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Andy Green bce1f01370 lws_state and system state

Introduce a generic lws_state object with notification handlers
that may be registered in a chain.

Implement one of those in the context to manage the "system state".

Allow other pieces of lws and user code to register notification
handlers on a context list.  Handlers can object to or take over
responsibility to move forward and retry system state changes if
they know that some dependent action must succeed first.

For example if the system time is invalid, we cannot move on to
a state where anything can do tls until that has been corrected.

2019-09-22 09:35:07 -07:00

3.2 KiB

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`lws_system`

See include/libwebsockets/lws-system.h for function and object prototypes.

System integration api

lws_system allows you to set a system_ops struct at context creation time, which can write up some function callbacks for system integration. The goal is the user code calls these by getting the ops struct pointer from the context using lws_system_get_ops(context) or lws_system_get_info() and so does not spread system dependencies around the user code.

typedef struct lws_system_ops {
	int (*get_info)(lws_system_item_t i, lws_system_arg_t *arg);
	int (*reboot)(void);
	int (*set_clock)(lws_usec_t us);
} lws_system_ops_t;

`get_info`

This allows the user code to query some common system values without introducing any system dependencies in the code itself. The defined item numbers are

Item	Meaning
`LWS_SYSI_HRS_DEVICE_MODEL`	String describing device model
`LWS_SYSI_HRS_DEVICE_SERIAL`	String for the device serial number
`LWS_SYSI_HRS_FIRMWARE_VERSION`	String describing the current firmware version
`LWS_SYSI_HRS_NTP_SERVER`	String with the ntp server address (defaults to pool.ntp.org)

`reboot`

Reboots the device

`set_clock`

Set the system clock to us-resolution Unix time in seconds

System state and notifiers

Lws implements a state in the context that reflects the readiness of the system for various steps leading up to normal operation. By default it acts in a backwards-compatible way and directly reaches the OPERATIONAL state just after the context is created.

However other pieces of lws, and user, code may define notification handlers that get called back when the state changes incrementally, and may veto or delay the changes until work necessary for the new state has completed asynchronously.

The generic states defined are:

State	Meaning
`LWS_SYSTATE_CONTEXT_CREATED`	The context was just created.
`LWS_SYSTATE_INITIALIZED`	The vhost protocols have been initialized
`LWS_SYSTATE_IFACE_COLDPLUG`	Existing network interfaces have been iterated
`LWS_SYSTATE_DHCP`	Network identity is available
`LWS_SYSTATE_TIME_VALID`	The system knows the time
`LWS_SYSTATE_POLICY_VALID`	If the system needs information about how to act from the net, it has it
`LWS_SYSTATE_REGISTERED`	The device has a registered identity
`LWS_SYSTATE_AUTH1`	The device identity has produced a time-limited access token
`LWS_SYSTATE_AUTH2`	Optional second access token for different services
`LWS_SYSTATE_OPERATIONAL`	The system is ready for user code to work normally
`LWS_SYSTATE_POLICY_INVALID`	All connections are being dropped because policy information is changing. It will transition back to `LWS_SYSTATE_INITIALIZED` and onward to `OPERATIONAL` again afterwards with the new policy

Inserting a notifier

You should create an object lws_system_notify_link_t in non-const memory and zero it down. Set the notify_cb member and the name member and then register it using either lws_system_reg_notifier() or the .register_notifier_list member of the context creation info struct to make sure it will exist early enough to see all events. The context creation info method takes a list of pointers to notify_link structs ending with a NULL entry.

3.2 KiB Raw Blame History

lws_system