Forwarding does not work

Set up is the following: "one" and "two" are the nodes that want to talk to each other. "three" is sitting in the middle forwarding for them.

|-----|  |-------|  |-----|
| one |--| three |--| two |
|-----|  |-------|  |-----|

$ git checkout feature/nixos-test-three-nodes # commit 006e6c967081d080ba29f7a5266534f74fa2b2b5
$ nix-build nix/test/simple-three-nodes.nix
[...]
one: INFO netmod_inet::session: Successfully peered with [fe80::5054:ff:fe12:a02%3]:9000
two: INFO netmod_inet::session: Successfully peered with [fe80::5054:ff:fe12:1402%3]:9000

but the ratcat address of host one never shows up in ratctl --get-peers on host two

host one:

$ ratctl --get-peers
3205-A09A-7C85-B88A-D258-D598-F4F1-D13C-C536-6627-A3A5-B5F1-040F-A554-8497-A026 (three)
359C-C4E1-AE20-74FF-A87E-754F-6005-23E9-C801-D4D1-93D8-B2CA-9C32-3AFE-2136-C81E (one)

host two:

$ ratctl --get-peers
3205-A09A-7C85-B88A-D258-D598-F4F1-D13C-C536-6627-A3A5-B5F1-040F-A554-8497-A026 (three)
E085-4DAF-1F6C-687C-1ED9-C58C-6636-075F-8FB6-DA7C-D019-CBFC-C508-2E97-34B3-DF73 (two)

host three:

$ ratctl --get-peers
3205-A09A-7C85-B88A-D258-D598-F4F1-D13C-C536-6627-A3A5-B5F1-040F-A554-8497-A026 (three)
359C-C4E1-AE20-74FF-A87E-754F-6005-23E9-C801-D4D1-93D8-B2CA-9C32-3AFE-2136-C81E (one)
E085-4DAF-1F6C-687C-1ED9-C58C-6636-075F-8FB6-DA7C-D019-CBFC-C508-2E97-34B3-DF73 (two)