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444 lines
9.9 KiB
444 lines
9.9 KiB
/* SPDX-License-Identifier: LGPL-2.1-only */
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/*
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* lib/cache_mngt.c Cache Management
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*
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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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* of the License.
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*
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* Copyright (c) 2003-2012 Thomas Graf <tgraf@suug.ch>
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*/
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/**
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* @ingroup core
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* @defgroup cache_mngt Caching System
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*
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* Related sections in the development guide:
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* - @core_doc{core_cache, Caching System}
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*
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* @{
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*
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* Header
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* ------
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* ~~~~{.c}
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* #include <netlink/cache.h>
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* ~~~~
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*/
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#include <netlink-private/netlink.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 struct nl_cache_ops *cache_ops;
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static NL_RW_LOCK(cache_ops_lock);
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/**
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* @name Cache Operations Sets
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* @{
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*/
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static struct nl_cache_ops *__nl_cache_ops_lookup(const char *name)
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{
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struct nl_cache_ops *ops;
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for (ops = cache_ops; ops; ops = ops->co_next)
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if (!strcmp(ops->co_name, name))
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return ops;
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return NULL;
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}
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/**
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* Increment reference counter
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* @arg ops Cache operations
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*/
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void nl_cache_ops_get(struct nl_cache_ops *ops)
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{
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ops->co_refcnt++;
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}
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/**
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* Decrement reference counter
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* @arg ops Cache operations
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*/
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void nl_cache_ops_put(struct nl_cache_ops *ops)
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{
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ops->co_refcnt--;
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}
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/**
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* Lookup cache operations by name
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* @arg name name of the cache type
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*
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* @attention This function is not safe, it does not increment the reference
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* counter. Please use nl_cache_ops_lookup_safe().
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*
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* @return The cache operations or NULL if not found.
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*/
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struct nl_cache_ops *nl_cache_ops_lookup(const char *name)
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{
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struct nl_cache_ops *ops;
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nl_read_lock(&cache_ops_lock);
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ops = __nl_cache_ops_lookup(name);
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nl_read_unlock(&cache_ops_lock);
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return ops;
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}
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/**
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* Lookup cache operations by name
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* @arg name name of the cache type
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*
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* @note The reference counter of the returned cache operation is incremented
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* and must be decremented after use with nl_cache_ops_put().
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*
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* @return The cache operations or NULL if not found.
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*/
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struct nl_cache_ops *nl_cache_ops_lookup_safe(const char *name)
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{
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struct nl_cache_ops *ops;
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nl_write_lock(&cache_ops_lock);
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if ((ops = __nl_cache_ops_lookup(name)))
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nl_cache_ops_get(ops);
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nl_write_unlock(&cache_ops_lock);
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return ops;
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}
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static struct nl_cache_ops *__cache_ops_associate(int protocol, int msgtype)
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{
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int i;
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struct nl_cache_ops *ops;
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for (ops = cache_ops; ops; ops = ops->co_next) {
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if (ops->co_protocol != protocol)
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continue;
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for (i = 0; ops->co_msgtypes[i].mt_id >= 0; i++)
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if (ops->co_msgtypes[i].mt_id == msgtype)
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return ops;
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}
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return NULL;
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}
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/**
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* Associate protocol and message type to cache operations
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* @arg protocol netlink protocol
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* @arg msgtype netlink message type
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*
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* @attention This function is not safe, it does not increment the reference
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* counter. Please use nl_cache_ops_associate_safe().
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*
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* @see nl_cache_ops_associate_safe()
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*
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* @return The cache operations or NULL if no match found.
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*/
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struct nl_cache_ops *nl_cache_ops_associate(int protocol, int msgtype)
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{
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struct nl_cache_ops *ops;
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nl_read_lock(&cache_ops_lock);
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ops = __cache_ops_associate(protocol, msgtype);
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nl_read_unlock(&cache_ops_lock);
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return ops;
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}
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/**
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* Associate protocol and message type to cache operations
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* @arg protocol netlink protocol
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* @arg msgtype netlink message type
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*
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* Searches the registered cache operations for a matching protocol
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* and message type.
