Arp2wol, small hack to send wake on lan frames based on arp requests.
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This is the second version.
It takes the destination IP, destination subnet and destination mac as parameter now.This version allow one to run it multiple times without interfering with other running tcpdumps.
Also tcpdump runs without putting the interface into promiscuous mode.example to start it:
arp2wol.sh 10.0.8.33 10.0.8.255 01ad:be:ef:33 &#! /bin/sh # This program listens for arp lookups and triggers something INTERFACE=vr2 # Listen on this interface. RESTART="1200" # After the trigger, wait this long to start listening again. TARGET_IP=$1 # Listen for this IP. TARGET_BROADCAST=$2 # Broadcast to send the wol frame to. TARGET_MAC=$3 # MAC address to send the wol frame to. # Create path to initial pid file. add some randomness in case you want to run it multiple times pid="/var/run/dumper$(cat /dev/urandom | tr -dc '0-9' | head -c 10).pid" while true do # Check if not another process is using the same pidfile. while [ -f $pid ] do pid="/var/run/dumper$(cat /dev/urandom | tr -dc '0-9' | head -c 10).pid" done; # Actually run tcpdump (tcpdump -p -S -l -n -i $INTERFACE arp dst $TARGET_IP & echo $! >&3 ) 3>$pid | while read data do if [ -f $pid ]; then fping -c 1 $TARGET_IP if [ "$?" -ne "0" ]; then logger -t arp2wol "$TARGET_IP is down, starting it." wol -i $TARGET_BROADCAST $TARGET_MAC fi kill -9 $(cat $pid) rm $pid fi done; sleep $RESTART done;
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Interesting idea, thanks…
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Thank you very much.
In addition with the help from https://doc.pfsense.org/index.php/Executing_commands_at_boot_time
it is the answer for my question :-) -
First wanted to thank GruensFroeschli,
i used his script on ASUS 68U router then switched to PFSENSE, both works fine.
However, in pfsense the "cat /dev/urandom" causes a loop when the script is used at shellcmd and observed a high CPU use.i modified the script slightly to fix this problem, any suggestion to enhance it would be great
#! /bin/sh # This program listens for arp lookups and triggers something INTERFACE=re1 # Listen on this interface. RESTART="120" # After the trigger, wait this long to start listening again. TARGET_IP=$1 # Listen for this IP. TARGET_BROADCAST=$2 # Broadcast to send the wol frame to. TARGET_MAC=$3 # MAC address to send the wol frame to. # Create path to initial pid file. add some randomness in case you want to run it multiple times #pid="/var/run/dumper$(cat /dev/urandom | tr -dc '0-9' | head -c 10).pid" pid="/var/run/dumper$$.pid" trap 'rm -f $pid; exit' EXIT SIGHUP SIGINT SIGTERM while true do # check if not another process is using the same pidfile. #while [ -f $pid ] #do #pid="/var/run/dumper$(cat /dev/urandom | tr -dc '0-9' | head -c 10).pid" #pid="/var/run/dumper$$.pid" #done; # Actually run tcpdump (/usr/sbin/tcpdump -p -S -l -n -v -i $INTERFACE arp dst $TARGET_IP & echo $! >&3 ) 3>$pid | while read data do if [ -f $pid ]; then /usr/local/sbin/fping -c 1 $TARGET_IP if [ "$?" -ne "0" ]; then /usr/bin/logger -t arp2wol "$TARGET_IP is down, starting it." /usr/local/bin/wol -i $TARGET_BROADCAST $TARGET_MAC fi kill -9 $(cat $pid) rm $pid fi done; sleep $RESTART done;
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hmmm.
I'm running this still myself but i haven't seen a loop at all.
What happens if you executecat /dev/urandom | tr -dc '0-9' | head -c 10
on a shell directly?
Your change will not work if you start multiple instances from the same shell since $$ returns the pid of the shell where you ask for $$.
–> Running it multiple time will reuse the same file and break.On pfSense you could use jot to get a random number and then remove the \n.
e.g.
jot -r 1 0 9999999999 | tr -d '\n' -
it works fine if i run it from the shell directly, it loops only when i run it on boot using shell comand or *sh file under /usr/local/etc/rc.d.
The $$ should have a different value(PID) every time you start the script, no? not sure this will work properly with scripts running in the background.
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The $$ should have a different value(PID) every time you start the script, no? not sure this will work properly with scripts running in the background.
No $$ returns the pid of the current shell.
If you fork multiple instance of the arp2wol.sh then all of them will have the same parent (the init script which executes it).
–> All of them will use the same pid-file. -
thank you let me test jot.
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Many thanks for this script :D
Does this log the source of the arp request?
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Not really, but you can easily extend it to do this.
$data contains the line which triggered the event.
–> the arp responses look something like13:22:24.457157 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 80.219.3.42 tell 80.219.2.1, length 46
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Can this script to be modified to work across subnets ie the device I want to wake up in this instance is on a different subnet to everything that is waking it connected to lan interface em2, those devices waking it are connected to lan em1?
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I don't know, but this really has nothing to do with this script.
This script exists to trigger something based on ARP lookups.
What you trigger is your own thing.Try reading the documentation of the /usr/local/bin/wol which is used on pfsense to send magic packet.
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I am not 100% sure but I think all I need to do is remove "arp" from the tcpdump command and ensure $TARGET_BROADCAST $TARGET_MAC are those of the machine to be woken and $INTERFACE is the lan on the source machines trying to access the target?
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A client trying access a server on a different network segment (subnet) will never issue an ARP broadcast for the destination address because MAC addresses are local to the connected segment and access to the outside of the local segment is done via a gateway (the router in between the segments). In other words, the MAC address of the destination host won't show up in the traffic of the client's network. You have to monitor the destination IP instead and then trigger the WOL action on the other network segment where the to be woken up hosts are.
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Yep, removing the arp and it works great, I am actually doing it via port , thanks again for the script.
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If you want to change what the tcpdump is looking for:
Here is some documentation to that: http://www.tcpdump.org/manpages/pcap-filter.7.html -
I am using the original script posted by @GruensFroeschli with shellcmd. The cpu usage jumps to 100% when I use shellcmd through gui. When I run it as a sh script in ssh, it runs fine and cpu usage stays at 5% but need to login each time after reboot to do that. I am a newbie. Any help is greatly appreciated. I am running 2.4.2-RELEASE-p1 (amd64). Thanks !
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Anyone have any suggestions .. TIA