Bİlgisayar Ağları - Ders 9 - Nftables

Nftables, ağ paketlerinin, ağ datagramlarının, ağ çerçevelerinin filtrelenmesini ve sınıflandırılmasını sağlayan Linux çekirdeğinin bir alt sistemidir.

Linux çekirdeği 3.13'te çalışır.

Iptables'in yeni sürümü olarak görülebilir ancak söz dizimi iptables'tan farklıdır. Aynı zamanda iptables komutlarının da çalıştırılmasına izin verilen bir uyumluluk modu vardır.

En önemli yeniliği kural sayısını çok fazla azaltmasıdır.

Nftables Kurulumu

sudo apt-get install nftables

komutu ile kurulum gerçekleştirilir.

Nfrables Tablo(Table), Zincir(Chain), Kural(Rule) Kavramları

Tablo, belirli bir semantik içermeyen bir zincirler konteynırını ifade eder.
Bir tablodaki zincir, bir kurallar konteynırını ifade eder.
Kural, bir zincir içinde yapılandırılacak bir eylemi ifade eder.

Nftables Tablo İşlemleri

Tablo Oluşturmak, Silmek, Flush İşlemleri

nft (add | delete | flush) table [<family>] <isim>

Var Olan Tabloları Listeletmek

nft list tables [<family>]
nft list table [<family>] <name> [-n] [-a]

Family bu tablo türlerinden birine karşılık gelir: ip, arp, ip6, bridge, inet, netdev.

-n argümanı, adresleri ve diğer bilgileri gösterir. -a argümanı, handle'ı görüntülemek için kullanılır.

Nftables Zincir İşlemleri

Zincir Ekleme ve Oluşturma

nft (add | create) chain [<family>] <table> <name> [ { type <type> hook <hook> [device <device>] priority <priority> \; [policy <policy> \;] } ]

Zincir Silme ve Var Olan Zicirleri Listeleme

nft (delete | list | flush) chain [<family>] <table> <name>

Zincirin İsmini Değiştirme

nft rename chain [<family>] <table> <name> <newname>

type parametresi oluşturulacak zincirin türünü belirtir.

filter : Arp, bridge, IP, IPv6 ve inet tarafından desteklenir.
route : Çıkış işlemleri için kullanılır. IP VE IPv6 tarafından desteklenir.
nat : Ağ adresi çevirisi gerçekleştirmek için kullanılır. IP ve IPv6 tarafından desteklenir.

hook parametresi çekirdekte işlenecek paketlerin aşamasını belirtir.

IP, IPv6 ve inet için hook, prerouting, input, forward, output, postrouting.
Arp için hook, input, output.
Bridge için hook, köprü aygıtlarını geçen ethernet paketlerini yönetir.
Netdev için hook, ingress.

priority, Zincirleri sipariş etmek veya bazı Netfilter işlemleri arasında ayarlamak için kullanılan bir numarayı belirtir. Olası değerler:

NF_IP_PRI_CONNTRACK_DEFRAG (-400)
NF_IP_PRI_RAW (-300)
NF_IP_PRI_SELINUX_FIRST (-225)
NF_IP_PRI_CONNTRACK (-200)
NF_IP_PRI_MANGLE (-150)
NF_IP_PRI_NAT_DST (-100)
NF_IP_PRI_FILTER (0)
NF_IP_PRI_SECURITY (50)
NF_IP_PRI_NAT_SRC (100)
NF_IP_PRI_SELINUX_LAST (225)
NF_IP_PRI_CONNTRACK_HELPER (300)

policy, parametresi zincirde ki paketlere ne yapılacağını belirtir. Olası değerler:

accept (Kabul Et)
drop (DÜşür)
queue (Kuyruk)
continue (Devam)
return (Geri Dön)

Nftables Kural İşlemleri

Kural Ekleme

nft add rule [<family>] <table> <chain> <matches> <statements>

Araya Kural Ekleme

nft insert rule [<family>] <table> <chain> [position <position>] <matches> <statements>

Kural Değiştirme

nft replace rule [<family>] <table> <chain> [handle <handle>] <matches> <statements>

Kural Silme

nft delete rule [<family>] <table> <chain> [handle <handle>]

handle parametresi belirli bir kuralı tanımlayan dahili bir sayıdır.

position parametresi belirli bir handle'dan önce bir kural eklemek için kullanılan dahili bir sayıdır.

