• kill `pidof udhcpc`
  renegotiate DHCP lease
  (/etc/inittab's 'respawn' feature will bring udhcpc back)
• /bin/reboot
• /sbin/udhcpc renew &
• /usr/etc/init.d/plugin stop wireless; /usr/etc/init.d/plugin start wireless; /usr/etc/init.d/plugin start netconf; kill `pidof udhcpc`

Various places to look for clues about more sophisticated versions of the above:

• ps
• /etc/rc.d/rc ⇒ /etc/startup.list ⇒ /etc/sysinit/*.conf
• /etc/inittab
• /usr/www/*.cgi