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* lib/cache_mngr.c Cache Manager
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation version 2.1
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* Copyright (c) 2003-2008 Thomas Graf <tgraf@suug.ch>
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* @defgroup cache_mngr Manager
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* @brief Helps keeping caches up to date.
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* The purpose of a cache manager is to keep track of caches and
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* automatically receive event notifications to keep the caches
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* up to date with the kernel state. Each manager has exactly one
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* netlink socket assigned which limits the scope of each manager
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* to exactly one netlink family. Therefore all caches committed
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* to a manager must be part of the same netlink family. Due to the
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* nature of a manager, it is not possible to have a cache maintain
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* two instances of the same cache type. The socket is subscribed
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* to the event notification group of each cache and also put into
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* non-blocking mode. Functions exist to poll() on the socket to
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* wait for new events to be received.
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* +-----------------+ [ notification, link change ]
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* | | Cache Manager | | [ (IFF_UP | IFF_RUNNING) ]
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* | | +------------+| | | [ notification, new addr ]
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* <-------|---| route/link |<-------(async)--+ [ 10.0.1.1/32 dev eth1 ]
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* | | +------------+| | |
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* <---|---|---| route/addr |<------|-(async)--------------+
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* | | +------------+| |
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* <-------|---| ... ||
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* | | +------------+| |
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* @par 1) Creating a new cache manager
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* struct nl_cache_mngr *mngr;
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* // Allocate a new cache manager for RTNETLINK and automatically
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* // provide the caches added to the manager.
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* mngr = nl_cache_mngr_alloc(NETLINK_ROUTE, NL_AUTO_PROVIDE);
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* @par 2) Keep track of a cache
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* struct nl_cache *cache;
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* // Create a new cache for links/interfaces and ask the manager to
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* // keep it up to date for us. This will trigger a full dump request
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* // to initially fill the cache.
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* cache = nl_cache_mngr_add(mngr, "route/link");
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* @par 3) Make the manager receive updates
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* // Give the manager the ability to receive updates, will call poll()
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* // with a timeout of 5 seconds.
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* if (nl_cache_mngr_poll(mngr, 5000) > 0) {
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* // Manager received at least one update, dump cache?
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* nl_cache_dump(cache, ...);
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* @par 4) Release cache manager
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* nl_cache_mngr_free(mngr);
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#include <netlink-local.h>
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#include <netlink/netlink.h>
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#include <netlink/cache.h>
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#include <netlink/utils.h>
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static int include_cb(struct nl_object *obj, struct nl_parser_param *p)
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struct nl_cache_assoc *ca = p->pp_arg;
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NL_DBG(2, "Including object %p into cache %p\n", obj, ca->ca_cache);
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nl_object_dump(obj, &nl_debug_dp);
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return nl_cache_include(ca->ca_cache, obj, ca->ca_change, ca->ca_change_data);
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static int event_input(struct nl_msg *msg, void *arg)
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struct nl_cache_mngr *mngr = arg;
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int protocol = nlmsg_get_proto(msg);
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int type = nlmsg_hdr(msg)->nlmsg_type;
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struct nl_cache_ops *ops;
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struct nl_parser_param p = {
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NL_DBG(2, "Cache manager %p, handling new message %p as event\n",
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nl_msg_dump(msg, stderr);
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if (mngr->cm_protocol != protocol)
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for (i = 0; i < mngr->cm_nassocs; i++) {
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if (mngr->cm_assocs[i].ca_cache) {
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ops = mngr->cm_assocs[i].ca_cache->c_ops;
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for (n = 0; ops->co_msgtypes[n].mt_id >= 0; n++)
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if (ops->co_msgtypes[n].mt_id == type)
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NL_DBG(2, "Associated message %p to cache %p\n",
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msg, mngr->cm_assocs[i].ca_cache);
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p.pp_arg = &mngr->cm_assocs[i];
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return nl_cache_parse(ops, NULL, nlmsg_hdr(msg), &p);
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* Allocate new cache manager
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* @arg sk Netlink socket.
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* @arg protocol Netlink Protocol this manager is used for
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* @return Newly allocated cache manager or NULL on failure.
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int nl_cache_mngr_alloc(struct nl_sock *sk, int protocol, int flags,
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struct nl_cache_mngr **result)
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struct nl_cache_mngr *mngr;
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int err = -NLE_NOMEM;
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mngr = calloc(1, sizeof(*mngr));
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mngr->cm_handle = sk;
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mngr->cm_nassocs = 32;
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mngr->cm_protocol = protocol;
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mngr->cm_flags = flags;
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mngr->cm_assocs = calloc(mngr->cm_nassocs,
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sizeof(struct nl_cache_assoc));
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if (!mngr->cm_assocs)
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nl_socket_modify_cb(mngr->cm_handle, NL_CB_VALID, NL_CB_CUSTOM,
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/* Required to receive async event notifications */
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nl_socket_disable_seq_check(mngr->cm_handle);
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if ((err = nl_connect(mngr->cm_handle, protocol) < 0))
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if ((err = nl_socket_set_nonblocking(mngr->cm_handle) < 0))
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NL_DBG(1, "Allocated cache manager %p, protocol %d, %d caches\n",
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mngr, protocol, mngr->cm_nassocs);
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nl_cache_mngr_free(mngr);
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* Add cache responsibility to cache manager
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* @arg mngr Cache manager.
