Migrate new file structure to crux (#435)

* order workflows and add submodule

* rename gitmodules file

* delete docs/.gitignore

* add vyos custom linter

* correct __pycache__ in gitignore

* add test-coverage.py

* move draw.io folder

* arrange changelog, install history and about

* arrange: firewall

* arrange: highavailability

* arrange: loadbalancing

* arrange: nat

* arrange: services

* sort configexamples and configuration interfaces

* wireles: rename wireless

* rearrange: Protocols and Policy

* rearrange: Firewall and Zone Policy

* rearrange: Interfaces

* rearrange: Interfaces

* rearrange: dynamic DNS

* hostinfo: add page to index

* rearrange: appendix

* venv: add Pipfile

* rearrange: contributing

* index: remove debugging

* rearrange: fix all figure and refs

* rearrange: commandtree

* fix: cli, openvpn, install headline level

* protocols: change headline

* firewall: move mss clamping

* ip: separate ipv4 and ipv6

* arp: move to static page

* igmp: rename multicast page

* Update to year 2021

1 files changed, 81 insertions, 0 deletions

diff --git a/docs/configuration/system/flow-accounting.rst b/docs/configuration/system/flow-accounting.rst
new file mode 100644
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+.. _flow-accounting:
+
+NetFlow is a feature that was introduced on Cisco routers around 1996 that
+provides the ability to collect IP network traffic as it enters or exits an
+interface. By analyzing the data provided by NetFlow, a network administrator
+can determine things such as the source and destination of traffic, class of
+service, and the causes of congestion. A typical flow monitoring setup (using
+NetFlow) consists of three main components:
+
+* Flow exporter: aggregates packets into flows and exports flow records towards
+  one or more flow collectors
+* Flow collector: responsible for reception, storage and pre-processing of flow
+  data received from a flow exporter
+* Analysis application: analyzes received flow data in the context of intrusion
+  detection or traffic profiling, for example
+
+For connectionless protocols as like ICMP and UDP, a flow is considered complete
+once no more packets for this flow appear after configurable timeout.
+
+NetFlow is usually enabled on a per-interface basis to limit load on the router
+components involved in NetFlow, or to limit the amount of NetFlow records
+exported.
+
+VyOS supports flow accounting through NetFlow (version 5, 9 and 10) or sFlow.
+
+Flow Accounting
+---------------
+
+In order for flow accounting information to be collected and displayed for an
+interface, the interface must be configured for flow accounting. The following
+example shows how to configure ``eth0`` and ``bond3`` for flow accounting.
+
+.. code-block:: none
+
+  set system flow-accounting interface eth0
+  set system flow-accounting interface bond3
+
+
+NetFlow is a protocol originating from Cisco Systems. It works on level3.
+VyOS supports version 5, 9 and 10 (IPFIX - IP Flow Information Export)
+
+NetFlow v5 example:
+
+.. code-block:: none
+
+  set system flow-accounting netflow engine-id 100
+  set system flow-accounting netflow version 5
+  set system flow-accounting netflow server 192.168.2.10 port 2055
+
+Displaying Flow Accounting Information
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Once flow accounting is configured on an interfaces it provides the ability to
+display captured network traffic information for all configured interfaces.
+
+The following op-mode command shows flow accounting for eth0.
+
+.. code-block:: none
+
+  vyos@vyos:~$ show flow-accounting interface eth0
+  flow-accounting for [eth0]
+  Src Addr        Dst Addr        Sport Dport Proto    Packets      Bytes   Flows
+  0.0.0.0         192.0.2.50      811   811     udp       7733     591576       0
+  0.0.0.0         192.0.2.50      811   811     udp       7669     586558       1
+  192.0.2.200     192.0.2.51      56188 22      tcp        586      36504       1
+  192.0.2.99      192.0.2.51      61636 161     udp         46       6313       4
+  192.0.2.99      192.0.2.51      61638 161     udp         42       5364       9
+  192.0.2.99      192.0.2.51      61640 161     udp         42       5111       3
+  192.0.2.200     192.0.2.51      54702 22      tcp         86       4432       1
+  192.0.2.99      192.0.2.51      62509 161     udp         24       3540       1
+  192.0.2.99      192.0.2.51      0     0      icmp         49       2989       8
+  192.0.2.99      192.0.2.51      54667 161     udp         18       2658       1
+  192.0.2.99      192.0.2.51      54996 161     udp         18       2622       1
+  192.0.2.99      192.0.2.51      63708 161     udp         18       2622       1
+  192.0.2.99      192.0.2.51      62111 161     udp         18       2622       1
+  192.0.2.99      192.0.2.51      61646 161     udp         16       1977       4
+  192.0.2.99      192.0.2.51      56038 161     udp         10       1256       1
+  192.0.2.99      192.0.2.51      55570 161     udp          6       1146       1
+  192.0.2.99      192.0.2.51      54599 161     udp          6       1134       1
+  192.0.2.99      192.0.2.51      56304 161     udp          8       1029       1
+