Provided by: xinetd_2.3.14-7ubuntu3_i386 bug

NAME

       xinetd.conf - Extended Internet Services Daemon configuration file

DESCRIPTION

       xinetd.conf  is  the  configuration  file  that determines the services
       provided by xinetd.  Any line whose first non-white-space character  is
       a ’#’ is considered a comment line. Empty lines are ignored.

       The file contains entries of the form:

              service <service_name>
              {
                     <attribute> <assign_op> <value> <value> ...
                     ...
              }

       The assignment operator, assign_op, can be one of ’=,+=,-=.  The
       majority of attributes support only  the  simple  assignment  operator,
       ’=.   Attributes whose value is a set of values support all assignment
       operators.  For such attributes, ’+=’ means adding a value to  the  set
       and  ’-=’  means  removing  a  value  from  the  set.   A list of these
       attributes will be given after all the attributes are described.

       Each entry defines a  service  identified  by  the  service_name.   The
       following is a list of available attributes:

       id               This attribute is used to uniquely identify a service.
                        This is useful because there exist services  that  can
                        use  different protocols and need to be described with
                        different  entries  in  the  configuration  file.   By
                        default,  the  service  id  is the same as the service
                        name.

       type             Any combination of the following values may be used:

                        RPC         if this is an RPC service

                        INTERNAL    if this is a service provided by xinetd.

                        TCPMUX/TCPMUXPLUS
                                    if this is a service that will be  started
                                    according  to the RFC 1078 protocol on the
                                    TCPMUX well-known port.  See  the  section
                                    describing TCPMUX services below.

                        UNLISTED    if  this  is  a  service  not  listed in a
                                    standard system file  (like  /etc/rpc  for
                                    RPC services, or /etc/services for non-RPC
                                    services).

       flags            Any combination of the following flags may be used:

                        INTERCEPT   Intercept packets or accepted  connections
                                    in  order  to  verify that they are coming
                                    from  acceptable  locations  (internal  or
                                    multi-threaded    services    cannot    be
                                    intercepted).

                        NORETRY     Avoid  retry  attempts  in  case  of  fork
                                    failure.

                        IDONLY      Accept  connections  only  when the remote
                                    end identifies the remote user  (i.e.  the
                                    remote  host  must  run  an identification
                                    server).   This  flag  applies   only   to
                                    connection-based  services.   This flag is
                                    ineffective if the USERID  log  option  is
                                    not used.

                        NAMEINARGS  This  will  cause  the  first  argument in
                                    "server_args" to be argv[0] when executing
                                    the  server,  as  specified  in  "server".
                                    This allows you to  use  tcpd  by  putting
                                    tcpd  in  "server"  and  the  name  of the
                                    server in  "server_args"  like  in  normal
                                    inetd.

                        NODELAY     If  the  service  is a tcp service and the
                                    NODELAY flag is set, then the  TCP_NODELAY
                                    flag  will  be  set on the socket.  If the
                                    service is not a tcp service, this  option
                                    has no effect.

                        KEEPALIVE   If  the  service  is a tcp service and the
                                    KEEPALIVE   flag   is   set,   then    the
                                    SO_KEEPALIVE  socket  flag  will be set on
                                    the socket.  If the service is not  a  tcp
                                    service, this option has no effect.

                        NOLIBWRAP   This  disables  internal  calling  of  the
                                    tcpwrap library to determine access to the
                                    service.   This  may be needed in order to
                                    use libwrap functionality not available to
                                    long-running  processes such as xinetd; in
                                    this case, the tcpd program can be  called
                                    explicitly (see also the NAMEINARGS flag).

                        SENSOR      This replaces the service  with  a  sensor
                                    that  detects  accesses  to  the specified
                                    port. NOTE: It  will  NOT  detect  stealth
                                    scans.  This  flag  should be used only on
                                    services that you  know  you  don’t  need.
                                    When  an  access is made to this service’s
                                    port, the IP Address is added to a  global
                                    no_access list. This causes all subsequent
                                    accesses from the originating  IP  address
                                    to  be  denied  access until the deny_time
                                    setting expires. The amount of time  spent
                                    on   this  list  is  configurable  as  the
                                    deny_time attribute. The SENSOR flag  will
                                    also  cause  xinetd to consider the server
                                    attribute to be INTERNAL no matter what is
                                    typed  on the same line. Another important
                                    thing  to  remember   is   that   if   the
                                    socket_type  is  set  to  stream, then the
                                    wait attribute should be set to no.

