flow-nfilter - Filter flows.

flow-nfilter [-hk] [-b big|little] [-C comment] [-d debug_level] [-f filter_fname] [-F filter_definition] [-v variable binding] [-z z_level]

The flow-nfilter utility will filter flows based on user selectable criteria. Filters are defined in a configuration file and are composed of primitives and a definition. Definitions contain match lines grouped to form logical AND and OR operations on the flow using the selected primitives. A definition may contain the invert command which will invert the result of the evaluation.

Words in the configuration file of the form @VAR or @{VAR:-default} will be expanded at run-time by setting variable names with the -v option.

Filter primitives begin with the filter-primitive keyword followed by a symbolic name. Each primitive has a type defined below. A list of permit and or deny keywords followed by an argument are later evaulated to determine if the flow is permitted or denied. The default action for a primitive is to deny which may be changed with the default keyword. Symbolic substitutions are done where appropriate.

The match keyword in a definition selects the criteria to match a primitive. A match type may allow more than one type of primitive, for example the src-ip-addr match type will accept any of {ip-address, ip-address-mask, ip-address-prefix} primitive types.

 Primitive type          Type       Description/Example
-------------------------------------------------------------------
as                      Bucket     Autonomous System Number.
                                   600,159,3112

ip-address-prefix-len Numeric Integer from 0 to 32. 16-31

ip-protocol Bucket Integer from 0 to 255. 6,17,1

ip-tos Bucket Integer from 0 to 255 with mask. 0xA0/0xE0

ip-tcp-flags Bucket Integer from 0 to 255 with mask. 0x2/0x2

ifindex Bucket Integer from 0 to 65535 0,5,10

engine Bucket Integer from 0 to 255. 0

ip-port Bucket Integer from 0 to 65535. 80,8080,23,22

ip-address Hash List of IP Addresses. 10.0.0.1

ip-address-mask List List of IP address/mask pairs. 10.1.0.0 255.255.0.0

ip-address-prefix Trie List of IP address/mask pairs. 10.1/16

tag Hash List of tags. 0xFF00

tag-mask List List of tags. 0xF000/0xFF00

counter List List of Integers with qualifier. lt 32

time List List of relative time specifiers. gt 5:00

time-date List List of absolute time specifiers. gt December 12, 2002 5:13:21

double List List of doubles with qualifier. lt 32.0

rate Element Rate is calculated as 1/rate. permit 100

Match type Description Primitives accepted ------------------------------------------------------------------- source-as Source AS as

destination-as Destination AS as

ip-source-address Source IP Address ip-address, ip-address-mask, ip-address-prefix

ip-destination-address Destination IP Address ip-address, ip-address-mask, ip-address-prefix

ip-exporter-address Exporter IP Address ip-address, ip-address-mask, ip-address-prefix

ip-nexthop-address NextHop IP Address ip-address, ip-address-mask, ip-address-prefix

ip-shortcut-address Shortcut IP Address ip-address, ip-address-mask, ip-address-prefix

ip-protocol IP Protocol ip-protocol

ip-source-address-prefix-len Source IP address ip-address-prefix-len prefix length

ip-destination-address-prefix-len Destination IP address ip-address-prefix-len prefix length ip-tos IP Type Of Service ip-tos

ip-marked-tos IP Type Of Service ip-tos

ip-tcp-flags IP/TCP Flags ip-tcp-flags

ip-source-port Source IP Port ip-port eg TCP/UDP

ip-destination-port Destination IP Port ip-port eg TCP/UDP

input-interface Source ifIndex ifindex eg Input Interface

output-interface Destination ifIndex ifindex eg Output Interface

start-time Start Time of flow time, time-date

end-time End Time of Flow time, time-date

flows Number of flows counter

octets Number of octets counter

packets Number of packets counter

duration Duration of flow in ms counter

engine-id Engine ID engine

engine-type Engine Type engine

source-tag Source Tag tag, tag-mask

destination-tag Destination Tag tag, tag-mask

pps Packets Per Second double

bps Bits Per Second double

random-sample Random Sample rate

-b big|little

Byte order of output.

-C Comment

Add a comment.

-d debug_level

Enable debugging.

-f filter_fname

Filter list filename. Defaults to /etc/flow-tools/cfg/filter.

-F filter_definition

Select the active definition. Defaults to default.

-h

Display help.

-k

Keep time from input.

-v variable binding

Set a variable FOO=bar.

-z z_level

Configure compression level to z_level. 0 is disabled (no compression), 9 is highest compression.

time-date parsing is implemented with getdate.y, a commonly used function to process free-form time date specifications. Example usage borrowed from cvs: 1 month ago 2 hours ago 400000 seconds ago last year last Monday yesterday a fortnight ago 3/31/92 10:00:07 PST January 23, 1987 10:05pm 22:00 GMT

An example of filter configuration file.

 filter-primitive srate
  type rate
  permit 100

filter-primitive test-as type as permit 600,159

filter-primitive test-prefix-len type ip-address-prefix-len permit 32

filter-primitive test-protocol type ip-protocol permit tcp

filter-primitive test-tos type ip-tos mask 0xA0 permit 0xE0

filter-primitive test-tcp-flags type ip-tcp-flags mask 0x2 permit 0x2

filter-primitive test-ifindex type ifindex permit 0,5,10

filter-primitive test-engine type engine permit 0

filter-primitive test-port type ip-port permit https permit 80 default deny

filter-primitive test-address type ip-address permit 0.0.0.1 permit 0.0.0.2 default deny

filter-primitive test-address-mask type ip-address-mask permit 128.146.197.1 255.255.255.255 permit 128.146.197.2 255.255.255.255

filter-primitive test-prefix type ip-address-prefix permit 128.146.0.0/16 default deny

filter-primitive test-tag type tag permit 0x00 permit 0x01 permit 0xFF

filter-primitive test-tag-mask type tag-mask permit OSU 0xFF permit 0xFF 0xFF default deny

filter-primitive test-counter type counter permit lt 5 permit gt 10 default deny

filter-primitive test-time-date type time-date permit gt December 12, 2002 5:13:21

filter-primitive test-time type time-date permit gt 12:15:00

filter-definition sample-1-in-100 match random-sample srate

filter-definition t1 match engine-type test-engine or match destination-tag test-tag-mask

Display all flows with a destination port of 80 or source port of 25 (smtp) starting after Dec 12, 2001. The file test is populated with the following:

filter-primitive port80
  type ip-port
  permit 80

filter-primitive port25 type ip-port permit smtp

filter-primitive dec12 type time-date permit gt Dec 12, 2001

filter-definition foo match ip-source-port port80 match start-time dec12 or match ip-destination-port port25 match start-time dec12 flow-cat flows | flow-nfilter -ftest -Ffoo | flow-print

Configuration files: Symbols - /etc/flow-tools/sym/*. Tag - /etc/flow-tools/cfg/tag.cfg. Filter - /etc/flow-tools/cfg/filter.cfg.

None known.

Mark Fullmer maf@splintered.net

flow-tools(1)