don't dns resolve raw IP addresses

lib/network.py

@@ -32,12 +32,14 @@ import threading
 import socket
 import json
 import sys
+import ipaddress
 
 import dns
 import dns.resolver
 import socks
 
 from . import util
+from .util import print_error
 from . import bitcoin
 from .bitcoin import COIN
 from . import constants
@@ -452,27 +454,38 @@ class Network(util.DaemonThread):
                 # On Windows, socket.getaddrinfo takes a mutex, and might hold it for up to 10 seconds
                 # when dns-resolving. To speed it up drastically, we resolve dns ourselves, outside that lock.
                 # see #4421
-                def fast_getaddrinfo(host, *args, **kwargs):
+                socket.getaddrinfo = self._fast_getaddrinfo
-                    try:
-                        if str(host) not in ('localhost', 'localhost.',):
-                            answers = dns.resolver.query(host)
-                            addr = str(answers[0])
-                        else:
-                            addr = host
-                    except dns.exception.DNSException:
-                        # dns failed for some reason, e.g. dns.resolver.NXDOMAIN
-                        # this is normal. Simply report back failure:
-                        raise socket.gaierror(11001, 'getaddrinfo failed')
-                    except BaseException as e:
-                        # Possibly internal error in dnspython :( see #4483
-                        # Fall back to original socket.getaddrinfo to resolve dns.
-                        self.print_error('dnspython failed to resolve dns with error:', e)
-                        addr = host
-                    return socket._getaddrinfo(addr, *args, **kwargs)
-                socket.getaddrinfo = fast_getaddrinfo
             else:
                 socket.getaddrinfo = socket._getaddrinfo
 
+    @staticmethod
+    def _fast_getaddrinfo(host, *args, **kwargs):
+        def needs_dns_resolving(host2):
+            try:
+                ipaddress.ip_address(host2)
+                return False  # already valid IP
+            except ValueError:
+                pass  # not an IP
+            if str(host) in ('localhost', 'localhost.',):
+                return False
+            return True
+        try:
+            if needs_dns_resolving(host):
+                answers = dns.resolver.query(host)
+                addr = str(answers[0])
+            else:
+                addr = host
+        except dns.exception.DNSException:
+            # dns failed for some reason, e.g. dns.resolver.NXDOMAIN
+            # this is normal. Simply report back failure:
+            raise socket.gaierror(11001, 'getaddrinfo failed')
+        except BaseException as e:
+            # Possibly internal error in dnspython :( see #4483
+            # Fall back to original socket.getaddrinfo to resolve dns.
+            print_error('dnspython failed to resolve dns with error:', e)
+            addr = host
+        return socket._getaddrinfo(addr, *args, **kwargs)
+
     @with_interface_lock
     def start_network(self, protocol, proxy):
         assert not self.interface and not self.interfaces