Version 8.7release_8_7

* NEWS: Update.
* configure.ac: Raise minor version.
* doc/functions.texi: Document new functions

Include the implementation of the NS resolving MFL functions, as
proposed by Jan Rafaj

* lib/dns.c (ns_lookup): New function.
* lib/dns.h (ns_lookup): New proto.
* mflib/dns.mf4 (hasns): New function.
* src/builtin/dns.bi (primitive_hasns, getns): New functions.

7 files changed, 216 insertions, 40 deletions

diff --git a/NEWS b/NEWS
index bc239bd3..86f6c7a9 100644
--- a/NEWS
+++ b/NEWS
@@ -1,29 +1,48 @@
-Mailfromd NEWS -- history of user-visible changes. 2018-11-12
+Mailfromd NEWS -- history of user-visible changes. 2019-01-03
 See the end of file for copying conditions.
 
 Please send Mailfromd bug reports to <bug-mailfromd@gnu.org.ua>
 
-Version 8.6.90 (Git)
+Version 8.7, 2019-01-03
 
 * The --callout-socket option
 
 New option --callout-socket=URL instructs mailfromd to use URL to pass
 callout requests to the callout server listening on URL. It is
 equivalent to the callout-url configuration statement, which it
 overrides.
 
 This option is used by mtasim to avoid clobbering the existing callout
 sockets when starting new mailfromd instance.
 
+* NS lookup NFL functions
+
+This release implements the following new MFL functions:
+
+number primitive_hasns (string DOM)
+  Returns 1 if the domain DOM has at least one NS record and 0
+  otherwise. Throws an error if DNS lookup fails.
+
+require 'dns'
+number hasns (string DOM)
+  Same as above, but returns 0 on DNS lookup failures.
+
+string getns (string DOM ; number RESOLVE, number SORT)
+
+  Returns a whitespace-separated list of all the NS records for
+  the domain DOM. If optional parameter RESOLVE is 1, the returned list
+  contains IP addresses. Optional SORT controls whether the entries are
+  sorted.
+
 * Bugfixes
 ** Callout functions return true on checking the null return address (<>)
 ** Arguments in transaction between mailfromd and calloutd are quoted
 ** Avoid false failures in testsuite due to libadns warnings
 ** configure --with-dbm=T accepts any T supported by mailutils
 ** The 'dbdel' built-in silently ignores non-existing keys
 
 Version 8.6, 2018-07-24
 
 * New configure option --with-dbm
 
 This option allows you to select any DBM flavor supported by mailutils
diff --git a/configure.ac b/configure.ac
index 3585d967..54c9ebd8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -7,26 +7,26 @@
 # any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 AC_PREREQ(2.63)
 m4_define([MF_VERSION_MAJOR], 8)
-m4_define([MF_VERSION_MINOR], 6)
-m4_define([MF_VERSION_PATCH], 90)
+m4_define([MF_VERSION_MINOR], 7)
+dnl m4_define([MF_VERSION_PATCH], 0)
 AC_INIT([mailfromd],
         MF_VERSION_MAJOR.MF_VERSION_MINOR[]m4_ifdef([MF_VERSION_PATCH],.MF_VERSION_PATCH),
         [bug-mailfromd@gnu.org.ua],
 	[mailfromd],
 	[http://www.gnu.org.ua/software/mailfromd])
 AC_CONFIG_SRCDIR([src/mailfromd.h])
 AC_CONFIG_AUX_DIR([build-aux])
 AC_CONFIG_HEADERS([config.h])
 AM_INIT_AUTOMAKE([1.11 gnits tar-ustar dist-bzip2 dist-xz std-options silent-rules])
 
 # Enable silent rules by default:
 AM_SILENT_RULES([yes])
diff --git a/doc/functions.texi b/doc/functions.texi
index 75eed904..d25911aa 100644
--- a/doc/functions.texi
+++ b/doc/functions.texi
@@ -1,20 +1,23 @@
 @c Copyright (C) 2005-2019 Sergey Poznyakoff
 @c Permission is granted to copy, distribute and/or modify this document
 @c under the terms of the GNU Free Documentation License, Version 1.3 or
 @c any later version published by the Free Software Foundation; with no
 @c Invariant Sections, with the Front and Back-Cover texts at your option. 
 
