[pve-devel] [RFC pve-network 5/6] sdn: dhcp: add DHCP plugin for dnsmasq

[Stefan Hanreich <s.hanreich@proxmox.com>]

The plugin generates several dnsmasq configuration files from the SDN
configuration.

/etc/default/dnsmasq.<dhcp_id>
This file specifies the configuration directory for the dnsmasq
instance (/etc/dnsmasq.d/<dhcp_id>). It also sets the configuration
file to /dev/null so the default configuration from the package has
no influence on the dnsmasq configuration.

/etc/dnsmasq.d/<dhcp_id>/00-default.conf
The default configration does several things:
* disable DNS functionality.
* make dnsmasq listen only on the interfaces where it should provide
  DHCP (contrary to the default configuration, which listens on all
  interfaces). This is particularly important when running multiple
  instances of dnsmasq.
* Set the lease file to /var/lib/misc/dnsmasq.<dhcp_id>.leases

/etc/dnsmasq.d/<dhcp_id>/10-<subnet_id>.conf
This file contains the subnet specific settings, which usually
includes:
* DHCP range
* DNS server
* Default Gateway (for IPv4)

Currently regenerating and reloading dnsmasq is very sledgehammery. It
deletes all existing subnet configuration files and disables + stops
all currently running dnsmasq instances. Then it enables + starts all
dnsmasq instances that have been recreated. I intend to improve this
behaviour in the future either by getting access to the old
configuration or using systemd targets.

This plugin currently only works for simple Zones with subnets that
have a gateway configured, since I use the gateway as listening
address for dnsmasq.

Signed-off-by: Stefan Hanreich <s.hanreich@proxmox.com>
---
 debian/control                      |   1 +
 src/PVE/Network/SDN/Dhcp/Dnsmasq.pm | 115 ++++++++++++++++++++++++++++
 src/PVE/Network/SDN/Dhcp/Makefile   |   2 +-
 3 files changed, 117 insertions(+), 1 deletion(-)
 create mode 100644 src/PVE/Network/SDN/Dhcp/Dnsmasq.pm

diff --git a/debian/control b/debian/control
index 8b720c3..4424096 100644
--- a/debian/control
+++ b/debian/control
@@ -24,6 +24,7 @@ Depends: libpve-common-perl (>= 5.0-45),
          ${misc:Depends},
          ${perl:Depends},
 Recommends: frr-pythontools (>= 8.5.1~), ifupdown2
+Suggests: dnsmasq
 Description: Proxmox VE's SDN (Software Defined Network) stack
  This package contains the Software Defined Network (tech preview) for
  Proxmox VE.
diff --git a/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm b/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm
new file mode 100644
index 0000000..55d42e4
--- /dev/null
+++ b/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm
@@ -0,0 +1,115 @@
+package PVE::Network::SDN::Dhcp::Dnsmasq;
+
+use strict;
+use warnings;
+
+use base qw(PVE::Network::SDN::Dhcp::Plugin);
+
+use Net::IP qw(:PROC);
+use PVE::Tools qw(file_set_contents run_command);
+
+my $DNSMASQ_CONFIG_ROOT = '/etc/dnsmasq.d';
+my $DNSMASQ_DEFAULT_ROOT = '/etc/default';
+my $DNSMASQ_LEASE_ROOT = '/var/lib/misc';
+
+my $DEFAULT_LEASE_TIME = 86400;
+
+sub type {
+    return 'dnsmasq';
+}
+
+sub configure_subnet {
+    my ($class, $dhcp_config, $subnet_config, $range_config) = @_;
+
+    die "No gateway defined for subnet $subnet_config->{id}"
+	if !$subnet_config->{gateway};
+
+    my $tag = $subnet_config->{id};
+    my $lease_time = $subnet_config->{'lease-time'} || $dhcp_config->{'lease-time'} || $DEFAULT_LEASE_TIME;
+
+    my @dnsmasq_config = (
+	"listen-address=$subnet_config->{gateway}",
+    );
+
+    my $option_string;
+    if (ip_is_ipv6($subnet_config->{network})) {
+	$option_string = 'option6';
+
+	push @dnsmasq_config, "enable-ra";
+    } else {
+	$option_string = 'option';
+
+	push @dnsmasq_config, "dhcp-option=tag:$tag,$option_string:router,$subnet_config->{gateway}";
+    }
+
+
+
+    foreach my $dhcp_range (@$range_config) {
+	push @dnsmasq_config, "dhcp-range=set:$tag,$dhcp_range->{'start-address'},$dhcp_range->{'end-address'},${lease_time}s";
+
+	my $dns_server = $dhcp_range->{'dns-server'} || $subnet_config->{'dhcp-dns-server'} ;
+	push @dnsmasq_config, "dhcp-option=tag:$tag,$option_string:dns-server,$dns_server"
+	    if $dns_server;
+    }
+
+    PVE::Tools::file_set_contents(
+	"$DNSMASQ_CONFIG_ROOT/$dhcp_config->{id}/10-$subnet_config->{id}.conf",
+	join("\n", @dnsmasq_config)
+    );
+}
+
+sub before_configure {
+    my ($class, $dhcp_config) = @_;
+
+    my $config_directory = "$DNSMASQ_CONFIG_ROOT/$dhcp_config->{id}";
+
+    mkdir($config_directory, 755) if !-d $config_directory;
+
+    my $default_config = <<CFG;
+CONFIG_DIR=$config_directory,.dpkg-dist,.dpkg-old,.dpkg-new,.pve-new
+DNSMASQ_OPTS="--conf-file=/dev/null"
+CFG
+
+    PVE::Tools::file_set_contents(
+	"$DNSMASQ_DEFAULT_ROOT/dnsmasq.$dhcp_config->{id}",
+	$default_config
+    );
+
+    my $default_dnsmasq_config = <<CFG;
+except-interface=lo
+bind-dynamic
+no-resolv
+no-hosts
+dhcp-leasefile=$DNSMASQ_LEASE_ROOT/dnsmasq.$dhcp_config->{id}.leases
+CFG
+
+    PVE::Tools::file_set_contents(
+	"$config_directory/00-default.conf",
+	$default_dnsmasq_config
+    );
+
+    unlink glob "$config_directory/10-*.conf";
+}
+
+sub after_configure {
+    my ($class, $dhcp_config) = @_;
+
+    my $service_name = "dnsmasq\@$dhcp_config->{id}";
+
+    PVE::Tools::run_command(['systemctl', 'enable', $service_name]);
+    PVE::Tools::run_command(['systemctl', 'restart', $service_name]);
+}
+
+sub before_regenerate {
+    my ($class) = @_;
+
+    PVE::Tools::run_command(['systemctl', 'stop', "dnsmasq@*"]);
+    PVE::Tools::run_command(['systemctl', 'disable', 'dnsmasq@']);
+}
+
+sub after_regenerate {
+    my ($class) = @_;
+    # noop
+}
+
+1;
diff --git a/src/PVE/Network/SDN/Dhcp/Makefile b/src/PVE/Network/SDN/Dhcp/Makefile
index 1e9b6d3..6546513 100644
--- a/src/PVE/Network/SDN/Dhcp/Makefile
+++ b/src/PVE/Network/SDN/Dhcp/Makefile
@@ -1,4 +1,4 @@
-SOURCES=Plugin.pm
+SOURCES=Plugin.pm Dnsmasq.pm


 PERL5DIR=${DESTDIR}/usr/share/perl5
--
2.39.2