Reverse proxying HTTP/2 from h2 to h2c

Question

We have a java web server which is able to serve content over h2c (HTTP/2 clear text)

We would like to reverse proxy connections established using h2 (i.e. standard HTTP/2 over SSL) to the java server in h2c.

Enabling HTTP/2 on nginx is simple enough and handling incoming h2 connections works fine.

How do we tell nginx to proxy the connection using h2c rather than http/1.1 ?

Note: a non-nginx solution may be acceptable

server {
    listen       443 ssl http2 default_server;
    server_name  localhost;

    ssl_certificate      /opt/nginx/certificates/???.pem;
    ssl_certificate_key  /opt/nginx/certificates/???.pk8.key.pem;

    ssl_session_cache    shared:SSL:1m;
    ssl_session_timeout  5m;

    ssl_ciphers  HIGH:!aNULL:!MD5;
    ssl_prefer_server_ciphers  on;

    location / {
        proxy_pass http://localhost:8080/;  ## <---- h2c here rather than http/1.1
    }
}

CONCLUSION (June 2016)

This can be done with haproxy using a configuration file as simple as the one below.

Querying (HttpServletRequest) req.getProtocol() clearly returns HTTP/2.0

global
tune.ssl.default-dh-param 1024

defaults
timeout connect 10000ms
timeout client 60000ms
timeout server 60000ms

frontend fe_http
mode http
bind *:80
# Redirect to https
redirect scheme https code 301

frontend fe_https
mode tcp
bind *:443 ssl no-sslv3 crt mydomain.pem ciphers TLSv1.2 alpn h2,http/1.1
default_backend be_http

backend be_http
mode tcp
server domain 127.0.0.1:8080

Answer 1

HAProxy does support that.

HAProxy can offload TLS and forward to a backend that speaks h2c.

Details on how to setup this configuration are available in this blog post.