   This chapter describes library functions available in Mailfromd
-version @value{VERSION}. 
+version @value{VERSION}. For the simplicity of explanation, we use
+the word @samp{boolean} to indicate variables of numeric type that are
+used as boolean values. For such variables, the term @samp{False}
+stands for the numeric 0, and @samp{True} for any non-zero value.
 
 @menu
 * Macro access::
 * String manipulation::
 * String formatting::
 * Character Type::
 * Email processing functions::
 * Envelope modification functions::
 * Header modification functions::
 * Body Modification Functions::
 * Message modification queue::
 * Mail header functions::
@@ -56,25 +59,25 @@ not defined, raises the @code{e_macroundef} exception.
 
 Calling @code{getmacro(@var{name})} is completely equivalent to
 referencing @code{$@{@var{name}@}}, except that it allows to construct
 macro names programmatically, e.g.:
 
 @smallexample
   if getmacro("auth_%var") = "foo"
     @dots{}
   fi
 @end smallexample
 @end deftypefn
 
-@deftypefn {Built-in Function} number macro_defined (string @var{name})
+@deftypefn {Built-in Function} boolean macro_defined (string @var{name})
 Return true if Sendmail macro @var{name} is defined.
 @end deftypefn
 
   Notice, that if your @acronym{MTA} supports macro name
 negotiation@footnote{That is, if it supports Milter protocol 6 and
 upper.  Sendmail 8.14.0 and Postfix 2.6 and newer do.  MeTA1 (via
 @command{pmult}) does as well.  @xref{MTA Configuration}, for more
 details.}, you will have to export macro names used by these two
 functions using @samp{#pragma miltermacros} construct.  Consider this
 example:
 
 @smallexample
@@ -593,93 +596,93 @@ conversion specification is @samp{%%}.
 @node Character Type
 @section Character Type
 
 @cindex ctype_mismatch, global variable
 These functions check whether all characters of @var{str} fall into a
 certain character class according to the @samp{C} (@samp{POSIX})
 locale@footnote{Support for other locales is planned for future
 versions.}.  @samp{True} (1) is returned if they do, @samp{false} (0)
 is returned otherwise.  In the latter case, the global variable
 @code{ctype_mismatch} is set to the index of the first character that
 is outside of the character class (characters are indexed from 0).
 
-@deftypefn {Built-in Function} number isalnum (string @var{str})
+@deftypefn {Built-in Function} boolean isalnum (string @var{str})
 Checks for alphanumeric characters:
 
 @smallexample
   isalnum("a123") @result{} 1
   isalnum("a.123") @result{} 0 (ctype_mismatch = 1)
 @end smallexample
 @end deftypefn
 
-@deftypefn {Built-in Function} number isalpha (string @var{str})
+@deftypefn {Built-in Function} boolean isalpha (string @var{str})
 Checks for an alphabetic character:
 
 @smallexample
   isalnum("abc") @result{} 1
   isalnum("a123") @result{} 0
 @end smallexample
 @end deftypefn
 
-@deftypefn {Built-in Function} number isascii (string @var{str})
+@deftypefn {Built-in Function} boolean isascii (string @var{str})
 Checks whether all characters in @var{str} are 7-bit ones, that fit into
 the @acronym{ASCII} character set.
 
 @smallexample
   isascii("abc") @result{} 1
   isascii("ab\0200") @result{} 0
 @end smallexample  
 @end deftypefn
 
-@deftypefn {Built-in Function} number isblank (string @var{str})
+@deftypefn {Built-in Function} boolean isblank (string @var{str})
 Checks if @var{str} contains only blank characters; that is, spaces or
 tabs. 
 @end deftypefn
 
-@deftypefn {Built-in Function} number iscntrl (string @var{str})
+@deftypefn {Built-in Function} boolean iscntrl (string @var{str})
 Checks for control characters.
 @end deftypefn
 
-@deftypefn {Built-in Function} number isdigit (string @var{str})
+@deftypefn {Built-in Function} boolean isdigit (string @var{str})
 Checks for digits (0 through 9).
 @end deftypefn
 
-@deftypefn {Built-in Function} number isgraph (string @var{str})
+@deftypefn {Built-in Function} boolean isgraph (string @var{str})
 Checks for any printable characters except spaces.
 @end deftypefn
 
