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Manual Reference Pages  -  RWGROUP (1)

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rwgroup - Tag similar SiLK records with a common next hop IP value



        {--id-fields=KEY | --delta-field=FIELD --delta-value=DELTA}
        [--objective] [--summarize] [--rec-threshold=THRESHOLD]
        [--note-add=TEXT] [--note-file-add=FILE] [--output-path=PATH]
        [--copy-input=PATH] [--compression-method=COMP_METHOD]
        [--plugin=PLUGIN [--plugin=PLUGIN ...]]
        [--python-file=PATH [--python-file=PATH ...]]
        [--pmap-file=MAPNAME:PATH [--pmap-file=MAPNAME:PATH ...]]

  rwgroup [--pmap-file=MAPNAME:PATH [--pmap-file=MAPNAME:PATH ...]]
        [--plugin=PLUGIN ...] [--python-file=PATH ...] --help

  rwgroup [--pmap-file=MAPNAME:PATH [--pmap-file=MAPNAME:PATH ...]]
        [--plugin=PLUGIN ...] [--python-file=PATH ...] --help-fields

  rwgroup --version


rwgroup reads sorted SiLK Flow records (c.f. rwsort(1)) from the standard input or from a single file name listed on the command line, marks records that form a group with an identifier in the Next Hop IP field, and prints the binary SiLK Flow records to the standard output. In some ways rwgroup is similar to rwuniq(1), but rwgroup writes SiLK flow records instead of textual output.

Two SiLK records are defined as being in the same group when the fields specified in the --id-fields switch match exactly and when the field listed in the --delta-field matches within the value given by the --delta-value switch. Either --id-fields or --delta-fields is required; both may be specified. A --delta-value must be given when --delta-fields is present.

The first group of records gets the identifer 0, and rwgroup writes that value into each record’s Next Hop IP field. The ID for each subsequent group is incremented by 1. The --group-offset switch may be used to set the identifier of the initial group.

The --rec-threshold switch may be used to only write groups that contain a certain number of records. The --summarize switch attempts to merge records in the same group to a single output record.

rwgroup requires that the records are sorted on the fields listed in the --id-fields and --delta-fields switches. For example, a call using

  rwgroup --id-field=2 --delta-field=9 --delta-value=3

should read the output of

  rwsort --field=2,9

otherwise the results are unpredictable.


Option names may be abbreviated if the abbreviation is unique or is an exact match for an option. A parameter to an option may be specified as --arg=param or --arg param, though the first form is required for options that take optional parameters.

At least one value for --id-field or --delta-field must be provided; rwgroup terminates with an error if no fields are specified.
--id-fields=KEY KEY contains the list of flow attributes (a.k.a. fields or columns) that must match exactly for flows to be considered part of the same group. Each field may be specified once only. KEY is a comma separated list of field-names, field-integers, and ranges of field-integers; a range is specified by separating the start and end of the range with a hyphen (-). Field-names are case insensitive. Example:


There is no default value for the --id-fields switch.

The complete list of built-in fields that the SiLK tool suite supports follows, though note that not all fields are present in all SiLK file formats; when a field is not present, its value is 0.
sIP,1 source IP address
dIP,2 destination IP address
sPort,3 source port for TCP and UDP, or equivalent
dPort,4 destination port for TCP and UDP, or equivalent
protocol,5 IP protocol
packets,pkts,6 packet count
bytes,7 byte count
flags,8 bit-wise OR of TCP flags over all packets
sTime,9 starting time of flow (seconds resolution)
duration,10 duration of flow (seconds resolution)
eTime,11 end time of flow (seconds resolution)
sensor,12 name or ID of sensor at the collection point
class,20 class of sensor at the collection point
type,21 type of sensor at the collection point
iType the ICMP type value for ICMP or ICMPv6 flows and zero for non-ICMP flows. Internally, SiLK stores the ICMP type and code in the dPort field, so there is no need have both dPort and iType or iCode in the sort key. This field was introduced in SiLK 3.8.1.
iCode the ICMP code value for ICMP or ICMPv6 flows and zero for non-ICMP flows. See note at iType.
icmpTypeCode,25 equivalent to iType,iCode in --id-fields. This field may not be mixed with iType or iCode, and this field is deprecated as of SiLK 3.8.1. As of SiLK 3.8.1, icmpTypeCode may no longer be used as the argument to --delta-field; the dPort field will provide an equivalent result as long as the input is limited to ICMP flow records.

