[Libguestfs] [PATCH v3 2/4] launch: libvirt: Use qemu-bridge-helper to implement a full network (RHBZ#1148012).

[Richard W.M. Jones]

When using the libvirt backend, don't use the SLIRP.  Use
qemu-bridge-helper via libvirt to give us a full network connection.

One consequence of this is that 'ping' works in
'virt-builder --run-command'.

A less useful consequence is that the host firewall will prevent
connections on non-standard ports to the host.  So you can't (eg)
connect to a rsync daemon on the host listening on an arbitrary port,
which worked before.

The default bridge is 'virbr0', but you can override this by setting
LIBGUESTFS_BACKEND_SETTINGS=network_bridge=<some_bridge>

Note: this does not fix virt-rescue (since it overrides the default
backend and uses 'direct' for various reasons).
---
 src/guestfs.pod      | 10 ++++++++++
 src/launch-libvirt.c | 44 +++++++++++++++++++++++---------------------
 2 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/src/guestfs.pod b/src/guestfs.pod
index e4f9b54..f133fee 100644
--- a/src/guestfs.pod
+++ b/src/guestfs.pod
@@ -1519,6 +1519,16 @@ On Fedora, install C<kernel-debuginfo> for the C<vmlinux> file
 (containing symbols).  Make sure the symbols precisely match the
 kernel being used.
 
+=head3 network_bridge
+
+The libvirt backend supports:
+
+ export LIBGUESTFS_BACKEND_SETTINGS=network_bridge=virbrX
+
+This allows you to override the bridge that is connected to when the
+network is enabled.  The default is C<virbr0>.  See also
+L</guestfs_set_network>.
+
 =head2 ATTACHING TO RUNNING DAEMONS
 
 I<Note (1):> This is B<highly experimental> and has a tendency to eat
diff --git a/src/launch-libvirt.c b/src/launch-libvirt.c
index 706ae38..f8f818a 100644
--- a/src/launch-libvirt.c
+++ b/src/launch-libvirt.c
@@ -105,6 +105,7 @@ struct backend_libvirt_data {
   char *selinux_label;
   char *selinux_imagelabel;
   bool selinux_norelabel_disks;
+  char *network_bridge;
   char name[DOMAIN_NAME_LEN];   /* random name */
   bool is_kvm;                  /* false = qemu, true = kvm (from capabilities)*/
   unsigned long qemu_version;   /* qemu version (from libvirt) */
@@ -325,6 +326,12 @@ launch_libvirt (guestfs_h *g, void *datav, const char *libvirt_uri)
     guestfs_get_backend_setting (g, "internal_libvirt_imagelabel");
   data->selinux_norelabel_disks =
     guestfs___get_backend_setting_bool (g, "internal_libvirt_norelabel_disks");
+  if (g->enable_network) {
+    data->network_bridge =
+      guestfs_get_backend_setting (g, "network_bridge");
+    if (!data->network_bridge)
+      data->network_bridge = safe_strdup (g, "virbr0");
+  }
   guestfs_pop_error_handler (g);
 
   /* Locate and/or build the appliance. */
@@ -1236,6 +1243,19 @@ construct_libvirt_xml_devices (guestfs_h *g,
       } end_element ();
     } end_element ();
 
+    /* Connect to libvirt bridge (see: RHBZ#1148012). */
+    if (g->enable_network) {
+      start_element ("interface") {
+        attribute ("type", "bridge");
+        start_element ("source") {
+          attribute ("bridge", params->data->network_bridge);
+        } end_element ();
+        start_element ("model") {
+          attribute ("type", "virtio");
+        } end_element ();
+      } end_element ();
+    }
+
   } end_element (); /* </devices> */
 
   return 0;
@@ -1617,27 +1637,6 @@ construct_libvirt_xml_qemu_cmdline (guestfs_h *g,
       attribute ("value", tmpdir);
     } end_element ();
 
-    /* Workaround because libvirt user networking cannot specify "net="
-     * parameter.
-     */
-    if (g->enable_network) {
-      start_element ("qemu:arg") {
-        attribute ("value", "-netdev");
-      } end_element ();
-
-      start_element ("qemu:arg") {
-        attribute ("value", "user,id=usernet,net=169.254.0.0/16");
-      } end_element ();
-
-      start_element ("qemu:arg") {
-        attribute ("value", "-device");
-      } end_element ();
-
-      start_element ("qemu:arg") {
-        attribute ("value", VIRTIO_NET ",netdev=usernet");
-      } end_element ();
-    }
-
     /* The qemu command line arguments requested by the caller. */
     for (hp = g->hv_params; hp; hp = hp->next) {
       start_element ("qemu:arg") {
@@ -1707,6 +1706,9 @@ shutdown_libvirt (guestfs_h *g, void *datav, int check_for_errors)
   free (data->selinux_imagelabel);
   data->selinux_imagelabel = NULL;
 
+  free (data->network_bridge);
+  data->network_bridge = NULL;
+
   return ret;
 }
 
-- 
2.0.4