系统： debian squeeze，Linux 服务器 2.6.32-5-amd64 #1 SMP 2014 年 5 月 13 日星期二 16:34:35 UTC x86_64 GNU/Linux，iptables v1.4.8
lsmod | grep iptable
iptable_security 2176 0
iptable_mangle 2817 1
iptable_filter 2258 0
iptable_raw 1867 0
iptable_nat 4283 1
nf_nat 13308 2 ipt_REDIRECT,iptable_nat
nf_conntrack_ipv4 9833 3 iptable_nat,nf_nat
nf_conntrack 46391 3 iptable_nat,nf_nat,nf_conntrack_ipv4
ip_tables 13915 5 iptable_security,iptable_mangle,iptable_filter,iptable_raw,iptable_nat
x_tables 12845 11 ipt_REDIRECT,xt_mark,xt_MARK,xt_dscp,xt_DSCP,xt_tcpudp,xt_string,ipt_LOG,ip6_tables,iptable_nat,ip_tables
这些是我的规则：
iptables -t mangle -A PREROUTING -p tcp -s 192.168.1.2 --dport 80 -m string --algo kmp --string anystring -j LOG --log-prefix anystring1
iptables -t mangle -A PREROUTING -p tcp -s 192.168.1.2 --dport 80 -m string --algo kmp --string anystring -j MARK --set-mark 0x401
iptables -t nat -A PREROUTING -m mark --mark 0x401 -j LOG --log-prefix anystring11
iptables -t nat -A PREROUTING -p tcp -m mark --mark 0x401 -j REDIRECT --to-ports 911
iptables -t mangle -A INPUT -m mark --mark 0x401 -j LOG --log-prefix anystring111
系统日志：
May 22 10:17:01 server kernel: [51224.137665] anystring1IN=eth0 OUT= MAC=00:1b:b9:a1:b0:da:00:17:e0:78:3b:40:08:00 SRC=192.168.1.2 DST=192.168.1.1 LEN=224 TOS=0x00 PREC=0x00 TTL=62 ID=51913 DF PROTO=TCP SPT=54516 DPT=80 WINDOW=457 RES=0x00 ACK PSH URGP=0
May 22 10:17:01 server kernel: [51224.137692] anystring111IN=eth0 OUT= MAC=00:1b:b9:a1:b0:da:00:17:e0:78:3b:40:08:00 SRC=192.168.1.2 DST=192.168.1.1 LEN=224 TOS=0x00 PREC=0x00 TTL=62 ID=51913 DF PROTO=TCP SPT=54516 DPT=80 WINDOW=457 RES=0x00 ACK PSH URGP=0 MARK=0x401
May 22 10:17:01 server kernel: [51224.140909] anystring1IN=eth0 OUT= MAC=00:1b:b9:a1:b0:da:00:17:e0:78:3b:40:08:00 SRC=192.168.1.2 DST=192.168.1.1 LEN=154 TOS=0x00 PREC=0x00 TTL=62 ID=47231 DF PROTO=TCP SPT=54517 DPT=80 WINDOW=457 RES=0x00 ACK PSH URGP=0
May 22 10:17:01 server kernel: [51224.140934] anystring111IN=eth0 OUT= MAC=00:1b:b9:a1:b0:da:00:17:e0:78:3b:40:08:00 SRC=192.168.1.2 DST=192.168.1.1 LEN=154 TOS=0x00 PREC=0x00 TTL=62 ID=47231 DF PROTO=TCP SPT=54517 DPT=80 WINDOW=457 RES=0x00 ACK PSH URGP=0 MARK=0x401
我的桌子：
iptables -t nat -L -v
Chain PREROUTING (policy ACCEPT 9485 packets, 604K bytes)
pkts bytes target prot opt in out source destination
0 0 LOG all -- any any anywhere anywhere mark match 0x401 LOG level warning prefix `anystring11'
0 0 REDIRECT tcp -- any any anywhere anywhere mark match 0x401 redir ports 911
Chain POSTROUTING (policy ACCEPT 12570 packets, 850K bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 8009 packets, 564K bytes)
pkts bytes target prot opt in out source destination
iptables -t mangle -L -v
Chain PREROUTING (policy ACCEPT 339K packets, 101M bytes)
pkts bytes target prot opt in out source destination
6 1134 LOG tcp -- any any 192.168.1.2 anywhere tcp dpt:www STRING match "anystring" ALGO name kmp TO 65535 LOG level warning prefix `anystring1'
6 1134 MARK tcp -- any any 192.168.1.2 anywhere tcp dpt:www STRING match "anystring" ALGO name kmp TO 65535 MARK set 0x401
Chain INPUT (policy ACCEPT 211K packets, 88M bytes)
pkts bytes target prot opt in out source destination
6 1134 LOG all -- any any anywhere anywhere mark match 0x401 LOG level warning prefix `anystring111'
Chain FORWARD (policy ACCEPT 128K packets, 13M bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 192K packets, 139M bytes)
pkts bytes target prot opt in out source destination
Chain POSTROUTING (policy ACCEPT 317K packets, 152M bytes)
pkts bytes target prot opt in out source destination
iptables -t 过滤器 -L -v
Chain INPUT (policy ACCEPT 250K packets, 100M bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 141K packets, 15M bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 229K packets, 157M bytes)
pkts bytes target prot opt in out source destination
iptables -t raw -L -v
Chain PREROUTING (policy ACCEPT 394K packets, 115M bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 234K packets, 158M bytes)
pkts bytes target prot opt in out source destination
iptables -t 安全 -L -v
Chain INPUT (policy ACCEPT 254K packets, 101M bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 141K packets, 15M bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 232K packets, 158M bytes)
pkts bytes target prot opt in out source destination
答案1
这似乎违反直觉，但只有 conntrack 不知道的数据包才会通过 NAT 表。这使得尝试使用字符串匹配进行 NAT 变得困难：当字符串出现在数据包中时，连接已经建立。
通常使用 iptables 字符串匹配是不明智的，您应该在更高层次上做一些事情来实现您的目标。