                        IPv4        Sets the service to  be  an  IPv4  service
                                    (AF_INET).

                        IPv6        Sets  the  service  to  be an IPv6 service
                                    (AF_INET6), if IPv6 is  available  on  the
                                    system.

                        REUSE       The   REUSE   flag   is  deprecated.   All
                                    services  now  implicitly  use  the  REUSE
                                    flag.

       disable          This  is  boolean  "yes" or "no".  This will result in
                        the service being disabled and not starting.  See  the
                        DISABLE flag description.

       socket_type      Possible values for this attribute include:

                        stream      stream-based service

                        dgram       datagram-based service

                        raw         service that requires direct access to IP

                        seqpacket   service  that requires reliable sequential
                                    datagram transmission

       protocol         determines  the  protocol  that  is  employed  by  the
                        service.   The  protocol must exist in /etc/protocols.
                        If this attribute is not defined, the default protocol
                        employed by the service will be used.

       wait             This  attribute  determines  if the service is single-
                        threaded or multi-threaded and whether or  not  xinetd
                        accepts  the  connection or the server program accepts
                        the connection. If its value is yes,  the  service  is
                        single-threaded; this means that xinetd will start the
                        server and then it will stop handling requests for the
                        service  until  the  server  dies  and that the server
                        software will accept the connection. If the  attribute
                        value  is no, the service is multi-threaded and xinetd
                        will keep handling new  service  requests  and  xinetd
                        will  accept  the  connection. It should be noted that
                        udp/dgram services normally expect the value to be yes
                        since udp is not connection oriented, while tcp/stream
                        servers normally expect the value to be no.

       user             determines the uid for the server  process.  The  user
                        attribute  can  either be numeric or a name. If a name
                        is given (recommended),  the user name must  exist  in
                        /etc/passwd.   This  attribute  is  ineffective if the
                        effective user ID of xinetd is not super-user.

       group            determines the gid for the server process.  The  group
                        attribute  can  either be numeric or a name. If a name
                        is given (recommended), the group name must  exist  in
                        /etc/group.  If a group is not specified, the group of
                        user will be used (from /etc/passwd).  This  attribute
                        is  ineffective  if the effective user ID of xinetd is
                        not super-user and if the groups attribute is not  set
                        to ’yes’.

       instances        determines   the   number   of  servers  that  can  be
                        simultaneously active for a service (the default is no
                        limit).  The  value  of this attribute can be either a
                        number or UNLIMITED  which  means  that  there  is  no
                        limit.

       nice             determines   the  server  priority.  Its  value  is  a
                        (possibly negative) number;  check  nice(3)  for  more
                        information.

       server           determines the program to execute for this service.

       server_args      determines  the  arguments  passed  to  the server. In
                        contrast to inetd,  the  server  name  should  not  be
                        included in server_args.

       libwrap          overrides  the  service  name passed to libwrap (which
                        defaults to the server  name,  the  first  server_args
                        component   with   NAMEINARGS,  the  id  for  internal
                        services  and  the   service   name   for   redirected
                        services).  This attribute is only valid if xinetd has
                        been configured with the libwrap option.

       only_from        determines the remote hosts to  which  the  particular
                        service  is  available.   Its  value  is  a list of IP
                        addresses which can be specified in any combination of
                        the following ways:

                        a)   a  numeric address in the form of %d.%d.%d.%d. If
                             the rightmost components are 0, they are  treated
                             as  wildcards  (for example, 128.138.12.0 matches
                             all hosts on  the  128.138.12  subnet).   0.0.0.0
                             matches  all  Internet addresses.  IPv6 hosts may
                             be specified in the form of abcd:ef01::2345:6789.
                             The  rightmost  rule  for IPv4 addresses does not
                             apply to IPv6 addresses.

