[k8s] unable to SSH into cluster on K8s that use ipv6

[alex000kim]

1. I launched a lupyterlab server:

resources:
  cloud: kubernetes
  cpus: 16

workdir: .

setup: |
  pip install jupyterlab
run: |
  jupyter lab --no-browser --port 8888

2. When I am trying to do ssh port-forwarding, I get this:

$ ssh -L 8888:localhost:8888 alexkim-jupyter -v
OpenSSH_9.9p1, LibreSSL 3.3.6
debug1: Reading configuration data /Users/alexkim/.ssh/config
debug1: Reading configuration data /Users/alexkim/.sky/generated/ssh/alexkim-jupyter
debug1: /Users/alexkim/.sky/generated/ssh/alexkim-jupyter line 2: Applying options for alexkim-jupyter
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 21: include /etc/ssh/ssh_config.d/* matched no files
debug1: /etc/ssh/ssh_config line 54: Applying options for *
debug1: Authenticator provider $SSH_SK_PROVIDER did not resolve; disabling
debug1: Executing proxy command: exec ssh -tt -i ~/.sky/generated/ssh-keys/alexkim-jupyter.key -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o IdentitiesOnly=yes -W 2600:1f16:cf3:2520:f32c::c:22 sky@127.0.0.1 -o ProxyCommand='/Users/alexkim/.pyenv/versions/3.10.13/bin/python3.10 /Users/alexkim/.pyenv/versions/3.10.13/lib/python3.10/site-packages/sky/templates/websocket_proxy.py http://127.0.0.1:46580/ alexkim-jupyter'
debug1: identity file /Users/alexkim/.sky/generated/ssh-keys/alexkim-jupyter.key type -1
debug1: identity file /Users/alexkim/.sky/generated/ssh-keys/alexkim-jupyter.key-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_9.9
Bad stdio forwarding specification '2600:1f16:cf3:2520:f32c::c:22'
kex_exchange_identification: Connection closed by remote host
Connection closed by UNKNOWN port 65535

$ sky --version
skypilot, version 1.0.0.dev20250424
$ sky --commit
skypilot, commit 3d993746d92a6d4cc8802156663bce1a4bf15b92

a while back this PR fixed it #4497
but the issue is back again

[cg505]

What is the content of /Users/alexkim/.sky/generated/ssh/alexkim-jupyter?

[alex000kim]

$ cat /Users/alexkim/.sky/generated/ssh/alexkim-jupyter
# Added by sky (use `sky stop/down alexkim-jupyter` to remove)
Host alexkim-jupyter
  HostName 2600:1f16:cf3:2522:853b::a
  User sky
  IdentityFile /Users/alexkim/.sky/generated/ssh-keys/alexkim-jupyter.key
  IdentitiesOnly yes
  StrictHostKeyChecking no
  UserKnownHostsFile=/dev/null
  GlobalKnownHostsFile=/dev/null
  Port 22
  ProxyCommand ssh -tt -i ~/.sky/generated/ssh-keys/alexkim-jupyter.key -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o IdentitiesOnly=yes -W %h:%p sky@127.0.0.1 -o ProxyCommand='/Users/alexkim/miniforge3/bin/python3.12 /Users/alexkim/miniforge3/lib/python3.12/site-packages/sky/templates/websocket_proxy.py http://127.0.0.1:46580 alexkim-jupyter'

[romilbhardwaj]

Thanks @alex000kim, @kyuds is looking into this.

[kyuds]

@alex000kim @romilbhardwaj sorry for the late replies! Was a bit back-logged but will be able to resolve this soon!
done

[alex000kim]

I just tested that it works. Thanks so much for a quick turn around!