Re: Systems-resolved: Calling gethostbyaddr on non-local/non-private causes connection attempt

Hi Cristian,

I had to look up nss-resolve and indeed both LLMNR and system-resolved are mentioned in the description. In my test VM, `apt-cache policy` is showing that libnss-resolve package is installed.

I removed it using `apt purge libnss-resolve` and checked journalctl logs again while re-running the python script and I continue to see outbound connections on port 5355 are being logging.

I restarted the VM (to ensure the plugin was no longer loaded) and re-ran the nftables rule and python script but I continue to see the outbound connections with each invocation of gethostbyaddr.

Let me know what else I can investigate, this is new territory for me.

Thanks,

Anthony

From: Cristian Rodríguez <crrodriguez@xxxxxxxxxxxx>
Date: Thursday, February 22, 2024 at 4:48 PM
To: Anthony Fuller (TR-NA) <Anthony_Fuller@xxxxxxxxxxxxxx>
Cc: systemd-devel@xxxxxxxxxxxxxxxxxxxxx <systemd-devel@xxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [systemd-devel] Systems-resolved: Calling gethostbyaddr on non-local/non-private causes connection attempt

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On Thu, Feb 22, 2024 at 2:09 PM Anthony_Fuller@xxxxxxxxxxxxxx
<Anthony_Fuller@xxxxxxxxxxxxxx> wrote:

>
> Port 5355 is used for LLMNR and RFC-4795 [4], states in the abstract that “LLMNR only operates on the local link” so I think the current behavior of contacting hosts on port 5355 is incorrect, especially if that host IP is not link-local and not in the private IP range.

I cannot reproduce your issue.. are you using the nss module "resolve" peraphs ?

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