fxp damages dmesg?

[Sergei Vyshenski]

Motherboard ASUS CUSL2-C with 815EP chipset and 
two Intel 82559 Pro/100 Ethernet cards
exibits the following.

dmesg reports usual text only a few seconds after reboot.
Later it displays a single line with a fragment of ipfw log, e.g.

167 213.131.11.152 in via fxp0

which seems to change with each new activity of ipfw.
Files /var/log/dmesg.today and /var/log/dmesg.yesterday
rotate daily as usual and contain similar single line.
The file /var/run/dmesg.boot still has usual text of dmesg.

This started not long before 4.9-PRERELEASE
No crushes at any CPU or network load, and no sane error messages.