ZeroTier Connectivity Issues with CSF Firewall Despite Allowing All UDP Traffic

[RodGomes]

Hello,

I'm reporting a persistent issue I've been experiencing with ZeroTier connectivity when the CSF is active on my Linux system. Despite my attempts to configure the firewall to allow ZeroTier traffic, ZeroTier does not function as long as CSF is active.

Here's what I've done so far:

• I have allowed all UDP traffic in both UDP_IN and UDP_OUT sections of my CSF configuration.
  I have opened the UDP port 9993, which ZeroTier primarily uses, in both UDP_IN and UDP_OUT sections of my CSF configuration.

• Despite these steps, ZeroTier does not work when CSF is active. As soon as I disable CSF, ZeroTier starts working immediately. This issue persists even when all UDP traffic is allowed, suggesting that it's not merely a configuration problem.

Given that the issue is resolved when CSF is turned off, it seems likely that CSF is blocking some aspect of ZeroTier's traffic, even though all UDP traffic has been allowed.

I'm submitting this as a bug report because this behavior seems inconsistent with the intended functionality of CSF. I would appreciate any guidance on whether this is a known issue, if there are any workarounds, or if a fix is being considered for future CSF updates.

Thank you in advance for your assistance.