This networking enhancement is new in the Solaris Express 3/06 release.
The IP_NEXTHOP is a new IP-level socket option that specifies the address of the next hop for the traffic that originates from the socket. An application that has the IP_NEXTHOP option set bypasses the routing table lookups on the destination and sends packets directly to the specified onlink nexthop.
The thread that sets the IP_NEXTHOP option must have the PRIV_SYS_NET_CONFIG privilege.