.\" --8-LICENSE--
.\"
.\" $Revision: 1.110 $
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.Dd March 22, 2024
.ds volume-ds-DCC Distributed Checksum Clearinghouse
.Dt cdcc 8 DCC
.Os " "
.Sh NAME
.Nm cdcc
.Nd Control Distributed Checksum Clearinghouse
.Sh SYNOPSIS
.Nm cdcc
.Op Fl VBdq
.Op Fl h Ar homedir
.Op Fl c Ar ids
.Op Ar op1 op2 ... Op Ar -
.Sh DESCRIPTION
.Nm Cdcc
is used to clear, control, and query the control file used
by Distributed Checksum Clearinghouse
clients such as
.Xr dccm 8 .
The host names, UDP port numbers, IDs, and passwords local clients use
to talk to servers as well as IP addresses, round trip times, and other
information are contained in the
.Pa map
file.
While
.Nm
is set-UID, it uses the real UID only when accessing the
.Pa map
file.
It refuses to display sensitive information such as passwords
unless the real UID is the same as the effective UID.
Note that
.Nm
needs to be set to a UID that can read and write the
.Pa map
file, but that UID need not be 0.
.Pp
.Nm Cdcc
is also used to send commands to DCC servers to tell them
to stop, reload their lists of DCC IDs, turn on tracing, and so forth.
.Pp
Many commands sent to DCC servers require a numeric DCC ID
and a password recognized by the server.
A DCC password is a 1-32 character string that does not contain
blank, tab, newline or carriage return characters.
The ID is specified with the
.Ic id
operation.
If
.Nm cdcc
is run with a real UID that can read the
.Pa ids
file and a password is not specified
(see the
.Ic password
operation),
then the current password for the specified ID in the
.Pa ids
file will be used.
If no
.Pa ids
file is available and a password and DCC ID are not specified,
.Nm
uses the anonymous DCC client-ID.
DCC servers do not expect a password from clients using the
anonymous client-ID,
but they also won't honor control requests.
.Pp
Operations that modify the
.Pa map
file can only be performed when
the real UID is sufficient to modify the file directly.
Trying to perform an operation that requires a password without
specifying a server-ID or without using a UID that can access the
.Pa ids
file produces an error message complaining
about a "privileged operation."
.Pp
Commands and operations are read from the command line or from stdin.
A series of
.Ar op1 op2 ...
operations followed a
.Ar -
(a dash) causes operations to be read from stdin after the command line
operations are processed.
Semi-colons or newlines separate commands in UNIX command-line "words,"
as well as when commands are read from stdin.
Since each command line operation must be a shell "word," quotes are
often required as in
.Bd -ragged -offset indent
% cdcc
.Qq load map.txt
.Ed
or
.Bd -ragged -offset indent
% cdcc
.Qq host localhost;info
stats
.Ed
.Ss OPTIONS
The following options are available:
.Bl -tag -width 3n
.It Fl V
displays the version of the DCC controller.
Two or more
.Fl V
options show the options with which it was built.
.It Fl B
sends error messages from the DCC server to both stderr and stdout instead
of only stderr.
.It Fl d
enables debugging output from the DCC client software.
Additional
.Fl d
options increase the number of messages.
See the
.Ic debug
command.
.It Fl q
quiets initial complaints about the map file
and some messages about successful commands.
See the
.Ic quiet
command.
.It Fl h Ar homedir
overrides the default DCC home directory,
.Pa @prefix@ .
See the
.Ic homedir
operation.
.It Fl c Ar ids
specifies the file containing DCC IDs and passwords known by
local DCC servers.
An
.Pa ids
file that can be read by others cannot be used.
The format of the
.Pa ids
file is described in
.Xr dccd 8 .
.It Ar op1 op2 ...
are operations or commands such as "id\ 100;\ stop".
Commands or operations specified on the command line are performed
before the first interactive request.
The last command can be
.Ar "-"
to specify that additional commands should be read from stdin.
.El
.Ss OPERATIONS
Local operations include the following:
.Bl -tag -width info
.It Ic help Op Ar command
lists information about one or all available commands and operations.
.It Ic exit
stops
.Nm
.It Ic grey Op Ar on | off
switches between DCC and greylist servers.
.It Ic homedir Op Ar path
displays or specifies the DCC home directory,
.Pa @prefix@ .
.It Ic file Op Ar map
displays or specifies the name or path of the map file.
