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Linux防火墙之iptables入门
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一、防火墙的概念
什么是防火墙？防火墙是一台或一组设备，用以在网络间实施访问控制策略；事实上一个防火墙能够包含OSI模型中的很多层，并且可能会涉及进行数据包过滤的设备，它可以实施数据包检查和过滤，在更高的层次中对某应用程序实现某一策略，或做更多类似的事情。防火墙的功能主要是隔离功能，工作在网络或主机边缘，对进出网络或主机的数据包基于一定的规则检查，并在匹配某规则定义的行为进行处理的一组功能组件，基本上的实现都是默认情况下关闭所有的访问，只开放允许访问的策略；防火墙分主机防火墙、网络防火墙、硬件防火墙、软件防火墙、网络层防火墙、应用层防火墙等；主机防火墙指定的是针对服务当前主机做的访问策略的防火墙；网络防火墙指服务范围为防火墙一侧的局域网；硬件防火墙指在专用硬件级别实现部分功能的防火墙，另一部分功能基于软件实现；软件防火墙指运行于通用硬件平台之上的防火墙应用软件；网络层防火墙指OSI模型下四层的防火墙，主要针对OSI模型下四层的网络报文的访问策略控制；应用层防火墙/代理服务器指OSI模型中的应用层的防火墙，它主要在应用层进行操作，针对应用层的程序数据报文进行访问策略控制；
二、网络型防火墙和应用层防火墙的优缺点
网络层防火墙主要是包过滤，网络层对数据包进行选择，选择的依据是系统内设置的过滤逻辑，被称为访问控制列表（ACL），通过检查数据流中每个数据的源地址，目标地址，所用端口和协议状态等因素，或他们的组合来取定是否允许该数据包通过；优点对用户来说透明，处理速度快且易于维护；缺点无法检查应用层数据，如病毒等；
应用层防火墙我们又称代理服务型防火墙，它将所有跨越防火墙的网络通信链路分为两段；内外网用户的访问都是通过代理服务器上的“链路”来实现，这种防火墙优点是在应用层对数据进行检查，比较安全，缺点是增加防火墙的负载。
现实生产环境中所使用的防火墙一般都是二者结合体，即现检查网络数据，通过之后在送到应用层去检查。
三、iptables简介
先来说说内核组件netfilter，它是Linux2.4以后的内核版本引入的一个子系统，它作为一个通用的、抽象的框架，提供一整套的hook(勾子)函数的管理机制，使得诸如数据包过滤、网络地址转换和基于协议类型的连接追踪成为了可能；它在内核中选取了五个位置放置了五个hook(勾子)函数分别是INPUT、OUTPUT、FORWARD、PREROUTING、POSTROUTING，而这五个勾子函数向用户开放，用户可以通过一个命令工具（iptables）向其写入规则；从上面的介绍不难理解，iptables只是管理netfilter上规则的一个用户空间的工具，真正实现防火墙的功能是netfilter，我们知道内核空间的功能，用户是没有办法直接使用，必须通过用户空间的软件去调用才可以使用。这也不难说明了iptables它是一个工具，而不是一个服务。
四、iptables的组成以及数据包的传输过程
iptables由五个表和五个链以及一些规则组成，五个表分别是filter、nat、mangle、raw、security，这五张表每张表都有不同的作用，filter表，主要是过滤报文策略的定义，根据预定义的规则过滤符合条件的数据包才允许或拒绝通行。nat表是地址转换规则表，它上面主要定义一些地址转换规则。mangle表是修改数据标记位规则表，raw是关闭NAT表上启用的连接跟踪机制，加快封包穿越防火墙速度，security用于强制访问控制（MAC）网络规则，有Linux安全模块（如selinux）实现；他们的优先级由高到低的顺序为security--->raw---->mangle---->nat---->filter
五个内置的链（chain）就是我们上面说的五个勾子函数INPUT、OUTPUT、FORWARD、PREROUTING、POSTROUTING，netfilter表和链对应关系如下图
上图没有画出securiyt表所工作的链，它和filter表一样，都工作在INPUT、FORWARD、OUTPUT链上。上图主要是说明了五个表的工作位置，了解了表和链的对应关系，我们在来看看数据包过滤匹配流程
