Zebra: ADD Protobuf Encoding & Decoding for MLAG Messages

1. add the Mlag ProtoBuf Lib to Zebra Compilation
2. Encode the messages with protobuf before writing to MLAG
3. Decode the MLAG Messages using protobuf and write to clients
   based on their subscrption.

Signed-off-by: Satheesh Kumar K <sathk@cumulusnetworks.com>

Makefile.am

@@ -125,11 +125,11 @@ include doc/manpages/subdir.am
 include doc/developer/subdir.am
 include include/subdir.am
 include lib/subdir.am
+include mlag/subdir.am
 include zebra/subdir.am
 include watchfrr/subdir.am
 include qpb/subdir.am
 include fpm/subdir.am
-include mlag/subdir.am
 include grpc/subdir.am
 include tools/subdir.am
 include solaris/subdir.am

zebra/subdir.am

@@ -38,6 +38,9 @@ man8 += $(MANBUILD)/zebra.8
 endif
 
 zebra_zebra_LDADD = lib/libfrr.la $(LIBCAP)
+if HAVE_PROTOBUF
+zebra_zebra_LDADD += mlag/libmlag_pb.la $(PROTOBUF_C_LIBS)
+endif
 zebra_zebra_SOURCES = \
 	zebra/connected.c \
 	zebra/debug.c \
@@ -131,6 +134,7 @@ noinst_HEADERS += \
 	zebra/rtadv.h \
 	zebra/rule_netlink.h \
 	zebra/zebra_mlag.h \
+	zebra/zebra_mlag_private.h \
 	zebra/zebra_fpm_private.h \
 	zebra/zebra_l2.h \
 	zebra/zebra_dplane.h \