Using Bitcoin Core v0.15.1
I have just set onlynet=onion in my bitcoin.conf file and have the following in my logs after node restart:
2018-02-03 12:40:52 receive version message: /Satoshi:0.15.1/: version 70015, blocks=507429, us={IPv4}:{port), peer=0
2018-02-03 12:41:15 receive version message: /Satoshi:0.14.2/: version 70015, blocks=507429, us={IPv4}:{port), peer=2
2018-02-03 12:41:22 receive version message: /Satoshi:0.14.2/: version 70015, blocks=507429, us={IPv4}:{port), peer=3
2018-02-03 12:41:28 receive version message: /Satoshi:0.15.0/: version 70015, blocks=507429, us={IPv4}:{port), peer=4
2018-02-03 12:41:57 receive version message: /Satoshi:0.15.99/: version 70015, blocks=526679, us={IPv4}:{port), peer=5
...
2018-02-03 12:44:11 receive version message: /Satoshi:0.15.1/: version 70015, blocks=507429, us=[::]:0, peer=6
The peer 6 was an onion.
My bitcoin.conf file is as follows:
uacomment={redacted}
prune=10239
banscore=10
bantime=31536000
maxmempool=900
mempoolexpiry=2160
proxy=127.0.0.1:9050
listen=1
bind=127.0.0.1
onlynet=onion
All the Used for reaching peers via tick boxes are still ticked but disabled when I look in Options>Newtork.
Bitcoin Core should not initiate IPv4 (or IPv6) connections when onlynet=onion. These connections should not be seed nodes due to low addresses:
2018-02-03 12:40:30 Loaded 66198 addresses from peers.dat 254ms
I get some IPv4 version messages each time I restart the node.
Note: added both dns=0 and dnsseed=0 at the same time and this seems to resolve the issue with limited testing. These entries should not be necessary to limit IPv4 outgoing connect.
If people need to setup Tor for testing, the setup I have used is here on Bitcoin.SE
