Merge pull request #4486 from SomberNight/getaddrinfo_take2

socket.getaddrinfo on win32: do our own dns resolution

lib/network.py

@@ -31,9 +31,15 @@ from collections import defaultdict
 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
@@ -444,7 +450,41 @@ class Network(util.DaemonThread):
             socket.getaddrinfo = lambda *args: [(socket.AF_INET, socket.SOCK_STREAM, 6, '', (args[0], args[1]))]
         else:
             socket.socket = socket._socketobject
-            socket.getaddrinfo = socket._getaddrinfo
+            if sys.platform == 'win32':
+                # 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
+                socket.getaddrinfo = self._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):