Protocols and Plugins

Modules
	plugin: lws-ssh-base

Data Structures
struct	lws_protocols
struct	lws_plugin_header
struct	lws_plugin_protocol
struct	lws_plugin
struct	lws_plugin_evlib

Macros
#define	LWS_PROTOCOL_LIST_TERM   { NULL, NULL, 0, 0, 0, NULL, 0 }
#define	LWS_PLUGIN_API_MAGIC   191

Typedefs
typedef struct lws_plugin_header	lws_plugin_header_t
typedef struct lws_plugin_protocol	lws_plugin_protocol_t
typedef struct lws_plugin_evlib	lws_plugin_evlib_t
typedef int(*	each_plugin_cb_t) (struct lws_plugin *p, void *user)

Functions
LWS_VISIBLE LWS_EXTERN const struct lws_protocols *	lws_vhost_name_to_protocol (struct lws_vhost *vh, const char *name)
LWS_VISIBLE LWS_EXTERN const struct lws_protocols *	lws_get_protocol (struct lws *wsi)
LWS_VISIBLE LWS_EXTERN const struct lws_protocols *	lws_protocol_get (struct lws *wsi) LWS_WARN_DEPRECATED
LWS_VISIBLE LWS_EXTERN void *	lws_protocol_vh_priv_zalloc (struct lws_vhost *vhost, const struct lws_protocols *prot, int size)
LWS_VISIBLE LWS_EXTERN void *	lws_protocol_vh_priv_get (struct lws_vhost *vhost, const struct lws_protocols *prot)
LWS_VISIBLE LWS_EXTERN void *	lws_vhd_find_by_pvo (struct lws_context *cx, const char *protname, const char *pvo_name, const char *pvo_value)
LWS_VISIBLE LWS_EXTERN void *	lws_adjust_protocol_psds (struct lws *wsi, size_t new_size)
LWS_VISIBLE LWS_EXTERN int	lws_finalize_startup (struct lws_context *context)
LWS_VISIBLE LWS_EXTERN const struct lws_protocol_vhost_options *	lws_pvo_search (const struct lws_protocol_vhost_options *pvo, const char *name)
LWS_VISIBLE LWS_EXTERN int	lws_pvo_get_str (void *in, const char *name, const char **result)
LWS_VISIBLE LWS_EXTERN int	lws_protocol_init (struct lws_context *context)
LWS_VISIBLE LWS_EXTERN int	lws_plugins_init (struct lws_plugin **pplugin, const char *const *d, const char *_class, const char *filter, each_plugin_cb_t each, void *each_user)
LWS_VISIBLE LWS_EXTERN int	lws_plugins_destroy (struct lws_plugin **pplugin, each_plugin_cb_t each, void *each_user)

Detailed Description

Protocol and protocol plugin -related apis

Protocols bind ws protocol names to a custom callback specific to that protocol implementaion.

A list of protocols can be passed in at context creation time, but it is also legal to leave that NULL and add the protocols and their callback code using plugins.

Plugins are much preferable compared to cut and pasting code into an application each time, since they can be used standalone.

Function Documentation

lws_adjust_protocol_psds()

LWS_VISIBLE LWS_EXTERN void* lws_adjust_protocol_psds	(	struct lws *	wsi,
		size_t	new_size
	)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_adjust_protocol_psds - change a vhost protocol's per session data size

Parameters

wsi	a connection with the protocol to change
new_size	the new size of the per session data size for the protocol

Returns user_space for the wsi, after allocating

This should not be used except to initalize a vhost protocol's per session data size one time, before any connections are accepted.

Sometimes the protocol wraps another protocol and needs to discover and set its per session data size at runtime.

lws_finalize_startup()

LWS_VISIBLE LWS_EXTERN int lws_finalize_startup

(

struct lws_context *

context

)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_finalize_startup() - drop initial process privileges

Parameters

context

lws context

This is called after the end of the vhost protocol initializations, but you may choose to call it earlier

lws_get_protocol()

LWS_VISIBLE LWS_EXTERN const struct lws_protocols* lws_get_protocol

(

struct lws *

wsi

)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_get_protocol() - Returns a protocol pointer from a websocket connection.

Parameters

wsi	pointer to struct websocket you want to know the protocol of

 Some apis can act on all live connections of a given protocol,
 this is how you can get a pointer to the active protocol if needed.

lws_plugins_destroy()

LWS_VISIBLE LWS_EXTERN int lws_plugins_destroy	(	struct lws_plugin **	pplugin,
		each_plugin_cb_t	each,
		void *	each_user
	)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_plugins_destroy() - dynamically unload list of plugins

Parameters

pplugin	pointer to linked-list for this kind of plugin
each	NULL, or each_plugin_cb_t callback for each instantiated plugin
each_user	pointer passed to each callback

Allows you to destroy a class of plugins from a specified linked-list created by a call to lws_plugins_init().

