W3C home > Mailing lists > Public > public-html@w3.org > July 2008

Re: websocket HTTP response parsing

From: Ian Hickson <ian@hixie.ch>
Date: Sun, 6 Jul 2008 21:30:37 +0000 (UTC)
To: Julian Reschke <julian.reschke@gmx.de>
Cc: "public-html@w3.org" <public-html@w3.org>
Message-ID: <Pine.LNX.4.62.0807062047010.11215@hixie.dreamhostps.com>

On Sun, 6 Jul 2008, Julian Reschke wrote:
> > >
> > > As far as I can tell, it depends on specifics of the server 
> > > implementation. I can easily imagine cases where it's the HTTP 
> > > server that replies to the upgrade request, and control to the new 
> > > server component passes only afterwards. In that case it could be 
> > > hard to produce the specified byte sequence.
> > 
> > Yes, it may require careful work when the servers are updated.
> So why make it harder than necessary?

We need a handshake that can guarantee that we've contacted a WebSocket 
server and not some other server that's being tricked into sending data 
that looks like the handshake. For that purpose, we use the headers that 
come before the server has to echo anything, and we make that as long as 
possible (and as unique as possible) by moving both those headers there.

> > > Also, did you consider the impact of intermediates in the request 
> > > path?
> > 
> > You mean, like proxies? Sure, the spec defines how to handle those.
> What if they somehow modify the reason phrase? It would be outside the 
> control of the server, and communication would break.

Any proxy that did that would be deeply violating HTTP rules and would 
also be breaking TLS tunnels.

In any case, mcarter implemented and tested this with several proxies, as 
I understand it, to make sure this would work.

> > > But it's more complex than it needs to be
> > 
> > It's a stream of bytes. It's longer than absolutely necessary, sure, 
> > but how can it be more complex than necessary?
> Ok, it's longer. What for?

Why shouldn't it be?

It seems better to use whatever HTTP uses in its descriptions than go 
ahead and make up our own stuff for no reason. If we had a good reason to 
use something else then sure, but here we really don't. Would you rather 
have the status text be something else, like "101 WebSocket Handshake"?

> > Why is using the HTTP spec's recommended text a problem?
> The HTTP spec doesn't recommend any specific text. The reason phrase is 
> for human consumption only. For instance, there are servers known to 
> vary it by Accept-Language or locale.

The section defining code 101 is "10.1.2 101 Switching Protocols". So 
that's what we use here. Seems reasonable to me.

> There's simply no point in putting it in, so why do it?

This seems like an unbelievably minor point of basically no importance 
whatsoever. Am I missing some key way in which this actually matters? If 
not, then it seems pointless to be arguing over it.

> > Could you describe the actual practical problem you are concerned 
> > about?
> Could you describe the actual practical problem because of which you're 
> putting in a reason phrase?

I'll take that as a "no", and assume there is no actual problem, then. 
(I've described the reason for the handshake earlier in this e-mail.)

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Sunday, 6 July 2008 21:31:16 UTC

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