The Setsockopt() call has five arguments. The arguments level and optname specify the option that you want to set. The simulator supports only the IPPROTO_IP level and the IP_FW_SET, IP_NAT_SET, and IP_IF_SET options (defined in $PDIR/include/Socket.h). The option value for the IP_IF_SET option needs to be a pointer to a struct if_info (defined in $PDIR/include/route.h). The data structures of the option values for IP_FW_SET and IP_NAT_SET have not been defined.