[Python-Dev] IPv6 and Windows

Martin v. Loewis martin@loewis.home.cs.tu-berlin.de
Sun, 24 Jun 2001 23:56:48 +0200

> Why ? Why can't those parts be 'if it exists'-ed out ? We do it for SSL
> support. I'm only comfortable with the IPv6 patch if it's optional, or can
> at least be disabled. I haven't looked at the patch, but why is getaddrinfo
> absolutely necessary, if the code works without it now, too ?

getaddrinfo offers protocol-independent address lookup. It is
necessary to use that API to support AF_INET and AF_INET6
transparently in application code. itojun proposes to change a number
of standard library modules. Please have a look at the actual patch
for details; the typical change will look like this (for httplib)

diff -u -r1.35 httplib.py
--- Lib/httplib.py	2001/06/01 16:25:38	1.35
+++ Lib/httplib.py	2001/06/24 04:41:48
@@ -357,10 +357,22 @@
     def connect(self):
         """Connect to the host and port specified in __init__."""
-        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        if self.debuglevel > 0:
-            print "connect: (%s, %s)" % (self.host, self.port)
-        self.sock.connect((self.host, self.port))
+ 	for res in socket.getaddrinfo(self.host, self.port, 0, socket.SOCK_STREAM):
+ 	    af, socktype, proto, canonname, sa = res
+ 	    try:
+ 		self.sock = socket.socket(af, socktype, proto)
+		if self.debuglevel > 0:
+		    print "connect: (%s, %s)" % (self.host, self.port)
+		self.sock.connect(sa)
+	    except socket.error, msg:
+		if self.debuglevel > 0:
+		    print 'connect fail:', (self.host, self.port)
+		self.sock.close()
+		self.sock = None
+		continue
+	    break
+	if not self.sock:
+	    raise socket.error, msg
     def close(self):
         """Close the connection to the HTTP server."""

As you can see, the modified code can simultaneously access both IPv4
and IPv6 hosts, and will pick whatever it can connect to best. Without
getaddrinfo, httplib would continue to support IPv4 hosts only.

The IPv6 support itself is absolutely optional. If it is not
available, getaddrinfo will never return IPv6 addresses, or propose
AF_INET6 as the address family.

> What about the zillion other 'obscure' ports ? OS/2 ? Palm ? MacOS 9 ;) If
> this patch can't be zero-impact-if-necessary, I'm a firm -1 on it. But I
> don't think it can't, it just takes more work.

Depends on what zero-impact-if-necessary means to you. The patch, as
it stands, can be fixed to compile on all systems that are currently
supported. It cannot be fixed to be taken completely out (unless you
literally do that: take it out).

I don't plan to fight for it too much. Please have a look at the code
itself, and try to cooperate on integrating it. Don't reject it
outright without having even looked at it.

If I get strong rejections from everybody, I'll just withdraw it and
feel sorry for the time I've already spent with it.