Support OSX nonstandard Ethernet link layer header.

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Ostinato currently supports only Ethernet as a link layer. OSX doesn't use a 
standard Ethernet link layer header for the loopback interface, but instead 
uses a 4 byte 'type' field.

What steps will reproduce the problem?
1. Use Ostinato to send traffic out the loopback interface on OSX
2. tcpdump the traffic - tcpdump does not interpret the packet correctly.
3.

What is the expected output? What do you see instead?

Packets appear to have the first four bytes truncated.

What version and revision of the product are you using (available in the
About dialog)? On what operating system?

Ostinato rev 0.5, OSX 10.7.4

Please provide any additional information below.

Noted here:  https://groups.google.com/d/msg/ostinato/ktboY8G3EE8/znJHcDpQh2QJ

Original issue reported on code.google.com by jamg...@gmail.com on 16 Jul 2012 at 6:18

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Original comment by pstav...@gmail.com on 17 Jul 2012 at 4:31

• Changed state: Accepted

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Hi 

I am experiencing the same issue, my loopback interface is busy with RPCAP 
Error packets and subsequent TCP (ACK >> PSH,ACK >> ACK) 
is there any way to solve this?

Original comment by osamah.i...@gmail.com on 26 Sep 2012 at 10:01

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@osamah - you are not experiencing this issue. The packets shown as RPCAP Error 
packets on the loopback interface are most likely valid packets that Wireshark 
is not able to decode correctly

Original comment by pstav...@gmail.com on 27 Sep 2012 at 1:32