Monitoring for Large-Scale Networks

SiLK

sensor.conf

NAME

sensor.conf - Sensor Configuration file for rwflowpack and flowcap

DESCRIPTION

As part of collecting flow data, the rwflowpack(8) and flowcap(8) daemons need to know what type of data they are collecting and how to collect it (e.g., listen on 10000/udp for NetFlow v5; listen on 4740/tcp for IPFIX). In addition, the rwflowpack daemon needs information on how to categorize the flow: for example, to label the flows collected at a border router as incoming or outgoing. The Sensor Configuration file, sensor.conf, contains this information, and this manual page describes the syntax of the file (see "SYNTAX" below) and provides some example configurations (see "EXAMPLES").

The sensor.conf file may have any name, and it may reside in any location. The name and location of the file is specified by the --sensor-configuration switch to rwflowpack and flowcap.

The Sensor Configuration File defines the following concepts:

probe: A probe specifies a source for flow data. The source could be a port on which flowcap or rwflowpack collects NetFlow or IPFIX data from a flow generator such as a router or the yaf software (http://tools.netsa.cert.org/yaf/). In rwflowpack, the source can be a directory to periodically poll for files containing NetFlow v5 PDUs, IPFIX records, or SiLK Flow records. When defining a probe, you must specify a unique name for the probe and the probe's type.
group: A group is a named list that contains one of the following: CIDR blocks, the names of IPset files, or integers representing SNMP interfaces or VLAN identifiers. The use of groups is optional; the primary purpose of a group is to allow the administrator to specify a commonly used list (such as the IP space of the network being monitored) in a single location.
sensor: A sensor represents a logical collection point for the purposes of analysis. The sensor contains configuration values that rwflowpack uses to categorize each flow record depending on how the record moves between networks at the collection point. Since the sensors and the categories (known as flowtypes or as class/type pairs) are also used for analysis, they are defined in the Site Configuration file, described in silk.conf(5). The Sensor Configuration file maps sensors to probes and specifies the rules required to categorize the data. Usually one sensor corresponds to one probe; however, a sensor may be comprised of multiple probes, or the flow data collected at a single probe may be handled by multiple sensors.

The next section of this manual page describes the syntax of the sensor.conf file.

Using the syntax to configure a sensor requires knowledge of the packing logic that rwflowpack is using. The packing logic is the set of rules that rwflowpack uses to assign a flowtype to each record it processes. The default packing logic is for the twoway site, which is described in the packlogic-twoway(3) manual page. Additional packing logic rules are available (e.g., packlogic-generic(3)).

The last major section of this document is "EXAMPLES" where several common configurations are shown. These examples assume rwflowpack is using the packing logic from the twoway site.

SYNTAX

When parsing the Sensor Configuration file, blank lines are ignored. At any location in a line, the character # indicates the beginning of a comment, which continues to the end of the line. These comments are ignored.

All other lines begin with optional leading whitespace, a command name, and one or more arguments to the command. Command names are a sequence of non-whitespace characters, not including the character #. Arguments are textual atoms: any sequence of non-whitespace, non-# characters, including numerals and punctuation.

There are four contexts for commands: top-level, probe block, group block, and sensor block. The probe block, group block, and sensor block contexts are used to describe individual features of probes, groups, and sensors, respectively.

The valid commands for each context are described below.

Top-Level Commands

In addition to the commands to begin a probe, group, or sensor block, the top-level context supports the following command:

include "path": The include command is used to include the contents of another file whose location is path. This may be used to separate large configurations into logical units. The argument to include must be a double-quoted string.

Probe Block

With the exception of the probe command, the commands listed below are accepted within the probe context. Within a probe block, one and only one of the following must be specified: listen-on-port to listen on a network socket, poll-directory to poll a directory for files, read-from-file to read a single file, or listen-on-unix-socket to listen on a UNIX domain socket. These commands are described below.

probe probe-name probe-type

The probe command is used in the top-level context to begin a new probe block which continues to the end probe command. The arguments to the probe command are the name of the probe being defined and the probe type. The probe-name must be unique among all probes. It must begin with a letter, and it may not contain whitespace characters or the slash character (/). When a probe is associated with a single sensor, it is good practice to give the probe the same name as the sensor. The probe-type must be one of the following:

netflow-v5: This probe processes NetFlow v5 protocol data units (PDU) that the daemon reads from a UDP port or from a file. NetFlow may be generated by a router or by software that reads packet capture (pcap(3)) data and generates NetFlow v5 records.
netflow: This is an alias for netflow-v5 for backwards compatibility. This alias is deprecated, and it may be removed in a future release.
ipfix: An IPFIX probe processes Internal Protocol Flow Information eXchange records that the daemon reads over the network from an IPFIX source such as yaf(1). An IPFIX probe can also poll a directory for files generated by the yaf program. To support IPFIX probes, SiLK must be built with support for the external library libfixbuf, version 1.7.0 or later. Both yaf and libfixbuf are available from http://tools.netsa.cert.org/.
netflow-v9: This probe processes NetFlow v9 protocol data units (PDU) that the daemon reads from a UDP port from a router. To support NetFlow v9 probes, SiLK must be built with support for the external library libfixbuf, version 1.7.0 or later.
sflow: This probe processes sFlow v5 records that the daemon reads from a UDP port. To support sFlow probes, SiLK must be built with support for the external library libfixbuf, version 1.7.0 or later. Since SiLK 3.9.0.
silk: A SiLK probe processes the records contained in SiLK Flow files created by previous invocations of rwflowpack. The flows will be completely re-packed, as if they were just received over the network. The sensor and flowtype values in each flow will be ignored. Note that SiLK usually removes the SNMP interfaces from its flow records, and it is likely that you will be unable to use the SNMP interfaces to pack the flows.

