Ethernet Frames
Ethernet frames in TEMU are structs containing a flag field, data and an optional preamble.
The data field is a COW buffer which contains the level 2 ethernet frame data.
The preamble will typically be ignored and not set for most MACs.
However if it is set to somthing non-standard,
a device can indicate this by setting the flag TEMU_ETH_NON_STANDARD_PREAMBLE
.