我有 Ubuntu 22.04，它通过 OpenVPN 连接到远程网络。我的机器上还运行着一些虚拟机。它们都使用一个虚拟网络相互连接。并非所有虚拟机都支持 OpenVPN，所以我需要使用主机 VPN 连接。该怎么做？
目前，我尝试使用 NAT 虚拟网络，但看起来 VPN 连接完全被忽略，并且流量通过我的网络网关。
我可以尝试使用 iptables 将流量重定向到 VPN TUN 接口，但看起来主机上没有用于 VPN 的路由
$ ip a
...
23: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 500
link/none
inet 192.168.110.7/32 scope global noprefixroute tun0
valid_lft forever preferred_lft forever
inet6 fe80::2a81:35e3:66b3:c04/64 scope link stable-privacy
valid_lft forever preferred_lft forever
$ ip r s
default via 10.0.0.1 dev enp1s0 proto dhcp metric 100
10.0.0.0/24 dev enp1s0 proto kernel scope link src 10.0.0.5 metric 100
169.254.0.0/16 dev virbr1 scope link metric 1000
192.168.100.0/24 dev virbr1 proto kernel scope link src 192.168.100.1
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1
$ sudo iptables-save
# Generated by iptables-save v1.8.7 on Wed Aug 24 22:17:39 2022
*mangle
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
:LIBVIRT_PRT - [0:0]
-A POSTROUTING -j LIBVIRT_PRT
-A LIBVIRT_PRT -o virbr0 -p udp -m udp --dport 68 -j CHECKSUM --checksum-fill
-A LIBVIRT_PRT -o virbr1 -p udp -m udp --dport 68 -j CHECKSUM --checksum-fill
COMMIT
# Completed on Wed Aug 24 22:17:39 2022
# Generated by iptables-save v1.8.7 on Wed Aug 24 22:17:39 2022
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:LIBVIRT_FWI - [0:0]
:LIBVIRT_FWO - [0:0]
:LIBVIRT_FWX - [0:0]
:LIBVIRT_INP - [0:0]
:LIBVIRT_OUT - [0:0]
-A INPUT -j LIBVIRT_INP
-A FORWARD -j LIBVIRT_FWX
-A FORWARD -j LIBVIRT_FWI
-A FORWARD -j LIBVIRT_FWO
-A OUTPUT -j LIBVIRT_OUT
-A LIBVIRT_FWI -d 192.168.122.0/24 -o virbr0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A LIBVIRT_FWI -o virbr0 -j REJECT --reject-with icmp-port-unreachable
-A LIBVIRT_FWI -o virbr1 -j REJECT --reject-with icmp-port-unreachable
-A LIBVIRT_FWO -s 192.168.122.0/24 -i virbr0 -j ACCEPT
-A LIBVIRT_FWO -i virbr0 -j REJECT --reject-with icmp-port-unreachable
-A LIBVIRT_FWO -i virbr1 -j REJECT --reject-with icmp-port-unreachable
-A LIBVIRT_FWX -i virbr0 -o virbr0 -j ACCEPT
-A LIBVIRT_FWX -i virbr1 -o virbr1 -j ACCEPT
-A LIBVIRT_INP -i virbr0 -p udp -m udp --dport 53 -j ACCEPT
-A LIBVIRT_INP -i virbr0 -p tcp -m tcp --dport 53 -j ACCEPT
-A LIBVIRT_INP -i virbr0 -p udp -m udp --dport 67 -j ACCEPT
-A LIBVIRT_INP -i virbr0 -p tcp -m tcp --dport 67 -j ACCEPT
-A LIBVIRT_INP -i virbr1 -p udp -m udp --dport 53 -j ACCEPT
-A LIBVIRT_INP -i virbr1 -p tcp -m tcp --dport 53 -j ACCEPT
-A LIBVIRT_INP -i virbr1 -p udp -m udp --dport 67 -j ACCEPT
-A LIBVIRT_INP -i virbr1 -p tcp -m tcp --dport 67 -j ACCEPT
-A LIBVIRT_OUT -o virbr0 -p udp -m udp --dport 53 -j ACCEPT
-A LIBVIRT_OUT -o virbr0 -p tcp -m tcp --dport 53 -j ACCEPT
-A LIBVIRT_OUT -o virbr0 -p udp -m udp --dport 68 -j ACCEPT
-A LIBVIRT_OUT -o virbr0 -p tcp -m tcp --dport 68 -j ACCEPT
-A LIBVIRT_OUT -o virbr1 -p udp -m udp --dport 53 -j ACCEPT
-A LIBVIRT_OUT -o virbr1 -p tcp -m tcp --dport 53 -j ACCEPT
-A LIBVIRT_OUT -o virbr1 -p udp -m udp --dport 68 -j ACCEPT
-A LIBVIRT_OUT -o virbr1 -p tcp -m tcp --dport 68 -j ACCEPT
COMMIT
# Completed on Wed Aug 24 22:17:39 2022
# Generated by iptables-save v1.8.7 on Wed Aug 24 22:17:39 2022
*nat
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
:LIBVIRT_PRT - [0:0]
-A POSTROUTING -j LIBVIRT_PRT
-A LIBVIRT_PRT -s 192.168.122.0/24 -d 224.0.0.0/24 -j RETURN
-A LIBVIRT_PRT -s 192.168.122.0/24 -d 255.255.255.255/32 -j RETURN
-A LIBVIRT_PRT -s 192.168.122.0/24 ! -d 192.168.122.0/24 -p tcp -j MASQUERADE --to-ports 1024-65535
-A LIBVIRT_PRT -s 192.168.122.0/24 ! -d 192.168.122.0/24 -p udp -j MASQUERADE --to-ports 1024-65535
-A LIBVIRT_PRT -s 192.168.122.0/24 ! -d 192.168.122.0/24 -j MASQUERADE
COMMIT
# Completed on Wed Aug 24 22:17:39 2022