                        b)   a   factorized   address   in   the    form    of
                             %d.%d.%d.{%d,%d,...}.  There is no need for all 4
                             components (i.e. %d.%d.{%d,%d,...%d} is also ok).
                             However,  the  factorized part must be at the end
                             of the address.  This form does not work for IPv6
                             hosts.

                        c)   a  network  name  (from /etc/networks). This form
                             does not work for IPv6 hosts.

                        d)   a host  name.   When  a  connection  is  made  to
                             xinetd,  a  reverse  lookup is performed, and the
                             canonical  name  returned  is  compared  to   the
                             specified  host  name.   You  may also use domain
                             names in the form of .domain.com.  If the reverse
                             lookup  of the client’s IP is within .domain.com,
                             a match occurs.

                        e)   an  ip  address/netmask  range  in  the  form  of
                             1.2.3.4/32.   IPv6  address/netmask ranges in the
                             form of 1234::/46 are also valid.

                        Specifying this attribute without a  value  makes  the
                        service available to nobody.

       no_access        determines  the  remote  hosts to which the particular
                        service is unavailable. Its value can be specified  in
                        the  same way as the value of the only_from attribute.
                        These two attributes  determine  the  location  access
                        control  enforced  by  xinetd.  If  none of the two is
                        specified for a service, the service is  available  to
                        anyone.  If  both are specified for a service, the one
                        that is the better match for the address of the remote
                        host  determines  if  the service is available to that
                        host (for example,  if  the  only_from  list  contains
                        128.138.209.0   and   the   no_access   list  contains
                        128.138.209.10  then  the  host   with   the   address
                        128.138.209.10 can not access the service).

       access_times     determines  the  time  intervals  when  the service is
                        available. An interval has the form  hour:min-hour:min
                        (connections  will  be  accepted  at  the bounds of an
                        interval). Hours can range from 0 to  23  and  minutes
                        from 0 to 59.

       log_type         determines where the service log output is sent. There
                        are two formats:

                        SYSLOG  syslog_facility [syslog_level]
                               The  log  output  is  sent  to  syslog  at  the
                               specified  facility.  Possible  facility  names
                               include: daemon, auth,  authpriv,  user,  mail,
                               lpr,  news, uucp, ftp local0-7.  Possible level
                               names  include:  emerg,   alert,   crit,   err,
                               warning,  notice,  info,  debug.  If a level is
                               not present, the messages will be  recorded  at
                               the info level.

                        FILE  file [soft_limit [hard_limit]]
                               The  log  output is appended to file which will
                               be created if it does not exist. Two limits  on
                               the  size  of  the  log  file can be optionally
                               specified.  The first  limit  is  a  soft  one;
                               xinetd  will  log a message the first time this
                               limit is exceeded (if xinetd  logs  to  syslog,
                               the  message will be sent at the alert priority
                               level).  The second  limit  is  a  hard  limit;
                               xinetd  will  stop  logging  for  the  affected
                               service (if the log file is a common log  file,
                               then more than one service may be affected) and
                               will log a message about this (if  xinetd  logs
                               to  syslog,  the  message  will  be sent at the
                               alert priority level).  If a hard limit is  not
                               specified,   it  defaults  to  the  soft  limit
                               increased by 1% but  the  extra  size  must  be
                               within   the   parameters   LOG_EXTRA_MIN   and
                               LOG_EXTRA_MAX  which  default  to  5K  and  20K
                               respectively  (these  constants  are defined in
                               xconfig.h).

       log_on_success   determines what information is logged when a server is
                        started  and when that server exits (the service id is
                        always included in the log entry).  Any combination of
                        the following values may be specified:

                        PID         logs the server process id (if the service
                                    is implemented by xinetd  without  forking
                                    another process the logged process id will
                                    be 0)

                        HOST        logs the remote host address

                        USERID      logs the user id of the remote user  using
                                    the   RFC  1413  identification  protocol.
                                    This option is available only  for  multi-
                                    threaded stream services.

                        EXIT        logs  the  fact that a server exited along
                                    with the exit status  or  the  termination
                                    signal  (the  process id is also logged if
                                    the PID option is used)

                        DURATION    logs the duration of a service session

                        TRAFFIC     logs the total bytes  in  and  out  for  a
                                    redirected service.

       log_on_failure   determines  what  information  is logged when a server
                        cannot  be  started  (either  because  of  a  lack  of
                        resources  or because of access control restrictions).
                        The service id is always included  in  the  log  entry
                        along with the reason for failure.  Any combination of
                        the following values may be specified:

                        HOST        logs the remote host address.

                        USERID      logs the user id of the remote user  using
                                    the   RFC  1413  identification  protocol.
                                    This option is available only  for  multi-
                                    threaded stream services.

                        ATTEMPT     logs  the  fact  that a failed attempt was
                                    made  (this  option  is  implied  by   all
                                    others).

       rpc_version      determines  the  RPC  version  for  a RPC service. The
                        version can be a single number or a range in the  form
                        number-number.

       rpc_number       determines  the  number  for  an  UNLISTED RPC service
                        (this attribute is  ignored  if  the  service  is  not
                        unlisted).

       env              The  value  of  this attribute is a list of strings of
                        the form ’name=value’.  These strings will be added to
                        the  environment  before  starting a server (therefore
                        the  server’s  environment   will   include   xinetd’s
                        environment plus the specified strings).

       passenv          The  value  of this attribute is a list of environment
                        variables  from  xinetd’s  environment  that  will  be
                        passed  to  the server.  An empty list implies passing
                        no variables to the server except for those explicitly
                        defined using the env attribute.  (notice that you can
                        use  this  attribute  in  conjunction  with  the   env
                        attribute  to specify exactly what environment will be
                        passed to the server).

       port             determines the service  port.  If  this  attribute  is
                        specified  for  a  service listed in /etc/services, it
                        must be equal to the port number listed in that  file.

       redirect         Allows a tcp service to be redirected to another host.
                        When xinetd receives a tcp connection on this port  it
                        spawns  a process that establishes a connection to the
                        host and port number specified, and forwards all  data
                        between  the  two  hosts.   This option is useful when
                        your internal machines are not visible to the  outside
                        world.   Syntax  is:  redirect  = (ip address) (port).
                        You can also use a hostname instead of the IP  address
                        in  this field.  The hostname lookup is performed only
                        once, when xinetd is started, and the first IP address
                        returned  is  the  one  that  is  used until xinetd is
                        restarted.  The "server"  attribute  is  not  required
                        when  this  option  is  specified.   If  the  "server"
                        attribute is specified, this attribute takes priority.

       bind             Allows  a  service to be bound to a specific interface
                        on the machine.  This means  you  can  have  a  telnet
                        server  listening  on  a local, secured interface, and
                        not on the external interface.  Or  one  port  on  one
                        interface  can  do something, while the same port on a
                        different  interface  can  do   something   completely
                        different.   Syntax: bind = (ip address of interface).

       interface        Synonym for bind.

       banner           Takes the name of a file to be splatted at the  remote
                        host when a connection to that service is established.
                        This banner is printed regardless of  access  control.
                        It  should  *always*  be printed when a connection has
                        been made.  xinetd outputs the file as-is, so you must
                        ensure   the  file  is  correctly  formatted  for  the
                        service’s protocol.  In  paticular,  if  the  protocol
                        requires  CR-LF  pairs  for line termination, you must
                        supply them.

       banner_success   Takes the name of a file to be splatted at the  remote
                        host  when  a  connection  to that service is granted.
                        This banner is printed as soon as  access  is  granted
                        for  the  service.   xinetd outputs the file as-is, so
                        you must ensure the file is  correctly  formatted  for
                        the service’s protocol.  In paticular, if the protocol
                        requires CR-LF pairs for line  termination,  you  must
                        supply them.

       banner_fail      Takes  the name of a file to be splatted at the remote
                        host when a connection  to  that  service  is  denied.
                        This  banner  is  printed  immediately  upon denial of
                        access.  This is useful for informing your users  that
                        they  are  doing  something  bad and they shouldn’t be
                        doing it anymore.  xinetd outputs the file  as-is,  so
                        you  must  ensure  the file is correctly formatted for
                        the service’s protocol.  In paticular, if the protocol
                        requires  CR-LF  pairs  for line termination, you must
                        supply them.

       per_source       Takes an integer or "UNLIMITED" as an argument.   This
                        specifies  the  maximum  instances of this service per
                        source IP address.  This can also be specified in  the
                        defaults section.

       cps              Limits  the  rate  of incoming connections.  Takes two
                        arguments.   The  first  argument  is  the  number  of
                        connections  per  second  to  handle.   If the rate of
                        incoming connections is higher than this, the  service
                        will  be temporarily disabled.  The second argument is
                        the number of seconds to wait before  re-enabling  the
                        service  after  it has been disabled.  The default for
                        this  setting  is  50  incoming  connections  and  the
                        interval is 10 seconds.

       max_load         Takes  a floating point value as the load at which the
                        service will stop accepting connections.  For example:
                        2 or 2.5.  The service will stop accepting connections
                        at this load.  This is the one  minute  load  average.
                        This  is  an  OS dependent feature, and currently only
                        Linux, Solaris, and FreeBSD are  supported  for  this.
                        This   feature   is   only  avaliable  if  xinetd  was
                        configured with the -with-loadavg option.

       groups           Takes either "yes" or "no".  If the  groups  attribute
                        is  set  to  "yes",  then  the server is executed with
                        access to the groups that the server’s  effective  UID
                        has  access to.  Alternatively, if the group attribute
                        is set, the server is  executed  with  access  to  the
                        groups  specified.   If the groups attribute is set to
                        "no", then  the  server  runs  with  no  supplementary
                        groups.   This attribute must be set to "yes" for many
                        BSD  systems.   This  attribute  can  be  set  in  the
                        defaults section as well.

       mdns             Takes  either  "yes" or "no".  On systems that support
                        mdns registration of services (currently only  Mac  OS
                        X),  this  will  enable or disable registration of the
                        service.  This defaults to "yes".

       umask            Sets the inherited umask for the service.  Expects  an
                        octal value.  This option may be set in the "defaults"
                        section to set a umask for all services.  xinetd  sets
                        its  own  umask  to  the previous umask OR’d with 022.
                        This is the umask that will be inherited by all  child
                        processes if the umask option is not used.

       enabled          Takes  a  list  of  service ID’s to enable.  This will
                        enable only the services listed as arguments  to  this
                        attribute;  the  rest will be disabled.  If you have 2
                        ftp services, you will need to list both of their ID’s
                        and  not  just  ftp. (ftp is the service name, not the
                        ID. It might accidentally be the ID,  but  you  better
                        check.)  Note that the service "disable" attribute and
                        "DISABLE"  flag  can  prevent  a  service  from  being
                        enabled despite being listed in this attribute.

       include          Takes   a   filename   in   the   form   of   "include
                        /etc/xinetd/service".  The file is then  parsed  as  a
                        new  configuration  file.  It is not the same thing as
                        pasting the file into xinetd.conf  where  the  include
                        directive  is given.  The included file must be in the
                        same form as xinetd.conf.  This may not  be  specified
                        from within a service.  It must be specified outside a
                        service declaration.

       includedir       Takes a directory name  in  the  form  of  "includedir
                        /etc/xinetd.d".   Every  file  inside  that directory,
                        excluding files with names containing a dot  (’.’)  or
                        ending  with  a  tilde (’~’), will be parsed as xinetd
                        configuration files.  The  files  will  be  parsed  in
                        alphabetical  order  according  to  the C locale. This
                        allows you to specify services one per file  within  a
                        directory.    The  includedir  directive  may  not  be
                        specified from within a service declaration.

       rlimit_as        Sets the Address Space resource limit for the service.
                        One  parameter is required, which is either a positive
                        integer representing the number of bytes  to  set  the
                        limit   to   (K   or   M   may   be  used  to  specify
                        kilobytes/megabytes) or "UNLIMITED".  Due to  the  way
                        Linux’s  libc malloc is implemented, it is more useful
                        to set this limit  than  rlimit_data,  rlimit_rss  and
                        rlimit_stack.  This resource limit is only implemented
                        on Linux systems.

       rlimit_cpu       Sets the  maximum  number  of  CPU  seconds  that  the
                        service  may use.  One parameter is required, which is
                        either a positive integer representing the  number  of
                        CPU seconds limit to, or "UNLIMITED".

