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diff --git a/docs/htmldocs/Samba3-Developers-Guide/devprinting.html b/docs/htmldocs/Samba3-Developers-Guide/devprinting.html new file mode 100644 index 0000000000..a68cce597c --- /dev/null +++ b/docs/htmldocs/Samba3-Developers-Guide/devprinting.html @@ -0,0 +1,215 @@ +<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 15. Samba Printing Internals</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.72.0"><link rel="start" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt04.html" title="Part IV. Debugging and tracing"><link rel="prev" href="tracing.html" title="Chapter 14. Tracing samba system calls"><link rel="next" href="pt05.html" title="Part V. Appendices"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 15. Samba Printing Internals</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="tracing.html">Prev</a> </td><th width="60%" align="center">Part IV. Debugging and tracing</th><td width="20%" align="right"> <a accesskey="n" href="pt05.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="devprinting"></a>Chapter 15. Samba Printing Internals</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Gerald</span> <span class="surname">Carter</span></h3></div></div><div><p class="pubdate">October 2002</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="devprinting.html#id334024">Abstract</a></span></dt><dt><span class="sect1"><a href="devprinting.html#id334035"> +Printing Interface to Various Back ends +</a></span></dt><dt><span class="sect1"><a href="devprinting.html#id334109"> +Print Queue TDB's +</a></span></dt><dt><span class="sect1"><a href="devprinting.html#id334247"> +ChangeID and Client Caching of Printer Information +</a></span></dt><dt><span class="sect1"><a href="devprinting.html#id334258"> +Windows NT/2K Printer Change Notify +</a></span></dt></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id334024"></a>Abstract</h2></div></div></div><p> +The purpose of this document is to provide some insight into +Samba's printing functionality and also to describe the semantics +of certain features of Windows client printing. +</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id334035"></a> +Printing Interface to Various Back ends +</h2></div></div></div><p> +Samba uses a table of function pointers to seven functions. The +function prototypes are defined in the <code class="varname">printif</code> structure declared +in <code class="filename">printing.h</code>. +</p><div class="itemizedlist"><ul type="disc"><li><p>retrieve the contents of a print queue</p></li><li><p>pause the print queue</p></li><li><p>resume a paused print queue</p></li><li><p>delete a job from the queue</p></li><li><p>pause a job in the print queue</p></li><li><p>result a paused print job in the queue</p></li><li><p>submit a job to the print queue</p></li></ul></div><p> +Currently there are only two printing back end implementations +defined. +</p><div class="itemizedlist"><ul type="disc"><li><p>a generic set of functions for working with standard UNIX + printing subsystems</p></li><li><p>a set of CUPS specific functions (this is only enabled if + the CUPS libraries were located at compile time).</p></li></ul></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id334109"></a> +Print Queue TDB's +</h2></div></div></div><p> +Samba provides periodic caching of the output from the "lpq command" +for performance reasons. This cache time is configurable in seconds. +Obviously the longer the cache time the less often smbd will be +required to exec a copy of lpq. However, the accuracy of the print +queue contents displayed to clients will be diminished as well. +</p><p> +The list of currently opened print queue TDB's can be found +be examining the list of tdb_print_db structures ( see print_db_head +in printing.c ). A queue TDB is opened using the wrapper function +printing.c:get_print_db_byname(). The function ensures that smbd +does not open more than MAX_PRINT_DBS_OPEN in an effort to prevent +a large print server from exhausting all available file descriptors. +If the number of open queue TDB's exceeds the MAX_PRINT_DBS_OPEN +limit, smbd falls back to a most recently used algorithm for maintaining +a list of open TDB's. +</p><p> +There are two ways in which a a print job can be entered into +a print queue's TDB. The first is to submit the job from a Windows +client which will insert the job information directly into the TDB. +The second method is to have the print job picked up by executing the +"lpq command". +</p><pre class="programlisting"> +/* included from printing.h */ +struct printjob { + pid_t pid; /* which process launched the job */ + int sysjob; /* the system (lp) job number */ + int fd; /* file descriptor of open file if open */ + time_t starttime; /* when the job started spooling */ + int status; /* the status of this job */ + size_t size; /* the size of the job