fix: RDAP ban prevention and DNS fallback

Problem: We are banned from Afilias (.info/.biz) and Google (.dev/.app)
RDAP servers due to too many requests, causing timeouts.

Solution:
1. Added RDAP_BLOCKED_TLDS list in domain_checker.py
2. Skip RDAP for blocked TLDs, use DNS+WHOIS instead
3. Updated drop_status_checker.py to skip blocked TLDs
4. Removed banned endpoints from RDAP_ENDPOINTS

TLDs now using DNS-only: .info, .biz, .org, .dev, .app, .xyz, .online, .com, .net
TLDs still using RDAP: .ch, .li, .de (working fine)

This prevents bans and timeouts while still providing availability checks.

backend/app/services/domain_checker.py

@@ -87,6 +87,20 @@ class DomainChecker:
         'ru', 'su', 'ua', 'by', 'kz',
     }
     
+    # TLDs where we are rate-limited/banned from RDAP
+    # Use DNS+WHOIS only for these (no RDAP calls!)
+    RDAP_BLOCKED_TLDS = {
+        'info',   # Afilias - banned, timeouts
+        'biz',    # Afilias - banned, timeouts
+        'org',    # PIR - might be blocked
+        'dev',    # Google - blocked
+        'app',    # Google - blocked
+        'xyz',    # CentralNic - slow/limited
+        'online', # CentralNic - slow/limited
+        'com',    # Verisign - heavy rate limits
+        'net',    # Verisign - heavy rate limits
+    }
+    
     def __init__(self):
         """Initialize the domain checker."""
         self._dns_resolver = dns.resolver.Resolver()
@@ -602,8 +616,10 @@ class DomainChecker:
             # If custom RDAP fails, fall through to DNS check
             logger.info(f"Custom RDAP failed for {domain}, using DNS fallback")
         
-        # Priority 2: Try standard RDAP via whodap
+        # Priority 2: Try standard RDAP via whodap (skip blocked TLDs!)
-        if tld not in self.WHOIS_ONLY_TLDS and tld not in self.CUSTOM_RDAP_ENDPOINTS:
+        if (tld not in self.WHOIS_ONLY_TLDS and 
+            tld not in self.CUSTOM_RDAP_ENDPOINTS and
+            tld not in self.RDAP_BLOCKED_TLDS):
             rdap_result = await self._check_rdap(domain)
             if rdap_result:
                 # Validate with DNS if RDAP says available
@@ -614,6 +630,30 @@ class DomainChecker:
                         rdap_result.is_available = False
                 return rdap_result
         
+        # For RDAP-blocked TLDs: Use DNS first, then WHOIS for details
+        if tld in self.RDAP_BLOCKED_TLDS:
+            logger.debug(f"Using DNS+WHOIS fallback for blocked TLD .{tld}: {domain}")
+            dns_available = await self._check_dns(domain)
+            
+            if dns_available:
+                # No DNS records = likely available, verify with WHOIS
+                whois_result = await self._check_whois(domain)
+                return whois_result
+            else:
+                # Has DNS records = taken, try to get details from WHOIS
+                try:
+                    whois_result = await self._check_whois(domain)
+                    whois_result.check_method = "dns+whois"
+                    return whois_result
+                except Exception:
+                    # WHOIS failed, return DNS-only result
+                    return DomainCheckResult(
+                        domain=domain,
+                        status=DomainStatus.TAKEN,
+                        is_available=False,
+                        check_method="dns",
+                    )
+        
         # Priority 3: Fall back to WHOIS (skip for TLDs that block it like .ch)
         if tld not in self.CUSTOM_RDAP_ENDPOINTS:
             whois_result = await self._check_whois(domain)

backend/app/services/drop_status_checker.py

@@ -16,24 +16,26 @@ from typing import Optional
 logger = logging.getLogger(__name__)
 
 # RDAP endpoints for different TLDs
+# ONLY include TLDs where RDAP is NOT blocked!
 RDAP_ENDPOINTS = {
-    # ccTLDs
+    # ccTLDs (these work reliably)
     'ch': 'https://rdap.nic.ch/domain/',
     'li': 'https://rdap.nic.ch/domain/',
     'de': 'https://rdap.denic.de/domain/',
-    # gTLDs via CentralNic
+    # gTLDs - DISABLED due to rate limits / bans:
-    'online': 'https://rdap.centralnic.com/online/domain/',
+    # 'online': 'https://rdap.centralnic.com/online/domain/',  # rate-limited
-    'xyz': 'https://rdap.centralnic.com/xyz/domain/',
+    # 'xyz': 'https://rdap.centralnic.com/xyz/domain/',        # rate-limited
-    'club': 'https://rdap.nic.club/domain/',
+    # 'club': 'https://rdap.nic.club/domain/',                 # unreliable
-    # gTLDs via Afilias/Donuts
+    # 'info': 'https://rdap.afilias.net/rdap/info/domain/',    # BANNED
-    'info': 'https://rdap.afilias.net/rdap/info/domain/',
+    # 'biz': 'https://rdap.afilias.net/rdap/biz/domain/',      # BANNED
-    'biz': 'https://rdap.afilias.net/rdap/biz/domain/',
+    # 'org': 'https://rdap.publicinterestregistry.org/rdap/org/domain/',  # blocked
-    'org': 'https://rdap.publicinterestregistry.org/rdap/org/domain/',
+    # 'dev': 'https://rdap.nic.google/domain/',                # BANNED
-    # Google TLDs
+    # 'app': 'https://rdap.nic.google/domain/',                # BANNED
-    'dev': 'https://rdap.nic.google/domain/',
-    'app': 'https://rdap.nic.google/domain/',
 }
 
+# TLDs where RDAP is blocked/banned - skip RDAP entirely
+RDAP_BLOCKED_TLDS = {'info', 'biz', 'org', 'dev', 'app', 'xyz', 'online', 'club', 'com', 'net'}
+
 
 @dataclass
 class DropStatus:
@@ -60,16 +62,27 @@ async def check_drop_status(domain: str) -> DropStatus:
     """
     tld = domain.split('.')[-1].lower()
     
-    endpoint = RDAP_ENDPOINTS.get(tld)
+    # Skip RDAP for blocked TLDs to avoid bans/timeouts
-    if not endpoint:
+    if tld in RDAP_BLOCKED_TLDS:
-        # Try generic lookup
+        logger.debug(f"Skipping RDAP for blocked TLD .{tld}: {domain}")
-        logger.warning(f"No RDAP endpoint for .{tld}, returning unknown")
         return DropStatus(
             domain=domain,
             status='unknown',
             rdap_status=[],
             can_register_now=False,
-            should_monitor=False,
+            should_monitor=True,  # Still worth monitoring via zone files
+            message=f"RDAP disabled for .{tld} (rate-limited)"
+        )
+    
+    endpoint = RDAP_ENDPOINTS.get(tld)
+    if not endpoint:
+        logger.debug(f"No RDAP endpoint for .{tld}, returning unknown")
+        return DropStatus(
+            domain=domain,
+            status='unknown',
+            rdap_status=[],
+            can_register_now=False,
+            should_monitor=True,
             message=f"No RDAP endpoint for .{tld}"
         )