       rlimit_data      Sets  the  maximum  data  size  resource limit for the
                        service.  One parameter is required, which is either a
                        positive  integer  representing the number of bytes or
                        "UNLIMITED".

       rlimit_rss       Sets the maximum  resident  set  size  limit  for  the
                        service.  Setting this value low will make the process
                        a likely candidate  for  swapping  out  to  disk  when
                        memory  is  low.   One parameter is required, which is
                        either a positive integer representing the  number  of
                        bytes or "UNLIMITED".

       rlimit_stack     Set the maximum stack size limit for the service.  One
                        parameter is required,  which  is  either  a  positive
                        integer   representing   the   number   of   bytes  or
                        "UNLIMITED".

       deny_time        Sets the time span that access to all services on  all
                        IP  addresses  are denied to someone that sets off the
                        SENSOR. The unit of time is in minutes.  Valid options
                        are:  FOREVER,  NEVER,  and  a  numeric value. FOREVER
                        causes the IP address not to be purged until xinetd is
                        restarted.  NEVER  has  the effect of just logging the
                        offending IP address. A typical time value would be 60
                        minutes.  This  should  stop  most  DOS  attacks while
                        allowing IP addresses that come  from  a  pool  to  be
                        recycled  for legitimate purposes. This option must be
                        used in conjunction with the SENSOR flag.

       You don’t need to specify all of the above attributes for each service.
       The necessary attributes for a service are:

              socket_type
              user              (non-internal services only)
              server            (non-internal services only)
              wait
              protocol          (RPC and unlisted services only)
              rpc_version       (RPC services only)
              rpc_number        (unlisted RPC services only)
              port              (unlisted non-RPC services only)

       The following attributes support all assignment operators:

              only_from
              no_access
              log_on_success
              log_on_failure
              passenv
              env               (does not support the ’-=’ operator)

       These  attributes  can  also  appear more than once in a service entry.
       The remaining attributes support only the ’=’ operator and  can  appear
       at most once in a service entry.

       The  configuration  file  may also contain a single defaults entry that
       has the form

              defaults
              {
                     <attribute> = <value> <value> ...
                     ...
              }

       This entry provides default attribute values for service  entries  that
       don’t specify those attributes. Possible default attributes:

              log_type          (cumulative effect)
              bind
              per_source
              umask
              log_on_success    (cumulative effect)
              log_on_failure    (cumulative effect)
              only_from         (cumulative effect)
              no_access         (cumulative effect)
              passenv           (cumulative effect)
              instances
              disabled          (cumulative effect)
              enabled           (cumulative effect)
              banner
              banner_success
              banner_fail
              per_source
              groups
              cps
              max_load

              Attributes  with  a  cumulative  effect  can be specified
              multiple times
              with  the values specified each time accumulating (i.e. ’=’ does
              the same thing as ’+=’).  With the exception  of  disabled  they
              all have the same meaning as if they were specified in a service
              entry.  disabled determines services that are disabled  even  if
              they  have  entries  in  the configuration file. This allows for
              quick reconfiguration by specifying disabled services  with  the
              disabled attribute instead of commenting them out.  The value of
              this attribute  is  a  list  of  space  separated  service  ids.
              enabled  has  the  same  properties as disabled.  The difference
              being that enabled is  a  list  of  which  services  are  to  be
              enabled.   If  enabled is specified, only the services specified
              are available.  If enabled is not specified,  all  services  are
              assumed to be enabled, except those listed in disabled.

INTERNAL SERVICES

       xinetd  provides  the  following  services  internally (both stream and
       datagram based): echo, time,  daytime,  chargen,  and  discard.   These
       services  are  under the same access restrictions as all other services
       except for the ones that don’t require xinetd to fork  another  process
       for  them.  Those  ones  (time,  daytime,  and the datagram-based echo,
       chargen, and discard) have no limitation in the number of instances.

TCPMUX Services

       xinetd supports  TCPMUX  services  that  conform  to  RFC  1078.  These
       services  may  not have a well-known port associated with them, and can
       be accessed via the TCPMUX well-known port.

