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>

configure.ac

@@ -55,6 +55,13 @@ dnl XXX add --pkgsrcrcdir to autoconf standard directory list somehow
 AC_SUBST(pkgsrcdir)
 AC_SUBST(pkgsrcrcdir)
 
+AC_ARG_WITH([moduledir], [AS_HELP_STRING([--with-moduledir=DIR], [module directory (${libdir}/frr/modules)])], [
+	moduledir="$withval"
+], [
+	moduledir="\${libdir}/frr/modules"
+])
+AC_SUBST([moduledir], [$moduledir])
+
 AC_ARG_ENABLE(tcmalloc,
 	AS_HELP_STRING([--enable-tcmalloc], [Turn on tcmalloc]),
 [case "${enableval}" in
@@ -1347,6 +1354,14 @@ int main(void);
    AC_DEFINE_UNQUOTED(AS_TR_CPP(SNMP_${SNMP_METHOD}),,SNMP method to interface with snmpd)
 fi
 
+dnl ------
+dnl dlopen
+dnl ------
+AC_SEARCH_LIBS(dlopen, [dl dld], [], [
+  AC_MSG_ERROR([unable to find the dlopen()])
+])
+
+
 dnl ---------------------------
 dnl sockaddr and netinet checks
 dnl ---------------------------
@@ -1646,14 +1661,18 @@ AC_DEFINE_UNQUOTED(VTYSH_BIN_PATH, "$vtysh_bin",path to vtysh binary)
 CFG_SYSCONF="$sysconfdir"
 CFG_SBIN="$sbindir"
 CFG_STATE="$frr_statedir"
+CFG_MODULE="$moduledir"
 for I in 1 2 3 4 5 6 7 8 9 10; do
 	eval CFG_SYSCONF="\"$CFG_SYSCONF\""
 	eval CFG_SBIN="\"$CFG_SBIN\""
 	eval CFG_STATE="\"$CFG_STATE\""
+	eval CFG_MODULE="\"$CFG_MODULE\""
 done
 AC_SUBST(CFG_SYSCONF)
 AC_SUBST(CFG_SBIN)
 AC_SUBST(CFG_STATE)
+AC_SUBST(CFG_MODULE)
+AC_DEFINE_UNQUOTED(MODULE_PATH, "$CFG_MODULE", path to modules)
 
 dnl ---------------------------
 dnl Check htonl works correctly
@@ -1728,6 +1747,7 @@ linker flags            : ${LDFLAGS} ${LIBS} ${LIBCAP} ${LIBREADLINE} ${LIBM}
 state file directory    : ${frr_statedir}
 config file directory   : `eval echo \`echo ${sysconfdir}\``
 example directory       : `eval echo \`echo ${exampledir}\``
+module directory        : ${CFG_MODULE}
 user to run as          : ${enable_user}
 group to run as         : ${enable_group}
 group for vty sockets   : ${enable_vty_group}

lib/Makefile.am

@@ -31,7 +31,9 @@ libfrr_la_SOURCES = \
 	spf_backoff.c \
 	libfrr.c \
 	strlcpy.c \
-	strlcat.c
+	strlcat.c \
+	module.c \
+	# end
 
 BUILT_SOURCES = route_types.h gitversion.h command_parse.h command_lex.h
 
@@ -54,6 +56,7 @@ pkginclude_HEADERS = \
 	monotime.h \
 	spf_backoff.h \
 	srcdest_table.h \
+	module.h \
 	libfrr.h \
 	# end
 

lib/libfrr.c

@@ -28,6 +28,7 @@
 #include "memory_vty.h"
 #include "zclient.h"
 #include "log_int.h"
+#include "module.h"
 
