XFRM input/output

  Today I'll show you the input/output procedure of XFRM.

Output procedure
  Go through the code:
+xfrm4_output->
 +xfrm4_output_finish->
  -xfrm4_output_finish2
  In xfrm4_output_finish2, it applies a sa(take AH for example) by '.mode->output' and '.type->output'. Finally, it calls dst_output again and pass down the packet protected to the 'neighbour subsystem'.

Input procedure
  Go through the code:
 +xfrm4_rcv->
  +xfrm4_rcv_encap->