       For each service that is to be accessed via TCPMUX, a service entry  in
       /etc/xinetd.conf  or in a configuration file in an includedir directory
       must exist.

       The service_name field (as defined above for each service in any xinetd
       configuration  file)  must  be  identical  to the string that is passed
       (according to RFC 1078 protocol) to  xinetd  when  the  remote  service
       requestor  first  makes  the  connection on the TCPMUX well-known port.
       Private protocols should use a service name that has a high probability
       of  being unique. One way is to prepend the service name with some form
       of organization ID.

       The type field can be either TCPMUX  or  TCPMUXPLUS.  If  the  type  is
       TCPMUXPLUS,  xinetd  will  handle  the  initial  protocol handshake (as
       defined in RFC 1078) with the calling  process  before  initiating  the
       service.  If  the  type  is  TCPMUX,  the  server  that  is  started is
       responsible for performing the handshake.

       The type field should also include  UNLISTED  if  the  service  is  not
       listed  in  a  standard system file (like /etc/rpc for RPC services, or
       /etc/services for non-RPC services).

       The socket_type for these services must be  stream,  and  the  protocol
       must be tcp.

       Following is a sample TCPMUX service configuration:

              service myorg_server
              {
                     disable             = no
                     type                = TCPMUX
                     socket_type         = stream
                     protocol            = tcp
                     wait                = no
                     user                = root
                     server              = /usr/etc/my_server_exec
              }

       Besides  a  service entry for each service that can be accessed via the
       TCPMUX well-known port, a service entry for TCPMUX itself must also  be
       included in the xinetd configuration. Consider the following sample:

              service tcpmux
              {
                     type                = INTERNAL
                     id                  = tcpmux
                     socket_type         = stream
                     protocol            = tcp
                     user                = root
                     wait                = no
              }

NOTES

       1.  The   following   service   attributes   cannot   be   changed   on
           reconfiguration: socket_type, wait, protocol, type.

       2.  When the attributes only_from and no_access are not specified for a
           service  (either  directly  or  via  defaults) the address check is
           considered successful (i.e. access will not be denied).

       3.  The address check is based on the IP address of the remote host and
           not  on  its domain address. We do this so that we can avoid remote
           name lookups which may take a long time (since  xinetd  is  single-
           threaded,  a name lookup will prevent the daemon from accepting any
           other requests until the lookup is resolved).   The  down  side  of
           this  scheme  is  that  if the IP address of a remote host changes,
           then  access  to  that  host  may  be  denied   until   xinetd   is
           reconfigured.  Whether access is actually denied or not will depend
           on whether the new host IP address is among those  allowed  access.
           For  example,  if  the IP address of a host changes from 1.2.3.4 to
           1.2.3.5 and only_from is specified as 1.2.3.0 then access will  not
           be denied.

       4.  If  the  USERID  log option is specified and the remote host either
           does not run an identification server or the server  sends  back  a
           bad reply, access will not be denied unless the IDONLY service flag
           is used.

       5.  Interception works by forking a process  which  acts  as  a  filter
           between  the  remote  host(s) and the local server.  This obviously
           has a performance impact so it is up to you to make the  compromise
           between  security  and performance for each service.  The following
           tables show the overhead of interception.  The  first  table  shows
           the  time  overhead-per-datagram  for  a  UDP-based  service  using
           various datagram sizes.  For TCP-based  services  we  measured  the
           bandwidth reduction because of interception while sending a certain
           amount of data from client to server (the time overhead should  the
           same  as  for UDP-based services but it is "paid" only by the first
           packet of a continuous data transmission).  The amount of  data  is
           given  in  the table as system_callsxdata_sent_per_call, i.e.  each
           send(2) system  call  transferred  so  many  bytes  of  data.   The
           bandwidth  reduction is given in terms of bytes per second and as a
           percentage of the bandwidth when  interception  is  not  performed.
           All measurements were done on a SparcStation IPC running SunOS 4.1.

