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1 office 1 /*
2 * netlink/cache-api.h Caching API
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation version 2.1
7 * of the License.
8 *
9 * Copyright (c) 2003-2006 Thomas Graf <tgraf@suug.ch>
10 */
11  
12 #ifndef NETLINK_CACHE_API_H_
13 #define NETLINK_CACHE_API_H_
14  
15 #include <netlink/netlink.h>
16  
17 #ifdef __cplusplus
18 extern "C" {
19 #endif
20  
21 /**
22 * @ingroup cache
23 * @defgroup cache_api Cache Implementation
24 * @brief
25 *
26 * @par 1) Cache Definition
27 * @code
28 * struct nl_cache_ops my_cache_ops = {
29 * .co_name = "route/link",
30 * .co_protocol = NETLINK_ROUTE,
31 * .co_hdrsize = sizeof(struct ifinfomsg),
32 * .co_obj_ops = &my_obj_ops,
33 * };
34 * @endcode
35 *
36 * @par 2)
37 * @code
38 * // The simplest way to fill a cache is by providing a request-update
39 * // function which must trigger a complete dump on the kernel-side of
40 * // whatever the cache covers.
41 * static int my_request_update(struct nl_cache *cache,
42 * struct nl_sock *socket)
43 * {
44 * // In this example, we request a full dump of the interface table
45 * return nl_rtgen_request(socket, RTM_GETLINK, AF_UNSPEC, NLM_F_DUMP);
46 * }
47 *
48 * // The resulting netlink messages sent back will be fed into a message
49 * // parser one at a time. The message parser has to extract all relevant
50 * // information from the message and create an object reflecting the
51 * // contents of the message and pass it on to the parser callback function
52 * // provide which will add the object to the cache.
53 * static int my_msg_parser(struct nl_cache_ops *ops, struct sockaddr_nl *who,
54 * struct nlmsghdr *nlh, struct nl_parser_param *pp)
55 * {
56 * struct my_obj *obj;
57 *
58 * obj = my_obj_alloc();
59 * obj->ce_msgtype = nlh->nlmsg_type;
60 *
61 * // Parse the netlink message and continue creating the object.
62 *
63 * err = pp->pp_cb((struct nl_object *) obj, pp);
64 * if (err < 0)
65 * goto errout;
66 * }
67 *
68 * struct nl_cache_ops my_cache_ops = {
69 * ...
70 * .co_request_update = my_request_update,
71 * .co_msg_parser = my_msg_parser,
72 * };
73 * @endcode
74 *
75 * @par 3) Notification based Updates
76 * @code
77 * // Caches can be kept up-to-date based on notifications if the kernel
78 * // sends out notifications whenever an object is added/removed/changed.
79 * //
80 * // It is trivial to support this, first a list of groups needs to be
81 * // defined which are required to join in order to receive all necessary
82 * // notifications. The groups are separated by address family to support
83 * // the common situation where a separate group is used for each address
84 * // family. If there is only one group, simply specify AF_UNSPEC.
85 * static struct nl_af_group addr_groups[] = {
86 * { AF_INET, RTNLGRP_IPV4_IFADDR },
87 * { AF_INET6, RTNLGRP_IPV6_IFADDR },
88 * { END_OF_GROUP_LIST },
89 * };
90 *
91 * // In order for the caching system to know the meaning of each message
92 * // type it requires a table which maps each supported message type to
93 * // a cache action, e.g. RTM_NEWADDR means address has been added or
94 * // updated, RTM_DELADDR means address has been removed.
95 * static struct nl_cache_ops rtnl_addr_ops = {
96 * ...
97 * .co_msgtypes = {
98 * { RTM_NEWADDR, NL_ACT_NEW, "new" },
99 * { RTM_DELADDR, NL_ACT_DEL, "del" },
100 * { RTM_GETADDR, NL_ACT_GET, "get" },
101 * END_OF_MSGTYPES_LIST,
102 * },
103 * .co_groups = addr_groups,
104 * };
105 *
106 * // It is now possible to keep the cache up-to-date using the cache manager.
107 * @endcode
108 * @{
109 */
110  
111 enum {
112 NL_ACT_UNSPEC,
113 NL_ACT_NEW,
114 NL_ACT_DEL,
115 NL_ACT_GET,
116 NL_ACT_SET,
117 NL_ACT_CHANGE,
118 __NL_ACT_MAX,
119 };
120  
121 #define NL_ACT_MAX (__NL_ACT_MAX - 1)
122  
123 #define END_OF_MSGTYPES_LIST { -1, -1, NULL }
124  
125 /**
126 * Message type to cache action association
127 */
128 struct nl_msgtype
129 {
130 /** Netlink message type */
131 int mt_id;
132  
133 /** Cache action to take */
134 int mt_act;
135  
136 /** Name of operation for human-readable printing */
137 char * mt_name;
138 };
139  
140 /**
141 * Address family to netlink group association
142 */
143 struct nl_af_group
144 {
145 /** Address family */
146 int ag_family;
147  
148 /** Netlink group identifier */
149 int ag_group;
150 };
151  
152 #define END_OF_GROUP_LIST AF_UNSPEC, 0
153  
154 struct nl_parser_param
155 {
156 int (*pp_cb)(struct nl_object *, struct nl_parser_param *);
157 void * pp_arg;
158 };
159  
160 /**
161 * Cache Operations
162 */
163 struct nl_cache_ops
164 {
165 char * co_name;
166  
167 int co_hdrsize;
168 int co_protocol;
169 struct nl_af_group * co_groups;
170  
171 /**
172 * Called whenever an update of the cache is required. Must send
173 * a request message to the kernel requesting a complete dump.
174 */
175 int (*co_request_update)(struct nl_cache *, struct nl_sock *);
176  
177 /**
178 * Called whenever a message was received that needs to be parsed.
179 * Must parse the message and call the paser callback function
180 * (nl_parser_param) provided via the argument.
181 */
182 int (*co_msg_parser)(struct nl_cache_ops *, struct sockaddr_nl *,
183 struct nlmsghdr *, struct nl_parser_param *);
184  
185 struct nl_object_ops * co_obj_ops;
186  
187 struct nl_cache_ops *co_next;
188 struct nl_cache *co_major_cache;
189 struct genl_ops * co_genl;
190 struct nl_msgtype co_msgtypes[];
191 };
192  
193 /** @} */
194  
195 #ifdef __cplusplus
196 }
197 #endif
198  
199 #endif