-@deftypefn {Built-in Function} number islower (string @var{str})
+@deftypefn {Built-in Function} boolean islower (string @var{str})
 Checks for lower-case characters.
 @end deftypefn
 
-@deftypefn {Built-in Function} number isprint (string @var{str})
+@deftypefn {Built-in Function} boolean isprint (string @var{str})
 Checks for printable characters including space.
 @end deftypefn
 
-@deftypefn {Built-in Function} number ispunct (string @var{str})
+@deftypefn {Built-in Function} boolean ispunct (string @var{str})
 Checks for any printable characters which are not a spaces or
 alphanumeric characters.
 @end deftypefn
 
-@deftypefn {Built-in Function} number isspace (string @var{str})
+@deftypefn {Built-in Function} boolean isspace (string @var{str})
 Checks for white-space characters, i.e.: space, form-feed (@samp{\f}),
 newline (@samp{\n}), carriage return (@samp{\r}), horizontal tab
 (@samp{\t}), and vertical tab (@samp{\v}).
 @end deftypefn
 
-@deftypefn {Built-in Function} number isupper (string @var{str})
+@deftypefn {Built-in Function} boolean isupper (string @var{str})
 Checks for uppercase letters. 
 @end deftypefn
 
-@deftypefn {Built-in Function} number isxdigit (string @var{str})
+@deftypefn {Built-in Function} boolean isxdigit (string @var{str})
 Checks for hexadecimal digits, i.e. one of @samp{0}, @samp{1},
 @samp{2}, @samp{3}, @samp{4}, @samp{5}, @samp{6}, @samp{7}, @samp{8},
 @samp{9}, @samp{a}, @samp{b}, @samp{c}, @samp{d}, @samp{e}, @samp{f},
 @samp{A}, @samp{B}, @samp{C}, @samp{D}, @samp{E}, @samp{F}.
 @end deftypefn
 
 @node Email processing functions
 @section Email processing functions.
 
 @deftypefn {Built-in Function} number email_map (string @var{email})
   Parses @var{email} and returns a bitmap, consisting of zero or more of
 the following flags:
@@ -708,25 +711,25 @@ the following flags:
 @kwindex EMAIL_ROUTE
 @item EMAIL_ROUTE
 @var{email} has route part.
 @end table
 
 @flindex email.mf
 These constants are declared in the @file{email.mf} module.  The
 function @code{email_map} returns 0 if its argument is not a valid
 email address.
 @end deftypefn
 
 @deftypefn {Library Function} boolean email_valid (string @var{email})
-  Returns @var{True} if @var{email} is a valid email address,
+  Returns @samp{True} (1) if @var{email} is a valid email address,
 consisting of local and domain parts only.  E.g.:
 
 @smallexample
 email_valid("gray@@gnu.org") @result{} 1
 email_valid("gray") @result{} 0
 email_valid('"Sergey Poznyakoff <gray@@gnu.org>') @result{} 0
 @end smallexample
 
   This function is defined in @file{email.mf} (@pxref{Modules}).
 @end deftypefn
 
 @node Envelope modification functions
@@ -1695,61 +1698,61 @@ server.
 @end deftypefn
 
 @node Compatibility Callout functions
 @section Compatibility Callout Functions
   The following functions are wrappers over the callout functions
 described in the previous section.  They are provided for backward
 compativbility.
 
 @flindex poll.mf
   These functions  are defined in the module @file{poll.mf}, which you
 must require prior to using any of them. 
   
-@deftypefn {Library Function} number _pollhost @
+@deftypefn {Library Function} boolean _pollhost @
   (string @var{ip}, string @var{email}, string @var{domain}, @
    string @var{mailfrom})   
   Poll @acronym{SMTP} host @var{ip} for email address @var{email},
 using @var{domain} as @code{EHLO} domain and @var{mailfrom} as
 @code{MAIL FROM}.  Returns 0 or 1 depending on the result of the test.
 In contrast to the @code{strictpoll} function, this function does not use
 cache database and does not fall back to polling @acronym{MX} servers if the
 main poll tempfails.  The function can throw one of the following
 exceptions: @code{e_failure}, @code{e_temp_failure}.
 @end deftypefn
 
