lib: dynamic module loading

This adds a "-M" option to each daemon, to load dynamic modules at
startup.  Modules are by default located in /usr/lib/frr/modules (lib64
if appropriate).  Unloading or loading at runtime is not supported at
this point to keep things simple.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

1 files changed, 104 insertions, 0 deletions

diff --git a/lib/module.h b/lib/module.h
new file mode 100644
index 0000000000..cb66e60976
--- /dev/null
+++ b/lib/module.h
@@ -0,0 +1,104 @@
+/*
+ * Copyright (c) 2015-16  David Lamparter, for NetDEF, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef _FRR_MODULE_H
+#define _FRR_MODULE_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#if !defined(__GNUC__)
+# error module code needs GCC visibility extensions
+#elif __GNUC__ < 4
+# error module code needs GCC visibility extensions
+#else
+# define DSO_PUBLIC __attribute__ ((visibility ("default")))
+# define DSO_SELF   __attribute__ ((visibility ("protected")))
+# define DSO_LOCAL  __attribute__ ((visibility ("hidden")))
+#endif
+
+struct frrmod_runtime;
+
+struct frrmod_info {
+	/* single-line few-word title */
+	const char *name;
+	/* human-readable version number, should not contain spaces */
+	const char *version;
+	/* one-paragraph description */
+	const char *description;
+
+	int (*init)(void);
+};
+
+/* primary entry point structure to be present in loadable module under
+ * "_frrmod_this_module" dlsym() name
+ *
+ * note space for future extensions is reserved below, so other modules
+ * (e.g. memory management, hooks) can add fields
+ *
+ * const members/info are in frrmod_info.
+ */
+struct frrmod_runtime {
+	struct frrmod_runtime *next;
+
+	const struct frrmod_info *info;
+	void *dl_handle;
+	bool finished_loading;
+
+	char *load_name;
+	char *load_args;
+};
+
+/* space-reserving foo */
+struct _frrmod_runtime_size {
+	struct frrmod_runtime r;
+	/* this will barf if frrmod_runtime exceeds 1024 bytes ... */
+	uint8_t space[1024 - sizeof(struct frrmod_runtime)];
+};
+union _frrmod_runtime_u {
+	struct frrmod_runtime r;
+	struct _frrmod_runtime_size s;
+};
+
+extern union _frrmod_runtime_u _frrmod_this_module;
+#define THIS_MODULE (&_frrmod_this_module.r)
+
+#define FRR_COREMOD_SETUP(...) \
+	static const struct frrmod_info _frrmod_info = { __VA_ARGS__ }; \
+	DSO_LOCAL union _frrmod_runtime_u _frrmod_this_module = { \
+		.r.info = &_frrmod_info, \
+	};
+#define FRR_MODULE_SETUP(...) \
+	FRR_COREMOD_SETUP(__VA_ARGS__) \
+	DSO_SELF struct frrmod_runtime *frr_module = &_frrmod_this_module.r;
+
+extern struct frrmod_runtime *frrmod_list;
+
+extern void frrmod_init(struct frrmod_runtime *modinfo);
+extern struct frrmod_runtime *frrmod_load(const char *spec,
+		char *err, size_t err_len);
+#if 0
+/* not implemented yet */
+extern void frrmod_unload(struct frrmod_runtime *module);
+#endif
+
+#endif /* _FRR_MODULE_H */