lib: add new gRPC-based northbound plugin

This is an experimental plugin for now. Full documentation will
come later.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

.gitignore

@@ -49,6 +49,7 @@
 *.pb.h
 *.pb-c.h
 *.pb-c.c
+*.pb.cc
 *_clippy.c
 
 ### dist

Makefile.am

@@ -123,6 +123,7 @@ include zebra/subdir.am
 include watchfrr/subdir.am
 include qpb/subdir.am
 include fpm/subdir.am
+include grpc/subdir.am
 include tools/subdir.am
 include solaris/subdir.am
 
@@ -198,6 +199,7 @@ EXTRA_DIST += \
 	doc/user/Makefile \
 	eigrpd/Makefile \
 	fpm/Makefile \
+	grpc/Makefile \
 	isisd/Makefile \
 	ldpd/Makefile \
 	lib/Makefile \

configure.ac

@@ -126,12 +126,15 @@ dnl Check CC and friends
 dnl --------------------
 dnl note orig_cflags is also used further down
 orig_cflags="$CFLAGS"
+orig_cxxflags="$CXXFLAGS"
 AC_LANG([C])
 AC_PROG_CC
 AC_PROG_CPP
+AC_PROG_CXX
 AM_PROG_CC_C_O
 dnl remove autoconf default "-g -O2"
 CFLAGS="$orig_cflags"
+CXXFLAGS="$orig_cxxflags"
 AC_PROG_CC_C99
 dnl NB: see C11 below
 
@@ -447,6 +450,8 @@ AC_ARG_ENABLE([confd],
   AS_HELP_STRING([--enable-confd=ARG], [enable confd integration]))
 AC_ARG_ENABLE([sysrepo],
   AS_HELP_STRING([--enable-sysrepo], [enable sysrepo integration]))
+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_WITH([libpam],
@@ -1678,6 +1683,25 @@ if test "$enable_sysrepo" = "yes"; then
 fi
 AM_CONDITIONAL([SYSREPO], [test "x$enable_sysrepo" = "xyes"])
 
+dnl ---------------
+dnl gRPC
+dnl ---------------
+if test "$enable_grpc" = "yes"; then
+  PKG_CHECK_MODULES([GRPC], [grpc grpc++ protobuf], [
+    AC_CHECK_PROGS([PROTOC], [protoc], [/bin/false])
+    if test "$PROTOC" = "/bin/false"; then
+      AC_MSG_FAILURE([grpc requested but protoc not found.])
+    fi
+
+    AC_DEFINE([HAVE_GRPC], [1], [Enable the gRPC northbound plugin])
+    GRPC=true
+  ], [
+    GRPC=false
+    AC_MSG_ERROR([grpc/grpc++ were not found on your system.])
+  ])
+fi
+AM_CONDITIONAL([GRPC], [test "x$enable_grpc" = "xyes"])
+
 dnl ---------------
 dnl math
 dnl ---------------

grpc/Makefile

@@ -0,0 +1,10 @@
+all: ALWAYS
+	@$(MAKE) -s -C .. grpc/libfrrgrpc_pb.la
+%: ALWAYS
+	@$(MAKE) -s -C .. grpc/$@
+
+Makefile:
+	#nothing
+ALWAYS:
+.PHONY: ALWAYS makefiles
+.SUFFIXES: