Mail::Milter::Module::ConnectDNSBL - milter to accept/reject connecting hosts matching DNSBLs

       Todd Vierling, <tv@duh.org> <tv@pobox.com>

       In Sendmail 8.11 and 8.12, a milter rejection at "connect" stage does not allow the reply message to be
       set -- it simply becomes "not accepting messages".  However, this module still attempts to set the reply
       code and message in the hope that this will be fixed.

       This milter module rejects any connecting host whose IPv4 address matches a given DNS Blocking List
       (DNSBL).  It can also function as a whitelisting Chain element; see "accept_match()".

       The check used by this module is a simple "A" record lookup, via the standard "gethostbyname" lookup
       mechanism.  This method does not require the use of Net::DNS and is thus typically very fast.

       (Note:  If the connecting host is not using IPv4, this module will simply be a passthrough using
       SMFIS_CONTINUE.)

           new(DNSBL)

           new(DNSBL, MATCHRECORD[, ...])

           new(DNSBL, SUBREF)

           Creates a ConnectDNSBL object.  DNSBL is the root host hierarchy to use for lookups.  Three methods
           of matching can be used:

           If no additional arguments are provided, the match succeeds if there is any address entry present for
           the DNSBL lookup; the values are not examined.

           If one or more MATCHRECORD values are supplied, they are string representations of IPv4 addresses.
           If any of these match record values is the same as any address record returned by the DNSBL lookup,
           the match succeeds.

           If a SUBREF (reference to a subroutine; may be an anonymous inline "sub{}") is supplied, it is called
           for each of the address records returned by the DNSBL lookup.  The subroutine should return 0 or
           undef to indicate a failed match, and nonzero to indicate a successful match.  The subroutine
           receives a binary-encoded four byte scalar that should be transformed as needed with "inet_ntoa()" or
           "unpack".

           accept_match(FLAG)

           If FLAG is 0 (the default), a matching DNSBL will cause the connection to be rejected.

           If FLAG is 1, a matching DNSBL will cause this module to return SMFIS_ACCEPT instead.  This allows a
           "ConnectDNSBL" to be used inside a "Mail::Milter::Chain" container (in accept_break(1) mode), to
           function as a whitelist rather than a blacklist.

           This method returns a reference to the object itself, allowing this method call to be chained.

           ignore_tempfail(FLAG)

           If FLAG is 0 (the default), a DNSBL lookup which fails the underlying DNS query will cause the milter
           to return a temporary failure result (SMFIS_TEMPFAIL).

           If FLAG is 1, a temporary DNS failure will be treated as if the lookup resulted in an empty record
           set (SMFIS_CONTINUE).

           This method returns a reference to the object itself, allowing this method call to be chained.

           set_message(MESSAGE)

           Sets the message used when rejecting connections.  This string may contain the substring %A, which
           will be replaced by the matching IPv4 address, or %L, which will be replaced by the name of the
           matching DNSBL.

           This method returns a reference to the object itself, allowing this method call to be chained.

       Mail::Milter::Module::ConnectDNSBL - milter to accept/reject connecting hosts matching DNSBLs

       Hey! Theabovedocumenthadsomecodingerrors,whichareexplainedbelow:

       Around line 79:
           You can't have =items (as at line 91) unless the first thing after the =over is an =item

perl v5.36.0                                       2023-01-22             Mail::Milter::M...e::ConnectDNSBL(3pm)

       Mail::Milter::Object

           use Mail::Milter::Module::ConnectDNSBL;

           my $milter = new Mail::Milter::Module::ConnectDNSBL('foo.spamlist.dom');

           my $milter2 = &ConnectDNSBL('foo.spamlist.dom'); # convenience

           $milter2->set_message('Connections from %A disallowed');