end probe

The end probe command ends the definition of a probe. Following an end probe command, top-level commands are again accepted.

listen-on-port port

This command configures the probe to accept flow records over the network, and port specifies the network port number where the probe should listen for flow data. The protocol command is required when listen-on-port is specified, and the listen-as-host and accept-from-host commands are optional. Multiple probes may use the same value for port as long as the probes are the same type and the accept-from-host command is specified in each probe block. Probes of different types may not bind to the same port, meaning the combination of the following three values must be different: listen-on-port, protocol, and listen-as-host. When listening to IPFIX data from yaf, this is the value specified to yaf's --ipfix-port switch. When listening to NetFlow from a Cisco router, this is the port that was specified to the Cisco IOS command

ip flow-export [ip-address] [port]

protocol { tcp | udp }

This command, required when listen-on-port is given, specifies whether the port is a tcp or udp port. IPFIX probes support both types; the only permitted value for all other probe types is udp. When listening to IPFIX data from yaf, this is the value specified to yaf's --ipfix switch.

accept-from-host host-name [host-name...]

This optional command specifies the hosts that are allowed to connect to the port where the probe is listening. The argument is a list of IP addresses and/or hostnames separated by whitespace and/or a comma. When this command is not present, any host may connect. The command may only be specified when the listen-on-port command is also present. When multiple probes use the same listen-on-port, protocol, and listen-as-host values, the accept-from-host switch must be used so that rwflowpack may assign incoming records to a specified probe. When listening for NetFlow, this attribute would be the IP address of the router as seen from the machine running rwflowpack or flowcap. (Prior to SiLK 3.10.1, the accept-from-host command accepted only a single argument.)

listen-as-host host-name

This optional command is used on a multi-homed machine to specify the address the probe should listen on (bind(2) to). Its value is the name of the host or its IP address. If not present, the program will listen on all the machine's addresses. The command may only be specified when the listen-on-port command is also present. For listening to NetFlow, the value would be the ip-address that was specified to the Cisco IOS command

ip flow-export [ip-address] [port]

listen-on-unix-socket path-to-unix-socket

The value contains the path name to a UNIX domain socket where the flow generator writes its data. The parent directory of path-to-unix-socket must exist. Multiple probes may not use the same path-to-unix-socket.

poll-directory directory-path

When this command is given, rwflowpack will periodically poll the directory-path to look for files to process. flowcap will exit with an error if you attempt to use probes that contain this command since flowcap does not support reading data from files. Multiple probes may not use the same directory-path. When polling the directory, zero length files and files whose name begin with a dot (.) are ignored. This command may be used with the following probe types:

For SiLK probes, each file must be a valid SiLK Flow file.
IPFIX probes can process files created by the yaf program.
A NetFlow v5 probe will process files containing NetFlow v5 PDUs. The format of these files is specified in the description of the read-from-file command.

read-from-file dummy-value

When this command is given, rwflowpack will read NetFlow v5 records from the file specified by the --netflow-file command line switch. The value to the read-from-file command is completely ignored, and we recommend you use /dev/null as the value. flowcap will exit with an error if you attempt to use probes that contain this command since flowcap does not support reading data from files. The format of a NetFlow v5 file is that the file's length should be an integer multiple of 1464 bytes, where 1464 is the maximum length of the NetFlow v5 PDU. Each 1464 block should contain the 24-byte NetFlow v5 header and space for thirty 48-byte flow records, even if fewer NetFlow records are valid. rwflowpack will accept NetFlow v5 files that have been compressed with the gzip(1) program.

log-flags { none | { all | bad | default | firewall-event | missing | record-timestamps | sampling | show-templates | ... } }

This optional command accepts a comma- and/or space-separated list of names that specify which messages to log for this probe. If not specified, the default is default, which is equivalent to bad, missing, sampling. The possible values are:

all: Log everything.
bad: Write messages about an individual NetFlow v5 record where the packet or octet count is zero, the packet count is larger than the octet count, or the duration of the flow is larger than 45 days.
default: Enable the following values: bad, missing, sampling. This is the default value. Since SiLK 3.10.0. (Prior to SiLK 3.10.0, all was the default.)
firewall-event: When the firewall-event quirks flag is set and the probe is processing NetFlow v9 or IPFIX, write messages about records that are ignored because the firewall event information element on the record is something other than flow deleted or flow denied. Since SiLK 3.8.1.
missing: Examine the sequence numbers of NetFlow v5 packets and write messages about missing and out-of-sequence packets. (You may suppress messages regarding out-of-sequence NetFlow v9 or IPFIX packets for all probes by setting the SILK_LIBFIXBUF_SUPPRESS_WARNINGS environment variable.)
none: Log nothing. It is an error to combine this value with any other.
record-timestamps: Log the timestamps that appear on each record. This produces a lot of output, and it is primarily used for debugging. Since SiLK 3.10.0.
sampling: Write messages constructed by parsing the NetFlow v9 Options Templates that specify the sampling algorithm (when samplingAlgorithm and samplingInterval IEs are present) or flow sampler mode (when flowSamplerMode and flowSamplerRandomInterval IEs are present). Since SiLK 3.8.0.
show-templates: Write messages to the log file describing each IPFIX template that is read by this file-base or TCP probe. (UDP probes must still rely on the SILK_IPFIX_PRINT_TEMPLATES environment variable.) The message contains embedded new lines, with the template ID and domain on the first line, and each of the template's elements on the following lines. Each element is described by its name, its IE number with the private enterprise number if any, and its length in the template. Scope elements in options templates are marked. The format is that described in Section 10.2 of RFC7013. Since SiLK 3.19.0.

