[Pi 4B 8GB] When EEE (Energy Efficient Ethernet) is enable and active on eth0 at gigabit speed, ethernet becomes slow to unresponsive with packets dropping

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
linux
Domain
networking, operating-systems

Research direction

Start by reproducing the eth0 behavior on a Pi 4B at gigabit speed with EEE enabled, using the reported ethtool --show-eee eth0 status and the supplied network setup. Compare packet loss and responsiveness with EEE enabled and after running ethtool --set-eee eth0 eee off; done means gigabit Ethernet remains responsive without packet drops while EEE is active.

Written by the indexing model from the issue text.

Description

Summary
When Energy Efficient Ethernet is enabled and active from a new install of Raspberry Pi OS on a Pi 4B 8GB, gigabit ethernet transfer with the built-in ethernet adapter becomes slow and unresponsive with packets being dropped. Other computers supporting EEE plugged into the same network behave normally, even if they are tested in the same port that the Pi was connected. When the Pi is connected with EEE enabled, it also results in some odd behaviour on other devices connected to the same switch such as causing the other device to drop packets and/or reconnect constantly. Removing the Pi from the network causes the behaviour on the switch and other device to return to normal.

To reproduce
When Pi 4B 8GB is connected to gigabit switch with default EEE behaviours, the network performance of the Pi deteriorates as above.

Status from ethtool --show-eee eth0:

EEE Settings for eth0:
EEE status: enabled - active
Tx LPI: inactive
Supported EEE link modes: 100baseT/Full
1000baseT/Full
Advertised EEE link modes: 100baseT/Full
1000baseT/Full
Link partner advertised EEE link modes: 100baseT/Full
1000baseT/Full

Temporary fix
As soon as EEE is disabled with 'ethtool --set-eee eth0 eee off', ethernet performance returns to normal at gigabit speeds.

Logs
I am unsure which logs would be necessary to help diagnose the problem... please let me know and I will be happy to add them!

Equipment in use: Home network with BT Business Hub in use as modem and switch + Powerline ethernet with built in switch (BT Mini Connector)

A relevant forum thread: https://www.raspberrypi.org/forums/viewtopic.php?t=305820

Dominant language
C
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Avg merge
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Merged PRs (30d)
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