Weave failed to create bridge due to "bridge not supported" in WSL2?

[Aster-the-Med-Stu]

What you expected to happen?

There should be a bridge, allowing me to expose weave network to WSL2 machine.

What happened?

That bridge never shows up.

How to reproduce it?

$ weave launch

Anything else we need to know?

The log complains that bridge is not supported but actually I could create one using ip:

$ ip link add name bridge_test type bridge
$ ip link set dev bridge_test up
$ ip addr
[Redacted]
14: bridge_test: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
    link/ether 5a:c1:c2:88:91:c3 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::58c1:c2ff:fe88:91c3/64 scope link
       valid_lft forever preferred_lft forever

And from kernel flags in /proc/config.gz, CONFIG_BRIDGE is set to y, meaning that WSL2 kernel should support bridge. (Also there's a closed issue about supporting network bridge in WSL2 repo microsoft/WSL#4472)

Versions:

$ weave version
weave script 2.7.0
weave 2.7.0
$ docker version
Client: Docker Engine - Community
 Cloud integration  0.1.18
 Version:           19.03.13
 API version:       1.40
 Go version:        go1.13.15
 Git commit:        4484c46d9d
 Built:             Wed Sep 16 17:02:36 2020
 OS/Arch:           linux/amd64
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          19.03.13
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.13.15
  Git commit:       4484c46d9d
  Built:            Wed Sep 16 17:07:04 2020
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v1.3.7
  GitCommit:        8fba4e9a7d01810a393d5d25a3621dc101981175
 runc:
  Version:          1.0.0-rc10
  GitCommit:        dc9208a3303feef5b3839f4323d9beb36df0a9dd
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683
$ uname -a
Linux NAS 4.19.128-microsoft-standard #1 SMP Tue Jun 23 12:58:10 UTC 2020 x86_64 GNU/Linux

Logs:

WARN: 2020/10/14 07:30:13.600777 Skipping bridge creation of "bridged_fastdp" due to: : bridge not supported

INFO: 2020/10/14 07:30:13.725199 Bridge type is bridge

INFO: 2020/10/14 07:30:13.725273 Communication between peers via untrusted networks is encrypted.

INFO: 2020/10/14 07:30:13.750935 Our name is 7a:dd:37:e2:6b:03(docker-desktop)

INFO: 2020/10/14 07:30:13.751101 Launch detected - using supplied peer list: []

INFO: 2020/10/14 07:30:13.813599 Docker API on unix:///var/run/docker.sock: &[Components=[{"Details":{"ApiVersion":"1.40","Arch":"amd64","BuildTime":"2020-09-16T17:07:04.000000000+00:00","Experimental":"false","GitCommit":"4484c46d9d","GoVersion":"go1.13.15","KernelVersion":"4.19.128-microsoft-standard","MinAPIVersion":"1.12","Os":"linux"},"Name":"Engine","Version":"19.03.13"},{"Details":{"GitCommit":"8fba4e9a7d01810a393d5d25a3621dc101981175"},"Name":"containerd","Version":"v1.3.7"},{"Details":{"GitCommit":"dc9208a3303feef5b3839f4323d9beb36df0a9dd"},"Name":"runc","Version":"1.0.0-rc10"},{"Details":{"GitCommit":"fec3683"},"Name":"docker-init","Version":"0.18.0"}] Version=19.03.13 ApiVersion=1.40 GoVersion=go1.13.15 Os=linux Platform={"Name":"Docker Engine - Community"} MinAPIVersion=1.12 GitCommit=4484c46d9d Arch=amd64 KernelVersion=4.19.128-microsoft-standard BuildTime=2020-09-16T17:07:04.000000000+00:00]