Rpi4 loses network connectivity via eth0 after kernel update to 6.18.24

[antoniosk]

Describe the bug

On Raspberry Pi OS Trixie, after the yesteday (13/5/2026) kernel update to 6.18.29, when Firefox or Chromium is launched, the eth0 connection dies.
Nether unplugging the cable nor restarting the systemd-networkd.service works. Ping works only for the assigned IPv4 address to eth0.
No errors are reported to syslog/kernel.log.
The wlan0 is not connected to a wireless network.
The eth0 gets its's IPv4 address from isc-dhcpd running on an Rpi2B, acting also as a gateway. There are no issues with other machines on the network.

Steps to reproduce the behaviour

Launch a browser (Firefox/Chromium).

Device (s)

Raspberry Pi 4 Mod. B

System

cat /etc/rpi-issue
Raspberry Pi reference 2025-10-01
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 7dadcf1fc5ce1648ab09409ab978831690c9a955, stage5

vcgencmd version
May 8 2026 18:13:05
Copyright (c) 2012 Broadcom
version ae9a8ea9f3ca745de6f357bd7fc8307721ad38b7 (clean) (release) (start)

uname -a
Linux raspberrypi4 6.18.29+rpt-rpi-v8 #1 SMP PREEMPT Debian 1:6.18.29-1+rpt1 (2026-05-12) aarch64 GNU/Linux

Logs

No response

Additional context

No response

[JustArchi]

This is a serious issue and it doesn't consider only web browser. I have fully headless (raspberry pi os lite) version that only replicates my postgresql database, and after 6.12.75+rpt-rpi-v8 -> 6.18.29+rpt-rpi-v8 kernel upgrade it has VERY unstable network connection shortly after boot, even though the activity there is minimal, within 50 mbps or less.

Please investigate, I've downgraded to 6.12 for now. I've double-verified that other machines have no issues, and triple-verified that 6.18 gives issues, rebooting to 6.12 fixes them, and rebooting back to 6.18 brings the issues back.

Raspberry Pi 4 Model B Rev 1.4

BOOTLOADER: up to date
   CURRENT: Tue 14 Apr 21:17:01 UTC 2026 (1776201421)

     VL805: up to date
   CURRENT: 000138c0

It's very hard for me to believe that this wasn't caught earlier, as it's a serious regression observable right away on any network-connected system. Should be easy to reproduce - I can't even download bigger file without network dropping in the middle of it.

wget -O /dev/null https://proof.ovh.net/files/10Gb.dat

[spockfish]

Could this be related to #7304 ?

[antoniosk]

After further investigation, this is not browser related. The issue appears after network activity other than a simple ping via eth0. The workarounds are (1) to downgrade to the old kernel, or (2) to disconnect eth0 and use wlan instead.