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Tuinslak
Asked: 2021-02-23 07:17:18 +0800 CST

Make Docker listen to the IPv6 address of server, forward IPv6 requests to right container

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My server is running on both IPv4 and IPv6. Docker is running on (local) IPv4 addresses (ie 192.168.100.1/24). I did not enable IPv6 inside daemon.json as I understand that to be rather buggy and requires me to have a full IPv6 /64 range available.

For example, a reverse-proxy nginx docker container is running at superuser.one -- that IP is accessible both over IPv4 and IPv6.

# dig superuser.one +short a
85.17.140.73
# dig superuser.one +short aaaa
2001:1af8:4200:a003:1:aaaa:0:123

And IPv6 is working:

# ping6 superuser.one -c 1
PING superuser.one(2001:1af8:4200:a003:1:aaaa:0:123 (2001:1af8:4200:a003:1:aaaa:0:123)) 56 data bytes
64 bytes from 2001:1af8:4200:a003:1:aaaa:0:123 (2001:1af8:4200:a003:1:aaaa:0:123): icmp_seq=1 ttl=57 time=19.5 ms

--- superuser.one ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 19.526/19.526/19.526/0.000 ms

However, when accessing the webserver (or other services running behind Docker), IPv6 doesn't work:

# curl https://superuser.one -6 -I
curl: (7) Failed to connect to superuser.one port 443: Connection refused

While IPv4 works fine:

# curl https://superuser.one -4 -I
HTTP/2 200
server: nginx
date: Mon, 22 Feb 2021 15:10:37 GMT
[...]

How can I get Docker to listen to the server's IPv6 address and forward the request to the right container (using the regular bridge or host network already set up)?

Edit 1:

ip -6 addr: https://pastebin.com/zKkZW6CE

# docker network ls
NETWORK ID     NAME            DRIVER    SCOPE
4ea1dddd3d64   0x04            bridge    local
c6ad6c596ec5   bridge          bridge    local
5d5ea78ff91f   host            host      local
7a03e7ecb430   matrix          bridge    local
20cb1fbc5dfe   matrix-coturn   bridge    local
684af653d87a   none            null      local

docker network inspect 0x04: https://pastebin.com/tWYNyM3Y

Edit 2:

I cleared my daemon.json file as I had the following content:

"ipv6": true,
"fixed-cidr-v6": "fd00::/80"

This means I can now correctly run IPv4 and IPv6 connections on my bridge network:

ipv4 and ipv6 working

However, this doesn't seem to work with --network option. Most my containers are running in their own network.

ipv6 docker ipv4

1 Answers

  1. You can just declare a normal port forward during container creation, using

    -p [2001:dead:beef::1]:22:22

    That creates an IPv6 socket on the host that is forwarded to an IPv4 socket inside the container.

    To listen to any IPv6 address, use [::] as the listen address.

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