nftables (Magyar)

Related articles
iptables
Firewalld
nftables
is a netfilter project that aims to replace the existing {ip,ip6,arp,eb}tables framework. It provides a new packet filtering framework, a new user-space utility (nft), and a compatibility layer for {ip,ip6}tables. It uses the existing hooks, connection tracking system, user-space queueing component, and logging subsystem of netfilter.
It consists of three main components: a kernel implementation, the libnl
netlink
communication and the nftables user-space front-end.
The kernel provides a netlink configuration interface, as well as run-time rule-set evaluation, libnl contains the low-level functions for communicating with the kernel, and the nftables front-end is what the user interacts with via nft.
You can also visit the
official nftables wiki page
for more information.
Telepítés
Install
the userspace utilities package
nftables
.
Alternatively,
install
iptables-nft
[
Hibás hivatkozás
: replaced by
iptables
]
, which includes
nftables
as a dependency, will automatically uninstall
iptables
(an indirect dependency of the
base
meta package
) and prevent conflicts between
iptables
and
nftables
when used together. See
#Using iptables-nft
for details.
Note
iptables-nft
[
Hibás hivatkozás
: replaced by
iptables
]
works by providing implementations of the
iptables
commands that actually create and act on the
nftables
rules. However, rules created using the old
iptables-legacy
tools are separate objects, and
iptables-nft
will warn you if they are present.
Front-ends
Tip
Most
iptables front-ends
feature no direct or indirect support of nftables, but may introduce it.
[1]
One graphical front-end that supports both, nftables and iptables, is
firewalld
.
[2]
. Another one is
ufw
.
firewalld
(firewall-cmd)
— Daemon and console interface for configuring network and firewall zones as well as setting up and configuring firewall rules.
https://firewalld.org/
||
firewalld
nft-blackhole
— Script / daemon to blocking IP in nftables by country and black lists.
https://github.com/tomasz-c/nft-blackhole
||
nft-blackhole
AUR
ufw
— Ufw stands for Uncomplicated Firewall, and is a program for managing a netfilter firewall.
https://help.ubuntu.com/community/UFW
||
ufw
reaction
— A daemon that scans program outputs for repeated patterns, and takes action. A lightweight alternative to fail2ban.
https://framagit.org/ppom/reaction
||
reaction
AUR
Használat
Tip
If you already have an iptables rule, you can convert the iptables rule to an nftables rule, see
[3]
.
nftables
makes
no
distinction between temporary rules made in the command line and permanent ones loaded from or saved to a file.
All rules have to be created or loaded using
nft
command line utility.
Refer to
#Configuration
section on how to use.
Current ruleset can be printed with:
# nft list ruleset
Remove all ruleset leaving the system with no firewall:
# nft flush ruleset
Read ruleset from
/etc/nftables.conf
by
restarting
nftables.service
.
Simple firewall
nftables
comes with a simple and secure firewall configuration stored in the
/etc/nftables.conf
file.
The
nftables.service
will load rules from that file when
started or enabled
.
Configuration
nftables user-space utility
nft
performs most of the rule-set evaluation before handing rule-sets to the kernel. Rules are stored in chains, which in turn are stored in tables. The following sections indicate how to create and modify these constructs.
To read input from a file use the
-f
/
--file
option:
# nft --file
filename
Note that any rules already loaded are
not
automatically flushed.
See
nft(8)
for a complete list of all commands.
Tables
This article or section needs expansion.
Reason:
Clarify the difference between tables in iptables and nftables: in the latter they have a "namespacing" nature and can contain different chain types.
[4]
(Discuss in
Talk:Nftables (Magyar)
)
Tables hold
#Chains
. Unlike tables in iptables, there are no built-in tables in nftables. The number of tables and their names is up to the user. However, each table only has one address family and only applies to packets of this family. Tables can have one of five families specified:
nftables family
iptables utility
ip
iptables
ip6
ip6tables
inet
iptables and ip6tables
arp
arptables
bridge
ebtables
ip
(i.e. IPv4) is the default family and will be used if family is not specified.
To create one rule that applies to both IPv4 and IPv6, use
inet
.
inet
allows for the unification of the
ip
and
ip6
families to make defining rules for both easier.
See
nft(8) § ADDRESS FAMILIES
for a complete description of address families.
In all of the following,
family_type
is optional, and if not specified is set to
ip
.
Create table
The following adds a new table:
# nft add table
family_type
table_name
List tables
To list all tables:
# nft list tables
List chains and rules in a table
To list all chains and rules of a specified table:
# nft list table
family_type
table_name
For example, to list all the rules of the
my_table
table of the
inet
family:
# nft list table inet my_table
Delete table
To delete a table:
# nft delete table
family_type
table_name
This will destroy all chains in the table.
Flush table
To flush/clear all rules from a table:
# nft flush table
family_type