so far */ + int page_count; /* then number of pages so far */ + BOOL spooled; /* has it been sent to the spooler yet? */ + BOOL smbjob; /* set if the job is a SMB job */ + fstring filename; /* the filename used to spool the file */ + fstring jobname; /* the job name given to us by the client */ + fstring user; /* the user who started the job */ + fstring queuename; /* service number of printer for this job */ + NT_DEVICEMODE *nt_devmode; +}; +</pre><p> +The current manifestation of the printjob structure contains a field +for the UNIX job id returned from the "lpq command" and a Windows job +ID (32-bit bounded by PRINT_MAX_JOBID). When a print job is returned +by the "lpq command" that does not match an existing job in the queue's +TDB, a 32-bit job ID above the <*vance doesn't know what word is missing here*> is generating by adding UNIX_JOB_START to +the id reported by lpq. +</p><p> +In order to match a 32-bit Windows jobid onto a 16-bit lanman print job +id, smbd uses an in memory TDB to match the former to a number appropriate +for old lanman clients. +</p><p> +When updating a print queue, smbd will perform the following +steps ( refer to <code class="filename">print.c:print_queue_update()</code> ): +</p><div class="orderedlist"><ol type="1"><li><p>Check to see if another smbd is currently in + the process of updating the queue contents by checking the pid + stored in <code class="constant">LOCK/<em class="replaceable"><code>printer_name</code></em></code>. + If so, then do not update the TDB.</p></li><li><p>Lock the mutex entry in the TDB and store our own pid. + Check that this succeeded, else fail.</p></li><li><p>Store the updated time stamp for the new cache + listing</p></li><li><p>Retrieve the queue listing via "lpq command"</p></li><li><pre class="programlisting"> + foreach job in the queue + { + if the job is a UNIX job, create a new entry; + if the job has a Windows based jobid, then + { + Lookup the record by the jobid; + if the lookup failed, then + treat it as a UNIX job; + else + update the job status only + } + }</pre></li><li><p>Delete any jobs in the TDB that are not + in the in the lpq listing</p></li><li><p>Store the print queue status in the TDB</p></li><li><p>update the cache time stamp again</p></li></ol></div><p> +Note that it is the contents of this TDB that is returned to Windows +clients and not the actual listing from the "lpq command". +</p><p> +The NT_DEVICEMODE stored as part of the printjob structure is used to +store a pointer to a non-default DeviceMode associated with the print +job. The pointer will be non-null when the client included a Device +Mode in the OpenPrinterEx() call and subsequently submitted a job for +printing on that same handle. If the client did not include a Device +Mode in the OpenPrinterEx() request, the nt_devmode field is NULL +and the job has the printer's device mode associated with it by default. +</p><p> +Only non-default Device Mode are stored with print jobs in the print +queue TDB. Otherwise, the Device Mode is obtained from the printer +object when the client issues a GetJob(level == 2) request. +</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id334247"></a> +ChangeID and Client Caching of Printer Information +</h2></div></div></div><p> +[To be filled in later] +</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id334258"></a> +Windows NT/2K Printer Change Notify +</h2></div></div></div><p> +When working with Windows NT+ clients, it is possible for a +print server to use RPC to send asynchronous change notification +events to clients for certain printer and print job attributes. +This can be useful when the client needs to know that a new +job has been added to the queue for a given printer or that the +driver for a printer has been changed. Note that this is done +entirely orthogonal to cache updates based on a new ChangeID for +a printer object. +</p><p> +The basic set of RPC's used to implement change notification are +</p><div class="itemizedlist"><ul type="disc"><li><p>RemoteFindFirstPrinterChangeNotifyEx ( RFFPCN )</p></li><li><p>RemoteFindNextPrinterChangeNotifyEx ( RFNPCN )</p></li><li><p>FindClosePrinterChangeNotify( FCPCN )</p></li><li><p>ReplyOpenPrinter</p></li><li><p>ReplyClosePrinter</p></li><li><p>RouteRefreshPrinterChangeNotify ( RRPCN )</p></li></ul></div><p> +One additional RPC is available to a server, but is never used by the +Windows spooler service: +</p><div class="itemizedlist"><ul type="disc"><li><p>RouteReplyPrinter()</p></li></ul></div><p> +The opnum for all of these RPC's are defined in include/rpc_spoolss.h +</p><p> +Windows NT print servers use a bizarre method of sending print +notification event to clients. The process of registering a new change +notification handle is as follows. The 'C' is for client and the +'S' is for server. All error conditions have been eliminated. +</p><pre class="programlisting"> +C: Obtain handle to printer or to the printer + server via the standard OpenPrinterEx() call. +S: Respond with a valid handle to object + +C: Send a RFFPCN request with the previously obtained + handle with either (a) set of flags for change events + to monitor, or (b) a PRINTER_NOTIFY_OPTIONS structure + containing the event information to monitor. The windows + spooler has only been observed to use (b). +S: The <* another missing word*> opens a new TCP session to the client (thus requiring + all print clients to be CIFS servers as well) and sends + a ReplyOpenPrinter() request to the client. +C: The client responds with a printer handle that can be used to + send event notification messages. +S: The server replies success to the RFFPCN request. + +C: The windows spooler follows the RFFPCN with a RFNPCN + request to fetch the current values of all monitored + attributes. +S: The server replies with an array SPOOL_NOTIFY_INFO_DATA + structures (contained in a SPOOL_NOTIFY_INFO structure). + +C: If the change notification handle is ever released by the + client via a FCPCN request, the server sends a ReplyClosePrinter() + request back to the client first. However a request of this + nature from the client is often an indication that the previous + notification event was not marshalled correctly by the server + or a piece of data was wrong. +S: The server closes the internal change notification handle + (POLICY_HND) and does not send any further change notification + events to the client for that printer or job. +</pre><p> +The current list of notification events supported by Samba can be +found by examining the internal tables in srv_spoolss_nt.c +</p><div class="itemizedlist"><ul type="disc"><li><p>printer_notify_table[]</p></li><li><p>job_notify_table[]</p></li></ul></div><p> +When an event occurs that could be monitored, smbd sends a message +to itself about the change. The list of events to be transmitted +are queued by the smbd process sending the message to prevent an +overload of TDB usage and the internal message is sent during smbd's +idle loop (refer to printing/notify.c and the functions +send_spoolss_notify2_msg() and print_notify_send_messages() ). +</p><p> +The decision of whether or not the change is to be sent to connected +clients is made by the routine which actually sends the notification. +( refer to srv_spoolss_nt.c:recieve_notify2_message() ). +</p><p> +Because it possible to receive a listing of multiple changes for +multiple printers, the notification events must be split into +categories by the printer name. This makes it possible to group +multiple change events to be sent in a single RPC according to the +printer handle obtained via a ReplyOpenPrinter(). +</p><p> +The actual change notification is performed using the RRPCN request +RPC. This packet contains +</p><div class="itemizedlist"><ul type="disc"><li><p>the printer handle registered with the +client's spooler on which the change occurred</p></li><li><p>The change_low value which was sent as part +of the last RFNPCN request from the client</p></li><li><p>The SPOOL_NOTIFY_INFO container with the event +information</p></li></ul></div><p> +A <code class="varname">SPOOL_NOTIFY_INFO</code> contains: +</p><div class="itemizedlist"><ul type="disc"><li><p>the version and flags field are predefined +and should not be changed</p></li><li><p>The count field is the number of entries +in the SPOOL_NOTIFY_INFO_DATA array</p></li></ul></div><p> +The <code class="varname">SPOOL_NOTIFY_INFO_DATA</code> entries contain: +</p><div class="itemizedlist"><ul type="disc"><li><p>The type defines whether or not this event +is for a printer or a print job</p></li><li><p>The field is the flag identifying the event</p></li><li><p>the notify_data union contains the new valuie of the +attribute</p></li><li><p>The enc_type defines the size of the structure for marshalling +and unmarshalling</p></li><li><p>(a) the id must be 0 for a printer event on a printer handle. +(b) the id must be the job id for an event on a printer job +(c) the id must be the matching number of the printer index used +in the response packet to the RFNPCN when using a print server +handle for notification. Samba currently uses the snum of +the printer for this which can break if the list of services +has been modified since the notification handle was registered.</p></li><li><p>The size is either (a) the string length in UNICODE for strings, +(b) the size in bytes of the security descriptor, or (c) 0 for +data values.</p></li></ul></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="tracing.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt04.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="pt05.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 14. Tracing samba system calls </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Part V. Appendices</td></tr></table></div></body></html> |