iperf3: segfault on x86_64

Maintainer: @nbd168
Environment: x86_64, Hewlett-Packard HP EliteDesk 800 G1 USDT, OpenWrt GCC 12.3.0 r23899+10-3001d3c5d4
This was an OpenWrt fork: Gluon v2023.2.3
Which runs:

OPENWRT_REPO=https://github.com/openwrt/openwrt.git
OPENWRT_BRANCH=openwrt-23.05
OPENWRT_COMMIT=3001d3c5d446bf53fc222640d49a4cc79e04a2f3

Description:
I just noticed this segfault in dmesg after running a couple of iperf3 commands (I'm not sure which one triggered it or if it could've been triggered by a STRG+C by accident)

[459397.930023] iperf3[4064]: segfault at 28 ip 00007ff50794da40 sp 00007ffe5a472880 error 4 in libc.so[7ff507928000+4c000] [459397.930195] Code: 41 5d 41 5e c3 48 8d 35 2e f2 03 00 e9 a1 ff ff ff 90 83 c8 ff c3 83 c8 ff c3 83 c8 ff c3 41 54 55 bd 01 00 00 00 53 48 89 fb <48> 8b 43 28 48 85 c0 74 08 48 ff c5 48 89 c3 eb ef 48 0f bf 43 50 

No source files, tests, or exact triggering command are named. Start by reproducing the segfault on the stated x86_64 OpenWrt/Gluon environment using the available iperf3 commands, then narrow down whether interruption or a specific command triggers it; done means the trigger and cause are identified and the crash is prevented.