tech-net archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: lib/42405: libc: getaddrinfo() should perform T_A lookups before T_AAAA lookups, was: Resolver problems

Hi, all--

Lots of people make decisions about software based upon personal preference; if 
you like your bikeshed painted red, or blue, or any other color, that's fine, 
and good software ought to be adjustable to suit those preferences.  However, I 
see quite a difference between making a decision based upon opinion and one 
based upon engineering principles such as obtaining relevant data, looking at 
the actual numbers, and making supportable estimates & predictions for future 

I hope the signal to noise ratio would improve if people choose to concentrate 
a bit more about real-world data, a bit more about writing actual code, and a 
bit less about their own personal opinions.  :-)

On Dec 4, 2009, at 7:19 AM, Greg Troxel wrote:
> Matthias Scheler <> writes:
>> No, the problem is caused by a router whose builtin caching nameserver
>> sends broken replies if NetBSD's libc queries for AAAA records. The broken
>> answer gets ignored and NetBSD's libc waits 15(?) seconds before trying
>> to query for A records.
> I see.  Well, perhaps some kind of "don't do AAAA lookups" runtime
> config would help such people.  Or a switch to accept replies from the
> wrong port.
> I wonder how many people are suffering from this - it's not clear that
> it's sensible for people who aren't having the problem to spend time
> working on it, compared to replacing a few broken routers.

This is a good question and a good point.  Aside from the Hurricane 
link, which seems to be updated daily, the next best source of information I've 
seen is RIPE meeting archives, here: and in 

Quoting from page 5:

"* 0.238% of users have useful IPv6 connectivity (and prefer IPv6)
 * 0.09% of users have broken IPv6 connectivity
   That is, adding an AAAA record will make these users unable to view your 

Approximately 2 or 3 users per thousand prefer IPv6, and approximately 38% of 
these IPv6 users have broken connectivity, as of a year ago.  Page 16 breaks 
down IPv6 traffic volume by operating system, but the status for NetBSD 
community in particular might be more accurately described by obtaining numbers 
for the IPv6 vs. IPv4 traffic ratio to, your FTP servers, etc.


Home | Main Index | Thread Index | Old Index