如上图所示，从网络A访问网络B，首先数据要先到达我们防火墙的网卡上，内核根据数据包目的IP判断是否需要转送出去，在路由之前数据报文要通过raw、mangel、nat这三个表中的规则，如果通过了这三张表中的规则后，数据才能决定到底是发往本机还是通过本机转发出去，如果是发往本机的，则数据会经过PREROUTING链，来到INPUT链，在进入用户空间访问用户空间的应用进程时，数据首先要通过，INPUT链上的所有规则，才可以访问本机用户空间的进程，用户空间进程接受到远端用户请求的数据报文后，响应报文会来到OUTPUT链上，这个链主要检查由本机发出的数据包，只有数据包满足出站规则后，它才能通过OUTPUT，当数据报文通过OUTPUT链后，数据报文会经过路由，来到POSTROUTING链，然后POSTROUTING链上的规则会对出站报文进行匹配，满足匹配策略POSTROUTING链放行或拒绝；如果数据包不是发往本机，则数据报文会经过PREROUTING链来到FORWARD链上，在FORWARD链上也有规则，数据符合FORWARD链上定义的规则，则通过或不通过（这个要看链上的处理动作怎么定义的，我们这里假设是匹配通过，不匹配这不通过来说明数据报文过滤匹配流程），如果数据通过了FORWARD链上的所有规则，这时数据会再次经过路由来到POSTROUTING链，同理它需要通过POSTROUTING上的所有规则后才能把到达下一个网络，从而实现数据包的转发；
通过上图，不难发现数据报文的流向有三种，第一种是到本机来到，第二种是从本机出去的，第三种是经由本机转发的；流入本机的报文首先要通过PREROUTING链然后通过后来到INPUT链，通过后最后到达用户空间进程；流出本机的数据报文走向是用户空间进程---->OUTPUT---->POSTROUTING；经本机转发出去的报文走向：PREROUTING --> FORWARD --> POSTROUTING
了解了数据报文的走向后，我们在来说说路由功能和发生的时间点，报文进入本机后，内核通过数据报的目标ip来判断此数据包是发往本机还是转发，如果是发往本机，则数据报文会送到INPUT链，如果不是发往本机的数据报文会送到FORWARD链，这时报文进入本机前端路由；在报文离开本机之前，内核会根据目标地址IP来判断数据报文由那个接口送往下一跳（下一个网络）
当一个数据包进入网卡时，数据包首先进入PREROUTING链，内核根据数据包目的IP判断是否需要转送出去；如果数据包就是进入本机的，数据包就会到达INPUT链。数据包到达INPUT链后，任何进程都会收到它。本机上运行的程序可以发送数据包，这些数据包经过OUTPUT链，然后到达POSTROUTING链输出；如果数据包是要转发出去的，且内核允许转发，数据包就会向右移动，经过FORWARD链，然后到达POSTROUTING链输出；
五、ipatbles规则
规则（rule）是由匹配条件和匹配动作组成，根据规则的匹配条件尝试匹配报文，对匹配成功的报文根据规则定义的处理动作作出处理。匹配条件有基本匹配条件和扩展匹配条件，基本匹配条件就是内建匹配条件，原生就有的，扩展匹配条件是由扩展模块定义，需要安装特定的模块才可以实现特定的扩展匹配；处理动作分基本处理动作，就是内建，原生支持的动作，扩展处理动作，由扩展模块定义，还有就是用户自定义处理（就是把匹配到达报文叫由自定义链来处理，这也是自定义链被主链调用的方式），iptables的链分内置链，和自定义链，内置的链就是对应五个勾子函数；自定义链式用于内置链的扩展和补充，可实现更灵活的规则管理机制，它只有被内置链调用才能生效；
iptables规则添加需要考量以下几点
1、要实现那种功能，判断规则该添加到那张表上的那个位置（iptables匹配规则的顺序是从上至下依次匹配，匹配到了就安装匹配到的处理动作做出处理，没有匹配到就按默认动作处理，所以添加规则需要考虑添加到那个位置）
2、报文流经的路径必须清楚，需要判断把规则添加到哪个链上
3、报文的流向，判断源和目标
4、匹配规则，根据业务需求，怎么去匹配规则
六、iptables命令使用和选项说明
[root@test ~]# iptables -h
iptables v1.4.21 Usage: iptables -[ACD] chain rule-specification [options]
iptables -I chain [rulenum] rule-specification [options]
iptables -R chain rulenum rule-specification [options]
iptables -D chain rulenum [options]
iptables -[LS] [chain [rulenum]] [options]
iptables -[FZ] [chain] [options]
iptables -[NX] chain
iptables -E old-chain-name new-chain-name
iptables -P chain target [options]
iptables -h (print this help information) Commands:
Either long or short options are allowed.
