This is an experimental demonstration target which inverts the source
and destination fields in the IP header and retransmits the packet.
It is only valid in the
.BR INPUT ,
.B FORWARD
and
.B PREROUTING
chains, and user-defined chains which are only called from those
chains.  Note that the outgoing packets are
.B NOT
seen by any packet filtering chains, connection tracking or NAT, to
avoid loops and other problems.