dccm(8)               Distributed Checksum Clearinghouse               dccm(8)


NAME

     dccm -- Distributed Checksum Clearinghouse Milter Interface


SYNOPSIS

     dccm [-VdbxANPQ] [-G on | off | noIP | IPmask/xx] [-h homedir] [-I user]
          [-p protocol:filename | protocol:port@host] [-m map]
          [-w whiteclnt] [-U userdirs] [-a IGNORE | REJECT | DISCARD]
          [-t type,[log-thold,]rej-thold] [-g [not-]type] [-S header]
          [-l logdir] [-R rundir] [-r rejection-msg] [-j maxjobs]
          [-B dnsbl-option] [-L ltype,facility.level]


DESCRIPTION

     dccm is a daemon built with the sendmail milter interface intended to
     connect sendmail(8) to DCC servers.  When built with the milter filter
     machinery and configured to talk to dccm in the sendmail.cf file, send-
     mail passes all email to dccm which in turn reports related checksums to
     the nearest DCC server.  dccm then adds an X-DCC SMTP header line to the
     message.  Sendmail is told to reject the message if it is unsolicited
     bulk mail.

     Dccm sends reports of checksums related to mail received by DCC clients
     and queries about the total number of reports of particular checksums.  A
     DCC server receives no mail, address, headers, or other information, but
     only cryptographically secure checksums of such information.  A DCC
     server cannot determine the text or other information that corresponds to
     the checksums it receives.  Its only acts as a clearinghouse of counts
     for checksums computed by clients.  For complete privacy as far as the
     DCC is concerned, the checksums of purely internal mail or other mail
     that is known to not be unsolicited bulk can be listed in a whitelist to
     not be reported to the DCC server.

     Since the checksums of messages that are whitelisted locally by the
     /var/dcc/whiteclnt file are not reported to the DCC server, dccm knows
     nothing about the total recipient counts for their checksums and so can-
     not add X-DCC header lines to such messages.  Sendmail does not tell dccm
     about messages that are not received by sendmail via SMTP, including mes-
     sages submitted locally and received via UUCP, and so they also do not
     receive X-DCC header lines.

     Enable the daemon and put its parameters in the /var/dcc/conf file and
     start the daemon with the /var/dcc/libexec/start-dccm or
     /var/dcc/libexec/rcDCC scripts.

     The list of servers that dccm contacts is in the memory mapped file
     /var/dcc/map shared by local DCC clients.  The file is  maintained with
     cdcc(8).

   OPTIONS
     The following options are available:

     -V   displays the version of dccm.  Two or more -V options show the
          options with which it was built.

     -d   enables debugging output from the DCC client software.  Additional
          -d options increase the number of messages.  A single -d logs
          aborted SMTP transactions including those from some "dictionary
          attacks."

     -b   causes the daemon to not detach itself from the controlling tty and
          put itself into the background.

     -x   causes the daemon to try "extra hard" to contact a DCC server.
          Since it is usually more important to deliver mail than to report
          its checksums, dccm normally does not delay too long while trying to
          contact a DCC server.  It will not try again for several seconds
          after a failure.  With -x, it will always try to contact the DCC
          server and it will tell the MTA to answer the DATA command with a
          4yz temporary failure.

     -A   adds to existing X-DCC headers in the message instead of replacing
          existing headers of the brand of the current server.

     -N   neither adds, deletes, nor replaces existing X-DCC headers in the
          message.  Each mail message is logged, rejected, and otherwise han-
          dled the same.

     -P   The SpamAsassin DCC.pm plugin should watch for "bulk" in X-DCC SMTP
          header fields, but historically has looked for counts of "many".
          However, there are situations when dccm knows that a mail message is
          extremely bulky and probably spam.  For example, mail from a sender
          that is blacklisted in whiteclnt gets an X-DCC header that includes
          bulk.  To acommodate that bug in SpamAssassin, by default whenever
          dccm generates an X-DCC header containing "bulk", it also forces the
          Body count to "many".  -P turns off that kludge and the Body con-
          tains the count from the DCC server.

     -Q   only queries the DCC server about the checksums of messages instead
          of reporting.  This is useful when dccm is used to filter mail that
          has already been reported to a DCC server by another DCC client.  No
          single mail message should be reported to a DCC server more than
          once per recipient, because each report will increase the apparent
          "bulkness" of the message.

          It is better to use MXDCC lines in the global /var/dcc/whiteclnt
          file for your MX mail servers that use DCC than to use -Q with dccm.

          Do not use -Q except on mail that you know has been reported to a
          DCC server.  DCC depends on reports of all except known private mail
          and works only because almost no DCC installations use -Q.

     -G on | off | noIP | IPmask/xx
          controls greylisting.  At least one working greylist server must be
          listed in the /var/dcc/map file.  If more than one is named, they
          must "flood" or change checksums and they must use the same -G
          parameters.  See dccd(8).  Usually all dccm or dccifd DCC client
          processes use the same -G parameters.

          IPmask/xx and noIP remove part or all of the IP address from the
          greylist triple.

     -h homedir
          overrides the default DCC home directory, /var/dcc.

     -I user
          specifies the UID and GID of the process.

     -p protocol:filename | protocol:port@host
          specifies the protocol and address by which sendmail will contact
          dccm.  The default is a UNIX domain socket in the "run" directory,
          /var/run/dcc/dccm.  (See also -R) This protocol and address must
          match the value in sendmail.cf.  This mechanism can be used to con-
          nect dccm on one computer to sendmail on another computer when a
          port and host name or IP address are used.

     -m map
          specifies a name or path of the memory mapped parameter file instead
          of the default /var/dcc/map.  It should be created with the cdcc(8)
          command.

     -w whiteclnt
          specifies an optional file containing filtering parameters as well
          as SMTP client IP addresses, SMTP envelope values, and header values
          of mail that is spam or is not spam and does not need a X-DCC
          header, and whose checksums should not be reported to the DCC
          server.

          If the pathname whiteclnt is not absolute, it is relative to the DCC
          home directory.

          The format of the dccm whiteclnt file is the same as the
          /var/dcc/whitelist files used by dbclean(8) and the whiteclnt file
          used by dccproc(8).  See dcc(8) for a description of DCC white and
          blacklists.  Because the contents of the whiteclnt file are used
          frequently, a companion file is automatically created and main-
          tained.  It has the same pathname but with an added suffix of .dccw
          and contains a memory mapped hash table of the main file.

          A whitelist entry ("OK") or two or more semi-whitelistings ("OK2")
          for one of the message's checksums prevents all of the message's
          checksums from being reported to the DCC server and the addition of
          a X-DCC header line by dccm.  A whitelist entry for a checksum also
          prevents rejecting or discarding the message based on DCC recipient
          counts as specified by -a and -t.  Otherwise, one or more checksums
          with blacklisting entries ("MANY") cause all of the message's check-
          sums to be reported to the server with an addressee count of "MANY".

          If the message has a single recipient, an env_To whiteclnt entry of
          "OK" for the checksum of its recipient address acts like any other
          whiteclnt entry of "OK."  When the SMTP message has more than one
          recipient, the effects can be complicated.  When a message has sev-
          eral recipients with some but not all listed in the whiteclnt file,
          dccm tries comply with the wishes of the users who want filtering as
          well as those who don't by silently not delivering the message to
          those who want filtering (i.e. are not whitelisted) and delivering
          the message to users who don't want filtering.

     -U userdirs
          enables per-user whiteclnt files and log directories.  Each target
          of a message can have a directory of log files named
          usedirs/${dcc_userdir}/log where ${dcc_userdir} is the sendmail.cf
          macro described below.  If ${dcc_userdir} is not set,
          userdirs/${rcpt_mailer}/${rcpt_addr}/log is used.  The most likely
          value of mailer is local.  Appropriate values for both
          ${rcpt_mailer} and ${rcpt_addr} can be seen by examining env_To
          lines in -l logdir files.  If it is not absolute, userdirs is rela-
          tive to the DCC home directory.  The directory containing the log
          files must be named log and it must be writable by the dccm process.
          Each log directory must exist or logging for the corresponding is
          silently disabled.  The files created in the log directory are owned
          by the UID of the dccm process, but they have group and other read
          and write permissions copied from the corresponding log directory.
          To ensure the privacy of mail, it may be good to make the directo-
          ries readable only by owner and group, and to use a cron script that
          changes the owner of each file to match the grandparent addr direc-
          tory.

