rtl8169_tx_interrupt() in Realtek's driver is _very_ wrong. It may take some time
for you to notice but the symptoms will be pretty clear
If you can reproduce the issue with a recent 2.4.x kernel without any binary only
module loaded, I'll at least update the backport of the r8169 driver. OTOH, I have
no interest trying to fix bugs in the r8169 driver while some piece of code does
interesting things in the background.