libnl  3.2.3
Manager

Helps keeping caches up to date. More...

Functions

int nl_cache_mngr_alloc (struct nl_sock *sk, int protocol, int flags, struct nl_cache_mngr **result)
 Allocate new cache manager.
int nl_cache_mngr_add (struct nl_cache_mngr *mngr, const char *name, change_func_t cb, void *data, struct nl_cache **result)
 Add cache responsibility to cache manager.
int nl_cache_mngr_get_fd (struct nl_cache_mngr *mngr)
 Get file descriptor.
int nl_cache_mngr_poll (struct nl_cache_mngr *mngr, int timeout)
 Check for event notifications.
int nl_cache_mngr_data_ready (struct nl_cache_mngr *mngr)
 Receive available event notifications.
void nl_cache_mngr_free (struct nl_cache_mngr *mngr)
 Free cache manager and all caches.

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

Function Documentation

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

Allocate new cache manager.

Parameters:
skNetlink socket.
protocolNetlink Protocol this manager is used for
flagsFlags
resultResult pointer
Returns:
0 on success or a negative error code.

Definition at line 156 of file cache_mngr.c.

References nl_cache_mngr_free(), NL_CB_CUSTOM, NL_CB_VALID, nl_connect(), nl_socket_disable_seq_check(), nl_socket_modify_cb(), and nl_socket_set_nonblocking().

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

Add cache responsibility to cache manager.

Parameters:
mngrCache manager.
nameName of cache to keep track of
cbFunction to be called upon changes.
dataArgument passed on to change callback
resultPointer 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.

Definition at line 217 of file cache_mngr.c.

References nl_af_group::ag_group, nl_cache_ops::co_groups, nl_cache_ops::co_protocol, nl_cache_alloc(), nl_cache_free(), nl_cache_mngt_provide(), nl_cache_ops_lookup(), and nl_cache_refill().

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int nl_cache_mngr_get_fd ( struct nl_cache_mngr *  mngr)

Get file descriptor.

Parameters:
mngrCache 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().

Definition at line 303 of file cache_mngr.c.

int nl_cache_mngr_poll ( struct nl_cache_mngr *  mngr,
int  timeout 
)

Check for event notifications.

Parameters:
mngrCache Manager
timeoutUpper 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.

Definition at line 323 of file cache_mngr.c.

References nl_cache_mngr_data_ready().

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int nl_cache_mngr_data_ready ( struct nl_cache_mngr *  mngr)

Receive available event notifications.

Parameters:
mngrCache 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.

Definition at line 354 of file cache_mngr.c.

References 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.

Parameters:
mngrCache manager.

Release all resources after usage of a cache manager.

Definition at line 371 of file cache_mngr.c.

References nl_cache_free(), nl_cache_mngt_unprovide(), and nl_close().

Referenced by nl_cache_mngr_alloc().

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