$Cambridge: exim/doc/doc-txt/NewStuff,v 1.28 2005/03/22 14:11:54 ph10 Exp $

New Features in Exim
--------------------

This file contains descriptions of new features that have been added to Exim,
but have not yet made it into the main manual (which is most conveniently
updated when there is a relatively large batch of changes). The doc/ChangeLog
file contains a listing of all changes, including bug fixes.


Version 4.51
------------

PH/01 The format in which GnuTLS parameters are written to the gnutls-param
      file in the spool directory has been changed. This change has been made
      to alleviate problems that some people had with the generation of the
      parameters by Exim when /dev/random was exhausted. In this situation,
      Exim would hang until /dev/random acquired some more entropy.

      The new code exports and imports the DH and RSA parameters in PEM
      format. This means that the parameters can be generated externally using
      the certtool command that is part of GnuTLS.

      To replace the parameters with new ones, instead of deleting the file
      and letting Exim re-create it, you can generate new parameters using
      certtool and, when this has been done, replace Exim's cache file by
      renaming. The relevant commands are something like this:

        # rm -f new.params
        # touch new.params
        # chown exim:exim new.params
        # chmod 0400 new.params
        # certtool --generate-privkey --bits 512 >new.params
        # echo "" >>new.params
        # certtool --generate-dh-params --bits 1024 >> new.params
        # mv new.params params

      If Exim never has to generate the parameters itself, the possibility of
      stalling is removed.

PH/02 A new expansion item for dynamically loading and calling a locally-
      written C function is now provided, if Exim is compiled with

        EXPAND_DLFUNC=yes

      set in Local/Makefile. The facility is not included by default (a
      suitable error is given if you try to use it when it is not there.)
      You load and call the function like this:

        ${dlfunc{/some/file}{function}{arg1}{arg2}...}

      Once loaded, Exim remembers it so that it doesn't reload it in the same
      Exim process (but of course Exim does start new processes frequently).

      There may be from zero to eight arguments to the function. When compiling
      a local function that is to be called in this way, local_scan.h should be
      included. The Exim variables and functions that are defined by that API
      are also available for dynamically loaded functions. The function itself
      must have the following type:

        int dlfunction(uschar **yield, int argc, uschar *argv[])

      Where "uschar" is a typedef for "unsigned char" in local_scan.h. The
      function should return one of the following values:

      OK            Success. The string that is placed in "yield" is put into
                    the expanded string that is being built.

      FAIL          A non-forced expansion failure occurs, with the error
                    message taken from "yield", if it is set.

      FAIL_FORCED   A forced expansion failure occurs, with the error message
                    taken from "yield" if it is set.

      ERROR         Same as FAIL, except that a panic log entry is written.

      When compiling a function that is to be used in this way with gcc,
      you need to add -shared to the gcc command. Also, in the Exim build-time
      configuration, you must add -export-dynamic to EXTRALIBS.


Version 4.50
------------

The documentation is up-to-date for the 4.50 release.

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