一、iptables的基本匹配條件
上一篇博文我們說到了iptables的基本工作原理、數據報文在內核的走向和管理鏈、管理規則、以及查看規則、導入和導出規則；回顧請參考https://www.cnblogs.com/qiuhom-1874/p/12237976.html，今天我們再來說說iptables的基本匹配條件。
iptables的基本匹配條件也叫通用匹配條件，是iptables/netfilter原生自帶的，無需加載模塊，通俗的講就是iptables這個命令的原生選項。iptables基本匹配條件有以下幾種
1、[!] -s,--source addresss[/mask][,…]：表示匹配報文段源ip地址或范圍，它可以是一個ip地址，也可以是一個網段地址，網段地址需要寫明子網掩碼，其中子網掩碼支持225.255.0.0的方式，也支持數字表示，比如192.168.0.0/24。同時它也支持取反。
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
461 33551 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 14 packets, 1320 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -s 192.168.1.0/24 -j ACCEPT
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -j ACCEPT
[root@test ~]# iptables -A my_chain -s 192.168.0.0/255.255.255.0 -j ACCEPT
[root@test ~]# iptables -nvL my_chain
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * * 192.168.1.0/24 0.0.0.0/0
0 0 ACCEPT all -- * * 192.168.0.232 192.168.0.99
0 0 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
[root@test ~]# iptables -A my_chain ! -s 192.168.10.0/24 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
946 67475 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 15 packets, 1396 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * * 192.168.1.0/24 0.0.0.0/0
0 0 ACCEPT all -- * * 192.168.0.232 192.168.0.99
0 0 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
0 0 ACCEPT all -- * * !192.168.10.0/24 0.0.0.0/0
[root@test ~]#
2、-d,--destination address[/mask][,…]：表示匹配報文的目標ip地址或范圍，它同-s的用法一樣，支持單台主機或一個網段，網段需寫明子網掩碼，子網掩碼支持數字表示，也支持子網掩碼地址的方式表示。同時它也支持對匹配的條件取反。
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL my_chain
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp --dport 22 -j ACCEPT
[root@test ~]# iptables -A my_chain -d 192.168.0.10 -p tcp --dport 3306 -j DROP
[root@test ~]# iptables -A my_chain -d 192.168.10.0/24 -p tcp --dport 25 -j DROP
[root@test ~]# iptables -A my_chain ! -d 192.168.11.0/255.255.255.0 -p tcp --dport 123 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1698 123K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 17 packets, 1580 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:22
0 0 DROP tcp -- * * 0.0.0.0/0 192.168.0.10 tcp dpt:3306
0 0 DROP tcp -- * * 0.0.0.0/0 192.168.10.0/24 tcp dpt:25
0 0 DROP tcp -- * * 0.0.0.0/0 !192.168.11.0/24 tcp dpt:123
[root@test ~]#
3、[!] -p, --protocol protocol：指定協議，可使用數字如0（all）；protocol: tcp, udp, icmp, icmpv6, udplite,esp, ah, sctp, mh or“all“ 參考：/etc/protocols
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1752 126K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp --dport 80 -j DROP
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp --dport 23 -j DROP
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp --sport 25 -j ACCEPT
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p icmp --icmp-type 0 -j ACCEPT
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p icmp --icmp-type 8 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2487 179K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 47 packets, 4340 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 DROP tcp -- * * 192.168.0.232 192.168.0.99 tcp dpt:80
0 0 DROP tcp -- * * 192.168.0.232 192.168.0.99 tcp dpt:23
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp spt:25
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 0
0 0 ACCEPT icmp -- * * 192.168.0.232 192.168.0.99 icmptype 8
[root@test ~]# iptables -A my_chain ! -p udp -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2586 186K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 DROP tcp -- * * 192.168.0.232 192.168.0.99 tcp dpt:80
0 0 DROP tcp -- * * 192.168.0.232 192.168.0.99 tcp dpt:23
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp spt:25
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 0
0 0 ACCEPT icmp -- * * 192.168.0.232 192.168.0.99 icmptype 8
0 0 ACCEPT !udp -- * * 0.0.0.0/0 0.0.0.0/0
[root@test ~]#
提示：-p指定某一協議時，往往會有該協議的一些隱式擴展的選項，比如我們指定-p tcp 表示指定協議類型為tcp 后面指定的源端口或者目標端口 就是tcp模塊的隱式。通俗講就是我們指定了協議為tcp 可以不用明確的用-m 再指定其模塊，這種機制我們叫隱式擴展。上面的例子用到了隱式擴展到有 tcp 的 --sport --dport ;icmp 協議的--icmp-type;當然-p指定協議的類型也可以用！ 來對它取反，表示匹配除了指定的協議以為的所有協議的報文，如果不用-p 指定協議表示匹配所有協議的報文
4、[!] -i, --in-interface name：報文流入的接口；只能應用於數據報文流入環節，只應用於INPUT、FORWARD、PREROUTING鏈以及自定義鏈。
[root@test ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:30:18:51:af:3c brd ff:ff:ff:ff:ff:ff
inet 192.168.0.99/24 brd 192.168.0.255 scope global noprefixroute enp2s0
valid_lft forever preferred_lft forever
inet 172.16.1.2/16 brd 172.16.255.255 scope global noprefixroute enp2s0:0
valid_lft forever preferred_lft forever
inet6 fe80::230:18ff:fe51:af3c/64 scope link
valid_lft forever preferred_lft forever
3: enp3s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether 00:30:18:51:af:3d brd ff:ff:ff:ff:ff:ff
4: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:63:ab:82:55 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 scope global docker0
valid_lft forever preferred_lft forever
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL my_chain
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -s 192.168.0.0/24 -i enp2s0 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2911 209K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- enp2s0 * 192.168.0.0/24 0.0.0.0/0
[root@test ~]# iptables -A OUTPUT -i enp2s0 -j ACCEPT
iptables v1.4.21: Can't use -i with OUTPUT
Try `iptables -h' or 'iptables --help' for more information.
[root@test ~]#
提示：自定義添加到規則可以被任意主鏈所引用。不存在自定義鏈上的規則不適用主鏈，但主鏈上可以引用它的，只是說主鏈引用后，規則不生效，匹配不到報文。-i 表示指定網絡報文流入的接口，所以這個基本匹配條件，只能用於報文能夠進來的鏈上，比如PREROUTING、INPUT、FORWARD這三個主鏈，以及自定義鏈，通常情況，如果寫到自定義鏈，都是被這三個主鏈所引用，除此之外，被OUTPUT、和POSTROUTING所引用，規則是無效的，不能匹配到報文。
5、[!] -o, --out-interface name：報文流出的接口；只能應用於數據報文流出的環節，只應用於FORWARD、OUTPUT、POSTROUTING鏈以及自定義鏈
[root@test ~]# ip a s
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:30:18:51:af:3c brd ff:ff:ff:ff:ff:ff
inet 192.168.0.99/24 brd 192.168.0.255 scope global noprefixroute enp2s0
valid_lft forever preferred_lft forever
inet 172.16.1.2/16 brd 172.16.255.255 scope global noprefixroute enp2s0:0
valid_lft forever preferred_lft forever
inet6 fe80::230:18ff:fe51:af3c/64 scope link
valid_lft forever preferred_lft forever
3: enp3s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether 00:30:18:51:af:3d brd ff:ff:ff:ff:ff:ff
4: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:63:ab:82:55 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 scope global docker0
valid_lft forever preferred_lft forever
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
66 4512 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -o enp2s0 -j ACCEPT
[root@test ~]# iptables -A INPUT -o enp2s0 -j DROP
iptables v1.4.21: Can't use -o with INPUT
Try `iptables -h' or 'iptables --help' for more information.
