Add support for IPv6

It will now listen on an IPv6 socket if possible or fall back to IPv4
if that doesn't work. It will no longer filter out all IPv6 addresses
and instead it will only filter out those that point to the local
network.

It looks like the DNS bootstrapping should just automatically work
because getaddrinfo already returns IPv6 addresses from the AAAA
record.

In order to convert from the ASCII representation of IPv6 addresses
and back we need inet_ntop and inet_pton. Python 2 doesn't currently
provide these for Windows so instead this patch provides a hot patch
to the socket module which wraps WSAStringToAddress and
WSAAddressToString using ctypes.

src/bitmessagemain.py

@@ -13,6 +13,9 @@ import signal  # Used to capture a Ctrl-C keypress so that Bitmessage can shutdo
 # The next 3 are used for the API
 import singleton
 import os
+import socket
+import ctypes
+from struct import pack
 
 from SimpleXMLRPCServer import SimpleXMLRPCServer
 from api import MySimpleXMLRPCRequestHandler
@@ -71,6 +74,56 @@ def connectToStream(streamNumber):
         a.setup(streamNumber, selfInitiatedConnections)
         a.start()
 
+def _fixWinsock():
+    if not ('win32' in sys.platform) and not ('win64' in sys.platform):
+        return
+
+    # Python 2 on Windows doesn't define a wrapper for
+    # socket.inet_ntop but we can make one ourselves using ctypes
+    if not hasattr(socket, 'inet_ntop'):
+        addressToString = ctypes.windll.ws2_32.WSAAddressToStringA
+        def inet_ntop(family, host):
+            if family == socket.AF_INET:
+                if len(host) != 4:
+                    raise ValueError("invalid IPv4 host")
+                host = pack("hH4s8s", socket.AF_INET, 0, host, "\0" * 8)
+            elif family == socket.AF_INET6:
+                if len(host) != 16:
+                    raise ValueError("invalid IPv6 host")
+                host = pack("hHL16sL", socket.AF_INET6, 0, 0, host, 0)
+            else:
+                raise ValueError("invalid address family")
+            buf = "\0" * 64
+            lengthBuf = pack("I", len(buf))
+            addressToString(host, len(host), None, buf, lengthBuf)
+            return buf[0:buf.index("\0")]
+        socket.inet_ntop = inet_ntop
+
+    # Same for inet_pton
+    if not hasattr(socket, 'inet_pton'):
+        stringToAddress = ctypes.windll.ws2_32.WSAStringToAddressA
+        def inet_pton(family, host):
+            buf = "\0" * 28
+            lengthBuf = pack("I", len(buf))
+            if stringToAddress(str(host),
+                               int(family),
+                               None,
+                               buf,
+                               lengthBuf) != 0:
+                raise socket.error("illegal IP address passed to inet_pton")
+            if family == socket.AF_INET:
+                return buf[4:8]
+            elif family == socket.AF_INET6:
+                return buf[8:24]
+            else:
+                raise ValueError("invalid address family")
+        socket.inet_pton = inet_pton
+
+    # These sockopts are needed on for IPv6 support
+    if not hasattr(socket, 'IPPROTO_IPV6'):
+        socket.IPPROTO_IPV6 = 41
+    if not hasattr(socket, 'IPV6_V6ONLY'):
+        socket.IPV6_V6ONLY = 27
 
 # This thread, of which there is only one, runs the API.
 class singleAPI(threading.Thread):
@@ -95,6 +148,8 @@ if shared.useVeryEasyProofOfWorkForTesting:
 
 class Main:
     def start(self, daemon=False):
+        _fixWinsock()
+
         shared.daemon = daemon
         # is the application already running?  If yes then exit.
         thisapp = singleton.singleinstance()

