iperf3 binds to UE pod's default interface instead of uesimtunX when using nr-binder

[amrbaraka]

Hello,

Binding uesimtun interfaces for ping command works fine:
root@ueransim-ueee-5647db78d5-j9rct:/ueransim/build# ping -I uesimtun0 google.com
PING google.com (216.58.206.46) from 10.1.0.1 uesimtun0: 56(84) bytes of data.
64 bytes from lhr35s10-in-f14.1e100.net (216.58.206.46): icmp_seq=1 ttl=115 time=2.32 ms
64 bytes from lhr35s10-in-f14.1e100.net (216.58.206.46): icmp_seq=2 ttl=115 time=1.91 ms

I could also verify it via tcpdump on UPF n6 interface where icmp packets can be seen traversing.

However for iperf3, this is not Ok:

I've tried binding uesimtun via nr-binder:

root@ueransim-ue-5647db78d5-j9rct:/ueransim/build# ./nr-binder 10.1.0.1 iperf3 -b 1 k/s -c 192.168.180.151 -p 12345
Connecting to host 192.168.180.151, port 12345
[ 4] local 10.1.0.1 port 52671 connected to 192.168.180.151 port 12345
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-1.00 sec 1.38 MBytes 11.5 Mbits/sec 0 201 KBytes
[ 4] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec 0 201 KBytes

But no packet were traversing via UPF n6 interface.
Taking a tcpdump on ue pod, showed that packet are traversing via pod default interface and not uesimtun.

Same behavior when I tried binding via iperf3 command options:
root@ueransim-ue-5647db78d5-j9rct:/ueransim/build# iperf3 -B 10.1.0.1 -b 1 k/s -c 192.168.180.151 -p 12345
Connecting to host 192.168.180.151, port 12345
[ 4] local 10.1.0.1 port 38301 connected to 192.168.180.151 port 12345
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-1.00 sec 1.38 MBytes 11.5 Mbits/sec 0 154 KBytes
[ 4] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec 0 154 KBytes

Same behavior also when trying towards external iperf servers ping.online.net, iperf3.moji.fr

Any idea what could be the reason ?

I'm using UERANSIM v3.2.6 on AWS EKS,, installed iperf3 as a binary inside the ue container.

Thanks in advance.
Br,
Amr