HTTP2D module

Admin Guide

Overview

This module provides an RFC 7540/9113 HTTP/2 server implementation with “h2” ALPN support, based on the nghttp2 library (https://nghttp2.org/).

HTTP/2, introduced in 2015, is a binary protocol with added transactional layers (SESSION, FRAME), which allow identifying and managing multiple, concurrent transfers over the same TCP/TLS connection. Thus, the revised protocol primarily aims to reduce resource usage for both clients and servers, by reducing the amount of TCP and/or TLS handshakes performed when loading a given web page.

The OpenSIPS http2d server includes support for both “h2” (TLS secured) and “h2c” (cleartext) HTTP/2 connections. The requests arrive at opensips.cfg level using the http2 request event, where script writers may process the data and respond accordingly.

Dependencies

OpenSIPS Modules

None.

External Libraries or Applications

The HTTP/2 server is provided by the nghttp2 library, which runs on top of the libevent server framework.

Overall, the following libraries must be installed before running OpenSIPS with this module loaded:

• libnghttp2
• libevent, libevent_openssl
• libssl, libcrypto

Exported Parameters

ip (string)

The listening IPv4 address.

Default value is “127.0.0.1”.

Setting the ip parameter

modparam("http2d", "ip", "127.0.0.2")

port (integer)

The listening port.

Default value is 443.

Setting the port parameter

modparam("http2d", "port", 5000)

tls_cert_path (string)

File path to the TLS certificate, in PEM format.

Default value is NULL (not set).

Setting the tls_cert_path parameter

modparam("http2d", "tls_cert_path", "/etc/pki/http2/cert.pem")

tls_cert_key (string)

File path to the TLS private key, in PEM format.

Default value is NULL (not set).

Setting the tls_cert_key parameter

modparam("http2d", "tls_cert_key", "/etc/pki/http2/private/key.pem")

max_headers_size (integer)

The maximum amount of bytes allowed for all header field names and values combined in a single HTTP/2 request processed by the server. Once this threshold is reached, extra headers will no longer be provided at script level and will be reported as errors instead.

Default value is 8192 bytes.

Setting the max_headers_size parameter

modparam("http2d", "max_headers_size", 16384)

response_timeout (integer)

The maximum amount of time, in milliseconds, that the library will allow the opensips.cfg processing to take for a given HTTP/2 request.

Once this timeout is reached, the module will auto-generate a 408 (request timeout) reply.

Default value is 2000 ms.

Setting the response_timeout parameter

modparam("http2d", "response_timeout", 5000)

Exported Functions

http2_send_response(code, [headers_json], [data])

Sends a response for the HTTP/2 request being processed. The ":status" header field will be automatically included by the module as 1st header, so it must not be included in the headers_json array.

Parameters

• code (integer) - The HTTP/2 reply code
• headers_json (string, default: NULL) - Optional JSON Array containing {“header”: “value”} elements, denoting HTTP/2 headers and their values to be included in the response message.
• data (string, default: NULL) - Optional DATA payload to include in the response message.

Return Codes

• 1 - Success
• -1 - Internal Error

This function can only be used from an EVENT_ROUTE.

http2_send_response() usage

event_route [E_HTTP2_REQUEST] {
  xlog(":: Method:  $param(method)\n");
  xlog(":: Path:    $param(path)\n");
  xlog(":: Headers: $param(headers)\n");
  xlog(":: Data:    $param(data)\n");

  $json(hdrs) := $param(headers);
  xlog("content-type: $json(hdrs/content-type)\n");

  $var(rpl_headers) = "[
  { \"content-type\": \"application/json\" },
  { \"server\": \"OpenSIPS 3.5\" },
  { \"x-current-time\": \"1711457142\" },
  { \"x-call-cost\": \"0.355\" }
  ]";

  $var(data) = "{\"status\": \"success\"}";

  if (!http2_send_response(200, $var(rpl_headers), $var(data)))
    xlog("ERROR - failed to send HTTP/2 response\n");
}

Exported Events

E_HTTP2_REQUEST

This event is raised whenever the http2d module is loaded and OpenSIPS receives an HTTP/2 request on the configured listening interface(s).

Parameters:

• method (string) - value of the ":method" HTTP/2 header
• path (string) - value of the ":path" HTTP/2 header
• headers (string) - JSON Array with all headers of the request, including pseudo-headers
• data (string, default: NULL) - If the request included a payload, this parameter will hold its contents

Note that this event is currently designed to be mainly consumed by an event_route, since that is the only way to gain access to the http2 send response function in order to build custom response messages. On the other hand, if the application does not mind the answer being always a 200 with no payload, this event can be successfully consumed through any other EVI-compatible delivery channel ☺️

Contributors

By Commit Statistics

Top contributors by DevScore⁽¹⁾, authored commits⁽²⁾ and lines added/removed⁽³⁾

#	Name	DevScore	Commits	Lines++	Lines—
1.	Liviu Chircu (@liviuchircu)	42	8	2592	722
2.	Stefan Darius (@dariusstefan)	8	4	269	33
3.	Razvan Crainea (@razvancrainea)	6	4	58	7
4.	Peter Lemenkov (@lemenkov)	4	2	2	2

(1) DevScore = author_commits + author_lines_added / (project_lines_added / project_commits) + author_lines_deleted / (project_lines_deleted / project_commits)

(2) including any documentation-related commits, excluding merge commits

(3) ignoring whitespace edits, renamed files and auto-generated files

By Commit Activity

#	Name	Commit Activity
1.	Stefan Darius (@dariusstefan)	Jun 2026 - Jul 2026
2.	Razvan Crainea (@razvancrainea)	May 2024 - Jun 2026
3.	Peter Lemenkov (@lemenkov)	Jul 2025 - May 2026
4.	Liviu Chircu (@liviuchircu)	Mar 2024 - May 2024

(1) including any documentation-related commits, excluding merge commits

Documentation

Contributors

Last edited by: Razvan Crainea (@razvancrainea), Liviu Chircu (@liviuchircu).

License

All documentation files (i.e. .md extension) are licensed under the Creative Common License 4.0