Packets are not arrived at tunnel setup by libgtpnl

congnt congnt at viosoft.com
Thu Nov 23 11:02:13 UTC 2017


Hi guys,

I'm using libgtpnl tools (gtp-link, gtp-tunnel) to setup a tunnel in my 
local
machines. I was able to setup gtp link to 2152 port as well as gtp tunnel.
I have pre-recorded GTP packets with correct teid and IP address as well
as chksum and port to send to 2152. However I can not see any packets
in gtp link device when using tcpdump.

By add some messages in gtp module, I notice that the function
gtp1u_udp_encap_recv in gtp.c kernel file was never been called if I send
packet with GTP headers. However, that function is called if I send normal
UDP packet without GTP header.

Note that I'm using Ubuntu 14.04 with kernel 4.8.0 lowlatency, the tunnel
is on a VM created by Virtualbox using virtio network driver. Any 
suggestions
on how to debug/solve this problem?

Many thanks in advances.
Best regards
Cong.


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