libnl  1.1
cache_mngt.c
1 /*
2  * lib/cache_mngt.c Cache Management
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 /**
13  * @defgroup cache_mngt Caching
14  * @{
15  */
16 
17 #include <netlink-local.h>
18 #include <netlink/netlink.h>
19 #include <netlink/cache.h>
20 #include <netlink/utils.h>
21 
22 static struct nl_cache_ops *cache_ops;
23 
24 /**
25  * @name Cache Operations Sets
26  * @{
27  */
28 
29 /**
30  * Lookup the set cache operations of a certain cache type
31  * @arg name name of the cache type
32  *
33  * @return The cache operations or NULL if no operations
34  * have been registered under the specified name.
35  */
36 struct nl_cache_ops *nl_cache_ops_lookup(const char *name)
37 {
38  struct nl_cache_ops *ops;
39 
40  for (ops = cache_ops; ops; ops = ops->co_next)
41  if (!strcmp(ops->co_name, name))
42  return ops;
43 
44  return NULL;
45 }
46 
47 /**
48  * Associate a message type to a set of cache operations
49  * @arg protocol netlink protocol
50  * @arg msgtype netlink message type
51  *
52  * Associates the specified netlink message type with
53  * a registered set of cache operations.
54  *
55  * @return The cache operations or NULL if no association
56  * could be made.
57  */
58 struct nl_cache_ops *nl_cache_ops_associate(int protocol, int msgtype)
59 {
60  int i;
61  struct nl_cache_ops *ops;
62 
63  for (ops = cache_ops; ops; ops = ops->co_next)
64  for (i = 0; ops->co_msgtypes[i].mt_id >= 0; i++)
65  if (ops->co_msgtypes[i].mt_id == msgtype &&
66  ops->co_protocol == protocol)
67  return ops;
68 
69  return NULL;
70 }
71 
72 /**
73  * Lookup message type cache association
74  * @arg ops cache operations
75  * @arg msgtype netlink message type
76  *
77  * Searches for a matching message type association ing the specified
78  * cache operations.
79  *
80  * @return A message type association or NULL.
81  */
82 struct nl_msgtype *nl_msgtype_lookup(struct nl_cache_ops *ops, int msgtype)
83 {
84  int i;
85 
86  for (i = 0; ops->co_msgtypes[i].mt_id >= 0; i++)
87  if (ops->co_msgtypes[i].mt_id == msgtype)
88  return &ops->co_msgtypes[i];
89 
90  return NULL;
91 }
92 
93 static struct nl_cache_ops *cache_ops_lookup_for_obj(struct nl_object_ops *obj_ops)
94 {
95  struct nl_cache_ops *ops;
96 
97  for (ops = cache_ops; ops; ops = ops->co_next)
98  if (ops->co_obj_ops == obj_ops)
99  return ops;
100 
101  return NULL;
102 
103 }
104 
105 /**
106  * Call a function for each registered cache operation
107  * @arg cb Callback function to be called
108  * @arg arg User specific argument.
109  */
110 void nl_cache_ops_foreach(void (*cb)(struct nl_cache_ops *, void *), void *arg)
111 {
112  struct nl_cache_ops *ops;
113 
114  for (ops = cache_ops; ops; ops = ops->co_next)
115  cb(ops, arg);
116 }
117 
118 /**
119  * Register a set of cache operations
120  * @arg ops cache operations
121  *
122  * Called by users of caches to announce the avaibility of
123  * a certain cache type.
124  *
125  * @return 0 on success or a negative error code.
126  */
128 {
129  if (!ops->co_name)
130  return nl_error(EINVAL, "No cache name specified");
131 
132  if (!ops->co_obj_ops)
133  return nl_error(EINVAL, "No obj cache ops specified");
134 
135  if (nl_cache_ops_lookup(ops->co_name))
136  return nl_error(EEXIST, "Cache operations already exist");
137 
138  ops->co_next = cache_ops;
139  cache_ops = ops;
140 
141  NL_DBG(1, "Registered cache operations %s\n", ops->co_name);
142 
143  return 0;
144 }
145 
146 /**
147  * Unregister a set of cache operations
148  * @arg ops cache operations
149  *
150  * Called by users of caches to announce a set of
151  * cache operations is no longer available. The
152  * specified cache operations must have been registered
153  * previously using nl_cache_mngt_register()
154  *
155  * @return 0 on success or a negative error code
156  */
158 {
159  struct nl_cache_ops *t, **tp;
160 
161  for (tp = &cache_ops; (t=*tp) != NULL; tp = &t->co_next)
162  if (t == ops)
163  break;
164 
165  if (!t)
166  return nl_error(ENOENT, "No such cache operations");
167 
168  NL_DBG(1, "Unregistered cache operations %s\n", ops->co_name);
169 
170  *tp = t->co_next;
171  return 0;
172 }
173 
174 /** @} */
175 
176 /**
177  * @name Global Cache Provisioning/Requiring
178  * @{
179  */
180 
181 /**
182  * Provide a cache for global use
183  * @arg cache cache to provide
184  *
185  * Offers the specified cache to be used by other modules.
186  * Only one cache per type may be shared at a time,
187  * a previsouly provided caches will be overwritten.
188  */
189 void nl_cache_mngt_provide(struct nl_cache *cache)
190 {
191  struct nl_cache_ops *ops;
192 
193  ops = cache_ops_lookup_for_obj(cache->c_ops->co_obj_ops);
194  if (!ops)
195  BUG();
196  else
197  ops->co_major_cache = cache;
198 }
199 
200 /**
201  * Unprovide a cache for global use
202  * @arg cache cache to unprovide
203  *
204  * Cancels the offer to use a cache globally. The
205  * cache will no longer be returned via lookups but
206  * may still be in use.
207  */
208 void nl_cache_mngt_unprovide(struct nl_cache *cache)
209 {
210  struct nl_cache_ops *ops;
211 
212  ops = cache_ops_lookup_for_obj(cache->c_ops->co_obj_ops);
213  if (!ops)
214  BUG();
215  else if (ops->co_major_cache == cache)
216  ops->co_major_cache = NULL;
217 }
218 
219 /**
220  * Demand the use of a global cache
221  * @arg name name of the required object type
222  *
223  * Trys to find a cache of the specified type for global
224  * use.
225  *
226  * @return A cache provided by another subsystem of the
227  * specified type marked to be available.
228  */
229 struct nl_cache *nl_cache_mngt_require(const char *name)
230 {
231  struct nl_cache_ops *ops;
232 
233  ops = nl_cache_ops_lookup(name);
234  if (!ops || !ops->co_major_cache) {
235  fprintf(stderr, "Application BUG: Your application must "
236  "call nl_cache_mngt_provide() and\nprovide a valid "
237  "%s cache to be used for internal lookups.\nSee the "
238  " API documentation for more details.\n", name);
239 
240  return NULL;
241  }
242 
243  return ops->co_major_cache;
244 }
245 
246 /** @} */
247 
248 /** @} */