The each callback allows you to deinit each inistantiated callback and pass a pointer each_user to it, just before its footprint is destroyed.

lws_plugins_init()

LWS_VISIBLE LWS_EXTERN int lws_plugins_init	(	struct lws_plugin **	pplugin,
		const char *const *	d,
		const char *	_class,
		const char *	filter,
		each_plugin_cb_t	each,
		void *	each_user
	)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_plugins_init() - dynamically load plugins of matching class from dirs

Parameters

pplugin	pointer to linked-list for this kind of plugin
d	array of directory paths to look in
_class	class string that plugin must declare
filter	NULL, or a string that must appear after the third char of the plugin filename
each	NULL, or each_plugin_cb_t callback for each instantiated plugin
each_user	pointer passed to each callback

Allows you to instantiate a class of plugins to a specified linked-list. The each callback allows you to init each inistantiated callback and pass a pointer each_user to it.

To take down the plugins, pass a pointer to the linked-list head to lws_plugins_destroy.

This is used for lws protocol plugins but you can define your own plugin class name like "mypluginclass", declare it in your plugin headers, and load your own plugins to your own list using this api the same way.

lws_protocol_get()

LWS_VISIBLE LWS_EXTERN const struct lws_protocols* lws_protocol_get

(

struct lws *

wsi

)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_protocol_get() - deprecated: use lws_get_protocol

lws_protocol_vh_priv_get()

LWS_VISIBLE LWS_EXTERN void* lws_protocol_vh_priv_get	(	struct lws_vhost *	vhost,
		const struct lws_protocols *	prot
	)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_protocol_vh_priv_get() - retreive a protocol's per-vhost storage

Parameters

vhost	vhost the instance is related to
prot	protocol the instance is related to

Recover a pointer to the allocated per-vhost storage for the protocol created by lws_protocol_vh_priv_zalloc() earlier

lws_protocol_vh_priv_zalloc()

LWS_VISIBLE LWS_EXTERN void* lws_protocol_vh_priv_zalloc	(	struct lws_vhost *	vhost,
		const struct lws_protocols *	prot,
		int	size
	)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_protocol_vh_priv_zalloc() - Allocate and zero down a protocol's per-vhost storage

Parameters

vhost	vhost the instance is related to
prot	protocol the instance is related to
size	bytes to allocate

Protocols often find it useful to allocate a per-vhost struct, this is a helper to be called in the per-vhost init LWS_CALLBACK_PROTOCOL_INIT

lws_pvo_get_str()

LWS_VISIBLE LWS_EXTERN int lws_pvo_get_str	(	void *	in,
		const char *	name,
		const char **	result
	)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_pvo_get_str() - retreive a string pvo value

Parameters

in	the first pvo in the linked-list
name	the name of the pvo to return if found
result	pointer to a const char * to get the result if any

Returns 0 if found and *result set, or nonzero if not found

lws_pvo_search()

LWS_VISIBLE LWS_EXTERN const struct lws_protocol_vhost_options* lws_pvo_search	(	const struct lws_protocol_vhost_options *	pvo,
		const char *	name
	)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_pvo_search() - helper to find a named pvo in a linked-list

Parameters

pvo	the first pvo in the linked-list
name	the name of the pvo to return if found

Returns NULL, or a pointer to the name pvo in the linked-list

lws_vhd_find_by_pvo()

LWS_VISIBLE LWS_EXTERN void* lws_vhd_find_by_pvo	(	struct lws_context *	cx,
		const char *	protname,
		const char *	pvo_name,
		const char *	pvo_value
	)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_vhd_find_by_pvo() - find a partner vhd

Parameters

cx	the lws_context
protname	the name of the lws_protocol the vhd belongs to
pvo_name	the name of a pvo that must exist bound to the vhd
pvo_value	the required value of the named pvo

This allows architectures with multiple protocols bound together to cleanly discover partner protocol instances even on completely different vhosts. For example, a proxy may consist of two protocols listening on different vhosts, and there may be multiple instances of the proxy in the same process. It's desirable that each side of the proxy is an independent protocol that can be freely bound to any vhost, eg, allowing Unix Domain to tls / h2 proxying, or each side bound to different network interfaces for localhost-only visibility on one side, using existing vhost management.

That leaves the problem that the two sides have to find each other and bind at runtime. This api allows each side to specify the protocol name, and a common pvo name and pvo value that indicates the two sides belong together, and search through all the instantiated vhost-protocols looking for a match. If found, the private allocation (aka "vhd" of the match is returned). NULL is returned on no match.

Since this can only succeed when called by the last of the two protocols to be instantiated, both sides should call it and handle NULL gracefully, since it may mean that they were first and their partner vhsot-protocol has not been instantiated yet.

lws_vhost_name_to_protocol()

LWS_VISIBLE LWS_EXTERN const struct lws_protocols* lws_vhost_name_to_protocol	(	struct lws_vhost *	vh,
		const char *	name
	)

#include <include/libwebsockets/lws-protocols-plugins.h>

lws_vhost_name_to_protocol() - get vhost's protocol object from its name

Parameters

vh	vhost to search
name	protocol name

Returns NULL or a pointer to the vhost's protocol of the requested name