interface-values { snmp | vlan }

This optional command specifies the values that should be stored in the input and output fields of the SiLK Flow records that are read from the probe. If this command is not given, the default is snmp. Note that NetFlow v5 probes only support snmp.

snmp: Store the index of the network interface card (ifIndex) where the flows entered and left the router, respectively.
vlan: Store the VLAN identifier for the source and destination networks, respectively. If only one VLAN ID is available, input is set to that value and output is set to 0.

This setting does not affect whether rwflowpack(8) stores the input and output fields to its output files. Storage of those fields is controlled by rwflowpack's --pack-interfaces switch.

quirks { none | { firewall-event | missing-ips | nf9-out-is-reverse | nf9-sysuptime-seconds | zero-packets ... } }

This optional command is used to indicate that special (or quirky) handling of the incoming data is desired. The value none disables all quirks, and that is the default setting. If the value is not none, it may be a list of one or more of the values specified below separated by commas and/or spaces. Since SiLK 3.8.0.

firewall-event: Enable checking for firewall event information elements (IEs) when processing IPFIX or NetFlow v9 flow records. This quirk must be enabled when collecting data from a Cisco ASA. The IPFIX firewallEvent IE is 233. The Cisco elements are NF_F_FW_EVENT (IE 40005) and NF_F_FW_EXT_EVENT (IE 33002). When this quirk is active, firewall events that match the value 2 (flow deleted) are categorized as normal flows, firewall events that match the value 3 (flow denied) are usually put into one of non-routed types (e.g., innull, outnull, see packlogic-twoway(3) and packlogic-generic(3) for details), and all other firewall events values are dropped. (Note that a log message is generated for these dropped records; to suppress these messages, use the log-flags command.) When this quirk is not provided, SiLK handles these records normally, which may result in duplicate flow records. (Prior to SiLK 3.8, SiLK dropped all flow records that contained a firewall event IE.) Since SiLK 3.8.0.
missing-ips: Store a flow record even when the record's NetFlow v9/IPFIX template does not contain IP addresses. One change in SiLK 3.8.0 was to ignore flow records that do not have a source and/or destination IP address; this quirk allows one to undo the effect of that change. Since SiLK 3.8.1.
nf9-out-is-reverse: Change handling of the OUT_BYTES and OUT_PKTS information elements to match that in libfixbuf prior to 1.8.0. Specifically, treat information elements 23 and 24 (OUT_BYTES and OUT_PKTS in RFC3954) as reverseOctetDeltaCount and reversePacketDeltaCount, respectively. Starting with libfixbuf-1.8.0, those NetFlow v9 elements are mapped to postOctetDeltaCount and postPacketDeltaCount, respectively. Since SiLK 3.17.2.
nf9-sysuptime-seconds: Work around an issue with NetFlow v9 records created by some middleboxes (e.g., SonicWall) where the sysUpTime field in the packet header is reported in seconds instead of in milliseconds. The incorrect units cause the time stamps on flow records to be future dated. In addition, adjust the time fields on single packet flow records. Since SiLK 3.14.0.
none: Do not enable any quirks.
zero-packets: Enable support for flow records either that do not contain a valid packets field, such as those from the Cisco ASA series of routers, or that have an unusually large bytes-per-packet ratio. When this quirk is active, SiLK sets the packet count to 1 when the incoming IPFIX or NetFlow v9 flow record has a the packet count if 0. This quirk may modify the file format used by rwflowpack for IPv4 records in order to support large byte-per-packet ratios. Since SiLK 3.8.0.

priority value

This optional command is deprecated. It exists for backwards compatibility and will be removed in the next major release.

To summarize the probe types and the input they can accept:

Probe Type   Berkeley    Directory  UnixDomain    Single
              Socket      Polling     Socket       File
==========  ==========  ==========  ==========  ==========
ipfix        tcp/udp        yes
netflow-v5     udp          yes                    yes
netflow-v9     udp
sflow          udp
silk                        yes

Lists of CIDR Blocks, IPsets, or Integers

This subsection describes the syntax of a list of CIDR blocks, a list of IPset file names, and a list of integers. These lists are used in the sensor block and group block commands described below.

A group block (see "Group Block") allows you to assign names to these lists. Once the name is defined, it may be referenced in other lists of the same type by prepending the "at" character (@) to the group's name.

