我想将来自端口（例如 4445，来自本地主机）的所有流量重新路由到 LAN 中另一台机器的另一个端口（例如 3305）。我预计这应该可以解决问题：
iptables -A PREROUTING -t nat -i eth0 -p tcp --dport 4445 -j DNAT --to 192.168.72.1:3305
我正在目标机器上监听
nc -k -l 3305
与该 ip:port 的直接连接有效，并且 nc 显示传输的消息。
telnet 192.168.72.1 3305
Trying 192.168.72.1...
Connected to 192.168.72.1.
Escape character is '^]'.
test
^]
但是当我想使用我的 iptables 规则时，连接突然被拒绝：
$>telnet localhost 4445
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection refused
我多次读到必须激活 IP 转发：
$>cat /proc/sys/net/ipv4/ip_forward
1
因此我的 IP 转发应该处于活动状态，并且在从 0 更改为 1 后我确实重新启动了机器。
我还检查了 iptables 是否列出了该规则：
$>iptables -L -t nat
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
DNAT tcp -- anywhere anywhere tcp dpt:4445 to:192.168.72.1:3305
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
--
$>iptables -L -n -v
Chain INPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
4745 586K ufw-before-logging-input all -- * * 0.0.0.0/0 0.0.0.0/0
4745 586K ufw-before-input all -- * * 0.0.0.0/0 0.0.0.0/0
121 8712 ufw-after-input all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ufw-after-logging-input all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ufw-reject-input all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ufw-track-input all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:4445
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 ufw-before-logging-forward all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ufw-before-forward all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ufw-after-forward all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ufw-after-logging-forward all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ufw-reject-forward all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ufw-track-forward all -- * * 0.0.0.0/0 0.0.0.0/0
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
3344 655K ufw-before-logging-output all -- * * 0.0.0.0/0 0.0.0.0/0
3344 655K ufw-before-output all -- * * 0.0.0.0/0 0.0.0.0/0
29 3082 ufw-after-output all -- * * 0.0.0.0/0 0.0.0.0/0
29 3082 ufw-after-logging-output all -- * * 0.0.0.0/0 0.0.0.0/0
29 3082 ufw-reject-output all -- * * 0.0.0.0/0 0.0.0.0/0
29 3082 ufw-track-output all -- * * 0.0.0.0/0 0.0.0.0/0
Chain ufw-after-forward (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-after-input (1 references)
pkts bytes target prot opt in out source destination
0 0 ufw-skip-to-policy-input udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:137
0 0 ufw-skip-to-policy-input udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:138
0 0 ufw-skip-to-policy-input tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:139
0 0 ufw-skip-to-policy-input tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:445
0 0 ufw-skip-to-policy-input udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:67
0 0 ufw-skip-to-policy-input udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:68
121 8712 ufw-skip-to-policy-input all -- * * 0.0.0.0/0 0.0.0.0/0 ADDRTYPE match dst-type BROADCAST
Chain ufw-after-logging-forward (1 references)
pkts bytes target prot opt in out source destination
0 0 LOG all -- * * 0.0.0.0/0 0.0.0.0/0 limit: avg 3/min burst 10 LOG flags 0 level 4 prefix "[UFW BLOCK] "
Chain ufw-after-logging-input (1 references)
pkts bytes target prot opt in out source destination
0 0 LOG all -- * * 0.0.0.0/0 0.0.0.0/0 limit: avg 3/min burst 10 LOG flags 0 level 4 prefix "[UFW BLOCK] "
Chain ufw-after-logging-output (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-after-output (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-before-forward (1 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 3
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 4
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 11
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 12
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
0 0 ufw-user-forward all -- * * 0.0.0.0/0 0.0.0.0/0
Chain ufw-before-input (1 references)
pkts bytes target prot opt in out source destination
146 223K ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
4471 353K ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
0 0 ufw-logging-deny all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate INVALID
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate INVALID
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 3
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 4
