nghttpx - HTTP/2 proxy - HOW-TO¶

Default mode¶

If nghttpx is invoked without any -s, -p and --client, it operates in default mode. In this mode, nghttpx frontend listens for HTTP/2 requests and translates them to HTTP/1 requests. Thus it works as reverse proxy (gateway) for HTTP/2 clients to HTTP/1 web server. HTTP/1 requests are also supported in frontend as a fallback. If nghttpx is linked with spdylay library and frontend connection is SSL/TLS, the frontend also supports SPDY protocol.

By default, this mode’s frontend connection is encrypted using SSL/TLS. So server’s private key and certificate must be supplied to the command line (or through configuration file). In this case, the fontend protocol selection will is done via ALPN or NPN.

With --frontend-no-tls option, user can turn off SSL/TLS in frontend connection. In this case, SPDY protocol is not available even if spdylay library is liked to nghttpx. HTTP/2 and HTTP/1 are available on the frontend and a HTTP/1 connection can be upgraded to HTTP/2 using HTTP Upgrade. Starting HTTP/2 connection by sending HTTP/2 connection preface is also supported.

The backend is supposed to be HTTP/1 Web server. For example, to make nghttpx listen to encrypted HTTP/2 requests at port 8443, and a backend HTTP/1 web server is configured to listen to HTTP/1 request at port 8080 in the same host, run nghttpx command-line like this:

$ nghttpx -f0.0.0.0,8443 -b127.0.0.1,8080 /path/to/server.key /path/to/server.crt

Then HTTP/2 enabled client can access to the nghttpx in HTTP/2. For example, you can send GET request to the server using nghttp:

$ nghttp -nv https://localhost:8443/

HTTP/2 proxy mode¶

If nghttpx is invoked with -s option, it operates in HTTP/2 proxy mode. The supported protocols in frontend and backend connections are the same in default mode. The difference is that this mode acts like forward proxy and assumes the backend is HTTP/1 proxy server (e.g., squid). So HTTP/1 request must include absolute URI in request line.

By default, frontend connection is encrypted, this mode is also called secure proxy. If nghttpx is linked with spdylay, it supports SPDY protocols and it works as so called SPDY proxy.

With --frontend-no-tls option, SSL/TLS is turned off in frontend connection, so the connection gets insecure.

The backend must be HTTP/1 proxy server. nghttpx only supports 1 backend server address. It translates incoming requests to HTTP/1 request to backend server. The backend server performs real proxy work for each request, for example, dispatching requests to the origin server and caching contents.

For example, to make nghttpx listen to encrypted HTTP/2 requests at port 8443, and a backend HTTP/1 proxy server is configured to listen to HTTP/1 request at port 3128 in the same host, run nghttpx command-line like this:

$ nghttpx -s -f0.0.0.0,8443 -b127.0.0.1,3128 /path/to/server.key /path/to/server.crt

At the time of this writing, there is no known HTTP/2 client which supports HTTP/2 proxy in this fashion. You can use Google Chrome to use this as secure (SPDY) proxy to test it out, though it does not use HTTP/2 at all.

The one way to configure Google Chrome to use secure proxy is create proxy.pac script like this:

function FindProxyForURL(url, host) {
    return "HTTPS SERVERADDR:PORT";
}

SERVERADDR and PORT is the hostname/address and port of the machine nghttpx is running. Please note that Google Chrome requires valid certificate for secure proxy.

Then run Google Chrome with the following arguments:

$ google-chrome --proxy-pac-url=file:///path/to/proxy.pac --use-npn

Client mode¶

If nghttpx is invoked with --client option, it operates in client mode. In this mode, nghttpx listens for plain, unencrypted HTTP/2 and HTTP/1 requests and translates them to encrypted HTTP/2 requests to the backend. User cannot enable SSL/TLS in frontend connection.

HTTP/1 frontend connection can be upgraded to HTTP/2 using HTTP Upgrade. To disable SSL/TLS in backend connection, use --backend-no-tls option.