Many SiLK file formats do not store the following fields and their values will always be 0; they are listed here for completeness:
in,13 router SNMP input interface or vlanId if packing tools were configured to capture it (see sensor.conf(5))
out,14 router SNMP output interface or postVlanId

SiLK can store flows generated by enhanced collection software that provides more information than NetFlow v5. These flows may support some or all of these additional fields; for flows without this additional information, the field’s value is always 0.
initialFlags,26 TCP flags on first packet in the flow
sessionFlags,27 bit-wise OR of TCP flags over all packets except the first in the flow
attributes,28 flow attributes set by the flow generator:
S all the packets in this flow record are exactly the same size
F flow generator saw additional packets in this flow following a packet with a FIN flag (excluding ACK packets)
T flow generator prematurely created a record for a long-running connection due to a timeout. (When the flow generator yaf(1) is run with the --silk switch, it will prematurely create a flow and mark it with T if the byte count of the flow cannot be stored in a 32-bit value.)
C flow generator created this flow as a continuation of long-running connection, where the previous flow for this connection met a timeout (or a byte threshold in the case of yaf).

Consider a long-running ssh session that exceeds the flow generator’s active timeout. (This is the active timeout since the flow generator creates a flow for a connection that still has activity). The flow generator will create multiple flow records for this ssh session, each spanning some portion of the total session. The first flow record will be marked with a T indicating that it hit the timeout. The second through next-to-last records will be marked with TC indicating that this flow both timed out and is a continuation of a flow that timed out. The final flow will be marked with a C, indicating that it was created as a continuation of an active flow.

application,29 guess as to the content of the flow. Some software that generates flow records from packet data, such as yaf, will inspect the contents of the packets that make up a flow and use traffic signatures to label the content of the flow. SiLK calls this label the application; yaf refers to it as the appLabel. The application is the port number that is traditionally used for that type of traffic (see the /etc/services file on most UNIX systems). For example, traffic that the flow generator recognizes as FTP will have a value of 21, even if that traffic is being routed through the standard HTTP/web port (80).

The following fields provide a way to label the IPs or ports on a record. These fields require external files to provide the mapping from the IP or port to the label:
sType,16 categorize the source IP address as non-routable, internal, or external and group based on the category. Uses the mapping file specified by the SILK_ADDRESS_TYPES environment variable, or the address_types.pmap mapping file, as described in addrtype(3).
dType,17 as sType for the destination IP address
scc,18 the country code of the source IP address. Uses the mapping file specified by the SILK_COUNTRY_CODES environment variable, or the country_codes.pmap mapping file, as described in ccfilter(3).
dcc,19 as scc for the destination IP
src-MAPNAME value determined by passing the source IP or the protocol/source-port to the user-defined mapping defined in the prefix map associated with MAPNAME. See the description of the --pmap-file switch below and the pmapfilter(3) manual page.
dst-MAPNAME as src-MAPNAME for the destination IP or protocol/destination-port.
dval These are deprecated field names created by pmapfilter that correspond to src-MAPNAME and dst-MAPNAME, respectively. These fields are available when a prefix map is used that is not associated with a MAPNAME.

Finally, the list of built-in fields may be augmented by the run-time loading of PySiLK code or plug-ins written in C (also called shared object files or dynamic libraries), as described by the --python-file and --plugin switches.