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 11
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 12
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:67 dpt:68
128 9132 ufw-not-local all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT udp -- * * 0.0.0.0/0 224.0.0.251 udp dpt:5353
0 0 ACCEPT udp -- * * 0.0.0.0/0 239.255.255.250 udp dpt:1900
128 9132 ufw-user-input all -- * * 0.0.0.0/0 0.0.0.0/0
Chain ufw-before-logging-forward (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-before-logging-input (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-before-logging-output (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-before-output (1 references)
pkts bytes target prot opt in out source destination
146 223K ACCEPT all -- * lo 0.0.0.0/0 0.0.0.0/0
3169 428K ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
29 3082 ufw-user-output all -- * * 0.0.0.0/0 0.0.0.0/0
Chain ufw-logging-allow (0 references)
pkts bytes target prot opt in out source destination
0 0 LOG all -- * * 0.0.0.0/0 0.0.0.0/0 limit: avg 3/min burst 10 LOG flags 0 level 4 prefix "[UFW ALLOW] "
Chain ufw-logging-deny (2 references)
pkts bytes target prot opt in out source destination
0 0 RETURN all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate INVALID limit: avg 3/min burst 10
0 0 LOG all -- * * 0.0.0.0/0 0.0.0.0/0 limit: avg 3/min burst 10 LOG flags 0 level 4 prefix "[UFW BLOCK] "
Chain ufw-not-local (1 references)
pkts bytes target prot opt in out source destination
7 420 RETURN all -- * * 0.0.0.0/0 0.0.0.0/0 ADDRTYPE match dst-type LOCAL
0 0 RETURN all -- * * 0.0.0.0/0 0.0.0.0/0 ADDRTYPE match dst-type MULTICAST
121 8712 RETURN all -- * * 0.0.0.0/0 0.0.0.0/0 ADDRTYPE match dst-type BROADCAST
0 0 ufw-logging-deny all -- * * 0.0.0.0/0 0.0.0.0/0 limit: avg 3/min burst 10
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain ufw-reject-forward (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-reject-input (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-reject-output (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-skip-to-policy-forward (0 references)
pkts bytes target prot opt in out source destination
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain ufw-skip-to-policy-input (7 references)
pkts bytes target prot opt in out source destination
121 8712 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain ufw-skip-to-policy-output (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
Chain ufw-track-forward (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-track-input (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-track-output (1 references)
pkts bytes target prot opt in out source destination
3 180 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 ctstate NEW
26 2902 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 ctstate NEW
Chain ufw-user-forward (1 references)
pkts bytes target prot opt in out source destination
Chain ufw-user-input (1 references)
pkts bytes target prot opt in out source destination
1 60 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:22
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:22
6 360 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:80
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:443
Chain ufw-user-limit (0 references)
pkts bytes target prot opt in out source destination
0 0 LOG all -- * * 0.0.0.0/0 0.0.0.0/0 limit: avg 3/min burst 5 LOG flags 0 level 4 prefix "[UFW LIMIT BLOCK] "
0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
Chain ufw-user-limit-accept (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
Chain ufw-user-logging-forward (0 references)
pkts bytes target prot opt in out source destination
Chain ufw-user-logging-input (0 references)
pkts bytes target prot opt in out source destination
Chain ufw-user-logging-output (0 references)
pkts bytes target prot opt in out source destination
Chain ufw-user-output (1 references)
pkts bytes target prot opt in out source destination
为什么这不能按预期工作/我的错误是什么？
答案1
至少有两个原因导致这种方法行不通：
DNAT您在链中添加了一条带有目标的规则PREROUTING，本地连接时不会触发该规则。相反，您需要将其添加到OUTPUTnat 表中的链中。- 您已指定输入接口
-i eth0，您的测试流量不会来自此接口。它将通过环回接口进行传输lo。
您可以尝试将规则更改为：
iptables -A OUTPUT -t nat -p tcp --dport 4445 -j DNAT --to 192.168.72.1:3305
当然，您可以同时保留这两条规则（针对传入流量和本地生成的流量）。
答案2
连同@Khaled 的建议作为答案...不要忘记触发这个：
sudo iptables -A INPUT -p tcp --dport 4445 -j ACCEPT也是吗？