The lists are:

cidr-block-list: A cidr-block-list (or ipblock-list) contains one or more CIDR blocks or group references that represent an address space. Adjacent values in the list may be separated by multiple whitespace (space or tab) characters and/or a single comma. When IPv4 and IPv6 addresses combined, IPv4 addresses are mapped into the ::ffff:0:0/96 netblock. For lists containing more than a few CIDR blocks, consider using an IPset list instead.
ipset-list: An ipset-list contains the path names of one or more binary IPset files or group references. To create an IPset file, use the rwsetbuild(1) tool. Each path name may be a double-quoted string ("example"); the quote characters are not necessary if the path name does not contain whitespace or any special characters (single-quote ', double-quote ", comma ,, or pound #). Adjacent values in the list may be separated by multiple whitespace (space or tab) characters and/or a single comma. When multiple IPset files are specified, a new IPset is created in memory and the contents of the files are merged into it. rwflowpack(8) exits with an error if the IPset file does not exist or does not contain any IP addresses. Since SiLK 3.10.0.
interface-list: An interface-list contains one or more integers between 0 and 65535, inclusive, or group references or that represent SNMP interface indexes or VLAN identifiers. Adjacent values in the list may be separated by multiple whitespace (space or tab) characters and/or a single comma.

Group Block

The use of group blocks is optional. They are a convenience to define and give a name to a list of commonly used CIDR blocks, IPset files, or integer values that are treated as SNMP interfaces or VLAN identifiers. Groups may be used in sensor blocks ("Sensor Block") as described in the descriptions for the discard-when, discard-unless, network-name-ipblocks, network-name-ipsets and network-name-interfaces commands, below.

The commands in a group definition must all be of the same type. For example, you cannot mix ipblocks and ipsets commands in a single group definition, even though both contain IP addresses.

The contents of an existing group may be added to the current group block by using a group reference after the appropriate keyword as long as both groups are the same type. A group reference is the name of the group prefixed by the "at" character (@). When a group reference is used, the contents of the existing groups are copied into the current group.

For examples of group blocks, see "Group definitions" below.

The group command is used at top-level to begin a group definition block, and the remaining commands are accepted within the group block.

group group-name: The group command begins a new group definition block which continues to the end group command. The argument to the group command is the name of the group being defined. The group-name must be unique among all groups. It must begin with a letter, and it may not contain whitespace characters or the slash character (/).
end group: The end group command ends the definition of a group. Following an end group command, top-level commands are again accepted.
interfaces interface-list: The interfaces command adds integer values to a group, where each integer is treated as an SNMP interface number or VLAN identifier. An interface-list is a list of integers or group references as defined above ("Lists of CIDR Blocks, IPsets, or Integers"). The interfaces command may appear multiple times in a group block.
ipblocks cidr-block-list: The ipblocks command adds CIDR block values to a group. The cidr-block-list is described above. The ipblocks command may appear multiple times in a group block.
ipsets ipset-list: The ipset command adds the IP addresses specified in an IPset file to a group. The ipsets command may appear multiple times in a group block. Since SiLK 3.10.0.

Sensor Block

The information from the sensor block is used by rwflowpack to determine how to categorize a flow; that is, in which file the flow record is stored. The packlogic-twoway(3) manual page describes how rwflowpack may use the sensor blocks to determine a record's category.

When the Sensor Configuration file is used with flowcap, no sensors need to be defined. In fact, flowcap completely ignores all text inside each sensor block.

The sensor block works with the packing logic to determine where rwflowpack stores flow records. The packing logic plug-in specifies a list of network names, and you will refer to these networks when you configure the sensor block. Most plug-ins provide the external, internal, and null names, where internal refers to network being monitored, null are flows that were blocked by the router's access control list, and external is everything else.

Several of the commands described below that categorize flow records require as an argument a list of CIDR blocks, a list of IPset files, or a list of integers. The syntax of these lists is described in the "Lists of CIDR Blocks, IPsets, or Integers" section above.

As part of determining how to process a flow record, rwflowpack may check a record's source or destination IP address against a cidr-block-list or an ipset-set. Note the following:

for a cidr-block-list, the IP address is sequentially compared to each element of the list, stopping once a match is made
when comparing an IPv4 address to an IPv6 list, the IPv4 address is converted to IPv6 by mapping it into the ::ffff:0:0/96 prefix for purposes of the comparison
when comparing an IPv6 address to an IPv4 list, an IPv6 address in the ::ffff:0:0/96 prefix is converted to IPv4 for purposes of the comparison and any other IPv6 address fails the comparison

As part of determining how to process a flow record, rwflowpack may check whether the record's input or output fields are an interface-list. Whether the input and output fields contain SNMP interfaces or VLAN identifiers is determined by the interface-values command in the probe block (c.f. "Probe Block").

The sensor command is used in the top-level context to begin a sensor configuration block, and the remaining commands are accepted within the sensor block.

