--- name: "flow-nfilter" section: "1" platform: "linux" package: "flow-tools" version: "1:0.68-12.5+b3" release: "Debian 10 (Buster)" platforms: ["linux"] url: "https://new.carta.tech/flow-nfilter" --- # flow-nfilter(1) Filter flows. ## NAME **flow-nfilter** — Filter flows. ## SYNOPSIS **flow-nfilter** \[-hk\] \[-b *big*\|*little*\] \[-C *comment*\] \[-d *debug\_level*\] \[-f *filter\_fname*\] \[-F *filter\_definition*\] \[-v *variable binding*\] \[-z *z\_level*\] ## DESCRIPTION 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 ``` ## OPTIONS - \-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 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 ## EXAMPLES 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** ## FILES **Configuration files:**\ **Symbols - /etc/flow-tools/sym/\*.**\ **Tag - /etc/flow-tools/cfg/tag.cfg.**\ **Filter - /etc/flow-tools/cfg/filter.cfg.** ## BUGS **None known.** ## AUTHOR **Mark Fullmer maf@splintered.net** ## SEE ALSO **[flow-tools(1)](/flow-tools/1.md)**