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Re: [XHR] Open issue: allow setting User-Agent?

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Tue, 16 Oct 2012 13:08:59 -0400
Message-ID: <507D94AB.3000207@mit.edu>
To: Mark Baker <mark@zepheira.com>
CC: Hallvord Reiar Michaelsen Steen <hallvord@opera.com>, Jungkee Song <jungkee.song@samsung.com>, Julian Aubourg <j@ubourg.net>, public-webapps@w3.org
On 10/16/12 1:04 PM, Mark Baker wrote:
> That would be an improvement, but wouldn't solve the problem of
> intermediary cache poisoning.

Ah, yes. Intermediary caches are indeed a problem.  I don't see anything 
the browser can do to solve that problem, unfortunately.

On the other hand, caches that don't assume "Vary: User-Agent" are 
already completely broken on the web when they sit between multiple 
users using multiple browsers and the rest of the web....

> Julian Aubourg wrote;
>> Couldn't we simply state in the spec that browsers must add the User-Agent header to the Vary list, all the time?
> Vary is a response header, set by the server.

The point is that a browser can act as if every single server response 
included "Vary: User-Agent".  And perhaps should.  Intermediary caches 
_certainly_ should.

Received on Tuesday, 16 October 2012 17:09:33 UTC

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