-@deftypefn {Library Function} number _pollmx @
+@deftypefn {Library Function} boolean _pollmx @
   (string @var{ip}, string @var{email}, string @var{domain}, @
    string @var{mailfrom})
   Poll @acronym{MX}s of the @var{domain} for email address @var{email}, using
 @var{domain} as @code{EHLO} domain and @var{mailfrom} as @code{MAIL
 FROM} address.  Returns 0 or 1 depending on the result of the test.
 In contrast to the @code{stdpoll} function, @code{_pollmx} does
 not use cache database and does not fall back to polling the @var{ip} 
 if the poll fails.  The function can throw one of the following
 exceptions: @code{e_failure}, @code{e_temp_failure}.
 @end deftypefn
 
-@deftypefn {Library Function} number stdpoll @
+@deftypefn {Library Function} boolean stdpoll @
   (string @var{email}, string @var{domain}, string @var{mailfrom})
   
   Performs standard poll for @var{email}, using @var{domain} as
 @code{EHLO} domain and @var{mailfrom} as @code{MAIL FROM} address.
 Returns 0 or 1 depending on the result of the test.  Can raise one of
 the following exceptions: @code{e_failure}, @code{e_temp_failure}.
 
   In @code{on} statement context, it is synonymous to @code{poll}
 without explicit @var{host}.  @FIXME{more details and references.}
 @end deftypefn
 
-@deftypefn {Library Function} number strictpoll @
+@deftypefn {Library Function} boolean strictpoll @
   (string @var{host}, string @var{email}, @
    string @var{domain}, string @var{mailfrom})
 
   Performs strict poll for @var{email} on host @var{host}.
 See the description of @code{stdpoll} for the detailed information.
 
 In @code{on} context, it is synonymous to @code{poll host @var{host}}.
 @end deftypefn
 
 @cindex multiple sender addresses, using with polling commands.
 @cindex trying several sender addresses
 The @var{mailfrom} argument can be a comma-separated list of email
@@ -1916,25 +1919,25 @@ records) for @var{domain}.
 
   This function does not use the @acronym{DNS} cache.
 @end deftypefn
 
 @deftypefn {Built-in Function} string dns_getname (string @var{ipstr})
   Returns a whitespace-separated list of domain names (@code{PTR}
 records) for the @acronym{IP}v4 address @var{ipstr}.
 
   This function does not use the @acronym{DNS} cache.
 @end deftypefn
 
 @deftypefn {Built-in Function} string getmx (string @var{domain} @
-  [, number @var{ip}])
+  [, boolean @var{ip}])
   Returns a whitespace-separated list of @samp{MX} names (if @var{ip} is not
 given or if it is @code{0}) or @samp{MX} @acronym{IP} addresses (if
 @code{@var{ip}!=0})) for @var{domain}.  Within the returned
 string, items are sorted in order of increasing @samp{MX} priority.
 If @var{domain} has no @samp{MX} records, an empty string is returned.
 If the @acronym{DNS} query fails, @code{getmx} raises an appropriate
 exception.
 
 Examples:
 
 @smallexample
 getmx("mafra.cz") @result{} "smtp1.mafra.cz smtp2.mafra.cz relay.iol.cz"
@@ -2105,24 +2108,48 @@ occurs, the function returns @samp{"0"}.
 @end deftypefn
 
 @deftypefn {Built-in Function} string ptr_validate (string @var{ip})
 Tests whether the DNS reverse-mapping for @var{ip} exists and
 correctly points to a domain name within a particular domain.
 
 First, it obtains all PTR records for @var{ip}.  Then, for each record
 returned, a look up for A records is performed and IP addresses of each
 record are compared against @var{ip}.  The function returns true if a
 matching A record is found.
 @end deftypefn
 