          There can also be a per-user whitelist file named
          userdirs/addr/whiteclnt for each addressee addr. Any checksum that
          is not white- or blacklisted by an individual addressee's per-user
          whiteclnt file  is checked in the main /var/dcc/whiteclnt file.  A
          missing per-addressee whiteclnt file is the same as an empty file.
          Relative paths for files included in per-addressee files are
          resolved in the DCC home directory.  The whiteclnt files and the
          addr directories containing them must be writable by the dccm
          process.

          Option lines in per-user whiteclnt files can be used to modify many
          aspects of dccm filtering, as described in the main dcc man page.
          For example, an option dcc-off line turns off DCC filtering for
          individual mailboxes.

     -a IGNORE | REJECT | DISCARD
          specifies the action taken when DCC server counts or -t thresholds
          say that a message is unsolicited and bulk.  IGNORE causes the mes-
          sage to be unaffected except for adding the X-DCC header line to the
          message.  This turns off all filtering except greylisting.

          Spam can also be REJECTed or accepted and silently DISCARDed without
          being delivered to local mailboxes.  The default is REJECT.

          Mail forwarded via IP addresses marked MX or MXDCC in the main
          /var/dcc/whiteclnt file is treated as if -a DISCARD were specified.
          This prevents "bouncing" spam.

          Determinations that mail is or is not spam from sendmail via
          ${dcc_isspam} or ${dcc_notspam} macros override -a.  The effects of
          the -w whiteclnt are not affected by -a.

     -t type,[log-thold,]rej-thold
          sets logging and "spam" thresholds for checksum type.  The checksum
          types are IP, env_From, From, Message-ID, substitute, Received,
          Body, Fuz1, Fuz2, rep-total, and rep.  The first six, IP through
          substitute, have no effect except when a local DCC server configured
          with -K is used.  The substitute thresholds apply to the first sub-
          stitute heading encountered in the mail message.  The string ALL
          sets thresholds for all types, but is unlikely to be useful except
          for setting logging thresholds.  The string CMN specifies the com-
          monly used checksums Body, Fuz1, and Fuz2.  Rej-thold and log-thold
          must be numbers, the string NEVER, or the string MANY indicating
          millions of targets.  Counts from the DCC server as large as the
          threshold for any single type are taken as sufficient evidence that
          the message should be logged or rejected.

          Log-thold is the threshold at which messages are logged.  It can be
          handy to log messages at a lower threshold to find solicited bulk
          mail sources such as mailing lists.  If no logging threshold is set,
          only rejected mail and messages with complicated combinations of
          white and blacklisting are logged.  Messages that reach at least one
          of their rejection thresholds are logged regardless of logging
          thresholds.

          Rej-thold is the threshold at which messages are considered "bulk,"
          and so should be rejected or discarded if not whitelisted.

          DCC Reputation thresholds in the commercial version of DCC are con-
          trolled by thresholds on checksum types rep and rep-total.  The DCC
          Reputations of IP addresses that the DCC database says have sent
          more than rep-total,log-thold are computed and messages from those
          addresses are logged.  Messages from IP addresses with DCC Reputa-
          tions of at least the rep,rej-thold rejection threshold can be
          rejected.  The DCC Reputation of an IP address is the percentage of
          its messages known to have been sent to at least 10 recipients.  The
          defaults are equivalent to rep,never and rep-total,never,20.

          Bulk DCC Reputations do not reject mail unless enabled by an
          option DCC-rep-on line a whiteclnt file.

          The checksums of locally whitelisted messages are not checked with
          the DCC server and so only the number of targets of the current copy
          of a whitelisted message are compared against the thresholds.

          The default is ALL,NEVER, so that nothing is discarded, rejected, or
          logged.  A common choice is CMN,25,50 to reject or discard mail with
          common bodies except as overridden by the whitelist of the DCC
          server, the sendmail ${dcc_isspam} and ${dcc_notspam} macros, and
          -g, and -w.

     -g [not-]type
          indicates that whitelisted, OK or OK2, counts from the DCC server
          for a type of checksum are to be believed.  They should be ignored
          if prefixed with not-.  Type is one of the same set of strings as
          for -t.  Only IP, env_From, and From are likely choices.  By default
          all three are honored, and hence the need for not-.

     -S hdr
          adds to the list of substitute or locally chosen headers that are
          checked with the -w whiteclnt file and sent to the DCC server.  The
          checksum of the last header of type hdr found in the message is
          checked.  Hdr can be HELO to specify the SMTP envelope HELO value.
          Hdr can also be mail_host to specify the host name from the
          Mail_from value in the SMTP envelope.  As many as 8 different sub-
          stitute headers can be specified, but only the checksum of the first
          will be sent to the DCC server.

     -l logdir
          specifies a directory in which files containing copies of messages
          processed by dccm are kept.  They can be copied to per-user directo-
          ries specified with -U.  Information about other recipients of a
          message is deleted from the per-user copies.

          See the FILES section below concerning the contents of the files.
          See also the option log-subdirectory-{day,hour,minute} lines in
          whiteclnt files described in dcc(8).

          The directory is relative to the DCC home directory if it is not
          absolute

     -R rundir
          specifies the "run" directory where the UNIX domain socket and file
          containing the daemon's process ID are stored.  The default value is
          /var/run/dcc .

     -r rejection-msg
          specifies the rejection message for unsolicited bulk mail or for
          mail temporarily blocked by greylisting when -G is specified.  The
          first -r rejection-msg replaces the default bulk mail rejection mes-
          sage, "5.7.1 550 mail %ID from %CIP rejected by DCC".  The second
          replaces "4.2.1 452 mail %ID from %CIP temporary greylist embar-
          goed".  The third -r rejection-msg replaces the default SMTP rejec-
          tion message "5.7.1 550 %ID bad reputation; see http://commercial-
          dcc.rhyolite.com/cgi-bin/reps.cgi?tgt=%CIP" for mail with bulk DCC
          Reputations.  If rejection-msg is the zero-length string, the -r
          setting is counted but the corresponding default message is not
          changed.

          Rejection-msg can contain specific information about the mail mes-
          sage.  The following strings starting with % are replaced with the
          corresponding values:
              %ID       message ID such as the unique part of log file name or
                        sendmail queue ID
              %CIP      SMTP client IP address
              %BTYPE    type of DNS blacklist hit, such as "SMTP client",
                        "mail_host", or "URL NS"
              %BTGT     IP address or name declared bad by DNS blacklist
              %BPROBE   domain name found in DNS blacklist such as
                        4.3.2.10.example.com
              %BRESULT  value of the %BPROBE domain name found in DNS black-
                        list

          A common alternate for the bulk mail rejection message is "4.7.1 451
          Access denied by DCC" to tell the sending mail system to continue
          trying.  Use a 4yz response with caution, because it is likely to
          delay for days a delivery failure message for false positives.  If
          the rejection message does not start with an RFC 1893 status code
          and RFC 2821 reply code, 5.7.1 and 550 or 4.2.1 and 452 are used.

          See also -B set:rej-msg to set the status message for mail rejected
          by DNS blacklists.

     -j maxjobs
          limits the number of simultaneous requests that will be processed.
          The default value is the maximum number that seems to be possible
          given system limits on open files, select() bit masks, and so forth.
          Start dccm with -d and see the starting message in the system log to
          see the limit.

     -B dnsbl-option
          enables DNS white- and blacklist checks of the SMTP client IP
          address, SMTP envelope Mail_From sender domain name, and of host
          names in URLs in the message body.  Body URL blacklisting has too
          many false positives to use on abuse mailboxes.  It is less effec-
          tive than greylisting with dccm(8) or dccifd(8) but can be useful in
          situations where greylisting cannot be used.  It can be combined
          with greylisting.

          Dnsbl-option is either one of the -B set:option forms or
              -B domain[any[,bltype]]
              -B domain[,IPaddr[/xx[&IPmask][,bltype]]]
              -B domain[,IPaddrLO[-IPaddrHI[&IPmask][,bltype]]]
          Domain is a DNS blacklist domain such as example.com that will be
          searched.  The strings any, IPaddr, IPaddr/xx, or IPaddrLO-IPaddrHI,
          specifies which IP addresses found in the DNS blacklist after apply-
          ing the optional IP address mask IPmask say that mail messages
          should be rejected or accepted with -B set:white.  "127.0.0.2" is
          assumed if no address(es) are specified.  IPv6 addresses can be
          specified with the usual colon (:) notation.  Host names can be used
          instead of numeric addresses.  The type of DNS blacklist is speci-
          fied by bltype as name, all-names, IPv4, or IPv6.  Given an envelope
          sender domain name or a domain name in a URL of spam.domain.org and
          a blacklist of type name, spam.domain.org.example.com will be looked
          up.  The names spam.domain.org.example.com, domain.org.example.com,
          and org.example.com will be looked up in blacklists of type
          all-names.  Use name with DNS blacklists that use wildcards for
          speed but all-names for other DNS name blacklists.  Blacklist types
          of IPv4 and IPv6 require that the domain name in a URL sender
          address be resolved into an IPv4 or IPv6 address.  The resolved
          address from the mail message is then written as a reversed string
          of decimal octets to check the DNS blacklist, as in
          2.0.0.127.example.com.

