Decimal Offset	Description
-14:	DST MAC, 6 bytes
-8:	SRC MAC, 6 bytes
-2:	Eth PROTO, 2 bytes, eg. ETH_P_IP
0:	Protocol header (IP Header)

From an email on the LARTC list :

Egress (match Dst MAC):
... match u16 0xPPPP 0xFFFF at -2 match u32 0xM2M3M4M5 0xFFFFFFFF at -12 match u16 0xM0M1 0xFFFF at -14

Ingress (match Src MAC):
... match u16 0xPPPP 0xFFFF at -2 match u16 0xM4M5 0xFFFF at -4 match u32 0xM0M1M2M3 0xFFFFFFFF at -8

Where PPPP is the Eth Proto Code (from linux/include/linux/if_ether.h):

0800    ETH_P_IP

and M0..M5 are the 6 bytes of the MAC address

Example for matching ETH_P_IP for MAC 00:11:22:33:44:55

Egress:
... match u16 0x0800 0xFFFF at -2 match u32 0x22334455 0xFFFFFFFF at -12 match u16 0x0011 0xFFFF at -14

Ingress:
... match u16 0x0800 0xFFFF at -2 match u16 0x4455 0xFFFF at -4 match u32 0x00112233 0xFFFFFFFF at -8



stef.coene@docum.org