Matches Parametresi

ip match
dscp <value>		ip dscp cs1 ip dscp != cs1 ip dscp 0x38 ip dscp != 0x20 ip dscp {cs0, cs1, cs2, cs3, cs4, cs5, cs6, cs7, af11, af12, af13, af21, af22, af23, af31, af32, af33, af41, af42, af43, ef}
length <length>	Total packet length	ip length 232 ip length != 233 ip length 333-435 ip length != 333-453 ip length { 333, 553, 673, 838}
id <id>	IP ID	ip id 22 ip id != 233 ip id 33-45 ip id != 33-45 ip id { 33, 55, 67, 88 }
frag-off <value>	Fragmentation offset	ip frag-off 222 ip frag-off != 233 ip frag-off 33-45 ip frag-off != 33-45 ip frag-off { 33, 55, 67, 88 }
ttl <ttl>	Time to live	ip ttl 0 ip ttl 233 ip ttl 33-55 ip ttl != 45-50 ip ttl { 43, 53, 45 } ip ttl { 33-55 }
protocol <protocol>	Upper layer protocol	ip protocol tcp ip protocol 6 ip protocol != tcp ip protocol { icmp, esp, ah, comp, udp, udplite, tcp, dccp, sctp }
checksum <checksum>	IP header checksum	ip checksum 13172 ip checksum 22 ip checksum != 233 ip checksum 33-45 ip checksum != 33-45 ip checksum { 33, 55, 67, 88 } ip checksum { 33-55 }
saddr <ip source address>	Source address	ip saddr 192.168.2.0/24 ip saddr != 192.168.2.0/24 ip saddr 192.168.3.1 ip daddr 192.168.3.100 ip saddr != 1.1.1.1 ip saddr 1.1.1.1 ip saddr & 0xff == 1 ip saddr & 0.0.0.255 < 0.0.0.127
daddr <ip destination address>	Destination address	ip daddr 192.168.0.1 ip daddr != 192.168.0.1 ip daddr 192.168.0.1-192.168.0.250 ip daddr 10.0.0.0-10.255.255.255 ip daddr 172.16.0.0-172.31.255.255 ip daddr 192.168.3.1-192.168.4.250 ip daddr != 192.168.0.1-192.168.0.250 ip daddr { 192.168.0.1-192.168.0.250 } ip daddr { 192.168.5.1, 192.168.5.2, 192.168.5.3 }
version <version>	Ip Header version	ip version 4
hdrlength <header length>	IP header length	ip hdrlength 0 ip hdrlength 15

Ip6

ip6 match
dscp <value>		ip6 dscp cs1 ip6 dscp != cs1 ip6 dscp 0x38 ip6 dscp != 0x20 ip6 dscp {cs0, cs1, cs2, cs3, cs4, cs5, cs6, cs7, af11, af12, af13, af21, af22, af23, af31, af32, af33, af41, af42, af43, ef}
flowlabel <label>	Flow label	ip6 flowlabel 22 ip6 flowlabel != 233 ip6 flowlabel { 33, 55, 67, 88 } ip6 flowlabel { 33-55 }
length <length>	Payload length	ip6 length 232 ip6 length != 233 ip6 length 333-435 ip6 length != 333-453 ip6 length { 333, 553, 673, 838}
nexthdr <header>	Next header type (Upper layer protocol number)	ip6 nexthdr {esp, udp, ah, comp, udplite, tcp, dccp, sctp, icmpv6} ip6 nexthdr esp ip6 nexthdr != esp ip6 nexthdr { 33-44 } ip6 nexthdr 33-44 ip6 nexthdr != 33-44
hoplimit <hoplimit>	Hop limit	ip6 hoplimit 1 ip6 hoplimit != 233 ip6 hoplimit 33-45 ip6 hoplimit != 33-45 ip6 hoplimit {33, 55, 67, 88} ip6 hoplimit {33-55}
saddr <ip source address>	Source Address	ip6 saddr 1234:1234:1234:1234:1234:1234:1234:1234 ip6 saddr ::1234:1234:1234:1234:1234:1234:1234 ip6 saddr ::/64 ip6 saddr ::1 ip6 daddr ::2
daddr <ip destination address>	Destination Address	ip6 daddr 1234:1234:1234:1234:1234:1234:1234:1234 ip6 daddr != ::1234:1234:1234:1234:1234:1234:1234-1234:1234::1234:1234:1234:1234:1234
version <version>	IP header version	ip6 version 6