table_name
Chains
The purpose of chains is to hold
#Rules
. Unlike chains in iptables, there are no built-in chains in nftables. This means that if no chain uses any types or hooks in the netfilter framework, packets that would flow through those chains will not be touched by nftables, unlike iptables.
Chains have two types. A
base
chain is an entry point for packets from the networking stack, where a hook value is specified. A
regular
chain may be used as a jump target for better organization.
See the
traffic flow diagram
showing the ordering between individual hooks. Within a given hook, netfilter performs operations in order of increasing numerical priority.
In all of the following
family_type
is optional, and if not specified is set to
ip
.
Create chain
Base chain
To add a base chain it is mandatory to specify type, hook and priority values:
# nft add chain
family_type
table_name
chain_name
'{ type
chain_type
hook
hook_type
priority
priority_value
; policy
policy
;}'
chain_type
can be
filter
,
route
, or
nat
.
For IPv4/IPv6/Inet address families
hook_type
can be
prerouting
,
input
,
forward
,
output
, or
postrouting
. See
nft(8) § CHAINS
for a list of supported
family_type
,
chain_type
and
hook_type
combinations.
priority_value
takes either a priority name or an integer value. See
nft(8) § CHAINS
for a list of standard priority names and values. Chains with lower numbers are processed first and can be negative.
[5]
Optionally base chains can have a
policy
(
drop
or the default
accept
), to define what happens to packets not explicitly accepted or refused in contained rules.
For example, to add a base chain that filters input packets:
# nft add chain inet my_table my_chain '{ type filter hook input priority 0; }'
Replace
add
with
create
in any of the above to add a new chain but return an error if the chain already exists.
Regular chain
The following adds a regular chain named
chain_name
to the table named
table_name
:
# nft add chain
family_type
table_name
chain_name
For example, to add a regular chain named
my_tcp_chain
to the
my_table
table of the
inet
address family:
# nft add chain inet my_table my_tcp_chain
List chains
The following lists all chains without rules (see
#List rules
) of a
family_type
:
# nft list chains
family_type
For example, the following lists the chains of ipv6:
# nft list chains ip6
if you omit the family_type all chains are printed.
Edit a chain
To edit a chain, simply call it by its name and define the rules you want to change.
# nft chain
family_type table_name chain_name
'{ [ type
chain_type
hook
hook_type
device
device_name
priority
priority_value
; policy
policy_type
; ] }'
For example, to change the
my_input
chain policy of the default table from
accept
to
drop
# nft chain inet my_table my_input '{ policy drop ; }'
Delete a chain
To delete a chain:
# nft delete chain
family_type
table_name
chain_name
The chain must not contain any rules or be a jump target.
Flush rules from a chain
To flush rules from a chain:
# nft flush chain
family_type
table_name
chain_name
Rules
Rules are either constructed from expressions or statements and are contained within chains.
Add rule
To add a rule to a chain:
# nft add rule
family_type
table_name
chain_name
handle
handle_value
statement
The rule is appended at
handle_value
, which is optional. If not specified, the rule is appended to the end of the chain.
The
--handle
switch, which can be added to any valid list command, must be used to determine a rule handle. This switch tells
nft
to list the handles in its output. The
--numeric
argument is useful for viewing some numeric output, like unresolved IP addresses.
# nft --handle --numeric list chain inet my_table my_input
table inet my_table {
     chain input {
          type filter hook input priority 0;
          ip saddr 127.0.0.1 accept # handle 10
     }
}
To prepend the rule to the position:
# nft insert rule
family_type
table_name
chain_name
handle
handle_value
statement
If
handle_value
is not specified, the rule is prepended to the chain.
Expressions
Typically a
statement
includes some expression to be matched and then a verdict statement. Verdict statements include
accept
,
drop
,
queue
,
continue
,
return
,
jump
chain_name
, and
goto
chain_name
. Other statements than verdict statements are possible. See
nft(8)
for more information.
There are various expressions available in nftables and, for the most part, coincide with their iptables counterparts. The most noticeable difference is that there are no generic or implicit matches. A generic match was one that was always available, such as
--protocol
or
--source
. Implicit matches were protocol-specific, such as
--sport
when a packet was determined to be TCP.
The following is an incomplete list of the matches available:
meta    (meta properties, e.g. interfaces)
icmp    (ICMP protocol)
icmpv6  (ICMPv6 protocol)
ip      (IP protocol)
ip6     (IPv6 protocol)
tcp     (TCP protocol)
udp     (UDP protocol)
sctp    (SCTP protocol)
ct      (connection tracking)
The following is an incomplete list of match arguments (for a more complete list, see
nft(8)
):
meta:
  oif <output interface INDEX>
  iif <input interface INDEX>
  oifname <output interface NAME>
  iifname <input interface NAME>

