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CIDR_TABLE(5) File Formats Manual CIDR_TABLE(5)

NAME

cidr_table - format of Postfix CIDR tables

SYNOPSIS

postmap -q "string" cidr:/etc/postfix/filename
postmap -q - cidr:/etc/postfix/filename <inputfile

DESCRIPTION


The Postfix mail system uses optional lookup tables. These tables are usually in dbm or db format. Alternatively, lookup tables can be specified in CIDR (Classless Inter-Domain Routing) form. In this case, each input is compared against a list of patterns. When a match is found, the corresponding result is returned and the search is terminated.

To find out what types of lookup tables your Postfix system supports use the "postconf -m" command.

To test lookup tables, use the "postmap -q" command as described in the SYNOPSIS above.

TABLE FORMAT



The general form of a Postfix CIDR table is:



  

  
When a search string matches the specified pattern, use the
      corresponding result value. The pattern must be in
      network/prefix or network_address form (see ADDRESS PATTERN
      SYNTAX below).

  
!pattern result

  
When a search string does not match the specified pattern, use the
      specified result value. The pattern must be in
      network/prefix or network_address form (see ADDRESS PATTERN
      SYNTAX below).
    
This feature is available in Postfix 3.2 and later.

  

  

  

  

  
When a search string matches the specified pattern, match that
      search string against the patterns between if and endif. The
      pattern must be in network/prefix or network_address
      form (see ADDRESS PATTERN SYNTAX below). The if..endif can
      nest.
    
Note: do not prepend whitespace to text between
        if..endif.

    
This feature is available in Postfix 3.2 and later.

  

  

  

  

  
When a search string does not match the specified pattern, match
      that search string against the patterns between if and
      endif. The pattern must be in network/prefix or
      network_address form (see ADDRESS PATTERN SYNTAX below). The
      if..endif can nest.
    
Note: do not prepend whitespace to text between
        if..endif.

    
This feature is available in Postfix 3.2 and later.

  

  

  
Empty lines and whitespace-only lines are ignored, as are lines whose
      first non-whitespace character is a `#'.

  

  
A logical line starts with non-whitespace text. A line that starts with
      whitespace continues a logical line.








TABLE SEARCH ORDER




Patterns are applied in the order as specified in the table, until
    a pattern is found that matches the search string.






ADDRESS PATTERN SYNTAX




Postfix CIDR tables are pattern-based. A pattern is either a
    network_address which requires an exact match, or a
    network_address/prefix_length where the prefix_length part
    specifies the length of the network_address prefix that must be
    matched (the other bits in the network_address part must be
  zero).


An IPv4 network address is a sequence of four decimal octets
    separated by ".", and an IPv6 network address is a sequence of
    three to eight hexadecimal octet pairs separated by ":" or
    "::", where the latter is short-hand for a sequence of one or more
    all-zero octet pairs. The pattern 0.0.0.0/0 matches every IPv4 address, and
    ::/0 matches every IPv6 address. IPv6 support is available in Postfix 2.2
    and later.


Before comparisons are made, lookup keys and table entries are
    converted from string to binary. Therefore, IPv6 patterns will be matched
    regardless of leading zeros (a leading zero in an IPv4 address octet
    indicates octal notation).


Note: address information may be enclosed inside "[]"
    but this form is not required.






INLINE SPECIFICATION




The contents of a table may be specified in the table name
    (Postfix 3.7 and later). The basic syntax is:




main.cf:


    parameter = .. cidr:{ { rule-1 }, { rule-2 } .. } ..
master.cf:


    .. -o { parameter = .. cidr:{ { rule-1 }, { rule-2 } .. } .. } ..


Postfix ignores whitespace after '{' and before '}', and writes
    each rule as one text line to an in-memory file:




in-memory file:


    rule-1


    rule-2


    ..


Postfix parses the result as if it is a file in /etc/postfix.


Note: if a rule contains $, specify $$ to keep
    Postfix from trying to do $name expansion as it evaluates a parameter
    value.






EXAMPLE SMTPD ACCESS MAP




/etc/postfix/main.cf:


    smtpd_client_restrictions = ... cidr:/etc/postfix/client.cidr ...
/etc/postfix/client.cidr:


    # Rule order matters. Put more specific allowlist entries


    # before more general denylist entries.


    192.168.1.1             OK


    192.168.0.0/16          REJECT


    2001:db8::1             OK


    2001:db8::/32           REJECT






SEE ALSO


postmap(1), Postfix lookup table manager
regexp_table(5), format of regular expression tables
pcre_table(5), format of PCRE tables






README FILES




Use "postconf readme_directory" or
    "postconf html_directory" to locate this information.


DATABASE_README, Postfix lookup table overview






HISTORY




CIDR table support was introduced with Postfix version 2.1.






AUTHOR(S)


The CIDR table lookup code was originally written by:
Jozsef Kadlecsik
KFKI Research Institute for Particle and Nuclear Physics
POB. 49
1525 Budapest, Hungary
Adopted and adapted by:
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA