Fwd: "International Domain Names" support in KDE

Thiago Macieira thiagom at wanadoo.fr
Thu Jan 23 12:09:15 GMT 2003

Hash: SHA1

Dirk Mueller wrote:
>Thats flawed. Why does it do an IPv6 lookup? I have not a single network
>device that supports IPv6. even if it would manage to get an ipv6 address,
>there is no possible way to contact the ipv6 server.
>Why do we significantly slow down the dns resolution by wasting time on
>looking up ipv6 if the system cannot handle it ?

That's because the lower-level API we use can either handle one or all address 
families. We can't tell it to use just some of them.

And, actually, that happens in my system only, which has an IPv6 stack. Code 
to determine if an IPv6 stack is present in KDE for some time and is enabled 
by default. If one isn't found, the IPv6 lookup is disabled and an IPv4-only 
is done. The side-effect is that we don't benefit from other kinds of sockets 
that the getaddrinfo(3) function could return.

Still, I've done some more research into the problem, you still can't browse 
to that site because of something gone bizarre inside glibc. An strace and 
tcpdump reveals it sends the proper DNS query and receives a valid reply, but 
returns to the caller a non-recoverable error. It should be noted that the 
DNS query contains a domain-name that is not 7-bit clean, which is irregular 
by the standards. That might be the cause of glibc's rejecting it.

Finally, while writing the new resolver code, I've taken into consideration 
the fact that an IPv6 lookup could slow down the process. So, instead of 
doing a serial operation IPv6-then-IPv4, I'm coding it to do both lookups in 
parallel, with IPv4 being sent first to avoid nasty problems as those 
reported in bugs #30001 (I think) and similar. Of course, the IPv6 lookup 
will be withheld if no stack is present (*).

(*) note the code to detect the stack has a nasty side effect of activating 
such a stack that was not present, in certain configurations.

- -- 
  Thiago Macieira - UFOT Registry number: 1001
 thiagom at mail.com
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