  (oif and iif accept string arguments and are converted to interface indexes)
  (oifname and iifname are more dynamic, but slower because of string matching)

icmp:
  type <icmp type>

icmpv6:
  type <icmpv6 type>

ip:
  protocol <protocol>
  daddr <destination address>
  saddr <source address>

ip6:
  daddr <destination address>
  saddr <source address>

tcp:
  dport <destination port>
  sport <source port>

udp:
  dport <destination port>
  sport <source port>

sctp:
  dport <destination port>
  sport <source port>

ct:
  state <new | established | related | invalid>
List rules
The following lists all rules of a chain:
# nft list chain
family_type
table_name
chain_name
For example, the following lists the rules of the chain named
my_output
in the
inet
table named
my_table
:
# nft list chain inet my_table my_output
Deletion
Individual rules can only be deleted by their handles. Obtaining the handles was shown at
#Add rule
. Assuming
# nft --handle --numeric list chain inet my_table my_input
table inet my_table {
     chain input {
          type filter hook input priority 0;
          ip saddr 127.0.0.1 accept # handle 10
     }
}
# nft delete rule inet my_table my_input handle 10
deletes it.
All the chains in a table can be flushed with the
nft flush table
command. Individual chains can be flushed using either the
nft flush chain
or
nft delete rule
commands.
# nft flush table
table_name
# nft flush chain
family_type
table_name
chain_name
# nft delete rule
family_type
table_name
chain_name
The first command flushes all of the chains in the ip
table_name
table. The second flushes the
chain_name
chain in the
family_type
table_name
table. The third deletes all of the rules in
chain_name
chain in the
family_type
table_name
table.
Sets
Sets are named or anonymous
, and consist of one or more elements, separated by commas, enclosed by curly braces. Anonymous sets are embedded in rules and cannot be updated, you must delete and re-add the rule. E.g., you cannot just remove "http" from the dports set in the following:
# nft add rule ip6 filter input tcp dport {telnet, http, https} accept
Named sets can be updated, and can be typed and flagged.
sshguard
uses named sets for the IP addresses of blocked hosts.
table ip sshguard {
       set attackers {
               type ipv4_addr
               flags interval
               elements = { 1.2.3.4 }
       }
To
add
or
delete
elements from the set, use:
# nft add element ip sshguard attackers { 5.6.7.8/32 }
# nft delete element ip sshguard attackers { 1.2.3.4/32 }
Note the type
ipv4_addr
can include a CIDR netmask (the
/32
here is not necessary, but is included for completeness' sake). Note also, the set defined here by
TABLE ip sshguard { SET attackers }
is addressed as
ip sshguard attackers
.
Tip
systemd-networkd
connections can be configured to populate predefined named sets with host IP addresses, network prefixes and interface indexes. See the description of
NFTSet=
in
systemd.network(5) § [ADDRESS] SECTION OPTIONS
for details and
#Dynamic named sets using systemd-networkd
for an example.
Atomic reloading
Flush the current ruleset:
# echo "flush ruleset" > /tmp/nftables
Dump the current ruleset:
# nft -s list ruleset >> /tmp/nftables
Now you can edit
/tmp/nftables
and apply your changes with:
# nft -f /tmp/nftables
Examples
Workstation
/etc/nftables.conf
flush ruleset

