Add function to write DNS entries

Added function to write DNS entries to specified file
Also, added test case

Change-Id: I64250c7ee3cf7db3e7f8b5cf1669c7b4a7738637
Signed-off-by: Vishwanatha Subbanna <vishwa@linux.vnet.ibm.com>
diff --git a/test/Makefile.am b/test/Makefile.am
index 024fa25..5c70fbe 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -2,7 +2,7 @@
 
 TESTS = $(check_PROGRAMS)
 
-check_PROGRAMS = test
+check_PROGRAMS = test test_dns_updater
 
 test_SOURCES = \
 	test_util.cpp \
@@ -12,20 +12,30 @@
 	test_config_parser.cpp \
 	test_vlan_interface.cpp
 
-test_CPPFLAGS = -Igtest $(GTEST_CPPFLAGS) $(AM_CPPFLAGS)
+test_dns_updater_SOURCES = test_dns_updater.cpp
 
-test_CXXFLAGS = $(PTHREAD_CFLAGS) \
-				$(SYSTEMD_CFLAGS) \
-				$(SDBUSPLUS_CFLAGS) \
-				$(PHOSPHOR_LOGGING_CFLAGS) \
-				$(PHOSPHOR_DBUS_INTERFACES_CFLAGS)
+generic_cpp_flags = -Igtest $(GTEST_CPPFLAGS) $(AM_CPPFLAGS)
 
-test_LDFLAGS =	-lgtest_main -lgtest -lstdc++fs \
-				$(OESDK_TESTCASE_FLAGS) \
-				$(SYSTEMD_LIBS) \
-				$(SDBUSPLUS_LIBS) \
-				$(PHOSPHOR_LOGGING_LIBS) \
-				$(PHOSPHOR_DBUS_INTERFACES_LIBS)
+generic_cxx_flags = $(PTHREAD_CFLAGS) \
+					$(SYSTEMD_CFLAGS) \
+					$(SDBUSPLUS_CFLAGS) \
+					$(PHOSPHOR_LOGGING_CFLAGS) \
+					$(PHOSPHOR_DBUS_INTERFACES_CFLAGS)
+
+generic_ld_flags =  -lgtest_main -lgtest -lstdc++fs \
+					$(OESDK_TESTCASE_FLAGS) \
+					$(SYSTEMD_LIBS) \
+					$(SDBUSPLUS_LIBS) \
+					$(PHOSPHOR_LOGGING_LIBS) \
+					$(PHOSPHOR_DBUS_INTERFACES_LIBS)
+
+test_CPPFLAGS = ${generic_cpp_flags}
+test_CXXFLAGS = ${generic_cxx_flags}
+test_LDFLAGS  = ${generic_ld_flags}
+
+test_dns_updater_CPPFLAGS = ${generic_cpp_flags}
+test_dns_updater_CXXFLAGS = ${generic_cxx_flags}
+test_dns_updater_LDFLAGS  = ${generic_ld_flags}
 
 test_LDADD = $(top_builddir)/ethernet_interface.o \
 			$(top_builddir)/network_manager.o \
@@ -40,3 +50,5 @@
 			$(top_builddir)/vlan_interface.o \
 			$(top_builddir)/xyz/openbmc_project/Network/VLAN/Create/phosphor_network_manager-server.o \
 			$(top_builddir)/xyz/openbmc_project/Network/IP/Create/phosphor_network_manager-server.o
+
+test_dns_updater_LDADD = $(top_builddir)/dns_updater.o