How do you send an Ethernet frame with a corrupt FCS?

Question

I'm not sure if this is even possible since this might be handled in hardware, but I need to send some Ethernet frames with errors in them. I'd like to be able to create runts, jabber, misalignment, and bad FCS errors. I'm working in Python.

Answer 1

It can be handled in hardware, but isn't always -- and even if it is, you can turn that off; see the ethtool offload parameters.

With regard to getting full control over the frames you create -- look into PF_PACKET (for one approach) or the tap driver (for another).

Here's an article on using PF_PACKET to send hand-crafted frames from Python.