+@deftypefn {Built-in Function} boolean primitive_hasns (string @var{domain})
+Returns @samp{True} if the domain @var{domain} has at least one
+@samp{NS} record. Throws exception if DNS lookup fails.
+@end deftypefn
+
+@deftypefn {Library Function} boolean hasns (string @var{domain})
+Returns @samp{True} if the domain @var{domain} has at least one
+@samp{NS} record. Returns @samp{False} if there are no @samp{NS}
+records or if the DNS lookup fails.
+@end deftypefn
+
+@deftypefn {Built-in Function} string getns (string @var{domain} ; @
+                                 boolean @var{resolve}, boolean @var{sort})
+  Returns a whitespace-separated list of all the @samp{NS} records for
+the domain @var{domain}. Optional parameters @var{resolve} and
+@var{sort} control the formatting. If @var{resolve} is 0 (the default), the
+resulting string will contain IP addresses of the NS servers. If
+@var{resolve} is not 0, hostnames will be returned instead. If
+@var{sort} is 1, the returned items will be sorted.
+
+If the @acronym{DNS} query fails, @code{getns} raises an appropriate
+exception.
+@end deftypefn
+
 @node Geolocation functions
 @section Geolocation functions
 @cindex geolocation
 @cindex GeoIP
 @flindex libGeoIP
 @kwindex WITH_GEOIP
   The @dfn{geolocation functions} allow you to identify the country where
 the given IP address or host name is located.  These functions are
 available only if the @samp{GeoIP} library is installed and
 @command{mailfromd} is compiled with the @samp{GeoIP} support.  The
 @command{m4} macro @samp{WITH_GEOIP} is defined if it is so.
 
@@ -2240,115 +2267,115 @@ declares that all database files in directory @file{/etc/mail} have
 privileges @samp{640} and include null terminator in the key
 length.  @emph{Notice}, the use of @command{m4} quoting characters in
 the example below.  Without them, the sequence @samp{/*} would have
 been taken as the beginning of a comment.
 
 Additionally, for compatibility with previous versions (up to 5.0),
 the terminating null property can be requested via an optional
 argument to the database functions (in description below, marked as
 @var{null}).
 
 @anchor{dbmap}
 @deftypefn {Built-in Function} boolean dbmap (string @var{db}, @
-    string @var{key}, [number @var{null}])
+    string @var{key}, [boolean @var{null}])
   Looks up @var{key} in the @acronym{DBM} file @var{db} and returns
 @code{true} if it is found.
 
   See above for the meaning of @var{null}.
 
 @xref{whitelisting}, for an example of using this function.
 @end deftypefn
 
 @deftypefn {Built-in Function} string dbget (string @var{db}, @
-  string @var{key} [, string @var{default}, number @var{null}])
+  string @var{key} [, string @var{default}, boolean @var{null}])
   Looks up @var{key} in the database @var{db} and returns the value
 associated with it.  If the key is not found returns @var{default}, if
 specified, or empty string otherwise.
 
   See above for the meaning of @var{null}.
 @end deftypefn
 
 @deftypefn {Built-in Function} void dbput (string @var{db}, @
  string @var{key}, string @var{value} [, @
- number @var{null}, number @var{mode} ])
+ boolean @var{null}, number @var{mode} ])
   Inserts in the database a record with the given @var{key} and
 @var{value}.  If a record with the given @var{key} already exists, its
 value is replaced with the supplied one.
 
   See above for the meaning of @var{null}.  Optional @var{mode} allows
 to explicitly specify the file mode for this database.  See also
 @code{#pragma dbprop}, described above.
 @end deftypefn
 
 @deftypefn {Built-in Function} void dbinsert (string @var{db}, @
  string @var{key}, string @var{value} [, @
- number @var{replace}, number @var{null}, number @var{mode} ])
+ boolean @var{replace}, boolean @var{null}, number @var{mode} ])
   This is an improved variant of @code{dbput}, which provides a
 better control on the actions to take if the @var{key} already exists in the
 database.  Namely, if @var{replace} is @samp{True}, the old value is
 replaced with the new one.  Otherwise, the @samp{e_exists} exception
 is thrown.
 @end deftypefn
  
 @deftypefn {Built-in Function} void dbdel (string @var{db}, @
- string @var{key} [, number @var{null}, number @var{mode}])
+ string @var{key} [, boolean @var{null}, number @var{mode}])
   Delete from the database the record with the given @var{key}.  If
 there are no such record, return without signalling error.
 
   If the optional @var{null} argument is given and is not zero, the
 terminating null character will be included in @var{key} length.
 