Tcp

tcp match
dport <destination port>	Destination port	tcp dport 22 tcp dport != 33-45 tcp dport { 33-55 } tcp dport {telnet, http, https } tcp dport vmap { 22 : accept, 23 : drop } tcp dport vmap { 25:accept, 28:drop }
sport < source port>	Source port	tcp sport 22 tcp sport != 33-45 tcp sport { 33, 55, 67, 88} tcp sport { 33-55} tcp sport vmap { 25:accept, 28:drop } tcp sport 1024 tcp dport 22
sequence <value>	Sequence number	tcp sequence 22 tcp sequence != 33-45
ackseq <value>	Acknowledgement number	tcp ackseq 22 tcp ackseq != 33-45 tcp ackseq { 33, 55, 67, 88 } tcp ackseq { 33-55 }
flags <flags>	TCP flags	tcp flags { fin, syn, rst, psh, ack, urg, ecn, cwr} tcp flags cwr tcp flags != cwr
window <value>	Window	tcp window 22 tcp window != 33-45 tcp window { 33, 55, 67, 88 } tcp window { 33-55 }
checksum <checksum>	IP header checksum	tcp checksum 22 tcp checksum != 33-45 tcp checksum { 33, 55, 67, 88 } tcp checksum { 33-55 }
urgptr <pointer>	Urgent pointer	tcp urgptr 22 tcp urgptr != 33-45 tcp urgptr { 33, 55, 67, 88 }
doff <offset>	Data offset	tcp doff 8

Udp

udp match
dport <destination port>	Destination port	udp dport 22 udp dport != 33-45 udp dport { 33-55 } udp dport {telnet, http, https } udp dport vmap { 22 : accept, 23 : drop } udp dport vmap { 25:accept, 28:drop }
sport < source port>	Source port	udp sport 22 udp sport != 33-45 udp sport { 33, 55, 67, 88} udp sport { 33-55} udp sport vmap { 25:accept, 28:drop } udp sport 1024 tcp dport 22
length <length>	Total packet length	udp length 6666 udp length != 50-65 udp length { 50, 65 } udp length { 35-50 }
checksum <checksum>	UDP checksum	udp checksum 22 udp checksum != 33-45 udp checksum { 33, 55, 67, 88 } udp checksum { 33-55 }

Udplite

udplite match
dport <destination port>	Destination port	udplite dport 22 udplite dport != 33-45 udplite dport { 33-55 } udplite dport {telnet, http, https } udplite dport vmap { 22 : accept, 23 : drop } udplite dport vmap { 25:accept, 28:drop }
sport < source port>	Source port	udplite sport 22 udplite sport != 33-45 udplite sport { 33, 55, 67, 88} udplite sport { 33-55} udplite sport vmap { 25:accept, 28:drop } udplite sport 1024 tcp dport 22
checksum <checksum>	Checksum	udplite checksum 22 udplite checksum != 33-45 udplite checksum { 33, 55, 67, 88 } udplite checksum { 33-55 }

udplite match

dport <destination port>

Destination port

udplite dport 22
udplite dport != 33-45
udplite dport { 33-55 }
udplite dport {telnet, http, https }
udplite dport vmap { 22 : accept, 23 : drop }
udplite dport vmap { 25:accept, 28:drop }

sport < source port>

Source port

udplite sport 22
udplite sport != 33-45
udplite sport { 33, 55, 67, 88}
udplite sport { 33-55}
udplite sport vmap { 25:accept, 28:drop }
udplite sport 1024 tcp dport 22

checksum <checksum>

Checksum

udplite checksum 22
udplite checksum != 33-45
udplite checksum { 33, 55, 67, 88 }
udplite checksum { 33-55 }

Sctp

sctp match
dport <destination port>	Destination port	sctp dport 22 sctp dport != 33-45 sctp dport { 33-55 } sctp dport {telnet, http, https } sctp dport vmap { 22 : accept, 23 : drop } sctp dport vmap { 25:accept, 28:drop }
sport < source port>	Source port	sctp sport 22 sctp sport != 33-45 sctp sport { 33, 55, 67, 88} sctp sport { 33-55} sctp sport vmap { 25:accept, 28:drop } sctp sport 1024 tcp dport 22
checksum <checksum>	Checksum	sctp checksum 22 sctp checksum != 33-45 sctp checksum { 33, 55, 67, 88 } sctp checksum { 33-55 }
vtag <tag>	Verification tag	sctp vtag 22 sctp vtag != 33-45 sctp vtag { 33, 55, 67, 88 } sctp vtag { 33-55 }

