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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.
25 /* type-safe subscribable hook points
27 * where "type-safe" applies to the function pointers used for subscriptions
34 * DECLARE_HOOK (some_update_event, (struct eventinfo *info), (info))
37 * DEFINE_HOOK (some_update_event, (struct eventinfo *info), (info))
39 * hook_call (some_update_event, info)
41 * Note: the second and third macro args must be the hook function's
42 * parameter list, with the same names for each parameter. The second
43 * macro arg is with types (used for defining things), the third arg is
44 * just the names (used for passing along parameters).
46 * Do not use parameter names starting with "hook", these can collide with
47 * names used by the hook code itself.
49 * The return value is always "int" for now; hook_call will sum up the
50 * return values from each registered user. Default is 0.
52 * There are no pre-defined semantics for the value, in most cases it is
53 * ignored. For success/failure indication, 0 should be success, and
54 * handlers should make sure to only return 0 or 1 (not -1 or other values).
57 * - to use a hook / create a handler:
59 * #include "mydaemon.h"
60 * int event_handler (struct eventinfo *info) { ... }
61 * hook_register (some_update_event, event_handler);
63 * or, if you need an argument to be passed along (addonptr will be added
64 * as first argument when calling the handler):
66 * #include "mydaemon.h"
67 * int event_handler (void *addonptr, struct eventinfo *info) { ... }
68 * hook_register_arg (some_update_event, event_handler, addonptr);
70 * (addonptr isn't typesafe, but that should be manageable.)
72 * Hooks also support a "priority" value for ordering registered calls
73 * relative to each other. The priority is a signed integer where lower
74 * values are called earlier. There is also "Koohs", which is hooks with
75 * reverse priority ordering (for cleanup/deinit hooks, so you can use the
76 * same priority value).
78 * Recommended priority value ranges are:
80 * -999 ... 0 ... 999 - main executable / daemon, or library
81 * -1999 ... -1000 - modules registering calls that should run before
83 * 1000 ... 1999 - modules calls that should run after daemon's
85 * Note: the default value is 1000, based on the following 2 expectations:
86 * - most hook_register() usage will be in loadable modules
87 * - usage of hook_register() in the daemon itself may need relative ordering
88 * to itself, making an explicit value the expected case
90 * The priority value is passed as extra argument on hook_register_prio() /
91 * hook_register_arg_prio(). Whether a hook runs in reverse is determined
92 * solely by the code defining / calling the hook. (DECLARE_KOOH is actually
93 * the same thing as DECLARE_HOOK, it's just there to make it obvious.)
97 * - hook_unregister_all_module()
98 * - introspection / CLI / debug
101 * For loadable modules, the idea is that hooks could be automatically
102 * unregistered when a module is unloaded.
104 * It's also possible to add a constructor (MTYPE style) to DEFINE_HOOK,
105 * which would make it possible for the CLI to show all hooks and all
106 * registered handlers.
110 struct hookent
*next
;
111 void *hookfn
; /* actually a function pointer */
115 struct frrmod_runtime
*module
;
121 struct hookent
*entries
;
125 #define HOOK_DEFAULT_PRIORITY 1000
127 /* subscribe/add callback function to a hook
129 * always use hook_register(), which uses the static inline helper from
130 * DECLARE_HOOK in order to get type safety
132 extern void _hook_register(struct hook
*hook
, void *funcptr
, void *arg
,
133 bool has_arg
, struct frrmod_runtime
*module
,
134 const char *funcname
, int priority
);
135 #define hook_register(hookname, func) \
136 _hook_register(&_hook_##hookname, _hook_typecheck_##hookname(func), \
137 NULL, false, THIS_MODULE, #func, HOOK_DEFAULT_PRIORITY)
138 #define hook_register_arg(hookname, func, arg) \
139 _hook_register(&_hook_##hookname, \
140 _hook_typecheck_arg_##hookname(func), arg, true, \
141 THIS_MODULE, #func, HOOK_DEFAULT_PRIORITY)
142 #define hook_register_prio(hookname, prio, func) \
143 _hook_register(&_hook_##hookname, _hook_typecheck_##hookname(func), \
144 NULL, false, THIS_MODULE, #func, prio)
145 #define hook_register_arg_prio(hookname, prio, func, arg) \
146 _hook_register(&_hook_##hookname, \
147 _hook_typecheck_arg_##hookname(func), arg, true, \
148 THIS_MODULE, #func, prio)
150 extern void _hook_unregister(struct hook
*hook
, void *funcptr
, void *arg
,
152 #define hook_unregister(hookname, func) \
153 _hook_unregister(&_hook_##hookname, _hook_typecheck_##hookname(func), \
155 #define hook_unregister_arg(hookname, func, arg) \
156 _hook_unregister(&_hook_##hookname, \
157 _hook_typecheck_arg_##hookname(func), arg, true)
160 * this is private (static) to the file that has the DEFINE_HOOK statement
162 #define hook_call(hookname, ...) hook_call_##hookname(__VA_ARGS__)
164 /* helpers to add the void * arg */
165 #define HOOK_ADDDEF(...) (void *hookarg , ## __VA_ARGS__)
166 #define HOOK_ADDARG(...) (hookarg , ## __VA_ARGS__)
168 /* use in header file - declares the hook and its arguments
169 * usage: DECLARE_HOOK(my_hook, (int arg1, struct foo *arg2), (arg1, arg2))
170 * as above, "passlist" must use the same order and same names as "arglist"
172 * theoretically passlist is not neccessary, but let's keep things simple and
173 * use exact same args on DECLARE and DEFINE.
175 #define DECLARE_HOOK(hookname, arglist, passlist) \
176 extern struct hook _hook_##hookname; \
177 __attribute__((unused)) static void *_hook_typecheck_##hookname( \
178 int(*funcptr) arglist) \
180 return (void *)funcptr; \
182 __attribute__((unused)) static void *_hook_typecheck_arg_##hookname( \
183 int(*funcptr) HOOK_ADDDEF arglist) \
185 return (void *)funcptr; \
187 #define DECLARE_KOOH(hookname, arglist, passlist) \
188 DECLARE_HOOK(hookname, arglist, passlist)
190 /* use in source file - contains hook-related definitions.
192 #define DEFINE_HOOK_INT(hookname, arglist, passlist, rev) \
193 struct hook _hook_##hookname = { \
194 .name = #hookname, .entries = NULL, .reverse = rev, \
196 static int hook_call_##hookname arglist \
199 struct hookent *he = _hook_##hookname.entries; \
203 int(*fptr) arglist; \
204 int(*farg) HOOK_ADDDEF arglist; \
206 for (; he; he = he->next) { \
207 hookarg = he->hookarg; \
208 hookp.voidptr = he->hookfn; \
210 hooksum += hookp.fptr passlist; \
212 hooksum += hookp.farg HOOK_ADDARG passlist; \
217 #define DEFINE_HOOK(hookname, arglist, passlist) \
218 DEFINE_HOOK_INT(hookname, arglist, passlist, false)
219 #define DEFINE_KOOH(hookname, arglist, passlist) \
220 DEFINE_HOOK_INT(hookname, arglist, passlist, true)
222 #endif /* _FRR_HOOK_H */