libnl  3.2.7
object-api.h
1 /*
2  * netlink/object-api.c Object 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) 2003-2007 Thomas Graf <tgraf@suug.ch>
10  */
11 
12 #ifndef NETLINK_OBJECT_API_H_
13 #define NETLINK_OBJECT_API_H_
14 
15 #include <netlink/netlink.h>
16 #include <netlink/utils.h>
17 
18 #ifdef __cplusplus
19 extern "C" {
20 #endif
21 
22 /**
23  * @ingroup object
24  * @defgroup object_api Object API
25  * @brief
26  *
27  * @par 1) Object Definition
28  * @code
29  * // Define your object starting with the common object header
30  * struct my_obj {
31  * NLHDR_COMMON
32  * int my_data;
33  * };
34  *
35  * // Fill out the object operations structure
36  * struct nl_object_ops my_ops = {
37  * .oo_name = "my_obj",
38  * .oo_size = sizeof(struct my_obj),
39  * };
40  *
41  * // At this point the object can be allocated, you may want to provide a
42  * // separate _alloc() function to ease allocting objects of this kind.
43  * struct nl_object *obj = nl_object_alloc(&my_ops);
44  *
45  * // And release it again...
46  * nl_object_put(obj);
47  * @endcode
48  *
49  * @par 2) Allocating additional data
50  * @code
51  * // You may require to allocate additional data and store it inside
52  * // object, f.e. assuming there is a field `ptr'.
53  * struct my_obj {
54  * NLHDR_COMMON
55  * void * ptr;
56  * };
57  *
58  * // And at some point you may assign allocated data to this field:
59  * my_obj->ptr = calloc(1, ...);
60  *
61  * // In order to not introduce any memory leaks you have to release
62  * // this data again when the last reference is given back.
63  * static void my_obj_free_data(struct nl_object *obj)
64  * {
65  * struct my_obj *my_obj = nl_object_priv(obj);
66  *
67  * free(my_obj->ptr);
68  * }
69  *
70  * // Also when the object is cloned, you must ensure for your pointer
71  * // stay valid even if one of the clones is freed by either making
72  * // a clone as well or increase the reference count.
73  * static int my_obj_clone(struct nl_object *src, struct nl_object *dst)
74  * {
75  * struct my_obj *my_src = nl_object_priv(src);
76  * struct my_obj *my_dst = nl_object_priv(dst);
77  *
78  * if (src->ptr) {
79  * dst->ptr = calloc(1, ...);
80  * memcpy(dst->ptr, src->ptr, ...);
81  * }
82  * }
83  *
84  * struct nl_object_ops my_ops = {
85  * ...
86  * .oo_free_data = my_obj_free_data,
87  * .oo_clone = my_obj_clone,
88  * };
89  * @endcode
90  *
91  * @par 3) Object Dumping
92  * @code
93  * static int my_obj_dump_detailed(struct nl_object *obj,
94  * struct nl_dump_params *params)
95  * {
96  * struct my_obj *my_obj = nl_object_priv(obj);
97  *
98  * // It is absolutely essential to use nl_dump() when printing
99  * // any text to make sure the dumping parameters are respected.
100  * nl_dump(params, "Obj Integer: %d\n", my_obj->my_int);
101  *
102  * // Before we can dump the next line, make sure to prefix
103  * // this line correctly.
104  * nl_new_line(params);
105  *
106  * // You may also split a line into multiple nl_dump() calls.
107  * nl_dump(params, "String: %s ", my_obj->my_string);
108  * nl_dump(params, "String-2: %s\n", my_obj->another_string);
109  * }
110  *
111  * struct nl_object_ops my_ops = {
112  * ...
113  * .oo_dump[NL_DUMP_FULL] = my_obj_dump_detailed,
114  * };
115  * @endcode
116  *
117  * @par 4) Object Attributes
118  * @code
119  * // The concept of object attributes is optional but can ease the typical
120  * // case of objects that have optional attributes, e.g. a route may have a
121  * // nexthop assigned but it is not required to.