table inet my_table {
	set LANv4 {
		type ipv4_addr
		flags interval

		elements = { 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16 }
	}
	set LANv6 {
		type ipv6_addr
		flags interval

		elements = { fd00::/8, fe80::/10 }
	}

	chain my_input_lan {
		udp sport 1900 udp dport >= 1024 meta pkttype unicast limit rate 4/second burst 20 packets accept comment "Accept UPnP IGD port mapping reply"

		udp sport netbios-ns udp dport >= 1024 meta pkttype unicast accept comment "Accept Samba Workgroup browsing replies"

	}

	chain my_input {
		type filter hook input priority filter; policy drop;

		iif lo accept comment "Accept any localhost traffic"
		ct state invalid drop comment "Drop invalid connections"
		fib daddr . iif type != { local, broadcast, multicast } drop comment "Drop packets if the destination IP address is not configured on the incoming interface (strong host model)"
		ct state { established, related } accept comment "Accept traffic originated from us"

		meta l4proto { icmp, ipv6-icmp } accept comment "Accept ICMP"
		ip protocol igmp accept comment "Accept IGMP"

		udp dport mdns ip6 daddr ff02::fb accept comment "Accept mDNS"
		udp dport mdns ip daddr 224.0.0.251 accept comment "Accept mDNS"

		ip6 saddr @LANv6 jump my_input_lan comment "Connections from private IP address ranges"
		ip saddr @LANv4 jump my_input_lan comment "Connections from private IP address ranges"

		counter comment "Count any other traffic"
	}

	chain my_forward {
		type filter hook forward priority filter; policy drop;
		# Drop everything forwarded to us. We do not forward. That is routers job.
	}

	chain my_output {
		type filter hook output priority filter; policy accept;
		# Accept every outbound connection
	}

}
Tip
When using
systemd-networkd
and connected to a local network, you can avoid hardcoding the network subnets by using the
systemd.network(5)
option
NFTSet=
to get the network prefixes of a connection. See
#Dynamic named sets using systemd-networkd
.
Server
/etc/nftables.conf
flush ruleset

table inet my_table {
	set LANv4 {
		type ipv4_addr
		flags interval

		elements = { 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16 }
	}
	set LANv6 {
		type ipv6_addr
		flags interval

		elements = { fd00::/8, fe80::/10 }
	}

	chain my_input_lan {
		meta l4proto { tcp, udp } th dport 2049 accept comment "Accept NFS"

		udp dport netbios-ns accept comment "Accept NetBIOS Name Service (nmbd)"
		udp dport netbios-dgm accept comment "Accept NetBIOS Datagram Service (nmbd)"
		tcp dport netbios-ssn accept comment "Accept NetBIOS Session Service (smbd)"
		tcp dport microsoft-ds accept comment "Accept Microsoft Directory Service (smbd)"

		udp sport { bootpc, 4011 } udp dport { bootps, 4011 } accept comment "Accept PXE"
		udp dport tftp accept comment "Accept TFTP"
	}

	chain my_input {
		type filter hook input priority filter; policy drop;

		iif lo accept comment "Accept any localhost traffic"
		ct state invalid drop comment "Drop invalid connections"
		fib daddr . iif type != { local, broadcast, multicast } drop comment "Drop packets if the destination IP address is not configured on the incoming interface (strong host model)"
		ct state { established, related } accept comment "Accept traffic originated from us"

		meta l4proto { icmp, ipv6-icmp } accept comment "Accept ICMP"
		ip protocol igmp accept comment "Accept IGMP"

		udp dport mdns ip6 daddr ff02::fb accept comment "Accept mDNS"
		udp dport mdns ip daddr 224.0.0.251 accept comment "Accept mDNS"

		ip6 saddr @LANv6 jump my_input_lan comment "Connections from private IP address ranges"
		ip saddr @LANv4 jump my_input_lan comment "Connections from private IP address ranges"

