libwebsockets
Lightweight C library for HTML5 websockets
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_protocolslws_vhost_name_to_protocol (struct lws_vhost *vh, const char *name)
 
LWS_VISIBLE LWS_EXTERN const struct lws_protocolslws_get_protocol (struct lws *wsi)
 
LWS_VISIBLE LWS_EXTERN const struct lws_protocolslws_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_optionslws_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
wsia connection with the protocol to change
new_sizethe 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
contextlws 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
wsipointer 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
ppluginpointer to linked-list for this kind of plugin
eachNULL, or each_plugin_cb_t callback for each instantiated plugin
each_userpointer 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
ppluginpointer to linked-list for this kind of plugin
darray of directory paths to look in
_classclass string that plugin must declare
filterNULL, or a string that must appear after the third char of the plugin filename
eachNULL, or each_plugin_cb_t callback for each instantiated plugin
each_userpointer 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
vhostvhost the instance is related to
protprotocol 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
vhostvhost the instance is related to
protprotocol the instance is related to
sizebytes 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
inthe first pvo in the linked-list
namethe name of the pvo to return if found
resultpointer 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
pvothe first pvo in the linked-list
namethe 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
cxthe lws_context
protnamethe name of the lws_protocol the vhd belongs to
pvo_namethe name of a pvo that must exist bound to the vhd
pvo_valuethe 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
vhvhost to search
nameprotocol name

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