The string "-" specifies the default file
.Pa @prefix@/map .
.It Ic new map Op Ar map
creates a new, empty file for DCC server host names,
port numbers, passwords, and so forth.
There must not already be a file of the same name.
The default is
.Pa map
in the DCC home directory.
.It Ic delete Ar host Ns Xo
.Ns Op , Ns Ar port
.Xc
deletes the entry in the
.Pa map
file for
.Ar host
and UDP
.Ar port.
If greylist mode has been set with the
.Ic grey\ on
command,
the entry for the grelist server at
.Ar host
is deleted.
.It Ic add Ar host Ns Xo
.Ns Op , Ns Ar port
.Op Ar RTT+adj Ns | Ns Ar RTT-adj
.Op Ar Greylist
.Op Ar client-ID Op password
.Xc
adds an entry to the
.Pa map
file.
The
.Ar port
can be "-" to specify the default DCC server port number.
.Pp
An adjustment to the round trip time is
between -2000 and +2000 and follows the string
.Ar RTT .
The adjustment is added to the average measured round trip time when
the DCC client software picks the "nearest" DCC server, or the server
with the smallest RTT.
If an IP address is mentioned more than once in the list of servers,
for example because it is among the addresses for more than one server name,
conflicts among RTT adjustments are resolved by picking
the adjustment with the largest absolute value.
.Pp
.Ar Greylist
marks an entry for a greylist servers.
.Ar Greylist
is assumed if greylist mode has been set with
the
.Ic grey\ on
command,
See
.Xr dccd 8 .
.Pp
If both the client-ID and the password are absent,
the anonymous client-ID, 1, is used.
The string
.Ar anon
is equivalent to the anonymous client-ID.
A null password string is assumed if the password is missing
and the client-ID is 1 or also missing.
.It Ic load Ar info-file
loads the current parameter file with the host names, port numbers, IDs, and
passwords in
.Ar info-file .
Standard input is understood if
.Ar info-file
is "-".
.Pp
A suitable file can be created with the
.Ic info
operation.
It consists of ignored blank or comment lines starting with '#' and
other lines in the same format as the arguments to the
.Ic add
operation.
Note that output of the
.Ic info
command will lack passwords unless it is run by a privileged user.
.It Ic host Op Ar hostname
specifies the host name of the DCC server to which commands should be sent.
If
.Ar hostname
is "-", the current default DCC server is chosen.
.It Ic port Op Ar port
specifies the UDP port number of the DCC server to which commands should
be sent.
The default is 6277 or 6276 depending on the setting of the greylist
mode controlled with the
.Ic grey
command.
.It Ic password Ar secret
specifies the password with which to sign commands sent to the DCC
server specified with the
.Ic server
and
.Ic port
operations.
.It Ic id Op Ar ID
specifies or displays the numeric DCC ID for commands sent to the DCC
server specified with the
.Ic server
and
.Ic port
operations.
If no password is specified with the
.Ic password
command,
the password is sought in the local
.Pa ids .
.It Ic info Op Fl N
displays information about the connections to DCC servers.
It starts with the current date and name of the current
.Ar map
file or
says that
.Nm
is using the implicit file created with the
.Ic server
and
.Ic port
operations.
It then says when host names will next be resolved into IP addresses,
the smallest round trip time to the IP addresses of known DCC servers.
The host name, UDP port number (or dash if it is the default),
DCC client-ID, and password (if
.Nm
is used by a privileged user)
are shown in one line per configured DCC server.
.Pp
The currently preferred IP address is indicated by an asterisk.
The "brand" of the server, its DCC ID, and its IP address
are displayed in one line per IP address.
The performance of the server at each IP address in the most recent
32 operations is displayed in a second line.
The second line ends with the measured delay imposed by the server on requests
with this client's ID.
.Pp
.Fl N
displays the reverse DNS name of each server.
.It Ic RTT Op Fl N
measures the round trip time to the DCC servers.
It does this by discarding accumulated information and forcing
a probe of all listed server IP addresses.
.Pp
.Em Beware
that when run with sufficient privilege, the
.Ic RTT
operation is like the
.Ic info
and
.Ic load
operations and displays cleartext passwords.
.Pp
.Fl N
displays the reverse DNS name of each server.
.It Ic debug Xo
Op Ar on | off | TTL=x
.Xc
increases or decreases debugging information from the DCC client software
or sets the IP TTL on queries to the server.
See
.Fl d .