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*
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* @note The reference counter of the returned cache operation is incremented
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* and must be decremented after use with nl_cache_ops_put().
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*
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* @return The cache operations or NULL if no no match was found.
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*/
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struct nl_cache_ops *nl_cache_ops_associate_safe(int protocol, int msgtype)
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{
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struct nl_cache_ops *ops;
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nl_write_lock(&cache_ops_lock);
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if ((ops = __cache_ops_associate(protocol, msgtype)))
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nl_cache_ops_get(ops);
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nl_write_unlock(&cache_ops_lock);
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return ops;
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}
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/**
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* Lookup message type cache association
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* @arg ops cache operations
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* @arg msgtype netlink message type
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*
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* Searches for a matching message type association ing the specified
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* cache operations.
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*
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* @attention The guranteed lifetime of the returned message type is bound
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* to the lifetime of the underlying cache operations.
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*
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* @return A message type association or NULL.
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*/
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struct nl_msgtype *nl_msgtype_lookup(struct nl_cache_ops *ops, int msgtype)
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{
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int i;
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for (i = 0; ops->co_msgtypes[i].mt_id >= 0; i++)
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if (ops->co_msgtypes[i].mt_id == msgtype)
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return &ops->co_msgtypes[i];
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return NULL;
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}
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/* Must hold cache_ops_lock */
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static struct nl_cache_ops *cache_ops_lookup_for_obj(struct nl_object_ops *obj_ops)
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{
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struct nl_cache_ops *ops;
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for (ops = cache_ops; ops; ops = ops->co_next)
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if (ops->co_obj_ops == obj_ops)
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return ops;
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return NULL;
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}
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/**
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* Call a function for each registered cache operation
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* @arg cb Callback function to be called
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* @arg arg User specific argument.
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*/
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void nl_cache_ops_foreach(void (*cb)(struct nl_cache_ops *, void *), void *arg)
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{
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struct nl_cache_ops *ops;
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nl_read_lock(&cache_ops_lock);
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for (ops = cache_ops; ops; ops = ops->co_next)
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cb(ops, arg);
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nl_read_unlock(&cache_ops_lock);
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}
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/**
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* Set default flags for caches of this type
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* @arg ops Cache ops
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* @arg flags Flags to set
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*
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* The cache operation flags will be derived to all caches allocates
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* based on this set of cache operations.
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*/
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void nl_cache_ops_set_flags(struct nl_cache_ops *ops, unsigned int flags)
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{
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nl_write_lock(&cache_ops_lock);
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ops->co_flags |= flags;
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nl_write_unlock(&cache_ops_lock);
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}
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/**
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* Register a set of cache operations
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* @arg ops cache operations
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*
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* Called by users of caches to announce the avaibility of
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* a certain cache type.
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*
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* @return 0 on success or a negative error code.
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*/
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int nl_cache_mngt_register(struct nl_cache_ops *ops)
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{
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if (!ops->co_name || !ops->co_obj_ops)
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return -NLE_INVAL;
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/* oo_keygen() also needs oo_compare() */
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BUG_ON (ops->co_obj_ops->oo_keygen && !ops->co_obj_ops->oo_compare);
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nl_write_lock(&cache_ops_lock);
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if (__nl_cache_ops_lookup(ops->co_name)) {
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nl_write_unlock(&cache_ops_lock);
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return -NLE_EXIST;
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}
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ops->co_refcnt = 0;
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ops->co_next = cache_ops;
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cache_ops = ops;
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nl_write_unlock(&cache_ops_lock);
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NL_DBG(1, "Registered cache operations %s\n", ops->co_name);
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return 0;
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}
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/**
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* Unregister a set of cache operations
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* @arg ops cache operations
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*
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* Called by users of caches to announce a set of
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* cache operations is no longer available. The
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* specified cache operations must have been registered
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* previously using nl_cache_mngt_register()
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*
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* @return 0 on success or a negative error code
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*/
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int nl_cache_mngt_unregister(struct nl_cache_ops *ops)
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{
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struct nl_cache_ops *t, **tp;
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int err = 0;
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nl_write_lock(&cache_ops_lock);
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if (ops->co_refcnt > 0) {
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err = -NLE_BUSY;
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goto errout;
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}
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for (tp = &cache_ops; (t=*tp) != NULL; tp = &t->co_next)
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if (t == ops)
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break;
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if (!t) {
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err = -NLE_NOCACHE;
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goto errout;
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}
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NL_DBG(1, "Unregistered cache operations %s\n", ops->co_name);
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*tp = t->co_next;
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errout:
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nl_write_unlock(&cache_ops_lock);
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return err;
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}
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/** @} */
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/**
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* @name Global Cache Provisioning/Requiring
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* @{
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*/
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/**
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* Provide a cache for global use
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* @arg cache cache to provide
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*
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* Offers the specified cache to be used by other modules.
