lib, configure.ac: initial LTTng support

This commit adds initial support for LTTng.

When --enable-lttng=no or is not specified, no tracing code is included.
When --enable-lttng=yes, LTTng tracing events are (will be) generated.

configure.ac:
- add --enable-lttng
- define HAVE_LTTNG when enabled
- minimum LTTng version: 2.12.0

lib:
- add trace.[ch]
- update subdir.am

Signed-off-by: Quentin Young <qlyoung@nvidia.com>

configure.ac

@@ -566,6 +566,8 @@ AC_ARG_ENABLE([grpc],
   AS_HELP_STRING([--enable-grpc], [enable the gRPC northbound plugin]))
 AC_ARG_ENABLE([zeromq],
   AS_HELP_STRING([--enable-zeromq], [enable ZeroMQ handler (libfrrzmq)]))
+AC_ARG_ENABLE([lttng],
+  AS_HELP_STRING([--enable-lttng], [enable LTTng tracing]))
 AC_ARG_WITH([libpam],
   AS_HELP_STRING([--with-libpam], [use libpam for PAM support in vtysh]))
 AC_ARG_ENABLE([ospfapi],
@@ -1851,6 +1853,18 @@ if test "$enable_grpc" = "yes"; then
   ])
 fi
 
+dnl -----
+dnl LTTng
+dnl -----
+if test "$enable_lttng" = "yes"; then
+  PKG_CHECK_MODULES([UST], [lttng-ust >= 2.12.0], [
+    AC_DEFINE([HAVE_LTTNG], [1], [Enable LTTng support])
+    LTTNG=true
+  ], [
+    AC_MSG_ERROR([configuration specifies --enable-lttng but lttng-ust was not found])
+  ])
+fi
+
 dnl ------
 dnl ZeroMQ
 dnl ------

lib/subdir.am

@@ -3,7 +3,7 @@
 #
 lib_LTLIBRARIES += lib/libfrr.la
 lib_libfrr_la_LDFLAGS = -version-info 0:0:0 -Xlinker -e_libfrr_version
-lib_libfrr_la_LIBADD = $(LIBCAP) $(UNWIND_LIBS) $(LIBYANG_LIBS) $(LUA_LIB) $(LIBM)
+lib_libfrr_la_LIBADD = $(LIBCAP) $(UNWIND_LIBS) $(LIBYANG_LIBS) $(LUA_LIB) $(UST_LIBS) $(LIBM)
 
 lib_libfrr_la_SOURCES = \
 	lib/agg_table.c \
@@ -93,6 +93,7 @@ lib_libfrr_la_SOURCES = \
 	lib/table.c \
 	lib/termtable.c \
 	lib/thread.c \
+	lib/trace.c \
 	lib/typerb.c \
 	lib/typesafe.c \
 	lib/vector.c \
@@ -251,6 +252,7 @@ pkginclude_HEADERS += \
 	lib/table.h \
 	lib/termtable.h \
 	lib/thread.h \
+	lib/trace.h \
 	lib/typerb.h \
 	lib/typesafe.h \
 	lib/vector.h \

lib/trace.c

@@ -0,0 +1,4 @@
+#define TRACEPOINT_CREATE_PROBES
+#define TRACEPOINT_DEFINE
+
+#include "trace.h"

lib/trace.h

@@ -0,0 +1,50 @@
+/* Tracing
+ *
+ * Copyright (C) 2020  NVIDIA Corporation
+ * Quentin Young
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#if !defined(_TRACE_H) || defined(TRACEPOINT_HEADER_MULTI_READ)
+#define _TRACE_H
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif /* HAVE_CONFIG_H */
+
+#ifdef HAVE_LTTNG
+
+#undef TRACEPOINT_PROVIDER
+#define TRACEPOINT_PROVIDER frr_libfrr
+
+#undef TRACEPOINT_INCLUDE
+#define TRACEPOINT_INCLUDE "./trace.h"
+
+/* tracepoint definitions go here */
+
+#include <lttng/tracepoint.h>
+#include <lttng/tracepoint-event.h>
+
+#else /* HAVE_LTTNG */
+
+#define tracepoint(...)
+#define tracef(...)
+#define tracelog(...)
+#define tracepoint_enabled(...) true
+
+#endif /* HAVE_LTTNG */
+
+#endif /* _TRACE_H */