src/class_outgoingSynSender.py

@@ -55,7 +55,11 @@ class outgoingSynSender(threading.Thread):
             shared.alreadyAttemptedConnectionsListLock.release()
             timeNodeLastSeen = shared.knownNodes[
                 self.streamNumber][peer]
-            sock = socks.socksocket(socket.AF_INET, socket.SOCK_STREAM)
+            if peer.host.find(':') == -1:
+                address_family = socket.AF_INET
+            else:
+                address_family = socket.AF_INET6
+            sock = socks.socksocket(address_family, socket.SOCK_STREAM)
             # This option apparently avoids the TIME_WAIT state so that we
             # can rebind faster
             sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

src/class_receiveDataThread.py

@@ -532,6 +532,32 @@ class receiveDataThread(threading.Thread):
 
         shared.broadcastToSendDataQueues((self.streamNumber, 'advertiseobject', hash))
     """
+
+    def _checkIPv4Address(self, host, hostFromAddrMessage):
+        # print 'hostFromAddrMessage', hostFromAddrMessage
+        if host[0] == '\x7F':
+            print 'Ignoring IP address in loopback range:', hostFromAddrMessage
+            return False
+        if host[0] == '\x0A':
+            print 'Ignoring IP address in private range:', hostFromAddrMessage
+            return False
+        if host[0:2] == '\xC0A8':
+            print 'Ignoring IP address in private range:', hostFromAddrMessage
+            return False
+        return True
+
+    def _checkIPv6Address(self, host, hostFromAddrMessage):
+        if host == ('\x00' * 15) + '\x01':
+            print 'Ignoring loopback address:', hostFromAddrMessage
+            return False
+        if host[0] == '\xFE' and (ord(host[1]) & 0xc0) == 0x80:
+            print 'Ignoring local address:', hostFromAddrMessage
+            return False
+        if (ord(host[0]) & 0xfe) == 0xfc:
+            print 'Ignoring unique local address:', hostFromAddrMessage
+            return False
+        return True
+
     # We have received an addr message.
     def recaddr(self, data):
         #listOfAddressDetailsToBroadcastToPeers = []
@@ -551,14 +577,11 @@ class receiveDataThread(threading.Thread):
 
         for i in range(0, numberOfAddressesIncluded):
             try:
-                if data[20 + lengthOfNumberOfAddresses + (38 * i):32 + lengthOfNumberOfAddresses + (38 * i)] != '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF':
-                    with shared.printLock:
-                       print 'Skipping IPv6 address.', repr(data[20 + lengthOfNumberOfAddresses + (38 * i):32 + lengthOfNumberOfAddresses + (38 * i)])
-                    continue
+                fullHost = data[20 + lengthOfNumberOfAddresses + (38 * i):36 + lengthOfNumberOfAddresses + (38 * i)]
             except Exception as err:
                 with shared.printLock:
                    sys.stderr.write(
-                       'ERROR TRYING TO UNPACK recaddr (to test for an IPv6 address). Message: %s\n' % str(err))
+                       'ERROR TRYING TO UNPACK recaddr (recaddrHost). Message: %s\n' % str(err))
                 break  # giving up on unpacking any more. We should still be connected however.
 