--append -A chain Append to chain
--check -C chain Check for the existence of a rule
--delete -D chain Delete matching rule from chain
--delete -D chain rulenum
Delete rule rulenum (1 = first) from chain
--insert -I chain [rulenum]
Insert in chain as rulenum (default 1=first)
--replace -R chain rulenum
Replace rule rulenum (1 = first) in chain
--list -L [chain [rulenum]]
List the rules in a chain or all chains
--list-rules -S [chain [rulenum]]
Print the rules in a chain or all chains
--flush -F [chain] Delete all rules in chain or all chains
--zero -Z [chain [rulenum]]
Zero counters in chain or all chains
--new -N chain Create a new user-defined chain
--delete-chain
-X [chain] Delete a user-defined chain
--policy -P chain target
Change policy on chain to target
--rename-chain
-E old-chain new-chain
Change chain name, (moving any references)
Options:
--ipv4 -4 Nothing (line is ignored by ip6tables-restore)
--ipv6 -6 Error (line is ignored by iptables-restore)
[!] --protocol -p proto protocol: by number or name, eg. `tcp'
[!] --source -s address[/mask][...]
source specification
[!] --destination -d address[/mask][...]
destination specification
[!] --in-interface -i input name[+]
network interface name ([+] for wildcard)
--jump -j target
target for rule (may load target extension)
--goto -g chain
jump to chain with no return
--match -m match
extended match (may load extension)
--numeric -n numeric output of addresses and ports
[!] --out-interface -o output name[+]
network interface name ([+] for wildcard)
--table -t table table to manipulate (default: `filter')
--verbose -v verbose mode
--wait -w [seconds] maximum wait to acquire xtables lock before give up
--wait-interval -W [usecs] wait time to try to acquire xtables lock
default is 1 second
--line-numbers print line numbers when listing
--exact -x expand numbers (display exact values)
[!] --fragment -f match second or further fragments only
--modprobe=<command> try to insert modules using this command
--set-counters PKTS BYTES set the counter during insert/append
[!] --version -V print package version.
