Federico Cabiddu

Giacomo Vacca

Camille Oudot


Edited by

Federico Cabiddu

Table of Contents

1. Admin Guide
1. Overview
2. Dependencies
2.1. Kamailio Modules
2.2. External Libraries or Applications
3. Parameters
3.1. workers (int)
3.2. connection_timeout (str)
3.3. hash_size (str)
3.4. tls_version (int)
3.5. tls_verify_host (int)
3.6. tls_verify_peer (int)
3.7. curl_verbose (int)
3.8. memory_manager (string)
3.9. tls_client_cert (int)
3.10. tls_client_key (int)
3.11. tls_ca_path (int)
4. Functions
4.1. http_async_query(url, [post_data], route_name)
4.2. http_async_suspend(suspend)
4.3. tls_verify_host(verify)
4.4. tls_verify_peer(verify)
4.5. http_set_timeout(timeout)
4.6. http_append_header(header)
4.7. http_set_method(method)
4.8. http_set_tls_client_cert(path)
4.9. http_set_tls_client_key(path)
4.10. http_set_tls_ca_path(path)
5. Pseudo Variables
6. Statistics
6.1. requests
6.2. replies
6.3. errors
6.4. timeouts

List of Examples

1.1. Set workers parameter
1.2. Set connection_timeout parameter
1.3. Set hash_size parameter
1.4. Set tls_version parameter
1.5. Set tls_verify_host parameter
1.6. Set tls_verify_peer parameter
1.7. Set curl_verbose parameter
1.8. Set memory_manager parameter
1.9. Set tls_client_cert parameter
1.10. Set tls_client_key parameter
1.11. Set tls_ca_path parameter
1.12. http_async_query() usage
1.13. http_async_suspend() usage
1.14. tls_verify_host() usage
1.15. tls_verify_peer() usage
1.16. http_set_timeout() usage
1.17. http_append_header() usage
1.18. http_set_method() usage
1.19. http_set_tls_client_cert() usage
1.20. http_set_tls_client_key() usage
1.21. http_set_tls_ca_path() usage
1.22. $http_req(key) variable usage

Chapter 1. Admin Guide

1. Overview

This module performs asynchronous HTTP queries.

2. Dependencies

2.1. Kamailio Modules

The following modules must be loaded before this module:

  • tm - Transaction module

  • pv - Pseudo-Variables module

2.2. External Libraries or Applications

The following libraries or applications must be installed before running Kamailio with this module loaded:

  • libcurl libev

3. Parameters

3.1. workers (int)

Number of worker processes to be started to send HTTP requests and asynchronously handle responses.

Default value is 1.

Example 1.1. Set workers parameter

modparam("http_async_client", "workers", 2)

3.2. connection_timeout (str)

Defines in milliseconds how long Kamailio waits for response from HTTP server.

Default value is 500ms.

Example 1.2. Set connection_timeout parameter

modparam("http_async_client", "connection_timeout", 1000)

3.3. hash_size (str)

The size of the hash table internally used to keep the requests. A larger table is much faster but consumes more memory. The hash size must be a power of two, otherwise it will be rounded down to the nearest power of two.

Default value is 2048.

Example 1.3. Set hash_size parameter

modparam("http_async_client", "hash_size", 1024)

3.4. tls_version (int)

For HTTPS connections, what's the preferred SSL version.

Default value is 0 (default SSL version).

Example 1.4. Set tls_version parameter

modparam("http_async_client", "tls_version", 6)

3.5. tls_verify_host (int)

For HTTPS connections, whether the client should verify the server host.

Default value is 2 (enabled).

Example 1.5. Set tls_verify_host parameter

modparam("http_async_client", "tls_verify_host", 0)

3.6. tls_verify_peer (int)

For HTTPS connections, whether the client should verify the server identity.

Default value is 1 (enabled).

Example 1.6. Set tls_verify_peer parameter

modparam("http_async_client", "tls_verify_peer", 0)

3.7. curl_verbose (int)

If defined to a non-zero value, extra informations from cURL (request and response headers) will be included in the kamailio logs, with LM_INFO priority.

Default value is 0 (disabled).

Example 1.7. Set curl_verbose parameter

modparam("http_async_client", "curl_verbose", 1)

3.8. memory_manager (string)

Choose the memory manager used by curl:

  • shm: curl will use kamailio's SHM pool and memory manager

  • sys: curl will use the system memory and memory manager (malloc, free, ...)

