Netfilter redirect does not work with wireguard

[Ivan Labáth]

Hello,

have you checked the source port of replies, or whether
there are any replies?

# tcpdump -nn

Tcpdump should show pre-NAT addresses on incoming packets
and AFAIK post-NAT on outgoing packets, i.e. what goes on
the wire.

You might need to apply SNAT on outgoing packets, which
might happen automatically with TCP connection tracking,
but I wouldn't really expect it on connection-less UDP.

Regards,
Ivan

On Thu, Nov 07, 2019 at 05:38:42PM +0100, Nico Schottelius wrote:
> 
> Hello,
> 
> I am experimenting with nft / netfilter redirects to support wireguard
> packets on *any* udp port. I tried using the following configuration for
> nftables:
> 
> [17:34:14] vpn-2a0ae5c1:~# cat /etc/nftables.conf
> #!/usr/sbin/nft -f
> 
> flush ruleset
> 
> table ip nat {
> 	chain prerouting {
> 		type nat hook prerouting priority 0;
> 
> 		# SSH works
> 		tcp dport != 22 redirect to 22
> 
> 		# wireguard doesn't
> 		udp dport != 51820 redirect to 51820
> 	}
> 
> 	chain postrouting {
> 		type nat hook postrouting priority 0;
> 	}
> }
> 
> However as you can see in the comments, this does not work with
> wireguard, however it does work with SSH.
> 
> I can see that wireguard is kernel space, and ssh user space, but does
> that cause the netfilter part to be skipped or am I doing some silly
> mistake here?
> 
> Best regards,
> 
> Nico
> 
> 
> --
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