DHCP Discovery testing and implementation

Development
1

Hi :wave:!

Can someone help me figuring out how DHCP discovery works?

On my dev environment it doesn’t seem to work. Its a macOS venv installation and I get [homeassistant.components.dhcp] Cannot watch for dhcp packets without root or CAP_NET_RAW: Can't attach the BPF filter ! when I start HA.
I’ve tried it on a Windows machine running WSL too - with the same error.
I’ve even tried to run a Dev-Container, but I don’t quite know what I’m doing there and it seems it doesn’t get any DHCP requests forwarded.

How can I test this?

About the implementation: I've added the OUI to the manifest and ran `script.hassfest` so it is added to generated/dhcp and added `async def async_step_dhcp()` to my config_flow.py. 
    async def async_step_dhcp(self, discovery_info: DhcpServiceInfo) -> FlowResult:
        """Handle a flow initiated by the DHCP client."""
        discovery_input = {CONF_HOST: discovery_info.ip}
        self._async_abort_entries_match(discovery_input)
        return await self.async_step_user(user_input=discovery_input)

Can I just use DhcpServiceInfo data and forward it to self.async_step_user() - this would create the config_entry - or do I need to add some kind of confirmation step (I’ve seen this on couple of integrations code)?

Regards, Farmio

2

It basically sniff the network for DHCP packets, which requires elevated (root) privileges.

3

Thank you for your reply.
I know what it does, or is supposed to do, but I can’t get it running on my systems.
On WSL I tried sudo setcap cap_net_raw+ep /usr/bin/python3 Does remove the log message in startup, but still nothing gets discovered.
I’ve yet to try this on macOS.

Can I somehow run Hass as root? Sounds kind of wrong to me…

4

I doubt it will work on WSL.
CAP_NET_RAW is a privilege given to a docker container.

5

There is no Docker involved in my setups.
I tried to run sudo hass on macOS now, but it still gives me
[homeassistant.components.dhcp] Cannot watch for dhcp packets: Can't attach the BPF filter ! :confused:

6

So on macOS using an ubuntu aarch64 VM and installing HA there (using sudo setcap 'cap_net_raw+ep' /usr/bin/python3.8) works and I can test DHCP discovery now :tada: