Provided by: dhcp-probe_1.3.0-8_i386 bug

NAME

       dhcp_probe.cf - configuration file for dhcp_probe

SYNPOSIS

       /etc/dhcp_probe.cf

DESCRIPTION

       The  file /etc/dhcp_probe.cf contains configuration information used by
       the dhcp_probe(8) daemon.  dhcp_probe reads the  file  when  it  begins
       (and whenever it receives a SIGHUP signal).

       The  location  of  this file defaults to /etc/dhcp_probe.cf, but may be
       overridden by a command-line option to dhcp_probe(8).

       The file consists of a  series  of  statements,  one  per  line.   Each
       statement  begins  with  a  keyword  followed  by one or more arguments
       (depending on the keyword); keywords and  arguments  are  separated  by
       spaces or tabs.  Statements may be specified in any order.

       Some  keywords  take  an  ethernet-address  argument.  Ethernet address
       values must be written in a form that  ether_aton(3)  recognizes;  e.g.
       1:2:3:4:5:6 or 00:A5:b2:0:BB:c.

       Some keywords take an ip-address as a value.  IP address values must be
       written in a form that inet_aton(3) recognizes; e.g.  192.168.1.2.

       Blank lines are ignored.  Lines for which the first non-blank character
       is  a '#' are treated as comments.  Trailing comments on statements are
       not supported.

       Because all presently-defined keywords are optional, the  file  may  be
       empty, however, it must exist.

KEYWORDS

       The keywords are as follows:

   chaddr
              The  chaddr  statement  is  optional, and is used to specify the
              value of the chaddr field in the request  packets  sent  by  the
              program.   This  value  is  also used to compute the DHCP Client
              Identifier option in some of the request  packets  sent  by  the
              program (by prepending x'01').

              Specify:

                     chaddr ethernet-address

              If  not  specified,  this value defaults to the Ethernet address
              corresponding to the interface you specified on the commandline.

              You might want to use the chaddr statement if the  interface  is
              also   a   DHCP  client,  so  that  sending  requests  with  the
              interface's own chaddr/DHCP Client Identifier will not interfere
              with that functionality.

              If  you  specify  a value, be sure to specify a unicast Ethernet
              address that does  not  belong  to  any  valid  client  on  your
              network.

              Correctly-functioning  BootP  and DHCP servers that respond will
              send any responses to the chaddr address, or in some  cases,  to
              the  Ethernet  broadcast  address.   Therefore, if you specify a
              value here  (and  it  differs  from  your  interface's  Ethernet
              address),  the  program  will  have  to place the interface into
              promiscuous mode to be sure it hears unicast responses.

              Note that the chaddr value does not affect the  Ethernet  source
              address of the Ethernet frames sent by the program.

              If you specify this value, you may also wish to specify the same
              value in the ether_src statement.  See the description  of  that
              statement for further discussion.

   ether_src
              The  ether_src statement is optional, and is used to specify the
              value of the ether_src field in the Ethernet frames sent by  the
              program.

              Specify:

                     ether_src ethernet-address

              If  not  specified,  this value defaults to the Ethernet address
              corresponding to the interface you specified on the commandline.

              If you specify a value, be sure to specify  a  unicast  Ethernet
              address  that  does  not  belong  to  any  valid  client on your
              network.

              Note that this value does not affect the  chaddr  field  or  the
              DHCP  Client  Identifier option field in request packets sent by
              the program.

              If you specified a chaddr value, you may also wish to specify an
              equal  ether_src  value.  While not strictly necessary, doing so
              will cause any Layer 2 switches on the  network  to  learn  that
              this  hardware  address  is  on your leg of the network, so they
              will not  need  to  flood  response  packets  directed  to  that
              hardware  address,  but  instead can direct the response packets
              only to your leg of the network.

              Additionally, specifying the same ether_src value could help you
              discover  any buggy BootP or DHCP servers that mistakenly direct
              their responses to the sender's ether_src  (instead  of  to  the
              sender's bootp_chaddr).

   server_id
              The  server_id statement is optional, and is used to specify the
              value of the DHCP Server Identifer option in some of the request
              packets sent by the program.

              Specify:

                     server_id ip-address

              If not specified, this value defaults to 10.254.254.254.

              The  DHCP  Server  Identifer  option  appears in the packets the
              program sends when it mimics a  DHCP  client  in  the  SELECTING
              state.

              It's  best  that  the  DHCP Server Identifier option the program
              uses not match the IP address of any valid DHCP server  on  your
              network,  to  avoid  confusing  them.   Other  than that, any IP
              address is a reasonable value; you may wish to specify one  that
              could never be a valid address on your network.

   client_ip_address
              The  client_ip_address  statement  is  optional,  and is used to
              specify the IP address that the program should request, or claim
              to have a lease on.

              Specify:

                     client_ip_address ip-address

              If not specified, this value defaults to 172.31.254.254.

              When  the  program  generates a DHCPREQUEST packet that mimics a
              DHCP client that is in the INIT-REBOOT or SELECTING  state,  the
              packet  contains  a  Requested IP Address option containing this
              value.  When the program generates  a  DHCPREQUEST  packet  that
              mimics  a DHCP client that is in the REBINDING state, the packet
              contains a ciaddr field containing this value.

              It's best that the value the  program  uses  not  match  the  IP
              address  of  any  valid  DHCP  client  on your network, to avoid
              confusing valid DHCP servers.

              It's extremely useful if the value the program uses not be valid
              (topologically  speaking)  for the physical network on which the
              program   sends   the   packets.    Sending   a    topologically
              inappropriate  value  may stimulate some DHCP servers to respond
              with a DHCPNAK, which helps the program flush out DHCP servers.

   response_wait_time
              The response_wait_time statement is optional,  and  is  used  to
              specify  how  long  the  program should wait for responses after
              sending a single request packet.

              Specify

                     response_wait_time num_milliseconds

              If not specified, this value defaults to  5000  milliseconds  (5
              seconds).

              The  value  is  specified  in milliseconds, and must fit into an
              'int' on your  host.   (Values  larger  than  an  'int'  may  be
              silently  misinterpreted.)  Typical values are on the order of a
              few thousand milliseconds; i.e. several seconds.

   cycle_time
              The cycle_time statement is optional, and is used to specify how
              long the program should sleep between each probe cycle.

              Specify

                     cycle_time num_seconds

              If not specified, this value defaults to 300 seconds.

              The  value  is  specified  in  seconds,  and  must  into into an
              'unsigned int' on your host.  (Values larger than  an  'unsigned
              int'  may be silently misinterpreted.)  Typical valus range from
              several  hundred  to  several  thousand  seconds  (i.e.  several
              minutes to several hours).

              During  each  probe  cycle, the program sends one of the request
              packet flavors, captures any responses that  arrive  during  the
              response_wait_time,  then  repeats  this  for  each of the other
              request packet flavors.  After doing this  for  each  flavor  of
              request  packet,  the  probe  cycle is complete, and the program
              sleeps for the cycle_time.

   legal_server
              The legal_server statement is optional, and is used  to  specify
              the  IP source address of responses that come from a legal BootP
              or DHCP server on your network.  The statement may be  specified
              multiple times.

              Specify

                     legal_server ip-address

              If  not  specified, the program assumes there are no legal BootP
              and DHCP servers on your network; all responses will be  treated
              as coming from an unknown DHCP server.

              When  the  program  receives  a response packet, it compares the
              packet's IP  source  address  to  all  the  addresses  you  have
              specified  in legal_server statements.  If the IP source address
              matches one of these values, the response is deemed to have come
              from  a  known  DHCP  server,  and is ignored.  If the IP source
              address does not match any  of  these  values  (or  you  do  not
              specify  any legal_server), then the program logs a message that
              reports the packet's  IP  source  address  and  Ethernet  source
              address.   Additionally,  if the program was started with the -o
              commandline option, the packet  is  also  written  to  a  packet
              capture file.

              If   both   legal_server  and  legal_server_ethersrc  statements
              appear, then a response must have both a valid IP source  and  a
              valid ethernet source to be considered to have come from a known
              DHCP server.

              When relaying a response from a server to a client,  some  BootP
              Relay  Agents  may  change  the  response's  IP  source address,
              replacing the server's IP address with that of the  BootP  Relay
              Agent.   If BootP Relay Agents on your network do this, you will
              need to specify their IP addresses here instead.

   legal_server_ethersrc
              The legal_server_ethersrc statement is optional, and is used  to
              specify  the Ethernet source address of responses that come from
              a legal BootP or DHCP server on your network.  The statement may
              be specified multiple times.

              Specify

                     legal_server_ethersrc ethernet-address

              If not specified, the program does not check the Ethernet source
              address of responses.

              If you have specified at least one legal_server_ethersrc  value,
              when  the  program  receives  a  response  packet,  the  program
              compares  the  packet's  Ethernet  source  address  to  all  the
              addresses    you   have   specified   in   legal_server_ethersrc
              statements.  If the Ethernet source does not match one of  these
              values, the response is deemed to have come from an unknown DHCP
              server; the program logs a message that reports the packet's  IP
              source  address  and  Ethernet source address.  Additionally, if
              the program was started with  the  -o  commandline  option,  the
              packet is also written to a packet capture file.

              If   both   legal_server  and  legal_server_ethersrc  statements
              appear, then a response must have both a valid IP source  and  a
              valid ethernet source to be considered to have come from a known
              DHCP server.

              Each router on the path from the DHCP server to the DHCP  client
              will  overwrite  the  Ethernet  source address field.  So if you
              specify any  legal_server_ethersrc  statements,  also  list  the
              Ethernet  source  value(s)  for the last hop router(s).  A BootP
              Relay Agent on the path from the DHCP server to the DHCP  client
              will  overwrite  the  Ethernet field.  So also list the Ethernet
              source value(s) for the BootP Relay  Agent.   (The  BootP  Relay
              Agent is often co-resident in the last-hop IP router, so you may
              have already taken care of this when  you  listed  the  last-hop
              router(s).

              The  legal_server_ethersrc  statement is considered experimental
              in version 1.3.0, as it has received only limited testing.

   lease_network_of_concern
              The lease_network_of_concern statement is optional, and  may  be
              specified  multiple times.  The statement is used to specify one
              or more network ranges that are of concern relative  to  the  IP
              addresses distributed by a rogue BootP/DHCP server.

              Specify

                     lease_network_of_concern network-ip-address network-mask

              Specifying   one  or  more  lease_network_of_concern  statements
              activates the "Lease Networks of Concern" feature.

              When the program receives a response packet that  it  determines
              to  be from a rogue BootP/DHCP server, if the "Lease Networks of
              Concern" feature is active, the program will examine the  packet
              further.  If the packet's yiaddr field is non-zero, the value in
              that field is tested to see  if  it  falls  within  any  of  the
              "Leases  Networks of Concern."  If it does, then the message the
              program logs is extended  to  also  report  this  fact,  and  to
              include  the  value  of  the  yiaddr  field.  Furthermore, if an
              alert_program_name2 was specified, when that program is  called,
              it  is called with an additional -y yiaddr option.  (This is not
              supported if an alert_program_name was specified, as  the  older
              alert_program_name uses a syntax that cannot be extended.)

              The  "Lease Networks of Concern" feature does not change the way
              the program probes for  or  detects  rogue  BootP/DHCP  servers.
              Upon  detection  of  a rogue BootP/DHCP server, the feature only
              may cause additional information to  be  added  to  the  message
              logged (and passed to alert_program_name2).

              This  feature  may  be  used,  for  example,  by specifying your
              networks'  legitimate  address  ranges  as  "Lease  Networks  of
              Concern".    While  most  rogue  BootP/DHCP  servers  distribute
              private IP addresses, or send DHCPNAKs  to  legitimate  clients,
              other  more  damaging rogue BootP/DHCP servers may distribute IP
              addresses that fall within your legitimate network ranges.  This
              will  help  differentiate those more damaging incidents from the
              more common ones.

   alert_program_name
              The alert_program_name statement is optional, and may be used to
              specify the name of an external program that should be run every
              time a response packet is received from an unexpected server.

              Note that  using  the  newer  alert_program_name2  statement  is
              preferrable.

              Specify

                     alert_program_name /absolute/path/name

              Unexpected  response packets are reported as a matter of course,
              and optionally written to a packet capture file.  You may use an
              alert_program_name  to provide additional handling of the event,
              for example, to alert an appropriate party via mail  or  paging.
              The alert_program_name you specify is called with four arguments
              in the following order: the name of the  calling  program  (e.g.
              dhcp_probe),  the  name of the interface on which the unexpected
              response packet was received,  the  IP  source  address  of  the
              packet, and the Ethernet source address of the packet.

              As  the alert_program_name is called with the same privileges as
              dhcp_probe (i.e. root), you should exercise  caution  to  ensure
              that the alert program is safe for a privileged user to execute.

              Because  the  syntax  supported  by  the external program is not
              extensible, the use of alert_program_name2 is preferrable.

              You   may    not    specify    both    alert_program_name    and
              alert_program_name2.

   alert_program_name2
              The  alert_program_name2  statement is optional, and may be used
              to specify the name of an external program that  should  be  run
              every  time  a  response  packet  is received from an unexpected
              server.

              Specify

                     alert_program_name2 /absolute/path/name

              Unexpected response packets are reported as a matter of  course,
              and optionally written to a packet capture file.  You may use an
              alert_program_name2 to provide additional handling of the event,
              for  example,  to alert an appropriate party via mail or paging.
              The alert_program_name2 you specify is called with the following
              required options:

                     -p the name of the calling program (e.g. dhcp_probe),
                     -I the name of the interface on which the unexpected response packet was received
                     -i the IP source address of the packet
                     -m Ethernet source address of the packet

              The following non-required options may also be passed:

                     -y the non-zero yiaddr value from the packet, when it falls inside a "Lease Network of Concern"

              The  alert_program_name2 program you specify must ignore options
              or arguments it does not recognize; this is to ensure it remains
              forward-compatible  with  future enhancements to dhcp_probe.  It
              must be prepared to accept options in any order.

              As the alert_program_name2 is called with the same privileges as
              dhcp_probe  (i.e.  root),  you should exercise caution to ensure
              that the alert program is safe for a privileged user to execute.

              You   may    not    specify    both    alert_program_name    and
              alert_program_name2.

EXAMPLE

       An example /etc/dhcp_probe.cf file follows:

              # dhcp_probe.cf: config file for dhcp_probe
              #
              # General syntax:
              #  Comment lines start with '#' (trailing comments not permitted).
              #  Blank lines are OK.
              #  Tokens within a line should be separated with spaces and/or tabs.
              #  Entries in the file may be in any order.
              #  Any 'ethernet-address' must be written in a form that ether_aton(3) recognizes; e.g.
              #      1:2:3:4:5:6   00:A5:b2:0:BB:c
              #  Any 'ip-address' must be written in a form that inet_aton(3) recognizes; e.g.
              #      192.168.1.2
              #
              # ----------------------------------------------------------------------------------
              #
              # CLIENT HARDWARE ADDRESS
              #
              # By default, for the 'chaddr' field in the BootP header, we use the Ethernet
              # address corresponding to the interface you specified.
              # We also use this value to compute the DHCP Client Identifier option (by prepending x'01').
              # You may optionally override this value.
              # (Note that this does not override the Ethernet Src address in the Ethernet frame we send.)
              #
              # You might want to do this if our interface is also a DHCP client, so
              # sending requests with the interface's own chaddr/DHCP Client Identifier would interfere with
              # that functionality.
              #
              # If you specify a value, be sure to specify an Ethernet address that does not belong to
              # any valid client on your network.  Be sure to specify a unicast Ethernet address.
              #
              # Syntax:
              #    chaddr enet-addr

              chaddr 0:0:0:1:2:3

              # ----------------------------------------------------------------------------------
              #
              # ETHERNET SOURCE ADDRESS
              #
              # By default, for the 'ether_shost' field in the Ethernet header, we use the Ethernet
              # address corresponding to the interface you specified.
              # You may optionally override this value.
              # (Note that this does not override the 'chaddr' in the BootP header, nor the DHCP Client Identifier.)
              #
              # If you are specify the 'chaddr' statement, you might want to also do this, so you don't miss buggy
              # DHCP servers that respond (incorrectly) to ether_src instead of to chaddr.
              #
              # If you specify a value, be sure to specify an Ethernet address that does not belong to
              # any valid client on your network.  Be sure to specify a unicast Ethernet address.
              #
              # Syntax:
              #    ether_src enet-addr

