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Date: Thu, 19 May 2016 01:37:54 -0700 (PDT)
From: Don Lewis <truckman@FreeBSD.org>
Subject: Re: r299512 breaks dhclient on some networks
To: ian.freislich@capeaugusta.com
cc: freebsd-current@freebsd.org
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On 18 May, Ian FREISLICH wrote:
> On 05/18/16 20:19, Don Lewis wrote
>> It looks to me like r299512 is changing the format of the client
>> identifier by inserting the struct hardware hlen field into it.  That's
>> not valid if htype is non-zero the way I interpret RFC 2132.  On the
>> other hand, I would think that the server would interpret the client ID
>> as an opaque cookie, so I wouldn't think it would make a difference
>> (other than thinking this is a new client) unless your server is
>> configured to look for specific client IDs.
> 
> It's not that the server isn't working.  The client is discarding the
> server's offer for whatever reason.

There may be some other place in the code that validates the response
and that calculates the client ID the old way.  When it sees the
response with the new client ID, it doesn't match and the client
discards the response because it thinks the response is for some other
host.