          A domain of "."  and type of name can be used to blacklist domain
          names with specified addresses.  This can be useful to detect URLs
          with domain names listed in a Response Policy Zone (RPZ).  For exam-
          ple, the following can be used to reject mail containing URLs listed
          by a response policy zone that maps evil domain names to 224.0.0.0
          with an informative status message:

            '-Bset:rej-msg=5.7.1 550 %ID %BTYPE \
                  http://www.example.org/query/dbl?domain=%BTGT'
            -B.,224.0.0.0,name

          More than one blacklist can be specified and blacklists can be
          grouped with -B set:group=X.  All searching within a group of black-
          lists is stopped at the first positive result.

          Unlike dccproc(8), positive results are ignored by dccm after being
          logged unless an option DNSBL-on or option DNSBLx-on line appears a
          whiteclnt file.

          -B set:no-client
               implies that SMTP client IP addresses and reverse DNS domain
               names should not be checked in the following blacklists.
               -B set:client restores the default for the following black-
               lists.

          -B set:no-mail_host
               implies that SMTP envelope Mail_From sender domain names should
               not be checked in the following blacklists.  -B set:mail_host
               restores the default.

          -B set:no-URL
               says that URLs in the message body should not be checked in the
               in the following blacklists.  -B set:URL restores the default.

          -B set:no-MX
               says MX servers of sender Mail_From domain names and host names
               in URLs should not be checked in the following blacklists.
               -B set:MX restores the default.

          -B set:no-NS
               says DNS servers of sender Mail_From domain names and host
               names in URLs should not be checked in the following black-
               lists.  -B set:NS restores the default.

          -B set:white
               says the DNS list is a whitelist of names or IP addresses.
               -B set:black restores the default.  DNS whitelist usually also
               need -B set:no-mail_host, -B set:no-URL, -B set:no-MX,
               -B set:no-NS, and -B set:no-mail_host.

          -B set:defaults
               is equivalent to all of -B set:black -B set:client
               -B set:mail_host -B set:URL -B set:MX and -B set:NS

          -B set:group=X
               adds following DNS blacklists specified with -B domain[...] to
               group 1, 2, 3, or 4.

          -B set:debug=X
               sets the DNS blacklist logging level

          -B set:msg-secs=S
               limits dccm to S seconds total for checking all DNS blacklists.
               The default is 25.

          -B set:URL-secs=S
               limits dccm to at most S seconds resolving and checking any
               single URL or IP address.  The default is 11.  Some spam con-
               tains dozens of URLs and some "spamvertised" URLs contain host
               names that need minutes to resolve.  Busy mail systems cannot
               afford to spend minutes checking each incoming mail message.

          -B set:rej-msg="rejection message"
               sets the SMTP rejection message for the following blacklists.
               Rejection-msg must be in the same format as for -r.  If
               rejection message is null, the default is restored.  The
               default DNS blacklist rejection message is the first message
               set with -r.

          -B set:max_helpers=X
               sets maximum number of helper processes to X.  In order to use
               typical single-threaded DNS resolver libraries, dccm uses
               fleets of helper processes.  It is rarely a good idea to change
               the default, which is the same as the maximum number of simul-
               taneous jobs set with -j.

          -B set:progpath=/var/dcc/libexec/dns-helper
               changes the path to the helper program.