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
238 16280 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 61 packets, 5724 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * enp2s0 0.0.0.0/0 0.0.0.0/0
[root@test ~]#
提示：同樣-o表示匹配網絡報文的出口接口，不能用於網絡報文入口的鏈上。在iptables/netfilter框架中，報文的出口只經過FORWARD、OUTPUT和POSTROUTING這三個主鏈，即便我們在自定義鏈上用-o來指定匹配出口的網絡接口，也只有被FORWARD、OUTPUT或者POSTROUTING這三個主鏈所引用才能生效，匹配到報文，用在INPUT或PREROUTING鏈上iptables是不允許的。可以看到FORWARD這個鏈上即可以匹配網絡報文的入口接口和出口接口。
二、tcp/udp/icmp隱式擴展選項說明
iptables的匹配條件分基本匹配條件和擴展匹配條件，擴展匹配條件里有顯示擴展和隱式擴展，從字面上很好理解，顯示就是明確指定嘛 ，隱式就是不明確指定，通常擴展匹配條件是需要加載擴展模塊（/usr/lib64/xtables/*.so）方可生效；隱式擴展我們可以理解為，當我們使用-p 去指定協議時無需再用-m再指定其模塊，就可以使用其擴展模塊中的選項，也就是說不需要我們手動的去加載模塊，-p 所指定的協議，會幫我們加載。（這個僅個人理解哈）
1、tcp協議的隱式擴展選項說明
[!] --source-port, --sport port[:port]：匹配報文源端口,可為端口范圍，當端口連續時可以用：來表示；比如21：25，表示匹配21，22，23，24，25這些連續的端口。
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
878 58520 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp --sport 22 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1324 93312 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 34 packets, 3144 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spt:22
[root@test ~]#
提示：以上添加到規則表示匹配源地址為192.168.0.232 目標地址為192.168.0.99 的tcp報文，並且源端口為22 的報文，如果匹配到這樣的報文，給予放行操作。當然如果是匹配一個連續的端口可以寫成：來表示中間連續的端口，它也支持對源端口取反，表示匹配除了指定的端口以外的所有端口如下所示
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp --sport 23:30 -j ACCEPT
[root@test ~]# iptables -nvL my_chain
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spt:22
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spts:23:30
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp ! --sport 40:50 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1519 107K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spt:22
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spts:23:30
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spts:!40:50
[root@test ~]#
[!] --destination-port,--dport port[:port]：匹配報文目標端口,可為范圍，當端口連續是也可以用：來代替連續中間的端口，同--sport用法一樣
[root@test ~]# iptables -F
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 19 packets, 1332 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp --dport 22 -j ACCEPT
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp --dport 23:25 -j ACCEPT
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp ! --dport 80 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 19 packets, 1332 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:22
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpts:23:25
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:!80
[root@test ~]#
[!] --tcp-flags mask comp表示匹配符合指定標志的數據報文，mask表示需檢查的標志為列表，用逗號分隔，例如SYN,ACK,FIN,RST；comp表示mask列表中必須為1的標志為列表，沒有指定表示必須為0用逗號分隔
[root@test ~]# iptables -F
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 22 packets, 1556 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 15 packets, 1396 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -p tcp --tcp-flags SYN,ACK,FIN,RST SYN -j ACCEPT
[root@test ~]# iptables -A my_chain -p tcp --tcp-flags ALL ALL -j DROP
[root@test ~]# iptables -A my_chain -p tcp --tcp-flags ALL NONE -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 47 packets, 3830 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 39 packets, 3630 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x17/0x02
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x3F
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x00
[root@test ~]#
提示：以上規則表示匹配tcp報文，syn=1 其他標志位為0的報文給予允許放行，匹配所有標志位為1的報文給予丟棄，匹配到所有標志為0的報文給予丟棄。這個擴展選項也支持取反，表示出了指定的標志位的所有報文。
[!] --syn：用於匹配TCP第一次握手報文，它相當於--tcp-flags SYN,ACK,FIN,RST SYN
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 73 packets, 5582 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 61 packets, 6538 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x17/0x02
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x3F
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x00
[root@test ~]# iptables -A INPUT -p tcp --syn -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 11 packets, 804 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x17/0x02
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 8 packets, 864 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x17/0x02
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x3F
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x00
