selftests/net: Add a test to validate behavior of rx timestamps

Validate the behavior of the combination of various timestamp socket
options, and ensure consistency across ip, udp, and tcp.

Signed-off-by: Mike Maloney <maloney@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/networking/timestamping/.gitignore

@@ -1,3 +1,4 @@
 timestamping
+rxtimestamp
 txtimestamp
 hwtstamp_config

tools/testing/selftests/networking/timestamping/Makefile

@@ -1,4 +1,6 @@
-TEST_PROGS := hwtstamp_config timestamping txtimestamp
+CFLAGS += -I../../../../../usr/include
+
+TEST_PROGS := hwtstamp_config rxtimestamp timestamping txtimestamp
 
 all: $(TEST_PROGS)