/[smeserver]/rpms/qmail/sme10/moreipme.README
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Contents of /rpms/qmail/sme10/moreipme.README

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Revision 1.1 - (show annotations) (download)
Thu Apr 13 15:55:52 2017 UTC (7 years, 6 months ago) by unnilennium
Branch: MAIN
CVS Tags: qmail-1_03-21_el7_sme, qmail-1_03-25_el7_sme, HEAD
* Thu Apr 13 2017 Jean-Philipe Pialasse <tests@pialasse.com> 1.03-21.sme
- added documentation [SME: 9705]
- added binaries ipmetest et ipmeprint to help configuration

1 ###########
2 ### WHO ###
3 ###########
4
5 This patch was written by Scott Gifford <sgifford@suspectclass.com>.
6 The design and much of the code for supporting "notipme" was
7 contributed by Charles Cazabon <charlesc@discworld.dyndns.org>.
8
9
10 ############
11 ### WHAT ###
12 ############
13
14 This patch may be necessary in some configurations that involve network
15 address translation or port forwarding. It prevents a problem caused
16 by an MX or other mail routing directive instructing qmail to connect to
17 itself without realizing it's connecting to itself. When this happens,
18 it accepts the message, finds out where to deliver it to (itself), and
19 promptly reconnects to itself to deliver the message. Eventually, when
20 it has done this 20 or 30 times, it will give up and bounce the message,
21 but not before sucking up all of your CPU while it's happening.
22
23 It may also be useful in some configurations that have multiple qmail
24 servers configured on different interfaces of the same system. qmail
25 will normally refuse to deliver mail by SMTP to the machine it's
26 running on, but with multiple copies of qmail, you may want to prevent
27 this behavior.
28
29 Normally, qmail can detect what IP addresses refer to itself by getting
30 a list of all network interfaces with IP addresses from the operating
31 system. It uses this list to determine whether connecting to an address
32 will cause it to connect to itself, and avoid the situation (it calls
33 the perm_ambigmx() function, which prints the message:
34
35 Sorry. Although I'm listed as a best-preference MX or A for that host,
36 it isn't in my control/locals file, so I don't treat it as local. (#5.4.6)
37
38 But in situations where the OS is not aware of all IP addresses that
39 connect back to itself, this detection fails, causing the CPU-sucking
40 phenomenon described above. This can happen if there is a network
41 address translation device in front of the qmail server, such as a
42 load-balancer or a router which allows you to share one IP address among
43 several machines; if there is a port forwarder forwarding connections
44 from some other machine to the SMTP server on the qmail server; or in
45 configurations where a "dumb" mailserver is configured to use your qmail
46 server as a "smarthost", delivering all mail to it without inspection.
47
48 To solve this, other IP addresses which will ultimately connect back to
49 your machine can be added to the file "control/moreipme", one per line.
50 qmail will treat all addresses in this file exactly as if they were
51 local, and if it finds an MX record or other mail routing information
52 which would cause it to connect to any of these addresses, it will call
53 perm_ambigmx(), and print the above error message.
54
55 Additionally, IP addresses which the system detects but which should
56 *not* be treated as local can be removed from qmail's ipme list by
57 adding them to the file "control/notipme".
58
59 IP addresses can be specified as individual addresses in the usual
60 dotted-quad format, or as entire networks using a slash followed by
61 the full dotted-quad netmask:
62
63 127.0.0.1
64 127.0.0.1/255.255.255.255
65 127.0.0.0/255.0.0.0
66 10.0.0.0/255.255.255.0
67
68 An individual address is treated exactly like a network with a mask of
69 255.255.255.255. Addresses of interfaces found on the system are
70 added with their individual addresses. In addition, these addresses
71 are implicitly added:
72
73 0.0.0.0
74 127.0.0.0/255.0.0.0
75
76 So the list of system addresses (the "ipme" list) is, in order,
77 127.0.0.0/255.0.0.0, 0.0.0.0, then all actual interfaces on the system
78 in the order they are reported, then the contents of the "moreipme"
79 file. The list of excluded addresses (the "notipme" list) is just the
80 contents of the "notipme" file.
81
82 If an address appears in both the ipme list and the notipme list, the
83 entry with the longest netmask wins. If the netmask lengths are the
84 same, notipme wins.
85
86 For example, if the ipme list has 127.0.0.0/255.0.0.0 and notipme has
87 127.0.0.2, then 127.0.0.2 will not be considered me because the entry
88 in notipme has a 32-bit mask. If the notipme list has
89 127.0.0.0/255.0.0.0, all of 127.* will not be considered me.
90
91 You can run the program "ipmeprint" from the source directory to see
92 what interfaces qmail is detecting or finds in moreipme.
93
94 You can run the program "ipmetest" from the source directory to test
95 your configuration. It takes as its first and only parameter an IP
96 address to test, and prints either "me" or "not me".
97
98 ###########
99 ### HOW ###
100 ###########
101
102 To apply the patch, download and save it somewhere, then cd into your
103 qmail source directory.
104
105 For stock qmail, download qmail-1.03-moreipme-0.6.patch then run:
106
107 cd qmail-1.03
108 patch -p1 </path/to/qmail-1.03-moreipme-0.6.patch
109
110 For netqmail, first download netqmail-1.05, and run the included
111 collate.sh script. Then download netqmail-1.05-moreipme-0.6.patch and
112 apply it to the netqmail base directory, after runn:
113
114 cd netqmail-1.05
115 patch -p1 </path/to/netqmail-1.05-moreipme-0.6.patch
116
117
118 ###################
119 ### OTHER NOTES ###
120 ###################
121
122 This patch also incorporates the "0.0.0.0" patch, which causes qmail
123 to recognize the IP address 0.0.0.0 as a local address. See:
124
125 http://www.suspectclass.com/~sgifford/qmail/qmail-0.0.0.0.README
126
127 for more information, and
128
129 http://www.suspectclass.com/~sgifford/qmail/qmail-0.0.0.0.patch
130
131 for a copy of the patch.
132
133
134 ###############
135 ### HISTORY ###
136 ###############
137
138 2004 May 22 - Patch version 0.6 released. Fix from Richard Dawe where
139 masks weren't handled properly, removed some dead code,
140 updated comments and docs. Produce a copy of the patch
141 for netqmail-1.05.
142
143 2003 Apr 29 - Patch version 0.5 released. Added support for netmasks
144 in moreipme and notipme, ipmetest utility, 127/8 as
145 implicit ipme.
146
147 2002 Apr 26 - Patch version 0.4 released. Includes support for "notipme" file.
148 Many other small fixes and cleanups. Fixes ipmeprint to
149 chdir(/var/qmail) before running.
150
151 2001 Oct 8 - Original release of patch.
152
153 2001 Jan 22 - (roughly) Original release of 0.0.0.0 patch.
154

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