This problem rears its head in many applications. Some WINE apps, for
example, try to connect to ALL defined cups printers (regardless of
whether they are set as default, or were the "last-used" printer), and
hang, waiting for connection to remote printer which isn't connected.
Another example is "vym", which won't even start if it cannot connect to
ALL printers.. see https://bugzilla.novell.com/show_bug.cgi?id=418439
...
Some apps will timeout, but some seem to hang forever (Adobe acrobat).
MacOS uses CUPS - I wonder how it handles the same situation??
Anyway, the best solution I could find so far is based on what was
posted above by Sangala. IE. a script that checks which printer is
accessible and IF NOT, rejects packets destined there.
I toyed with the idea of having a script which actually removed the
printer from cups (lpadmin -x), but re-creating the printer is a little
more involved, and it seems like overkill. Unfortunately disabling or
rejecting the printer within CUPS, does not stop it from broadcasting
the printer to requesting applications.
Anyway, I simplified Sangala's script (removing requirement for MAC) and
put it in cron to run every 5 minutes (this is on a server running 24x7
with some off and on VPN connected printers):
#!/bin/bash
PINGTIME=3
PINGCOUNT=1
PINGCMD="/bin/ping"
processByPing(){
if [ $# -eq 2 ]; then
$PINGCMD -c $PINGCOUNT -q -W $PINGTIME $1 > /dev/null
if [ $? = 0 ]; then
iptables -D OUTPUT -p tcp -d $1 --dport $2 -j REJECT &> /dev/null
#"Printer on IP: $1 port: $2 is accessible"
else
iptables -D OUTPUT -p tcp -d $1 --dport $2 -j REJECT &> /dev/null
iptables -I OUTPUT -p tcp -d $1 --dport $2 -j REJECT &> /dev/null
#"Printer on IP: $1 port: $2 is NOT accessible"
fi
else
echo "Bad parameters"
fi
}
#Detect remote printers
#every remote printer server or printers
#1st IP addres
#2nd port
processByPing 10.8.0.62 631 #vpn connected printer #1
processByPing 10.8.0.74 631 #vpn connected printer #2
exit 0
I saved it as /usr/local/sbin/reject-remote-printers (and chmod 744) and added
this to cron:
*/5 * * * * /usr/local/sbin/reject-remote-printers
This way, within 5 mintues of VPN users connecting, their printers are
able to receive packets... and within 5 minutes of disconnecting, the
packets are rejected.
Thanks Sangala for the idea! It maybe convoluted, but it works!!
** Bug watch added: Novell/SUSE Bugzilla #418439
https://bugzilla.novell.com/show_bug.cgi?id=418439
--
remote printer : freeze when not available
https://bugs.launchpad.net/bugs/264333
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