Network Management
Overview
The Network Management APIs allow applications, as well as network layer code itself, to call defined network routines at any level in the IP stack, or receive notifications on relevant network events. For example, by using these APIs, application code can request a scan be done on a Wi-Fi- or Bluetooth-based network interface, or request notification if a network interface IP address changes.
The Network Management API implementation is designed to save memory
by eliminating code at build time for management routines that are not
used. Distinct and statically defined APIs for network management
procedures are not used. Instead, defined procedure handlers are
registered by using a NET_MGMT_REGISTER_REQUEST_HANDLER
macro. Procedure requests are done through a single net_mgmt() API
that invokes the registered handler for the corresponding request.
The current implementation is experimental and may change and improve in future releases.
Requesting a defined procedure
All network management requests are of the form
net_mgmt(mgmt_request, ...). The mgmt_request parameter is a bit
mask that tells which stack layer is targeted, if a net_if object is
implied, and the specific management procedure being requested. The
available procedure requests depend on what has been implemented in
the stack.
To avoid extra cost, all net_mgmt() calls are direct. Though this
may change in a future release, it will not affect the users of this
function.
Listening to network events
You can receive notifications on network events by registering a callback function and specifying a set of events used to filter when your callback is invoked. The callback will have to be unique for a pair of layer and code, whereas on the command part it will be a mask of events.
At runtime two functions are available, net_mgmt_add_event_callback()
for registering the callback function, and net_mgmt_del_event_callback()
for unregistering a callback. A helper function,
net_mgmt_init_event_callback(), can
be used to ease the initialization of the callback structure.
Additionally NET_MGMT_REGISTER_EVENT_HANDLER can be used to
register a callback handler at compile time.
When an event occurs that matches a callback’s event set, the associated callback function is invoked with the actual event code. This makes it possible for different events to be handled by the same callback function, if desired.
Warning
Event set filtering allows false positives for events that have the same
layer and layer code. A callback handler function must check
the event code (passed as an argument) against the specific network
events it will handle, regardless of how many events were in the
set passed to net_mgmt_init_event_callback().
Note that in order to receive events from multiple layers, one must have multiple listeners registered, one for each layer being listened. The callback handler function can be shared between different layer events.
(False positives can occur for events which have the same layer and layer code.)
An example follows.
/*
* Set of events to handle.
* See e.g. include/net/net_event.h for some NET_EVENT_xxx values.
*/
#define EVENT_IFACE_SET (NET_EVENT_IF_xxx | NET_EVENT_IF_yyy)
#define EVENT_IPV4_SET (NET_EVENT_IPV4_xxx | NET_EVENT_IPV4_yyy)
struct net_mgmt_event_callback iface_callback;
struct net_mgmt_event_callback ipv4_callback;
void callback_handler(struct net_mgmt_event_callback *cb,
uint32_t mgmt_event,
struct net_if *iface)
{
if (mgmt_event == NET_EVENT_IF_xxx) {
/* Handle NET_EVENT_IF_xxx */
} else if (mgmt_event == NET_EVENT_IF_yyy) {
/* Handle NET_EVENT_IF_yyy */
} else if (mgmt_event == NET_EVENT_IPV4_xxx) {
/* Handle NET_EVENT_IPV4_xxx */
} else if (mgmt_event == NET_EVENT_IPV4_yyy) {
/* Handle NET_EVENT_IPV4_yyy */
} else {
/* Spurious (false positive) invocation. */
}
}
void register_cb(void)
{
net_mgmt_init_event_callback(&iface_callback, callback_handler,
EVENT_IFACE_SET);
net_mgmt_init_event_callback(&ipv4_callback, callback_handler,
EVENT_IPV4_SET);
net_mgmt_add_event_callback(&iface_callback);
net_mgmt_add_event_callback(&ipv4_callback);
}
Or similarly using NET_MGMT_REGISTER_EVENT_HANDLER.
Note
The info and info_length arguments are only usable if
CONFIG_NET_MGMT_EVENT_INFO is enabled. Otherwise these are
NULL and zero.
/*
* Set of events to handle.
*/
#define EVENT_IFACE_SET (NET_EVENT_IF_xxx | NET_EVENT_IF_yyy)
#define EVENT_IPV4_SET (NET_EVENT_IPV4_xxx | NET_EVENT_IPV4_yyy)
static void event_handler(uint32_t mgmt_event, struct net_if *iface,
void *info, size_t info_length,
void *user_data)
{
if (mgmt_event == NET_EVENT_IF_xxx) {
/* Handle NET_EVENT_IF_xxx */
} else if (mgmt_event == NET_EVENT_IF_yyy) {
/* Handle NET_EVENT_IF_yyy */
} else if (mgmt_event == NET_EVENT_IPV4_xxx) {
/* Handle NET_EVENT_IPV4_xxx */
} else if (mgmt_event == NET_EVENT_IPV4_yyy) {
/* Handle NET_EVENT_IPV4_yyy */
} else {
/* Spurious (false positive) invocation. */
}
}
NET_MGMT_REGISTER_EVENT_HANDLER(iface_event_handler, EVENT_IFACE_SET,
event_handler, NULL);
NET_MGMT_REGISTER_EVENT_HANDLER(ipv4_event_handler, EVENT_IPV4_SET,
event_handler, NULL);
See include/zephyr/net/net_event.h for available generic core events that can be listened to.
Defining a network management procedure
You can provide additional management procedures specific to your stack implementation by defining a handler and registering it with an associated mgmt_request code.
Management request code are defined in relevant places depending on the targeted layer or eventually, if l2 is the layer, on the technology as well. For instance, all IP layer management request code will be found in the include/zephyr/net/net_event.h header file. But in case of an L2 technology, let’s say Ethernet, these would be found in include/zephyr/net/ethernet.h
You define your handler modeled with this signature:
static int your_handler(uint32_t mgmt_event, struct net_if *iface,
void *data, size_t len);
and then register it with an associated mgmt_request code:
NET_MGMT_REGISTER_REQUEST_HANDLER(<mgmt_request code>, your_handler);
This new management procedure could then be called by using:
net_mgmt(<mgmt_request code>, ...);
Signaling a network event
You can signal a specific network event using the net_mgmt_event_notify()
function and provide the network event code. See
include/zephyr/net/net_mgmt.h for details. As for the management request
code, event code can be also found on specific L2 technology mgmt headers,
for example include/zephyr/net/ieee802154_mgmt.h would be the right place if
802.15.4 L2 is the technology one wants to listen to events.