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, traffic server). So HTTP/1 request must include absolute URI in request line.

By default, frontend connection is encrypted. So 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 supports multiple backend server addresses. 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 8080 in the same host, run nghttpx command-line like this:

$ nghttpx -s -f'*,8443' -b127.0.0.1,8080 /path/to/server.key /path/to/server.crt

At the time of this writing, Firefox nightly supports HTTP/2 proxy. Chromium can use nghttpx as secure (SPDY) proxy and will support HTTP/2 proxy in the near future.

To make Firefox nightly or Chromium use nghttpx as HTTP/2 or SPDY proxy, user has to create proxy.pac script file 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 both Firefox nightly and Chromium require valid certificate for secure proxy.

For Firefox nightly, open Preference window and select Advanced then click Network tab. Clicking Connection Settings button will show the dialog. Select "Automatic proxy configuration URL" and enter the path to proxy.pac file, something like this:

file:///path/to/proxy.pac

For Chromium, use following command-line:

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

As HTTP/1 proxy server, Squid may work as out-of-box. Traffic server requires to be configured as forward proxy. Here is the minimum configuration items to edit:

CONFIG proxy.config.reverse_proxy.enabled INT 0
CONFIG proxy.config.url_remap.remap_required INT 0

Consult Traffic server documentation to know how to configure traffic server as forward proxy and its security implications.

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.

By default, the number of backend HTTP/2 connections per worker (thread) is determined by number of -b option. To adjust this value, use --backend-http2-connections-per-worker option.

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.

By default, the number of backend HTTP/2 connections per worker (thread) is determined by number of -b option. To adjust this value, use --backend-http2-connections-per-worker option.

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 connections are the same in default mode. The protocol in backend is HTTP/2 only.

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

By default, the number of backend HTTP/2 connections per worker (thread) is determined by number of -b option. To adjust this value, use --backend-http2-connections-per-worker option.

The backend server is supporsed to be a HTTP/2 web server or HTTP/2 proxy. If backend server is HTTP/2 proxy, use --no-location-rewrite and --no-host-rewrite options to disable rewriting location, host and :authority header field.

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 frontend connection for reading and writeing individually.

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

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

Rewriting location header field¶

nghttpx automatically rewrites location response header field if the following all conditions satisfy:

• URI in location header field is not absolute URI or is not https URI.
• URI in location header field includes non empty host component.
• host (without port) in URI in location header field must match the host appearing in :authority or host header field.

When rewrite happens, URI scheme and port are replaced with the ones used in frontend, and host is replaced with which appears in :authority or host request header field. :authority header field has precedence. If the above conditions are not met with the host value in :authority header field, rewrite is retried with the value in host header field.

Hot swapping¶

nghttpx supports hot swapping using signals. The hot swapping in nghttpx is multi step process. First send USR2 signal to nghttpx process. It will do fork and execute new executable, using same command-line arguments and environment variables. At this point, both current and new processes can accept requests. To gracefully shutdown current process, send QUIT signal to current nghttpx process. When all existing frontend connections are done, the current process will exit. At this point, only new nghttpx process exists and serves incoming requests.

Re-opening log files¶

When rotating log files, it is desirable to re-open log files after log rotation daemon renamed existing log files. To tell nghttpx to re-open log files, send USR1 signal to nghttpx process. It will re-open files specified by --accesslog-file and --errorlog-file options.

Multiple backend addresses¶

nghttpx supports multiple backend addresses. To specify them, just use -b option repeatedly. For example, to use backend1:8080 and backend2:8080, use command-line like this: -bbackend1,8080 -bbackend2,8080. For HTTP/2 backend, see also --backend-http2-connections-per-worker option.