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Re: [DNSOP] CNAME chain length limits

John R Levine <johnl@taugh.com> Wed, 27 May 2020 18:48 UTC

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Date: Wed, 27 May 2020 14:48:38 -0400
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From: John R Levine <johnl@taugh.com>
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Subject: Re: [DNSOP] CNAME chain length limits
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On Wed, 27 May 2020, John R Levine wrote:
> While I should have been doing something else, I made a rather long CNAME 
> chain.  When I looked up chain.examp1e.com it got SERVFAIL, but after I 
> warmed up my cache five links at a time by looking for chain5, chain10, 
> chain15, and so forth, it worked.  At least it worked in "dig" and "host". 
> When I try and look up http://chain.examp1e.com, Chrome waits a while and 
> says not found, Firefox waits a while and says "Hmm. We’re having trouble 
> finding that site." and Safari on my Mac hangs.  (Feel free to try it 
> yourself.)

FWIW, the cache is unbound 1.10.1.

R's,
John

> I realize the answer to most questions like this can be summarized as "don't 
> do that", but is there any consensus as to the maximum CNAME chain length 
> that works reliably, and what happens if the chain is too long? Hanging seems 
> sub-optimal.

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