Re: [pve-devel] [PATCH container v3 09/13] manage DHCP for containers with custom entrypoint

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

On Wed, Jul 09, 2025 at 02:34:26PM +0200, Filip Schauer wrote:
> Containers that do not use the default `/sbin/init` entrypoint may lack

^ This commit message needs updating to reflect the changes in this
version.

> in-container network management. A previous commit already handles
> static IP addresses. Now this commit also handles DHCP. This is done
> using a `dhclient` process for each network interface.
> 
> Signed-off-by: Filip Schauer <f.schauer@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.
> * manage_dhclient: add a FIXME comment regarding the AppArmor profile:
>   "use a profile that confines writes to /var/lib/lxc/$vmid and rootfs"
> * kill_dhclients: untaint pid from pidfile
> * fix manage_dhclient called with 'stop' instead of 'start' for IPv6
>   when container is started
> 
>  src/PVE/LXC.pm        | 103 +++++++++++++++++++++++++++++++++++++-----
>  src/PVE/LXC/Config.pm |  17 ++++---
>  2 files changed, 101 insertions(+), 19 deletions(-)
> 
> diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
> index 7c9caf6..4f19a21 100644
> --- a/src/PVE/LXC.pm
> +++ b/src/PVE/LXC.pm
> @@ -837,15 +837,12 @@ sub update_lxc_config {
>          }
>  
>          if ((!defined($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.address = $d->{ip}\n"
> +                if defined($d->{ip}) && $d->{ip} !~ /^(dhcp|manual)$/;
>              $raw .= "lxc.net.$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 $d->{ip6} ne 'manual';
> +                die "$k: SLAAC is not supported with a custom entrypoint\n" if $d->{ip6} eq 'auto';
> +                $raw .= "lxc.net.$ind.ipv6.address = $d->{ip6}\n" if $d->{ip6} !~ /^(dhcp|manual)$/;
>              }
>              $raw .= "lxc.net.$ind.ipv6.gateway = $d->{gw6}\n" if defined($d->{gw6});
>              $raw .= "lxc.net.$ind.flags = up\n";
> @@ -1028,6 +1025,8 @@ sub vm_stop_cleanup {
>          PVE::Storage::deactivate_volumes($storage_cfg, $vollist);
>      };
>      warn $@ if $@; # avoid errors - just warn
> +
> +    kill_dhclients($vmid, '*') if $conf->{ipmanagehost};
>  }
>  
>  sub net_tap_plug : prototype($$) {
> @@ -1259,6 +1258,52 @@ sub get_interfaces {
>      return $res;
>  }
>  
> +sub manage_dhclient {
> +    my ($action, $vmid, $ipversion, $eth, $rootdir) = @_;
> +
> +    File::Path::make_path("/var/lib/lxc/$vmid/hook") if $action eq 'start';
> +    my $pidfile = "/var/lib/lxc/$vmid/hook/dhclient$ipversion-$eth.pid";
> +    my $leasefile = "/var/lib/lxc/$vmid/hook/dhclient$ipversion-$eth.leases";
> +    my $scriptfile = '/usr/share/lxc/hooks/dhclient-script';
> +    PVE::Tools::run_command([
> +        'lxc-attach',
> +        '-n',
> +        $vmid,
> +        '-s',
> +        'NETWORK|UTSNAME',
> +        '--',
> +        'aa-exec',
> +        '-p',
> +        'unconfined', # FIXME: use a profile that confines writes to /var/lib/lxc/$vmid and rootfs
> +        '/sbin/dhclient',
> +        $action eq 'start' ? '-1' : '-r',
> +        "-$ipversion",
> +        '-pf',
> +        $pidfile,
> +        '-lf',
> +        $leasefile,
> +        '-e',
> +        "ROOTFS=$rootdir",
> +        '-sf',
> +        $scriptfile,
> +        $eth,
> +    ]);
> +}
> +
> +sub kill_dhclients {
> +    my ($vmid, $eth) = @_;
> +
> +    foreach my $pidfile (glob("/var/lib/lxc/$vmid/hook/dhclient*-$eth.pid")) {
> +        my $pid = eval { file_get_contents($pidfile) };
> +        if (!$@) {
> +            chomp $pid;
> +            next if $pid !~ /^(\d+)$/;
> +            kill 9, $1;
> +            unlink($pidfile);
> +        }
> +    }
> +}
> +
>  sub update_ipconfig {
>      my ($vmid, $conf, $opt, $eth, $newnet, $rootdir) = @_;
>  
> @@ -1295,11 +1340,21 @@ sub update_ipconfig {
>  
>          # step 1: add new IP, if this fails we cancel