 const char frr_sysconfdir[] = SYSCONFDIR;
 const char frr_vtydir[] = DAEMON_VTY_DIR;
@@ -64,14 +65,16 @@ static const struct option lo_always[] = {
 	{ "help",        no_argument,       NULL, 'h' },
 	{ "version",     no_argument,       NULL, 'v' },
 	{ "daemon",      no_argument,       NULL, 'd' },
+	{ "module",      no_argument,       NULL, 'M' },
 	{ "vty_socket",  required_argument, NULL, OPTION_VTYSOCK },
 	{ NULL }
 };
 static const struct optspec os_always = {
-	"hvdi:",
+	"hvdM:",
 	"  -h, --help         Display this help and exit\n"
 	"  -v, --version      Print program version\n"
 	"  -d, --daemon       Runs in daemon mode\n"
+	"  -M, --module       Load specified module\n"
 	"      --vty_socket   Override vty socket path\n",
 	lo_always
 };
@@ -184,12 +187,18 @@ void frr_help_exit(int status)
 	exit(status);
 }
 
+struct option_chain {
+	struct option_chain *next;
+	const char *arg;
+};
+static struct option_chain *modules = NULL, **modnext = &modules;
 static int errors = 0;
 
 static int frr_opt(int opt)
 {
 	static int vty_port_set = 0;
 	static int vty_addr_set = 0;
+	struct option_chain *oc;
 	char *err;
 
 	switch (opt) {
@@ -203,6 +212,13 @@ static int frr_opt(int opt)
 	case 'd':
 		di->daemon_mode = 1;
 		break;
+	case 'M':
+		oc = XMALLOC(MTYPE_TMP, sizeof(*oc));
+		oc->arg = optarg;
+		oc->next = NULL;
+		*modnext = oc;
+		modnext = &oc->next;
+		break;
 	case 'i':
 		if (di->flags & FRR_NO_CFG_PID_DRY)
 			return 1;
@@ -298,6 +314,9 @@ int frr_getopt(int argc, char * const argv[], int *longindex)
 struct thread_master *frr_init(void)
 {
 	struct thread_master *master;
+	struct option_chain *oc;
+	struct frrmod_runtime *module;
+	char moderr[256];
 
 	srandom(time(NULL));
 
@@ -307,6 +326,17 @@ struct thread_master *frr_init(void)
 	zlog_set_level (ZLOG_DEST_SYSLOG, zlog_default->default_lvl);
 #endif
 
+	frrmod_init(di->module);
+	while (modules) {
+		modules = (oc = modules)->next;
+		module = frrmod_load(oc->arg, moderr, sizeof(moderr));
+		if (!module) {
+			fprintf(stderr, "%s\n", moderr);
+			exit(1);
+		}
+		XFREE(MTYPE_TMP, oc);
+	}
+
 	zprivs_init(di->privs);
 
 	master = thread_master_create();

lib/libfrr.h

@@ -26,6 +26,7 @@
 #include "thread.h"
 #include "log.h"
 #include "getopt.h"
+#include "module.h"
 
 #define FRR_NO_PRIVSEP		(1 << 0)
 #define FRR_NO_TCPVTY		(1 << 1)
@@ -40,6 +41,7 @@ struct frr_daemon_info {
 	const char *name;
 	const char *logname;
 	unsigned short instance;
+	struct frrmod_runtime *module;
 
 	char *vty_addr;
 	int vty_port;
@@ -67,15 +69,22 @@ struct frr_daemon_info {
  * i.e. "ZEBRA" or "BGP"
  *
  * note that this macro is also a latch-on point for other changes (e.g.
- * upcoming plugin support) that need to place some per-daemon things.  Each
+ * upcoming module support) that need to place some per-daemon things.  Each
  * daemon should have one of these.
  */
 #define FRR_DAEMON_INFO(execname, constname, ...) \
 	static struct frr_daemon_info execname ##_di = { \
 		.name = # execname, \
 		.logname = # constname, \
+		.module = THIS_MODULE, \
 		__VA_ARGS__ \
-	};
+	}; \
+	FRR_COREMOD_SETUP( \
+		.name = # execname, \
+		.description = # execname " daemon", \
+                .version = FRR_VERSION, \
+	) \
+	/* end */
 
 extern void frr_preinit(struct frr_daemon_info *daemon,
 		int argc, char **argv);

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

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 */