package/libnl-tiny/src/include/netlink/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 /**
 194  * Return true if attribute is available in both objects
 195  * @arg A               an object
 196  * @arg B               another object
 197  * @arg ATTR            attribute bit
 198  *
 199  * @return True if the attribute is available, otherwise false is returned.
 200  */
 201 #define AVAILABLE(A, B, ATTR)   (((A)->ce_mask & (B)->ce_mask) & (ATTR))
 202
 203 /**
 204  * Return true if attributes mismatch
 205  * @arg A               an object
 206  * @arg B               another object
 207  * @arg ATTR            attribute bit
 208  * @arg EXPR            Comparison expression
 209  *
 210  * This function will check if the attribute in question is available
 211  * in both objects, if not this will count as a mismatch.
 212  *
 213  * If available the function will execute the expression which must
 214  * return true if the attributes mismatch.
 215  *
 216  * @return True if the attribute mismatch, or false if they match.
 217  */
 218 #define ATTR_MISMATCH(A, B, ATTR, EXPR) (!AVAILABLE(A, B, ATTR) || (EXPR))
 219
 220 /**
 221  * Return attribute bit if attribute does not match
 222  * @arg LIST            list of attributes to be compared
 223  * @arg ATTR            attribute bit
 224  * @arg A               an object
 225  * @arg B               another object
 226  * @arg EXPR            Comparison expression
 227  *
 228  * This function will check if the attribute in question is available
 229  * in both objects, if not this will count as a mismatch.
 230  *
 231  * If available the function will execute the expression which must
 232  * return true if the attributes mismatch.
 233  *
 234  * In case the attributes mismatch, the attribute is returned, otherwise
 235  * 0 is returned.
 236  *
 237  * @code
 238  * diff |= ATTR_DIFF(attrs, MY_ATTR_FOO, a, b, a->foo != b->foo);
 239  * @endcode
 240  */
 241 #define ATTR_DIFF(LIST, ATTR, A, B, EXPR) \
 242 ({      int diff = 0; \
 243         if (((LIST) & (ATTR)) && ATTR_MISMATCH(A, B, ATTR, EXPR)) \
 244                 diff = ATTR; \
 245         diff; })
 246
 247 /**
 248  * Object Operations
 249  */
 250 struct nl_object;
 251 struct nl_object_ops
 252 {
 253         /**
 254          * Unique name of object type
 255          *
 256          * Must be in the form family/name, e.g. "route/addr"
 257          */
 258         char *          oo_name;
 259
 260         /** Size of object including its header */
 261         size_t          oo_size;
 262
 263         /* List of attributes needed to uniquely identify the object */
 264         uint32_t        oo_id_attrs;
 265
 266         /**
 267          * Constructor function
 268          *
 269          * Will be called when a new object of this type is allocated.
 270          * Can be used to initialize members such as lists etc.
 271          */
 272         void  (*oo_constructor)(struct nl_object *);
 273
 274         /**
 275          * Destructor function
 276          *
 277          * Will be called when an object is freed. Must free all
 278          * resources which may have been allocated as part of this
 279          * object.
 280          */
 281         void  (*oo_free_data)(struct nl_object *);
 282
 283         /**
 284          * Cloning function
 285          *
 286          * Will be called when an object needs to be cloned. Please
 287          * note that the generic object code will make an exact
 288          * copy of the object first, therefore you only need to take
 289          * care of members which require reference counting etc.
 290          *
 291          * May return a negative error code to abort cloning.
 292          */
 293         int  (*oo_clone)(struct nl_object *, struct nl_object *);
 294
 295         /**
 296          * Dumping functions
 297          *
 298          * Will be called when an object is dumped. The implementations
 299          * have to use nl_dump(), nl_dump_line(), and nl_new_line() to
 300          * dump objects.
 301          *
 302          * The functions must return the number of lines printed.
 303          */
 304         void (*oo_dump[NL_DUMP_MAX+1])(struct nl_object *,
 305                                        struct nl_dump_params *);
 306
 307         /**
 308          * Comparison function
 309          *
 310          * Will be called when two objects of the same type are
 311          * compared. It takes the two objects in question, an object
 312          * specific bitmask defining which attributes should be
 313          * compared and flags to control the behaviour.
 314          *
 315          * The function must return a bitmask with the relevant bit
 316          * set for each attribute that mismatches.
 317          */
 318         int   (*oo_compare)(struct nl_object *, struct nl_object *,
 319                             uint32_t, int);
 320
 321
 322         char *(*oo_attrs2str)(int, char *, size_t);
 323 };
 324
 325 /** @} */
 326
 327 #ifdef __cplusplus
 328 }
 329 #endif
 330
 331 #endif