left|rightsourceip=1.2.3.4
This assigns the IP address specified to the interface pluto is bound to (usually ipsec0, or whatever interface is the default route).
It is essentially the same as doing:
ip addr add 1.2.3.4/32 dev $PLUTO_INTERFACE ip route change $RIGHTSUBNET dev $PLUTO_INTERFACE src 1.2.3.4
Note that this interface is deleted when the tunnels go down, or Openswan is stopped.
