1 $Cambridge: exim/doc/doc-txt/NewStuff,v 1.28 2005/03/22 14:11:54 ph10 Exp $
6 This file contains descriptions of new features that have been added to Exim,
7 but have not yet made it into the main manual (which is most conveniently
8 updated when there is a relatively large batch of changes). The doc/ChangeLog
9 file contains a listing of all changes, including bug fixes.
15 PH/01 The format in which GnuTLS parameters are written to the gnutls-param
16 file in the spool directory has been changed. This change has been made
17 to alleviate problems that some people had with the generation of the
18 parameters by Exim when /dev/random was exhausted. In this situation,
19 Exim would hang until /dev/random acquired some more entropy.
21 The new code exports and imports the DH and RSA parameters in PEM
22 format. This means that the parameters can be generated externally using
23 the certtool command that is part of GnuTLS.
25 To replace the parameters with new ones, instead of deleting the file
26 and letting Exim re-create it, you can generate new parameters using
27 certtool and, when this has been done, replace Exim's cache file by
28 renaming. The relevant commands are something like this:
32 # chown exim:exim new.params
33 # chmod 0400 new.params
34 # certtool --generate-privkey --bits 512 >new.params
35 # echo "" >>new.params
36 # certtool --generate-dh-params --bits 1024 >> new.params
37 # mv new.params params
39 If Exim never has to generate the parameters itself, the possibility of
42 PH/02 A new expansion item for dynamically loading and calling a locally-
43 written C function is now provided, if Exim is compiled with
47 set in Local/Makefile. The facility is not included by default (a
48 suitable error is given if you try to use it when it is not there.)
49 You load and call the function like this:
51 ${dlfunc{/some/file}{function}{arg1}{arg2}...}
53 Once loaded, Exim remembers it so that it doesn't reload it in the same
54 Exim process (but of course Exim does start new processes frequently).
56 There may be from zero to eight arguments to the function. When compiling
57 a local function that is to be called in this way, local_scan.h should be
58 included. The Exim variables and functions that are defined by that API
59 are also available for dynamically loaded functions. The function itself
60 must have the following type:
62 int dlfunction(uschar **yield, int argc, uschar *argv[])
64 Where "uschar" is a typedef for "unsigned char" in local_scan.h. The
65 function should return one of the following values:
67 OK Success. The string that is placed in "yield" is put into
68 the expanded string that is being built.
70 FAIL A non-forced expansion failure occurs, with the error
71 message taken from "yield", if it is set.
73 FAIL_FORCED A forced expansion failure occurs, with the error message
74 taken from "yield" if it is set.
76 ERROR Same as FAIL, except that a panic log entry is written.
78 When compiling a function that is to be used in this way with gcc,
79 you need to add -shared to the gcc command. Also, in the Exim build-time
80 configuration, you must add -export-dynamic to EXTRALIBS.
86 The documentation is up-to-date for the 4.50 release.