[pve-devel] [PATCH v2 container 3/4] lxc: Add `link-down` config to allow setting interfaces as disconnected

[Christoph Heiss]

If this network option is set, the host-side link will be forced down
and the interface won't be connected to the bridge.

Signed-off-by: Christoph Heiss <c.heiss at proxmox.com>
---
Changes v1 -> v2:
 * Split trailing whitespace fix into separate patch
 * Rename option to kebap-case
 * Proper option comparison using `safe_boolean_ne`
 * Copy option to new network conf like the other options
 * Remove the veth interface from the bridge when disconnected

 src/PVE/LXC.pm        | 41 ++++++++++++++++++++++++++++++++++-------
 src/PVE/LXC/Config.pm |  5 +++++
 src/lxcnetaddbr       |  7 +++++--
 3 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index 0de5ba3..1b93f48 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -955,7 +955,8 @@ sub update_net {
 	} else {
 	    if (safe_string_ne($oldnet->{bridge}, $newnet->{bridge}) ||
 		safe_num_ne($oldnet->{tag}, $newnet->{tag}) ||
-		safe_num_ne($oldnet->{firewall}, $newnet->{firewall})
+		safe_num_ne($oldnet->{firewall}, $newnet->{firewall}) ||
+		safe_boolean_ne($oldnet->{'link-down'}, $newnet->{'link-down'})
 	    ) {

 		if ($oldnet->{bridge}) {
@@ -968,10 +969,28 @@ sub update_net {
 		}

 		my ($bridge, $mac, $firewall, $rate) = $newnet->@{'bridge', 'hwaddr', 'firewall', 'rate'};
-		PVE::LXC::net_tap_plug($veth, $bridge, $newnet->{tag}, $firewall, $newnet->{trunks}, $rate, { mac => $mac });
+
+		if (defined($newnet->{'link-down'})) {
+		    # The interface must not be connected to the designated
+		    # bridge if the link was requested to be disconnected.
+		    # Otherwise it could get re-enabled by something like
+		    # `ifreload`.
+		    #
+		    # Thus only force the host-side link down here and skip
+		    # adding it to the bridge.
+		    PVE::Tools::run_command(['/sbin/ip', 'link', 'set', 'dev', $veth, 'down']);
+		} else {
+		    # Connect the interface to the bridge
+		    PVE::LXC::net_tap_plug(
+			$veth, $bridge, $newnet->{tag}, $firewall, $newnet->{trunks}, $rate, { mac => $mac });
+
+		    # Force the host-side link up if it was previously down.
+		    PVE::Tools::run_command(['/sbin/ip', 'link', 'set', 'dev', $veth, 'up'])
+			if defined($oldnet->{'link-down'});
+		}

 		# This includes the rate:
-		foreach (qw(bridge tag firewall rate)) {
+		foreach (qw(bridge tag firewall rate link-down)) {
 		    $oldnet->{$_} = $newnet->{$_} if $newnet->{$_};
 		}
 	    } elsif (safe_string_ne($oldnet->{rate}, $newnet->{rate})) {
@@ -1002,9 +1021,6 @@ sub hotplug_net {
     } else {
 	PVE::Network::veth_create($veth, $vethpeer, $newnet->{bridge}, $newnet->{hwaddr});
     }
-    PVE::LXC::net_tap_plug(
-	$veth, $newnet->{bridge}, $newnet->{tag}, $newnet->{firewall}, $newnet->{trunks},
-	$newnet->{rate}, { mac => $newnet->{hwaddr} });

     # attach peer in container
     my $cmd = ['lxc-device', '-n', $vmid, 'add', $vethpeer, "$eth" ];
@@ -1014,8 +1030,19 @@ sub hotplug_net {
     $cmd = ['lxc-attach', '-n', $vmid, '-s', 'NETWORK', '--', '/sbin/ip', 'link', 'set', $eth ,'up'  ];
     PVE::Tools::run_command($cmd);

+    if (defined($newnet->{'link-down'})) {
+	# In case the network device should be disconnected, force the host-link down ..
+	PVE::Tools::run_command(['/sbin/ip', 'link', 'set', 'dev', $veth, 'down']);
+    } else {
+	# .. otherwise, connect it normally to the bridge.
+	# The interface is already up from creation.
+	PVE::LXC::net_tap_plug(
+	    $veth, $newnet->{bridge}, $newnet->{tag}, $newnet->{firewall}, $newnet->{trunks},
+	    $newnet->{rate}, { mac => $newnet->{hwaddr} });
+    }
+
     my $done = { type => 'veth' };
-    foreach (qw(bridge tag firewall hwaddr name)) {
+    foreach (qw(bridge tag firewall hwaddr name link-down)) {
 	$done->{$_} = $newnet->{$_} if $newnet->{$_};
     }
     $conf->{$opt} = PVE::LXC::Config->print_lxc_network($done);
diff --git a/src/PVE/LXC/Config.pm b/src/PVE/LXC/Config.pm
index af25a96..26a2fac 100644
--- a/src/PVE/LXC/Config.pm
+++ b/src/PVE/LXC/Config.pm
@@ -814,6 +814,11 @@ our $netconf_desc = {
 	description => "Apply rate limiting to the interface",
 	optional => 1,
     },
+    'link-down' => {
+	type => 'boolean',
+	description => 'Whether this interface should be disconnected (like pulling the plug).',
+	optional => 1,
+    },
 };
 PVE::JSONSchema::register_format('pve-lxc-network', $netconf_desc);

diff --git a/src/lxcnetaddbr b/src/lxcnetaddbr
index ebd6baa..c5d724b 100755
--- a/src/lxcnetaddbr
+++ b/src/lxcnetaddbr
@@ -52,10 +52,13 @@ if (-d "/sys/class/net/$iface") {
     #avoid insecure dependency;
     ($bridgemtu) = $bridgemtu =~ /(\d+)/;

-    PVE::Tools::run_command("/sbin/ip link set dev $iface up mtu $bridgemtu");
+    my $linkstate = defined($net->{'link-down'}) ? 'down' : 'up';
+    PVE::Tools::run_command("/sbin/ip link set dev $iface $linkstate mtu $bridgemtu");
     PVE::Tools::run_command("/sbin/ip addr add 0.0.0.0/0 dev $iface");

-    PVE::LXC::net_tap_plug($iface, $bridge, $tag, $firewall, $trunks, $rate, { mac => $hwaddr });
+    # Only plug the interface into the bridge if it is not set as disconnected by the user.
+    PVE::LXC::net_tap_plug($iface, $bridge, $tag, $firewall, $trunks, $rate, { mac => $hwaddr })
+	if !defined($net->{'link-down'});
 }

 exit 0;
--
2.39.1