.Pp
Some operating systems do not include the functions required to change the
IP TTL.
Others include the required functions
but have no apparent effect.
.It Ic quiet Op Ar on | off
makes commands more quiet or more verbose.
.It Ic IPv6 Op Ar on | off | only
clients to try to use IPv6 and IPv4, IPv4 only, or IPv6 only.
.It Ic SOCKS Op Ar on | off
tell DCC to use the SOCKS5 protocol
if they have been built with a SOCKS library.
The socks library linked with the DCC client must be configured appropriately,
often including knowing which DCC servers must be connected via the
SOCKS proxy and which can be reached directly.
DCC clients use SOCKS functions such as Rsendto() with all or no servers
depending on the setting of this switch.
.It Ic src Op Ar - |  Xo
.Sm off
.Ar IPaddress
.Op Ar ,IPv6address
.Sm on
.Xc
displays or configures the source address of DCC client requests.
.Ar -
removes the explicit configuration of the source, while
.Ar IPaddress
or
.Ar IPaddress,IPv6address
sets it.
This makes sense only on multi-homed hosts.
It can be useful for passing firewalls.
.El
.Pp
.Ss DCC SERVER COMMANDS
Commands that can be sent to a DCC server include the following.
Most of the commands must be used with the server's
.Ar ID
specified with the
.Ic id
command.
The specified ID is included in the commands sent to the server
The command itself is digitally signed with the first password associated
with the ID in the
.Pa ids
file.
The server requires that the signature match one of the passwords associated
with the ID in its
.Pa ids
file.
.Bl -tag -width xxx
.It Ic delck type hex1 hex2 hex3 hex4
asks the server to delete the
.Ar type
checksum with value
.Ar hex1 hex2 hex3 hex4 .
The type and checksum values can be found in
.Xr dccproc 8
and
.Xr dccm 8
log files
or computed with
.Em dccproc Fl QC .
.Pp
There are very few situations where it makes sense to bother to delete
checksums.
For example, mail that was accidentally reported with a target
count of "MANY" is either private and so will not be seen by other
people and so will not be affected, or it is bulk and its source
so must have already been whitelisted by recipients.
.It Ic stats Op Ar all | clear
displays current status and statistics from the current DCC server
or for
.Ar all
known DCC servers.
The server's counters will be cleared after they are displayed
when the server's ID has been specified with the
.Ic id Ar ID
operation.
.It Ic clients Xo
.Op Fl nsiaVAK
.Op Fl I Ar id
.Op Ar max Op Ar thold
.Op Ar addr Ns Op Ar /prefix
.Xc
display some of the clients recently seen by the server.
.Bl -hang -compact -width xxxxx
.It Fl n
display only the IP addresses and not the names of clients.
.It Fl s
sort the clients by the number of requests they have made.
.It Fl i
count clients with the same client-ID as single entities.
.It Fl I Ar id
display information only about clients using client-ID
.Ar id .
.It Fl a
produce 24 hour average numbers of requests.
.It Fl A
display only anonymous clients.
.It Fl K
display only clients using client-IDs other than the anonymous ID of 1.
.It Fl V
include the DCC protocol versions used by clients.
.It Ar max
display only the
.Ar max
most recent clients.
.It Ar max Ar thold
display the most recent
.Ar max
clients that have made at least
.Ar thold
requests.
.It Ar addr Ns Op Ar /prefix
restricts the results to the DCC client with that IP address or
clients with addresses in that block of addresses.
Individual clients in a blacklisted block of addresses
in the server's
.Pa @prefix@/blacklist
file are not displayed unless explicitly requested by address or address block.
.El
.Pp
Clients with IDs marked with an asterisk (*) used the wrong password for
that client-ID.
.Pp
The mechanism that implements this command involves
asking the DCC server for the first approximately 100 clients, then
the second about 100, and so on,
If entries change position in the complete list maintained by the server
between requests,
the displayed list will have duplicate or missing entries.
Only clients since the last use of
.Ic stats clear
are displayed.
.It Ic stop
tells the DCC server to exit.
.It Ic system stop
tells the DCC server to exit so that the operating system can be shut down.
This tells the DCC server on some systems to delete the dcc_db.hash file
to speed system shut down.
The file will be rebuilt automatically by
.Nm dbclean
when the DCC server is restarted.
.It Ic clean stop
tells the DCC server to exit after applying fsync() to the database.
.It Ic reload IDs
tells the local DCC server to reload its DCC
.Pa ids
file immediately.
