嘿伙计们，这可能只是我忽略了一些愚蠢的事情，但我在设置用于 VPN 的网络命名空间时遇到了麻烦。奇怪的是，这个脚本/设置本来可以运行，但在过去几周内突然停止了。
我在服务器上有一个以太网接口，该接口具有静态 IP 设置，我想将其用于所有正常流量。然后，我使用网桥作为其主网桥，并通过虚拟以太网将 VPN 连接到同一网桥。由于某种原因，我的 VPN 接口可以成功回复 ARP 请求，但似乎无法 ping 我的网关，因此无法连接到互联网）。我觉得这可能是路由问题，但我似乎无法弄清楚。
网络计划
# Let NetworkManager manage all devices on this system
network:
version: 2
renderer: networkd
ethernets:
enp3s0:
dhcp4: false
addresses:
- 192.168.0.54/24
bridges:
br0:
interfaces:
- enp3s0
routes:
- to: default
via: 192.168.0.1
- to: 192.168.0.0/24
nameservers:
addresses: [1.1.1.1, 8.8.8.8]
设置 VPN 网络命名空间的脚本：
ip link add vpn0 type veth peer name vpn1
ip link set dev vpn0 master br0
ip netns add vpn
ip link set vpn1 netns vpn
ip link set dev vpn0 promisc on
ip link set vpn0 up
ip netns exec vpn ip link set lo up
ip netns exec vpn ip link set vpn1 up
ip netns exec vpn ip address add 192.168.0.53/24 dev vpn1
ip netns exec vpn ip route add default via 192.168.0.1 dev vpn1
VPN 地址/路由
root@sam-server:~# ip address
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
5: vpn1@if6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether 06:9e:19:5a:a4:a5 brd ff:ff:ff:ff:ff:ff link-netnsid 0
inet 192.168.0.53/24 scope global vpn1
valid_lft forever preferred_lft forever
inet6 fe80::49e:19ff:fe5a:a4a5/64 scope link
valid_lft forever preferred_lft forever
root@sam-server:~# ip route
default via 192.168.0.1 dev vpn1
192.168.0.0/24 dev vpn1 proto kernel scope link src 192.168.0.53
正常地址/路线
root@sam-server:~# ip address
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master br0 state UP group default qlen 1000
link/ether 88:d7:f6:78:91:72 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.54/24 brd 192.168.0.255 scope global enp3s0
valid_lft forever preferred_lft forever
3: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether e6:3d:5a:ce:a9:fb brd ff:ff:ff:ff:ff:ff
inet6 fe80::e43d:5aff:fece:a9fb/64 scope link
valid_lft forever preferred_lft forever
4: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:19:80:3c:94 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
valid_lft forever preferred_lft forever
6: vpn0@if5: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UP group default qlen 1000
link/ether 66:2c:f9:35:3d:0e brd ff:ff:ff:ff:ff:ff link-netns vpn
inet6 fe80::642c:f9ff:fe35:3d0e/64 scope link
valid_lft forever preferred_lft forever
root@sam-server:~# ip route
default via 192.168.0.1 dev br0 proto static onlink
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown
192.168.0.0/24 dev br0 proto static scope link
192.168.0.0/24 dev enp3s0 proto kernel scope link src 192.168.0.54
从 VPN 名称空间进行 Ping（Arp似乎解决了，但我无法ping通网关）
root@sam-server:~# ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
^C
--- 192.168.0.1 ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 3066ms
root@sam-server:~# ping 192.168.0.54
PING 192.168.0.54 (192.168.0.54) 56(84) bytes of data.
64 bytes from 192.168.0.54: icmp_seq=1 ttl=64 time=0.037 ms
64 bytes from 192.168.0.54: icmp_seq=2 ttl=64 time=0.052 ms
64 bytes from 192.168.0.54: icmp_seq=3 ttl=64 time=0.052 ms
^C
--- 192.168.0.54 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2031ms
rtt min/avg/max/mdev = 0.037/0.047/0.052/0.007 ms
root@sam-server:~# arp
Address HWtype HWaddress Flags Mask Iface
192.168.0.1 ether b0:95:75:8c:fe:80 C vpn1
192.168.0.54 ether e6:3d:5a:ce:a9:fb C vpn1
root@sam-server:~#
希望这些信息足够，如果需要的话我可以发布更多信息。
答案1
我找到了问题的答案。原来这很简单。基本上，两周前我安装了Docker。我之前不知道这一点，但 Docker 搞乱了iptables。
root@sam-server:~# iptables --list
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy DROP) <----------- PROBLEM IS HERE
target prot opt source destination
DOCKER-USER all -- anywhere anywhere
DOCKER-ISOLATION-STAGE-1 all -- anywhere anywhere
ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED
DOCKER all -- anywhere anywhere
ACCEPT all -- anywhere anywhere
ACCEPT all -- anywhere anywhere
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain DOCKER (1 references)
target prot opt source destination
Chain DOCKER-ISOLATION-STAGE-1 (1 references)
target prot opt source destination
DOCKER-ISOLATION-STAGE-2 all -- anywhere anywhere
RETURN all -- anywhere anywhere
Chain DOCKER-ISOLATION-STAGE-2 (1 references)
target prot opt source destination
DROP all -- anywhere anywhere
RETURN all -- anywhere anywhere
Chain DOCKER-USER (1 references)
target prot opt source destination
RETURN all -- anywhere anywhere
由于 Docker 自动设置FORWARD为DROP我的数据包不会被转发到接口。我认为它ARP正在工作，因为它不受 iptables 的影响。
解决方法只是重置策略以接受：iptables --policy FORWARD ACCCEPT