/*
* netlink-private/cache-api.h Caching API
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation version 2.1
* of the License.
*
* Copyright (c) 2003-2013 Thomas Graf <tgraf@suug.ch>
*/
#ifndef NETLINK_CACHE_API_H_
#define NETLINK_CACHE_API_H_
#include <netlink/netlink.h>
#include <netlink/cache.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @ingroup cache
* @defgroup cache_api Cache Implementation
* @brief
*
* @par 1) Cache Definition
* @code
* struct nl_cache_ops my_cache_ops = {
* .co_name = "route/link",
* .co_protocol = NETLINK_ROUTE,
* .co_hdrsize = sizeof(struct ifinfomsg),
* .co_obj_ops = &my_obj_ops,
* };
* @endcode
*
* @par 2)
* @code
* // The simplest way to fill a cache is by providing a request-update
* // function which must trigger a complete dump on the kernel-side of
* // whatever the cache covers.
* static int my_request_update(struct nl_cache *cache,
* struct nl_sock *socket)
* {
* // In this example, we request a full dump of the interface table
* return nl_rtgen_request(socket, RTM_GETLINK, AF_UNSPEC, NLM_F_DUMP);
* }
*
* // The resulting netlink messages sent back will be fed into a message
* // parser one at a time. The message parser has to extract all relevant
* // information from the message and create an object reflecting the
* // contents of the message and pass it on to the parser callback function
* // provide which will add the object to the cache.
* static int my_msg_parser(struct nl_cache_ops *ops, struct sockaddr_nl *who,
* struct nlmsghdr *nlh, struct nl_parser_param *pp)
* {
* struct my_obj *obj;
*
* obj = my_obj_alloc();
* obj->ce_msgtype = nlh->nlmsg_type;
*
* // Parse the netlink message and continue creating the object.
*
* err = pp->pp_cb((struct nl_object *) obj, pp);
* if (err < 0)
* goto errout;
* }
*
* struct nl_cache_ops my_cache_ops = {
* ...
* .co_request_update = my_request_update,
* .co_msg_parser = my_msg_parser,
* };
* @endcode
*
* @par 3) Notification based Updates
* @code
* // Caches can be kept up-to-date based on notifications if the kernel
* // sends out notifications whenever an object is added/removed/changed.
* //
* // It is trivial to support this, first a list of groups needs to be
* // defined which are required to join in order to receive all necessary
* // notifications. The groups are separated by address family to support
* // the common situation where a separate group is used for each address
* // family. If there is only one group, simply specify AF_UNSPEC.
* static struct nl_af_group addr_groups[] = {
* { AF_INET, RTNLGRP_IPV4_IFADDR },
* { AF_INET6, RTNLGRP_IPV6_IFADDR },
* { END_OF_GROUP_LIST },
* };
*
* // In order for the caching system to know the meaning of each message
* // type it requires a table which maps each supported message type to
* // a cache action, e.g. RTM_NEWADDR means address has been added or
* // updated, RTM_DELADDR means address has been removed.
* static struct nl_cache_ops rtnl_addr_ops = {
* ...
* .co_msgtypes = {
* { RTM_NEWADDR, NL_ACT_NEW, "new" },
* { RTM_DELADDR, NL_ACT_DEL, "del" },
* { RTM_GETADDR, NL_ACT_GET, "get" },
* END_OF_MSGTYPES_LIST,
* },
* .co_groups = addr_groups,
* };
*
* // It is now possible to keep the cache up-to-date using the cache manager.
* @endcode
* @{
*/
#define END_OF_MSGTYPES_LIST { -1, -1, NULL }
/**
* Message type to cache action association
*/
struct nl_msgtype
{
/** Netlink message type */
int mt_id;
/** Cache action to take */
int mt_act;
/** Name of operation for human-readable printing */
char * mt_name;
};
/**
* Address family to netlink group association
*/
struct nl_af_group
{
/** Address family */
int ag_family;
/** Netlink group identifier */
int ag_group;
};
#define END_OF_GROUP_LIST AF_UNSPEC, 0
/**
* Parser parameters
*
* This structure is used to configure what kind of parser to use
* when parsing netlink messages to create objects.
*/
struct nl_parser_param
{
/** Function to parse netlink messages into objects */
int (*pp_cb)(struct nl_object *, struct nl_parser_param *);
/** Arbitary argument to be passed to the parser */
void * pp_arg;
};
/**
* Cache Operations
*
* This structure defines the characterstics of a cache type. It contains
* pointers to functions which implement the specifics of the object type
* the cache can hold.
*/
struct nl_cache_ops
{
/** Name of cache type (must be unique) */
char * co_name;
/** Size of family specific netlink header */
int co_hdrsize;
/** Netlink protocol */
int co_protocol;
/** cache object hash size **/
int co_hash_size;
/** cache flags */
unsigned int co_flags;
/** Reference counter */
unsigned int co_refcnt;
/** Group definition */
struct nl_af_group * co_groups;
/**
* Called whenever an update of the cache is required. Must send
* a request message to the kernel requesting a complete dump.
*/
int (*co_request_update)(struct nl_cache *, struct nl_sock *);
/**
* Called whenever a message was received that needs to be parsed.
* Must parse the message and call the paser callback function
* (nl_parser_param) provided via the argument.
*/
int (*co_msg_parser)(struct nl_cache_ops *, struct sockaddr_nl *,
struct nlmsghdr *, struct nl_parser_param *);
/**
* The function registered under this callback is called after a
* netlink notification associated with this cache type has been
* parsed into an object and is being considered for inclusio into
* the specified cache.
*
* The purpose of this function is to filter out notifications
* which should be ignored when updating caches.
*
* The function must return NL_SKIP to prevent the object from
* being included, or NL_OK to include it.
*
* @code
* int my_filter(struct nl_cache *cache, struct nl_object *obj)
* {
* if (reason_to_not_include_obj(obj))
* return NL_SKIP;
*
* return NL_OK;
* }
* @endcode
*/
int (*co_event_filter)(struct nl_cache *, struct nl_object *obj);
/**
* The function registered under this callback is called when an
* object formed from a notification event needs to be included in
* a cache.
*
* For each modified object, the change callback \c change_cb must
* be called with the \c data argument provided.
*
* If no function is registered, the function nl_cache_include()
* will be used for this purpose.
*
* @see nl_cache_include()
*/
int (*co_include_event)(struct nl_cache *cache, struct nl_object *obj,
change_func_t change_cb, void *data);
void (*reserved_1)(void);
void (*reserved_2)(void);
void (*reserved_3)(void);
void (*reserved_4)(void);
void (*reserved_5)(void);
void (*reserved_6)(void);
void (*reserved_7)(void);
void (*reserved_8)(void);
/** Object operations */
struct nl_object_ops * co_obj_ops;
/** Internal, do not touch! */
struct nl_cache_ops *co_next;
struct nl_cache *co_major_cache;
struct genl_ops * co_genl;
/* Message type definition */
struct nl_msgtype co_msgtypes[];
};
/** @} */
#ifdef __cplusplus
}
#endif
#endif