[root@test ~]#
2、udp協議的隱式擴展選項說明
[!] --source-port, --sport port[:port]：匹配報文的源端口或端口范圍，當端口連續可以使用：來代替連續的中間端口
[root@test ~]# iptables -F
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 24 packets, 1636 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 15 packets, 1396 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A OUTPUT -p udp --sport 928 -j ACCEPT
[root@test ~]# iptables -A OUTPUT -p udp --sport 111:123 -j ACCEPT
[root@test ~]# iptables -A OUTPUT -p udp ! --sport 323 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 14 packets, 1028 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 10 packets, 1144 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:928
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spts:111:123
0 0 DROP udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:!323
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]#
[!] --destination-port,--dport port[:port]：匹配報文的目標端口或端口范圍，當端口連續可以使用：來代替連續的中間端口
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 73 packets, 5156 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 54 packets, 6288 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:928
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spts:111:123
1 76 DROP udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:!323
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A INPUT -p udp --dport 928 -j ACCEPT
[root@test ~]# iptables -A INPUT -p udp --dport 111:123 -j ACCEPT
[root@test ~]# iptables -A INPUT -p udp ! --dport 323 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 14 packets, 1028 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:928
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpts:111:123
0 0 DROP udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:!323
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 10 packets, 1160 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:928
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spts:111:123
1 76 DROP udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:!323
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]#
3、icmp協議的隱式擴展選項
[!] --icmp-type {type[/code]|typename}
type/code 的值代表意義
備注：此圖片來源網絡
從上面的表可以看到不同的type，所表達的意思不同，就拿icmp最常用的兩個類型，0和8來說，0表示icmp的應答數據包類型，就好比我們去用ping工具去探測遠端主機是否存活，可以向遠端主機發送icmp協議的8號類型的數據包，對方收到這種類型的數據包，如果正常存活，它會回復一個icmp0號類型的消息，否則它會恢復一個其他類型的數據包（通常情況在對方主機沒有設置任何針對icmp協議報文的控制時）
在iptables里允許我們去ping對方，不允許對方ping我們
[root@test ~]# iptables -F
[root@test ~]# iptables -A OUTPUT -p icmp --icmp-type 8 -j ACCEPT
[root@test ~]# iptables -A INPUT -p icmp --icmp-type 0 -j ACCEPT
[root@test ~]# iptables -A INPUT -p icmp --icmp-type 8 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 25 packets, 1780 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 0
0 0 DROP icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 17 packets, 1580 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]#
提示：把以上三條規則添加到iptabels中就可以實現我們本機發出去的icmp類型為8 的報文可以正常放行，從對方主機返回icmp類型為0的應答報文可以正常放行，同時明確指定發往本機icmp類型為8的請求報文給予丟棄操作
提示：這樣是可以拒絕別人用ping工具來探測我們防火牆主機是否存活，當然這樣設置后，我們自己想探測都不行了，要想設置自己可以探測，我們可以在規則里添加對應的規則。明確放行特定的icmp數據報文
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 30 packets, 2084 bytes)
pkts bytes target prot opt in out source destination
15 1260 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 0
35 2940 DROP icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 19 packets, 1780 bytes)
pkts bytes target prot opt in out source destination
36 3024 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -I INPUT -s 192.168.0.151 -p icmp --icmp-type 8 -j ACCEPT
[root@test ~]# iptables -A OUTPUT -d 192.168.0.151 -p icmp --icmp-type 0 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 8 packets, 528 bytes)
pkts bytes target prot opt in out source destination
12 1008 ACCEPT icmp -- * * 192.168.0.151 0.0.0.0/0 icmptype 8
15 1260 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 0
46 3864 DROP icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 5 packets, 764 bytes)
pkts bytes target prot opt in out source destination
36 3024 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.151 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]#
提示：如果OUTPUT鏈的默認處理動作是DROP 需要配置以上兩條規則，如果默認規則是ACCEPT 那么在INPUT鏈上添加一條允許指定源ip的報文允許就可以了
提示：可以看到添加了指定的源ip主機允許規則后，用對應的主機ping防火牆主機了。
以上就是tcp、udp、icmp這三種協議的常用隱式擴展選項。