conf: allow setting peer address in <ip> element of <interface>

The peer attribute is used to set the property of the same name in the
interface IP info:

  <interface type='ethernet'>
    ...
    <ip family='ipv4' address='192.168.122.5'
        prefix='32' peer='192.168.122.6'/>
    ...
  </interface>

Note that this element is used to set the IP information on the
*guest* side interface, not the host side interface - that will be
supported in an upcoming patch.

(This is an updated *re*-commit of commit 690969af, which was
subsequently reverted in commit 1d14b13f).
Signed-off-by: NVasiliy Tolstov <v.tolstov@selfip.ru>
Signed-off-by: NLaine Stump <laine@laine.org>

docs/formatdomain.html.in

@@ -4967,6 +4967,7 @@ qemu-kvm -net nic,model=? /dev/null
       <source network='default'/>
       <target dev='vnet0'/>
       <b>&lt;ip address='192.168.122.5' prefix='24'/&gt;</b>
+      <b>&lt;ip address='192.168.122.5' prefix='24' peer='10.0.0.10'/&gt;</b>
       <b>&lt;route family='ipv4' address='192.168.122.0' prefix='24' gateway='192.168.122.1'/&gt;</b>
       <b>&lt;route family='ipv4' address='192.168.122.8' gateway='192.168.122.1'/&gt;</b>
     &lt;/interface&gt;
@@ -4985,21 +4986,30 @@ qemu-kvm -net nic,model=? /dev/null
 </pre>
 
     <p>
-    <span class="since">Since 1.2.12</span> the network devices and host devices
-    with network capabilities can be provided zero or more IP addresses to set
-    on the target device. Note that some hypervisors or network device types
-    will simply ignore them or only use the first one. The <code>family</code>
-    attribute can be set to either <code>ipv4</code> or <code>ipv6</code>, the
-    <code>address</code> attribute holds the IP address. The <code>prefix</code>
-    is not mandatory since some hypervisors do not handle it.
-    </p>
-
-    <p>
-    <span class="since">Since 1.2.12</span> route elements can also be added
-    to define the network routes to use for the network device. The attributes
-    of this element are described in the documentation for the <code>route</code>
-    element in <a href="formatnetwork.html#elementsStaticroute">network definitions</a>.
-    This is only used by the LXC driver.
+      <span class="since">Since 1.2.12</span> network devices and
+      hostdev devices with network capabilities can optionally be provided
+      one or more IP addresses to set on the network device in the
+      guest. Note that some hypervisors or network device types will
+      simply ignore them or only use the first one.
+      The <code>family</code> attribute can be set to
+      either <code>ipv4</code> or <code>ipv6</code>, and the
+      <code>address</code> attribute contains the IP address. The
+      optional <code>prefix</code> is the number of 1 bits in the
+      netmask, and will be automatically set if not specified - for
+      IPv4 the default prefix is determined according to the network
+      "class" (A, B, or C - see RFC870), and for IPv6 the default
+      prefix is 64. The optional <code>peer</code> attribute holds the
+      IP address of the other end of a point-to-point network
+      device <span class="since">(since 2.0.0)</span>.
+    </p>
+
+    <p>
+    <span class="since">Since 1.2.12</span> route elements can also be
+    added to define IP routes to add in the guest.  The attributes of
+    this element are described in the documentation for
+    the <code>route</code> element
+    in <a href="formatnetwork.html#elementsStaticroute">network
+    definitions</a>.  This is used by the LXC driver.
     </p>
 
     <h5><a name="elementVhostuser">vhost-user interface</a></h5>

docs/schemas/domaincommon.rng

@@ -2629,6 +2629,11 @@
             <ref name="ipPrefix"/>
           </attribute>
         </optional>
+        <optional>
+          <attribute name="peer">
+            <ref name="ipAddr"/>
+          </attribute>
+        </optional>
         <empty/>
       </element>
     </zeroOrMore>

src/conf/domain_conf.c

@@ -6121,7 +6121,7 @@ virDomainNetIPParseXML(xmlNodePtr node)
     unsigned int prefixValue = 0;
     char *familyStr = NULL;
     int family = AF_UNSPEC;
-    char *address = NULL;
+    char *address = NULL, *peer = NULL;
 
     if (!(address = virXMLPropString(node, "address"))) {
         virReportError(VIR_ERR_XML_ERROR, "%s",
@@ -6159,6 +6159,13 @@ virDomainNetIPParseXML(xmlNodePtr node)
     }
     ip->prefix = prefixValue;
 
+    if ((peer = virXMLPropString(node, "peer")) != NULL &&
+        virSocketAddrParse(&ip->peer, peer, family) < 0) {
+        virReportError(VIR_ERR_INVALID_ARG,
+                       _("Invalid peer '%s' in <ip>"), peer);
+        goto cleanup;
+    }
+
     ret = ip;
     ip = NULL;
 
@@ -6166,6 +6173,7 @@ virDomainNetIPParseXML(xmlNodePtr node)
     VIR_FREE(prefixStr);
     VIR_FREE(familyStr);
     VIR_FREE(address);
+    VIR_FREE(peer);
     VIR_FREE(ip);
     return ret;
 }
@@ -20264,6 +20272,12 @@ virDomainNetIPInfoFormat(virBufferPtr buf,
             virBufferAsprintf(buf, " family='%s'", familyStr);
         if (def->ips[i]->prefix)
             virBufferAsprintf(buf, " prefix='%u'", def->ips[i]->prefix);
+        if (VIR_SOCKET_ADDR_VALID(&def->ips[i]->peer)) {
+            if (!(ipStr = virSocketAddrFormat(&def->ips[i]->peer)))
+                return -1;
+            virBufferAsprintf(buf, " peer='%s'", ipStr);
+            VIR_FREE(ipStr);
+        }
         virBufferAddLit(buf, "/>\n");
     }
 

src/util/virnetdevip.h

@@ -27,7 +27,8 @@
 
 typedef struct {
     virSocketAddr address; /* ipv4 or ipv6 address */
-    unsigned int prefix; /* number of 1 bits in the net mask */
+    virSocketAddr peer;    /* ipv4 or ipv6 address of peer */
+    unsigned int prefix;   /* number of 1 bits in the netmask */
 } virNetDevIPAddr, *virNetDevIPAddrPtr;
 
 typedef struct {