Dccp

dccp match
dport <destination port>	Destination port	dccp dport 22 dccp dport != 33-45 dccp dport { 33-55 } dccp dport {telnet, http, https } dccp dport vmap { 22 : accept, 23 : drop } dccp dport vmap { 25:accept, 28:drop }
sport < source port>	Source port	dccp sport 22 dccp sport != 33-45 dccp sport { 33, 55, 67, 88} dccp sport { 33-55} dccp sport vmap { 25:accept, 28:drop } dccp sport 1024 tcp dport 22
type <type>	Type of packet	dccp type {request, response, data, ack, dataack, closereq, close, reset, sync, syncack} dccp type request dccp type != request

dccp match

dport <destination port>

Destination port

dccp dport 22
dccp dport != 33-45
dccp dport { 33-55 }
dccp dport {telnet, http, https }
dccp dport vmap { 22 : accept, 23 : drop }
dccp dport vmap { 25:accept, 28:drop }

sport < source port>

Source port

dccp sport 22
dccp sport != 33-45
dccp sport { 33, 55, 67, 88}
dccp sport { 33-55}
dccp sport vmap { 25:accept, 28:drop }
dccp sport 1024 tcp dport 22

type <type>

Type of packet

dccp type {request, response, data, ack, dataack, closereq, close, reset, sync, syncack}
dccp type request
dccp type != request

Ah

ah match
hdrlength <length>	AH header length	ah hdrlength 11-23 ah hdrlength != 11-23 ah hdrlength {11, 23, 44 }
reserved <value>		ah reserved 22 ah reserved != 33-45 ah reserved {23, 100 } ah reserved { 33-55 }
spi <value>		ah spi 111 ah spi != 111-222 ah spi {111, 122 }
sequence <sequence>	Sequence Number	ah sequence 123 ah sequence {23, 25, 33} ah sequence != 23-33

Esp

esp match
spi <value>		esp spi 111 esp spi != 111-222 esp spi {111, 122 }
sequence <sequence>	Sequence Number	esp sequence 123 esp sequence {23, 25, 33} esp sequence != 23-33

Comp

comp match
nexthdr <protocol>	Next header protocol (Upper layer protocol)	comp nexthdr != esp comp nexthdr {esp, ah, comp, udp, udplite, tcp, tcp, dccp, sctp}
flags <flags>	Flags	comp flags 0x0 comp flags != 0x33-0x45 comp flags {0x33, 0x55, 0x67, 0x88}
cpi <value>	Compression Parameter Index	comp cpi 22 comp cpi != 33-45 comp cpi {33, 55, 67, 88}

comp match

nexthdr <protocol>

Next header protocol (Upper layer protocol)

comp nexthdr != esp
comp nexthdr {esp, ah, comp, udp, udplite, tcp, tcp, dccp, sctp}

flags <flags>

Flags

comp flags 0x0
comp flags != 0x33-0x45
comp flags {0x33, 0x55, 0x67, 0x88}

cpi <value>

Compression Parameter Index

comp cpi 22
comp cpi != 33-45
comp cpi {33, 55, 67, 88}

Icmp

icmp match
type <type>	ICMP packet type	icmp type {echo-reply, destination-unreachable, source-quench, redirect, echo-request, time-exceeded, parameter-problem, timestamp-request, timestamp-reply, info-request, info-reply, address-mask-request, address-mask-reply, router-advertisement, router-solicitation}
code	ICMP packet code	icmp code 111 icmp code != 33-55 icmp code { 2, 4, 54, 33, 56}
checksum <value>	ICMP packet checksum	icmp checksum 12343 icmp checksum != 11-343 icmp checksum { 1111, 222, 343 }
id <value>	ICMP packet id	icmp id 12343 icmp id != 11-343 icmp id { 1111, 222, 343 }
sequence <value>	ICMP packet sequence	icmp sequence 12343 icmp sequence != 11-343 icmp sequence { 1111, 222, 343 }
mtu <value>	ICMP packet mtu	icmp mtu 12343 icmp mtu != 11-343 icmp mtu { 1111, 222, 343 }
gateway <value>	ICMP packet gateway	icmp gateway 12343 icmp gateway != 11-343 icmp gateway { 1111, 222, 343 }