[root@test ~]#
提示：除了以上用-h来了解iptables的简要用法和说明外，我们还可以通过man 8 iptables来了解每个选项的详细说明
-t选项表示指定表名，默认是filter表，-A表示追加规则到最后，-s表示指定源ip地址 -j 表示处理的动作；iptables命令大概可以分二段段，第一段是指明规则位置，第二段是规则本身，规则又需要指明匹配条件和处理动作；上图命令表示在INPUT链上的filter表上追加一条规则到最后，规则内容为源地址为192.168.0.1的报文将丢弃；注意-A后面需要跟链名，链名必须得大写。
总结命令使用格式：iptables [-t tablesname] COMMAND chain [-m matchname [per-match-options]] -j targetname [per-target-options]
tablesname: raw,mangle,nat,[filter]默认不指定就是filter;
COMMAND子命令，指明对规则的增删查改
1、链管理
-N：new，自定义一条新的规则链
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 7 packets, 488 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 5 packets, 524 bytes)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -N my_chain
[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 ~]#
-X：delete,删除自定义的空的规则链（删除一条自定义链的前提是，自定义连未被主链引用，也就是引用计数为0，其次是自定义链必须是空连，就是没有任何规则的链）
[root@test ~]# iptables -A my_chain -s 192.168.0.0/24 -j ACCEPT
[root@test ~]# iptables -A INPUT -s 192.168.0.0/24 -j my_chain
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
24 1688 my_chain all -- * * 192.168.0.0/24 0.0.0.0/0 Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 16 packets, 1488 bytes)
pkts bytes target prot opt in out source destination Chain my_chain (1 references)
pkts bytes target prot opt in out source destination
24 1688 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
[root@test ~]# iptables -X my_chain
iptables: Too many links.
[root@test ~]# iptables -F INPUT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 25 packets, 1780 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 16 packets, 1552 bytes)
pkts bytes target prot opt in out source destination Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
94 6516 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
[root@test ~]# iptables -X my_chain
iptables: Directory not empty.
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -X my_chain
[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
[root@test ~]#
-P：policy，设置默认策略；对filter表中的链而言，其默认策略有：ACCEPT接受，允许。DROP：丢弃
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 29890 packets, 10M 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 31689 packets, 26M bytes)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -P FORWARD ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 5 packets, 356 bytes)
pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 4 packets, 416 bytes)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -nvL
-E：重命名自定义连；
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
104 7344 you_chain all -- * * 192.168.0.0/24 0.0.0.0/0 Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 37 packets, 4120 bytes)
pkts bytes target prot opt in out source destination Chain you_chain (1 references)
pkts bytes target prot opt in out source destination
104 7344 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
[root@test ~]# iptables -E you_chain my_chain
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
178 12540 my_chain all -- * * 192.168.0.0/24 0.0.0.0/0 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 Chain my_chain (1 references)
pkts bytes target prot opt in out source destination
178 12540 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
[root@test ~]#
提示：重命名自定义链，引用计数不为零是可以被重命名的
2、规则管理
-A：append ，追加规则到指定表达最后
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2208 340K my_chain all -- * * 192.168.0.0/24 0.0.0.0/0 Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 1382 packets, 253K bytes)
pkts bytes target prot opt in out source destination Chain my_chain (1 references)
pkts bytes target prot opt in out source destination
2208 340K ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2360 351K my_chain all -- * * 192.168.0.0/24 0.0.0.0/0 Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 10 packets, 1048 bytes)
pkts bytes target prot opt in out source destination Chain my_chain (1 references)
pkts bytes target prot opt in out source destination
2360 351K ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
0 0 ACCEPT all -- * * 0.0.0.0/0 192.168.0.99
[root@test ~]#
-I：insert, 插入，要指明位置，省略时表示第一条；
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 195 packets, 13312 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 121 packets, 12112 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 41319 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 20 packets, 1372 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:41319
[root@test ~]# iptables -I my_chain -d 192.168.0.99 -p tcp --dport 80 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 124 packets, 10836 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 114 packets, 10648 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:80
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
[root@test ~]# iptables -I my_chain 2 -d 192.168.0.99 -p tcp --dport 8080 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 9 packets, 620 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 6 packets, 1176 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:80
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:8080
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
[root@test ~]#
-D：delete，删除；删除规则需啊哟指明规则序号，或者明规则本身
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 18 packets, 1136 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 17 packets, 3072 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:80
