fix: ensure DNS zone changes take effect immediately on startup

Three related issues prevented CoreDNS from serving updated zone records:

1. The `file` plugin blocks in generate_corefile() lacked a `reload`
   option, so CoreDNS never re-read zone files after they were written.
   Added `reload 30s` so zone file changes are picked up within 30s.

2. _reload_dns_service() sent SIGHUP via `docker exec ... kill -HUP 1`,
   which doesn't trigger zone reloads. Changed to SIGUSR1 via
   `docker kill --signal=SIGUSR1` (same as firewall_manager.reload_coredns).

3. _bootstrap_dns() wrote the zone file but never regenerated the
   Corefile. CoreDNS's reload plugin only fires when the Corefile
   changes, so zone records from startup were invisible until the next
   peer modification triggered apply_all_dns_rules(). Now _bootstrap_dns()
   always calls apply_all_dns_rules() after the zone write.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/app.py

@@ -416,6 +416,11 @@ def _bootstrap_dns():
                 caddy_ip = ip_utils.get_service_ips(ip_range).get('caddy', '172.20.0.2')
                 network_manager.update_split_horizon_zone(
                     effective_domain, caddy_ip, primary_domain=domain)
+        # Regenerate the Corefile so any new zone blocks or reload options take
+        # effect immediately without waiting for the next peer modification.
+        firewall_manager.apply_all_dns_rules(
+            peer_registry.list_peers(), COREFILE_PATH, domain,
+            cell_links=cell_link_manager.list_connections())
     except Exception as e:
         logger.warning(f"DNS bootstrap failed (non-fatal): {e}")
 

api/firewall_manager.py

@@ -739,7 +739,7 @@ def generate_corefile(peers: List[Dict[str, Any]], corefile_path: str = COREFILE
 
         acl_block = _build_acl_block(blocked, domain)
 
-        primary_zone_block = f'{domain} {{\n    file /data/{domain}.zone\n    log\n'
+        primary_zone_block = f'{domain} {{\n    file /data/{domain}.zone reload 30s\n    log\n'
         if acl_block:
             primary_zone_block += acl_block + '\n'
         primary_zone_block += '}\n'
@@ -760,7 +760,7 @@ def generate_corefile(peers: List[Dict[str, Any]], corefile_path: str = COREFILE
             for sz in split_horizon_zones:
                 corefile += (
                     f'\n{sz} {{\n'
-                    f'    file /data/{sz}.zone\n'
+                    f'    file /data/{sz}.zone reload 30s\n'
                     f'    log\n'
                     f'}}\n'
                 )

api/network_manager.py

@@ -453,9 +453,9 @@ class NetworkManager(BaseServiceManager):
             return {'running': False, 'stats': {}}
     
     def _reload_dns_service(self):
-        """Reload DNS service"""
+        """Send SIGUSR1 to CoreDNS so the reload plugin picks up zone file changes."""
         try:
-            subprocess.run(['docker', 'exec', 'cell-dns', 'kill', '-HUP', '1'],
+            subprocess.run(['docker', 'kill', '--signal=SIGUSR1', 'cell-dns'],
                            capture_output=True, timeout=10)
         except Exception as e:
             logger.error(f"Failed to reload DNS service: {e}")