>          my $is_real_ip = ($newip && $newip !~ /^(?:auto|dhcp|manual)$/);
> -        if ($change_ip && $is_real_ip) {
> -            eval { &$ipcmd($family_opt, 'addr', 'add', $newip, 'dev', $eth); };
> -            if (my $err = $@) {
> -                warn $err;
> -                return;
> +        if ($change_ip) {
> +            if ($conf->{ipmanagehost}) {
> +                if ($newip && $newip eq 'dhcp') {
> +                    manage_dhclient('start', $vmid, $ipversion, $eth, $rootdir);
> +                } elsif ($oldip && $oldip eq 'dhcp') {
> +                    manage_dhclient('stop', $vmid, $ipversion, $eth, $rootdir);
> +                }
> +            }
> +
> +            if ($is_real_ip) {
> +                eval { &$ipcmd($family_opt, 'addr', 'add', $newip, 'dev', $eth); };
> +                if (my $err = $@) {
> +                    warn $err;
> +                    return;
> +                }
>              }
>          }
>  
> @@ -2827,6 +2882,30 @@ sub vm_start {
>      }
>      PVE::GuestHelpers::exec_hookscript($conf, $vmid, 'post-start');
>  
> +    if ($conf->{ipmanagehost}) {
> +        my @dhcpv4_interfaces = ();
> +        my @dhcpv6_interfaces = ();
> +        foreach my $k (sort keys %$conf) {
> +            next if $k !~ m/^net(\d+)$/;
> +            my $d = PVE::LXC::Config->parse_lxc_network($conf->{$k});
> +            push @dhcpv4_interfaces, $d->{name} if $d->{ip} && $d->{ip} eq 'dhcp';
> +            push @dhcpv6_interfaces, $d->{name} if $d->{ip6} && $d->{ip6} eq 'dhcp';
> +        }
> +
> +        my $pid = PVE::LXC::find_lxc_pid($vmid);
> +        my $rootdir = "/proc/$pid/root";
> +
> +        foreach my $eth (@dhcpv4_interfaces) {
> +            eval { manage_dhclient('start', $vmid, 4, $eth, $rootdir) };
> +            PVE::RESTEnvironment::log_warn("DHCP failed - $@") if $@;
> +        }
> +
> +        foreach my $eth (@dhcpv6_interfaces) {
> +            eval { manage_dhclient('start', $vmid, 6, $eth, $rootdir) };
> +            PVE::RESTEnvironment::log_warn("DHCP failed - $@") if $@;
> +        }
> +    }
> +
>      return;
>  }
>  
> diff --git a/src/PVE/LXC/Config.pm b/src/PVE/LXC/Config.pm
> index c2f56e4..39c3243 100644
> --- a/src/PVE/LXC/Config.pm
> +++ b/src/PVE/LXC/Config.pm
> @@ -1291,12 +1291,13 @@ sub update_pct_config {
>                      if ($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}) && $res->{ip6} =~ /^(auto|dhcp)$/;
> +            if (
> +                (!defined($res->{link_down}) || $res->{link_down} != 1)
> +                && $conf->{ipmanagehost}
> +                && defined($res->{ip6})
> +                && $res->{ip6} eq 'auto'
> +            ) {
> +                die "$opt: SLAAC is not supported with a custom entrypoint\n";
>              }
>          } elsif ($opt =~ m/^dev(\d+)$/) {
>              my $device = $class->parse_device($value);
> @@ -1575,9 +1576,11 @@ sub vmconfig_hotplug_pending {
>                  $cgroup->change_cpu_shares(undef);
>              } elsif ($opt =~ m/^net(\d)$/) {
>                  my $netid = $1;
> +                my $net = parse_lxc_network($conf->{$opt});
> +                PVE::LXC::kill_dhclients($vmid, $net->{name}) if $conf->{ipmanagehost};
> +
>                  PVE::Network::veth_delete("veth${vmid}i$netid");
>                  if ($have_sdn) {
> -                    my $net = PVE::LXC::Config->parse_lxc_network($conf->{$opt});
>                      print "delete ips from $opt\n";
>                      eval {
>                          PVE::Network::SDN::Vnets::del_ips_from_mac(
> -- 
> 2.47.2
> 
> 
> 
> _______________________________________________
> pve-devel mailing list
> pve-devel@lists.proxmox.com
> https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
> 
> 


_______________________________________________
pve-devel mailing list
pve-devel@lists.proxmox.com
https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel