Kubernetes and DLNA

These are some notes taken while deploying a Digital Living Network Alliance (DLNA) to Kubernetes. DLNA is derived from Universal Plug and Play (UPnP) specifically for media interoperability. DLNA services are advertised and discovered via Simple Service Discovery Protocol (SSDP).

Take the follow DLNA interaction:

DLNA M-SEARCH Interaction diagram

Let’s have a look at a captured interaction with tshark.

sudo tshark -i eno1  -f "udp port 1900"
Capturing on 'eno1'
   ...
   12 10.641536725 192.168.0.85 → 239.255.255.250 SSDP 169 M-SEARCH * HTTP/1.1
   13 10.643129842 192.168.0.211 → 192.168.0.85 SSDP 404 HTTP/1.1 200 OK

We can see the SSDP port in our DLNA Deployment Kubernetes manifest.

ports:
- containerPort: 1900
  hostPort: 1900
  protocol: UDP

If we run tshark with -T pdml to examine the contents of the interaction the server - we will see an advertised http endpoint.

http://192.168.0.211:8200/rootDesc.xml

You also discover the advertised endpoints with nmap.

nmap sU -p 1900 --script=upnp-info 192.168.0.0/24
Starting Nmap 7.80 ( https://nmap.org ) at 2021-06-03 13:11 UTC
Nmap scan report for mymodem.modem (192.168.0.1)
Host is up (0.0045s latency).

PORT     STATE SERVICE
1900/udp open  upnp
| upnp-info:
| 192.168.0.1
|     Server: Homeware UPnP/1.1
|_    Location: http://192.168.0.1:5000/rootDesc.xml
MAC Address: D4:35:1D:14:F3:FE (Technicolor)

The endpoint enables programmatic interaction between client and server. This coincides with another port exposed in our manifest.

ports:
- containerPort: 8200
  hostPort: 8200
  protocol: TCP

Enabling the SSDP interaction on Kubernetes required the DLNA server pod to be run with hostNetwork.

hostNetwork: true

Otherwise, you can expect the following issues.

To avoid node port conflicts the deployment spec will needs to use a Recreate strategy.

replicas: 1
strategy:
  type: Recreate