Note: if this module is used in conjunction with another module using libcurl (http_client, utils, xcap, xcap_client), it must be loaded as first one for this parameter to have effect, otherwise curl will likely use the system memory allocator by default. On the other hand if the module is loaded before any other module using libcurl, all the modules will use the memory manager specified by this parameter.

Default value "shm"

Example 1.8. Set memory_manager parameter

modparam("http_async_client", "memory_manager", "sys")

3.9. tls_client_cert (int)

For HTTPS connections, the file path of the TLS client certificate to be used

Default value is NULL (not used). Default type is PEM.

Example 1.9. Set tls_client_cert parameter

modparam("http_async_client", "tls_client_cert", "/etc/kamailio/ssl/clientcert.pem")

3.10. tls_client_key (int)

For HTTPS connections, the file path of the TLS client certificate key

Default value is NULL (not used).

Example 1.10. Set tls_client_key parameter

modparam("http_async_client", "tls_client_key", "/etc/kamailio/ssl/clientcert.key")

3.11. tls_ca_path (int)

The path of the directory holding the CA certificates.

Default value is NULL..

Example 1.11. Set tls_ca_path parameter

modparam("http_async_client", "tls_ca_path", "/etc/kamailio/ssl/ca/")

4. Functions

4.1.  http_async_query(url, [post_data], route_name)

Sends HTTP(S) request asyncronously to the URL given in url parameter, which is a string that may contain pseudo variables.

Unless a specific HTTP method was specified using http_async_set_method(), it defaults to a GET request, or to a POST request if post_data is issued as second argument.

Parameter post_data, optional, which is sent as the body of the request, may also contain pseudo variables.

Parameter route_name defines the route to be executed upon reception of HTTP reply, on error or on timeout. If a transaction exists before calling http_async_query(), it will be paused and resumed in this route, while the routing script execution will be stopped. If executed in a transactionless context, or if http_async_suspend_transaction() or $http_req(suspend) are used to not suspend the transaction, the routing script execution will continue and the query result will be available in route_name.

Return value: 0 (stop script execution) on success in transaction context, 1 (continue script execution) in transaction-less context (or if http_async_suspend_transaction(0) or $http_req(suspend) are used), -1 on error.

This function can be used from ANY_ROUTE.

This method is executed asynchronously. The HTTP return code, body and error are returned in the module-specific $http_* PVs (see below). See example on how to retrieve return values.

Example 1.12. http_async_query() usage

# create a transaction to be paused, and resumed in route[HTTP_REPLY]
http_async_query("$rU&f_uri=$fU", "HTTP_REPLY");
http_async_query("", "{'r_uri':'$rU', 'f_uri':'$fU'}", "HTTP_REPLY");
route[HTTP_REPLY] {
    if ($http_ok) {
        xlog("L_INFO", "route[HTTP_REPLY]: status $http_rs\n");
        xlog("L_INFO", "route[HTTP_REPLY]: body   $http_rb\n");
    } else {
        xlog("L_INFO", "route[HTTP_REPLY]: error  $http_err)\n");

4.2.  http_async_suspend(suspend)

In a transaction context if the transaction must be suspended and script execution stopped.

Parameter suspend set to "1" to suspend the transaction, "0" to not suspend and continue with script execution. Default: 1 (transaction suspended).

Example 1.13. http_async_suspend() usage

# the transaction won't be suspended for the next query
http_async_query("", "HTTP_REPLY");
xlog("L_INFO", "query sent\n");
t_reply("200", "Ok");


4.3.  tls_verify_host(verify)

For the next HTTPS connection, whether the client should verify the server host.

Parameter verify set to "1" to enable the host verification, "0" to disable. Default: the global value set as verify_host module parameter.

Example 1.14. tls_verify_host() usage

# host verification is disabled for the next query
http_async_query("", "HTTP_REPLY");

4.4.  tls_verify_peer(verify)

For the next HTTPS connection, whether the client should verify the server identity.

Parameter verify set to "1" to enable the identity verification, "0" to disable. Default: the global value set as verify_peer module parameter.

Example 1.15. tls_verify_peer() usage

# server identity verification is disabled for the next query
http_async_query("", "HTTP_REPLY");

4.5.  http_set_timeout(timeout)

For the next HTTP query, set the response timeout.

Parameter timeout string representing the timeout in milliseconds. Default: the global value set as http_timeout module parameter.

Example 1.16. http_set_timeout() usage

# the server must respond in maximum 200ms, otherwise the query will fail
http_async_query("", "HTTP_REPLY");

4.6.  http_append_header(header)

Set/remove/replace a header in the next HTTP query.

