使用 iptables 将数据包从一个接口转发到另一个接口

Question

我有一个带有 2 个接口 e0 和 m0 的嵌入式系统，其 ips 分别为 10.0.0.20 和 192.168.0.20。传入 e0 的数据包的 ip 为 10.0.0.10，应转发到 m0 接口到 ip 为 10.0.0.30 的外部服务器。此外，返回到 m0 的流量应该返回到 e0。

我尝试使用以下命令转发数据包：

route add -net 10.0.0.0/16 dev m0
iptables -t nat -A PREROUTING -d 10.0.0.30 -j DNAT --to-destination 192.168.0.20
iptables -t nat -A POSTROUTING -s 10.0.0.0/16 -j SNAT --to-source 10.0.0.20

我在 m0 执行了 tcpdump，但没有看到任何内容。

你能告诉我我缺少什么吗？先感谢您。

1: lo: <LOOPBACK> mtu 65536 qdisc noop  
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

2: e0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq qlen 1000
    link/ether 00:a0:c9:00:00:00 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.20/24 brd 10.0.0.255 scope global e0
       valid_lft forever preferred_lft forever
    inet6 fe80::2a0:c9ff:fe00:0/64 scope link
       valid_lft forever preferred_lft forever

3: m0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq qlen 1000
    link/ether 00:aa:bb:cc:dd:44 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.20 brd 192.168.0.255 scope global m0
       valid_lft forever preferred_lft forever
    inet6 fe80::2aa:bbff:fecc:dd44/64 scope link
       valid_lft forever preferred_lft forever

4: bcm: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq qlen 1000
    link/ether 00:a0:c9:00:00:03 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::2a0:c9ff:fe00:3/64 scope link
       valid_lft forever preferred_lft forever
5: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop qlen 1000
    link/ether 80:3f:5d:09:7f:4b brd ff:ff:ff:ff:ff:ff

6: e0.1@e0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
    link/ether 00:a0:c9:00:00:00 brd ff:ff:ff:ff:ff:ff
    inet 127.3.0.254/24 brd 127.3.0.255 scope global e0.1
       valid_lft forever preferred_lft forever
    inet6 fe80::2a0:c9ff:fe00:0/64 scope link
       valid_lft forever preferred_lft forever


[0.1.10] pad# ip rule show
0:      from all lookup local
32766:  from all lookup main
32767:  from all lookup default

[0.1.10] pad# ip ro show
default via 192.168.0.20 dev m0
10.0.0.0/24 dev m0
10.0.0.0/24 dev e0  src 10.0.0.20
127.3.0.0/24 dev e0.1  src 127.3.0.254
192.168.0.0/24 dev m0  src 192.168.0.20

0.1.10] pad# iptables -L -vn
Chain INPUT (policy ACCEPT 1480 packets, 186K 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 914 packets, 158K bytes)
 pkts bytes target     prot opt in     out     source               destination


0.1.10] pad# iptables -t nat -L -vn
Chain PREROUTING (policy ACCEPT 258 packets, 51912 bytes)
 pkts bytes target     prot opt in     out     source               destination
    0     0 DNAT       all  --  *      *       0.0.0.0/0            10.0.0.30        to:192.168.0.20
    0     0 DNAT       all  --  *      *       0.0.0.0/0            10.0.0.30        to:192.168.0.20
    0     0 DNAT       all  --  *      *       0.0.0.0/0            10.0.0.30        to:192.168.0.20

Chain INPUT (policy ACCEPT 258 packets, 51912 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain OUTPUT (policy ACCEPT 13 packets, 876 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain POSTROUTING (policy ACCEPT 13 packets, 876 bytes)
 pkts bytes target     prot opt in     out     source               destination
    0     0 SNAT       all  --  *      *       10.0.0.0/16          0.0.0.0/0       to:10.0.0.20
    0     0 SNAT       all  --  *      *       10.0.0.0/16          0.0.0.0/0       to:10.0.0.20

Answer 1

@Mike：刷新所有规则/表并从基础开始，以确保您可以在网络之间进行 nat。

echo 1 > /proc/sys/net/ipv4/ip_forward
route add -net 10.0.0.0/16 dev m0
iptables -t nat -A POSTROUTING -o m0 -j MASQUERADE

在我看来，无论 IP 寻址如何，这都应该将所有 10.0.xx 流量路由并伪装到 m0。如果成功，请根据您的网络需求在此基础上进行构建。