Hi, looks like the issue still persists, but I have a temporary solution in case if your upload speed drops *way* beyond yours (2 Mbps for me). You can force-use a 100 Mbps link speed. `iperf3` results below. Literally 50x speed increase in my case!
I've performed these benchmarks connecting to my VPS via wireguard:
```
$ cat /dev/mtd/by-name/U-Boot | strings | grep -B1 "u-boot,version"`
U-Boot: 2026.01_armbian-2026.01-S127a-Pc2e6-H706e-Vab81-B2eb2-R448a
```
Linux 6.18.10-current-rockchip64
Standard operation (1000 Mbps):
```root@odroidm1 ~# ethtool -s eth0 speed 1000 duplex full
root@odroidm1 ~# iperf3 -c 10.0.3.1
Connecting to host 10.0.3.1, port 5201
[ 5] local 10.0.3.2 port 42538 connected to 10.0.3.1 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 384 KBytes 3.14 Mbits/sec 5 14.7 KBytes
[ 5] 1.00-2.00 sec 384 KBytes 3.15 Mbits/sec 5 6.68 KBytes
[ 5] 2.00-3.00 sec 384 KBytes 3.14 Mbits/sec 2 13.4 KBytes
[ 5] 3.00-4.00 sec 256 KBytes 2.10 Mbits/sec 6 9.35 KBytes
[ 5] 4.00-4.43 sec 128 KBytes 2.42 Mbits/sec 0 22.7 KBytes
```
Dirty fix, link capped at 100 Mbps at most:
```
root@odroidm1 ~# ethtool -s eth0 speed 100 duplex full
root@odroidm1 ~# iperf3 -c 10.0.3.1
Connecting to host 10.0.3.1, port 5201
[ 5] local 10.0.3.2 port 42354 connected to 10.0.3.1 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 11.4 MBytes 95.3 Mbits/sec 0 1.03 MBytes
[ 5] 1.00-2.00 sec 10.5 MBytes 88.1 Mbits/sec 0 1.03 MBytes
[ 5] 2.00-3.00 sec 11.4 MBytes 95.4 Mbits/sec 0 1.10 MBytes
[ 5] 3.00-4.00 sec 10.2 MBytes 86.0 Mbits/sec 0 1.10 MBytes
[ 5] 4.00-4.48 sec 5.00 MBytes 87.4 Mbits/sec 0 1.10 MBytes
```
So.. yeah. While using Wireshark I also saw *a lot* of TCP retransmissions too, which usually don't happen that at 100 Mbps link in my configuration.
