multi-home difficulty

[Tomas Herceg]

+1 for binding only on specific IP

On 11/21/2017 02:21 PM, d tbsky wrote:
> Hi:
>    I tested wireguard and the speed is amazing. but when I try to
> deploy it to our real linux firewall, I found it is hard to make it
> work.
> 
>    our current linux firewall have multiple interface and multiple
> routing tables. local program will get lan ip address and nat to
> correct wan ip address when goto internet.
> 
>   since wireguard can not bind to specific ip address, it sometimes
> use wrong ip address to reply and the vpn communication can not be
> established.
> 
> for example:
> 
> config for client site: (assume wan ip is 2.2.2.2)
> interface: wg0
>   public key: ****
>   private key: (hidden)
>   listening port: 51820
> peer: ****
>   endpoint: 1.1.1.1:51820
>   allowed ips: 0.0.0.0/0
> 
> config for server site: (assume wan ip is 1.1.1.1)
> interface: wg0
>   public key: ****
>   private key: (hidden)
>   listening port: 51820
> peer: ****
>   allowed ips: 0.0.0.0/0
> 
> when client initial connect to server, at server site I saw  flow like below:
> "cat /proc/net/nf_conntrack | grep 51820"
> 
> ipv4     2 udp      17 23 src=172.18.1.254 dst=2.2.2.2 sport=51820
> dport=51820 packets=1 bytes=120 [UNREPLIED] src=2.2.2.2 dst=1.1.1.1
> sport=51820 dport=1085 packets=0 bytes=0 mark=1 zone=0 use=2
> ipv4     2 udp      17 23 src=2.2.2.2 dst=1.1.1.1 sport=51820
> dport=51820 packets=1 bytes=176 [UNREPLIED] src=1.1.1.1 dst=2.2.2.2
> sport=51820 dport=51820 packets=0 bytes=0 mark=1 zone=0 use=2
> 
> so at first client  2.2.2.2:51820 connect to server 1.1.1.1:51820
> but then server use 172.18.1.254(lan ip address) to reply and 51820
> port is nat to 1085 so the communication is broken.
> 
> if wireguard can bind to specific ip address then there will be no problem.
> or if wireguard can reply with the correct ip address.( eg: if client
> connect to wireguard ip 1.1.1.1, then wiregurad should reply via ip
> address 1.1.1.1) then maybe there will be no problem.
> 
> Regards,
> tbskyd
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> 

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