KASM VLAN config issue post 1.15.0+ images

[Kabe0]

Existing Resources

• [x] Please search the existing issues for related problems
• [x] Consult the product documentation : Docs
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• [x] Consult the Troubleshooting Guide : Guide
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Describe the bug When working with restricted networking, I have a consistent problem with the container sessions starting properly, but the VNC connection never succeeding. This all started after the 1.15.0 builds. The 1.15.0 build behave properly, and connect to the VLAN network as expected.

To Reproduce Steps to reproduce the behavior:

1. configure a VLAN network interface. I have created one such as

        vlan15: connected to developers
        "vlan15"
        inet4 10.19.48.2/24
        route4 10.19.48.0/24 metric 400

2. Setup the docker vlan config docker network create --id -d ipvlan --subnet=10.19.48.0/24 --gateway=10.19.48.1 --aux-address="local=10.19.48.2" -o ipvlan_mode=l2 -o parent=vlan15 z_developer-net

3. Go to workspaces, and update a workspace to be restricted networks, and set "z_developer-net" as the network.

4. Login to the front-end portal and connect to the workspace. Inspect and watch the 503 errors on the VNC connection

https://domain.com/<uuid>/vnc/vnc.html?video_quality=3&enable_webp=false&idle_disconnect=20&password=&autoconnect=1&path=desktop/<uuid>f/vnc/websockify&cursor=true&resize=remote&clipboard_up=true&clipboard_down=false&clipboard_seamless=true&toggle_control_panel=null

Expected behavior VNC connects and opens up the window session. This image is working fine kasmweb/ubuntu-focal-dind-rootless:1.15.0, as well as kasmweb/fedora-39-desktop:1.15.0. Any of the later images these versions or other releases fail.

Workspaces Version Version 1.17

Workspaces Installation Method Single Server

Client Browser (please complete the following information):

• OS: Linux
• Browser Chrome, (Firefox too)
• Version 136.0.71

Workspace Server Information (please provide the output of the following commands):

• Linux 5.14.0-503.40.1.el9_5.x86_64 #1 SMP PREEMPT_DYNAMIC Thu Apr 24 08:27:29 EDT 2025 x86_64 x86_64 x86_64 GNU/Linux
• Red Hat Enterprise Linux - 9.5
• docker: 28.1.1

f2e8e141df64   kasmweb/proxy:1.17.0                    "/docker-entrypoint.…"   About an hour ago   Up About an hour             80/tcp, 0.0.0.0:443->443/tcp, [::]:443->443/tcp   kasm_proxy
8a2b2940673f   kasmweb/rdp-https-gateway:1.17.0        "/opt/rdpgw/rdpgw"       About an hour ago   Up About an hour (healthy)                                                     kasm_rdp_https_gateway
b6936acfe824   kasmweb/rdp-gateway:1.17.0              "/start.sh"              About an hour ago   Up About an hour (healthy)   0.0.0.0:3389->3389/tcp, [::]:3389->3389/tcp       kasm_rdp_gateway
5b2a97f0e089   kasmweb/agent:1.17.0                    "python3 /src/Provis…"   About an hour ago   Up About an hour (healthy)   4444/tcp                                          kasm_agent
915bd45ad54d   kasmweb/api:1.17.0                      "/bin/sh -c /usr/bin…"   About an hour ago   Up About an hour (healthy)   8080/tcp                                          kasm_api
737fe372c68f   kasmweb/share:1.17.0                    "python3 /src/api_se…"   About an hour ago   Up About an hour (healthy)   8182/tcp                                          kasm_share
a84275d6d9e3   kasmweb/manager:1.17.0                  "python3 /src/api_se…"   About an hour ago   Up About an hour (healthy)   8181/tcp                                          kasm_manager
d359e1438503   kasmweb/postgres:1.17.0                 "docker-entrypoint.s…"   About an hour ago   Up About an hour (healthy)   0.0.0.0:5432->5432/tcp, [::]:5432->5432/tcp       kasm_db
56b008598d2a   redis:5-alpine                          "docker-entrypoint.s…"   About an hour ago   Up About an hour             6379/tcp                                          kasm_redis
8d093e0b7037   kasmweb/kasm-guac:1.17.0                "/dockerentrypoint.sh"   About an hour ago   Up About an hour (healthy)                                                     kasm_guac