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:8080
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
[root@test ~]# iptables -D my_chain 1
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 6 packets, 396 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 4 packets, 416 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:8080
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
[root@test ~]# iptables -D my_chain -d 192.168.0.99 -p tcp --dport 8080 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 6 packets, 396 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 4 packets, 528 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:41319
[root@test ~]#
-R：replace，替换指定链上的指定规则；需指明替换第几条规则
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 6 packets, 396 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 4 packets, 528 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:41319
[root@test ~]# iptables -R my_chain 1 -d 192.168.0.100 -p tcp --dport 22 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 6 packets, 396 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 4 packets, 528 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 DROP tcp -- * * 0.0.0.0/0 192.168.0.100 tcp dpt:22
[root@test ~]#
-F：flush，清空指定的规则链；若为指定链 ，则表示清空filter表所在的所有链
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 38 packets, 2560 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 29 packets, 3648 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 DROP tcp -- * * 0.0.0.0/0 192.168.0.100 tcp dpt:22
[root@test ~]# iptables -F
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 16 packets, 1108 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 11 packets, 1028 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 INPUT -d 192.168.0.99 -p tcp --dport 41319 -j ACCEPT
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp --dport 80 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
139 9668 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319 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 DROP tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:80
[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
200 13824 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319 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 ~]#
-Z：zero，置零指定链上的计数器，若为指定则表示，清空filter表所在的所有链上的规则计数器；iptables的每条规则都有两个计数器：(1) 匹配到的报文的个数；(2) 匹配到的所有报文的大小之和；
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
783 59868 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
50 4212 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 27 packets, 3364 bytes)
pkts bytes target prot opt in out source destination
8 672 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 -Z OUTPUT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
822 62468 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
60 5052 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 4 packets, 416 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 -Z
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
31 2124 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 19 packets, 1764 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 ~]#
2、查看指定链上的规则
-L：list, 列出指定链上的所有规则；-n：numberic，以数字格式显示地址和端口；-v：verbose，详细信息，支持-vv -vvv来指定详细程度
[root@test ~]# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- anywhere test tcp dpt:41319
ACCEPT icmp -- anywhere test icmp echo-request Chain FORWARD (policy DROP)
target prot opt source destination Chain OUTPUT (policy ACCEPT)
target prot opt source destination
ACCEPT icmp -- test anywhere icmp echo-reply Chain my_chain (0 references)
target prot opt source destination
[root@test ~]# iptables -Ln
iptables: No chain/target/match by that name.
[root@test ~]# iptables -nL
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- 0.0.0.0/0 192.168.0.99 tcp dpt:41319
ACCEPT icmp -- 0.0.0.0/0 192.168.0.99 icmptype 8 Chain FORWARD (policy DROP)
target prot opt source destination Chain OUTPUT (policy ACCEPT)
target prot opt source destination
ACCEPT icmp -- 192.168.0.99 0.0.0.0/0 icmptype 0 Chain my_chain (0 references)
target prot opt source destination
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 4 packets, 284 bytes)
pkts bytes target prot opt in out source destination
205 14232 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
73 6132 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 160 packets, 18172 bytes)
pkts bytes target prot opt in out source destination
73 6132 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 -nL -vv
Chain INPUT (policy ACCEPT 4 packets, 284 bytes)
pkts bytes target prot opt in out source destination
244 16780 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
93 7812 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 185 packets, 21408 bytes)
pkts bytes target prot opt in out source destination
93 7812 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
libiptc vlibxtables.so.10. 1544 bytes.
Table `filter'
Hooks: pre/in/fwd/out/post = ffffffff/0/220/2b8/ffffffff
Underflows: pre/in/fwd/out/post = ffffffff/188/220/378/ffffffff
Entry 0 (0):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 192.168.0.99/255.255.255.255
Interface: `'/................to `'/................
