=head1 NAME

nnrpd - NNTP server for reader clients

=head1 SYNOPSIS

B<nnrpd> [B<-DfnoSt>] [B<-4> I<address>] [B<-6> I<address>] [B<-b> I<address>]
[B<-c> I<configfile>] [B<-i> I<initial>] [B<-I> I<instance>]
[B<-p> I<port>] [B<-P> I<prefork>] [B<-r> I<reason>] [B<-s> I<padding>]

=head1 DESCRIPTION

B<nnrpd> is an NNTP server for newsreaders.  It accepts commands on its
standard input and responds on its standard output.  It is normally
invoked by innd(8) with those descriptors attached to a remote client
connection.  B<nnrpd> also supports running as a standalone daemon.

Unlike innd(8), B<nnrpd> supports all NNTP commands for user-oriented
reading and posting.  B<nnrpd> uses the F<readers.conf> file to control
who is authorized to access the Usenet database.

On exit, B<nnrpd> will report usage statistics through syslog(3).

B<nnrpd> only reads config files (both F<readers.conf> and F<inn.conf>)
when it is spawned.  You can therefore never change the behavior of a
client that's already connected.  If B<nnrpd> is run from B<innd> (the
default) or from inetd(8), xinetd(8), or some equivalent, a new B<nnrpd>
process is spawned for every connection and therefore any changes to
configuration files will be immediately effective for all new
connections.  If you are instead running B<nnrpd> with the B<-D> option,
any configuration changes won't take effect until B<nnrpd> is restarted.

The F<inn.conf> setting I<nnrpdflags> can be used to pass any of the
options below to instances of B<nnrpd> that are spawned directly from
B<innd>.  Many options only make sense when B<-D> is used, so these
options should not be used with I<nnrpdflags>.  See also the discussion
of I<nnrpdflags> in inn.conf(5).

When I<nnrpdloadlimit> in F<inn.conf> is not C<0>, it will also reject
connections if the load average is greater than that value (typically
C<16>).  B<nnrpd> can also prevent high-volume posters from abusing
your resources.  See the discussion of exponential backoff in inn.conf(5).

=head1 OPTIONS

=over 4

=item B<-4> I<address>

The B<-4> parameter instructs B<nnrpd> to bind to the specified IPv4
address when started as a standalone daemon using the B<-D> flag.  This
has to be a valid IPv4 address belonging to an interface of the local
host.  It can also be C<0.0.0.0>, saying to bind to all addresses (this
is the default).

=item B<-6> I<address>

The B<-6> parameter instructs B<nnrpd> to bind to the specified IPv6
address when started as a standalone daemon using the B<-D> flag.  This
has to be a valid IPv6 address belonging to an interface of the local
host.  It can also be C<::0>, saying to bind to all IPv6 addresses.

By default, B<nnrpd> in daemon mode listens to both IPv4 and IPv6
addresses.  With this option, it will listen only to the specified
IPv6 addresses.  On some systems however, a value of C<::0> will cause
it to listen to all IPv4 addresses as well.

=item B<-b> I<address>

Similar to the B<-4> flag.  B<-b> is kept for backwards compatibility.

=item B<-c> I<configfile>

By default, B<nnrpd> reads the F<readers.conf> to determine how to
authenticate connections.  The B<-c> flag specifies an alternate file
for this purpose.  If the file name isn't fully qualified, it is taken
to be relative to I<pathetc> in F<inn.conf>.  (This is useful to have
several instances of B<nnrpd> running on different ports or IP
addresses with different settings.)

=item B<-D>

If specified, this parameter causes B<nnrpd> to operate as a daemon.  That
is, it detaches itself and runs in the background, forking a process for
every connection.  By default, B<nnrpd> listens on the NNTP port (119), so
either innd(8) has to be started on another port or the B<-p> parameter
used.  Note that with this parameter, B<nnrpd> continues running
until killed.  This means that it reads F<inn.conf> once on startup and
never again until restarted.  B<nnrpd> should therefore be restarted if
F<inn.conf> is changed.

