[nginx] support http2 per server

[Valentin V. Bartenev]

On Friday 09 June 2017 13:40:23 洪志道 wrote:
> Hi, Valentin.
> 
> "
> Also please note that with your patch clients are still able to
> negotiate HTTP/2 even if nginx doesn't announce it.
> "
> 
> Two points:
> 1. The patch forbids the clients explicitly not support HTTP/2 doing v2 (
> ngx_http_v2_init).
>     How to follow you mean of "with the patch, clients are still able to
> negotiate HTTP/2"
> 2. "even if nginx doesn't announce it"
>     Is it related to nginx?
> 
[..]

Your patch prevents advertising the protocol using ALPN and NPN, but
selecting protocol happens here (this part of code isn't touched): 
http://hg.nginx.org/nginx/file/tip/src/http/ngx_http_request.c#l808

In case of NPN, client can select protocol even if it hasn't been
advertised by the server.

  wbr, Valentin V. Bartenev