Protocol: 6
Flags: 00
Invflags: 00
Counters: 244 packets, 16780 bytes
Cache: 00000000
Match name: `tcp'
Target name: `' [40]
verdict=NF_ACCEPT Entry 1 (200):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 192.168.0.99/255.255.255.255
Interface: `'/................to `'/................
Protocol: 1
Flags: 00
Invflags: 00
Counters: 93 packets, 7812 bytes
Cache: 00000000
Match name: `icmp'
Target name: `' [40]
verdict=NF_ACCEPT Entry 2 (392):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 4 packets, 284 bytes
Cache: 00000000
Target name: `' [40]
verdict=NF_ACCEPT Entry 3 (544):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 0 packets, 0 bytes
Cache: 00000000
Target name: `' [40]
verdict=NF_DROP Entry 4 (696):
SRC IP: 192.168.0.99/255.255.255.255
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 1
Flags: 00
Invflags: 00
Counters: 93 packets, 7812 bytes
Cache: 00000000
Match name: `icmp'
Target name: `' [40]
verdict=NF_ACCEPT Entry 5 (888):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 185 packets, 21408 bytes
Cache: 00000000
Target name: `' [40]
verdict=NF_ACCEPT Entry 6 (1040):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 0 packets, 0 bytes
Cache: 00000000
Target name: `ERROR' [64]
error=`my_chain' Entry 7 (1216):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 0 packets, 0 bytes
Cache: 00000000
Target name: `' [40]
verdict=RETURN Entry 8 (1368):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 0 packets, 0 bytes
Cache: 00000000
Target name: `ERROR' [64]
error=`ERROR' [root@test ~]# iptables -nL -vvv
Chain INPUT (policy ACCEPT 4 packets, 284 bytes)
pkts bytes target prot opt in out source destination
288 18748 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
97 8148 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 264 packets, 32648 bytes)
pkts bytes target prot opt in out source destination
97 8148 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
libiptc vlibxtables.so.10. 1544 bytes.
Table `filter'
Hooks: pre/in/fwd/out/post = ffffffff/0/220/2b8/ffffffff
Underflows: pre/in/fwd/out/post = ffffffff/188/220/378/ffffffff
Entry 0 (0):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 192.168.0.99/255.255.255.255
Interface: `'/................to `'/................
Protocol: 6
Flags: 00
Invflags: 00
Counters: 288 packets, 18748 bytes
Cache: 00000000
Match name: `tcp'
Target name: `' [40]
verdict=NF_ACCEPT Entry 1 (200):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 192.168.0.99/255.255.255.255
Interface: `'/................to `'/................
Protocol: 1
Flags: 00
Invflags: 00
Counters: 97 packets, 8148 bytes
Cache: 00000000
Match name: `icmp'
Target name: `' [40]
verdict=NF_ACCEPT Entry 2 (392):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 4 packets, 284 bytes
Cache: 00000000
Target name: `' [40]
verdict=NF_ACCEPT Entry 3 (544):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 0 packets, 0 bytes
Cache: 00000000
Target name: `' [40]
verdict=NF_DROP Entry 4 (696):
SRC IP: 192.168.0.99/255.255.255.255
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 1
Flags: 00
Invflags: 00
Counters: 97 packets, 8148 bytes
Cache: 00000000
Match name: `icmp'
Target name: `' [40]
verdict=NF_ACCEPT Entry 5 (888):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 264 packets, 32648 bytes
Cache: 00000000
Target name: `' [40]
verdict=NF_ACCEPT Entry 6 (1040):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 0 packets, 0 bytes
Cache: 00000000
Target name: `ERROR' [64]
error=`my_chain' Entry 7 (1216):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 0 packets, 0 bytes
Cache: 00000000
Target name: `' [40]
verdict=RETURN Entry 8 (1368):
SRC IP: 0.0.0.0/0.0.0.0
DST IP: 0.0.0.0/0.0.0.0
Interface: `'/................to `'/................