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* Only one cache per type may be shared at a time,
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* a previsouly provided caches will be overwritten.
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*/
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void nl_cache_mngt_provide(struct nl_cache *cache)
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{
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struct nl_cache_ops *ops;
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nl_write_lock(&cache_ops_lock);
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ops = cache_ops_lookup_for_obj(cache->c_ops->co_obj_ops);
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if (!ops)
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BUG();
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else {
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nl_cache_get(cache);
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/*
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* Hold a reference to the cache operations to ensure the
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* ops don't go away while we use it to store the cache pointer.
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*/
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if (!ops->co_major_cache)
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nl_cache_ops_get(ops);
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ops->co_major_cache = cache;
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}
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nl_write_unlock(&cache_ops_lock);
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}
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/**
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* Unprovide a cache for global use
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* @arg cache cache to unprovide
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*
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* Cancels the offer to use a cache globally. The
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* cache will no longer be returned via lookups but
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* may still be in use.
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*/
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void nl_cache_mngt_unprovide(struct nl_cache *cache)
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{
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struct nl_cache_ops *ops;
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nl_write_lock(&cache_ops_lock);
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ops = cache_ops_lookup_for_obj(cache->c_ops->co_obj_ops);
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if (!ops)
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BUG();
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else if (ops->co_major_cache == cache) {
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nl_cache_free(ops->co_major_cache);
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nl_cache_ops_put(ops);
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ops->co_major_cache = NULL;
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}
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nl_write_unlock(&cache_ops_lock);
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}
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struct nl_cache *__nl_cache_mngt_require(const char *name)
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{
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struct nl_cache_ops *ops;
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struct nl_cache *cache = NULL;
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ops = nl_cache_ops_lookup_safe(name);
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if (ops) {
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cache = ops->co_major_cache;
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nl_cache_ops_put(ops);
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}
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return cache;
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}
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/**
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* Return cache previously provided via nl_cache_mngt_provide()
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* @arg name Name of cache to lookup
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*
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* @attention This function is not safe, it does not increment the reference
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* counter. Please use nl_cache_mngt_require_safe().
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*
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* @see nl_cache_mngt_require_safe()
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*
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* @return Pointer to cache or NULL if none registered
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*/
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struct nl_cache *nl_cache_mngt_require(const char *name)
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{
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struct nl_cache *cache;
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if (!(cache = __nl_cache_mngt_require(name)))
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NL_DBG(1, "Application BUG: Your application must "
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"call nl_cache_mngt_provide() and\nprovide a valid "
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"%s cache to be used for internal lookups.\nSee the "
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" API documentation for more details.\n", name);
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return cache;
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}
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/**
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* Return cache previously provided via nl_cache_mngt_provide()
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* @arg name Name of cache to lookup
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*
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* @note The reference counter of the returned cache is incremented
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* and must be decremented after use with nl_cache_put().
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*
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* @return Pointer to cache or NULL if none registered
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*/
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struct nl_cache *nl_cache_mngt_require_safe(const char *name)
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{
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struct nl_cache *cache;
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if ((cache = nl_cache_mngt_require(name)))
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nl_cache_get(cache);
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return cache;
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}
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/** @} */
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/** @} */
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