Buggy MTU with Wireguard (attached pcapng)

[Vasili Pupkin]

The TCP connection MSS is set to 1460 bytes and also Don't fragment flag 
is set. The server selects this MSS as a frame size on its side and 
packet is dropped, probably. If you are using linux router try to use 
this command "iptables -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j 
TCPMSS --clamp-mss-to-pmtu" or be careful to set MTU on all client 
machines adapters correctly.


On 10.01.2020 1:05, alpha_one_x86 wrote:
>
> Hi,
>
> I have wireguard interface "veth", and my real interface "eth0".
>
> No bug with openvpn, but with wireguard on IPv4 for https, I have bug, 
> see the attached file, the returned data is 3300byte, then Destination 
> unreachable (Fragmentation needed).
>
> Bug into wireguard? How fix this?
>
> The ok.pcapng it's same https download do with openvpn.
>
> Cheers,
>
>
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> WireGuard at lists.zx2c4.com
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