Icmpv6

icmpv6 match
type <type>	ICMPv6 packet type	icmpv6 type {destination-unreachable, packet-too-big, time-exceeded, echo-request, echo-reply, mld-listener-query, mld-listener-report, mld-listener-reduction, nd-router-solicit, nd-router-advert, nd-neighbor-solicit, nd-neighbor-advert, nd-redirect, parameter-problem, router-renumbering}
code <code>	ICMPv6 packet code	icmpv6 code 4 icmpv6 code 3-66 icmpv6 code {5, 6, 7}
checksum <value>	ICMPv6 packet checksum	icmpv6 checksum 12343 icmpv6 checksum != 11-343 icmpv6 checksum { 1111, 222, 343 }
id <value>	ICMPv6 packet id	icmpv6 id 12343 icmpv6 id != 11-343 icmpv6 id { 1111, 222, 343 }
sequence <value>	ICMPv6 packet sequence	icmpv6 sequence 12343 icmpv6 sequence != 11-343 icmpv6 sequence { 1111, 222, 343 }
mtu <value>	ICMPv6 packet mtu	icmpv6 mtu 12343 icmpv6 mtu != 11-343 icmpv6 mtu { 1111, 222, 343 }
max-delay <value>	ICMPv6 packet max delay	icmpv6 max-delay 33-45 icmpv6 max-delay != 33-45 icmpv6 max-delay {33, 55, 67, 88}

Ether

ether match
saddr <mac address>	Source mac address	ether saddr 00:0f:54:0c:11:04
type <type>		ether type vlan

Dst

dst match
nexthdr <proto>	Next protocol header	dst nexthdr { udplite, ipcomp, udp, ah, sctp, esp, dccp, tcp, ipv6-icmp} dst nexthdr 22 dst nexthdr != 33-45
hdrlength <length>	Header Length	dst hdrlength 22 dst hdrlength != 33-45 dst hdrlength { 33, 55, 67, 88 }

Frag

frag match
nexthdr <proto>	Next protocol header	frag nexthdr { udplite, comp, udp, ah, sctp, esp, dccp, tcp, ipv6-icmp, icmp} frag nexthdr 6 frag nexthdr != 50-51
reserved <value>		frag reserved 22 frag reserved != 33-45 frag reserved { 33, 55, 67, 88}
frag-off <value>		frag frag-off 22 frag frag-off != 33-45 frag frag-off { 33, 55, 67, 88}
more-fragments <value>		frag more-fragments 0 frag more-fragments 0
id <value>		frag id 1 frag id 33-45

Hbh

hbh match
nexthdr <proto>	Next protocol header	hbh nexthdr { udplite, comp, udp, ah, sctp, esp, dccp, tcp, icmpv6} hbh nexthdr 22 hbh nexthdr != 33-45
hdrlength <length>	Header Length	hbh hdrlength 22 hbh hdrlength != 33-45 hbh hdrlength { 33, 55, 67, 88 }

Mh

mh match
nexthdr <proto>	Next protocol header	mh nexthdr { udplite, ipcomp, udp, ah, sctp, esp, dccp, tcp, ipv6-icmp } mh nexthdr 22 mh nexthdr != 33-45
hdrlength <length>	Header Length	mh hdrlength 22 mh hdrlength != 33-45 mh hdrlength { 33, 55, 67, 88 }
type <type>		mh type {binding-refresh-request, home-test-init, careof-test-init, home-test, careof-test, binding-update, binding-acknowledgement, binding-error, fast-binding-update, fast-binding-acknowledgement, fast-binding-advertisement, experimental-mobility-header, home-agent-switch-message} mh type home-agent-switch-message mh type != home-agent-switch-message
reserved <value>		mh reserved 22 mh reserved != 33-45 mh reserved { 33, 55, 67, 88}
checksum <value>		mh checksum 22 mh checksum != 33-45 mh checksum { 33, 55, 67, 88}

Rt

rt match
nexthdr <proto>	Next protocol header	rt nexthdr { udplite, ipcomp, udp, ah, sctp, esp, dccp, tcp, ipv6-icmp } rt nexthdr 22 rt nexthdr != 33-45
hdrlength <length>	Header Length	rt hdrlength 22 rt hdrlength != 33-45 rt hdrlength { 33, 55, 67, 88 }
type <type>		rt type 22 rt type != 33-45 rt type { 33, 55, 67, 88 }
seg-left <value>		rt seg-left 22 rt seg-left != 33-45 rt seg-left { 33, 55, 67, 88}

Vlan

vlan match
id <value>	Vlan tag ID	vlan id 4094 vlan id 0
cfi <value>		vlan cfi 0 vlan cfi 1
pcp <value>		vlan pcp 7 vlan pcp 3