		tcp dport ssh accept comment "Accept SSH on port 22"

		tcp dport ipp accept comment "Accept IPP/IPPS on port 631"

		meta l4proto { tcp, udp } th dport { http, https, 8008, 8080 } accept comment "Accept HTTP (ports 80, 443, 8008, 8080)"

		udp sport bootpc udp dport bootps ip saddr 0.0.0.0 ip daddr 255.255.255.255 accept comment "Accept DHCPDISCOVER (for DHCP-Proxy)"
	}

	chain my_forward {
		type filter hook forward priority filter; policy drop;
		# Drop everything forwarded to us. We do not forward. That is routers job.
	}

	chain my_output {
		type filter hook output priority filter; policy accept;
		# Accept every outbound connection
	}

}
Limit rate
table inet my_table {
	chain my_input {
		type filter hook input priority filter; policy drop;

		iif lo accept comment "Accept any localhost traffic"
		ct state invalid drop comment "Drop invalid connections"
		fib daddr . iif type != { local, broadcast, multicast } drop comment "Drop packets if the destination IP address is not configured on the incoming interface (strong host model)"

		meta l4proto icmp icmp type echo-request limit rate over 10/second burst 4 packets drop comment "No ping floods"
		meta l4proto ipv6-icmp icmpv6 type echo-request limit rate over 10/second burst 4 packets drop comment "No ping floods"

		ct state { established, related } accept comment "Accept traffic originated from us"

		meta l4proto { icmp, ipv6-icmp } accept comment "Accept ICMP"
		ip protocol igmp accept comment "Accept IGMP"

		tcp dport ssh ct state new limit rate 15/minute accept comment "Avoid brute force on SSH"

	}

}
Jump
When using jumps in configuration file, it is necessary to define the target chain first. Otherwise one could end up with
Error: Could not process rule: No such file or directory
.
table inet my_table {
    chain web {
        tcp dport http accept
        tcp dport 8080 accept
    }
    chain my_input {
        type filter hook input priority filter;
        ip saddr 10.0.2.0/24 jump web
        drop
    }
}
Different rules for different interfaces
If your box has more than one network interface, and you would like to use different rules for different interfaces, you may want to use a "dispatching" filter chain, and then interface-specific filter chains. For example, let us assume your box acts as a home router, you want to run a web server accessible over the LAN (interface
enp3s0
), but not from the public internet (interface
enp2s0
), you may want to consider a structure like this:
table inet my_table {
  chain my_input { # this chain serves as a dispatcher
    type filter hook input priority filter; policy drop;

    iif lo accept comment "always accept loopback"
    iifname enp2s0 jump my_input_public
    iifname enp3s0 jump my_input_private
  }
  chain my_input_public { # rules applicable to public interface interface
    ct state {established,related} accept
    ct state invalid drop
    udp dport bootpc accept
    tcp dport bootpc accept
  }
  chain my_input_private {
    ct state {established,related} accept
    ct state invalid drop
    udp dport bootpc accept
    tcp dport bootpc accept
    tcp port http accept
    tcp port https accept
    reject with icmpx port-unreachable comment "all other traffic"
  }
  chain my_output { # we let everything out
    type filter hook output priority filter;
    accept
  }
}
Alternatively you could choose only one
iifname
statement, such as for the single upstream interface, and put the default rules for all other interfaces in one place, instead of dispatching for each interface.
Masquerading
nftables has a special keyword
masquerade
"where the source address is automagically set to the address of the output interface" (
source
). This is particularly useful for situations in which the IP address of the interface is unpredictable or unstable, such as the upstream interface of routers connecting to many ISPs. Without it, the Network Address Translation rules would have to be updated every time the IP address of the interface changed.
To use it:
make sure masquerading is enabled in the kernel (true if you use the default kernel), otherwise during kernel configuration, set
CONFIG_NFT_MASQ=m
.
the
masquerade
keyword can only be used in chains of type
nat
.
masquerading is a kind of source NAT, so only works in the output path.
Example for a machine with two interfaces: LAN connected to
enp3s0
, and public internet connected to
enp2s0
:
table inet my_nat {
  chain my_masquerade {
    type nat hook postrouting priority srcnat;
    oifname "enp2s0" masquerade
  }
}
Since the table type is
inet
both IPv4 and IPv6 packets will be masqueraded. If you want only ipv4 packets to be masqueraded (since extra adress space of IPv6 makes NAT not required)
meta nfproto ipv4
expression can be used infront of
oifname "enp2s0"
or the table type can be changed to
ip
.
NAT with port forwarding
This example will masquerade traffic exiting through a WAN interface called eth0 and forward ports 22 and 80 to
10.0.0.2
. You will need to set
net.ipv4.ip_forward
to
1
via
sysctl
.
table nat {
    chain prerouting {
        type nat hook prerouting priority dstnat;
        iif eth0 tcp dport {22, 80} dnat to 10.0.0.2
    }
    chain postrouting {
        type nat hook postrouting priority srcnat;
        oif eth0 masquerade
    }
}
Count new connections per IP
Use this snippet to count HTTPS connections:
/etc/nftables.conf
table inet filter {
    set https {
        type ipv4_addr;
        flags dynamic;
        size 65536;
        timeout 60m;
    }

