http/2 first experiences

Dridi Boukelmoune dridi at
Tue Oct 4 16:06:03 CEST 2016

On Tue, Oct 4, 2016 at 1:31 PM, Tom Anheyer <Tom.Anheyer at> wrote:
> Hello,
> I've setup a little test environment with varnish5 and hitch as TLS
> offloader. HTTP/2 works for me in FF and Chrome (after upgrading to openssl
> 1.0.2).

Hello Tom,

This is fantastic, thanks for the feedback on h2 using hitch+varnish.

> Which H2 features are supported so far?

I haven't looked closely, but if everything went according to plan,
the bare minimum (eg. varnish does not compress response headers

> How to do server push? If not supported yet - Is it planned?

It is planned, I don't know when it will land, and when it lands it
will probably introduce either a VMOD or new VCL syntax.

> 2016 11:26:36 GMT
>                                          "Incomplete code in
> h2_rx_rst_stream(), http2/cache_http2_proto.c line 113:

So apparently you reached one of the things Varnish doesn't implement
yet, in this case RST frames. Your browser tried to cancel a request
and close the related streams and Varnish doesn't support it.

Spoiler alert, your browser may crash with DATA, PUSH_PROMISE and

The push makes no sense for a client, so you can ignore it if we
assume a sane browser.

You should be able to crash Varnish too if you send a request with a
body (eg. POST) or with very large headers (eg. tracking cookies).


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