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git.proxmox.com Git - mirror_frr.git/blob - lib/hook.h
2 * Copyright (c) 2016 David Lamparter, for NetDEF, Inc.
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
29 /* type-safe subscribable hook points
31 * where "type-safe" applies to the function pointers used for subscriptions
38 * DECLARE_HOOK (some_update_event, (struct eventinfo *info), (info));
41 * DEFINE_HOOK (some_update_event, (struct eventinfo *info), (info));
43 * hook_call (some_update_event, info)
45 * Note: the second and third macro args must be the hook function's
46 * parameter list, with the same names for each parameter. The second
47 * macro arg is with types (used for defining things), the third arg is
48 * just the names (used for passing along parameters).
50 * Do not use parameter names starting with "hook", these can collide with
51 * names used by the hook code itself.
53 * The return value is always "int" for now; hook_call will sum up the
54 * return values from each registered user. Default is 0.
56 * There are no pre-defined semantics for the value, in most cases it is
57 * ignored. For success/failure indication, 0 should be success, and
58 * handlers should make sure to only return 0 or 1 (not -1 or other values).
61 * - to use a hook / create a handler:
63 * #include "mydaemon.h"
64 * int event_handler (struct eventinfo *info) { ... }
65 * hook_register (some_update_event, event_handler);
67 * or, if you need an argument to be passed along (addonptr will be added
68 * as first argument when calling the handler):
70 * #include "mydaemon.h"
71 * int event_handler (void *addonptr, struct eventinfo *info) { ... }
72 * hook_register_arg (some_update_event, event_handler, addonptr);
74 * (addonptr isn't typesafe, but that should be manageable.)
76 * Hooks also support a "priority" value for ordering registered calls
77 * relative to each other. The priority is a signed integer where lower
78 * values are called earlier. There is also "Koohs", which is hooks with
79 * reverse priority ordering (for cleanup/deinit hooks, so you can use the
80 * same priority value).
82 * Recommended priority value ranges are:
84 * -999 ... 0 ... 999 - main executable / daemon, or library
85 * -1999 ... -1000 - modules registering calls that should run before
87 * 1000 ... 1999 - modules calls that should run after daemon's
89 * Note: the default value is 1000, based on the following 2 expectations:
90 * - most hook_register() usage will be in loadable modules
91 * - usage of hook_register() in the daemon itself may need relative ordering
92 * to itself, making an explicit value the expected case
94 * The priority value is passed as extra argument on hook_register_prio() /
95 * hook_register_arg_prio(). Whether a hook runs in reverse is determined
96 * solely by the code defining / calling the hook. (DECLARE_KOOH is actually
97 * the same thing as DECLARE_HOOK, it's just there to make it obvious.)
101 * - hook_unregister_all_module()
102 * - introspection / CLI / debug
105 * For loadable modules, the idea is that hooks could be automatically
106 * unregistered when a module is unloaded.
108 * It's also possible to add a constructor (MTYPE style) to DEFINE_HOOK,
109 * which would make it possible for the CLI to show all hooks and all
110 * registered handlers.