Protocol: 0
Flags: 00
Invflags: 00
Counters: 0 packets, 0 bytes
Cache: 00000000
Target name: `ERROR' [64]
error=`ERROR' [root@test ~]#
提示：使用查看子命令-L如果有其他修饰子命令的选项和-L合并时，需要把 其他修饰该命令的选项需要放在-L 前面，否则会把其选项识别成链名
-x：exactly，显示计数器结果的精确值,而非单位转换后的易读值
--line-numbers：显示规则的序号；可缩写为--line-num
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 7 packets, 502 bytes)
pkts bytes target prot opt in out source destination
7196 322K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
459 38556 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 13994 packets, 13M bytes)
pkts bytes target prot opt in out source destination
459 38556 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 -nvL --line-numbers
Chain INPUT (policy ACCEPT 7 packets, 502 bytes)
num pkts bytes target prot opt in out source destination
1 7227 324K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
2 459 38556 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8 Chain FORWARD (policy DROP 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 14018 packets, 13M bytes)
num pkts bytes target prot opt in out source destination
1 459 38556 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0 Chain my_chain (0 references)
num pkts bytes target prot opt in out source destination
[root@test ~]# iptables -nvL --line-num
Chain INPUT (policy ACCEPT 7 packets, 502 bytes)
num pkts bytes target prot opt in out source destination
1 7240 325K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
2 459 38556 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8 Chain FORWARD (policy DROP 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 14031 packets, 13M bytes)
num pkts bytes target prot opt in out source destination
1 459 38556 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0 Chain my_chain (0 references)
num pkts bytes target prot opt in out source destination
[root@test ~]#
-S selected,以iptables-save 命令格式显示链上规则
[root@test ~]# iptables -S
-P INPUT ACCEPT
-P FORWARD DROP
-P OUTPUT ACCEPT
-N my_chain
-A INPUT -d 192.168.0.99/32 -p tcp -m tcp --dport 41319 -j ACCEPT
-A INPUT -d 192.168.0.99/32 -p icmp -m icmp --icmp-type 8 -j ACCEPT
-A OUTPUT -s 192.168.0.99/32 -p icmp -m icmp --icmp-type 0 -j ACCEPT
[root@test ~]#
提示：如果有需要，可以将其输出重定向到一个文件中去，但是导出的内容不能用于规则导入到文件，也就是说导出的文件不能用来重载iptables规则表
4、规则的导出和导入
iptables规则导出到指定文件
[root@test ~]# iptables-save > iptables.txt
[root@test ~]# cat iptables.txt
# Generated by iptables-save v1.4.21 on Thu Feb 6 00:01:22 2020
*security
:INPUT ACCEPT [122:11155]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [100:10857]
COMMIT
# Completed on Thu Feb 6 00:01:22 2020
# Generated by iptables-save v1.4.21 on Thu Feb 6 00:01:22 2020
*mangle
:PREROUTING ACCEPT [122:11155]
:INPUT ACCEPT [122:11155]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [100:10857]
:POSTROUTING ACCEPT [100:10857]
COMMIT
# Completed on Thu Feb 6 00:01:22 2020
# Generated by iptables-save v1.4.21 on Thu Feb 6 00:01:22 2020
*raw
:PREROUTING ACCEPT [122:11155]
:OUTPUT ACCEPT [100:10857]
COMMIT
# Completed on Thu Feb 6 00:01:22 2020
# Generated by iptables-save v1.4.21 on Thu Feb 6 00:01:22 2020
*nat
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [5:280]
:POSTROUTING ACCEPT [5:280]
COMMIT
# Completed on Thu Feb 6 00:01:22 2020
# Generated by iptables-save v1.4.21 on Thu Feb 6 00:01:22 2020
*filter
:INPUT ACCEPT [40:5587]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [100:10857]
:my_chain - [0:0]
-A INPUT -d 192.168.0.99/32 -p tcp -m tcp --dport 41319 -j ACCEPT
-A INPUT -d 192.168.0.99/32 -p icmp -m icmp --icmp-type 8 -j ACCEPT
-A OUTPUT -s 192.168.0.99/32 -p icmp -m icmp --icmp-type 0 -j ACCEPT
COMMIT
# Completed on Thu Feb 6 00:01:22 2020
[root@test ~]#
提示：保存规则使用iptables-save命令，它默认是把链上的所有规则打印到标准输出，如果需要保存到指定文件需要用到输出重定向到指定文件即可
iptables规则的导入
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
54895 2298K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
75 6300 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 117K packets, 130M bytes)