Arp

arp match
ptype <value>	Payload type	arp ptype 0x0800
htype <value>	Header type	arp htype 1 arp htype != 33-45 arp htype { 33, 55, 67, 88}
hlen <length>	Header Length	arp hlen 1 arp hlen != 33-45 arp hlen { 33, 55, 67, 88}
plen <length>	Payload length	arp plen 1 arp plen != 33-45 arp plen { 33, 55, 67, 88}
operation <value>		arp operation {nak, inreply, inrequest, rreply, rrequest, reply, request}

Ct

ct match
state <state>	State of the connection	ct state { new, established, related, untracked } ct state != related ct state established ct state 8
direction <value>	Direction of the packet relative to the connection	ct direction original ct direction != original ct direction {reply, original}
status <status>	Status of the connection	ct status expected ct status != expected ct status {expected,seen-reply,assured,confirmed,snat,dnat,dying}
mark [set]	Mark of the connection	ct mark 0 ct mark or 0x23 == 0x11 ct mark or 0x3 != 0x1 ct mark and 0x23 == 0x11 ct mark and 0x3 != 0x1 ct mark xor 0x23 == 0x11 ct mark xor 0x3 != 0x1 ct mark 0x00000032 ct mark != 0x00000032 ct mark 0x00000032-0x00000045 ct mark != 0x00000032-0x00000045 ct mark {0x32, 0x2222, 0x42de3} ct mark {0x32-0x2222, 0x4444-0x42de3} ct mark set 0x11 xor 0x1331 ct mark set 0x11333 and 0x11 ct mark set 0x12 or 0x11 ct mark set 0x11 ct mark set mark ct mark set mark map { 1 : 10, 2 : 20, 3 : 30 }
expiration	Connection expiration time	ct expiration 30 ct expiration 30s ct expiration != 233 ct expiration != 3m53s ct expiration 33-45 ct expiration 33s-45s ct expiration != 33-45 ct expiration != 33s-45s ct expiration {33, 55, 67, 88} ct expiration { 1m7s, 33s, 55s, 1m28s}
helper "<helper>"	Helper associated with the connection	ct helper "ftp"
[original \| reply] bytes <value>		ct original bytes > 100000 ct bytes > 100000
[original \| reply] packets <value>		ct reply packets < 100
[original \| reply] saddr <ip source address>		ct original saddr 192.168.0.1 ct reply saddr 192.168.0.1 ct original saddr 192.168.1.0/24 ct reply saddr 192.168.1.0/24
[original \| reply] daddr <ip destination address>		ct original daddr 192.168.0.1 ct reply daddr 192.168.0.1 ct original daddr 192.168.1.0/24 ct reply daddr 192.168.1.0/24
[original \| reply] l3proto <protocol>		ct original l3proto ipv4
[original \| reply] protocol <protocol>		ct original protocol 6
[original \| reply] proto-dst <port>		ct original proto-dst 22
[original \| reply] proto-src <port>		ct reply proto-src 53