                  Datagram size (bytes)    Latency (msec)
                  ---------------------    --------------
                  64                       1.19
                  256                      1.51
                  1024                     1.51
                  4096                     3.58

                  Bytes sent               Bandwidth reduction
                  ----------               -------------------
                  10000x64                 941 (1.2%)
                  10000x256                4,231 (1.8%)
                  10000x1024               319,300 (39.5%)
                  10000x4096               824,461 (62.1%)

EXAMPLE

              #
              # Sample configuration file for xinetd
              #

              defaults
              {
                     log_type            = FILE /var/log/servicelog
                     log_on_success      = PID
                     log_on_failure      = HOST
                     only_from           = 128.138.193.0 128.138.204.0
                     only_from           = 128.138.252.1
                     instances           = 10
                     disabled            = rstatd
              }

              #
              # Note 1: the protocol attribute is not required
              # Note 2: the instances attribute overrides the default
              #
              service login
              {
                     socket_type         = stream
                     protocol            = tcp
                     wait                = no
                     user                = root
                     server              = /usr/etc/in.rlogind
                     instances           = UNLIMITED
              }

              #
              # Note 1: the instances attribute overrides the default
              # Note 2: the log_on_success flags are augmented
              #
              service shell
              {
                     socket_type         = stream
                     wait                = no
                     user                = root
                     instances           = UNLIMITED
                     server              = /usr/etc/in.rshd
                     log_on_success      += HOST
              }

              service ftp
              {
                     socket_type         = stream
                     wait                = no
                     nice                = 10
                     user                = root
                     server              = /usr/etc/in.ftpd
                     server_args         = -l
                     instances           = 4
                     log_on_success      += DURATION HOST USERID
                     access_times        = 2:00-9:00 12:00-24:00
              }

              # Limit telnet sessions to 8 Mbytes of memory and a total
              # 20 CPU seconds for child processes.
              service telnet
              {
                     socket_type         = stream
                     wait                = no
                     nice                = 10
                     user                = root
                     server              = /usr/etc/in.telnetd
                     rlimit_as           = 8M
                     rlimit_cpu          = 20
              }

              #
              # This entry and the next one specify internal services. Since
              # this is the same service using a different socket type, the
              # id attribute is used to uniquely identify each entry
              #
              service echo
              {
                     id                  = echo-stream
                     type                = INTERNAL
                     socket_type         = stream
                     user                = root
                     wait                = no
              }

              service echo
              {
                     id                  = echo-dgram
                     type                = INTERNAL
                     socket_type         = dgram
                     user                = root
                     wait                = no
              }

              #
              # Sample RPC service
              #
              service rstatd
              {
                     type                = RPC
                     socket_type         = dgram
                     protocol            = udp
                     server              = /usr/etc/rpc.rstatd
                     wait                = yes
                     user                = root
                     rpc_version         = 2-4
                     env                 = LD_LIBRARY_PATH=/etc/securelib
              }

              #
              # Sample unlisted service
              #
              service unlisted
              {
                     type                = UNLISTED
                     socket_type         = stream
                     protocol            = tcp
                     wait                = no
                     server              = /home/user/some_server
                     port                = 20020
              }

SEE ALSO

       xinetd(1L),

       xinetd.log(5)

       Postel J., Echo Protocol, RFC 862, May 1983

       Postel J., Discard Protocol, RFC 863, May 1983

       Postel J., Character Generator Protocol, RFC 864, May 1983

       Postel J., Daytime Protocol, RFC 867, May 1983

       Postel J., Harrenstien K., Time Protocol, RFC 868, May 1983

       M. Lottor, TCP Port Service Multiplexer (TCPMUX), RFC 1078 Nov 1988

       StJohns M.,  Identification Protocol, RFC 1413, February 1993

BUGS

       If the INTERCEPT flag is not used, access control on the address of the
       remote  host  is  not  performed  when  wait  is yes and socket_type is
       stream.

       If the INTERCEPT flag is not used, access control on the address of the
       remote  host for services where wait is yes and socket_type is dgram is
       performed only on the first packet. The server may then accept  packets
       from  hosts  not  in  the access control list. This can happen with RPC
       services.

       There is no way to put a SPACE in an environment variable.

       When wait is yes and socket_type is stream, the socket  passed  to  the
       server can only accept connections.

       The  INTERCEPT  flag  is  not supported for internal services or multi-
       threaded services.

                                 14 June 2001                   XINETD.CONF(5)