sensor sensor-name: The sensor command begins a new sensor configuration block. It takes as an argument the name of the sensor being configured, and that sensor must be defined in the Site Configuration file (see silk.conf(5)). A sensor block is closed with the end sensor command. You may have multiple sensor blocks that have the same sensor-name.
end sensor: The end sensor command ends the configuration of a sensor. Following an end sensor command, top-level commands are again accepted.
probe-type-probes probe-name [probe-name ...]: This command associates the listed probe names of the given probe type with the sensor. The probes do not have to be defined before they are used. (Note this also means that a mistyped probe-name will not be detected.) For example, netflow-v5-probes S1 says that S1 is a netflow-v5 probe; whenever flow data arrives on the S1 probe, the sensor associated with the probe notices that data is available and processes it. Adjacent probe names in the argument list may be separated by space or tab characters and/or a single comma.
source-network network-name: This command causes the sensor to assume that all flows originated from the network named network-name. For example, if a sensor is associated a probe that only monitors incoming traffic, you could use source-network external to specify that all traffic originated from the external network.
destination-network network-name: This command causes the sensor to assume that all flows were sent to the network named network-name.
network-name-ipblocks {cidr-block-list | remainder}: This command specifies the IP-space that is assigned to the network named network-name. The value of the command can be the keyword remainder or a cidr-block-list as defined above. When the value is the keyword remainder, the IP-space for network-name is conceptually all IPs not assigned to other networks on this sensor. The remainder keyword may only appear one time within a sensor block.
network-name-ipsets {ipset-list | remainder}: This command specifies the IP-space that is assigned to the network named network-name. The value of the command can be the keyword remainder or an ipset-list as defined above. When the value is the keyword remainder, the IP-space for network-name is conceptually all IPs not assigned to other networks on this sensor. The remainder keyword may only appear one time within a sensor block.
network-name-interfaces {interface-list | remainder}: This command specifies the SNMP interface index(es) or VLAN identifiers that are assigned to the network named network-name. The value of the command may be the keyword remainder or an interface-list as defined above. When the value is the keyword remainder, the interface list is computed by finding all interface values not assigned to other networks on this sensor. The remainder keyword may only appear one time within a sensor block.
isp-ip ip-address [ip-address ...]: This optional command may be used for a sensor that processes NetFlow data. The value to the command is a list of IP addresses in dotted-decimal notation, where the IPs are the addresses of the NICs on the router. For traffic that doesn't leave the router (and thus was sent to the router's null-interface), some packing-logic plug-ins use these IPs to distinguish legitimate traffic for the router (e.g., routing protocol traffic, whose destination address would be in this list) from traffic that violated the router's access control list (ACL).

The following optional sensor block commands provide a way to filter the flow records that rwflowpack packs for a sensor. Each filter begins with either discard-when or discard-unless, mentions a flow record field, and ends with a list of values.

The discard-when command causes the sensor to ignore the flow record if the property matches any of the elements in the list. When a match is found, rwflowpack immediately stops processing the record for the current sensor and the flow is not packed for this sensor.

The discard-unless command causes the sensor to ignore the flow record unless the property matches one of the elements in the list. That is, the flow record is packed only if its property matches one of the values specified in the list, and, when multiple discard-unless commands are present, if the flow record matches the values specified in each.

For each individual property, only one of discard-when or discard-unless may be specified.

discard-when source-interfaces interface-list: Instructs rwflowpack to discard a flow record for this sensor if the value in the flow's input field is listed in interface-list. When paired with VLAN tagging (see the interface-values command in the probe block), this allows the administrator to discard flows that have a specific VLAN tag. The commands discard-when source-interfaces and discard-unless source-interfaces may not be specified on the same sensor, but other discard- commands are permitted.
discard-unless source-interfaces interface-list: Instructs rwflowpack to discard the flow record for this sensor unless the flow's input field is in interface-list. That is, the flow record may be packed only if its input field matches one of the values specified in interface-list. When paired with VLAN tagging, this allows one to discard flows that do not have a specific VLAN tag. The commands discard-when source-interfaces and discard-unless source-interfaces may not be specified on the same sensor, but other discard- commands are permitted.
discard-when destination-interfaces interface-list: Discards a flow for this sensor when the flow's output field matches a value in interface-list. May not appear in the same sensor block with discard-unless destination-interfaces.
discard-unless destination-interfaces interface-list: Discards a flow for this sensor unless the flow's output field matches a value in interface-list. May not appear in the same sensor block with discard-when destination-interfaces.
discard-when any-interfaces interface-list: Discards a flow for this sensor when either the flow's input or its output field matches a value in interface-list. May not appear in the same sensor block with discard-unless any-interfaces.
discard-unless any-interfaces interface-list: Discards a flow for this sensor unless either the flow's input or its output field matches a value in interface-list. May not appear in the same sensor block with discard-unless any-interfaces.
discard-when source-ipblocks cidr-block-list: Discards a flow for this sensor when the flow's source IP address, sIP, matches one of the CIDR blocks in cidr-block-list. May not appear in the same sensor block with discard-unless source-ipblocks.
discard-unless source-ipblocks cidr-block-list: Discards a flow for this sensor unless the flow's source IP address, sIP, matches one of the CIDR blocks in cidr-block-list. May not appear in the same sensor block with discard-when source-ipblocks.
discard-when destination-ipblocks cidr-block-list: Discards a flow for this sensor when the flow's destination IP address, dIP, matches one of the CIDR blocks in cidr-block-list. May not appear in the same sensor block with discard-unless destination-ipblocks.
discard-unless destination-ipblocks cidr-block-list: Discards a flow for this sensor unless the flow's destination IP address, dIP, matches one of the CIDR blocks in cidr-block-list. May not appear in the same sensor block with discard-when destination-ipblocks.
discard-when any-ipblocks cidr-block-list: Discards a flow for this sensor when either the flow's source IP or its destination IP address matches one of the CIDR blocks in cidr-block-list. May not appear in the same sensor block with discard-unless any-ipblocks.
discard-unless any-ipblocks cidr-block-list: Discards a flow for this sensor unless either the flow's source IP or its destination IP address matches one of the CIDR blocks in cidr-block-list. May not appear in the same sensor block with discard-when any-ipblocks.
discard-when source-ipsets ipset-list: Discards a flow for this sensor when the flow's source IP address, sIP, is in one of IPset files in ipset-list. May not appear in the same sensor block with discard-unless source-ipsets. Since SiLK 3.10.0.
discard-unless source-ipsets ipset-list: Discards a flow for this sensor unless the flow's source IP address, sIP, is in one of IPset files in ipset-list. May not appear in the same sensor block with discard-when source-ipsets. Since SiLK 3.10.0.
discard-when destination-ipsets ipset-list: Discards a flow for this sensor when the flow's destination IP address, dIP, is in one of the IPset files in ipset-list. May not appear in the same sensor block with discard-unless destination-ipsets. Since SiLK 3.10.0.
discard-unless destination-ipsets ipset-list: Discards a flow for this sensor unless the flow's destination IP address, dIP, is in one of the IPset files in ipset-list. May not appear in the same sensor block with discard-when destination-ipsets. Since SiLK 3.10.0.
discard-when any-ipsets ipset-list: Discards a flow for this sensor when either the flow's source IP or its destination IP address is in one of the IPset files in ipset-list. May not appear in the same sensor block with discard-unless any-ipsets. Since SiLK 3.10.0.
discard-unless any-ipsets ipset-list: Discards a flow for this sensor unless either the flow's source IP or its destination IP address is in one of the IPset files in ipset-list. May not appear in the same sensor block with discard-when any-ipsets. Since SiLK 3.10.0.

