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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-28 09:53:30 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-28 09:53:30 +0000
commit2c7cac91ed6e7db0f6937923d2b57f97dbdbc337 (patch)
treec05dc0f8e6aa3accc84e3e5cffc933ed94941383 /lib/hook.h
parentInitial commit. (diff)
downloadfrr-2c7cac91ed6e7db0f6937923d2b57f97dbdbc337.tar.xz
frr-2c7cac91ed6e7db0f6937923d2b57f97dbdbc337.zip
Adding upstream version 8.4.4.upstream/8.4.4upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+/*
+ * Copyright (c) 2016 David Lamparter, for NetDEF, Inc.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef _FRR_HOOK_H
+#define _FRR_HOOK_H
+
+#include <stdbool.h>
+
+#include "module.h"
+#include "memory.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* type-safe subscribable hook points
+ *
+ * where "type-safe" applies to the function pointers used for subscriptions
+ *
+ * overall usage:
+ * - to create a hook:
+ *
+ * mydaemon.h:
+ * #include "hook.h"
+ * DECLARE_HOOK (some_update_event, (struct eventinfo *info), (info));
+ *
+ * mydaemon.c:
+ * DEFINE_HOOK (some_update_event, (struct eventinfo *info), (info));
+ * ...
+ * hook_call (some_update_event, info)
+ *
+ * Note: the second and third macro args must be the hook function's
+ * parameter list, with the same names for each parameter. The second
+ * macro arg is with types (used for defining things), the third arg is
+ * just the names (used for passing along parameters).
+ *
+ * Do not use parameter names starting with "hook", these can collide with
+ * names used by the hook code itself.
+ *
+ * The return value is always "int" for now; hook_call will sum up the
+ * return values from each registered user. Default is 0.
+ *
+ * There are no pre-defined semantics for the value, in most cases it is
+ * ignored. For success/failure indication, 0 should be success, and
+ * handlers should make sure to only return 0 or 1 (not -1 or other values).
+ *
+ *
+ * - to use a hook / create a handler:
+ *
+ * #include "mydaemon.h"
+ * int event_handler (struct eventinfo *info) { ... }
+ * hook_register (some_update_event, event_handler);
+ *
+ * or, if you need an argument to be passed along (addonptr will be added
+ * as first argument when calling the handler):
+ *
+ * #include "mydaemon.h"
+ * int event_handler (void *addonptr, struct eventinfo *info) { ... }
+ * hook_register_arg (some_update_event, event_handler, addonptr);
+ *
+ * (addonptr isn't typesafe, but that should be manageable.)
+ *
+ * Hooks also support a "priority" value for ordering registered calls
+ * relative to each other. The priority is a signed integer where lower
+ * values are called earlier. There is also "Koohs", which is hooks with
+ * reverse priority ordering (for cleanup/deinit hooks, so you can use the
+ * same priority value).
+ *
+ * Recommended priority value ranges are:
+ *
+ * -999 ... 0 ... 999 - main executable / daemon, or library
+ * -1999 ... -1000 - modules registering calls that should run before
+ * the daemon's bits
+ * 1000 ... 1999 - modules calls that should run after daemon's
+ *
+ * Note: the default value is 1000, based on the following 2 expectations:
+ * - most hook_register() usage will be in loadable modules
+ * - usage of hook_register() in the daemon itself may need relative ordering
+ * to itself, making an explicit value the expected case
+ *
+ * The priority value is passed as extra argument on hook_register_prio() /
+ * hook_register_arg_prio(). Whether a hook runs in reverse is determined
+ * solely by the code defining / calling the hook. (DECLARE_KOOH is actually
+ * the same thing as DECLARE_HOOK, it's just there to make it obvious.)
+ */
+
+/* TODO:
+ * - hook_unregister_all_module()
+ * - introspection / CLI / debug
+ * - testcases ;)
+ *
+ * For loadable modules, the idea is that hooks could be automatically
+ * unregistered when a module is unloaded.
+ *
+ * It's also possible to add a constructor (MTYPE style) to DEFINE_HOOK,
+ * which would make it possible for the CLI to show all hooks and all
+ * registered handlers.
