fix(networks): fixed addresses, failed creates and stopped networks behave

- A network created with fixed addresses gets one per address of its DHCP
  range for any subnet; the old prefix cut assumed a gateway ending in .1
  and built addresses such as 10.0.0.1.130. Fixed addresses need a /24 or
  smaller subnet.
- A new network that does not start (its subnet is in use) is undefined
  again, so the name is free for another try.
- Fixed addresses are changed and deleted on a stopped network too: the
  running network is changed only while it runs. A host with only a name
  is deleted as defined, not with an empty MAC, shows no "None", and has no
  edit button it could not use.
- The create dialog disables the fields it hides, so an IPv6 subnet typed
  and then unchecked is not created, and switching from MACVTAP back to
  BRIDGE restores the bridge label and the Open vSwitch option.
- Isolated networks show QoS; QoS save buttons no longer raise a script
  error; saving an unchanged fixed address says so; two messages lose a
  stray backslash and spaces.

vrtManager/network.py

@@ -50,9 +50,6 @@ class wvmNetworks(wvmConnect):
 
         return networks
 
-    def define_network(self, xml):
-        self.wvm.networkDefineXML(xml)
-
     def create_network(
         self,
         name,
@@ -104,11 +101,9 @@ class wvmNetworks(wvmConnect):
                     xml += f"""<dhcp>
                                 <range start='{dhcp4_0}' end='{dhcp4_1}' />"""
                     if fixed:
-                        fist_oct = int(dhcp4[0].strip().split(".")[3])
-                        last_oct = int(dhcp4[1].strip().split(".")[3])
-                        gw_prefix = util.xml_escape(str(gateway)[:-2])
-                        for ip in range(fist_oct, last_oct + 1):
-                            xml += f"""<host mac='{util.randomMAC()}' ip='{gw_prefix}.{ip}' />"""
+                        first, last = (int(ipaddress.IPv4Address(ip)) for ip in dhcp4)
+                        for ip in range(first, last + 1):
+                            xml += f"""<host mac='{util.randomMAC()}' ip='{ipaddress.IPv4Address(ip)}' />"""
                     xml += """</dhcp>"""
                 xml += """</ip>"""
             if ipv6:
@@ -121,9 +116,12 @@ class wvmNetworks(wvmConnect):
                     xml += """</dhcp>"""
                 xml += """</ip>"""
         xml += """</network>"""
-        self.define_network(xml)
-        net = self.get_network(name)
-        net.create()
+        net = self.wvm.networkDefineXML(xml)
+        try:
+            net.create()
+        except libvirtError:  # e.g. the subnet is in use: the name stays free for another try
+            net.undefine()
+            raise
         net.setAutostart(1)
 
 
@@ -182,7 +180,10 @@ class wvmNetwork(wvmConnect):
                                       "start; remove their network cards first")
         self.net.undefine()
 
-    def update(self, command, section, xml, parentIndex, flags=0):
+    def update(self, command, section, xml, parentIndex):
+        """Changes the network's configuration and, while it runs, the running
+        network too (libvirt refuses a live change on a stopped one)."""
+        flags = VIR_NETWORK_UPDATE_AFFECT_CONFIG | (VIR_NETWORK_UPDATE_AFFECT_LIVE if self.is_active() else 0)
         return self.net.update(command, section, parentIndex, xml, flags)
 
     def get_ip_networks(self):
@@ -289,22 +290,13 @@ class wvmNetwork(wvmConnect):
             parent_index = self.parent_count - 1
         for h in hosts:
             if h.get("ip") == ip:
-                h_name = util.xml_escape(h.get("name") or "")
-                name_attr = f' name="{h_name}"' if h.get("name") else ""
-                ip_esc = util.xml_escape(ip)
-                if family == "ipv4":
-                    h_mac = util.xml_escape(h.get("mac") or "")
-                    new_xml = f'<host mac="{h_mac}"{name_attr} ip="{ip_esc}"/>'
-                if family == "ipv6":
-                    h_id = util.xml_escape(h.get("id") or "")
-                    new_xml = f'<host id="{h_id}"{name_attr} ip="{ip_esc}"/>'
-
+                # the host as it is: a host may have only a name and an address
+                new_xml = etree.tostring(h, with_tail=False).decode()
                 self.update(
                     VIR_NETWORK_UPDATE_COMMAND_DELETE,
                     VIR_NETWORK_SECTION_IP_DHCP_HOST,
                     new_xml,
                     parent_index,
-                    VIR_NETWORK_UPDATE_AFFECT_LIVE | VIR_NETWORK_UPDATE_AFFECT_CONFIG,
                 )
                 break
 
@@ -332,7 +324,6 @@ class wvmNetwork(wvmConnect):
                 VIR_NETWORK_SECTION_IP_DHCP_HOST,
                 new_xml,
                 parent_index,
-                VIR_NETWORK_UPDATE_AFFECT_LIVE | VIR_NETWORK_UPDATE_AFFECT_CONFIG,
             )
         else:
             # change the host
@@ -344,7 +335,6 @@ class wvmNetwork(wvmConnect):
                     VIR_NETWORK_SECTION_IP_DHCP_HOST,
                     new_xml,
                     parent_index,
-                    VIR_NETWORK_UPDATE_AFFECT_LIVE | VIR_NETWORK_UPDATE_AFFECT_CONFIG,
                 )
 
     def get_qos(self):