Not getting any ipv6 connections #20021

I restarted my Bitcoin full node yesterday after a cable repair outside my house. I'm using the latest version of the Bitcoin software (master branch) which has the (new) -netinfo rpc option (#19643).

bitcoin-cli -netinfo shows:

Bitcoin Core v0.20.99.0-1b313cacc - 70016/Satoshi:0.20.99/

        ipv4    ipv6   onion   total  block-relay
in        61       0      13      74       7
out        5       0       5      10       2
total     66       0      18      84       9

Why are there no ipv6 connectoins?

System: Ubuntu 18.04.5 LTS

I'm on an ipv4 internet address myself but as far as I know that shouldn't matter.

cat /proc/sys/net/ipv6/conf/all/disable_ipv6 gives 0, so ipv6 is not disabled on my system.

Turning off ufw didn't help.

debug.log tells me:

2020-09-25T13:40:53Z Bound to [::]:8333

2020-09-25T13:40:53Z Bound to 0.0.0.0:8333

bitcoin-cli getnetworkinfo

 "networks": [
    {
      "name": "ipv4",
      "limited": false,
      "reachable": true,
      "proxy": "",
      "proxy_randomize_credentials": false
    },
    {
      "name": "ipv6",
      "limited": false,
      "reachable": true,
      "proxy": "",
      "proxy_randomize_credentials": false
    },
    {
      "name": "onion",
      "limited": false,
      "reachable": true,
      "proxy": "127.0.0.1:9050",
      "proxy_randomize_credentials": true
    }
  ],

I tried adding 2 ipv6 outbound peers via rpc but they don't show up.

What was the command, you´ve added the IPv6 nodes with?

@n-thumann the command was:

bitcoin-cli addnode "[2a01:4f8:10b:41::2]:8333" add

bitcoin-cli getaddednodeinfo gives:

[
  {
    "addednode": "[2a01:4f8:161:7304::2]:8333",
    "connected": false,
    "addresses": [
    ]
  },
  {
    "addednode": "[2a01:4f8:10b:41::2]:8333",
    "connected": false,
    "addresses": [
    ]
  }
]

Hm, thought this could be related to #19643 (review), but doesn´t look like that. getaddednodeinfo says that the node isn´t connected at all, so is it even connected properly? Is the node in getpeerinfo?

It's not in getpeerinfo. For example; bitcoin-cli getpeerinfo | grep 4f8 returns nothing

Then the node isn´t connected at all and is therefore not shown in -netinfo or getpeerinfo. Try having a look into debug.log if the connection is refused or something, or try Wireshark 😊

In debug.log I see:

2020-09-26T06:59:08Z connect() to [2a01:4f8:161:7304::2]:8333 failed: Network is unreachable (101)

Looks like your system has no idea how to route to this network. Do you have proper v6 connectivity? What do traceroute 2a01:4f8:161:7304::2 or ip -6 route show?

ip -6 route give:

fe80::/64 dev eth0 proto kernel metric 100 pref medium
fe80::/64 dev eth0 proto kernel metric 256 pref medium

ip -4 route gives;

default via 192.168.178.1 dev eth0 proto static metric 100 
169.254.0.0/16 dev eth0 scope link metric 1000 
192.168.178.0/24 dev eth0 proto kernel scope link src 192.168.178.20 metric 100 

traceroute 2a01:4f8:161:7304::2 gives:

traceroute to 2a01:4f8:161:7304::2 (2a01:4f8:161:7304::2), 30 hops max, 80 byte packets connect: Network is unreachable

Yeah, you only have Link-Local IPv6 connectivity (so only within your local network), but not "the internet". If your ISP actually provides you with v6 connectivity, you can add a default route manually. If not, there´s no way for you to reach this server via IPv6.

Ah, thanks a lot for all your help. For now, I'll close this issue. Nevertheless, it shows how useful the -netinfo rpc call is :-)