Adding upstream version 8.4.4.upstream/8.4.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 254 insertions, 0 deletions

diff --git a/lib/hook.h b/lib/hook.h
new file mode 100644
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--- /dev/null
+++ b/lib/hook.h
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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 */