This command is not strictly needed.
Every several minutes, the DCC server notices if the file has been changed
and automatically reads it.
.It Ic flood check
tells the DCC server to check for changes in the
.Pa flod
file and try to restart any of the streams to peers that are broken.
.It Ic flood shutdown
tells the DCC server to cleanly stop flooding checksums to and from peers.
The server will wait for sending and receiving peers to agree to stop.
Each
.Ic flood shutdown
or
.Ic flood halt
request increases a count of reasons why the server should not
flood checksums.
.It Ic flood halt
tells the DCC server to abruptly stop flooding checksums to and from peers.
.It Ic flood rewind Ar server-ID
tells the DCC server to ask its peer with
.Ar server-ID
to rewind and resend its stream of checksums.
.It Ic flood ffwd in Ar server-ID
tells the DCC server to ask its peer to "fast forward" or skip to
the end of the incoming flood.
.It Ic flood ffwd out Ar server-ID
tells the DCC server to "fast forward" or skip to the current end
of the flood to its peer.
.It Ic flood resume
tells the DCC server to reduce the number of reasons to
not flood checksums increased by
.Ic flood shutdown
and
.Ic flood halt.
When the number of reasons reaches zero,
the server tries to resume flooding.
.It Ic flood list
displays the list of current incoming and outgoing floods.
Each line contains the server-ID of the peer,
the IP address and port used for the outgoing flood,
the address for the incoming flood if different,
and the host name.
Only the server-IDs of flooding peers are disclosed with the server's ID.
.It Ic flood stats Xo
.Op Ic clear
.No {
.Ar server-ID | all
.No }
.Xc
displays counts of checksum reports sent and received by the current
flooding connections to and from
.Ar server-ID
or
.Ar all
flooding connections
and then optionally clears the counts.
.It Ic DB clean
is used by
.Nm dbclean
to tell the server that the database expiration has begun.
.It Ic DB new
is used by
.Nm dbclean
to tell the server that the database cleaning is complete.
.It Ic flush cache
tells the server to flush its cache and to keep it clean.
.It Ic cache ok
tells the server to resume normal operations after
.Ic flush cache .
.It Ic clock check
asks the DCC server to say how much its clock differs from the local clock.
.It Ic clock kludge +/-seconds
adjusts the timestamps in server commands to make it possible to
control servers with inaccurate clocks.
.It Ic trace Ar default
turns on
.Ar ANON
and
.Ar CLNT
tracing
and turns off all others.
.It Ic trace Ar mode {on|off}
turns the server's tracing
.Ar mode
on or off.
.Ar Mode
must be one of:
.Bl -tag -width FLOOD2 -offset 2n -compact
.It Ar ADMN
administrative requests from
.Nm
.It Ar ANON
errors by anonymous clients
.It Ar CLNT
errors by authenticated clients
.It Ar RLIM
rate-limited messages
.It Ar QUERY
all queries and reports
.It Ar RIDC
messages concerning the report-ID cache that is used
to detect duplicate reports from clients
.It Ar FLOOD1
messages about inter-server flooding connections
.It Ar FLOOD2
messages about flooded reports
.It Ar IDS
unknown server-IDs in flooded reports
.It Ar BL
blacklisted clients
.It Ar DB
odd database events
.It Ar WLIST
reports of whitelisted checksums from authenticated, not anonymous DCC clients
.El
.El
.Pp
.Nm
exits with 0 on success,
and >0 if an error occurs in operations specified on the command line.
.Sh FILES
.Bl -tag -width @prefix@ -compact
.It Pa @prefix@
default DCC home directory unless changed by the
.Ar homedir
operation.
.It Pa map
memory mapped file in the home DCC home directory of server host names,
port numbers,
passwords, measured round trip times (RTT), and so forth.
.It Pa ids
list of IDs and passwords, as described in
.Xr dccd 8 .
It is only required by systems running the DCC server,
but is used by
.Nm
if available.
.El
.Sh SEE ALSO
.Xr dbclean 8 ,
.Xr dcc 8 ,
.Xr dccd 8 ,
.Xr dblist 8 ,
.Xr dccifd 8 ,
.Xr dccm 8 ,
.Xr dccproc 8 ,
.Xr dccsight 8 .
.Sh HISTORY
Implementation of
.Nm
was started at Rhyolite Software in 2000.
This document describes version RHYOLITE_VERSION.