When started in daemon mode, B<nnrpd> will write its PID into a file in
the I<pathrun> directory.  The file will be named F<nnrpd.pid> if B<nnrpd>
listens on port 119 (default), or F<nnrpd-%d.pid>, where C<%d> is replaced
with the port that B<nnrpd> is configured to listen on (B<-p> option is
given and its argument is not C<119>).

=item B<-f>

If specified, B<nnrpd> does not detach itself and runs in the
foreground when started as a standalone daemon using the B<-D> flag.

=item B<-i> I<initial>

Specify an initial command to B<nnrpd>.  When used, I<initial> is taken
as if it were the first command received by B<nnrpd>.  After having
responded, B<nnrpd> will close the connection.

=item B<-I> I<instance>

If specified, I<instance> is used as an additional static portion
within message-IDs generated by B<nnrpd>; typically this option would
be used where a cluster of machines exist with the same virtual
hostname and must be disambiguated during posts.

=item B<-n>

The B<-n> flag turns off resolution of IP addresses to names.  If you
only use IP-based restrictions in F<readers.conf> and can handle IP
addresses in your logs, using this flag may result in some additional
speed.

=item B<-o>

The B<-o> flag causes all articles to be spooled instead of sending
them to innd(8).  B<rnews> with the B<-U> flag should be invoked from
cron on a regular basis to take care of these articles.  This flag is
useful if innd(8) is accepting articles and B<nnrpd> is started
standalone or using inetd(8).

=item B<-p> I<port>

The B<-p> parameter instructs B<nnrpd> to listen on I<port> when
started as a standalone daemon using the B<-D> flag.

=item B<-P> I<prefork>

The B<-P> parameter instructs B<nnrpd> to prefork I<prefork> children
awaiting connections when started as a standalone daemon using the
B<-D> flag.

=item B<-r> I<reason>

If the B<-r> flag is used, then B<nnrpd> will reject the incoming
connection giving I<reason> as the text.  This flag is used by innd(8)
when it is paused or throttled.  I<reason> should be encoded in UTF-8.

=item B<-s> I<padding>

As each command is received, B<nnrpd> tries to change its C<argv>
array so that ps(1) will print out the command being executed.  To get
a full display, the B<-s> flag may be used with a long string as its
argument, which will be overwritten when the program changes its
title.

=item B<-S>

If specified, B<nnrpd> will start a negotiation for a TLS session as
soon as connected.  To use this flag, B<--with-openssl> must have been
specified at configure time.  For more information on running B<nnrpd>
with TLS support, see L<TLS SUPPORT>.

=item B<-t>

If the B<-t> flag is used, then all client commands and initial
responses will be traced by reporting them in syslog.  This flag is set
by innd(8) under the control of the ctlinnd(8) C<trace> command, and
is toggled upon receipt of a SIGHUP; see signal(2).

=back

=head1 TLS SUPPORT

If INN is built with B<--with-openssl>, B<nnrpd> will support news reading
over TLS (also known as SSL).  For clients that use the STARTTLS command,
no special configuration is needed beyond creating a TLS/SSL certificate
for the server.  You should do this in exactly the same way that you would
generate a certificate for a web server.

If you're happy with a self-signed certificate (which will generate
warnings with some news reader clients), you can create and install one in
the default path by running C<make cert> after C<make install> when
installing INN, or by running the following commands:

    umask 077
    openssl req -new -x509 -nodes -out <pathetc>/cert.pem \
        -days 366 -keyout <pathetc>/key.pem
    chown news:news <pathetc>/cert.pem
    chmod 640 <pathetc>/cert.pem
    chown news:news <pathetc>/key.pem
    chmod 600 <pathetc>/key.pem

Replace the paths with something appropriate to your INN installation.
This will create a self-signed certificate that will expire in a year.
The B<openssl> program will ask you a variety of questions about your
organization.  Enter the fully qualified domain name of the server as the
name the certificate is for.

You then have to set these F<inn.conf> parameters with the right paths:

    tlscapath:      <pathetc>
    tlscertfile:    <pathetc>/cert.pem
    tlskeyfile:     <pathetc>/key.pem

In case you have a certificate authority root certificate, you can also
set I<tlscafile> to its path.

