
proc make_ping {name len} {
	pinit ip $name
	pset $name ip proto icmp
	pcast $name end data
	plen $name data [expr $len - 20]
	pwrite $name b 20 8 0
	set dlen [expr $len - 20]
	for {set off 24} {$off < $len} {incr off} {
		pwrite $name b $off $off
	}
	pset $name ip len $len
	pwrite $name w 11 [ip.cksum $name 20 $dlen]
}
