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+The isdn diversion services are a supporting module working together with
+the isdn4linux and the HiSax module for passive cards.
+Active cards, TAs and cards using a own or other driver than the HiSax
+module need to be adapted to the HL<->LL interface described in a separate
+document. The diversion services may be used with all cards supported by
+the HiSax driver.
+The diversion kernel interface and controlling tool divertctrl were written
+by Werner Cornelius ( or under the
+GNU General Public License.
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ GNU General Public License for more details.
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+Table of contents
+1. Features of the i4l diversion services
+ (Or what can the i4l diversion services do for me)
+2. Required hard- and software
+3. Compiling, installing and loading/unloading the module
+ Tracing calling and diversion information
+4. Tracing calling and diversion information
+5. Format of the divert device ASCII output
+1. Features of the i4l diversion services
+ (Or what can the i4l diversion services do for me)
+ The i4l diversion services offers call forwarding and logging normally
+ only supported by isdn phones. Incoming calls may be diverted
+ unconditionally (CFU), when not reachable (CFNR) or on busy condition
+ (CFB).
+ The diversions may be invoked statically in the providers exchange
+ as normally done by isdn phones. In this case all incoming calls
+ with a special (or all) service identifiers are forwarded if the
+ forwarding reason is met. Activated static services may also be
+ interrogated (queried).
+ The i4l diversion services additionally offers a dynamic version of
+ call forwarding which is not preprogrammed inside the providers exchange
+ but dynamically activated by i4l.
+ In this case all incoming calls are checked by rules that may be
+ compared to the mechanism of ipfwadm or ipchains. If a given rule matches
+ the checking process is finished and the rule matching will be applied
+ to the call.
+ The rules include primary and secondary service identifiers, called
+ number and subaddress, callers number and subaddress and whether the rule
+ matches to all filtered calls or only those when all B-channel resources
+ are exhausted.
+ Actions that may be invoked by a rule are ignore, proceed, reject,
+ direct divert or delayed divert of a call.
+ All incoming calls matching a rule except the ignore rule a reported and
+ logged as ASCII via the proc filesystem (/proc/net/isdn/divert). If proceed
+ is selected the call will be held in a proceeding state (without ringing)
+ for a certain amount of time to let an external program or client decide
+ how to handle the call.
+2. Required hard- and software
+ For using the i4l diversion services the isdn line must be of a EURO/DSS1
+ type. Additionally the i4l services only work together with the HiSax
+ driver for passive isdn cards. All HiSax supported cards may be used for
+ the diversion purposes.
+ The static diversion services require the provider having static services
+ CFU, CFNR, CFB activated on an MSN-line. The static services may not be
+ used on a point-to-point connection. Further the static services are only
+ available in some countries (for example germany). Countries requiring the
+ keypad protocol for activating static diversions (like the netherlands) are
+ not supported but may use the tty devices for this purpose.
+ The dynamic diversion services may be used in all countries if the provider
+ enables the feature CF (call forwarding). This should work on both MSN- and
+ point-to-point lines.
+ To add and delete rules the additional divertctrl program is needed. This
+ program is part of the isdn4kutils package.
+3. Compiling, installing and loading/unloading the module
+ Tracing calling and diversion information
+ To compile the i4l code with diversion support you need to say yes to the
+ DSS1 diversion services when selecting the i4l options in the kernel
+ config (menuconfig or config).
+ After having properly activated a make modules and make modules_install all
+ required modules will be correctly installed in the needed modules dirs.
+ As the diversion services are currently not included in the scripts of most
+ standard distributions you will have to add a "insmod dss1_divert" after
+ having loaded the global isdn module.
+ The module can be loaded without any command line parameters.
+ If the module is actually loaded and active may be checked with a
+ "cat /proc/modules" or "ls /proc/net/isdn/divert". The divert file is
+ dynamically created by the diversion module and removed when the module is
+ unloaded.
+4. Tracing calling and diversion information
+ You also may put a "cat /proc/net/isdn/divert" in the background with the
+ output redirected to a file. Then all actions of the module are logged.
+ The divert file in the proc system may be opened more than once, so in
+ conjunction with inetd and a small remote client on other machines inside
+ your network incoming calls and reactions by the module may be shown on
+ every listening machine.
+ If a call is reported as proceeding an external program or client may
+ specify during a certain amount of time (normally 4 to 10 seconds) what
+ to do with that call.
+ To unload the module all open files to the device in the proc system must
+ be closed. Otherwise the module (and isdn.o) may not be unloaded.
+5. Format of the divert device ASCII output
+ To be done later