   Optional @var{mode} allows to explicitly specify the file mode for
 this database.  See also @code{#pragma dbprop}, described above.
 @end deftypefn
 
 @flindex safedb.mf
 The functions above have also the corresponding exception-safe
 interfaces, which return cleanly if the @samp{e_dbfailure} exception
 occurs.  To use these interfaces, request the @file{safedb} module:
 
 @smallexample
 require safedb
 @end smallexample
 
 The exception-safe interfaces are:
 
 @deftypefn {Library Function} string safedbmap (string @var{db}, @
-  string @var{key} [, string @var{default}, number @var{null}])
+  string @var{key} [, string @var{default}, boolean @var{null}])
 
   This is an exception-safe interface to @code{dbmap}.  If a
 database error occurs while attempting to retrieve the record,
 @code{safedbmap} returns @var{default} or @samp{0}, if it is
 not defined.
 @end deftypefn
 
 @deftypefn {Library Function} string safedbget (string @var{db}, @
-  string @var{key} [, string @var{default}, number @var{null}])
+  string @var{key} [, string @var{default}, boolean @var{null}])
 
   This is an exception-safe interface to @code{dbget}.  If a
 database error occurs while attempting to retrieve the record,
 @code{safedbget} returns @var{default} or empty string, if it is
 not defined.
 @end deftypefn
 
 @deftypefn {Library Function} void safedbput (string @var{db}, @
- string @var{key}, string @var{value} [, number @var{null}])
+ string @var{key}, string @var{value} [, boolean @var{null}])
  
   This is an exception-safe interface to @code{dbput}.  If a
 database error occurs while attempting to retrieve the record,
 the function returns without raising exception.
 @end deftypefn
 
 @deftypefn {Library Function} void safedbdel (string @var{db}, @
- string @var{key} [, number @var{null}])
+ string @var{key} [, boolean @var{null}])
  
   This is an exception-safe interface to @code{dbdel}.  If a
 database error occurs while attempting to delete the record,
 the function returns without raising exception.
 @end deftypefn
 
 @anchor{safedb_verbose}
 @vrindex safedb_verbose
 The verbosity of @samp{safedb} interfaces in case of database error is
 controlled by the value of @code{safedb_verbose} variable.  If it is
 @samp{0}, these functions return silently.  This is the default
 behavior.  Otherwise, if @code{safedb_verbose} is not @samp{0}, these
@@ -2413,26 +2440,27 @@ for that format.  If @var{fmtid} does not match any known format,
 @end deftypefn
 
 @cindex getting cache status
 @cindex cache, getting status
 @deftypefn {Built-in Function} number db_get_active (string @var{fmtid})
   Returns the flag indicating whether the cache database @var{fmtid}
 is currently enabled.  If @var{fmtid} does not match any known format,
 @code{db_name} raises the @code{e_not_found} exception.
 @end deftypefn
 
 @cindex disabling cache
 @cindex cache, disabling
-@deftypefn {Built-in Function} void db_set_active (string @var{fmtid}, number @var{enable})
-  Enables the cache database @var{fmtid} if @var{enable} is not null,
+@deftypefn {Built-in Function} void db_set_active (string @var{fmtid}, @
+                                         boolean @var{enable})
+  Enables the cache database @var{fmtid} if @var{enable} is @samp{True},
 or disables it otherwise.  For example, to disable @acronym{DNS}
 caching, do:
 
 @smallexample
 db_set_active("dns", 0)
 @end smallexample
 @end deftypefn
 
 @deftypefn {Built-in Function} boolean relayed (string @var{domain})
 @anchor{relayed}
   Returns @code{true} if the string @var{domain} is found in one of
 relayed domain files (@pxref{conf-base, relayed-domain-file}).  The
@@ -2775,30 +2803,30 @@ do
   write(fd, "prereq nxrrset %domain A\n"
              "update add %domain 86400 A %addr\n\n"
 done
 @end group
 @end smallexample
 
 @noindent
 The function @code{revip} is defined in @ref{revip}.
 
 @node System functions
 @section System functions
 
-@deftypefn {Built-in Function} number access (string @var{pathname}, @
+@deftypefn {Built-in Function} boolean access (string @var{pathname}, @
   number @var{mode})
 Checks whether the calling process can access the file @var{pathname}.
 If @var{pathname} is a symbolic link, it is dereferenced.  The
-function returns 1 (@samp{true}) if the file can be accessed and 0
-(@samp{false}) otherwise@footnote{@emph{Note}, that the return code is
+function returns @samp{True} if the file can be accessed and
+@samp{False} otherwise@footnote{@emph{Note}, that the return code is 
 inverted in respect to the system function @samp{access(2)}.}.
 