EXAMPLES

All these examples assume you are using the packlogic-twoway(3) packing logic plug-in to rwflowpack(8).

Group definitions

The following shows how to create groups that can be used in other group blocks or in certain commands within a sensor block.

group G01
    interfaces 1 2, 3
    interfaces 4
end group

group G02
    interfaces 5 @G01
end group

group G03
    interfaces @G02
    interfaces 6
end group

group G11
    ipblocks 192.0.2.0/27  192.0.2.32/27,  192.0.2.64/26
    ipblocks 192.0.2.128/25
end group

group G12
    ipblocks 198.51.100.0/24  @G11
end group

group G13
    ipblocks @G12
    ipblocks 203.0.113.0/24
end group

group G21
    ipsets /var/sets/ip1.set  /var/sets/ip2.set,  /var/sets/ip3.set
    ipsets /var/sets/ip4.set
end group

group G22
    ipsets /var/sets/ip5.set  @G21
end group

group G23
    ipsets @G22
    ipsets /var/sets/ip6.set
end group

NetFlow v5 Categorized by SNMP Interface

The following two blocks define a probe that listens on 9900/udp for NetFlow v5 from a router. The probe only accepts traffic originating from 172.16.22.22 or 172.16.33.33. The associated sensor uses the SNMP interfaces to categorize the flows, where traffic that enters the router on interface 1 and leaves on interface 8 is in, traffic entering on 8 and leaving on 1 is out, traffic from 1 to 0 is innull, traffic from 8 to 8 is int2int, etc.

probe S1 netflow-v5
    listen-on-port 9901
    protocol udp
    accept-from-host 172.16.22.22 172.16.33.33
end probe

sensor S1
    netflow-v5-probes S1
    external-interfaces 1
    internal-interfaces 8
    null-interfaces 0
end sensor

NetFlow v5 Categorized by IP Address

The probe in this example is the same as above, except the administrator has chosen to log only messages about bad packets (messages about missing packets will be ignored). The sensor is categorizing flows by the source and destination IP address in the flow record. The internal network is defined as 128.2.0.0/16, and all other IPs are defined as external. For example, HTTP traffic whose source is 128.2.0.1 and destination is google.com will be categorized as outweb; the reply (source of google.com and destination 128.2.0.1) will be inweb.

probe S2 netflow-v5
    listen-on-port 9902
    protocol udp
    accept-from-host 172.16.22.22 172.16.33.33
    log-flags bad                     # ignore missing pkts
end probe

sensor S2
    netflow-v5-probes S2
    internal-ipblocks 128.2.0.0/16
    external-ipblocks remainder
end sensor

IPFIX Categorized by IP Address

This example uses an IPFIX probe to collect the flows on port 9903/tcp, where the probe binds to address 192.168.1.92. The sensor configuration is the same as in the previous example, but a group definition is used to define the internal network.

probe S3 ipfix
    listen-on-port 9903
    protocol tcp
    listen-as-host 192.168.1.92
end probe

group my-network
    ipblocks 128.2.0.0/16
end group

sensor S3
    ipfix-probes S3
    internal-ipblocks @my-network
    external-ipblocks remainder
end sensor

IPFIX Read from Files

This example uses the same sensor configuration as above. The probe processes files that have been created by yaf(1) and stored in the directory /tmp/var/yaf/.

probe S4 ipfix
    poll-directory /tmp/var/yaf
end probe

sensor S4
    ipfix-probes S4
    internal-ipblock 128.2.0.0/16
    external-ipblock remainder
end sensor

NetFlow v9 Categorized by IP Address

This example uses a NetFlow v9 probe to collect the flows on port 9905/udp, where the probe binds to address 192.168.1.92. The sensor configuration uses an IPset file to define the internal network.

probe S5 netflow-v9
    listen-on-port 9905
    protocol udp
    listen-as-host 192.168.1.92
end probe

sensor S5
    netflow-v9-probes S5
    internal-ipsets /var/sets/my-network.set
    external-ipsets remainder
end sensor

sFlow v5 Categorized by IP Address

This example uses an sFlow probe to collect the flows on port 9906/udp, where the probe binds to the IPv6 address ::1. The sensor configuration uses an IPset file to define the internal network.

