dns: T5144: Restrict dualstack for dyndns2 protocol to dyn.com

ddclient implementation of dualstack for dyndns2 protocol is targeted
for dyn.com (dyndns.org) only. Dualstack won't work for other servers
supporting dyndns2 protocol (for example, dyn.dns.he.net).

1 files changed, 6 insertions, 3 deletions

diff --git a/src/conf_mode/dynamic_dns.py b/src/conf_mode/dynamic_dns.py
index 879086cc4..fe72a3180 100755
--- a/src/conf_mode/dynamic_dns.py
+++ b/src/conf_mode/dynamic_dns.py
@@ -93,9 +93,12 @@ def verify(dyndns):
                     if 'username' not in config:
                         raise ConfigError(f'"username" {error_msg}')
 
-                if (config['protocol'] not in dualstack_supported
-                        and config['ip_version'] == 'both'):
-                    raise ConfigError(f'"{config["protocol"]}" does not support IPv4 and IPv6 at the same time')
+                if config['ip_version'] == 'both':
+                    if config['protocol'] not in dualstack_supported:
+                        raise ConfigError(f'"{config["protocol"]}" does not support IPv4 and IPv6 at the same time')
+                    # dyndns2 protocol in ddclient honors dual stack only for dyn.com (dyndns.org)
+                    if config['protocol'] == 'dyndns2' and 'server' in config and config['server'] != 'members.dyndns.org':
+                        raise ConfigError(f'"{config["protocol"]}" for "{config["server"]}" does not support IPv4 and IPv6 at the same time')
 
     return None