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Re: [lwip-users] dns: remember multiple IP addresses patch

From: Jan Menzel
Subject: Re: [lwip-users] dns: remember multiple IP addresses patch
Date: Wed, 21 Feb 2018 20:22:22 +0100
User-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0

On 21.02.2018 19:49, address@hidden wrote:
> On 21.02.2018 17:18, Jan Menzel wrote:
>> Hi all!
>>     I'd like to share a small patch with you that allows the dns
>> subsystem
>> to remember and handle more then one IP address from response messages.
>> It basically parses out all IP address and stores them in an array. It
>> then returns a random entry.
> What is this used for? A good DNS server should sort the IP address list
> of a host differently for each request.
We have a number of devices all located behind a single public ip
address which request time from public ntp server pools. Without this
change all devices connected to the same server which just returned
Kiss-of-Death. It seems, that the router in this installation does not
qualify for a good DNS server.

> If you want your client application to load-balance although the locally
> cached DNS entry has expired, I think a better approach would be to
> actually return all available IPs to the client and let it chose one
> (i.e. implement the random algorithm in your application). That way,
> 'gethostbyname' etc. could return all entries as well.
Yes, this would be an option. I rejected this approach because it breaks
the api.


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