    chain input {
        type filter hook input priority filter;
        ct state new meta l4proto { tcp, udp } th dport 443 update @https { ip saddr counter }
    }
}
To print the counters, run
nft list set inet filter https
.
Dynamic blackhole
Use this snippet to drop all HTTPS connections for 1 minute from a source IP (or /64 IPv6 range) that exceeds the limit of 10/second.
/etc/nftables.conf
table inet dev {
    set blackhole_ipv4 {
        type ipv4_addr;
        flags dynamic, timeout;
        size 65536;
    }
    set blackhole_ipv6 {
        type ipv6_addr;
        flags dynamic, timeout;
        size 65536;
    }

    chain input {
        type filter hook input priority filter; policy accept;
        ct state new meta l4proto { tcp, udp } th dport 443 \
                meter flood_ipv4 size 128000 { ip saddr timeout 10s limit rate over 10/second } \
                add @blackhole_ipv4 { ip saddr timeout 1m }
        ct state new meta l4proto { tcp, udp } th dport 443 \
                meter flood_ipv6 size 128000 { ip6 saddr and ffff:ffff:ffff:ffff:: timeout 10s limit rate over 10/second } \
                add @blackhole_ipv6 { ip6 saddr and ffff:ffff:ffff:ffff:: timeout 1m }

