[PATCH qemu-server v4 10/13] network: sdn: push the DHCP mappings of a guest when it resumes

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

A mapping edit and a migration of the guest exclude each other, but
an edit through a node not yet upgraded takes no lock and writes no
reservation, so it can land while the guest is migrated. Every resume
now pushes the mapping of each NIC of the guest on the local node
before the guest continues, and the last step of a live migration
resumes the target after the config moved, so the target serves what
the cache vouches for. The push reads the cache only and asks the
IPAM for nothing, so the paused guest waits on no request.

Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
---
 src/PVE/QemuServer/Network.pm  | 17 +++++++++++++++++
 src/PVE/QemuServer/RunState.pm |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/src/PVE/QemuServer/Network.pm b/src/PVE/QemuServer/Network.pm
index b4893c015646..b063f5b75b36 100644
--- a/src/PVE/QemuServer/Network.pm
+++ b/src/PVE/QemuServer/Network.pm
@@ -272,6 +272,23 @@ sub add_random_macs {
     }
 }
 
+# every resume pushes the current mapping of each NIC, so the target of a
+# live migration, resumed after the config moved, holds what the cache
+# vouches for. The push takes it from the cache and asks the IPAM for
+# nothing, so the paused guest waits on no request
+sub add_nets_dhcp_mapping {
+    my ($conf) = @_;
+
+    for my $opt (keys %$conf) {
+        next if $opt !~ m/^net\d+$/;
+        my $net = parse_net($conf->{$opt}, 1) or next;
+        next if !$net->{bridge} || !$net->{macaddr};
+        # a resume does not fail on its DHCP backend
+        eval { PVE::Network::SDN::Dhcp::update_mapping($net->{bridge}, $net->{macaddr}, 1) };
+        warn $@ if $@;
+    }
+}
+
 sub add_nets_bridge_fdb {
     my ($conf, $vmid) = @_;
 
diff --git a/src/PVE/QemuServer/RunState.pm b/src/PVE/QemuServer/RunState.pm
index 889ddd28287b..828d79159e90 100644
--- a/src/PVE/QemuServer/RunState.pm
+++ b/src/PVE/QemuServer/RunState.pm
@@ -181,6 +181,8 @@ sub vm_resume($vmid, $skiplock = undef, $nocheck = undef) {
 
             PVE::QemuServer::Network::add_nets_bridge_fdb($conf, $vmid)
                 if $resume_cmd eq 'cont';
+            PVE::QemuServer::Network::add_nets_dhcp_mapping($conf)
+                if $resume_cmd eq 'cont';
 
             mon_cmd($vmid, $resume_cmd);
         },
-- 
2.47.3