CT HELPER
~~~~~~~~~
[verse]
*add* *ct helper* ['family'] 'table' 'name' *{ type* 'type' *protocol* 'protocol' *;* [*l3proto* 'family' *;*] *}*
*delete* *ct helper* ['family'] 'table' 'name'
*list* *ct helpers*

Ct helper is used to define connection tracking helpers that can then be used in
combination with the *ct helper set* statement. 'type' and 'protocol' are
mandatory, l3proto is derived from the table family by default, i.e. in the inet
table the kernel will try to load both the ipv4 and ipv6 helper backends, if
they are supported by the kernel.

.conntrack helper specifications
[options="header"]
|=================
|Keyword | Description | Type
| type |
name of helper type |
quoted string (e.g. "ftp")
|protocol |
layer 4 protocol of the helper |
string (e.g. ip)
|l3proto |
layer 3 protocol of the helper |
address family (e.g. ip)
|comment |
per ct helper comment field |
string
|=================

.defining and assigning ftp helper
----------------------------------
Unlike iptables, helper assignment needs to be performed after the conntrack
lookup has completed, for example with the default 0 hook priority.

table inet myhelpers {
  ct helper ftp-standard {
     type "ftp" protocol tcp
  }
  chain prerouting {
      type filter hook prerouting priority filter;
      tcp dport 21 ct helper set "ftp-standard"
  }
}
----------------------------------

CT TIMEOUT
~~~~~~~~~~
[verse]
*add* *ct timeout*  ['family'] 'table' 'name' *{ protocol* 'protocol' *; policy = {* 'state'*:* 'value' [*,* ...] *} ;* [*l3proto* 'family' *;*] *}*
*delete* *ct timeout* ['family'] 'table' 'name'
*list* *ct timeouts*

Ct timeout is used to update connection tracking timeout values.Timeout policies are assigned
with the *ct timeout set* statement. 'protocol' and 'policy' are
  mandatory, l3proto is derived from the table family by default.

.conntrack timeout specifications
[options="header"]
|=================
|Keyword | Description | Type
| protocol |
layer 4 protocol of the timeout object |
string (e.g. ip)
|state |
connection state name |
string (e.g. "established")
|value |
timeout value for connection state |
unsigned integer
|l3proto |
layer 3 protocol of the timeout object |
address family (e.g. ip)
|comment |
per ct timeout comment field |
string
|=================

tcp connection state names that can have a specific timeout value are:

'close', 'close_wait', 'established', 'fin_wait', 'last_ack', 'retrans', 'syn_recv', 'syn_sent', 'time_wait' and 'unack'.

You can use 'sysctl -a |grep net.netfilter.nf_conntrack_tcp_timeout_' to view and change the system-wide defaults.
'ct timeout' allows for flow-specific settings, without changing the global timeouts.

For example, tcp port 53 could have much lower settings than other traffic.

udp state names that can have a specific timeout value are 'replied' and 'unreplied'.

.defining and assigning ct timeout policy
----------------------------------
table ip filter {
	ct timeout customtimeout {
		protocol tcp;
		l3proto ip
		policy = { established: 2m, close: 20s }
	}

	chain output {
		type filter hook output priority filter; policy accept;
		ct timeout set "customtimeout"
	}
}
----------------------------------

.testing the updated timeout policy
----------------------------------

% conntrack -E

It should display:

[UPDATE] tcp      6 120 ESTABLISHED src=172.16.19.128 dst=172.16.19.1
sport=22 dport=41360 [UNREPLIED] src=172.16.19.1 dst=172.16.19.128
sport=41360 dport=22
----------------------------------

CT EXPECTATION
~~~~~~~~~~~~~~
[verse]
*add* *ct expectation*  ['family'] 'table' 'name' *{ protocol* 'protocol' *; dport* 'dport' *; timeout* 'timeout' *; size* 'size' *; [*l3proto* 'family' *;*] *}*
*delete* *ct expectation*  ['family'] 'table' 'name'
*list* *ct expectations*

Ct expectation is used to create connection expectations. Expectations are
assigned with the *ct expectation set* statement. 'protocol', 'dport',
'timeout' and 'size' are mandatory, l3proto is derived from the table family
by default.

.conntrack expectation specifications
[options="header"]
|=================
|Keyword | Description | Type
|protocol |
layer 4 protocol of the expectation object |
string (e.g. ip)
|dport |
destination port of expected connection |
unsigned integer
|timeout |
timeout value for expectation |
unsigned integer
|size |
size value for expectation |
unsigned integer
|l3proto |
layer 3 protocol of the expectation object |
address family (e.g. ip)
|comment |
per ct expectation comment field |
string
|=================

.defining and assigning ct expectation policy
---------------------------------------------
table ip filter {
	ct expectation expect {
		protocol udp
		dport 9876
		timeout 2m
		size 8
		l3proto ip
	}

	chain input {
		type filter hook input priority filter; policy accept;
		ct expectation set "expect"
	}
}
----------------------------------

COUNTER
~~~~~~~
[verse]
*add* *counter* ['family'] 'table' 'name' [*{* [ *packets* 'packets' *bytes* 'bytes' ';' ] [ *comment* 'comment' ';' *}*]
*delete* *counter* ['family'] 'table' 'name'
*list* *counters*

.Counter specifications
[options="header"]
|=================
|Keyword | Description | Type
|packets |
initial count of packets |
unsigned integer (64 bit)
|bytes |
initial count of bytes |
unsigned integer (64 bit)
|comment |
per counter comment field |
string
|=================

.*Using named counters*
------------------
nft add counter filter http
nft add rule filter input tcp dport 80 counter name \"http\"
------------------

.*Using named counters with maps*
------------------
nft add counter filter http
nft add counter filter https
nft add rule filter input counter name tcp dport map { 80 : \"http\", 443 : \"https\" }
------------------

QUOTA
~~~~~
[verse]
*add* *quota* ['family'] 'table' 'name' *{* [*over*|*until*] 'bytes' 'BYTE_UNIT' [ *used* 'bytes' 'BYTE_UNIT' ] ';' [ *comment* 'comment' ';' ] *}*
BYTE_UNIT := bytes | kbytes | mbytes
*delete* *quota* ['family'] 'table' 'name'
*list* *quotas*

.Quota specifications
[options="header"]
|=================
|Keyword | Description | Type
|quota |
quota limit, used as the quota name |
Two arguments, unsigned integer (64 bit) and string: bytes, kbytes, mbytes.
"over" and "until" go before these arguments
|used |
initial value of used quota |
Two arguments, unsigned integer (64 bit) and string: bytes, kbytes, mbytes
|comment |
per quota comment field |
string
|=================

.*Using named quotas*
------------------
nft add quota filter user123 { over 20 mbytes }
nft add rule filter input ip saddr 192.168.10.123 quota name \"user123\"
------------------

.*Using named quotas with maps*
------------------
nft add quota filter user123 { over 20 mbytes }
nft add quota filter user124 { over 20 mbytes }
nft add rule filter input quota name ip saddr map { 192.168.10.123 : \"user123\", 192.168.10.124 : \"user124\" }
------------------