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7dbf77c9 1$Cambridge: exim/doc/doc-txt/NewStuff,v 1.30 2005/03/22 16:52:06 ph10 Exp $
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2
3New Features in Exim
4--------------------
5
6This file contains descriptions of new features that have been added to Exim,
7but have not yet made it into the main manual (which is most conveniently
8updated when there is a relatively large batch of changes). The doc/ChangeLog
9file contains a listing of all changes, including bug fixes.
10
11
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12Version 4.51
13------------
14
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15PH/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.
20
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.
24
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:
29
30 # rm -f new.params
31 # touch new.params
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
38
39 If Exim never has to generate the parameters itself, the possibility of
40 stalling is removed.
41
42PH/02 A new expansion item for dynamically loading and calling a locally-
43 written C function is now provided, if Exim is compiled with
44
45 EXPAND_DLFUNC=yes
46
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.)
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49
50 If you enable EXPAND_DLFUNC, you should also be aware of the new redirect
51 router option forbid_filter_dlfunc. If you have unprivileged users on
52 your system who are permitted to create filter files, you might want to
53 set forbid_filter_dlfunc=true in the appropriate router, to stop them
54 using ${dlfunc to run code within Exim.
55
56 You load and call an external function like this:
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57
58 ${dlfunc{/some/file}{function}{arg1}{arg2}...}
59
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60 Once loaded, Exim remembers the dynamically loaded object so that it
61 doesn't reload the same object file in the same Exim process (but of
62 course Exim does start new processes frequently).
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63
64 There may be from zero to eight arguments to the function. When compiling
65 a local function that is to be called in this way, local_scan.h should be
66 included. The Exim variables and functions that are defined by that API
67 are also available for dynamically loaded functions. The function itself
68 must have the following type:
69
70 int dlfunction(uschar **yield, int argc, uschar *argv[])
71
72 Where "uschar" is a typedef for "unsigned char" in local_scan.h. The
73 function should return one of the following values:
74
75 OK Success. The string that is placed in "yield" is put into
76 the expanded string that is being built.
77
78 FAIL A non-forced expansion failure occurs, with the error
79 message taken from "yield", if it is set.
80
81 FAIL_FORCED A forced expansion failure occurs, with the error message
82 taken from "yield" if it is set.
83
84 ERROR Same as FAIL, except that a panic log entry is written.
85
86 When compiling a function that is to be used in this way with gcc,
87 you need to add -shared to the gcc command. Also, in the Exim build-time
88 configuration, you must add -export-dynamic to EXTRALIBS.
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90TF/01 $received_time is a new expansion variable containing the time and date
91 as a number of seconds since the start of the Unix epoch when the
92 current message was received.
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f7b63901 94Version 4.50
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95------------
96
b9e40c51 97The documentation is up-to-date for the 4.50 release.
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98
99****