probe S19 sflow
    listen-on-port 9906
    protocol udp
    listen-as-host ::1
end probe

sensor S19
    sflow-probes S19
    internal-ipsets /var/sets/my-network.set
    external-ipsets remainder
end sensor

NetFlow v9 from a Cisco ASA Router

When collecting NetFlow v9 data from a Cisco ASA (Adaptive Security Appliance), specify the quirks statement as shown in this example to enable special handling of the NetFlow data.

probe S20 netflow-v9
    listen-on-port 9988
    protocol udp
    quirks firewall-event zero-packets
end probe

sensor S20
    netflow-v9-probes S20
    internal-ipsets /var/sets/my-network.set
    external-ipsets remainder
end sensor

Multiple Sources Becoming One Sensor (One Port)

Consider a scenario where there are multiple input streams that need to be treated as a single sensor. For example, you use multiple routers for load-balancing but you want them treated as a single logical sensor. In this configuration, you send all the input streams to a single port, and you define a single probe listening on that port. As long as the streams have a unique source IP, the streams will be treated distinctly.

The following sensor and probe blocks accept any number of TCP-based IPFIX connections to port 9907 and any number of NetFlow v5 connections to 9908. This configuration works for all types of input as SiLK 3.4.0 when using libfixbuf-1.2.0. See the configuration in the following example for a alternate approach.

probe S7 ipfix
    listen-on-port 9907
    protocol tcp
end probe

sensor S7
    ipfix-probes S7
    internal-ipblocks 128.2.0.0/16
    external-ipblocks remainder
end sensor

probe S8 netflow-v5
    listen-on-port 9908
    protocol udp
    log-flags bad
end probe

sensor S8
    netflow-v5-probes S8
    internal-ipblocks 128.2.0.0/16
    external-ipblocks remainder
end sensor

Multiple Sources Becoming One Sensor (Multiple Ports)

Like the previous example, this example configuration causes multiple input streams to be treated as a single sensor. In this solution, each stream arrives on a separate port where it is collected by a separate probe. The sensor block combines the probes into one sensor. This type of approach works with all types of input for all releases of SiLK.

probe S6-p1 netflow-v9
    listen-on-port 9961
    protocol udp
end probe

probe S6-p2 netflow-v9
    listen-on-port 9962
    protocol udp
end probe

probe S6-p3 netflow-v9
    listen-on-port 9963
    protocol udp
end probe

sensor S6
    netflow-v9-probes S6-p1, S6-p2, S6-p3
    internal-ipblocks 128.2.0.0/16
    external-ipblocks remainder
end sensor

Multiple Sources Becoming One Sensor (Specific Directions)

Consider the case of using yaf on a monitor at the border of a network where all traffic entering the network arrives at the monitor on one network interface card (NIC) and all traffic leaving the network arrives at the monitor on a different NIC. Since yaf does not support multiple interfaces yet, you must run two yaf processes, one for each NIC. The sensor configuration for this monitor would list two probes, each listening on a different port, and two sensor blocks both packing to the same sensor. Each sensor block packs the traffic as incoming or outgoing depending on which probe received the traffic.

probe S9-in ipfix
    listen-on-port 9991
    protocol tcp
end probe

probe S9-out ipfix
    listen-on-port 9992
    protocol tcp
end probe

sensor S9
    ipfix-probes S9-in
    source-network external
    destination-network internal
end sensor

sensor S9
    ipfix-probes S9-out
    source-network internal
    destination-network external
end sensor

Multiple Sources to Multiple Sensors (Same Port)

Suppose your network has multiple flow generators that you wish to treat as separate sensors, but you would like to minimize the number of open ports on your firewall. To support this configuration, configure the probes to distinguish the traffic based on the source address. Specifically, create a separate probe for each sensor where the probes of the same type use the same listen-on-port value but different accept-from-host values. (Different probe types may not bind the same port; the combination of listen-on-port, protocol, and listen-as-host must be unique for different probe types.) The following configuration uses a NetFlow v5 probe, which works for all versions of SiLK. A similar configuration works for any type of input as of SiLK 3.4.0 and libfixbuf-1.2.0.

probe S10 netflow-v5
    listen-on-port 9910
    accept-from-host 172.16.22.10
    protocol udp
end probe

probe S11 netflow-v5
    listen-on-port 9910
    accept-from-host 172.16.22.11
    protocol udp
end probe

group my-network2
    ipblocks 128.2.0.0/16
end group

sensor S10
    netflow-v5-probes S10
    internal-ipblocks @my-network2
    external-ipblocks remainder
end sensor

sensor S11
    netflow-v5-probes S11
    internal-ipblocks @my-network2
    external-ipblocks remainder
end sensor

Single Source Becoming Multiple Sensors

Suppose you have instrumented a single router but you wish to split the traffic into two sensors, where one part of the network (monitored by sensor S12) is defined as 128.2.0.0/17, and the other (sensor S13) as 128.2.128.0/17. Traffic between 128.2.0.1 and google.com will be assigned to sensor S12, but it will so appear as ext2ext traffic for sensor S13 unless you explicitly discard that traffic using the discard-unless command.

