#!/bin/sh
# the next line restarts using scotty -*- tcl -*- \
exec scotty2.1.11 "$0" "$@"

package require Tnm 2.1

##
## This is very simple. We send a message to the UDP echo service
## and count the number of messages sent and received. The report
## proc is called to write a short report to stdout.
##

proc recv {ip f} {
    global stat
    catch {udp receive $f}
    incr stat(recv,$ip)
}

proc probe {ip f} {
    global stat
    catch {udp send $f "udp packet loss probing packet"}
    incr stat(send,$ip)
}

proc report {ip} {
    global stat
    if {[info exists stat(s,$ip)] && [info exists stat(r,$ip)]} {
	set send [expr $stat(send,$ip) - $stat(s,$ip)]
	set recv [expr $stat(recv,$ip) - $stat(r,$ip)]
	puts [format "%-30s %4d send %4d received %6.2f %% loss (%6.2f)" \
		$ip $send $recv [expr 100-$recv/double($send)*100] \
		[expr 100-$stat(recv,$ip)/double($stat(send,$ip))*100] ]
    }
    set stat(s,$ip) $stat(send,$ip)
    set stat(r,$ip) $stat(recv,$ip)
}

proc start {ip delay secs} {
    global stat
    set f [udp connect $ip echo]
    udp bind $f readable "recv $ip $f"
    set stat(send,$ip) 0
    set stat(recv,$ip) 0
    job create -command "report $ip" -interval [expr int($secs * 1000)]
    job create -command "probe $ip $f" -interval [expr int($delay * 1000)]
}

##
## Some command line parsing stuff.
##

set delay 5
set secs  60

set newargv ""
set parsing_options 1
while {([llength $argv] > 0) && $parsing_options} {
    set arg [lindex $argv 0]
    set argv [lrange $argv 1 end]
    if {[string index $arg 0] == "-"} {
        switch -- $arg  {
            "-d" { set delay [lindex $argv 0]
                   set argv  [lrange $argv 1 end]
                 }
            "-t" { set secs [lindex $argv 0]
                   set argv [lrange $argv 1 end]
                 }
            "--" { set parsing_options 0 }
        }
    } else {
        set parsing_options 0
        lappend newargv $arg
    }
}

set argv [concat $newargv $argv]
if {$argv == ""} { 
    puts stderr {usage: udploss [-d delay] [-t seconds] hosts}
} else {
    foreach host $argv {
	start $host $delay $secs
    }
}