122  *
123  * // The first step to define your object specific bitmask listing all
124  * // attributes
125  * #define MY_ATTR_FOO (1<<0)
126  * #define MY_ATTR_BAR (1<<1)
127  *
128  * // When assigning an optional attribute to the object, make sure
129  * // to mark its availability.
130  * my_obj->foo = 123123;
131  * my_obj->ce_mask |= MY_ATTR_FOO;
132  *
133  * // At any time you may use this mask to check for the availability
134  * // of the attribute, e.g. while dumping
135  * if (my_obj->ce_mask & MY_ATTR_FOO)
136  * nl_dump(params, "foo %d ", my_obj->foo);
137  *
138  * // One of the big advantages of this concept is that it allows for
139  * // standardized comparisons which make it trivial for caches to
140  * // identify unique objects by use of unified comparison functions.
141  * // In order for it to work, your object implementation must provide
142  * // a comparison function and define a list of attributes which
143  * // combined together make an object unique.
144  *
145  * static int my_obj_compare(struct nl_object *_a, struct nl_object *_b,
146  * uint32_t attrs, int flags)
147  * {
148  * struct my_obj *a = nl_object_priv(_a):
149  * struct my_obj *b = nl_object_priv(_b):
150  * int diff = 0;
151  *
152  * // We help ourselves in defining our own DIFF macro which will
153  * // call ATTR_DIFF() on both objects which will make sure to only
154  * // compare the attributes if required.
155  * #define MY_DIFF(ATTR, EXPR) ATTR_DIFF(attrs, MY_ATTR_##ATTR, a, b, EXPR)
156  *
157  * // Call our own diff macro for each attribute to build a bitmask
158  * // representing the attributes which mismatch.
159  * diff |= MY_DIFF(FOO, a->foo != b->foo)
160  * diff |= MY_DIFF(BAR, strcmp(a->bar, b->bar))
161  *
162  * return diff;
163  * }
164  *
165  * // In order to identify identical objects with differing attributes
166  * // you must specify the attributes required to uniquely identify
167  * // your object. Make sure to not include too many attributes, this
168  * // list is used when caches look for an old version of an object.
169  * struct nl_object_ops my_ops = {
170  * ...
171  * .oo_id_attrs = MY_ATTR_FOO,
172  * .oo_compare = my_obj_compare,
173  * };
174  * @endcode
175  * @{
176  */
177 
178 /**
179  * Common Object Header
180  *
181  * This macro must be included as first member in every object
182  * definition to allow objects to be cached.
183  */
184 #define NLHDR_COMMON \
185  int ce_refcnt; \
186  struct nl_object_ops * ce_ops; \
187  struct nl_cache * ce_cache; \
188  struct nl_list_head ce_list; \
189  int ce_msgtype; \
190  int ce_flags; \
191  uint32_t ce_mask;
192 
193 struct nl_object
194 {
196 };
197 
198 
199 /**
200  * Return true if attribute is available in both objects
201  * @arg A an object
202  * @arg B another object
203  * @arg ATTR attribute bit
204  *
205  * @return True if the attribute is available, otherwise false is returned.
206  */
207 #define AVAILABLE(A, B, ATTR) (((A)->ce_mask & (B)->ce_mask) & (ATTR))
208 
209 /**
210  * Return true if attribute is available in only one of both objects
211  * @arg A an object
212  * @arg B another object
213  * @arg ATTR attribute bit
214  *
215  * @return True if the attribute is available in only one of both objects,
216  * otherwise false is returned.
217  */
218 #define AVAILABLE_MISMATCH(A, B, ATTR) (((A)->ce_mask ^ (B)->ce_mask) & (ATTR))
219 
220 /**
221  * Return true if attributes mismatch
222  * @arg A an object
223  * @arg B another object
224  * @arg ATTR attribute bit
225  * @arg EXPR Comparison expression
226  *
227  * This function will check if the attribute in question is available
228  * in both objects, if not this will count as a mismatch.
