#!/bin/sh
#udhcpc -?
#udhcpc: invalid option -- ?
#BusyBox v1.20.1 (2013-02-08 03:29:16 UTC) multi-call binary.
#Usage: udhcpc [-fbnqoCRB] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]
#[-V VENDOR] [-x OPT:VAL]... [-O OPT]...

#-i,--interface IFACE Interface to use (default eth0)
#-p,--pidfile FILE Create pidfile
#-s,--script PROG Run PROG at DHCP events (default /usr/share/udhcpc/default.script)
#-B,--broadcast Request broadcast replies
#-t,--retries N Send up to N discover packets
#-T,--timeout N Pause between packets (default 3 seconds)
#-A,--tryagain N Wait N seconds after failure (default 20)
#-f,--foreground Run in foreground
#-b,--background Background if lease is not obtained
#-n,--now Exit if lease is not obtained
#-q,--quit Exit after obtaining lease
#-R,--release Release IP on exit
#-S,--syslog Log to syslog too
#-a,--arping Use arping to validate offered address
#-O,--request-option OPT Request option OPT from server (cumulative)
#-o,--no-default-options Don't request any options (unless -O is given)
#-r,--request IP Request this IP address
#-x OPT:VAL Include option OPT in sent packets (cumulative)
   #Examples of string, numeric, and hex byte opts:
   #-x hostname:bbox - option 12
   #-x lease:3600 - option 51 (lease time)
   #-x 0x3d:0100BEEFC0FFEE - option 61 (client id)
#-F,--fqdn NAME Ask server to update DNS mapping for NAME
#-V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')
#-C,--clientid-none Don't send MAC as client identifier
iface=wlan0
if [ $# -eq 1 ]; then
    iface=$1
fi
killall udhcpc
sleep 1
udhcpc --timeout=5 --retries=8 -n -i $iface