              ether_src 0:0:0:1:2:3

              # ----------------------------------------------------------------------------------
              #
              # DHCP SERVER IDENTIFIER
              #
              # When we generate a DHCPREQUEST packet corresponding to a client that is in the SELECTING
              # state, the options field must contain a 'DHCP Server Identifier' option, indicating the
              # IP address of the DHCP server the client is selecting.   It's best that the value we use
              # not match the IP address of any valid DHCP server, to avoid confusing them.  The program
              # provides a default value of 10.254.254.254, which you may override here.
              #
              # Syntax:
              #    server_id ip-addr

              server_id 10.1.2.3

              # ----------------------------------------------------------------------------------
              #
              # CLIENT IP ADDRESS
              #
              # When we generate a DHCPREQUEST packet corresponding to a client that is in the INIT-REBOOT
              # or SELECTING state, the options field must containg a 'Requested IP Address' option, indicating
              # the IP address the client is requesting.    When we generate a DHCPREQUEST packet corresponding
              # to a client that is in the REBINDING state, the 'ciaddr' field in the BootP header must contain
              # the IP address that the DHCP client presently has leased and wishes to renew.
              #
              # In all these cases, it's best that the value we use not match the IP address of any valid DHCP client,
              # to avoid confusing the valid DHCP servers.
              #
              # Furthermore, it is extremely useful if the value we use *not* be valid (topologically speaking) for the
              # physical network on which we send the packets.  Sending a topologically inappropriate value
              # may stimulate some DHCP servers to respond with a DHCPNAK, which helps us flush out DHCP servers.
              # (This will probably happen only in response to the packets we sending when pretending to be in REBINDING state.)
              #
              # The program provides a default value of 172.31.254.254, which you may override here.
              #
              # Syntax:
              #   client_ip_address ip-addr

              # client_ip_address 172.31.254.254

              # ----------------------------------------------------------------------------------
              #
              # RESPONSE WAIT TIME
              #
              # After sending one packet, we wait for responses.  The length of time we wait
              # is the 'response_wait_time'.  The program provides a default value of 5000, which you
              # may override here.  The value is measured in milliseconds, and must fit into
              # an 'int' on your host.  (Values larger than an 'int' may be silently misinterpreted.)
              # Typical values are on the order of a few thousand milliseconds; i.e. several seconds.
              #
              # Syntax:
              #    response_wait_time num_milliseconds

              # response_wait_time 5000

              # ----------------------------------------------------------------------------------
              #
              # CYCLE WAIT TIME
              #
              # For each flavor packet, we send the packet and listen for responses to that packet.
              # After doing this for all flavor packets, we go to sleep for the "cycle_time",
              # then repeat the process.  The program provides a default value of 300, which you
              # may override here.  The value is measured in seconds, and must fit into an
              # 'unsigned int' on your host.  (Values larger than an 'unsigned int' may be silently
              # misinterpreted.)  Typical valus range from several hundred to several thousand
              # seconds (i.e. several minutes to several hours).
              #
              # Syntax:
              #    cycle_time num_seconds

              cycle_time 1200

              # ----------------------------------------------------------------------------------
              #
              # LEGAL SERVERS' IP SOURCE ADDRESSES
              #
              # After sending one packet, we wait for responses.  Responses from legal BootP or DHCP
              # servers are ignored; presumably you aren't interesting in discovering them.
              # Specify a legal server's IP source address with the 'legal_server' statement.
              # The value you specify is compared to the IPsrc field in each response's IP header.
              #
              # If you have multiple legal servers, specify each in a separate statement.
              # If your BootP Relay Agents overwrite the server's IP address in the IPsrc field
              # with their own IP addresses, you will need to list the IP addresses of the
              # BootP Relay Agents.
              #
              # Alternatively, do not specify any legal_server statements at all, so *no* responses
              # will be considered legal.
              # (This is different from the way legal_server_ethersrc statements are handled.)
              #
              # If both legal_server and legal_server_ethersrc statements appear, then a response
              # must have both a valid IP source and a valid ethernet source to be considered legal.
              #
              # Syntax:
              #   legal_server ip-addr

