Hi,
Short story:
The VPP tunnel implementation HOWTO [1] says that a L3 tunnel needs an IP
address. How do I implement a P2P tunnel interface without assigning an IP
address to it?
Long story:
I'm implementing a GTP-U User Plane Node that conforms to 3GPP TS 29.244
[2] & [3]. For each Sx Session a VPP tunnel interface is created (a Sx
Session can consist of multiple GTP tunnels that all belong to the same UE
IP). A reverse route for the UE IP is inserted into the FIB pointing to the
session tunnel interface.
So far this all works nicely. However when a GTP-U packet arrives, a trace
shows that it is decapsulated, handed to ip4-input and the immediatly
dropped without any error indication:
00:00:59:474894: ip4-udp-lookup
UDP: src-port 2152 dst-port 2152
00:00:59:474902: gtpu4-input
GTPU decap from gtpu_session0 teid 1 next 1 error 0
00:00:59:474942: ip4-input
ICMP: 10.180.125.105 -> 8.8.8.8
tos 0x00, ttl 63, length 84, checksum 0xa484
fragment id 0xfef7, flags DONT_FRAGMENT
ICMP echo_request checksum 0xc7d
00:00:59:475013: ip4-drop
ICMP: 10.180.125.105 -> 8.8.8.8
tos 0x00, ttl 63, length 84, checksum 0xa484
fragment id 0xfef7, flags DONT_FRAGMENT
ICMP echo_request checksum 0xc7d
00:00:59:475020: error-drop
ip4-input: valid ip4 packets
I have traced the cause of the drop to vnet_feature_arc_start and from
there to vnet_get_config_data. It turns out the IP feature is not
configured on the ARC/sw_if_index combination.
When I manually add a IP address to the tunnel interface it starts to work.
I already looked at the PPPoE and the IPSec plugins, They must be doing
something simmilar, but I can't spot the difference.
So how do I get the tunnel interface to work without having to add an IP
address to it? Or, do I need to handle the input/decap chain differently?
My current code is at:
https://github.com/RoadRunnr/vpp/tree/feature/gtp-dp/src/plugins/gtpdp
Thanks
Andreas
1: https://wiki.fd.io/view/VPP/How_to_add_a_tunnel_encapsulation
2: https://github.com/RoadRunnr/vpp/tree/feature/gtp-dp
3:
http://www.etsi.org/deliver/etsi_ts/129200_129299/129244/14.01.00_60/ts_129244v140100p.pdf
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