+ */
+
+struct hookent {
+ struct hookent *next;
+ void *hookfn; /* actually a function pointer */
+ void *hookarg;
+ bool has_arg : 1;
+ bool ent_on_heap : 1;
+ bool ent_used : 1;
+ int priority;
+ struct frrmod_runtime *module;
+ const char *fnname;
+};
+
+struct hook {
+ const char *name;
+ struct hookent *entries;
+ bool reverse;
+};
+
+#define HOOK_DEFAULT_PRIORITY 1000
+
+/* subscribe/add callback function to a hook
+ *
+ * always use hook_register(), which uses the static inline helper from
+ * DECLARE_HOOK in order to get type safety
+ */
+extern void _hook_register(struct hook *hook, struct hookent *stackent,
+ void *funcptr, void *arg, bool has_arg,
+ struct frrmod_runtime *module,
+ const char *funcname, int priority);
+
+/* most hook_register calls are not in a loop or similar and can use a
+ * statically allocated "struct hookent" from the data segment
+ */
+#define _hook_reg_svar(hook, funcptr, arg, has_arg, module, funcname, prio) \
+ do { \
+ static struct hookent stack_hookent = {}; \
+ _hook_register(hook, &stack_hookent, funcptr, arg, has_arg, \
+ module, funcname, prio); \
+ } while (0)
+
+#define hook_register(hookname, func) \
+ _hook_reg_svar(&_hook_##hookname, _hook_typecheck_##hookname(func), \
+ NULL, false, THIS_MODULE, #func, HOOK_DEFAULT_PRIORITY)
+#define hook_register_arg(hookname, func, arg) \
+ _hook_reg_svar(&_hook_##hookname, \
+ _hook_typecheck_arg_##hookname(func), arg, true, \
+ THIS_MODULE, #func, HOOK_DEFAULT_PRIORITY)
+#define hook_register_prio(hookname, prio, func) \
+ _hook_reg_svar(&_hook_##hookname, _hook_typecheck_##hookname(func), \
+ NULL, false, THIS_MODULE, #func, prio)
+#define hook_register_arg_prio(hookname, prio, func, arg) \
+ _hook_reg_svar(&_hook_##hookname, \
+ _hook_typecheck_arg_##hookname(func), arg, true, \
+ THIS_MODULE, #func, prio)
+
+extern void _hook_unregister(struct hook *hook, void *funcptr, void *arg,
+ bool has_arg);
+#define hook_unregister(hookname, func) \
+ _hook_unregister(&_hook_##hookname, _hook_typecheck_##hookname(func), \
+ NULL, false)
+#define hook_unregister_arg(hookname, func, arg) \
+ _hook_unregister(&_hook_##hookname, \
+ _hook_typecheck_arg_##hookname(func), arg, true)
+
+/* invoke hooks
+ * this is private (static) to the file that has the DEFINE_HOOK statement
+ */
+#define hook_call(hookname, ...) hook_call_##hookname(__VA_ARGS__)
+
+/* helpers to add the void * arg */
+#define HOOK_ADDDEF(...) (void *hookarg , ## __VA_ARGS__)
+#define HOOK_ADDARG(...) (hookarg , ## __VA_ARGS__)
+
+/* and another helper to convert () into (void) to get a proper prototype */
+#define _SKIP_10(x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, ret, ...) ret
+#define _MAKE_VOID(...) _SKIP_10(, ##__VA_ARGS__, , , , , , , , , , void)
+
+#define HOOK_VOIDIFY(...) (_MAKE_VOID(__VA_ARGS__) __VA_ARGS__)
+
+/* use in header file - declares the hook and its arguments
+ * usage: DECLARE_HOOK(my_hook, (int arg1, struct foo *arg2), (arg1, arg2));
+ * as above, "passlist" must use the same order and same names as "arglist"
+ *
+ * theoretically passlist is not necessary, but let's keep things simple and
+ * use exact same args on DECLARE and DEFINE.
+ */
+#define DECLARE_HOOK(hookname, arglist, passlist) \
+ extern struct hook _hook_##hookname; \
+ __attribute__((unused)) static inline void * \
+ _hook_typecheck_##hookname(int(*funcptr) HOOK_VOIDIFY arglist) \
+ { \
+ return (void *)funcptr; \
+ } \
+ __attribute__((unused)) static inline void \
+ *_hook_typecheck_arg_##hookname(int(*funcptr) \
+ HOOK_ADDDEF arglist) \
+ { \
+ return (void *)funcptr; \
+ } \
+ MACRO_REQUIRE_SEMICOLON() /* end */
+
+#define DECLARE_KOOH(hookname, arglist, passlist) \
+ DECLARE_HOOK(hookname, arglist, passlist)
+
+/* use in source file - contains hook-related definitions.
+ */
+#define DEFINE_HOOK_INT(hookname, arglist, passlist, rev) \
+ struct hook _hook_##hookname = { \
+ .name = #hookname, .entries = NULL, .reverse = rev, \
+ }; \
+ static int hook_call_##hookname HOOK_VOIDIFY arglist \
+ { \
+ int hooksum = 0; \
+ struct hookent *he = _hook_##hookname.entries; \
+ void *hookarg; \
+ union { \
+ void *voidptr; \
+ int(*fptr) HOOK_VOIDIFY arglist; \
+ int(*farg) HOOK_ADDDEF arglist; \
+ } hookp; \
+ for (; he; he = he->next) { \
+ hookarg = he->hookarg; \
+ hookp.voidptr = he->hookfn; \
+ if (!he->has_arg) \
+ hooksum += hookp.fptr passlist; \
+ else \
+ hooksum += hookp.farg HOOK_ADDARG passlist; \
+ } \
+ return hooksum; \
+ } \
+ MACRO_REQUIRE_SEMICOLON() /* end */
+
+#define DEFINE_HOOK(hookname, arglist, passlist) \
+ DEFINE_HOOK_INT(hookname, arglist, passlist, false)
+#define DEFINE_KOOH(hookname, arglist, passlist) \
+ DEFINE_HOOK_INT(hookname, arglist, passlist, true)
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _FRR_HOOK_H */