 Symbolic values for @var{mode} are provided in module
 @file{status}:
 
 @table @asis
 @kwindex F_OK
 @item F_OK
 Tests for the existence of the file.
 
 @kwindex R_OK
 @item R_OK
@@ -4824,25 +4852,25 @@ module @var{srcname}, or the global debugging level, if called without
 arguments.
 
 For example, if the program was started with
 @option{--debug='all.trace5;@/engine.trace8'} option, then:
 
 @smallexample
 debug_level() @result{} 127
 debug_level("engine") @result{} 1023
 debug_level("db") @result{} 0
 @end smallexample
 @end deftypefn
 
-@deftypefn {Built-in Function} number callout_transcript ([number @var{value}])
+@deftypefn {Built-in Function} boolean callout_transcript ([boolean @var{value}])
 Returns the current state of the callout SMTP transcript.  The result
 is 1 if the transcript is enabled and 0 otherwise.  The transcript is
 normally enabled either by the use of the @option{--transcript}
 command line option (@pxref{SMTP transcript}) or via the
 @samp{transcript} configuration statement (@pxref{conf-server,
 transcript}).
 
 The optional @var{value}, supplies the new state for SMTP transcript.
 Thus, calling @samp{callout_transcript(0)} disables the transcript.
 
 This function can be used in bracket-like fashion to enable transcript
 for a certain part of MFL program, e.g.:
diff --git a/lib/dns.c b/lib/dns.c
index 708803d9..73499e65 100644
--- a/lib/dns.c
+++ b/lib/dns.c
@@ -18,24 +18,25 @@
 # include <config.h>
 #endif
 
 #include <sys/types.h>
 #include <stdlib.h>
 #include <errno.h>
 #include <ctype.h>
 #include <adns.h>
 #include <mailutils/alloc.h>
 #include <mailutils/argcv.h>
 #include <mailutils/io.h>
 #include <mailutils/stream.h>
+#include <mailutils/cstr.h>
 
 #include "libmf.h"
 #include "dns.h"
 
 #define DEFAULT_QFLAGS \
 	(adns_qf_quoteok_cname|adns_qf_cname_loose|adns_qf_quoteok_query)
 
 static mu_debug_handle_t debug_handle;
 static adns_state state;
 
 static void
 dns_log_cb(adns_state ads, void *logfndata, const char *fmt, va_list al)
@@ -709,12 +710,41 @@ resolve_hostname(const char *host, char **pipbuf)
 	case dns_success:
 		mu_debug(debug_handle, MU_DEBUG_TRACE8, 
 			 ("%s resolved to %s", host, ipbuf));
 		*pipbuf = ipbuf;
 		break;
 			
 	default:
 		mu_debug(debug_handle, MU_DEBUG_TRACE8,
 			 ("%s not resolved", host));
 	}
 	return dns_to_mf_status(dstat);
 }
+
+/* Return NS records for the given DOMAIN. */
+dns_status
+ns_lookup(const char *domain, int resolve, struct dns_reply *reply)
+{
+	dns_status status = dns_failure;
+	int rc;
+	adns_answer *ans;
+	int i;
+
+	rc = adns_synchronous(get_state(), domain, adns_r_ns_raw,
+			      DEFAULT_QFLAGS,
+			      &ans);
+	if (rc)
+		return errno_to_dns_status(rc);
+	status = adns_to_dns_status(ans->status);
+	if (status != dns_success)
+		return status;
+	
+	dns_reply_init(reply, dns_reply_str, ans->nrrs);
+	for (i = 0; i < ans->nrrs; i++)
+		reply->data.str[i] = mu_strdup(ans->rrs.str[i]);
+	free(ans);
+
+	if (resolve)
+		status = dns_reply_resolve(reply);
+	
+	return status;
+}
diff --git a/lib/dns.h b/lib/dns.h
index 74b4b168..b0127860 100644
--- a/lib/dns.h
+++ b/lib/dns.h
@@ -61,13 +61,15 @@ dns_status soa_check(const char *name, int ip, struct dns_reply *repl);
 
 dns_status a_lookup(const char *host, struct dns_reply *repl);
 
 dns_status ptr_lookup(struct in_addr ip, struct dns_reply *repl);
 dns_status txt_lookup(const char *name, struct dns_reply *repl);
 
 dns_status ptr_validate(const char *ipstr, struct dns_reply *repl);
 
 dns_status spf_lookup(const char *domain, char **record);
 
 dns_status mx_lookup(const char *host, int resolve, struct dns_reply *repl);
 