     -L ltype,facility.level
          specifies how messages should be logged.  Ltype must be error, info,
          or off to indicate which of the two types of messages are being con-
          trolled or to turn off all syslog(3) messages from dccm.  Level must
          be a syslog(3) level among EMERG, ALERT, CRIT, ERR, WARNING, NOTICE,
          INFO, and DEBUG.  Facility must be among AUTH, AUTHPRIV, CRON,
          DAEMON, FTP, KERN, LPR, MAIL, NEWS, USER, UUCP, and LOCAL0 through
          LOCAL7.  The default is equivalent to
                -L info,MAIL.NOTICE -L error,MAIL.ERR

     dccm normally sends counts of mail rejected and so forth the to system
     log at midnight.  The SIGUSR1 signal sends an immediate report to the
     system log.  They will be repeated every 24 hours instead of at midnight.


SENDMAIL MACROS

     Sendmail can affect dccm with the values of some sendmail.cf macros.
     These macro names must be added to the Milter.macros option statements in
     sendmail.cf as in the example "Feature" file dcc.m4.

     ${dcc_isspam}  causes a mail message to be reported to the DCC server as
                    having been addressed to "MANY" recipients.  The
                    ${dcc_isspam} macro is ignored if the ${dcc_notspam} macro
                    is set to a non-null string

                    If the value of the ${dcc_isspam} is null, dccm uses SMTP
                    rejection messages controlled by -a and -r.  If the value
                    of the ${dcc_isspam} macro starts with "DISCARD", the mail
                    message is silently discarded as with -a DISCARD. If value
                    of the macro not null and does not start with "DISCARD",
                    it is used as the SMTP error message given to the SMTP
                    client trying to send the rejected message.  The message
                    starts with an optional SMTP error type and number fol-
                    lowed by text.

                    The -a option does not effect messages marked spam with
                    ${dcc_isspam}.  When the ${dcc_isspam} macro is set, the
                    message is rejected or discarded despite local or DCC
                    database whitelist entries.  The local whitelist does con-
                    trol whether the message's checksums will be reported to
                    the DCC server and an X-DCC SMTP header line will be
                    added.

     ${dcc_notspam}
                    causes a message not be considered unsolicited bulk
                    despite evidence to the contrary.  It also prevents dccm
                    from reporting the checksums of the message to the DCC
                    server and from adding an X-DCC header line.

                    When the macro is set by the sendmail.cf rules,
                    ${dcc_notspam} macros overrides DCC threshlds that say the
                    message should be rejected as well as the effects of the
                    ${dcc_isspam} macro.

     ${dcc_mail_host}
                    specifies the name of the SMTP client that is sending the
                    message.  This macro is usually the same as the mail_host
                    macro.  They can differ when a sendmail "smart relay" is
                    involved.  The ${dcc_mail_host} macro does not work if
                    FEATURE(delay_checks) is used, and so dccm falls back on
                    mail_host.

     ${dcc_userdir}
                    is the per-user whitelist and log directory for a recipi-
                    ent.  If the macro is not set in sendmail.cf,
                    $&{rcpt_mailer}/$&{rcpt_addr} is assumed, but with the
                    recipient address converted to lower case.  Whatever value
                    is used, the directory name after the last slash (/) char-
                    acter is converted to lower case.  Any value containing
                    the string "/../" is ignored.

                    This macro also does not work if FEATURE(delay_checks) is
                    used.

                    The following two lines in a sendmail mc file have the
                    same effect as not defining the ${dcc_userdir} macro, pro-
                    vided FEATURE(dcc) is also used and the sendmail
                    cf/feature directory has a symbolic link to the
                    /var/dcc/build/dcc/misc/dcc.m4 file.

     SLocal_check_rcpt
     R$*     $: $1 $(macro {dcc_userdir} $@ $&{rcpt_mailer}/$&{rcpt_addr} $))


