我正在运行 ubuntu 18.04，对网络没有太多经验。这个 ubuntu 服务器在我们的机器人上运行，应该充当机器人上其余有线模块的无线到局域网桥接器。我之前一直在客户端桥接模式下使用 dd-wrt 路由器来实现相同的功能，但它们太不一致了。带有以太网端口的现成扩展器有点贵，因此我想尝试一下。我已经使用 netplan 配置了无线接口。
以下是我的服务器上的网络接口，enp2s0 是以太网接口，wlp3s0 是 wifi 接口：
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.10 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 fe80::7c0d:f9ff:feb1:68ba prefixlen 64 scopeid 0x20<link>
ether 7e:0d:f9:b1:68:ba txqueuelen 1000 (Ethernet)
RX packets 3 bytes 138 (138.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 39 bytes 5047 (5.0 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.9.1 netmask 255.255.255.0 broadcast 192.168.9.255
inet6 fe80::42:a6ff:fee9:59a4 prefixlen 64 scopeid 0x20<link>
ether 02:42:a6:e9:59:a4 txqueuelen 0 (Ethernet)
RX packets 1115 bytes 84610 (84.6 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 843 bytes 77266 (77.2 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
eno1: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet 169.254.32.1 netmask 255.255.255.0 broadcast 169.254.32.255
ether fc:aa:14:e3:e4:96 txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 20 memory 0xf7e00000-f7e20000
enp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.64 netmask 255.255.255.0 broadcast 192.168.0.255
ether fc:aa:14:e3:e4:94 txqueuelen 1000 (Ethernet)
RX packets 3 bytes 180 (180.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 216 bytes 14171 (14.1 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 50687 bytes 11888298 (11.8 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 50687 bytes 11888298 (11.8 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
vethea1fda5: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet6 fe80::94b1:bcff:fe80:d58e prefixlen 64 scopeid 0x20<link>
ether 96:b1:bc:80:d5:8e txqueuelen 0 (Ethernet)
RX packets 558 bytes 50143 (50.1 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 486 bytes 45921 (45.9 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
vethf80ef47: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet6 fe80::d419:a5ff:fe1d:fb02 prefixlen 64 scopeid 0x20<link>
ether d6:19:a5:1d:fb:02 txqueuelen 0 (Ethernet)
RX packets 557 bytes 50077 (50.0 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 486 bytes 45965 (45.9 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
wlp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.43 netmask 255.255.255.0 broadcast 192.168.0.255
ether d8:fc:93:c5:df:aa txqueuelen 1000 (Ethernet)
RX packets 6318 bytes 5376431 (5.3 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 4444 bytes 851545 (851.5 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
这是我的 netplan 配置 yaml：
network:
version: 2
renderer: networkd
ethernets:
enp2s0:
dhcp4: no
wifis:
wlp3s0:
dhcp4: no
dhcp6: no
addresses: [192.168.0.44/24]
gateway4: 192.168.0.1
access-points:
"leibnitz":
password: "***********"
bridges:
br0:
dhcp4: no
addresses: [192.168.0.10/24]
interfaces: [enp2s0,wlp3s0]
parameters:
stp: true
forward-delay: 4
配置文件中的桥接部分主要是从这里和那里复制粘贴的，并没有真正理解发生了什么。我的理解是，这会在接口之间创建一个桥梁，因为我已经指定要使用的接口是 enp2s0 和 wlp3s0。它在 2 个接口之间创建了一个桥梁（如果我错了，请原谅）。目前的状态是我可以通过无线接口连接到互联网，但无法 ping 主路由器（192.168.0.1）或同一子网上的任何其他计算机。以下是 brctl show 的输出：
bridge name bridge id STP enabled interfaces
br0 8000.7e0df9b168ba yes enp2s0
docker0 8000.0242a6e959a4 no vethea1fda5
vethf80ef47
当我将一台计算机（配置了静态 IP）连接到 enp2s0 时，我什么也没得到。我甚至无法 ping 连接到 enp2s0 的计算机。任何有关此问题的建议或帮助都将非常有用。
答案1
好的，现在桥接接口已经可以正常工作了。以下是 netplan yaml 文件：
network:
version: 2
renderer: networkd
ethernets:
enp2s0:
dhcp4: no
dhcp6: no
wifis:
wlp3s0:
dhcp4: no
dhcp6: no
access-points:
"leibnitz":
password: ""
bridges:
br0:
dhcp4: no
dhcp6: no
addresses: [192.168.0.10/24]
gateway4: 192.168.0.1
# routes:
# - to: 0.0.0.0/0
# via: 192.168.0.1/24
interfaces: [enp2s0,wlp3s0]
mtu: 1500
nameservers:
addresses: [8.8.8.8]
parameters:
stp: true
forward-delay: 4
但是为了将无线接口 wlp3s0 添加到网桥，我必须做一些额外的配置：
$ iw dev wlp3s0 set 4addr on
