'Invalid extension header length or else' when running end to end test with QER

[aviweit]

Hi,

I have properly installed gtp5g and libgtp5gnl on my Ubuntu 20.04 server and successfully invoked the test script script/ns_ran_upf.sh.

I then went ahead and added QER usage to the script, invoked ./cleanup.sh and run the script again. Ping failed.
I then noticed

gtp5gtest:[gtp5g] gtp1u_udp_encap_recv: Invalid extension header length or else

being reported in /var/log/syslog. I would like to ask whether I did something wrong or perhaps QER support is not fully implemented yet?

Please find below more details:

under "RAN part":

sudo ./gtp5g-tunnel add qer gtp5gtest 1 --qfi 9
sudo ./gtp5g-tunnel add qer gtp5gtest 2 --qfi 9
...
sudo ./gtp5g-tunnel add pdr gtp5gtest 1 --pcd 1 --hdr-rm 0 --ue-ipv4 ${UE_IP} --f-teid 87 ${RAN_IP} --far-id 1 --qer-id 1
sudo ./gtp5g-tunnel add pdr gtp5gtest 2 --pcd 2 --ue-ipv4 ${UE_IP} --far-id 2 --qer-id 2

under "UPF part":

${EXEC_NS2} ./gtp5g-tunnel add qer gtp5gtest 1 --qfi 9
${EXEC_NS2} ./gtp5g-tunnel add qer gtp5gtest 2 --qfi 9
...
${EXEC_NS2} ./gtp5g-tunnel add pdr gtp5gtest 1 --pcd 1 --hdr-rm 0 --ue-ipv4 ${UE_IP} --f-teid 78 ${UPF_IP} --far-id 1 --qer-id 1
${EXEC_NS2} ./gtp5g-tunnel add pdr gtp5gtest 2 --pcd 2 --ue-ipv4 ${UE_IP} --far-id 2 --qer-id 2

I am using master version for both.

Thanks.

[muthuramanecs03g]

Hi @aviweit,

For your information, in gtp5g, we handled the GTP-U extension header and verified with QER but there is no implementation about QoS.

Could you please provide the dmesg log and packet capture?

[aviweit]

Hi @muthuramanecs03g ,

Please find attached dmesg. I would just like to comment that I have added a printing of:

printk_ratelimited("PDU_SESSION_INFO_TYPE0"); in which it got printed in syslog.

I added that print right before return -1; at line https://github.com/PrinzOwO/gtp5g/blob/master/gtp5g.c#L2046
and rebuilt, reloaded the module.

