Testing MPLS from Linux kernel 4.12. The trace route is duplicete pe-p hop. This is not visible MPLS label on traceroute.
root@ne-vlezay80:~# traceroute -e 10.10.10.4 traceroute to 10.10.10.4 (10.10.10.4), 30 hops max, 60 byte packets 1 10.5.5.1 (10.5.5.1) 0.028 ms 0.005 ms 0.006 ms 2 10.4.4.2 (10.4.4.2) 0.021 ms 0.007 ms 0.012 ms 3 10.4.4.2 (10.4.4.2) 0.008 ms 0.008 ms 0.007 ms 4 10.10.10.4 (10.10.10.4) 0.015 ms 0.009 ms 0.008 ms root@ne-vlezay80:~#