Most news clients currently do not use the STARTTLS command, however, and
instead expect to connect to a separate port (563) and start a TLS
negotiation immediately.  B<innd> does not, however, know how to listen
for connections to that port and then spawn B<nnrpd> the way that it does
for regular reader connections.  You will therefore need to arrange for
B<nnrpd> to listen on that port through some other means.  This can be
done with the B<-D> flag along with C<-p 563> and put into your init scripts:

    su news -c '<pathbin>/nnrpd -D -p 563 -S'

but the easiest way is probably to add a line like:

    nntps stream tcp nowait news <pathbin>/nnrpd nnrpd -S

to F</etc/inetd.conf> or the equivalent on your system and let B<inetd>
run B<nnrpd>.  (Change the path to B<nnrpd> to match your installation.)
You may need to replace C<nntps> with C<563> if C<nntps> isn't
defined in F</etc/services> on your system.

=head1 PROTOCOL DIFFERENCES

B<nnrpd> implements the NNTP commands defined in S<RFC 3977> (NNTP),
S<RFC 4642> (TLS/NNTP) and S<RFC 4643> (NNTP authentication) with the
following differences:

=over 4

=item 1.

Besides the keywords defined in S<RFC 3977> (ACTIVE, ACTIVE.TIMES,
DISTRIB.PATS, HEADERS, NEWSGROUPS and OVERVIEW.FMT), the LIST command
may be followed by the optional keywords COUNTS, DISTRIBUTIONS, MODERATORS,
MOTD and SUBSCRIPTIONS to respectively get an improved version of the
ACTIVE variant with the number of articles in every newsgroup, a list
of valid distributions, the moderators list, the message of the day
information for readers, and a list of recommended group subscriptions.

=item 2.

The XGTITLE [I<wildmat>] command is provided.  This extension is used by
ANU-News and documented in S<RFC 2980>.  It returns a C<282> reply code,
followed by a one-line description of all newsgroups that match the
pattern.  The default is the current group.

Note that LIST NEWSGROUPS should be used instead of XGTITLE.

=item 3.

The XHDR I<header> [I<message-ID>|I<range>] command is implemented.  It
returns a C<221> reply code, followed by specific headers for the
specified range; the default is to return the data for the current article.
See S<RFC 2980>.

Note that HDR should be used instead of XHDR.

=item 4.

The XOVER [I<range>] command is provided.  It returns a C<224> reply code,
followed by the overview data for the specified range; the default is to
return the data for the current article.  See S<RFC 2980>.

Note that OVER should be used instead of XOVER.

=item 5.

A new command, XPAT I<header> I<message-ID>|I<range> I<pattern>
[I<pattern> ...], is provided.  The first argument is the case-insensitive
name of the header to be searched.  The second argument is either an article
range or a single message-ID, as specified in S<RFC 2980>.  The third
argument is a uwildmat(3)-style pattern; if there are additional arguments,
they are joined together separated by a single space to form the complete
pattern.  This command is similar to the XHDR command.  It returns a C<221>
response code, followed by the text response of all article numbers that
match the pattern.

=item 6.

A newsgroup name is case-sensitive for B<nnrpd>.

=item 7.

If IHAVE has been advertised, it will not necessarily be advertised for
the entire session (contrary to section 3.4.1 of S<RFC 3977>).  B<nnrpd>
only advertises the IHAVE capability when it is really available.

=item 8.

B<nnrpd> allows a wider syntax for wildmats and ranges (especially C<->
and C<-I<article-number>>).

=back

=head1 HISTORY

Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews.  Overview
support added by Rob Robertston <rob@violet.berkeley.edu> and Rich in
January, 1993.  Exponential backoff (for posting) added by Dave Hayes in
Febuary 1998.

$Id: nnrpd.pod 8956 2010-02-08 20:50:47Z iulius $

=head1 SEE ALSO

ctlinnd(8), innd(8), inn.conf(5), readers.conf(5), signal(2), uwildmat(3).

=cut
