[PATCH pve-network] sdn: push mapping changes from the ipam API to the dhcp backend

[Hannes Laimer <h.laimer@proxmox.com>]

Mapping edits through the API only wrote the IPAM record and the
cache, the dhcp backend was never told, so dnsmasq kept serving
stale reservations until a later guest start in the zone happened
to sweep them.

Push the MAC's current answer after each create, update and delete,
removing the old reservation first, since a re-add alone leaves a
stale address behind when only one of the MAC's two addresses was
deleted. The push is best effort, the record write stays
authoritative. Mapping removal was dispatched to the plugins but
implemented nowhere and never called, add the dnsmasq
implementation for it.

Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
---
 src/PVE/API2/Network/SDN/Ips.pm     | 18 ++++++++++++++++
 src/PVE/Network/SDN/Dhcp/Dnsmasq.pm | 32 ++++++++++++++++++++++++++++-
 src/PVE/Network/SDN/Dhcp/Plugin.pm  |  5 +++++
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/src/PVE/API2/Network/SDN/Ips.pm b/src/PVE/API2/Network/SDN/Ips.pm
index 5ff05e7..fc76c90 100644
--- a/src/PVE/API2/Network/SDN/Ips.pm
+++ b/src/PVE/API2/Network/SDN/Ips.pm
@@ -13,6 +13,17 @@ use PVE::RESTHandler;
 
 use base qw(PVE::RESTHandler);
 
+my sub update_dhcp_mapping {
+    my ($vnet, $mac) = @_;
+
+    eval {
+        my ($ip4, $ip6) = PVE::Network::SDN::Vnets::get_ips_from_mac($vnet, $mac);
+        PVE::Network::SDN::Dhcp::remove_mapping($vnet, $mac);
+        PVE::Network::SDN::Dhcp::add_mapping($vnet, $mac, $ip4, $ip6) if $ip4 || $ip6;
+    };
+    warn "could not update dhcp mapping for $mac: $@" if $@;
+}
+
 __PACKAGE__->register_method({
     name => 'ipdelete',
     path => '',
@@ -46,6 +57,8 @@ __PACKAGE__->register_method({
         eval { PVE::Network::SDN::Vnets::del_ip($vnet, $ip, '', $mac); };
         die "$@\n" if $@;
 
+        update_dhcp_mapping($vnet, $mac);
+
         return undef;
     },
 });
@@ -82,6 +95,8 @@ __PACKAGE__->register_method({
 
         PVE::Network::SDN::Vnets::add_ip($vnet, $ip, '', $mac, undef);
 
+        update_dhcp_mapping($vnet, $mac);
+
         return undef;
     },
 });
@@ -132,6 +147,9 @@ __PACKAGE__->register_method({
         }
 
         die "$error\n" if $error;
+
+        update_dhcp_mapping($vnet, $mac);
+
         return undef;
     },
 });
diff --git a/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm b/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm
index 477b700..4677330 100644
--- a/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm
+++ b/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm
@@ -6,7 +6,7 @@ use warnings;
 use base qw(PVE::Network::SDN::Dhcp::Plugin);
 
 use Net::IP qw(:PROC);
-use PVE::Tools qw(file_set_contents run_command lock_file);
+use PVE::Tools qw(file_get_contents file_set_contents run_command lock_file);
 
 use File::Copy;
 use Net::DBus;
@@ -136,6 +136,36 @@ sub add_ip_mapping {
     update_lease($dhcpid, $ip4, $mac);
 }
 
+sub del_ip_mapping {
+    my ($class, $dhcpid, $mac) = @_;
+
+    my $ethers_file = ethers_file($dhcpid);
+
+    my $reload = undef;
+
+    my $removeFn = sub {
+        my @lines = split(/\n/, file_get_contents($ethers_file));
+        my @remaining = grep {
+            my ($parsed_mac) = split(/,/, $_);
+            !defined($parsed_mac) || $parsed_mac ne $mac;
+        } @lines;
+
+        return if scalar(@remaining) == scalar(@lines);
+
+        file_set_contents($ethers_file, join("\n", @remaining) . "\n", 0644);
+        $reload = 1;
+    };
+
+    PVE::Tools::lock_file($ethers_file, 10, $removeFn);
+
+    if ($@) {
+        warn "Unable to remove $mac from the dnsmasq configuration: $@\n";
+        return;
+    }
+
+    systemctl_service('reload', "dnsmasq\@$dhcpid") if $reload;
+}
+
 sub configure_subnet {
     my ($class, $config, $dhcpid, $vnetid, $subnet_config) = @_;
 
diff --git a/src/PVE/Network/SDN/Dhcp/Plugin.pm b/src/PVE/Network/SDN/Dhcp/Plugin.pm
index b5d32fa..6cbb8a2 100644
--- a/src/PVE/Network/SDN/Dhcp/Plugin.pm
+++ b/src/PVE/Network/SDN/Dhcp/Plugin.pm
@@ -27,6 +27,11 @@ sub add_ip_mapping {
     die 'implement in sub class';
 }
 
+sub del_ip_mapping {
+    my ($class, $dhcpid, $mac) = @_;
+    die 'implement in sub class';
+}
+
 sub configure_range {
     my ($class, $config, $dhcpid, $vnetid, $subnet_config, $range_config) = @_;
     die 'implement in sub class';
-- 
2.47.3