I've discovered that since glibc 2.3.2, getaddrinfo(3) supports a useful flag called AI_ADDRCONFIG. It turns off AAAA lookups if the machine isn't configured for IPv6 (and similarly for IPv4, theoretically). This is especially important when behind gateways whose DNS forwarder silently filter AAAA requests. Without AI_ADDRCONFIG, every DNS request has to wait for 4 AAAA request timeouts before it even attempts an A request.
Passing hints=NULL to getaddrinfo (the C function) means hints->flags = AI_V4MAPPED | AI_ADDRCONFIG. I.e., not the same as hints->hints->flags = 0. (Don't ask me why the default isn't 0, I don't like this API either. It means if you wish to specify only some hint parameters you have to carefully get the flags right.) Python's socketmodule.c, especially socket_getaddrinfo, uses 0 as the default flags. So AI_ADDRCONFIG is turned off by default. I propose: 1) mimic glibc default behavior, i.e. if flags is unspecified or None, treat it as the default value of AI_V4MAPPED | AI_ADDRCONFIG). Alternatively: 2) add these flags to callers of socket.getaddrinfo in various standard libs, e.g. httplib. (AI_V4MAPPED isn't as important since it only applies if you explicitly choose AF_INET6, a conscious decision.) Karl -- http://mail.python.org/mailman/listinfo/python-list
