Libguestfs - Oct 2014 - Re: [PATCH v2 1/4] appliance: Use dhclient instead of hard-coding IP address of appliance.

v2:

- Make virbr0 configurable.
- Fix the tests.

qemu in SLIRP mode offers DHCP services to the appliance.  We don't
use them, but use a fixed IP address intead.  This changes the
appliance to get its IP address using DHCP.

Note: This is only used when the network is enabled.  dhclient is
somewhat slower, but the penalty (a few seconds) is only paid for
network users.  We could consider using the faster systemd dhcp client
instead.
---
 appliance/init           | 9 +++------
 appliance/packagelist.in | 1 +
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/appliance/init b/appliance/init
index 6d62338..d688a52 100755
--- a/appliance/init
+++ b/appliance/init
@@ -79,12 +79,9 @@ hwclock -u -s
 ip addr add 127.0.0.1/8 brd + dev lo scope host
 ip link set dev lo up
 
-ip addr add 169.254.2.10/16 brd + dev eth0 scope global
-ip link set dev eth0 up
-
-ip route add default via 169.254.2.2
-
-echo nameserver 169.254.2.3 > /etc/resolv.conf
+if grep -sq guestfs_network=1 /proc/cmdline; then
+    dhclient
+fi
 
 # Scan for MDs.
 mdadm -As --auto=yes --run
diff --git a/appliance/packagelist.in b/appliance/packagelist.in
index 276b4c2..4e93eaf 100644
--- a/appliance/packagelist.in
+++ b/appliance/packagelist.in
@@ -210,6 +210,7 @@ binutils
 bzip2
 coreutils
 cpio
+dhclient
 diffutils
 dosfstools
 e2fsprogs
-- 
2.0.4

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

This are commented out (still) so this change does nothing.
---
 appliance/init | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/appliance/init b/appliance/init
index d688a52..b1e7184 100755
--- a/appliance/init
+++ b/appliance/init
@@ -110,8 +110,7 @@ if grep -sq guestfs_verbose=1 /proc/cmdline; then
     date
     echo -n "clocksource: "
     cat /sys/devices/system/clocksource/clocksource0/current_clocksource
-    #ping -n -v -c 5 10.0.2.2
-    #ping -n -v -c 5 10.0.2.4
+    #ping -n -v -c 5 8.8.8.8
 
     echo -n "uptime: "; cat /proc/uptime
 fi
-- 
2.0.4

It would work, except if you have a host firewall which will block
inbound connections on virbr0 to non-standard ports.
---
 tests/rsync/test-rsync.sh | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/tests/rsync/test-rsync.sh b/tests/rsync/test-rsync.sh
index 793d59d..53fcab8 100755
--- a/tests/rsync/test-rsync.sh
+++ b/tests/rsync/test-rsync.sh
@@ -33,10 +33,33 @@ if ! rsync --help >/dev/null 2>&1; then
     exit 77
 fi
 
-if [ "$(guestfish get-backend)" = "uml" ]; then
-    echo "$0: skipping test because networking is not available in the UML
backend"
-    exit 77
-fi
+# Get host IP address.  XXX Bit of a hack.
+backend="$(guestfish get-backend)"
+case "$backend" in
+    direct)
+        ip=169.254.2.2
+        listen_address=localhost
+        ;;
+    libvirt|libvirt:*)
+        # This would work, except that the host firewall is effective
+        # on virbr0, and that is likely to block the non-standard port
+        # number that we listen on.
+#        ip="$(ip -4 -o address show virbr0 |
+#                  awk '{print $4}' |
+#                  awk -F/ '{print $1}')"
+#        listen_address="$ip"
+        echo "$0: skipping test because host firewall will probably
prevent this test from working"
+        exit 77
+        ;;
+    uml)
+        echo "$0: skipping test because networking is not available in the
UML backend"
+        exit 77
+        ;;
+    *)
+        echo "$0: don't know how to get IP address of backend
$backend"
+        exit 77
+        ;;
+esac
 
 # If rsync is not available, bail.
 if ! guestfish -a /dev/null run : available rsync; then
@@ -56,7 +79,7 @@ port="$(awk 'BEGIN{srand(); print
65000+int(500*rand())}' </dev/null)"
 
 # Write an rsync daemon config file.
 cat > rsyncd.conf <<EOF
-address = localhost
+address = $listen_address
 port = $port
 pid file = $pwd/rsyncd.pid
 [src]
@@ -80,8 +103,6 @@ function cleanup ()
 }
 trap cleanup INT TERM QUIT EXIT
 
-# XXX
-ip=169.254.2.2
 user="$(id -un)"
 
 guestfish --network -N test-rsync.img=fs -m /dev/sda1 <<EOF
-- 
2.0.4

On Thu, Oct 02, Richard W.M. Jones wrote:
> +if grep -sq guestfs_network=1 /proc/cmdline; then
> +    dhclient
> +fi
dhclient will be missing at least in openSUSE. Not an issue now, does
the script fail if the command fails to execute due to ENOENT?

Olaf

On Thursday 02 October 2014 12:39:56 Richard W.M. Jones
wrote:
> qemu in SLIRP mode offers DHCP services to the appliance.  We don't
> use them, but use a fixed IP address intead.  This changes the
> appliance to get its IP address using DHCP.
> 
> Note: This is only used when the network is enabled.  dhclient is
> somewhat slower, but the penalty (a few seconds) is only paid for
> network users.  We could consider using the faster systemd dhcp client
> instead.
> ---
>  appliance/init           | 9 +++------
>  appliance/packagelist.in | 1 +
>  2 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/appliance/init b/appliance/init
> index 6d62338..d688a52 100755
> --- a/appliance/init
> +++ b/appliance/init
> @@ -79,12 +79,9 @@ hwclock -u -s
>  ip addr add 127.0.0.1/8 brd + dev lo scope host
>  ip link set dev lo up
> 
> -ip addr add 169.254.2.10/16 brd + dev eth0 scope global
> -ip link set dev eth0 up
> -
> -ip route add default via 169.254.2.2
> -
> -echo nameserver 169.254.2.3 > /etc/resolv.conf
> +if grep -sq guestfs_network=1 /proc/cmdline; then
> +    dhclient
> +fi
When I tried v1 of this patch, with direct backend I still needed the 
manual filling of /etc/resolv.conf, otherwise it was not able to resolve 
names.
> diff --git a/appliance/packagelist.in b/appliance/packagelist.in
> index 276b4c2..4e93eaf 100644
> --- a/appliance/packagelist.in
> +++ b/appliance/packagelist.in
> @@ -210,6 +210,7 @@ binutils
>  bzip2
>  coreutils
>  cpio
> +dhclient
>  diffutils
>  dosfstools
>  e2fsprogs
This should be moved to the REDHAT section, as this package name differs 
between distributions:
- REDHAT: dhclient
- DEBIAN: isc-dhcp-client
- ARCHLINUX: dhclient

-- 
Pino Toscano