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* @arg name Name of cache to keep track of
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* @arg cb Function to be called upon changes.
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* @arg result Pointer to store added cache.
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* Allocates a new cache of the specified type and adds it to the manager.
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* The operation will trigger a full dump request from the kernel to
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* initially fill the contents of the cache. The manager will subscribe
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* to the notification group of the cache to keep track of any further
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* @return 0 on success or a negative error code.
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int nl_cache_mngr_add(struct nl_cache_mngr *mngr, const char *name,
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change_func_t cb, void *data, struct nl_cache **result)
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struct nl_cache_ops *ops;
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struct nl_cache *cache;
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struct nl_af_group *grp;
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ops = nl_cache_ops_lookup(name);
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if (ops->co_protocol != mngr->cm_protocol)
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return -NLE_PROTO_MISMATCH;
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if (ops->co_groups == NULL)
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return -NLE_OPNOTSUPP;
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for (i = 0; i < mngr->cm_nassocs; i++)
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if (mngr->cm_assocs[i].ca_cache &&
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mngr->cm_assocs[i].ca_cache->c_ops == ops)
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for (i = 0; i < mngr->cm_nassocs; i++)
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if (!mngr->cm_assocs[i].ca_cache)
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if (i >= mngr->cm_nassocs) {
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mngr->cm_nassocs += 16;
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mngr->cm_assocs = realloc(mngr->cm_assocs,
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sizeof(struct nl_cache_assoc));
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if (mngr->cm_assocs == NULL)
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NL_DBG(1, "Increased capacity of cache manager %p " \
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"to %d\n", mngr, mngr->cm_nassocs);
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cache = nl_cache_alloc(ops);
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for (grp = ops->co_groups; grp->ag_group; grp++) {
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err = nl_socket_add_membership(mngr->cm_handle, grp->ag_group);
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goto errout_free_cache;
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err = nl_cache_refill(mngr->cm_handle, cache);
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goto errout_drop_membership;
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mngr->cm_assocs[i].ca_cache = cache;
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mngr->cm_assocs[i].ca_change = cb;
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mngr->cm_assocs[i].ca_change_data = data;
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if (mngr->cm_flags & NL_AUTO_PROVIDE)
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nl_cache_mngt_provide(cache);
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NL_DBG(1, "Added cache %p <%s> to cache manager %p\n",
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cache, nl_cache_name(cache), mngr);
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errout_drop_membership:
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for (grp = ops->co_groups; grp->ag_group; grp++)
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nl_socket_drop_membership(mngr->cm_handle, grp->ag_group);
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nl_cache_free(cache);
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* Get file descriptor
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* @arg mngr Cache Manager
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* Get the file descriptor of the socket associated to the manager.
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* This can be used to change socket options or monitor activity
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* using poll()/select().
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int nl_cache_mngr_get_fd(struct nl_cache_mngr *mngr)
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return nl_socket_get_fd(mngr->cm_handle);
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* Check for event notifications
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* @arg mngr Cache Manager
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* @arg timeout Upper limit poll() will block, in milliseconds.
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* Causes poll() to be called to check for new event notifications
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* being available. Automatically receives and handles available
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* This functionally is ideally called regularly during an idle
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* @return A positive value if at least one update was handled, 0
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* for none, or a negative error code.
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int nl_cache_mngr_poll(struct nl_cache_mngr *mngr, int timeout)
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struct pollfd fds = {
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.fd = nl_socket_get_fd(mngr->cm_handle),
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NL_DBG(3, "Cache manager %p, poll() fd %d\n", mngr, fds.fd);
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ret = poll(&fds, 1, timeout);
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NL_DBG(3, "Cache manager %p, poll() returned %d\n", mngr, ret);
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return -nl_syserr2nlerr(errno);
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return nl_cache_mngr_data_ready(mngr);
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* Receive available event notifications
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* @arg mngr Cache manager
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* This function can be called if the socket associated to the manager
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* contains updates to be received. This function should not be used
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* if nl_cache_mngr_poll() is used.
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* @return A positive value if at least one update was handled, 0
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* for none, or a negative error code.
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int nl_cache_mngr_data_ready(struct nl_cache_mngr *mngr)
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err = nl_recvmsgs_default(mngr->cm_handle);
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* Free cache manager and all caches.
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* @arg mngr Cache manager.
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* Release all resources after usage of a cache manager.
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void nl_cache_mngr_free(struct nl_cache_mngr *mngr)
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nl_close(mngr->cm_handle);
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for (i = 0; i < mngr->cm_nassocs; i++)
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if (mngr->cm_assocs[i].ca_cache)
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nl_cache_free(mngr->cm_assocs[i].ca_cache);
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free(mngr->cm_assocs);
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NL_DBG(1, "Cache manager %p freed\n", mngr);
added
removed
lib/cache_mngr.c