probe S12-S13 ipfix
    listen-on-port 9912
    protocol tcp
end probe

group S12-space
    ipblocks 128.2.0.0/17
end group

group S13-space
    ipblocks 128.2.128.0/17
end group

sensor S12
    ipfix-probes S12-S13
    discard-unless any-ipblock @S12-space
    internal-ipblocks @S12-space
    external-ipblocks remainder
end sensor

sensor S13
    ipfix-probes S12-S13
    discard-unless any-ipblock @S13-space
    internal-ipblocks @S13-space
    external-ipblocks remainder
end sensor

Discarding Flows Using VLAN Tags

You can configure rwflowpack to discard flows that do not have a particular VLAN tag. First, specify the interface-values command to instruct the probe to put the VLAN id into the fields that typically store the SNMP interfaces. On the sensor, use the discard-unless command to discard flows that do not have the desired VLAN tag (114 in this example). Often you will not use the VLAN tags to determine a flow's direction (category) since there is a single VLAN tag on each flow; instead, you specify the IP space of the monitored network in the sensor block. (However, see the next example.)

probe S14 ipfix
    listen-on-port 9914
    protocol tcp
    interface-values vlan
end probe

sensor S14
    ipfix-probes S14
    discard-unless any-interface 114
    internal-ipblocks 128.2.0.0/16
    external-ipblocks remainder
end sensor

Categorizing Flows Using VLAN Tags

By repeating a sensor block and using different discard-unless commands in each block, you may configure rwflowpack to categorize flow records based on VLAN tags. Suppose yaf is monitoring a connection where incoming flows are marked with VLAN tag 151 and outgoing flows are marked with 152. You simply discard any traffic that does not have the wanted VLAN tag, and use the source-network and destination-network commands to assign the direction to the flow. In this example, any flow record that does not have one of the expected VLAN tags has its source-network set to null, but since rwflowpack does not expect a flow record to originate from the null network, it stores the record in the other category for later analysis/debugging. (This example requires SiLK 3.1 or later.)

probe S15 ipfix
    listen-on-port 9915
    protocol tcp
    interface-values vlan
end probe

sensor S15
    # vlan ID 151 is incoming
    ipfix-probes S15
    discard-unless source-interface 151
    source-network       external
    destination-network  internal
end sensor

sensor S15
    # vlan ID 152 is outgoing
    ipfix-probes S15
    discard-unless source-interface 152
    source-network       internal
    destination-network  external
end sensor

sensor S15
    # discard flows that have known IDs
    # force unknown IDs into the "other" category
    ipfix-probes S15
    discard-when source-interface 151,152
    source-network       null
    destination-network  internal
end sensor

IPFIX Collected by a DAG Card

When yaf generates flow records from a multi-port Endace DAG card, it is possible to use the port where the traffic was seen to categorize the traffic in rwflowpack.

To do this, include the --dag-interface switch on the yaf command line. This switch causes yaf to store the DAG port where the packet was collected into the equivalent of the SNMP input field, and yaf sets the SNMP output field to an offset of the port, specifically the port plus 256 (0x100|port).

Assume DAG port 0 is connected to the external side of the network (so it sees incoming traffic), and assume DAG port 1 is on the internal side. For incoming traffic, yaf sets the input and output values to 0 and 256, respectively. For outgoing traffic, the values are 1 and 257.

The sensor.conf configuration file for rwflowpack would be:

probe S16-dag ipfix
    listen-on-port 9916
    protocol tcp
end probe

sensor S16
    ipfix-probes S16-dag
    external-interface 0,257
    internal-interface 1,256
end sensor

When rwflowpack processes the IPFIX flow records, it treats flow records having an input of 0 and an output of 256 as traffic moving from an external interface to an internal interface, and rwflowpack packs those records as incoming. Similarly for the outgoing flow records.

Repacking of SiLK Flows by IP Address

A probe whose type is silk must get its flows by polling a directory of SiLK Flow files. The flows can be re-categorized based on the IP addresses or based on the SNMP interfaces (beware: often the SNMP interface values are 0 in SiLK Flow data). In this example, the files in the directory /var/tmp/old-data/ are processed. The internal network is defined as 128.2.0.0/16, and all other IPs are defined as external.

probe S17 silk
    poll-directory /var/tmp/old-data
end probe

sensor S17
    silk-probes S17
    internal-ipblock 128.2.0.0/16
    external-ipblock remainder
end sensor

NetFlow From a File Categorized by SNMP Interfaces

Instead of listening on a UDP port for NetFlow traffic, you can configure the probe to process a single file containing NetFlow v5 PDUs. This example assumes you are running rwflowpack with the switches --input-mode=file --netflow-file=FILENAME. The --netflow-file switch overrides the read-from-file command on the probe. rwflowpack will exit once it processes that single file.

probe S18 netflow-v5
    log-flags bad                     # ignore missing pkts
    read-from-file /dev/null          # use --netflow-file=<file>
end probe

sensor S18
    netflow-v5-probes S18
    external-interface 182
    internal-interface 189
    null-interface 0
end sensor

NOTES

Support for using double-quoted strings for IPset path names was added in SiLK 3.17.2.

The accept-from-host command began to accept a list of arguments in SiLK 3.10.1.

SiLK 3.10.0 added IPset file support to the group block and to some commands in the sensor block.

Support for collecting sFlow records was added in SiLK 3.9.0.

The quirks command was introduced in SiLK 3.8.0.