Meta

meta match
iifname <input interface name>	Input interface name	meta iifname "eth0" meta iifname != "eth0" meta iifname {"eth0", "lo"} meta iifname "eth*"
oifname <output interface name>	Output interface name	meta oifname "eth0" meta oifname != "eth0" meta oifname {"eth0", "lo"} meta oifname "eth*"
iif <input interface index>	Input interface index	meta iif eth0 meta iif != eth0
oif <output interface index>	Output interface index	meta oif lo meta oif != lo meta oif {eth0, lo}
iiftype <input interface type>	Input interface type	meta iiftype {ether, ppp, ipip, ipip6, loopback, sit, ipgre} meta iiftype != ether meta iiftype ether
oiftype <output interface type>	Output interface hardware type	meta oiftype {ether, ppp, ipip, ipip6, loopback, sit, ipgre} meta oiftype != ether meta oiftype ether
length <length>	Length of the packet in bytes	meta length 1000 meta length != 1000 meta length > 1000 meta length 33-45 meta length != 33-45 meta length { 33, 55, 67, 88 } meta length { 33-55, 67-88 }
protocol <protocol>	ethertype protocol	meta protocol ip meta protocol != ip meta protocol { ip, arp, ip6, vlan }
nfproto <protocol>		meta nfproto ipv4 meta nfproto != ipv6 meta nfproto { ipv4, ipv6 }
l4proto <protocol>		meta l4proto 22 meta l4proto != 233 meta l4proto 33-45 meta l4proto { 33, 55, 67, 88 } meta l4proto { 33-55 }
mark [set] <mark>	Packet mark	meta mark 0x4 meta mark 0x00000032 meta mark and 0x03 == 0x01 meta mark and 0x03 != 0x01 meta mark != 0x10 meta mark or 0x03 == 0x01 meta mark or 0x03 != 0x01 meta mark xor 0x03 == 0x01 meta mark xor 0x03 != 0x01 meta mark set 0xffffffc8 xor 0x16 meta mark set 0x16 and 0x16 meta mark set 0xffffffe9 or 0x16 meta mark set 0xffffffde and 0x16 meta mark set 0x32 or 0xfffff meta mark set 0xfffe xor 0x16
skuid <user id>	UID associated with originating socket	meta skuid {bin, root, daemon} meta skuid root meta skuid != root meta skuid lt 3000 meta skuid gt 3000 meta skuid eq 3000 meta skuid 3001-3005 meta skuid != 2001-2005 meta skuid { 2001-2005 }
skgid <group id>	GID associated with originating socket	meta skgid {bin, root, daemon} meta skgid root meta skgid != root meta skgid lt 3000 meta skgid gt 3000 meta skgid eq 3000 meta skgid 3001-3005 meta skgid != 2001-2005 meta skgid { 2001-2005 }
rtclassid <class>	Routing realm	meta rtclassid cosmos
pkttype <type>	Packet type	meta pkttype broadcast meta pkttype != broadcast meta pkttype { broadcast, unicast, multicast}
cpu <cpu index>	CPU ID	meta cpu 1 meta cpu != 1 meta cpu 1-3 meta cpu != 1-2 meta cpu { 2,3 } meta cpu { 2-3, 5-7 }
iifgroup <input group>	Input interface group	meta iifgroup 0 meta iifgroup != 0 meta iifgroup default meta iifgroup != default meta iifgroup {default} meta iifgroup { 11,33 } meta iifgroup {11-33}
oifgroup <group>	Output interface group	meta oifgroup 0 meta oifgroup != 0 meta oifgroup default meta oifgroup != default meta oifgroup {default} meta oifgroup { 11,33 } meta oifgroup {11-33}
cgroup <group>		meta cgroup 1048577 meta cgroup != 1048577 meta cgroup { 1048577, 1048578 } meta cgroup 1048577-1048578 meta cgroup != 1048577-1048578 meta cgroup {1048577-1048578}

Statements

Statement, paket kuralla eşleştiğinde gerçekleştirilen eylemdir. Terminal ve terminal dışı olabilir. Belli bir kuralda, birkaç terminal dışı ifadeyi düşünebiliriz, yalnızca tek bir terminal bildirimi düşünebilirsiniz.

Statement, kural setindeki akış kontrolünü değiştirir ve paketler için politika kararları verir.

accept: Paketi kabul et ve kalıcı kurallar değerlendirmesini durdur.
drop: Paketi düşür ve kalan kuralların değerlendirmesini durdurun.
queue: Paketi kuyruğa al ve kalan kural değerlendirmesini durdurun.
continue: Bir sonraki kuralla kural seti değerlendirmesine devam edin.
return: Geçerli zincirden dönün ve son zincirin bir sonraki kuralı ile devam edin. Base zincirinde accept ile eş değerdir.
jump <chain>: <chain> ile belirtilen zincirin ilk kuralıyla devam edin. İade ifadesinin yayınlanmasının ardından bir sonraki kuralda devam edecektir.
goto <chain>: Jump'a benzer, ancak yeni zincirden sonra değerlendirme, goto deyimini içeren son zincirde devam edecektir.

Log

log statement
level [over] <value> <unit> [burst <value> <unit>]	Log level	log log level emerg log level alert log level crit log level err log level warn log level notice log level info log level debug
group <value> [queue-threshold <value>] [snaplen <value>] [prefix "<prefix>"]		log prefix aaaaa-aaaaaa group 2 snaplen 33 log group 2 queue-threshold 2 log group 2 snaplen 33

log statement

level [over] <value> <unit> [burst <value> <unit>]

Log level

log
log level emerg
log level alert
log level crit
log level err
log level warn
log level notice
log level info
log level debug

group <value> [queue-threshold <value>] [snaplen <value>] [prefix "<prefix>"]

log prefix aaaaa-aaaaaa group 2 snaplen 33
log group 2 queue-threshold 2
log group 2 snaplen 33

