P2P: Node with onlynet=ipv6 connects outgoing to Onion #13378

Running bitcoind 0.16.1rc1 64-Bit binary release on Linux

What I did

I have now setup IPv6 connection for my node (but only outgoing, since my providers router does not allow incoming IPv6 traffic...) I have running also Tor on localhost with bitcoin (not really) "hidden" service, in parallel to IPv4.

So I was curious and set onlynet=ipv6 in bitcoin.conf (before, "onlynet" was not set)

Expected behavior

Only IPv6 connections, both incoming and outgoing, no Tor traffic, no traffic to local Tor hidden service.

Actual behavior

Node connects to IPv6, IPv4 and Tor, see screenshot of GUI debug window connection tab.

Also, there are error messages in the debug log that I had not before: ("Keine Berechtigung" means "No permission" in English)

2018-06-03 12:41:46 Loaded 71277 addresses from peers.dat 324ms 2018-06-03 12:41:46 init message: Lade Sperrliste... 2018-06-03 12:41:46 init message: Starte Netzwerk-Threads... 2018-06-03 12:41:46 init message: Laden abgeschlossen 2018-06-03 12:41:46 opencon thread start 2018-06-03 12:41:46 net thread start 2018-06-03 12:41:46 dnsseed thread start 2018-06-03 12:41:46 addcon thread start 2018-06-03 12:41:46 msghand thread start 2018-06-03 12:41:46 GUI: Platform customization: "other" 2018-06-03 12:41:46 GUI: PaymentServer::LoadRootCAs: Loaded 159 root certificates 2018-06-03 12:41:55 Imported mempool transactions from disk: 2019 succeeded, 0 failed, 0 expired, 0 already there 2018-06-03 12:41:57 Loading addresses from DNS seeds (could take a while) 2018-06-03 12:41:57 219 addresses found from DNS seeds 2018-06-03 12:41:57 dnsseed thread exit 2018-06-03 12:42:07 New outbound peer connected: version: 70015, blocks=525773, peer=0 2018-06-03 12:44:06 GUI: QAccessibleTable::child: Invalid index at: 3 0 2018-06-03 12:44:06 GUI: Cannot creat accessible child interface for object: QTableView(0x55960b4b1040, name = "peerWidget") index: 29 2018-06-03 12:44:06 GUI: QAccessibleTable::child: Invalid index at: 3 0 2018-06-03 12:44:06 GUI: Cannot creat accessible child interface for object: QTableView(0x55960b4b1040, name = "peerWidget") index: 29 2018-06-03 12:44:06 GUI: QAccessibleTable::child: Invalid index at: 3 0 2018-06-03 12:44:06 GUI: Cannot creat accessible child interface for object: QTableView(0x55960b4b1040, name = "peerWidget") index: 29 2018-06-03 12:44:11 GUI: QAccessibleTable::child: Invalid index at: 2 0 2018-06-03 12:44:11 GUI: Cannot creat accessible child interface for object: QTableView(0x55960b4b1040, name = "peerWidget") index: 22 2018-06-03 12:44:11 GUI: QAccessibleTable::child: Invalid index at: 2 0 2018-06-03 12:44:11 GUI: Cannot creat accessible child interface for object: QTableView(0x55960b4b1040, name = "peerWidget") index: 22 2018-06-03 12:44:11 GUI: QAccessibleTable::child: Invalid index at: 2 0 2018-06-03 12:44:11 GUI: Cannot creat accessible child interface for object: QTableView(0x55960b4b1040, name = "peerWidget") index: 22 2018-06-03 12:44:51 connect() to [2601:98a:4203:6e9d:68b9:19cf:e683:6932]:8333 failed after select(): Keine Berechtigung (13) 2018-06-03 12:45:33 connect() to [2a00:c1a0:4888:a500:cc5b:3e64:8aba:d6b4]:8333 failed after select(): Keine Berechtigung (13) 2018-06-03 12:45:38 connect() to [2001:981:9cae:1:7c4b:8f56:ab7c:78f]:8333 failed after select(): Keine Berechtigung (13)

When setting onlynet=ipv4 there are outgoing connections to .onion addresses, too.

The bitcoind man page says:

-onlynet=<net> Only connect to nodes in network <net> (ipv4, ipv6 or onion)

Additionally, I get incoming connections via Tor Hidden Service with both onlynet=ipv6 and onlynet=ipv4.

If this should be not a bug, but a feature, the man page should explain this behaviour more detailed and precisely.

I am wondering, that there is no feedback yet about this behavior. I think it is easy reproducable.

Onlynet only affects outgoing connections, not incoming.

Thanks for feedback. Following this, I would suggest to change the man page text to:

onlynet=
Actively connect to remote nodes exclusively in network <ipv4|ipv6|onion>.
Passive, incoming connections are not affected by this parameter.

But this statement for active connections to remote nodes does not seem to match the reality, currently. Or am I missing something?

Thanks for feedback. Following this, I would suggest to change the man page text to:

Sounds good to me. Feel free to open a PR.

But this statement for active connections to remote nodes does not seem to match the reality, currently. Or am I missing something?

If that's the case, there is a bug, and we should keep this issue open to investigate. I was just commenting because the in/out distinction was a possible explanation for what you saw.

@sipa

Onlynet only affects outgoing connections, not incoming.

Huh. So a onlynet=tor user may end up getting non-tor incoming connections? That sounds potentially undesirable.

Edit: off-topic; spin off in #13436, please respond there.

I got the node now running for 48h with onlynet=ipv6, and from looking at the connections tab from time to time, I only once saw a single outgoing connection via IPv6, so pretty seldomly. All of the other outgoing connections are to Onion addresses. I never saw an outgoing connection via IPv4.

netstat -np | grep tor shows only IPv4 connections, allthough Tor is configured with ClientUseIPv6 1, so it looks like this is not a "Onion via IPv6" phaenomen.

Issue still exists with 0.21.0rc2, see screenshot of connection table running with onlynet=ipv6.

There are no outgoing onion connections when additionally to onlynet=ipv6 setting listenonion=0 (default: 1). See #14425 (closed by me) and the successor PR #19358

Check if this is solved by #22651.