FILES

     /var/dcc   is the DCC home directory.
     /var/dcc/libexec/start-dccm
                is a script used by /var/dcc/libexec/rcDCC to start dccm.
     dcc_conf   contains parameters used by the scripts to start DCC daemons
                and cron jobs.
     logdir     is an optional directory specified with -l and containing
                marked mail.  Each file in the directory contains one message,
                at least one of whose checksums reached its -t thresholds or
                that is interesting for some other reason.  Each file starts
                with lines containing the date when the message was received,
                the IP address of the SMTP client, and SMTP envelope values.
                Those lines are followed by the body of the SMTP message
                including its header as it was received by sendmail and with-
                out any new or changed header lines.  Only approximately the
                first 32 KBytes of the body are recorded unless modified by
                ./configure --with-max-log-size=xx The checksums for the mes-
                sage follow the body.  They are followed by lines indicating
                that the ${dcc_isspam} or ${dcc_notspam} sendmail.cf macros
                were set or one of the checksums is white- or blacklisted by
                the -w whiteclnt file.  Each file ends with the X-DCC header
                line added to the message and the disposition of the message
                including SMTP status message if appropriate.
     map        is the memory mapped file of information concerning DCC
                servers in the DCC home directory.  See -m.
     whiteclnt  contains the client whitelist in the format described in
                dcc(8).  See -w.
     whiteclnt.dccw
                is a memory mapped hash table of the /var/dcc/whiteclnt file.
     /var/run/dcc/dccm.pid
                directory contains daemon's process ID.  The string ``dccm''
                is replaced by the file name containing the daemon to facili-
                tate running multiple daemons, probably connected to remote
                instances of sendmail using TCP/IP instead of a UNIX domain
                socket.  See also -R.
     /var/run/dcc/dccm
                is the default UNIX domain socket used by the sendmail milter
                interface.  See also -R.
     sendmail.cf
                is the sendmail(8) control file.
     /var/dcc/build/dcc/misc/dcc.m4
                sendmail mc file that should have a symbolic link in the send-
                mail cf/feature directory so that FEATURE(dcc) can be used in
                a sendmail mc file.


EXAMPLES

     Dccm should be started before sendmail with something like the script
     /var/dcc/libexec/start-dccm. It looks for common DCC parameters in the
     /var/dcc/dcc_conf file.

     Those numbers should modified to fit local conditions.  It might be wise
     to replace the "100" numbers with much larger values or with "MANY" until
     a few weeks of monitoring the log directory show that sources of mailing
     lists are in the server's whitelist file (see dccd(8)) or the local
     /var/dcc/whiteclnt file.

     It is usually necessary to regularly delete old log files with a script
     like /var/dcc/libexec/cron-dccd.

     On systems unlike modern FreeBSD and other UNIX-like systems which
     include sendmail milter support, sendmail must be built with the milter
     interface, such as by creating a devtools/Site/site.config.m4 or similar
     file containing something like the following lines:

           APPENDDEF(`conf_sendmail_ENVDEF', `-D_FFR_MILTER=1')
           APPENDDEF(`conf_libmilter_ENVDEF', `-D_FFR_MILTER=1')

     Appropriate lines invoking the milter interface must be added to
     sendmail.cf. That can be done by putting a symbolic link to the the
     misc/dcc.m4 file in the DCC source to the sendmail cf/feature directory
     and adding the line

           FEATURE(dcc)

     to the local .mc file.

     Note that dccm should not be used with the Postfix milter mechanism.
     Instead use dccifd(8) as a before-queue filter as described in that man
     page.


SEE ALSO

     cdcc(8), dbclean(8), dcc(8), dccd(8), dblist(8), dccifd(8), dccproc(8),
     dccsight(8), sendmail(8).


HISTORY

     Distributed Checksum Clearinghouses are based on an idea of Paul Vixie.
     Implementation of dccm was started at Rhyolite Software in 2000.  This
     document describes version 1.3.154.


BUGS

     dccm uses -t where dccproc(8) uses -c.

     Systems without setrlimit(2) and getrlimit(2) RLIMIT_NOFILE can have
     problems with the default limit on the number of simultaneous jobs, the
     value of -j.  Every job requires four open files.  These problems are
     usually seen with errors messages that say something like
           dccm[24448]: DCC: accept() returned invalid socket
     A fix is to use a smaller value for -j or to allow dccm to open more
     files.  Sendmail version 8.13 and later can be told to poll() instead of
     select with SM_CONF_POLL.  Some older versions of sendmail knew about
     FFR_USE_POLL.  One of the following lines in your devtools/Site/site.con-
     fig.m4 file can help:

           APPENDDEF(`conf_libmilter_ENVDEF', `-DSM_CONF_POLL')
           APPENDDEF(`conf_libmilter_ENVDEF', `-DFFR_USE_POLL')

     On many systems with sendmail 8.11.3 and preceding, a bug in the sendmail
     milter mechanism causes dccm to die with a core file when given a signal.

                               December 03, 2013

Man(1) output converted with man2html modified for the DCC $Date 2001/04/29 03:22:18 $