--delta-field=FIELD Specify a single field that can differ by a specified delta-value among the SiLK records that make up a group. The FIELD identifiers include most of those specified for --id-fields. The exceptions are that plug-in fields are not supported, nor are fields that do not have numeric values (e.g., class, type, flags). The most common value for this switch is stime, which allows records that are identical in the id-fields but temporally far apart to be in different groups. The switch takes a single argument; multiple delta fields cannot be specified. When this switch is specified, the --delta-value switch is required.
--delta-value=DELTA_VALUE Specify the acceptable difference between the values of the --delta-field. The --delta-value switch is required when the --delta-field switch is provided. For fields other than those holding IPs, when two consecutive records have values less than or equal to DELTA_VALUE, the records are considered members of the same group. When the delta-field refers to an IP field, DELTA_VALUE is the number of least significant bits of the IPs to remove before comparing them. For example, when --delta-field=sIP --delta-value=8 is specified, two records are the same group if their source IPv4 addresses belong to the same /24 or if their source IPv6 addresses belong to the same /120. The --objective switch affects the meaning of this switch.
--objective Change the behavior of the --delta-value switch so that a record is considered part of a group if the value of its --delta-field is within the DELTA_VALUE of the first record in the group. (When this switch is not specified, consecutive records are compared.)
--summarize Cause rwgroup to print (typically) a single record for each group. By default, all records in each group having at least --rec-threshold members is printed. When --summarize is active, the record that is written for the group is the first record in the group with the following modifications:
o The packets and bytes values are the sum of the packets and bytes values, respectively, for all records in the group.
o The start-time value is the earliest start time for the records in the group.
o The end-time value is the latest end time for the records in the group.
o The flags and session-flags values are the bitwise-OR of all flags and session-flags values, respectively, for the records in the group.

Note that multiple records for a group may be printed if the bytes, packets, or elapsed time values are too large to be stored in a SiLK flow record.

--plugin=PLUGIN Augment the list of fields by using run-time loading of the plug-in (shared object) whose path is PLUGIN. The switch may be repeated to load multiple plug-ins. The creation of plug-ins is described in the silk-plugin(3) manual page. When PLUGIN does not contain a slash (/), rwgroup will attempt to find a file named PLUGIN in the directories listed in the FILES section. If rwgroup finds the file, it uses that path. If PLUGIN contains a slash or if rwgroup does not find the file, rwgroup relies on your operating system’s dlopen(3) call to find the file. When the SILK_PLUGIN_DEBUG environment variable is non-empty, rwgroup prints status messages to the standard error as it attempts to find and open each of its plug-ins.
--rec-threshold=THRESHOLD Specify the minimum number of SiLK records a group must contain before the records in the group are written to the output stream. The default is 1; i.e., write all records. The maximum threshold is 65535.
--group-offset=IP Specify the value to write into the Next Hop IP for the records that comprise the first group. The value IP may be an integer, or an IPv4 or IPv6 address in the canonical presentation form. If not specified, counting begins at 0. The value for each subsequent group is incremented by 1.
--note-add=TEXT Add the specified TEXT to the header of the output file as an annotation. This switch may be repeated to add multiple annotations to a file. To view the annotations, use the rwfileinfo(1) tool.
--note-file-add=FILENAME Open FILENAME and add the contents of that file to the header of the output file as an annotation. This switch may be repeated to add multiple annotations. Currently the application makes no effort to ensure that FILENAME contains text; be careful that you do not attempt to add a SiLK data file as an annotation.
--copy-input=PATH Copy all binary input to the specified file or named pipe. PATH can be stdout to print flows to the standard output as long as the --output-path switch has been used to redirect rwgroup’s output.
--output-path=PATH Determines where the output of rwgroup is written. If this option is not given, output is written to the standard output.
--compression-method=COMP_METHOD Specify how to compress the output. When this switch is not given, output to the standard output or to named pipes is not compressed, and output to files is compressed using the default chosen when SiLK was compiled. The valid values for COMP_METHOD are determined by which external libraries were found when SiLK was compiled. To see the available compression methods and the default method, use the --help or --version switch. SiLK can support the following COMP_METHOD values when the required libraries are available.
none Do not compress the output using an external library.
zlib Use the zlib(3) library for compressing the output, and always compress the output regardless of the destination. Using zlib produces the smallest output files at the cost of speed.
lzo1x Use the lzo1x algorithm from the LZO real time compression library for compression, and always compress the output regardless of the destination. This compression provides good compression with less memory and CPU overhead.
best Use lzo1x if available, otherwise use zlib. Only compress the output when writing to a file.
--site-config-file=FILENAME Read the SiLK site configuration from the named file FILENAME. When this switch is not provided, rwgroup searches for the site configuration file in the locations specified in the FILES section.
--help Print the available options and exit. Specifying switches that add new fields or additional switches before --help will allow the output to include descriptions of those fields or switches.
--help-fields Print the description and alias(es) of each field and exit. Specifying switches that add new fields before --help-fields will allow the output to include descriptions of those fields.
--version Print the version number and information about how SiLK was configured, then exit the application.
--pmap-file=PATH Instruct rwgroup to load the mapping file located at PATH and create the src-MAPNAME and dst-MAPNAME fields. When MAPNAME is provided explicitly, it will be used to refer to the fields specific to that prefix map. If MAPNAME is not provided, rwgroup will check the prefix map file to see if a map-name was specified when the file was created. If no map-name is available, rwgroup creates the fields sval and dval. Multiple --pmap-file switches are supported as long as each uses a unique value for map-name. The --pmap-file switch(es) must precede the --id-fields switch. For more information, see pmapfilter(3).
--python-file=PATH When the SiLK Python plug-in is used, rwgroup reads the Python code from the file PATH to define additional fields that can be used as part of the group key. This file should call register_field() for each field it wishes to define. For details and examples, see the silkpython(3) and pysilk(3) manual pages.


