anyone can tell me what`r these ?

[ArioS]

I got it few time ago and it down all of my wireless networking. is it DoS ? 
what can of dos ? i`m using linux as router.. any chance to block it ?

Iptraf :

Non-IP (0x4) (1500 bytes) from ffffffff0000 to ffffffffffff on eth0
Non-IP (0x4) (1500 bytes) from ffffffff0000 to ffffffffffff on eth0
Non-IP (0x4) (1500 bytes) from ffffffff0000 to ffffffffffff on eth0
Non-IP (0x4) (1500 bytes) from ffffffff0000 to ffffffffffff on eth0

TcpDump :

15:11:19.765769 ff:ff:ff:ff:00:00 > Broadcast null I (s=0,r=0,C) len=42
15:11:19.766271 ff:ff:ff:ff:00:00 > Broadcast null I (s=0,r=0,C) len=42
15:11:19.767359 ff:ff:ff:ff:00:00 > Broadcast null I (s=0,r=0,C) len=42
15:11:19.770860 ff:ff:ff:ff:00:00 > Broadcast null I (s=0,r=0,C) len=42