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1. Printing concept
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| @ VM |
| MS Publish Color Printer prints job |
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| LPDP (unprivileged port)
v
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| @ mltk |
| tcpsvd | lpd | printergui -> CUPS backend |
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| IPP :631 / LPDP :515
v
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| @ Printer@Printserver |
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| Printer |
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User prints from virtual machine using MS Publish Color Printer. MS Publish
Color Printer converts the document to postscript and delivers it to
standard LPDP-Port 515.
Data traffic gets rerouted by Minilinux kernel to an unprivileged port.
tcpsvd listens on <IP>:<PORT> and transfers the input to lpd.
lpd now saves this file, sets parameters as shell variable and starts a
helper program. This helper program is a GUI applikation which offers
miscellaneous options to the user.
After user confirmation printergui delivers the print job to the local cups
server. From here the job gets handled by standard Common Unix Printing
System services.
2. Implementation in Virtual Machines
In virtual (windows) machines the generic printer "MS Publish Color Printer"
will be used to deliver a print job after conversion to to postscrip to the
Linux host.
Setup in Windows:
Win8: (TODO: elaborate further / english messages)
add orinter
Der gesuchte Drucker ist nicht aufgeführt]
Lokaler Drucker oder Netzwerkdrucker nicht aufgeführt]
Vorhandener Anschluss : LPD
Generic] [MS Publish Color Printer
Win7: (TODO: elaborate further / english messages)
Startmenü, Geräte und Drucker
Drucker hinzufügen
Einen Netzwerk, Drahtlos oder Bluetoothdrucker hinzufügen
Suche beenden und Der gesuchte Drucker ist nicht aufgeführt
Drucker unter Verwendung einer TCP/IP-Adresse oder eines Hostnamens
hinzufügen, Weiter
Gerätetyp: TCP/IP Gerät, IP-Adresse 192.168.101.1, Haken weg bei
Treiberautomatik, Weiter.
Kaffee holen auf Windoof warten.
Benutzerdefiniert, Einstellungen
Protokoll : LPR, Warteschlangenname: STANDARD, LPR-Bytezählung aktivieren,
"OK".
Weiter
Hersteller: Generic, Drucker: MS Publisher Color Printer, Weiter.
(Empfohlener Treiber) Weiter
(Druckername) Weiter
Fertig stellen
WinXP: (TODO elaborate further / english messages)
3. Implementation in Linux host
Redirecting: Redirecting is done by Linux kernel, or to be specific,
by iptables:.
iptables -A INPUT -i br0 -p tcp --dport 515 -j DROP
iptables -A INPUT -i br0 -p tcp --dport 5515 -j DROP
iptables -t nat -A PREROUTING -p tcp --dport 515 -j REDIRECT --to-port 5515
4. Local spooler
Local spooler is an unix lpd provided by busybox. It gets it's input on
stdin from TCP/IP service daemon tcpsvd. tcpsvd listens on an unprivileged port
to incoming data and passes them to lpd. In case of an incoming print job the
file will be deposited in <spooldir>, meta data will be stored in shell
variables and <helperprogram> be started. At this parameters gan be given. To
facilitate printing a directory needs to be created in <spooldir> using the
same name as the desired printing queue:
busybox tcpsvd -E 0.0.0.0 5515 busybox lpd <spooldir> sh -c "<helperprogram>" &
For better understanding a snippet from source file lpd.c should be helpful:
* A typical usage of BB lpd looks as follows:
* # tcpsvd -E 0 515 lpd [SPOOLDIR] [HELPER-PROG [ARGS...]]
* This starts TCP listener on port 515 (default for LP protocol).
* When a client connection is made (via lpr) lpd first changes its
* working directory to SPOOLDIR (current dir is the default).
[...]
* If HELPER-PROG (with optional arguments) is specified then lpd continues
* to process client data:
* 1. it reads and parses control file (cfA...). The parse process
* results in setting environment variables whose values were passed
* in control file; when parsing is complete, lpd deletes control file.
* 2. it spawns specified helper application. It is then
* the helper application who is responsible for both actual printing
* and deleting of processed data file.
*
* A good lpr passes control files which when parsed provides the following
* variables:
* $H = host which issues the job
* $P = user who prints
* $C = class of printing (what is printed on banner page)
* $J = the name of the job
* $L = print banner page
* $M = the user to whom a mail should be sent if a problem occurs
*
* We specifically filter out and NOT provide:
* $l = name of datafile ("dfAxxx") - file whose content are to be printed
*
* lpd provides $DATAFILE instead - the ACTUAL name
* of the datafile under which it was saved.
* $l would be not reliable (you would be at mercy of remote peer).
*
* Thus, a typical helper can be something like this:
* #!/bin/sh
* cat ./"$DATAFILE" >/dev/lp0
* mv -f ./"$DATAFILE" save/
5. GUI / Custom CUPS Frontend
As said in chapter 4, Local Spooler, a helper program is needed for further
print job processing. Therefore a Qt-GUI application was developed (source
avaiulable at http://git.openslx.org/printergui.git/). This application
communicates with a local CUPS by CUPS-API, facilitated by libcups2.
The application offers configurated printers and several print options
supported by the chosen printer. After obtaining user confirmation the
print job and given options will be given to CUPS for further processing.
The application expects an user name as first parameter, and the file to be
printed as second parameter (see chapter 4, Local Spooler).
5. Local CUPS (to be elaborated further)
A standard CUPS can be used. A minimal setup needs these files:
/usr/sbin/cupsd
/etc/cups/cupsd.conf
/usr/lib/cups/
/usr/share/cups/
Needed configuration files:
/etc/cups/ppd/*
/etc/cups/printers.conf
(Original: https://lab.ks.uni-freiburg.de/projects/rzpools/wiki/_Drucken_)
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