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* netlink/cache-api.h Caching API
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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) 2003-2006 Thomas Graf <tgraf@suug.ch>
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#ifndef NETLINK_CACHE_API_H_
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#define NETLINK_CACHE_API_H_
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#include <netlink/netlink.h>
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* @defgroup cache_api Cache Implementation
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* @par 1) Cache Definition
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* struct nl_cache_ops my_cache_ops = {
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* .co_name = "route/link",
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* .co_protocol = NETLINK_ROUTE,
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* .co_hdrsize = sizeof(struct ifinfomsg),
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* .co_obj_ops = &my_obj_ops,
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* // The simplest way to fill a cache is by providing a request-update
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* // function which must trigger a complete dump on the kernel-side of
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* // whatever the cache covers.
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* static int my_request_update(struct nl_cache *cache,
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* struct nl_sock *socket)
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* // In this example, we request a full dump of the interface table
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* return nl_rtgen_request(socket, RTM_GETLINK, AF_UNSPEC, NLM_F_DUMP);
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* // The resulting netlink messages sent back will be fed into a message
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* // parser one at a time. The message parser has to extract all relevant
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* // information from the message and create an object reflecting the
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* // contents of the message and pass it on to the parser callback function
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* // provide which will add the object to the cache.
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* static int my_msg_parser(struct nl_cache_ops *ops, struct sockaddr_nl *who,
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* struct nlmsghdr *nlh, struct nl_parser_param *pp)
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* obj = my_obj_alloc();
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* obj->ce_msgtype = nlh->nlmsg_type;
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* // Parse the netlink message and continue creating the object.
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* err = pp->pp_cb((struct nl_object *) obj, pp);
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* struct nl_cache_ops my_cache_ops = {
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* .co_request_update = my_request_update,
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* .co_msg_parser = my_msg_parser,
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* @par 3) Notification based Updates
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* // Caches can be kept up-to-date based on notifications if the kernel
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* // sends out notifications whenever an object is added/removed/changed.
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* // It is trivial to support this, first a list of groups needs to be
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* // defined which are required to join in order to receive all necessary
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* // notifications. The groups are separated by address family to support
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* // the common situation where a separate group is used for each address
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* // family. If there is only one group, simply specify AF_UNSPEC.
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* static struct nl_af_group addr_groups[] = {
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* { AF_INET, RTNLGRP_IPV4_IFADDR },
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* { AF_INET6, RTNLGRP_IPV6_IFADDR },
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* { END_OF_GROUP_LIST },
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* // In order for the caching system to know the meaning of each message
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* // type it requires a table which maps each supported message type to
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* // a cache action, e.g. RTM_NEWADDR means address has been added or
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* // updated, RTM_DELADDR means address has been removed.
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* static struct nl_cache_ops rtnl_addr_ops = {
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* { RTM_NEWADDR, NL_ACT_NEW, "new" },
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* { RTM_DELADDR, NL_ACT_DEL, "del" },
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* { RTM_GETADDR, NL_ACT_GET, "get" },
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* END_OF_MSGTYPES_LIST,
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* .co_groups = addr_groups,
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* // It is now possible to keep the cache up-to-date using the cache manager.
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#define NL_ACT_MAX (__NL_ACT_MAX - 1)
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#define END_OF_MSGTYPES_LIST { -1, -1, NULL }
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* Message type to cache action association
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/** Netlink message type */
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/** Cache action to take */
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/** Name of operation for human-readable printing */
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* Address family to netlink group association
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/** Address family */
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/** Netlink group identifier */
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#define END_OF_GROUP_LIST AF_UNSPEC, 0
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struct nl_parser_param
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int (*pp_cb)(struct nl_object *, struct nl_parser_param *);
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struct nl_af_group * co_groups;
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* Called whenever an update of the cache is required. Must send
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* a request message to the kernel requesting a complete dump.
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int (*co_request_update)(struct nl_cache *, struct nl_sock *);
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* Called whenever a message was received that needs to be parsed.
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* Must parse the message and call the paser callback function
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* (nl_parser_param) provided via the argument.
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int (*co_msg_parser)(struct nl_cache_ops *, struct sockaddr_nl *,
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struct nlmsghdr *, struct nl_parser_param *);
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struct nl_object_ops * co_obj_ops;
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struct nl_cache_ops *co_next;
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struct nl_cache *co_major_cache;
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struct genl_ops * co_genl;
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struct nl_msgtype co_msgtypes[];
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include/netlink/cache-api.h
