In attachment, you'll find my proposed patch for this problem.
On 04/19/2013 02:40 PM, Patrick Valsecchi wrote:
> Hi,
>
> I have a lot of trouble using c-ares on one of my windows boxes.
>
> The machine has two interfaces:
> 1) configured with a static IP address and it has DNS in automatic
> mode, but doesn't find any.
> 2) configured by DHCP and it receives a valid DNS interface
>
> My problem is that windows (at least 7), in all it's glory, invents
> DNS addesses for my first interface with 3 addresses taken from an
> outdated draft RFC [1]. And for some reasons, it shows them multiple
> times when GetAdaptersAddresses is called.
>
> So I end up with 13 DNS server addresses:
>
> * fec0:0:0:ffff::1
> * fec0:0:0:ffff::2
> * fec0:0:0:ffff::3
> * 10.104.48.2 <- my actual server
> * fec0:0:0:ffff::1
> * fec0:0:0:ffff::2
> * fec0:0:0:ffff::3
> * 10.104.48.2
> * fec0:0:0:ffff::1
> * fec0:0:0:ffff::2
> * fec0:0:0:ffff::3
>
> c-ares doesn't behave very well with such setup. At each query, it
> will start over with the first server, wait for a timeout of 5 seconds
> and then try the second one, ... . So I have to wait 15s for each
> query to complete.
>
> My first suggestion would be to apply this patch in order to remember
> the last good server and start from this one afterwards:
> diff --git a/c-ares/ares_process.c b/c-ares/ares_process.c
> --- a/c-ares/ares_process.c
> +++ b/c-ares/ares_process.c
> @@ -622,6 +622,8 @@
> }
> }
>
> + if (channel->rotate != 1)
> + channel->last_server = whichserver;
> end_query(channel, query, ARES_SUCCESS, abuf, alen);
> }
>
> Then I'd suggest to sort the servers in the ares_channel and put the
> fec0:: ones at the end.
>
> What do you think?
>
>
> [1] http://tools.ietf.org/id/draft-ietf-ipngwg-dns-discovery-03.txt