114 struct hookent
*next
;
115 void *hookfn
; /* actually a function pointer */
118 bool ent_on_heap
: 1;
121 struct frrmod_runtime
*module
;
127 struct hookent
*entries
;
131 #define HOOK_DEFAULT_PRIORITY 1000
133 /* subscribe/add callback function to a hook
135 * always use hook_register(), which uses the static inline helper from
136 * DECLARE_HOOK in order to get type safety
138 extern void _hook_register(struct hook
*hook
, struct hookent
*stackent
,
139 void *funcptr
, void *arg
, bool has_arg
,
140 struct frrmod_runtime
*module
,
141 const char *funcname
, int priority
);
143 /* most hook_register calls are not in a loop or similar and can use a
144 * statically allocated "struct hookent" from the data segment
146 #define _hook_reg_svar(hook, funcptr, arg, has_arg, module, funcname, prio) \
148 static struct hookent stack_hookent = {}; \
149 _hook_register(hook, &stack_hookent, funcptr, arg, has_arg, \
150 module, funcname, prio); \
153 #define hook_register(hookname, func) \
154 _hook_reg_svar(&_hook_##hookname, _hook_typecheck_##hookname(func), \
155 NULL, false, THIS_MODULE, #func, HOOK_DEFAULT_PRIORITY)
156 #define hook_register_arg(hookname, func, arg) \
157 _hook_reg_svar(&_hook_##hookname, \
158 _hook_typecheck_arg_##hookname(func), arg, true, \
159 THIS_MODULE, #func, HOOK_DEFAULT_PRIORITY)
160 #define hook_register_prio(hookname, prio, func) \
161 _hook_reg_svar(&_hook_##hookname, _hook_typecheck_##hookname(func), \
162 NULL, false, THIS_MODULE, #func, prio)
163 #define hook_register_arg_prio(hookname, prio, func, arg) \
164 _hook_reg_svar(&_hook_##hookname, \
165 _hook_typecheck_arg_##hookname(func), arg, true, \
166 THIS_MODULE, #func, prio)
168 extern void _hook_unregister(struct hook
*hook
, void *funcptr
, void *arg
,
170 #define hook_unregister(hookname, func) \
171 _hook_unregister(&_hook_##hookname, _hook_typecheck_##hookname(func), \
173 #define hook_unregister_arg(hookname, func, arg) \
174 _hook_unregister(&_hook_##hookname, \
175 _hook_typecheck_arg_##hookname(func), arg, true)
178 * this is private (static) to the file that has the DEFINE_HOOK statement
180 #define hook_call(hookname, ...) hook_call_##hookname(__VA_ARGS__)
182 /* helpers to add the void * arg */
183 #define HOOK_ADDDEF(...) (void *hookarg , ## __VA_ARGS__)
184 #define HOOK_ADDARG(...) (hookarg , ## __VA_ARGS__)
186 /* and another helper to convert () into (void) to get a proper prototype */
187 #define _SKIP_10(x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, ret, ...) ret
188 #define _MAKE_VOID(...) _SKIP_10(, ##__VA_ARGS__, , , , , , , , , , void)
190 #define HOOK_VOIDIFY(...) (_MAKE_VOID(__VA_ARGS__) __VA_ARGS__)
192 /* use in header file - declares the hook and its arguments
193 * usage: DECLARE_HOOK(my_hook, (int arg1, struct foo *arg2), (arg1, arg2));
194 * as above, "passlist" must use the same order and same names as "arglist"
196 * theoretically passlist is not necessary, but let's keep things simple and
197 * use exact same args on DECLARE and DEFINE.
199 #define DECLARE_HOOK(hookname, arglist, passlist) \
200 extern struct hook _hook_##hookname; \
201 __attribute__((unused)) static inline void * \
202 _hook_typecheck_##hookname(int(*funcptr) HOOK_VOIDIFY arglist) \
204 return (void *)funcptr; \
206 __attribute__((unused)) static inline void \
207 *_hook_typecheck_arg_##hookname(int(*funcptr) \
208 HOOK_ADDDEF arglist) \
210 return (void *)funcptr; \
212 MACRO_REQUIRE_SEMICOLON() /* end */
214 #define DECLARE_KOOH(hookname, arglist, passlist) \
215 DECLARE_HOOK(hookname, arglist, passlist)
217 /* use in source file - contains hook-related definitions.
219 #define DEFINE_HOOK_INT(hookname, arglist, passlist, rev) \
220 struct hook _hook_##hookname = { \
221 .name = #hookname, .entries = NULL, .reverse = rev, \
223 static int hook_call_##hookname HOOK_VOIDIFY arglist \
226 struct hookent *he = _hook_##hookname.entries; \
230 int(*fptr) HOOK_VOIDIFY arglist; \
231 int(*farg) HOOK_ADDDEF arglist; \
233 for (; he; he = he->next) { \
234 hookarg = he->hookarg; \
235 hookp.voidptr = he->hookfn; \
237 hooksum += hookp.fptr passlist; \
239 hooksum += hookp.farg HOOK_ADDARG passlist; \
243 MACRO_REQUIRE_SEMICOLON() /* end */
245 #define DEFINE_HOOK(hookname, arglist, passlist) \
246 DEFINE_HOOK_INT(hookname, arglist, passlist, false)
247 #define DEFINE_KOOH(hookname, arglist, passlist) \
248 DEFINE_HOOK_INT(hookname, arglist, passlist, true)
254 #endif /* _FRR_HOOK_H */