        ip saddr @blackhole_ipv4 counter drop
        ip6 saddr and ffff:ffff:ffff:ffff:: @blackhole_ipv6 counter drop
    }
}
To print the blackholed IPs, run
nft list set inet dev blackhole_ipv
X
.
Tips and tricks
Saving current rule set
The output of
nft list ruleset
command is a valid input file for it as well. Current rule set can be saved to file and later loaded back in.
# nft -s list ruleset | tee
filename
Note
nft list
does not output variable definitions, if you had any in your original file they will be lost. Any variables used in rules will be replaced by their value.
Simple stateful firewall
See
Simple stateful firewall
for more information.
Single machine
Flush the current ruleset:
# nft flush ruleset
Add a table:
# nft add table inet my_table
Add the input, forward, and output base chains. The policy for input and forward will be to drop. The policy for output will be to accept.
# nft add chain inet my_table my_input '{ type filter hook input priority 0 ; policy drop ; }'
# nft add chain inet my_table my_forward '{ type filter hook forward priority 0 ; policy drop ; }'
# nft add chain inet my_table my_output '{ type filter hook output priority 0 ; policy accept ; }'
Add two regular chains that will be associated with tcp and udp:
# nft add chain inet my_table my_tcp_chain
# nft add chain inet my_table my_udp_chain
Related and established traffic will be accepted:
# nft add rule inet my_table my_input ct state '{ related, established }' accept
All loopback interface traffic will be accepted:
# nft add rule inet my_table my_input iif lo accept
Drop any invalid traffic:
# nft add rule inet my_table my_input ct state invalid drop
Accept ICMP and IGMP:
# nft add rule inet my_table my_input meta l4proto '{ icmp, ipv6-icmp }' accept
# nft add rule inet my_table my_input ip protocol igmp accept
New udp traffic will jump to the UDP chain:
# nft add rule inet my_table my_input meta l4proto udp ct state new jump my_udp_chain
New tcp traffic will jump to the TCP chain:
# nft add rule inet my_table my_input 'meta l4proto tcp tcp flags & (fin|syn|rst|ack) == syn ct state new jump my_tcp_chain'
At this point you should decide what ports you want to open to incoming connections, which are handled by the TCP and UDP chains. For example to open connections for a web server add:
# nft add rule inet my_table my_tcp_chain tcp dport 80 accept
To accept HTTPS connections for a webserver on port 443:
# nft add rule inet my_table my_tcp_chain tcp dport 443 accept
# nft add rule inet my_table my_udp_chain udp dport 443 accept
To accept SSH traffic on port 22:
# nft add rule inet my_table my_tcp_chain tcp dport 22 accept
To accept incoming DNS requests:
# nft add rule inet my_table my_tcp_chain tcp dport 53 accept
# nft add rule inet my_table my_udp_chain udp dport 53 accept
Be sure to make your changes permanent when satisfied.
Prevent brute-force attacks
Sshguard
is program that can detect brute-force attacks and modify firewalls based on IP addresses it temporarily blacklists. See
Sshguard#nftables
on how to set up nftables to be used with it.
Logging traffic
You can log packets using the
log
action. The most simple rule to log all incoming traffic is:
# nft add rule inet filter input log
See
nftables wiki
for details.
Monitor
Listen to all events, report in native nft format.
# nft monitor
See
nft(8) § MONITOR
Ruleset debugging trace temporary
meta nftrace set 1
ruleset packet tracing on/off. Use
monitor trace
command to watch traces.
In another shell "include" the file inside the interactive shell:
# nft -i
nft> include "/root/nftables.trace"
Example, adjust to your needs:
/root/nftables.trace
add table ip temp-trace {comment "Temporary table!!"; flags owner;}
add chain ip temp-trace icmp-prerouting { type filter hook prerouting priority raw - 1 ; }
add rule ip temp-trace icmp-prerouting
ip protocol icmp
meta nftrace set 1
This file adds a temporary table (
flags owner
) so that it gets automatically removed, if the calling (process) interactive nft is closed. The Base Chain needs to be adjusted for your use case. You can create multiple chains and multiple rules with "meta nftrace set 1"  "ip protocol icmp" is used just as an example and is not necessary. There are many ways to achieve a similar effect, the advantage is that by closing the interactive shell the previous state is automatically restored, and if an error is inside the file nothing gets executed.
See
nftables wiki
and a
python tool automating
the process and coloring.
Using iptables-nft
The factual accuracy of this article or section is disputed.
Reason:
nftables warns if there are legacy iptables objects loaded, so it is not "perfectly workable to use legacy iptables
and
nftables at the same time". (Discuss in
Talk:Nftables (Magyar)
)
The older iptables language remains quite dominant in Linux documentation, and quite a few things still depend on iptables to run (such as Docker's networking). Although it's also perfectly workable to use legacy iptables
and
nftables at the same time, using iptables-nft's translation is preferred because:
It puts everything in the same place, using the newer, more efficient, non-locking framework.
It checks for conflicts.
There are two ways to use the old iptables language with nftables:
iptables-translate
and
iptables-restore-translate
(plus vice versa for
ip6tables
,
ebtables
, etc.) take iptable language and output nft language. They do
not
change running nft settings. See
xtables-translate(8)
.
For configuration you want to maintain later on, it's a good idea to use the
-translate
tool and integrate the result code into your existing rules. For example, if you find something useful in
simple stateful firewall
or the wider Internet, you can translate them to put into your nft config.
iptables
and
iptables-restore
(again vice versa for
ip6tables
etc.) uses the above translation
and
put them into the running nft settings. It also offers statistics like regular iptables does. See
xtables-nft(8)
.
Those commands work reasonably well given what they have to work with. They should "just work" with simple usage, but occasionally you will need to step in and debug.
Note
The translator covers a large portion, but not all, of the iptables language. Some iptables rules work in conjunction and the translator needs context to properly translate, so do not panic if some lines translate into nothing.
Dynamic named sets using systemd-networkd
systemd-networkd
's connections can use the
NFTSet=
option to populate predefined named sets with host IP addresses, network prefixes and interface indexes. This allows to avoid hardcoding them in
/etc/nftables.conf
. The
NFTSet=
option is supported in
[Address]
,
[DHCPv4]
,
[DHCPv6]
and
[IPv6AcceptRA]
sections. See
systemd.network(5) § [ADDRESS] SECTION OPTIONS
.
For example, to process connections from a local network (where IP addresses are assigned via DHCP or SLAAC) in a separate
my_input_lan
chain:
/etc/nftables.conf
...
table inet my_table {

