Hi,

there is this annoying problem with the way wg-quick sets up the routing, that 
when you unplug the Ethernet cable the routing rule (see ip rule) that checks 
the fwmark gets lost. So let's say you move to another location with your 
laptop and plug in an Ethernet cable again, it essentially disables your VPN. 
You're lucky if you have the popular kill switch in place blocking all your 
traffic instead of silently disabling your VPN.

PostUp = iptables -I OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m 
addrtype ! --dst-type LOCAL -j REJECT
PreDown = iptables -D OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m 
addrtype ! --dst-type LOCAL -j REJECT

I have no idea why the rule gets lost. It might be the kernel removing it for 
whatever reason. But it makes no sense to me because I don't see how the kernel 
would make a connection between that rule and the Ethernet link that goes down. 
Any ideas on the issue? Is this a known problem? Are there workarounds?

Greetings,
Tim

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