virsh: new command "domifannounce"

virsh domifannounce is a thin wrapper around the new API
virDomainAnnounceInterface(). Syntax:

     virsh domifannounce guestname [interfacename] [parameters]

where the optional interfacename can be either the MAC address of the
interface to announce, or the name of the tap device used to connect
the domain's interface to the real network (if the connection is with
a tap device), and [parameters] is one or more of the following options:

  --initial [unsigned integer]
  --max     [unsigned integer]
  --rounds  [unsigned integer]
  --step    [unsigned integer]

For example:

    virsh domifannounce myguest 52:54:00:BE:EF:E1 --initial 100
    virsh domifannounce other vnet2
    virsh domifannounce myguest

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>

docs/manpages/virsh.rst

@@ -2328,6 +2328,47 @@ exclusive. If no flag is specified, behavior is different depending
 on hypervisor.
 
 
+domifannounce
+-------------
+
+**Syntax**
+
+::
+
+   domifannounce domain [interface-device] [parameters]
+
+
+Request that a domain inject "gratuitous" ARP responses into the
+outbound data stream of a specific network interface of the domain (or
+if no interface-device is given, inject ARP responses on the outbound
+data stream of all interfaces of the domain). This can be helpful to
+re-sync network switches in the broadcast domain of said interfaces
+when the network topology has changed. This is usually done
+automatically when a domain is started, or after it has migrated (for
+example, that is the behavior of QEMU), but a more complicated setup
+where the topology changes around an already active domain (or
+possibly all the plumbing isn't yet connected and passing traffic at
+the time the automatic announcement takes place) might benefit from a
+manually triggered announce.
+
+The optional parameters are:
+
+- *--initial n*
+
+  initial delay before first announcement (milliseconds) default: 50
+
+- *--max n*
+
+  maximum delay between announcements (milliseconds) default: 550
+
+- *--rounds n*
+
+  total number of announcements default: 5
+
+- *--step n*
+
+  increment added to delay (milliseconds) after each announcement default 50
+
 dominfo
 -------