             try:
@@ -592,18 +615,15 @@ class receiveDataThread(threading.Thread):
                 break  # giving up on unpacking any more. We should still be connected however.
             # print 'Within recaddr(): IP', recaddrIP, ', Port',
             # recaddrPort, ', i', i
-            hostFromAddrMessage = socket.inet_ntoa(data[
-                                                   32 + lengthOfNumberOfAddresses + (38 * i):36 + lengthOfNumberOfAddresses + (38 * i)])
-            # print 'hostFromAddrMessage', hostFromAddrMessage
-            if data[32 + lengthOfNumberOfAddresses + (38 * i)] == '\x7F':
-                print 'Ignoring IP address in loopback range:', hostFromAddrMessage
-                continue
-            if data[32 + lengthOfNumberOfAddresses + (38 * i)] == '\x0A':
-                print 'Ignoring IP address in private range:', hostFromAddrMessage
-                continue
-            if data[32 + lengthOfNumberOfAddresses + (38 * i):34 + lengthOfNumberOfAddresses + (38 * i)] == '\xC0A8':
-                print 'Ignoring IP address in private range:', hostFromAddrMessage
-                continue
+            if fullHost[0:12] == '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF':
+                ipv4Host = fullHost[12:]
+                hostFromAddrMessage = socket.inet_ntop(socket.AF_INET, ipv4Host)
+                if not self._checkIPv4Address(ipv4Host, hostFromAddrMessage):
+                    continue
+            else:
+                hostFromAddrMessage = socket.inet_ntop(socket.AF_INET6, fullHost)
+                if not self._checkIPv6Address(fullHost, hostFromAddrMessage):
+                    continue
             timeSomeoneElseReceivedMessageFromThisNode, = unpack('>Q', data[lengthOfNumberOfAddresses + (
                 38 * i):8 + lengthOfNumberOfAddresses + (38 * i)])  # This is the 'time' value in the received addr message. 64-bit.
             if recaddrStream not in shared.knownNodes:  # knownNodes is a dictionary of dictionaries with one outer dictionary for each stream. If the outer stream dictionary doesn't exist yet then we must make it.
@@ -688,8 +708,7 @@ class receiveDataThread(threading.Thread):
                 payload += pack('>I', self.streamNumber)
                 payload += pack(
                     '>q', 1)  # service bit flags offered by this node
-                payload += '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF' + \
-                    socket.inet_aton(HOST)
+                payload += shared.encodeHost(HOST)
                 payload += pack('>H', PORT)  # remote port
         for (HOST, PORT), value in addrsInChildStreamLeft.items():
             timeLastReceivedMessageFromThisNode = value
@@ -700,8 +719,7 @@ class receiveDataThread(threading.Thread):
                 payload += pack('>I', self.streamNumber * 2)
                 payload += pack(
                     '>q', 1)  # service bit flags offered by this node
-                payload += '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF' + \
-                    socket.inet_aton(HOST)
+                payload += shared.encodeHost(HOST)
                 payload += pack('>H', PORT)  # remote port
         for (HOST, PORT), value in addrsInChildStreamRight.items():
             timeLastReceivedMessageFromThisNode = value
@@ -712,8 +730,7 @@ class receiveDataThread(threading.Thread):
                 payload += pack('>I', (self.streamNumber * 2) + 1)
                 payload += pack(
                     '>q', 1)  # service bit flags offered by this node
-                payload += '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF' + \
-                    socket.inet_aton(HOST)
+                payload += shared.encodeHost(HOST)
                 payload += pack('>H', PORT)  # remote port
 
         payload = encodeVarint(numberOfAddressesInAddrMessage) + payload

src/class_sendDataThread.py

@@ -113,8 +113,7 @@ class sendDataThread(threading.Thread):
                         payload += pack('>I', streamNumber)
                         payload += pack(
                             '>q', services)  # service bit flags offered by this node
-                        payload += '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF' + \
-                            socket.inet_aton(host)
+                        payload += shared.encodeHost(host)
                         payload += pack('>H', port)
 
                     payload = encodeVarint(numberOfAddressesInAddrMessage) + payload

src/class_singleListener.py

@@ -4,6 +4,8 @@ import socket
 from class_sendDataThread import *
 from class_receiveDataThread import *
 import helper_bootstrap
+import errno
+import re
 
 # Only one singleListener thread will ever exist. It creates the
 # receiveDataThread and sendDataThread for each incoming connection. Note
@@ -21,6 +23,21 @@ class singleListener(threading.Thread):
     def setup(self, selfInitiatedConnections):
         self.selfInitiatedConnections = selfInitiatedConnections
 
+    def _createListenSocket(self, family):
+        HOST = ''  # Symbolic name meaning all available interfaces
+        PORT = shared.config.getint('bitmessagesettings', 'port')
+        sock = socket.socket(family, socket.SOCK_STREAM)
+        if family == socket.AF_INET6:
+            # Make sure we can accept both IPv4 and IPv6 connections.
+            # This is the default on everything apart from Windows
+            sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)
+        # This option apparently avoids the TIME_WAIT state so that we can
+        # rebind faster
+        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        sock.bind((HOST, PORT))
+        sock.listen(2)
+        return sock
+
     def run(self):
         while shared.safeConfigGetBoolean('bitmessagesettings', 'dontconnect'):
             time.sleep(1)
@@ -35,14 +52,22 @@ class singleListener(threading.Thread):
         with shared.printLock:
             print 'Listening for incoming connections.'
 