pkts bytes target prot opt in out source destination
75 6300 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 -F
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 27 packets, 1976 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 20 packets, 1816 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-restore < iptables.txt
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
24 1636 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
7 588 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
7 588 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 ~]#
提示：导入规则的文件内容必须是iptables-save 导出的文件，不能用iptables -S 导出的文件还原。
-n, --noflush：不清除原有规则导入
[root@test ~]# iptables -F
[root@test ~]# iptables -A INPUT -d 192.168.0.99 -p tcp --dport 3306 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 48 packets, 3468 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:3306 Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 34 packets, 3028 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-restore -n iptables.txt
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:3306
24 1636 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
4 336 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
4 336 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 ~]#
提示：-n选项是不清空原有非自定义链上的规则，对于自定义链不管是否引用都会被清空
-t, --test：仅分析生成规则集，但不提交
[root@test ~]# iptables -F
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 24 packets, 1708 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 17 packets, 1548 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-restore -t iptables.txt
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 98 packets, 7096 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 72 packets, 7188 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 ~]#
提示：以上导出和导入规则适用centos6 和centos7
centos6除上面的方式可以导入和导出规则，它还可以用service iptables save 或者/etc/init.d/iptables save 使用脚本来保存iptables规则
[root@test-node1 ~]#cat /etc/redhat-release
CentOS release 6.7 (Final)
[root@test-node1 ~]#iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
25 1728 you_chain all -- * * 192.168.0.0/24 0.0.0.0/0 Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 16 packets, 2272 bytes)
pkts bytes target prot opt in out source destination Chain you_chain (1 references)
pkts bytes target prot opt in out source destination
25 1728 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
[root@test-node1 ~]#service iptables save
iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]
[root@test-node1 ~]#cat /etc/sysconfig/iptables
# Generated by iptables-save v1.4.7 on Thu Feb 6 00:49:32 2020
*filter
:INPUT ACCEPT [22:1656]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [82:8776]
:you_chain - [0:0]
-A INPUT -s 192.168.0.0/24 -j you_chain
-A you_chain -s 192.168.0.0/24 -j ACCEPT
COMMIT
# Completed on Thu Feb 6 00:49:32 2020
[root@test-node1 ~]
提示：在centos6上使用脚本的方式去导出iptables规则，它默认覆盖保存在/etc/sysconfig/iptables文件
centos6导入规则
[root@test-node1 ~]#iptables -F
[root@test-node1 ~]#iptables -nvL
Chain INPUT (policy ACCEPT 22 packets, 1556 bytes)
pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 14 packets, 1304 bytes)
pkts bytes target prot opt in out source destination Chain you_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test-node1 ~]#service iptables restart
iptables: Setting chains to policy ACCEPT: filter [ OK ]
iptables: Flushing firewall rules: [ OK ]
iptables: Unloading modules: [ OK ]
iptables: Applying firewall rules: [ OK ]
[root@test-node1 ~]#iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
19 1332 you_chain all -- * * 192.168.0.0/24 0.0.0.0/0 Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 13 packets, 1228 bytes)
pkts bytes target prot opt in out source destination Chain you_chain (1 references)
pkts bytes target prot opt in out source destination
19 1332 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
[root@test-node1 ~]#
提示：导入规则centos6 用restart 来导入，不是restore。
