[pve-devel] [PATCH container v3 09/13] manage DHCP for containers with custom entrypoint
Filip Schauer
f.schauer at proxmox.com
Wed Jul 9 14:34:26 CEST 2025
Containers that do not use the default `/sbin/init` entrypoint may lack
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 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.
* 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
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