Re: [Boost-users] [asio] negating address_configured

Subject: Re: [Boost-users] [asio] negating address_configured
From: Alexander Lamaison (awl03_at_[hidden])
Date: 2011-03-04 08:52:40

On Fri, 04 Mar 2011 14:30:36 +0100, Juraj Ivanèiæ wrote:

> On 4.3.2011 11:48, Alexander Lamaison wrote:
>> What is the correct way to negate the (default) resolver flag,
>> address_configured?
>>
>> On Windows, at least, specifying address_configured (which translates to
>> AI_ADDRCONFIG) has a nasty side effect.  If the 'external' network is down,
>> the resolver can no longer resolve the "localhost" address.  More here
>> http://src.chromium.org/viewvc/chrome/trunk/src/net/base/host_resolver.cc?r1=16212&r2=16211
>>
>> address_configured is the default flag for ip::basic_resolver_query so I
>> need to specify a flag that turns it off.  In the underlying addrinfo
>> struct this would just mean specifying 0 as the flag but that isn't an
>> option with ASIO as far as I can tell.  How would I do this?
> 
> I ran into this problem, and came up with the following workaround:
> 
> boost::asio::ip::tcp::resolver::query query(
>      hostname,
>      port,
>      boost::asio::ip::tcp::resolver::query::all_matching
> );

Doesn't all_matching have it's own meaning?  In other words, doesn't
getaddrinfo behave differently when given 0 as its flags rather than
AI_ALL?

MSDN says "If the AI_ALL bit is set, a request is made for IPv6 addresses
and IPv4 addressses with AI_V4MAPPED." which is as clear as mud to me.

Thanks.

Alex

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