[16049.428457] IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
[16049.428485] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
[16049.466155] gtp5g: enable gtp5g on 3, 5
[16049.470680] gtp5gtest:[gtp5g] gtp5g_newlink: registered new 5G GTP interface
[16049.567788] gtp5gtest:[gtp5g] gtp5g_gnl_add_qer: QER-Add: QER_ID(1) success
[16049.586265] gtp5gtest:[gtp5g] gtp5g_gnl_add_qer: QER-Add: QER_ID(2) success
[16049.604491] gtp5gtest:[gtp5g] gtp5g_gnl_add_far: FAR-Add: id[1] success
[16049.622599] gtp5gtest:[gtp5g] gtp5g_gnl_add_far: FAR-Add: id[2] success
[16049.642004] gtp5gtest:[gtp5g] gtp5g_gnl_add_pdr: PDR-Add: id[1] success
[16049.660085] gtp5gtest:[gtp5g] gtp5g_gnl_add_pdr: PDR-Add: id[2] success
[16049.687305] gtp5g: enable gtp5g on 3, 5
[16049.692959] gtp5gtest:[gtp5g] gtp5g_newlink: registered new 5G GTP interface
[16049.789026] gtp5gtest:[gtp5g] gtp5g_gnl_add_qer: QER-Add: QER_ID(1) success
[16049.809679] gtp5gtest:[gtp5g] gtp5g_gnl_add_qer: QER-Add: QER_ID(2) success
[16049.830879] gtp5gtest:[gtp5g] gtp5g_gnl_add_far: FAR-Add: id[1] success
[16049.850497] gtp5gtest:[gtp5g] gtp5g_gnl_add_far: FAR-Add: id[2] success
[16049.870825] gtp5gtest:[gtp5g] gtp5g_gnl_add_pdr: PDR-Add: id[1] success
[16049.890531] gtp5gtest:[gtp5g] gtp5g_gnl_add_pdr: PDR-Add: id[2] success
[16049.901035] get_gtpu_header_len: GTPV1_NEXT_EXT_HDR_TYPE_85
[16049.901036] PDU_SESSION_INFO_TYPE0
[16049.901037] gtp5gtest:[gtp5g] gtp1u_udp_encap_recv: Invalid extension header length or else
[16049.901038] gtp5gtest:[gtp5g] gtp5g_encap_recv: GTP packet has been dropped
[16050.904743] get_gtpu_header_len: GTPV1_NEXT_EXT_HDR_TYPE_85
[16050.904746] PDU_SESSION_INFO_TYPE0
[16050.904748] gtp5gtest:[gtp5g] gtp1u_udp_encap_recv: Invalid extension header length or else
[16050.904749] gtp5gtest:[gtp5g] gtp5g_encap_recv: GTP packet has been dropped
[16051.928751] get_gtpu_header_len: GTPV1_NEXT_EXT_HDR_TYPE_85
[16051.928753] PDU_SESSION_INFO_TYPE0
[16051.928754] gtp5gtest:[gtp5g] gtp1u_udp_encap_recv: Invalid extension header length or else
[16051.928755] gtp5gtest:[gtp5g] gtp5g_encap_recv: GTP packet has been dropped
[16052.952757] get_gtpu_header_len: GTPV1_NEXT_EXT_HDR_TYPE_85
[16052.952759] PDU_SESSION_INFO_TYPE0
[16052.952761] gtp5gtest:[gtp5g] gtp1u_udp_encap_recv: Invalid extension header length or else
[16052.952761] gtp5gtest:[gtp5g] gtp5g_encap_recv: GTP packet has been dropped
[16053.976826] get_gtpu_header_len: GTPV1_NEXT_EXT_HDR_TYPE_85
[16053.976828] PDU_SESSION_INFO_TYPE0
[16053.976830] gtp5gtest:[gtp5g] gtp1u_udp_encap_recv: Invalid extension header length or else
[16053.976830] gtp5gtest:[gtp5g] gtp5g_encap_recv: GTP packet has been dropped
[16066.020835] gtp5gtest:[gtp5g] gtp5g_dellink: deregistered 5G GTP interface

[aviweit]

Our intention was to create a tunnel with QoS enforcement and verify this with iperf.

For example, to create it with the following switches:

./gtp5g-tunnel add qer gtp5gtest 123 --qfi 9 --mbr-uhigh 200000 --mbr-ulow 200000 --mbr-dhigh 100000 --mbr-dlow 100000
and then to add this qer to the pdr.

Do you have plans to implement it?

Thanks again.

[muthuramanecs03g]

Hi @aviweit,

Looks you added some more debug prints to trace this issue

[16051.928755] gtp5gtest:[gtp5g] gtp5g_encap_recv: GTP packet has been dropped

[16052.952757] get_gtpu_header_len: GTPV1_NEXT_EXT_HDR_TYPE_85
[16052.952759] PDU_SESSION_INFO_TYPE0

In get_gtpu_header_len(), we didn't expect the TYPE0 ("DL PDU Session Information) in uplink.

Please, check the more information on the below documents

1. 3GPP TS 29.281 V15.3.0 (2018-06), Section 5.2.2.7 PDU Session Container
2. 3GPP TS 38.415 V15.2.0 (2018-12), Section 5.5.2 Frame format for the PDU Session user plane protocol

Do you have plans to implement it?
Yes, we have a plan to implement rfc2698 (Two Rate Three Color like in P4) may be the end of June 2021.

[aviweit]

Hi @muthuramanecs03g ,

Thanks for the input. I would like to ask whether there are differences between the GTP-U mainline kernel module and this gtp5g implementation? I am asking because I have noticed that free5gc UPF is based on this module and was wondering why it does not use the GTP-U mainline one.

Thanks.

[muthuramanecs03g]

Hi @aviweit,

Linux mainline GTP kernel module didn't fulfill the requirements of 5G such as Downlink Data Buffering, QoS, and other requirements. In gtp5g, implemented Match+Action based on PDR, FAR, and QER.

That's why implemented it as a separate module, and also we have a plan to merge with the Linux kernel once gtp5g got tested with Landslide.

[muthuramanecs03g]

Hi @aviweit,

One more thing, I would like to update you, this repo is part of the free5GC project. Now, this repo forked into free5GC and maintain it there only.

https://github.com/free5gc/gtp5g

[aviweit]

@muthuramanecs03g ,
Thanks a lot for the updates.