229  *
230  * If available the function will execute the expression which must
231  * return true if the attributes mismatch.
232  *
233  * @return True if the attribute mismatch, or false if they match.
234  */
235 #define ATTR_MISMATCH(A, B, ATTR, EXPR) (AVAILABLE_MISMATCH(A, B, ATTR) || \
236  (AVAILABLE(A, B, ATTR) && (EXPR)))
237 
238 /**
239  * Return attribute bit if attribute does not match
240  * @arg LIST list of attributes to be compared
241  * @arg ATTR attribute bit
242  * @arg A an object
243  * @arg B another object
244  * @arg EXPR Comparison expression
245  *
246  * This function will check if the attribute in question is available
247  * in both objects, if not this will count as a mismatch.
248  *
249  * If available the function will execute the expression which must
250  * return true if the attributes mismatch.
251  *
252  * In case the attributes mismatch, the attribute is returned, otherwise
253  * 0 is returned.
254  *
255  * @code
256  * diff |= ATTR_DIFF(attrs, MY_ATTR_FOO, a, b, a->foo != b->foo);
257  * @endcode
258  */
259 #define ATTR_DIFF(LIST, ATTR, A, B, EXPR) \
260 ({ int diff = 0; \
261  if (((LIST) & (ATTR)) && ATTR_MISMATCH(A, B, ATTR, EXPR)) \
262  diff = ATTR; \
263  diff; })
264 
265 /**
266  * Object Operations
267  */
269 {
270  /**
271  * Unique name of object type
272  *
273  * Must be in the form family/name, e.g. "route/addr"
274  */
275  char * oo_name;
276 
277  /** Size of object including its header */
278  size_t oo_size;
279 
280  /* List of attributes needed to uniquely identify the object */
281  uint32_t oo_id_attrs;
282 
283  /**
284  * Constructor function
285  *
286  * Will be called when a new object of this type is allocated.
287  * Can be used to initialize members such as lists etc.
288  */
289  void (*oo_constructor)(struct nl_object *);
290 
291  /**
292  * Destructor function
293  *
294  * Will be called when an object is freed. Must free all
295  * resources which may have been allocated as part of this
296  * object.
297  */
298  void (*oo_free_data)(struct nl_object *);
299 
300  /**
301  * Cloning function
302  *
303  * Will be called when an object needs to be cloned. Please
304  * note that the generic object code will make an exact
305  * copy of the object first, therefore you only need to take
306  * care of members which require reference counting etc.
307  *
308  * May return a negative error code to abort cloning.
309  */
310  int (*oo_clone)(struct nl_object *, struct nl_object *);
311 
312  /**
313  * Dumping functions
314  *
315  * Will be called when an object is dumped. The implementations
316  * have to use nl_dump(), nl_dump_line(), and nl_new_line() to
317  * dump objects.
318  *
319  * The functions must return the number of lines printed.
320  */
321  void (*oo_dump[NL_DUMP_MAX+1])(struct nl_object *,
322  struct nl_dump_params *);
323 
324  /**
325  * Comparison function
326  *
327  * Will be called when two objects of the same type are
328  * compared. It takes the two objects in question, an object
329  * specific bitmask defining which attributes should be
330  * compared and flags to control the behaviour.
331  *
332  * The function must return a bitmask with the relevant bit
333  * set for each attribute that mismatches.
334  */
335  int (*oo_compare)(struct nl_object *, struct nl_object *,
336  uint32_t, int);
337 
338 
339  char *(*oo_attrs2str)(int, char *, size_t);
340 };
341 
342 /** @} */
343 
344 #ifdef __cplusplus
345 }
346 #endif
347 
348 #endif