$ brctl addif br0 wlp3s0
完成上述步骤后，brctl show br0的输出为：
bridge name bridge id STP enabled interfaces
br0 8000.7e0df9b168ba yes enp2s0
wlp3s0
此后必须使用 ebtables 进行第 2 层 nat，因为只有 wlp3s0 通过 AP（这是我的主路由器）进行身份验证。
ebtables -t nat -A POSTROUTING -o wlp3s0 -n snat --to-src "MAC_OF_WLP3S0" --snat-arp --snat-target ACCEPT
ebtables -t nat -A PREROUTING -p IPv4 -i wlp3s0 --ip-dst 192.168.0.12 -j dnat --to-dst $MAC_OF_CLIENT --dnat-target ACCEPT
ebtables -t nat -A PREROUTING -p ARP -i wlp3s0 --arp-ip-dst 192.168.0.12 -j dnat --to-dst $MAC_OF_CLIENT --dnat-target ACCEPT
192.168.0.12 是客户端计算机的 IP。如果我对上述命令的理解有误，请纠正我。第一个 ebtables 命令确保从桥接接口发出的每个数据包都具有 wlp3s0 的 mac 地址。随后的 2 个命令确保当输入链接收到寻址到 192.168.0.12 的数据包时，其目标 mac 地址将更改为桥接客户端的 mac 地址。
现在桥接接口可以工作了。
$ brctl showmacs br0
port no mac addr is local? ageing timer
2 00:0a:f7:81:da:a3 no 0.00
2 24:0a:64:89:33:8d no 241.86
2 70:bb:e9:13:b6:03 no 32.02
1 d8:50:e6:23:32:6b no 3.34
2 d8:fc:93:c5:df:aa yes 0.00
2 d8:fc:93:c5:df:aa yes 0.00
2 f4:8c:eb:9e:e2:64 no 0.08
1 fc:aa:14:e3:e4:94 yes 0.00
1 fc:aa:14:e3:e4:94 yes 0.00
我可以在连接到网桥以太网接口的客户端计算机上 ping 8.8.8.8。但我无法上网，无法在客户端上浏览互联网。
这是客户端的路由表：
$ route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.0.1 0.0.0.0 UG 20100 0 0 enp4s0
169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 enp4s0
192.168.0.0 0.0.0.0 255.255.255.0 U 100 0 0 enp4s0
这是 ifconfig 的输出：
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.10 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 fe80::7c0d:f9ff:feb1:68ba prefixlen 64 scopeid 0x20<link>
inet6 fd01::7c0d:f9ff:feb1:68ba prefixlen 64 scopeid 0x0<global>
ether 7e:0d:f9:b1:68:ba txqueuelen 1000 (Ethernet)
RX packets 80966 bytes 108616599 (108.6 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 82286 bytes 10385602 (10.3 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.9.1 netmask 255.255.255.0 broadcast 192.168.9.255
inet6 fe80::42:ddff:fe39:8ff0 prefixlen 64 scopeid 0x20<link>
ether 02:42:dd:39:8f:f0 txqueuelen 0 (Ethernet)
RX packets 38417 bytes 2933398 (2.9 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 28883 bytes 2575833 (2.5 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
enp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether fc:aa:14:e3:e4:94 txqueuelen 1000 (Ethernet)
RX packets 3863 bytes 326607 (326.6 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1662 bytes 125423 (125.4 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 1288744 bytes 205878639 (205.8 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1288744 bytes 205878639 (205.8 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
veth8bdf2aa: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet6 fe80::b834:49ff:fe31:12ac prefixlen 64 scopeid 0x20<link>
ether ba:34:49:31:12:ac txqueuelen 0 (Ethernet)
RX packets 19226 bytes 1736798 (1.7 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 14559 bytes 1297280 (1.2 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
veth9e8287f: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet6 fe80::eccb:eaff:fe68:6b60 prefixlen 64 scopeid 0x20<link>
ether ee:cb:ea:68:6b:60 txqueuelen 0 (Ethernet)
RX packets 19191 bytes 1734438 (1.7 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 14593 bytes 1299457 (1.2 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
wlp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether d8:fc:93:c5:df:aa txqueuelen 1000 (Ethernet)
RX packets 129600 bytes 112940617 (112.9 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 89885 bytes 13247558 (13.2 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
以下是客户端电脑的yaml文件：
network:
version: 2
renderer: NetworkManager
ethernets:
enp4s0:
dhcp4: no
dhcp6: no
addresses: [192.168.0.12/24]
gateway: 192.168.0.1
nameservers:
addresses: [8.8.8.8, 8.8.4.4]
我不确定 192.168.0.1 是否是桥接客户端的正确网关，或者它应该是桥接器的 IP。我知道桥接器是一种第 2 层机制，它应该对第 3 层透明，因此连接到桥接器的所有设备都将具有与连接到桥接器外部 AP 的设备相同的网关。
我如何将客户端计算机连接到互联网