dns: T7924: Fix dns-dynamic migration error when `service` path is missing

Handle absent `service dns dynamic address <iface> service` nodes
during 1-to-2 migration to prevent ConfigTreeError.

3 files changed, 124 insertions, 5 deletions

diff --git a/smoketest/configs/assert/dns-dynamic b/smoketest/configs/assert/dns-dynamic
new file mode 100644
index 000000000..f40563016
--- /dev/null
+++ b/smoketest/configs/assert/dns-dynamic
@@ -0,0 +1,33 @@
+set interfaces ethernet eth0 address 'dhcp'
+set interfaces ethernet eth1 address 'dhcp'
+set interfaces loopback lo
+set service dns dynamic name rfc2136-PDNS-eth0 address interface 'eth0'
+set service dns dynamic name rfc2136-PDNS-eth0 host-name 'sub.example.com'
+set service dns dynamic name rfc2136-PDNS-eth0 key '/config/auth/../config.boot'
+set service dns dynamic name rfc2136-PDNS-eth0 protocol 'nsupdate'
+set service dns dynamic name rfc2136-PDNS-eth0 server '192.168.101.15'
+set service dns dynamic name rfc2136-PDNS-eth0 zone 'example.com'
+set service dns dynamic name service-dyndns-eth1 address interface 'eth1'
+set service dns dynamic name service-dyndns-eth1 host-name 'my-dyndns-hostname'
+set service dns dynamic name service-dyndns-eth1 password 'my-password'
+set service dns dynamic name service-dyndns-eth1 protocol 'dyndns2'
+set service dns dynamic name service-dyndns-eth1 username 'my-login'
+set service ntp allow-client address '0.0.0.0/0'
+set service ntp allow-client address '::/0'
+set service ntp server time1.vyos.net
+set service ntp server time2.vyos.net
+set service ntp server time3.vyos.net
+set system config-management commit-revisions '100'
+set system conntrack modules ftp
+set system conntrack modules h323
+set system conntrack modules nfs
+set system conntrack modules pptp
+set system conntrack modules sip
+set system conntrack modules sqlnet
+set system conntrack modules tftp
+set system console device ttyS0 speed '115200'
+set system host-name 'vyos'
+set system login user vyos authentication encrypted-password '$6$YuG5oKoRYQnbnxk$P2eZNlIwXJP82JFyFrF2g4ZoOZr6zgLHK.SDJVoqWDGefKkRrJijUZODAVMLeWU.9EGM48YtG9MwfuewWoOGE.'
+set system login user vyos authentication plaintext-password ''
+set system syslog local facility all level 'info'
+set system syslog local facility local7 level 'debug'
diff --git a/smoketest/configs/dns-dynamic b/smoketest/configs/dns-dynamic
new file mode 100644
index 000000000..068c0eed7
--- /dev/null
+++ b/smoketest/configs/dns-dynamic
@@ -0,0 +1,84 @@
+interfaces {
+    ethernet eth0 {
+        address dhcp
+    }
+    ethernet eth1 {
+        address dhcp
+    }
+    loopback lo {
+    }
+}
+service {
+    dns {
+        dynamic {
+            interface eth0 {
+                rfc2136 PDNS {
+                    key /config/auth/../config.boot
+                    record sub.example.com
+                    server 192.168.101.15
+                    zone example.com
+                }
+            }
+            interface eth1 {
+                service dyndns {
+                    host-name my-dyndns-hostname
+                    login my-login
+                    password my-password
+                }
+            }
+        }
+    }
+}
+system {
+    config-management {
+        commit-revisions 100
+    }
+    conntrack {
+        modules {
+            ftp
+            h323
+            nfs
+            pptp
+            sip
+            sqlnet
+            tftp
+        }
+    }
+    console {
+        device ttyS0 {
+            speed 115200
+        }
+    }
+    host-name vyos
+    login {
+        user vyos {
+            authentication {
+                encrypted-password $6$YuG5oKoRYQnbnxk$P2eZNlIwXJP82JFyFrF2g4ZoOZr6zgLHK.SDJVoqWDGefKkRrJijUZODAVMLeWU.9EGM48YtG9MwfuewWoOGE.
+                plaintext-password ""
+            }
+        }
+    }
+    ntp {
+        server time1.vyos.net {
+        }
+        server time2.vyos.net {
+        }
+        server time3.vyos.net {
+        }
+    }
+    syslog {
+        global {
+            facility all {
+                level info
+            }
+            facility protocols {
+                level debug
+            }
+        }
+    }
+}
+
+
+// Warning: Do not remove the following line.
+// vyos-config-version: "broadcast-relay@1:cluster@1:config-management@1:conntrack@3:conntrack-sync@2:container@1:dhcp-relay@2:dhcp-server@6:dhcpv6-server@1:dns-forwarding@3:firewall@5:https@2:interfaces@23:ipoe-server@1:ipsec@5:isis@1:l2tp@3:lldp@1:mdns@1:nat@5:ntp@1:pppoe-server@5:pptp@2:qos@1:quagga@8:rpki@1:salt@1:snmp@2:ssh@2:sstp@3:system@21:vrrp@2:vyos-accel-ppp@2:wanloadbalance@3:webproxy@2:zone-policy@1"
+// Release version: 1.3.8
diff --git a/src/migration-scripts/dns-dynamic/1-to-2 b/src/migration-scripts/dns-dynamic/1-to-2
index 6398b902f..424d4fa85 100644
--- a/src/migration-scripts/dns-dynamic/1-to-2
+++ b/src/migration-scripts/dns-dynamic/1-to-2
@@ -51,8 +51,10 @@ def migrate(config: ConfigTree) -> None:
         # Migrate "service dns dynamic address <interface> service <service> protocol dnsexit"
         #      to "service dns dynamic address <interface> service <service> protocol dnsexit2"
         for address in config.list_nodes(address_path):
-            for svc_cfg in config.list_nodes(address_path + [address, 'service']):
-                if config.exists(address_path + [address, 'service', svc_cfg, 'protocol']):
-                    protocol = config.return_value(address_path + [address, 'service', svc_cfg, 'protocol'])
-                    if protocol == 'dnsexit':
-                        config.set(address_path + [address, 'service', svc_cfg, 'protocol'], 'dnsexit2')
+            service_path = address_path + [address, 'service']
+            if config.exists(service_path):
+                for svc_cfg in config.list_nodes(service_path):
+                    if config.exists(service_path + [svc_cfg, 'protocol']):
+                        protocol = config.return_value(service_path + [svc_cfg, 'protocol'])
+                        if protocol == 'dnsexit':
+                            config.set(service_path + [svc_cfg, 'protocol'], 'dnsexit2')