Tor  0.4.4.0-alpha-dev
Data Fields
subsys_fns_t Struct Reference

#include <subsys.h>

Data Fields

const char * name
 
bool supported
 
int level
 
int(* initialize )(void)
 
int(* add_pubsub )(struct pubsub_connector_t *)
 
void(* prefork )(void)
 
void(* postfork )(void)
 
void(* thread_cleanup )(void)
 
void(* shutdown )(void)
 
const struct config_format_toptions_format
 
const struct config_format_tstate_format
 
int(* set_options )(void *)
 
int(* set_state )(void *)
 
int(* flush_state )(void *)
 

Detailed Description

A subsystem is a part of Tor that is initialized, shut down, configured, and connected to other parts of Tor.

All callbacks are optional – if a callback is set to NULL, the subsystem manager will treat it as a no-op.

You should use c99 named-field initializers with this structure, for readability and safety. (There are a lot of functions here, all of them optional, and many of them with similar signatures.)

See Initialization and shutdown for more information about initialization and shutdown in Tor.

To make a new subsystem, you declare a const instance of this type, and include it on the list in subsystem_list.c. The code that manages these subsystems is in subsysmgr.c.

Definition at line 37 of file subsys.h.

Field Documentation

◆ add_pubsub

int(* add_pubsub) (struct pubsub_connector_t *)

Connect a subsystem to the message dispatch system.

This function should use the macros in lib/pubsub to register a set of messages that this subsystem may publish, and may subscribe to.

See pubsub_macros.h for more information, and for examples.

Definition at line 80 of file subsys.h.

◆ flush_state

int(* flush_state) (void *)

Update any information that needs to be stored in the provided state object (as defined by state_format). Return 0 on success, -1 on failure.

The object provided here will be the same one as provided earlier to set_state(). This method is called when we are about to save the state to disk.

Definition at line 187 of file subsys.h.

◆ initialize

int(* initialize) (void)

Initialize any global components of this subsystem.

This function MAY rely on any lower-level subsystem being initialized.

This function MUST NOT rely on any runtime configuration information; it is only for global state or pre-configuration state.

(If you need to do any setup that depends on configuration, you'll need to declare a configuration callback instead. (Not yet designed))

This function MUST NOT have any parts that can fail.

Definition at line 70 of file subsys.h.

◆ level

int level

The 'initialization level' for the subsystem. It should run from -100 through +100. The subsystems are initialized from lowest level to highest, and shut down from highest level to lowest.

Definition at line 55 of file subsys.h.

◆ name

const char* name

The name of this subsystem. It should be a programmer-readable identifier.

Definition at line 42 of file subsys.h.

◆ options_format

const struct config_format_t* options_format

A config_format_t describing all of the torrc fields owned by this subsystem.

This object, if present, is registered in a confmgr_t for Tor's options, and used to parse option fields from the command line and torrc file.

Definition at line 138 of file subsys.h.

◆ postfork

void(* postfork) (void)

Perform any necessary post-fork setup. This function may not fail.

On Windows (and any other platforms without fork()), this function will never be invoked. Otherwise it is used when we are about to start running as a background daemon, or when we are about to run a unit test in a subprocess. Unlike the subsys_fns_t.prefork callback, it is run from the child process.

Note that we do not invoke this function when the child process's only purpose is to call exec() and run another program.

Definition at line 108 of file subsys.h.

◆ prefork

void(* prefork) (void)

Perform any necessary pre-fork cleanup. This function may not fail.

On Windows (and any other platforms without fork()), this function will never be invoked. Otherwise it is used when we are about to start running as a background daemon, or when we are about to run a unit test in a subprocess. Unlike the subsys_fns_t.postfork callback, it is run from the parent process.

Note that we do not invoke this function when the child process's only purpose is to call exec() and run another program.

Definition at line 94 of file subsys.h.

◆ set_options

int(* set_options) (void *)

Receive an options object as defined by options_format. Return 0 on success, -1 on failure.

It is safe to store the pointer to the object until set_options() is called again.

This function is only called after all the validation code defined by subsys_fns_t.options_format has passed.

Definition at line 159 of file subsys.h.

◆ set_state

int(* set_state) (void *)

Receive a state object as defined by state_format. Return 0 on success, -1 on failure.

It is safe to store the pointer to the object; set_state() is only called on startup.

This function is only called after all the validation code defined by subsys_fns_t.state_format has passed.

This function will only be called once per invocation of Tor, since Tor does not reload its state while it is running.

Definition at line 177 of file subsys.h.

◆ shutdown

void(* shutdown) (void)

Free all resources held by this subsystem.

This function is not allowed to fail.

Subsystems are shut down when Tor is about to exit or return control to an embedding program. This callback must return the process to a state such that subsys_fns_t.init will succeed if invoked again.

Definition at line 129 of file subsys.h.

◆ state_format

const struct config_format_t* state_format

A config_format_t describing all of the DataDir/state fields owned by this subsystem.

This object, if present, is registered in a confmgr_t for Tor's state, and used to parse state fields from the DataDir/state file.

Definition at line 147 of file subsys.h.

◆ supported

bool supported

Whether this subsystem is supported – that is, whether it is compiled into Tor. For most subsystems, this should be true.

Definition at line 48 of file subsys.h.

◆ thread_cleanup

void(* thread_cleanup) (void)

Free any thread-local resources held by this subsystem. Called before the thread exits.

This function is not allowed to fail.

Bug:
Note that this callback is currently buggy: See ticket 32103.

Definition at line 118 of file subsys.h.


The documentation for this struct was generated from the following file: