asus Merlin & openvpn & tunnelblink / ubuntu openvpn client = no IP configuration from DHCP

[wally_tm]

Hi,

This question is predominantly for @RMerlin :
On two separate routers I'm running the latests version of merlin asus firmware and for some time now I (and my colleagues) can perfectly connect with windows machines but nobody can connect with linux / macOS machine. We use openvpn client and tunnelblink respectively. I would like to point out that roughly 2 years ago it was working more or less OK.

I will attach a tunnel blink verbose output:

 

[RMerlin]

See this FAQ from tunnelblick regarding your error message:

https://tunnelblick.net/cKnown.html

 

[wally_tm]

Hi @RMerlin and thanks for fast reply,

Yes we followed that FAQ, also all possible configuration options for openvpn / tunnelblink client. Only way that darn thing connect is when IP configuration is provided via configuration file option "ifconfig x.x.x.x". WE were trying to get configuration for emerging DHCP server to look how the addresses are passed down the channel but so far it seems like ip is configured only through --win32-ip option that other systems to windows simply don't understand.

Also, please consider that people that attempt to get this thing working have background in software engineering going back to system V ... not saying that we know it all but we try to attempt all obvious solutions first like faq's and (rt)fm

 

[RMerlin]

I pointed you at the FAQ because a Google search for your specific error message pointed me to it, which implied it was a known issue with tunnelblick.

 

[wally_tm]

I know and for that thanks.

Anyway don't you happen to know how the IP allocation is done for setup with TAP interface on your flavour of firmware ? I was trying to trace the dhcp server configuration but was unable to do it on the quick ... I can find it out, but I'm not in the mood for hours of reverse engineering firmware if I can simply ask.

Also don't you happen to know whenever the build options for open vpn when you compile the firmware does include anything in regards of how it's pushing out the IP configuration to clients ? As I said before (actually my mate pointed it out) we se some mentioning of --win32-ip which could point out to openvpn server hijacking dhcp lease messages and is manually pumping it out at as --win32-ip option for silly windows machines that can't perform a proper dhcp lookup over vpn tunnel.

 

[RMerlin]

No idea, I've never looked at TAP mode, so I'm not familiar with how IPs are being handed to the remote client (I assume that other devices beyond the OpenVPN clients are relying on DHCP, assuming broadcasts are properly sent accross the TAP tunnel). You'd have to dig through OpenVPN's documentation to figure out how TAP mode works, sorry.