Re: p1: Via and gateways

Willy Tarreau <w@1wt.eu> Sat, 20 April 2013 08:10 UTC

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Date: Sat, 20 Apr 2013 10:09:19 +0200
From: Willy Tarreau <w@1wt.eu>
To: Mark Nottingham <mnot@mnot.net>
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Subject: Re: p1: Via and gateways
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On Sat, Apr 20, 2013 at 05:55:59PM +1000, Mark Nottingham wrote:
> 
> On 20/04/2013, at 5:21 PM, David Morris <dwm@xpasc.com> wrote:
> > 
> > I don't care about MUST, but I think the Via header can be useful for
> > problem determination. A smart content server could also adjust for
> > a detected accelerator and/or transcoder ... perhaps by avoiding
> > optimizations dependant on a direct connection and byte/byte transfer
> > between the client and the server.
> > 
> > So I'm very much in favor of keeping the Via: header.
> 
> 
> Definitely not talking about getting rid of it. The (only, specific) point
> here is whether a gateway that doesn't add Via to responses should be called
> non-conformant.
> 
> Personally, I think it should be a MUST for proxies, in both directions.
> However, for a gateway, it either shouldn't be a requirement at all (for
> responses), or it should be a SHOULD with a get-out clause for reasons of
> security (along with a note that they'll need to accept responsibility for
> any issues caused by omitting Via). Still should probable be a MUST for
> requests from gateways.

But then do we want to declare all gateways non-conformant ? The only gateway
I've seen use the Via header was abusing it to put the client's IP address
into it, and none of the hosted servers behind it were ever confused by this
despite being a few tens of various products!

The only use I see with Via is to convey the original message's HTTP version,
but most (all?) gateways do not change this version because it's already
painful to be a gateway, you generally don't want to add more burden by
changing the protocol version between the two sides!

Willy