[BUG] Hop is added when using XDP with pcn-iptables

[Hanarion]

Describe the bug

Hello, When i init pcn-iptables with XDP, i can see that in my traceroute a unknown hop is added, shown as * * * *

To Reproduce

Steps to reproduce the behavior:

1. pcn-iptables-init-xdp
2. Traceroute to IP of server
3. See that there is a hop added even in LAN

Expected behavior

I was thinking that XDP would be transparent, because of this hop, the server is unable to talk with some of my device wich force TTL to 1 (like for BGP) Is there a way to get rid of this hop ? When using classic pcn-iptables-init this hop isn't here, but i need XDP as it is a 2x100G link

Please tell us about your environment:

1. OS details: Debian 11
2. Kernel details: Linux filter1 5.10.0-9-amd64 # 1 SMP Debian 5.10.70-1 (2021-09-30) x86_64 GNU/Linux
3. Polycube Version: polycubectl: version: v0.9.0+ [git: (branch/commit): master/97156de0] polycubed: version: v0.9.0+ [git: (branch/commit): master/97156de0]
4. Polycube Log: Not relevant for the issue i think

Additionnal informations :

Host                             Loss%   Snt   Last   Avg  Best  Wrst StDev
 1. ???
 2. 2xxxxxxxxxxxxxxxx   0.0%    36    0.3   0.3   0.2   0.6   0.1

traceroute to XXXXXXXXX , 30 hops max, 60 byte packets
 1  * * *
 2  * * xxxxxxxxxxxxx (1XXXXXXXXX)  0.139 ms