make -C tools/testing/selftests TARGETS="net/for<GS=ipip_flat_gre_key.sh TEST_GEN_PROGS="" run_tests   
make: Entering directory '/srv/vmksft/testing/wt-3/tools/testing/selftests'
make[1]: Nothing to be done for 'all'.
TAP version 13
1..1
# timeout set to 10800
# selftests: net/forwarding: ipip_flat_gre_key.sh
# 6.12 [+6.12] TEST: ping gre flat with key                                        [ OK ]
# 12.13 [+6.01] TEST: ping gre packet size 1800 after MTU change                    [ OK ]
ok 1 selftests: net/forwarding: ipip_flat_gre_key.sh
make: Leaving directory '/srv/vmksft/testing/wt-3/tools/testing/selftests'
xx__-> echo $?
0
xx__->