+dns_status ns_lookup(const char *host, int resolve, struct dns_reply *reply);
+
 #endif
diff --git a/mflib/dns.mf4 b/mflib/dns.mf4
index e13130b1..e51656d8 100644
--- a/mflib/dns.mf4
+++ b/mflib/dns.mf4
@@ -50,12 +50,25 @@ do
   return primitive_hasmx(str)
 done
 
 func ismx (string domain, string ipstr)
   returns number
 do
   catch *
   do
     return 0
   done
   return primitive_ismx (domain, ipstr)
 done
+
+func hasns (string str)
+  returns number
+do
+  try
+  do
+    return primitive_hasns (str)
+  done
+  catch *
+  do
+    return 0
+  done
+done
diff --git a/src/builtin/dns.bi b/src/builtin/dns.bi
index 3f68f459..0e1e3279 100644
--- a/src/builtin/dns.bi
+++ b/src/builtin/dns.bi
@@ -270,12 +270,96 @@ MF_DEFUN(ptr_validate, NUMBER, STRING s)
 		break;
 	case dns_not_found:
 		res = 0;
 		break;
 	default:
 		MF_THROW(mf_status_to_exception(dns_to_mf_status(rc)),
 			 _("failed to get PTR record for %s"), s);
 	}
 	MF_RETURN(res);
 }
 END
 
+MF_DEFUN(primitive_hasns, NUMBER, STRING dom)
+{
+	struct dns_reply repl;
+	mf_status stat = dns_to_mf_status(ns_lookup(dom, 0, &repl));
+	MF_ASSERT(stat == mf_success || stat == mf_not_found,
+		  mf_status_to_exception(stat),
+		  _("cannot get NS records for %s"),
+		  dom);
+	dns_reply_free(&repl);
+	if (stat == mf_success) {
+		MF_RETURN(1);
+	}
+	MF_RETURN(0);
+}
+END
+
+static int
+cmp_ip(void const *a, void const *b)
+{
+	GACOPYZ_UINT32_T ipa = *(GACOPYZ_UINT32_T const *)a;
+	GACOPYZ_UINT32_T ipb = *(GACOPYZ_UINT32_T const *)b;
+	if (ipa < ipb)
+		return -1;
+	if (ipa > ipb)
+		return 1;
+	return 0;
+}
+
+static int
+cmp_str(void const *a, void const *b)
+{
+	char * const *stra = a;
+	char * const *strb = b;
+	return strcmp(*stra, *strb);
+}
+
+MF_DEFUN(getns, STRING, STRING domain, OPTIONAL, NUMBER resolve, NUMBER sort)
+{
+	mf_status stat;
+	struct dns_reply reply;
+	int i;
+	
+	stat = dns_to_mf_status(ns_lookup(domain, MF_OPTVAL(resolve),
+					  &reply));
+	if (!mf_resolved(stat)) {
+		MF_THROW(mf_status_to_exception(stat),
+			 _("cannot get MX records for %s"), domain);
+	}
+	if (stat == mf_not_found) {
+		MF_RETURN("");
+	}
+
+	MF_OBSTACK_BEGIN();
+	if (reply.type == dns_reply_ip) {
+		if (sort)
+			qsort(reply.data.ip,
+			      reply.count,
+			      sizeof(reply.data.ip[0]),
+			      cmp_ip);
+		for (i = 0; i < reply.count; i++) {
+			struct in_addr s;
+			s.s_addr = reply.data.ip[i];
+			if (i > 0)
+				MF_OBSTACK_1GROW(' ');
+			MF_OBSTACK_GROW(inet_ntoa(s));
+		}
+	} else {
+		if (sort)
+			qsort(reply.data.str,
+			      reply.count,
+			      sizeof(reply.data.str[0]),
+			      cmp_str);
+		for (i = 0; i < reply.count; i++) {
+			if (i > 0)
+				MF_OBSTACK_1GROW(' ');
+			MF_OBSTACK_GROW(reply.data.str[i]);
+		}
+	}
+	MF_OBSTACK_1GROW(0);
+	dns_reply_free(&reply);
+	MF_RETURN_OBSTACK();
+}
+END
+