Reject

reject statement
with <protocol> type <type>		reject reject with icmp type host-unreachable reject with icmp type net-unreachable reject with icmp type prot-unreachable reject with icmp type port-unreachable reject with icmp type net-prohibited reject with icmp type host-prohibited reject with icmp type admin-prohibited reject with icmpv6 type no-route reject with icmpv6 type admin-prohibited reject with icmpv6 type addr-unreachable reject with icmpv6 type port-unreachable ip protocol tcp reject with tcp reset reject with icmpx type host-unreachable reject with icmpx type no-route reject with icmpx type admin-prohibited reject with icmpx type port-unreachable

reject statement

with <protocol> type <type>

reject
reject with icmp type host-unreachable
reject with icmp type net-unreachable
reject with icmp type prot-unreachable
reject with icmp type port-unreachable
reject with icmp type net-prohibited
reject with icmp type host-prohibited
reject with icmp type admin-prohibited
reject with icmpv6 type no-route
reject with icmpv6 type admin-prohibited
reject with icmpv6 type addr-unreachable
reject with icmpv6 type port-unreachable
ip protocol tcp reject with tcp reset
reject with icmpx type host-unreachable
reject with icmpx type no-route
reject with icmpx type admin-prohibited
reject with icmpx type port-unreachable

Counter

counter statement
packets <packets> bytes <bytes>		counter counter packets 0 bytes 0

Limit

limit statement
rate [over] <value> <unit> [burst <value> <unit>]	Rate limit	limit rate 400/minute limit rate 400/hour limit rate over 40/day limit rate over 400/week limit rate over 1023/second burst 10 packets limit rate 1025 kbytes/second limit rate 1023000 mbytes/second limit rate 1025 bytes/second burst 512 bytes limit rate 1025 kbytes/second burst 1023 kbytes limit rate 1025 mbytes/second burst 1025 kbytes limit rate 1025000 mbytes/second burst 1023 mbytes

limit statement

rate [over] <value> <unit> [burst <value> <unit>]

Rate limit

limit rate 400/minute
limit rate 400/hour
limit rate over 40/day
limit rate over 400/week
limit rate over 1023/second burst 10 packets
limit rate 1025 kbytes/second
limit rate 1023000 mbytes/second
limit rate 1025 bytes/second burst 512 bytes
limit rate 1025 kbytes/second burst 1023 kbytes
limit rate 1025 mbytes/second burst 1025 kbytes
limit rate 1025000 mbytes/second burst 1023 mbytes

Nat

nat statement
dnat <destination address>	Destination address translation	dnat 192.168.3.2 dnat ct mark map { 0x00000014 : 1.2.3.4}
snat <ip source address>	Source address translation	snat 192.168.3.2 snat 2001:838:35f:1::-2001:838:35f:2:::100
masquerade [<type>] [to :<port>]	Masquerade	masquerade masquerade persistent,fully-random,random masquerade to :1024 masquerade to :1024-2048

nat statement

dnat <destination address>

Destination address translation

dnat 192.168.3.2
dnat ct mark map { 0x00000014 : 1.2.3.4}

snat <ip source address>

Source address translation

snat 192.168.3.2
snat 2001:838:35f:1::-2001:838:35f:2:::100

masquerade [<type>] [to :<port>]

Masquerade

masquerade
masquerade persistent,fully-random,random
masquerade to :1024
masquerade to :1024-2048

Queue

queue statement
num <value> <scheduler>		queue queue num 2 queue num 2-3 queue num 4-5 fanout bypass queue num 4-5 fanout queue num 4-5 bypass

Olayları İzleme

nft monitor [new | destroy] [tables | chains | sets | rules | elements] [xml | json]

komutu ile filtreleme olaylarını izleyebilirsiniz.

Basit IP / IPv6 Güvenlik Duvarı Örneği

flush ruleset

table firewall {
  chain incoming {
    type filter hook input priority 0; policy drop;

    # established/related connections
    ct state established,related accept

    # loopback interface
    iifname lo accept

    # icmp
    icmp type echo-request accept

    # open tcp ports: sshd (22), httpd (80)
    tcp dport {ssh, http} accept
  }
}

table ip6 firewall {
  chain incoming {
    type filter hook input priority 0; policy drop;

    # established/related connections
    ct state established,related accept

    # invalid connections
    ct state invalid drop

    # loopback interface
    iifname lo accept

    # icmp
    # routers may also want: mld-listener-query, nd-router-solicit
    icmpv6 type {echo-request,nd-neighbor-solicit} accept

    # open tcp ports: sshd (22), httpd (80)
    tcp dport {ssh, http} accept
  }
}

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