Helps keeping caches up to date. More...

Collaboration diagram for Manager:

Functions
int	nl_cache_mngr_alloc (struct nl_sock sk, int protocol, int flags, struct nl_cache_mngr *result)
	Allocate new cache manager. More...

int	nl_cache_mngr_add (struct nl_cache_mngr mngr, const char name, change_func_t cb, struct nl_cache **result)
	Add cache responsibility to cache manager. More...

int	nl_cache_mngr_get_fd (struct nl_cache_mngr *mngr)
	Get file descriptor. More...

int	nl_cache_mngr_poll (struct nl_cache_mngr *mngr, int timeout)
	Check for event notifications. More...

int	nl_cache_mngr_data_ready (struct nl_cache_mngr *mngr)
	Receive available event notifications. More...

void	nl_cache_mngr_free (struct nl_cache_mngr *mngr)
	Free cache manager and all caches. More...

Detailed Description

Helps keeping caches up to date.

The purpose of a cache manager is to keep track of caches and automatically receive event notifications to keep the caches up to date with the kernel state. Each manager has exactly one netlink socket assigned which limits the scope of each manager to exactly one netlink family. Therefore all caches committed to a manager must be part of the same netlink family. Due to the nature of a manager, it is not possible to have a cache maintain two instances of the same cache type. The socket is subscribed to the event notification group of each cache and also put into non-blocking mode. Functions exist to poll() on the socket to wait for new events to be received.

App       libnl                        Kernel
       |                            |
           +-----------------+        [ notification, link change ]
       |   |  Cache Manager  |      | [   (IFF_UP | IFF_RUNNING)  ]
           |                 |                |
       |   |   +------------+|      |         |  [ notification, new addr ]
   <-------|---| route/link |<-------(async)--+  [  10.0.1.1/32 dev eth1  ]
       |   |   +------------+|      |                      |
           |   +------------+|                             |
   <---|---|---| route/addr |<------|-(async)--------------+
           |   +------------+|
       |   |   +------------+|      |
   <-------|---| ...        ||
       |   |   +------------+|      |
           +-----------------+
       |                            |

1) Creating a new cache manager: struct nl_cache_mngr *mngr;

// Allocate a new cache manager for RTNETLINK and automatically

// provide the caches added to the manager.

mngr = nl_cache_mngr_alloc(NETLINK_ROUTE, NL_AUTO_PROVIDE);

2) Keep track of a cache: struct nl_cache *cache;

// Create a new cache for links/interfaces and ask the manager to

// keep it up to date for us. This will trigger a full dump request

// to initially fill the cache.

cache = nl_cache_mngr_add(mngr, "route/link");

3) Make the manager receive updates: // Give the manager the ability to receive updates, will call poll()

// with a timeout of 5 seconds.

if (nl_cache_mngr_poll(mngr, 5000) > 0) {

// Manager received at least one update, dump cache?

nl_cache_dump(cache, ...);

}

4) Release cache manager: nl_cache_mngr_free(mngr);

Function Documentation

int nl_cache_mngr_add	(	struct nl_cache_mngr *	mngr,
		const char *	name,
		change_func_t	cb,
		struct nl_cache **	result
	)

Add cache responsibility to cache manager.

mngr Cache manager.
name Name of cache to keep track of
cb Function to be called upon changes.
result Pointer to store added cache.

Allocates a new cache of the specified type and adds it to the manager. The operation will trigger a full dump request from the kernel to initially fill the contents of the cache. The manager will subscribe to the notification group of the cache to keep track of any further changes.

Returns: 0 on success or a negative error code.

References nl_af_group::ag_group, nl_cache::c_ops, nl_cache_assoc::ca_cache, nl_cache_assoc::ca_change, nl_cache_mngr::cm_assocs, nl_cache_mngr::cm_flags, nl_cache_mngr::cm_handle, nl_cache_mngr::cm_nassocs, nl_cache_mngr::cm_protocol, nl_cache_ops::co_groups, nl_cache_ops::co_protocol, NL_AUTO_PROVIDE, nl_cache_alloc(), nl_cache_free(), nl_cache_mngt_provide(), nl_cache_ops_lookup(), nl_cache_refill(), NL_DBG, nl_socket_add_membership(), nl_socket_drop_membership(), NLE_EXIST, NLE_NOCACHE, NLE_NOMEM, NLE_OPNOTSUPP, NLE_PROTO_MISMATCH, and NULL.

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int nl_cache_mngr_alloc	(	struct nl_sock *	sk,
		int	protocol,
		int	flags,
		struct nl_cache_mngr **	result
	)

Allocate new cache manager.

sk Netlink socket.
protocol Netlink Protocol this manager is used for
flags Flags

Returns: Newly allocated cache manager or NULL on failure.

References BUG, nl_cache_mngr::cm_assocs, nl_cache_mngr::cm_flags, nl_cache_mngr::cm_handle, nl_cache_mngr::cm_nassocs, nl_cache_mngr::cm_protocol, flags, nl_cache_mngr_free(), NL_CB_CUSTOM, NL_CB_VALID, nl_connect(), NL_DBG, nl_socket_disable_seq_check(), nl_socket_modify_cb(), nl_socket_set_nonblocking(), NLE_NOMEM, and NULL.

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int nl_cache_mngr_data_ready ( struct nl_cache_mngr * mngr )

Receive available event notifications.

mngr Cache manager

This function can be called if the socket associated to the manager contains updates to be received. This function should not be used if nl_cache_mngr_poll() is used.

Returns: A positive value if at least one update was handled, 0 for none, or a negative error code.

References nl_cache_mngr::cm_handle, and nl_recvmsgs_default().

Referenced by nl_cache_mngr_poll().

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void nl_cache_mngr_free ( struct nl_cache_mngr * mngr )

Free cache manager and all caches.

mngr Cache manager.

Release all resources after usage of a cache manager.

References nl_cache_assoc::ca_cache, nl_cache_mngr::cm_assocs, nl_cache_mngr::cm_handle, nl_cache_mngr::cm_nassocs, nl_cache_free(), nl_close(), and NL_DBG.

Referenced by nl_cache_mngr_alloc().

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int nl_cache_mngr_get_fd ( struct nl_cache_mngr * mngr )

Get file descriptor.

mngr Cache Manager

Get the file descriptor of the socket associated to the manager. This can be used to change socket options or monitor activity using poll()/select().

References nl_cache_mngr::cm_handle, and nl_socket_get_fd().

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int nl_cache_mngr_poll	(	struct nl_cache_mngr *	mngr,
		int	timeout
	)

Check for event notifications.

mngr Cache Manager
timeout Upper limit poll() will block, in milliseconds.

Causes poll() to be called to check for new event notifications being available. Automatically receives and handles available notifications.

This functionally is ideally called regularly during an idle period.

Returns: A positive value if at least one update was handled, 0 for none, or a negative error code.

References nl_cache_mngr::cm_handle, nl_cache_mngr_data_ready(), NL_DBG, nl_socket_get_fd(), and nl_syserr2nlerr().

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