traceroute does not stop on subnet router anycast addresses on linux routers

[ChrisRol99]

Hi,

I filed a bugreport(https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1055978) on the debian package 'mtr-tiny' and they told me I should open a github issue.

The problem is, that the traceroute does not terminate if the target is a anycast address, below i presented an example and attached some network traces.

I prepared a test setup and captured two traces of the network. The test consists of three linux routers which are connected as follows: R1 <-> R2 <-> R3 (see test_setup.png)

1st trace(intended_behavior.pcap) works as expected:
From R1 to R3:
mtr -c 1 2001:db8:0:3::1
Host Loss% Snt Last Avg Best Wrst StDev

1. 2001:db8:0:1::2 0.0% 1 1.0 1.0 1.0 1.0 0.0
2. 2001:db8:0:3::1 0.0% 1 1.4 1.4 1.4 1.4 0.0

2nd trace(unintended_behavior.pcap) does not stop, because I try to reach the anycast address:
mtr -c 1 2001:db8:0:3::
Host Loss% Snt Last Avg Best Wrst StDev

1. 2001:db8:0:1::2 0.0% 1 1.0 1.0 1.0 1.0 0.0
2. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
3. 2001:db8:0:2::2 0.0% 1 1.3 1.3 1.3 1.3 0.0
4. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
5. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
6. 2001:db8:0:2::2 0.0% 1 1.0 1.0 1.0 1.0 0.0
7. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
8. 2001:db8:0:2::2 0.0% 1 1.2 1.2 1.2 1.2 0.0
9. 2001:db8:0:2::2 0.0% 1 1.4 1.4 1.4 1.4 0.0
10. 2001:db8:0:2::2 0.0% 1 1.2 1.2 1.2 1.2 0.0
11. 2001:db8:0:2::2 0.0% 1 1.3 1.3 1.3 1.3 0.0
12. 2001:db8:0:2::2 0.0% 1 1.4 1.4 1.4 1.4 0.0
13. 2001:db8:0:2::2 0.0% 1 1.2 1.2 1.2 1.2 0.0
14. 2001:db8:0:2::2 0.0% 1 1.3 1.3 1.3 1.3 0.0
15. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
16. 2001:db8:0:2::2 0.0% 1 1.1 1.1 1.1 1.1 0.0
17. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
18. 2001:db8:0:2::2 0.0% 1 1.3 1.3 1.3 1.3 0.0
19. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
20. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
21. 2001:db8:0:2::2 0.0% 1 1.3 1.3 1.3 1.3 0.0
22. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
23. 2001:db8:0:2::2 0.0% 1 1.3 1.3 1.3 1.3 0.0
24. 2001:db8:0:2::2 0.0% 1 1.5 1.5 1.5 1.5 0.0
25. 2001:db8:0:2::2 0.0% 1 1.4 1.4 1.4 1.4 0.0
26. 2001:db8:0:2::2 0.0% 1 1.2 1.2 1.2 1.2 0.0
27. 2001:db8:0:2::2 0.0% 1 1.4 1.4 1.4 1.4 0.0
28. 2001:db8:0:2::2 0.0% 1 1.2 1.2 1.2 1.2 0.0
29. 2001:db8:0:2::2 0.0% 1 1.4 1.4 1.4 1.4 0.0
30. 2001:db8:0:2::2 0.0% 1 1.4 1.4 1.4 1.4 0.0

Network traces:
networkTrace.tar.gz

Summary of my problem:
BUG: An ICMP reply should be interpreted as a "destination reached"
Wishlist: tag the IP when the address doesn't match the destination
we're targetting.

[rewolff]

With "ICMP reply's" coming back, MTR should conclude that the
destination has been reached and not probe further. No half-assed
workarounds with "after three hops the same IP assume we won't get
anything new when going further".

BUG: An ICMP reply should be interpreted as a "destination reached"
Wishlist: tag the IP when the address doesn't match the destination
we're targetting.

[yvs2014]

in some way it's probably similar to trace of some network or unspecified target ip address, if I'm not mistaken something like mtr -n 0