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, 159 insertions, 0 deletions

diff --git a/lib/module.c b/lib/module.c
new file mode 100644
index 0000000000..4ebe3c0da2
--- /dev/null
+++ b/lib/module.c
@@ -0,0 +1,159 @@
+/*
+ * 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.
+ */
+
+#include "config.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <limits.h>
+#include <dlfcn.h>
+
+#include "module.h"
+#include "memory.h"
+#include "version.h"
+
+DEFINE_MTYPE_STATIC(LIB, MODULE_LOADNAME, "Module loading name")
+DEFINE_MTYPE_STATIC(LIB, MODULE_LOADARGS, "Module loading arguments")
+
+static struct frrmod_info frrmod_default_info = {
+	.name = "libfrr",
+	.version = FRR_VERSION,
+	.description = "libfrr core module",
+};
+union _frrmod_runtime_u frrmod_default = {
+	.r.info = &frrmod_default_info,
+	.r.finished_loading = 1,
+};
+
+// if defined(HAVE_SYS_WEAK_ALIAS_ATTRIBUTE)
+// union _frrmod_runtime_u _frrmod_this_module
+//	__attribute__((weak, alias("frrmod_default")));
+// elif defined(HAVE_SYS_WEAK_ALIAS_PRAGMA)
+#pragma weak _frrmod_this_module = frrmod_default
+// else
+// error need weak symbol support
+// endif
+
+struct frrmod_runtime *frrmod_list = &frrmod_default.r;
+static struct frrmod_runtime **frrmod_last = &frrmod_default.r.next;
+static const char *execname = NULL;
+
+void frrmod_init(struct frrmod_runtime *modinfo)
+{
+	modinfo->finished_loading = 1;
+	*frrmod_last = modinfo;
+	frrmod_last = &modinfo->next;
+
+	execname = modinfo->info->name;
+}
+
+struct frrmod_runtime *frrmod_load(const char *spec,
+		char *err, size_t err_len)
+{
+	void *handle = NULL;
+	char name[PATH_MAX], fullpath[PATH_MAX], *args;
+	struct frrmod_runtime *rtinfo, **rtinfop;
+	const struct frrmod_info *info;
+
+	snprintf(name, sizeof(name), "%s", spec);
+	args = strchr(name, ':');
+	if (args)
+		*args++ = '\0';
+
+	if (!strchr(name, '/')) {
+		if (!handle && execname) {
+			snprintf(fullpath, sizeof(fullpath), "%s/%s_%s.so",
+					MODULE_PATH, execname, name);
+			handle = dlopen(fullpath, RTLD_NOW | RTLD_GLOBAL);
+		}
+		if (!handle) {
+			snprintf(fullpath, sizeof(fullpath), "%s/%s.so",
+					MODULE_PATH, name);
+			handle = dlopen(fullpath, RTLD_NOW | RTLD_GLOBAL);
+		}
+	}
+	if (!handle) {
+		snprintf(fullpath, sizeof(fullpath), "%s", name);
+		handle = dlopen(fullpath, RTLD_NOW | RTLD_GLOBAL);
+	}
+	if (!handle) {
+		if (err)
+			snprintf(err, err_len,
+					"loading module \"%s\" failed: %s",
+					name, dlerror());
+		return NULL;
+	}
+
+	rtinfop = dlsym(handle, "frr_module");
+	if (!rtinfop) {
+		dlclose(handle);
+		if (err)
+			snprintf(err, err_len,
+					"\"%s\" is not a Quagga module: %s",
+					name, dlerror());
+		return NULL;
+	}
+	rtinfo = *rtinfop;
+	rtinfo->load_name = XSTRDUP(MTYPE_MODULE_LOADNAME, name);
+	rtinfo->dl_handle = handle;
+	if (args)
+		rtinfo->load_args = XSTRDUP(MTYPE_MODULE_LOADARGS, args);
+	info = rtinfo->info;
+
+	if (rtinfo->finished_loading) {
+		dlclose(handle);
+		if (err)
+			snprintf(err, err_len,
+					"module \"%s\" already loaded",
+					name);
+		goto out_fail;
+	}
+
+	if (info->init && info->init()) {
+		dlclose(handle);
+		if (err)
+			snprintf(err, err_len,
+					"module \"%s\" initialisation failed",
+					name);
+		goto out_fail;
+	}
+
+	rtinfo->finished_loading = 1;
+
+	*frrmod_last = rtinfo;
+	frrmod_last = &rtinfo->next;
+	return rtinfo;
+
+out_fail:
+	if (rtinfo->load_args)
+		XFREE(MTYPE_MODULE_LOADARGS, rtinfo->load_args);
+	XFREE(MTYPE_MODULE_LOADNAME, rtinfo->load_name);
+	return NULL;
+}
+
+#if 0
+void frrmod_unload(struct frrmod_runtime *module)
+{
+}
+#endif