Merge pull request #1221 from Giggum/master

docs: fix to improve readability and correct typos.
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Firewall Firewall
######## ########
With VyOS being based on top of Linux and its kernel, the Netfilter project As VyOS is based on Linux it leverages its firewall. The Netfilter project
created the iptables and now the successor nftables for the Linux kernel to created iptables and its successor nftables for the Linux kernel to
work directly on the data flows. This now extends the concept of zone-based work directly on packet data flows. This now extends the concept of
security to allow for manipulating the data at multiple stages once accepted zone-based security to allow for manipulating the data at multiple stages once
by the network interface and the driver before being handed off to the accepted by the network interface and the driver before being handed off to
destination (e.g. a web server OR another device). the destination (e.g., a web server OR another device).
A simplified traffic flow, based on Netfilter packet flow, is shown next, in A simplified traffic flow diagram, based on Netfilter packet flow, is shown
order to have a full view and understanding of how packets are processed, and next, in order to have a full view and understanding of how packets are
what possible paths can take. processed, and what possible paths traffic can take.
.. figure:: /_static/images/firewall-gral-packet-flow.png .. figure:: /_static/images/firewall-gral-packet-flow.png
Main notes regarding this packet flow and terminology used in VyOS firewall: The main points regarding this packet flow and terminology used in VyOS
firewall are covered below:
* **Bridge Port?**: choose appropiate path based on if interface were the * **Bridge Port?**: choose appropriate path based on whether interface
packet was received is part of a bridge, or not. where the packet was received is part of a bridge, or not.
If interface were the packet was received isn't part of a bridge, then packet If the interface where the packet was received isn't part of a bridge, then
is processed at the **IP Layer**: packetis processed at the **IP Layer**:
* **Prerouting**: several actions can be done in this stage, and currently * **Prerouting**: several actions can be done in this stage, and currently
these actions are defined in different parts in vyos configuration. Order these actions are defined in different parts in VyOS configuration. Order
is important, and all these actions are performed before any actions is important, and all these actions are performed before any actions
define under ``firewall`` section. Relevant configuration that acts in defined under ``firewall`` section. Relevant configuration that acts in
this stage are: this stage are:
* **Conntrack Ignore**: rules defined under ``set system conntrack ignore * **Conntrack Ignore**: rules defined under ``set system conntrack ignore
@ -40,12 +41,12 @@ is processed at the **IP Layer**:
* **Destination NAT**: rules defined under ``set [nat | nat66] * **Destination NAT**: rules defined under ``set [nat | nat66]
destination...``. destination...``.
* **Destination is the router?**: choose appropiate path based on * **Destination is the router?**: choose appropriate path based on
destination IP address. Transit forward continunes to **forward**, destination IP address. Transit forward continues to **forward**,
while traffic that destination IP address is configured on the router while traffic that destination IP address is configured on the router
continues to **input**. continues to **input**.
* **Input**: stage where traffic destinated to the router itself can be * **Input**: stage where traffic destined for the router itself can be
filtered and controlled. This is where all rules for securing the router filtered and controlled. This is where all rules for securing the router
should take place. This includes ipv4 and ipv6 filtering rules, defined should take place. This includes ipv4 and ipv6 filtering rules, defined
in: in:
@ -61,10 +62,10 @@ is processed at the **IP Layer**:
* ``set firewall ipv6 forward filter ...``. * ``set firewall ipv6 forward filter ...``.
* **Output**: stage where traffic that is originated by the router itself * **Output**: stage where traffic that originates from the router itself
can be filtered and controlled. Bare in mind that this traffic can be a can be filtered and controlled. Bear in mind that this traffic can be a
new connection originted by a internal process running on VyOS router, new connection originated by a internal process running on VyOS router,
such as NTP, or can be a response to traffic received externaly through such as NTP, or a response to traffic received externaly through
**inputt** (for example response to an ssh login attempt to the router). **inputt** (for example response to an ssh login attempt to the router).
This includes ipv4 and ipv6 filtering rules, defined in: This includes ipv4 and ipv6 filtering rules, defined in:
@ -79,16 +80,16 @@ is processed at the **IP Layer**:
* **Source NAT**: rules defined under ``set [nat | nat66] * **Source NAT**: rules defined under ``set [nat | nat66]
destination...``. destination...``.
If interface were the packet was received is part of a bridge, then packet If the interface where the packet was received is part of a bridge, then
is processed at the **Bridge Layer**, which contains a ver basic setup where packetis processed at the **Bridge Layer**, which contains a basic setup for
for bridge filtering: bridge filtering:
* **Forward (Bridge)**: stage where traffic that is trasspasing through the * **Forward (Bridge)**: stage where traffic that is trespasing through the
bridge is filtered and controlled: bridge is filtered and controlled:
* ``set firewall bridge forward filter ...``. * ``set firewall bridge forward filter ...``.
Main structure VyOS firewall cli is shown next: The main structure VyOS firewall cli is shown next:
.. code-block:: none .. code-block:: none
@ -134,7 +135,7 @@ Main structure VyOS firewall cli is shown next:
- custom_zone_name - custom_zone_name
+ ... + ...
Please, refer to appropiate section for more information about firewall Please, refer to appropriate section for more information about firewall
configuration: configuration:
.. toctree:: .. toctree::