Question about basic usage of GTP kernel module

Hi, I'm trying to build a simple node that would encap/decap between IP and GTP in the user plane. For this I have been using gtp-link and gtp-tunnel tools of the libgtpnl, but with no luck so far. Could anyone please review my setup and let me know what I'm doing wrong? Topology: node1 - DUT, I would like to be able to send a ping from this node such that it is encapsulated into GTP tunnel towards node2. 2 interfaces: - ens6 - represents interface towards MS, has address 20.1.1.1/24 - ens7 - represents interface towards GGSN, has address 10.1.1.1/24 node2 Just a single interface towards node1, address 10.1.1.2/24 Test: On node2, I'm following these steps: - creating a GTP device: # ./gtp-link add gtp-u - adding a GTP tunnel: # ./gtp-tunnel add gtp-u v1 20 10 20.1.1.1 10.1.1.2 # ./gtp-tunnel list version 1 tei 20/10 ms_addr 20.1.1.1 sgsn_addr 10.1.1.2 - adding a route to an address representing APN to use the GTP device: # ip route add 8.8.8.8 src 20.1.1.1 dev gtp-u - Trying to ping 8.8.8.8 Result: I was expecting to see ECMP packets to 8.8.8.8 to be sent out via ens7 towards node2 and encapsulated in GTP. However, I can only see that these packets appear on the gtp-u interface, but are not forwarded. Looking at interface stats on gtp-u, I can see that the ping hits "tx_error" counter. Is there anything I'm missing here? Are any parameters wrong? Or am I misunderstanding the function of the GTP-U kernel support entirely? Any help would be appreciated. Thanks, Michael