e1000 driver for Intel's Gigabit cards claims support for TCP checksum
calculation offload on both receive and transmit side. It is possible
to verify that claim with the sendfile() syscall on the transmit side.
However, sendfile() can not read from a socket.
Is there a way to benefit from TCP checksum offloading on the receive
side in 2.4.x or 2.5.x kernel?