Re: [PATCH pve-network v3 07/17] sdn: dhcp: make the lease time configurable per subnet

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

Reviewed-by: Stefan Hanreich <s.hanreich@proxmox.com>
Tested-by: Stefan Hanreich <s.hanreich@proxmox.com>

On 10/20/26 10:00 AM, Hannes Laimer wrote:
> dnsmasq hands out infinite leases, so a guest asks for its address
> again only at its next reboot or network restart. A finite lease makes
> it renew within the lease time. An address changed in the IPAM goes to
> dnsmasq on the node the change is made on, so a guest there picks up
> the new address at its next renewal. Guests on other nodes get it only
> at their next start there.
> 
> A subnet without a lease time keeps infinite leases.
> 
> Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
> ---
>  src/PVE/Network/SDN/Dhcp/Dnsmasq.pm |  3 +-
>  src/PVE/Network/SDN/SubnetPlugin.pm | 11 +++++++
>  src/test/run_test_vnets_blackbox.pl | 51 +++++++++++++++++++++++++++++
>  3 files changed, 64 insertions(+), 1 deletion(-)
> 
> diff --git a/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm b/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm
> index 57ce1f73..c6c9ce1d 100644
> --- a/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm
> +++ b/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm
> @@ -200,7 +200,8 @@ sub configure_subnet {
>          $mask = join('.', unpack("C4", pack("N", $mask)));
>      }
>  
> -    push @{$config}, "dhcp-range=set:$tag,$network,static,$mask,infinite";
> +    my $lease = $subnet_config->{'dhcp-lease-time'} // 'infinite';
> +    push @{$config}, "dhcp-range=set:$tag,$network,static,$mask,$lease";
>  
>      my $option_string;
>      if (ip_is_ipv6($subnet_config->{network})) {
> diff --git a/src/PVE/Network/SDN/SubnetPlugin.pm b/src/PVE/Network/SDN/SubnetPlugin.pm
> index e2a0e50d..29edf7b6 100644
> --- a/src/PVE/Network/SDN/SubnetPlugin.pm
> +++ b/src/PVE/Network/SDN/SubnetPlugin.pm
> @@ -177,6 +177,16 @@ sub properties {
>              description => 'IP address for the DNS server',
>              optional => 1,
>          },
> +        'dhcp-lease-time' => {
> +            type => 'integer',
> +            minimum => 60,
> +            maximum => 4294967295,
> +            description =>
> +                'Lease time in seconds for DHCP answers. Without it dnsmasq hands out'
> +                . ' infinite leases, and it raises anything below two minutes to two'
> +                . ' minutes.',
> +            optional => 1,
> +        },
>      };
>  }
>  
> @@ -189,6 +199,7 @@ sub options {
>          dnszoneprefix => { optional => 1 },
>          'dhcp-range' => { optional => 1 },
>          'dhcp-dns-server' => { optional => 1 },
> +        'dhcp-lease-time' => { optional => 1 },
>      };
>  }
>  
> diff --git a/src/test/run_test_vnets_blackbox.pl b/src/test/run_test_vnets_blackbox.pl
> index 476e7f8d..dc54bba3 100755
> --- a/src/test/run_test_vnets_blackbox.pl
> +++ b/src/test/run_test_vnets_blackbox.pl
> @@ -334,6 +334,11 @@ sub create_subnet {
>      PVE::API2::Network::SDN::Subnets->create($params);
>  }
>  
> +sub update_subnet {
> +    my ($params) = @_;
> +    PVE::API2::Network::SDN::Subnets->update($params);
> +}
> +
>  sub get_ipam_entries {
>      return PVE::API2::Network::SDN::Ipams->ipamindex({ ipam => "pve" });
>  }
> @@ -1118,6 +1123,52 @@ sub test_dnsmasq_mapping_push {
>  
>  run_test(\&test_dnsmasq_mapping_push);
>  
> +sub test_dnsmasq_lease_time {
> +    my $test_name = (split(/::/, (caller(0))[3]))[-1];
> +    my $zoneid = "TESTZONE";
> +    my $vnetid = "testvnet";
> +
> +    # the subnet's lease time reaches the range, and infinite stays the default
> +    create_zone({
> +        type => "simple",
> +        dhcp => "dnsmasq",
> +        ipam => "pve",
> +        zone => $zoneid,
> +    });
> +    create_vnet({
> +        type => "vnet",
> +        zone => $zoneid,
> +        vnet => $vnetid,
> +    });
> +    create_subnet({
> +        type => "subnet",
> +        vnet => $vnetid,
> +        subnet => "10.0.0.0/24",
> +        gateway => "10.0.0.1",
> +        'dhcp-range' => ["start-address=10.0.0.100,end-address=10.0.0.200"],
> +    });
> +    my $range = sub {
> +        my $subnets = PVE::Network::SDN::Vnets::get_subnets($vnetid, 1);
> +        my $config = [];
> +        for my $id (sort keys %$subnets) {
> +            PVE::Network::SDN::Dhcp::Dnsmasq->configure_subnet(
> +                $config, $zoneid, $vnetid, $subnets->{$id},
> +            );
> +        }
> +        my ($line) = grep { m/^dhcp-range=/ } @$config;
> +        return $line;
> +    };
> +    like($range->(), qr/,infinite$/, "$test_name: no lease time means infinite leases");
> +    update_subnet({
> +        vnet => $vnetid,
> +        subnet => "$zoneid-10.0.0.0-24",
> +        'dhcp-lease-time' => 300,
> +    });
> +    like($range->(), qr/,300$/, "$test_name: the lease time reaches the range");
> +}
> +
> +run_test(\&test_dnsmasq_lease_time);
> +
>  sub test_ipam_cache_misses {
>      my $test_name = (split(/::/, (caller(0))[3]))[-1];
>      my $zoneid = "TESTZONE";