Ethernet (Raw)

[gregory.menke at gsfc.nasa.gov]

Joel Sherrill writes:
 > 
 > 
 > gregory.menke at gsfc.nasa.gov wrote:
 > > 
 > > Erwin Rol writes:
 > >  > On Tue, 2003-03-25 at 18:12, Joel Sherrill wrote:
 > >  >
 > >  > > Look for tap in the networking guide and see if that helps.  I don't
 > >  > > know if it is far enough into the stack to help.
 > >  >
 > >  > The TAP interface is only the receiving part ( right ? ). I hacked up
 > >  > something like that for RTEMS 4.0 too, the problem was sending raw (or
 > >  > almost raw , IPX) frames.
 > >  >
 > > 
 > > Its right above the driver itself- its a raw ethernet frame.
 > > Depending on the if_tap function's return value, the packet is either
 > > passed to the tcp/ip stack or discarded.
 > 
 > Does the standard FreeBSD stack have a facility like this that was
 > not enabled/ported?
 > 
 > If not, then can the tap design/interface be used as a model to
 > provide the write side?

I don't know to both questions.  if_tap operates at the very bottom
layer of the ip stack, just after the driver submits the ethernet
frame to it.  The sending side looks fairly involved with a
per-interface send queue.  I would be suprised if there wasn't a hook
in there someplace.  Do you know if SOCK_RAW is supported by the
stack?

Gregm