[pve-devel] [PATCH container v3 06/13] configure static IP in LXC config for custom entrypoint

Filip Schauer f.schauer at proxmox.com
Wed Jul 9 14:34:23 CEST 2025


When a container uses the default `/sbin/init` entrypoint, network
interface configuration is usually managed by processes within the
container. However, containers with a different entrypoint might not
have any internal network management process. Consequently, IP addresses
might not be assigned.

This change ensures that a static IP address is explicitly set in the
LXC config for the container.

Signed-off-by: Filip Schauer <f.schauer at proxmox.com>
---
Changed since v2:
* rebase onto newest master (5a8b3f962f16) and re-format with
  proxmox-perltidy
* add an "ipmanagehost" property to pct.conf to control whether network
  interface IP configuration should be handled by the host.

 src/PVE/API2/LXC.pm   |  4 ++++
 src/PVE/LXC.pm        | 15 +++++++++++++++
 src/PVE/LXC/Config.pm | 14 ++++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/src/PVE/API2/LXC.pm b/src/PVE/API2/LXC.pm
index c3d0037..096dfb8 100644
--- a/src/PVE/API2/LXC.pm
+++ b/src/PVE/API2/LXC.pm
@@ -587,6 +587,10 @@ __PACKAGE__->register_method({
                                 # An entrypoint other than /sbin/init breaks the tty console mode.
                                 # This is fixed by setting cmode: console
                                 $conf->{cmode} = 'console';
+
+                                # Manage the IP configuration for the container. A container with a
+                                # custom entrypoint likely lacks internal network management.
+                                $conf->{ipmanagehost} = 1;
                             }
                         }
 
diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index 37ff8e1..7c9caf6 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -835,6 +835,21 @@ sub update_lxc_config {
         if ($lxc_major >= 4) {
             $raw .= "lxc.net.$ind.script.up = /usr/share/lxc/lxcnetaddbr\n";
         }
+
+        if ((!defined($d->{link_down}) || $d->{link_down} != 1) && $conf->{ipmanagehost}) {
+            if (defined($d->{ip})) {
+                die "$k: DHCP is not supported with a custom entrypoint\n" if $d->{ip} eq 'dhcp';
+                $raw .= "lxc.net.$ind.ipv4.address = $d->{ip}\n" if $d->{ip} ne 'manual';
+            }
+            $raw .= "lxc.net.$ind.ipv4.gateway = $d->{gw}\n" if defined($d->{gw});
+            if (defined($d->{ip6})) {
+                die "$k: DHCPv6 and SLAAC are not supported with a custom entrypoint\n"
+                    if $d->{ip6} =~ /^(auto|dhcp)$/;
+                $raw .= "lxc.net.$ind.ipv6.address = $d->{ip6}\n" if $d->{ip6} ne 'manual';
+            }
+            $raw .= "lxc.net.$ind.ipv6.gateway = $d->{gw6}\n" if defined($d->{gw6});
+            $raw .= "lxc.net.$ind.flags = up\n";
+        }
     }
 
     my $had_cpuset = 0;
diff --git a/src/PVE/LXC/Config.pm b/src/PVE/LXC/Config.pm
index fb370cf..c2f56e4 100644
--- a/src/PVE/LXC/Config.pm
+++ b/src/PVE/LXC/Config.pm
@@ -594,6 +594,12 @@ my $confdesc = {
             . " This is saved as comment inside the configuration file.",
         maxLength => 1024 * 8,
     },
+    ipmanagehost => {
+        type => 'boolean',
+        description =>
+            "Whether this interface's IP configuration should be managed by the host.",
+        optional => 1,
+    },
     searchdomain => {
         optional => 1,
         type => 'string',
@@ -1284,6 +1290,14 @@ sub update_pct_config {
                 die "$opt: MTU size '$mtu' is bigger than bridge MTU '$bridge_mtu'\n"
                     if ($mtu > $bridge_mtu);
             }
+
+            if ((!defined($res->{link_down}) || $res->{link_down} != 1) && $conf->{ipmanagehost}) {
+                die "$opt: DHCP is not supported with a custom entrypoint\n"
+                    if defined($res->{ip}) && $res->{ip} eq 'dhcp';
+
+                die "$opt: DHCPv6 and SLAAC are not supported with a custom entrypoint\n"
+                    if defined($res->{ip6}) && $res->{ip6} =~ /^(auto|dhcp)$/;
+            }
         } elsif ($opt =~ m/^dev(\d+)$/) {
             my $device = $class->parse_device($value);
 
-- 
2.47.2





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