From libcurl's documentation:

If you add a header that is otherwise generated and used by libcurl internally, your added one will be used instead. If you add a header with no content as in 'Accept:' (no data on the right side of the colon), the internally used header will get disabled. With this option you can add new headers, replace internal headers and remove internal headers. To add a header with no content (nothing to the right side of the colon), use the form 'MyHeader;' (note the ending semicolon).

The headers included in the linked list must not be CRLF-terminated, because libcurl adds CRLF after each header item.

Parameter header string representing the header to pass to libcurl for the next query.

Example 1.17. http_append_header() usage

http_append_header("X-Sip-Call-Id: $ci");
# a new 'X-Sip-Call-Id' header will be added to the next query
http_append_header("Content-Type": application/json");
# the curl default 'application/x-www-form-urlencoded' Content-Type will be replaced
http_async_query("", "{'foo': 'bar'}", "HTTP_REPLY");

4.7.  http_set_method(method)

For the next HTTP query, set the method.

Parameter method string representing the method (verb): either "GET", "POST", "PUT" or "DELETE" (these are the only supported methods). (Note: if http_set_method() is not called before a query, curl will use GET, or POST if a body is specified)

Example 1.18. http_set_method() usage

# the next query will be a HTTP PUT request
http_async_query("", "{'foo': 'bar'}", "HTTP_REPLY");

4.8.  http_set_tls_client_cert(path)

For the next HTTPS connection, what client certificate to use.

Default: the global value set as tls_client_cert module parameter.

Example 1.19. http_set_tls_client_cert() usage

# Next query will use the client cert above
http_async_query("", "HTTP_REPLY");

4.9.  http_set_tls_client_key(path)

For the next HTTPS connection, what client certificate key to use.

Default: the global value set as tls_client_key module parameter.

Example 1.20. http_set_tls_client_key() usage

# Next query will use the client cert key above
http_async_query("", "HTTP_REPLY");

4.10.  http_set_tls_ca_path(path)

For the next HTTP connection, what CA certificate files to use.

Default: the global value set as tls_ca_path module parameter.

Example 1.21. http_set_tls_ca_path() usage

# Next query will use the CA certs above
http_async_query("", "HTTP_REPLY");

5. Pseudo Variables

The $http_req(key) write-only variable can be used to set custom parameters before sending a HTTP query

setting this variable has the same effect than using the http_set_*()functions

key can be one of:

  • all: if set to $null, resets all the parameters to their default value (the ones defined in modparam)

  • hdr: sets/modifies/remove a HTTP header (see http_append_header()). N.B.: setting this variable multiple times will add several headers to the query.

  • method: sets the HTTP method (see http_set_method())

  • timeout: sets the HTTP timeout (see http_set_timeout())

  • tls_client_cert: sets the client certificate to use (see http_set_tls_client_cert())

  • tls_client_key: sets the client certificate key to use (see http_set_tls_client_key())

  • tls_ca_path: sets the CA certificate files to use (see http_set_tls_ca_path())

  • suspend: if set to 0 doesn't suspend the current transaction before performing the query (see http_async_suspend())

Example 1.22. $http_req(key) variable usage

$http_req(all) = $null;                    # reset the parameters
$http_req(timeout) = 100;                  # 100 ms
$http_req(method) = "DELETE";
$http_req(hdr) = "X-Sip-Call-Id: " + $ci;
$http_req(hdr) = "X-Foo: bar";             # add a 2nd header
$http_req(suspend) = 0;             # don't suspend the transaction, continue routing script's execution
# the following request will use the above parameters
http_async_query("", "HTTP_REPLY");

The following read-only pseudo variables can only be used in the callback routes executed by http_async_query()

  • $http_ok: 1 if cURL executed the request successfully, 0 otherwise (check $http_err for details)

  • $http_err: cURL error string if an error occured, $null otherwise

  • $http_rs: http status

  • $http_rr: http reason phrase

  • $http_hdr(Name): value of the Name header (the $(http_hdr(Name)[N]) syntax can also be used, check the SIP $hdr() PV documentation for details)

  • $http_mb and $http_ml: HTTP response buffer (including headers) and length

  • $http_rb and $http_bs: HTTP response body and body length

6. Statistics

6.1. requests

The number of http requests sent.

6.2. replies

The number of received http replies.

6.3. errors

The number of errors.

6.4. timeouts

The number of timed out requests.