-        HOST = ''  # Symbolic name meaning all available interfaces
-        PORT = shared.config.getint('bitmessagesettings', 'port')
-        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        # This option apparently avoids the TIME_WAIT state so that we can
-        # rebind faster
-        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-        sock.bind((HOST, PORT))
-        sock.listen(2)
+        # First try listening on an IPv6 socket. This should also be
+        # able to accept connections on IPv4. If that's not available
+        # we'll fall back to IPv4-only.
+        try:
+            sock = self._createListenSocket(socket.AF_INET6)
+        except socket.error, e:
+            if (isinstance(e.args, tuple) and
+                e.args[0] in (errno.EAFNOSUPPORT,
+                              errno.EPFNOSUPPORT,
+                              errno.ENOPROTOOPT)):
+                sock = self._createListenSocket(socket.AF_INET)
+            else:
+                raise
+
+        # regexp to match an IPv4-mapped IPv6 address
+        mappedAddressRegexp = re.compile(r'^::ffff:([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+)$')
 
         while True:
             # We typically don't want to accept incoming connections if the user is using a
@@ -56,18 +81,29 @@ class singleListener(threading.Thread):
                     print 'We are connected to too many people. Not accepting further incoming connections for ten seconds.'
 
                 time.sleep(10)
-            a, (HOST, PORT) = sock.accept()
 
-            # The following code will, unfortunately, block an incoming
-            # connection if someone else on the same LAN is already connected
-            # because the two computers will share the same external IP. This
-            # is here to prevent connection flooding.
-            while HOST in shared.connectedHostsList:
-                with shared.printLock:
-                    print 'We are already connected to', HOST + '. Ignoring connection.'
+            while True:
+                a, sockaddr = sock.accept()
+                (HOST, PORT) = sockaddr[0:2]
+
+                # If the address is an IPv4-mapped IPv6 address then
+                # convert it to just the IPv4 representation
+                md = mappedAddressRegexp.match(HOST)
+                if md != None:
+                    HOST = md.group(1)
+
+                # The following code will, unfortunately, block an
+                # incoming connection if someone else on the same LAN
+                # is already connected because the two computers will
+                # share the same external IP. This is here to prevent
+                # connection flooding.
+                if HOST in shared.connectedHostsList:
+                    a.close()
+                    with shared.printLock:
+                        print 'We are already connected to', HOST + '. Ignoring connection.'
+                else:
+                    break
 
-                a.close()
-                a, (HOST, PORT) = sock.accept()
             someObjectsOfWhichThisRemoteNodeIsAlreadyAware = {} # This is not necessairly a complete list; we clear it from time to time to save memory.
             sendDataThreadQueue = Queue.Queue() # Used to submit information to the send data thread for this connection.
             a.settimeout(20)

src/shared.py

@@ -96,6 +96,13 @@ def isInSqlInventory(hash):
     queryreturn = sqlQuery('''select hash from inventory where hash=?''', hash)
     return queryreturn != []
 
+def encodeHost(host):
+    if host.find(':') == -1:
+        return '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF' + \
+            socket.inet_aton(host)
+    else:
+        return socket.inet_pton(socket.AF_INET6, host)
+
 def assembleVersionMessage(remoteHost, remotePort, myStreamNumber):
     payload = ''
     payload += pack('>L', 2)  # protocol version.
@@ -104,8 +111,7 @@ def assembleVersionMessage(remoteHost, remotePort, myStreamNumber):
 
     payload += pack(
         '>q', 1)  # boolservices of remote connection; ignored by the remote host.
-    payload += '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF' + \
-        socket.inet_aton(remoteHost)
+    payload += encodeHost(remoteHost)
     payload += pack('>H', remotePort)  # remote IPv6 and port
 
     payload += pack('>q', 1)  # bitflags of the services I offer.