rwgroup requires sorted data. The application works by comparing records in the order that the records are received (similar to the UNIX uniq(1) command), odd orders will produce odd groupings.


In the following example, the dollar sign ($) represents the shell prompt. The text after the dollar sign represents the command line. Lines have been wrapped for improved readability, and the back slash (\) is used to indicate a wrapped line.

As a rule of thumb, the --id-fields and --delta-field parameters should match rwsort(1)’s call, with --delta-field being the last parameter. A call to group all web traffic by queries from the same addresses (field=2) within 10 seconds (field=9) of the first query from that address will be:

 $ rwfilter --proto=6 --dport=80 --pass=stdout                  \
   | rwsort --field=2,9                                         \
   | rwgroup --id-field=2 --delta-field=9 --delta-value=10      \


PYTHONPATH This environment variable is used by Python to locate modules. When --python-file is specified, rwgroup must load the Python files that comprise the PySiLK package, such as silk/ If this silk/ directory is located outside Python’s normal search path (for example, in the SiLK installation tree), it may be necessary to set or modify the PYTHONPATH environment variable to include the parent directory of silk/ so that Python can find the PySiLK module.
SILK_PYTHON_TRACEBACK When set, Python plug-ins will output traceback information on Python errors to the standard error.
SILK_COUNTRY_CODES This environment variable allows the user to specify the country code mapping file that rwgroup uses when computing the scc and dcc fields. The value may be a complete path or a file relative to the SILK_PATH. See the FILES section for standard locations of this file.
SILK_ADDRESS_TYPES This environment variable allows the user to specify the address type mapping file that rwgroup uses when computing the sType and dType fields. The value may be a complete path or a file relative to the SILK_PATH. See the FILES section for standard locations of this file.
SILK_CLOBBER The SiLK tools normally refuse to overwrite existing files. Setting SILK_CLOBBER to a non-empty value removes this restriction.
SILK_CONFIG_FILE This environment variable is used as the value for the --site-config-file when that switch is not provided.
SILK_DATA_ROOTDIR This environment variable specifies the root directory of data repository. As described in the FILES section, rwgroup may use this environment variable when searching for the SiLK site configuration file.
SILK_PATH This environment variable gives the root of the install tree. When searching for configuration files and plug-ins, rwgroup may use this environment variable. See the FILES section for details.
SILK_PLUGIN_DEBUG When set to 1, rwgroup prints status messages to the standard error as it attempts to find and open each of its plug-ins. In addition, when an attempt to register a field fails, rwgroup prints a message specifying the additional function(s) that must be defined to register the field in rwgroup. Be aware that the output can be rather verbose.


/usr/local/share/address_types.pmap Possible locations for the address types mapping file required by the sType and dType fields.
/usr/local/share/silk.conf Possible locations for the SiLK site configuration file which are checked when the --site-config-file switch is not provided.
/usr/local/share/country_codes.pmap Possible locations for the country code mapping file required by the scc and dcc fields.
/usr/local/lib/ Directories that rwgroup checks when attempting to load a plug-in.


rwfilter(1), rwfileinfo(1), rwsort(1), rwuniq(1), addrtype(3), ccfilter(3), pmapfilter(3), pysilk(3), silkpython(3), silk-plugin(3), sensor.conf(5), uniq(1), silk(7), yaf(1), dlopen(3), zlib(3)
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SiLK RWGROUP (1) 2016-04-05

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