	set eth_ipv4_prefix {
		type ipv4_addr
		flags interval
		comment "Populated by systemd-networkd"
	}
	set eth_ipv6_prefix {
		type ipv6_addr
		flags interval
		comment "Populated by systemd-networkd"

		elements = { fe80::/10 }
	}
	set eth_ifindex {
		type iface_index
		comment "Populated by systemd-networkd"
	}
...
	chain my_input {
		type filter hook input priority filter; policy drop;

		iif @eth_ifindex ip6 saddr @eth_ipv6_prefix jump my_input_lan comment "Connections from LAN"
		iif @eth_ifindex ip saddr @eth_ipv4_prefix jump my_input_lan comment "Connections from LAN"
	}
...
}
/etc/systemd/network/my-network.network
...

[DHCPv4]
NFTSet=prefix:inet:my_table:eth_ipv4_prefix
NFTSet=ifindex:inet:my_table:eth_ifindex

[DHCPv6]
NFTSet=prefix:inet:my_table:eth_ipv6_prefix
NFTSet=ifindex:inet:my_table:eth_ifindex

[IPv6AcceptRA]
NFTSet=prefix:inet:my_table:eth_ipv6_prefix
NFTSet=ifindex:inet:my_table:eth_ifindex
...
Troubleshooting
Working with Docker
Note
With the following setup, you will not be able to use protocols like
AF_BLUETOOTH
inside containers even with
--net host --privileged
.
Rootless Docker containers already run in a separate network namespace. You may not need to do anything.
Using nftables can interfere with
Docker
networking (and probably other container runtimes as well). You can find various workarounds on the internet which either involve patching iptables rules and ensuring a defined service start order or disabling dockers iptables management completely which makes using docker very restrictive (think port forwarding or docker-compose).
A reliable method is letting docker run in a separate network namespace where it can do whatever it wants. It is probably best to
not
use
iptables-nft
[
Hibás hivatkozás
: replaced by
iptables
]
to prevent docker from mixing nftables and iptables rules.
Use the following docker service
drop-in file
:
/etc/systemd/system/docker.service.d/netns.conf
[Service]
PrivateNetwork=yes
PrivateMounts=No

# cleanup
ExecStartPre=-nsenter -t 1 -n -- ip link delete docker0

# add veth
ExecStartPre=nsenter -t 1 -n -- ip link add docker0 type veth peer name docker0_ns
ExecStartPre=sh -c 'nsenter -t 1 -n -- ip link set docker0_ns netns "$$BASHPID" && true'
ExecStartPre=ip link set docker0_ns name eth0

# bring host online
ExecStartPre=nsenter -t 1 -n -- ip addr add 10.0.0.1/24 dev docker0
ExecStartPre=nsenter -t 1 -n -- ip link set docker0 up

# bring ns online
ExecStartPre=ip addr add 10.0.0.100/24 dev eth0
ExecStartPre=ip link set eth0 up
ExecStartPre=ip route add default via 10.0.0.1 dev eth0
Adjust the
10.0.0.*
IP addresses if they are not appropriate for your setup.
Enable IP forwarding and set-up NAT for docker0 with the following postrouting rule:
iifname docker0 oifname eth0 masquerade
Then, ensure that
kernel IP forwarding
is enabled.
Now you can setup a firewall and port forwarding for the
docker0
interface using nftables without any interference.
További olvasnivaló a témában
netfilter nftables wiki
debian:nftables
gentoo:nftables
First release of nftables
nftables quick howto
The return of nftables
What comes after ‘iptables’? Its successor, of course: `nftables`
Gene's Tech Blog
– additional nftables samples for workstation and firewall