The backend connection is created one per worker (thread).

The backend server is supporsed to be a HTTP/2 web server (e.g., nghttpd). The one use-case of this mode is utilize existing HTTP/1 clients to test HTTP/2 deployment. Suppose that HTTP/2 web server listens to port 80 without encryption. Then run nghttpx as client mode to access to that web server:

$ nghttpx --client -f127.0.0.1,8080 -b127.0.0.1,80 --backend-no-tls

Then you can use curl to access HTTP/2 server via nghttpx:

$ curl http://localhost:8080/

Client proxy mode¶

If nghttpx is invoked with -p option, it operates in client proxy mode. This mode behaves like client mode, but it works like forward proxy. So HTTP/1 request must include absolute URI in request line.

HTTP/1 frontend connection can be upgraded to HTTP/2 using HTTP Upgrade. To disable SSL/TLS in backend connection, use --backend-no-tls option.

The backend connection is created one per worker (thread).

The backend server must be a HTTP/2 proxy. You can use nghttpx in HTTP/2 proxy mode as backend server. The one use-case of this mode is utilize existing HTTP/1 clients to test HTTP/2 connections between 2 proxies. The another use-case is use this mode to aggregate local HTTP/1 connections to one HTTP/2 backend encrypted connection. This makes HTTP/1 clients which does not support secure proxy can use secure HTTP/2 proxy via nghttpx client mode.

Suppose that HTTP/2 proxy listens to port 8443, just like we saw in HTTP/2 proxy mode. To run nghttpx in client proxy mode to access that server, invoke nghttpx like this:

$ nghttpx -p -f127.0.0.1,8080 -b127.0.0.1,8443

Then you can use curl to issue HTTP request via HTTP/2 proxy:

$ curl --http-proxy=http://localhost:8080 http://www.google.com/

You can configure web browser to use localhost:8080 as forward proxy.

HTTP/2 bridge mode¶

If nghttpx is invoked with --http2-bridge option, it operates in HTTP/2 bridge mode. The supported protocols in frontend and backend connections are the same in default mode.

With --frontend-no-tls option, SSL/TLS is turned off in frontend connection, so the connection gets insecure.

The backend server is supporsed to be a HTTP/2 web server or HTTP/2 proxy. Since HTTP/2 requests opaque between proxied and non-proxied request, the backend server may be proxy or just web server depending on the context of incoming requests.

The use-case of this mode is aggregate the incoming connections to one HTTP/2 connection. One backend HTTP/2 connection is created per worker (thread).

Disable SSL/TLS¶

In default mode, HTTP/2 proxy mode and HTTP/2 bridge mode, frontend connections are encrypted with SSL/TLS by default. To turn off SSL/TLS, use --frontend-no-tls option. If this option is used, the private key and certificate are not required to run nghttpx.

In client mode, client proxy mode and HTTP/2 bridge mode, backend connections are encrypted with SSL/TLS by default. To turn off SSL/TLS, use --backend-no-tls option.

Specifying additional CA certificate¶

By default, nghttpx tries to read CA certificate from system. But depending on the system you use, this may fail or is not supported. To specify CA certificate manually, use --cacert option. The specified file must be PEM format and can contain multiple certificates.

By default, nghttpx validates server’s certificate. If you want to turn off this validation, knowing this is really insecure and what you are doing, you can use -k option to disable certificate validation.

Read/write rate limit¶

nghttpx supports transfer rate limiting on frontend connections. You can do rate limit per connection or per worker (thread) for reading and writeing individually.

To rate limit per connection for reading, use --read-rate and --read-burst options. For writing, use --write-rate and --write-burst options.

To rate limit per worker (thread), use --worker-read-rate and --worker-read-burst options. For writing, use --worker-write-rate and --worker-write-burst.

If both per connection and per worker rate limit configurations are specified, the lower rate is used.

Please note that rate limit is performed on top of TCP and nothing to do with HTTP/2 flow control.