormat(virBufferPtr buf,
         virBufferAddLit(buf,   "      </tune>\n");
     }
 
+    if (def->linkstate)
+        virBufferAsprintf(buf, "      <link state='%s'/>\n",
+                          virDomainNetInterfaceLinkStateTypeToString(def->linkstate));
+
     if (virBandwidthDefFormat(buf, def->bandwidth, "      ") < 0)
         return -1;
 

src/conf/domain_conf.h

@@ -410,6 +410,15 @@ enum virDomainNetVirtioTxModeType {
     VIR_DOMAIN_NET_VIRTIO_TX_MODE_LAST,
 };
 
+/* link interface states */
+enum virDomainNetInterfaceLinkState {
+        VIR_DOMAIN_NET_INTERFACE_LINK_STATE_DEFAULT = 0, /* Default link state (up) */
+        VIR_DOMAIN_NET_INTERFACE_LINK_STATE_UP,          /* Link is up. ("cable" connected) */
+        VIR_DOMAIN_NET_INTERFACE_LINK_STATE_DOWN ,       /* Link is down. ("cable" disconnected) */
+
+        VIR_DOMAIN_NET_INTERFACE_LINK_STATE_LAST
+};
+
 /* Config that was actually used to bring up interface, after
  * resolving network reference. This is private data, only used within
  * libvirt, but still must maintain backward compatibility, because
@@ -495,6 +504,7 @@ struct _virDomainNetDef {
     char *filter;
     virNWFilterHashTablePtr filterparams;
     virBandwidthPtr bandwidth;
+    int linkstate;
 };
 
 /* Used for prefix of ifname of any network name generated dynamically
@@ -1829,6 +1839,7 @@ VIR_ENUM_DECL(virDomainFSAccessMode)
 VIR_ENUM_DECL(virDomainNet)
 VIR_ENUM_DECL(virDomainNetBackend)
 VIR_ENUM_DECL(virDomainNetVirtioTxMode)
+VIR_ENUM_DECL(virDomainNetInterfaceLinkState)
 VIR_ENUM_DECL(virDomainChrDevice)
 VIR_ENUM_DECL(virDomainChrChannelTarget)
 VIR_ENUM_DECL(virDomainChrConsoleTarget)