              legal_server 192.168.1.2
              legal_server 192.168.3.4

              # ----------------------------------------------------------------------------------
              #
              # LEGAL SERVERS' ETHERNET SOURCE ADDRESSES
              #
              # Specify a legal server's Ethernet source address with the 'legal_server_ethersrc' statement.
              # The value you specify is compared to the ethernet_src field in each response's IP header.
              #
              # If you have multiple legal ethernet sources, specify each in a separate statement.
              # Each router on the path from the DHCP server to the DHCP client will overwrite
              # the ethernet_src field.  So also list the ethernet_src value(s) for the last hop router(s).
              # The BootP Relay Agent on the path from the DHCP server to the DHCP client will overwrite
              # the ethernet_src field.  So also list the ethernet_src value(s) for the BootP Relay Agent.
              # (This is often co-resident in the last-hop IP router, so you may have already taken care
              # of this when you listed the last-hop router(s).
              #
              # Alternatively, do not specify any legal_server_ethersrc statements at all.
              # If none are specified, then all ethernet_src values are considered legal.
              # (This is different from the way legal_server statements are handled.)
              #
              # If both legal_server and legal_server_ethersrc statements appear, then a response
              # must have both a valid IP source and a valid ethernet source to be considered legal.
              #
              # Syntax:
              #   legal_server_ethersrc enet-addr

              # legal_server_ethersrc 0:2:4:ab:cd:ef
              # legal_server_ethersrc 0:17:30:1:0A:3

              # ----------------------------------------------------------------------------------
              #
              # ALERT PROGRAM NAME
              #
              # In addition to logging a response received from an unexpected server, we will optionally
              # call a user-specified 'alert program' if one is specified here.  To use this feature,
              # specify the absolute pathname of a program we should execute for each unexpected response.
              # Either specify it using the older 'alert_program_name' statement, or (preferrably) using
              # the newer 'alert_program_name2' statement.  (The newer statement is preferrable because
              # it calls the alert program with a more extensible syntax.)  You may not specify
              # both alert_program_name and alert_program_name2.
              #
              # Old style alert program:
              #
              # Syntax:
              #   alert_program_name /absolute/path/name
              #
              # The program specified via 'alert_program_name' will be called as follows:
              #   /absolute/path/name  name_of_calling_program  name_of_interface_on_which_the_response_was_received  IP_source_of_the_response  ether_src_of_the_response
              #
              #
              # Newer style alert program:
              #
              # Syntax:
              #   alert_program_name2 /absolute/path/name
              #
              # The program specified via 'alert_program_name2' will be called as follows:
              #   /absolute/path/name  -p name_of_calling_program  -I name_of_interface_on_which_the_response_was_received  -i IP_source_of_the_response  -m ether_src_of_the_response [-y yiaddr_when_in_lease_networks_of_concern]
              # The options may appear in any order.
              # The program must silently ignore any options or arguments it does not recognize,
              # so as to be forward-compatible with future enhancements to dhcp_probe.

              alert_program_name2 /usr/local/etc/dhcp_probe_notify2

              # ----------------------------------------------------------------------------------
              #
              # LEASE NETWORKS OF CONCERN
              #
              # Optionally define one or more network ranges that are to be treated as
              # being of special concern when a rogue BootP/DHCP server is detected sending response
              # that contains a 'yiaddr' value that falls into any of these ranges.
              # Specify each such network ranges of concern in a separate statement.
              # When the yiaddr value in a rogue server's response falls into any of these ranges,
              # the message logged will contain additional text remarking on this fact.
              # And if an alert_program_name2 is used, that alert program
              # will be called with an extra option so it can also act on that fact.
              #
              # If you specify all your networks' legitimate IP ranges, this can help you
              # take additional notice of rogue BootP/DHCP servers that distribute *your*
              # network addresess, rather than simply distribute private IP address or
              # send DHCPNAKs to legitimate clients.
              #
              # Syntax:
              #    lease_network_of_concern  IP-network-address network-mask

              lease_network_of_concern 128.112.0.0 255.255.0.0
              lease_network_of_concern 140.180.0.0 255.255.0.0

SEE ALSO

       dhcp_probe(8)