Add support for option 'prefer-ipv6'

debian/config.json

@@ -7,5 +7,6 @@
     "timeout":300,
     "method":"aes-256-cfb",
     "fast_open": false,
-    "workers": 1
+    "workers": 1,
+    "prefer_ipv6": false
 }

shadowsocks/asyncdns.py

@@ -242,13 +242,13 @@ class DNSResponse(object):
         return '%s: %s' % (self.hostname, str(self.answers))
 
 
-STATUS_IPV4 = 0
-STATUS_IPV6 = 1
+STATUS_FIRST = 0
+STATUS_SECOND = 1
 
 
 class DNSResolver(object):
 
-    def __init__(self, server_list=None):
+    def __init__(self, server_list=None, prefer_ipv6=False):
         self._loop = None
         self._hosts = {}
         self._hostname_status = {}
@@ -261,6 +261,10 @@ class DNSResolver(object):
             self._parse_resolv()
         else:
             self._servers = server_list
+        if prefer_ipv6:
+            self._QTYPES = [QTYPE_AAAA, QTYPE_A]
+        else:
+            self._QTYPES = [QTYPE_A, QTYPE_AAAA]
         self._parse_hosts()
         # TODO monitor hosts change and reload hosts
         # TODO parse /etc/gai.conf and follow its rules
@@ -341,17 +345,18 @@ class DNSResolver(object):
                         answer[2] == QCLASS_IN:
                     ip = answer[0]
                     break
-            if not ip and self._hostname_status.get(hostname, STATUS_IPV6) \
-                    == STATUS_IPV4:
-                self._hostname_status[hostname] = STATUS_IPV6
-                self._send_req(hostname, QTYPE_AAAA)
+            if not ip and self._hostname_status.get(hostname, STATUS_SECOND) \
+                    == STATUS_FIRST:
+                self._hostname_status[hostname] = STATUS_SECOND
+                self._send_req(hostname, self._QTYPES[1])
             else:
                 if ip:
                     self._cache[hostname] = ip
                     self._call_callback(hostname, ip)
-                elif self._hostname_status.get(hostname, None) == STATUS_IPV6:
+                elif self._hostname_status.get(hostname, None) \
+                        == STATUS_SECOND:
                     for question in response.questions:
-                        if question[1] == QTYPE_AAAA:
+                        if question[1] == self._QTYPES[1]:
                             self._call_callback(hostname, None)
                             break
 
@@ -417,14 +422,14 @@ class DNSResolver(object):
                 return
             arr = self._hostname_to_cb.get(hostname, None)
             if not arr:
-                self._hostname_status[hostname] = STATUS_IPV4
-                self._send_req(hostname, QTYPE_A)
+                self._hostname_status[hostname] = STATUS_FIRST
+                self._send_req(hostname, self._QTYPES[0])
                 self._hostname_to_cb[hostname] = [callback]
                 self._cb_to_hostname[callback] = hostname
             else:
                 arr.append(callback)
                 # TODO send again only if waited too long
-                self._send_req(hostname, QTYPE_A)
+                self._send_req(hostname, self._QTYPES[0])
 
     def close(self):
         if self._sock:

shadowsocks/server.py

@@ -58,9 +58,10 @@ def main():
     udp_servers = []
 
     if 'dns_server' in config:  # allow override settings in resolv.conf
-        dns_resolver = asyncdns.DNSResolver(config['dns_server'])
+        dns_resolver = asyncdns.DNSResolver(config['dns_server'],
+                                            config['prefer_ipv6'])
     else:
-        dns_resolver = asyncdns.DNSResolver()
+        dns_resolver = asyncdns.DNSResolver(prefer_ipv6=config['prefer_ipv6'])
 
     port_password = config['port_password']
     del config['port_password']

shadowsocks/shell.py

@@ -137,7 +137,8 @@ def get_config(is_local):
     else:
         shortopts = 'hd:s:p:k:m:c:t:vqa'
         longopts = ['help', 'fast-open', 'pid-file=', 'log-file=', 'workers=',
-                    'forbidden-ip=', 'user=', 'manager-address=', 'version']
+                    'forbidden-ip=', 'user=', 'manager-address=', 'version',
+                    'prefer-ipv6']
     try:
         config_path = find_config()
         optlist, args = getopt.getopt(sys.argv[1:], shortopts, longopts)
@@ -207,6 +208,8 @@ def get_config(is_local):
             elif key == '-q':
                 v_count -= 1
                 config['verbose'] = v_count
+            elif key == '--prefer-ipv6':
+                config['prefer_ipv6'] = True
     except getopt.GetoptError as e:
         print(e, file=sys.stderr)
         print_help(is_local)
@@ -229,6 +232,7 @@ def get_config(is_local):
     config['local_address'] = to_str(config.get('local_address', '127.0.0.1'))
     config['local_port'] = config.get('local_port', 1080)
     config['one_time_auth'] = config.get('one_time_auth', False)
+    config['prefer_ipv6'] = config.get('prefer_ipv6', False)
     if is_local:
         if config.get('server', None) is None:
             logging.error('server addr not specified')
@@ -324,6 +328,7 @@ Proxy options:
   --workers WORKERS      number of workers, available on Unix/Linux
   --forbidden-ip IPLIST  comma seperated IP list forbidden to connect
   --manager-address ADDR optional server manager UDP address, see wiki
+  --prefer-ipv6          resolve ipv6 address first
 
 General options:
   -h, --help             show this help message and exit