TL;DR
使用WSL2和Docker Desktop for Windows时，经常遇到网络问题。通常情况下，我可以通过找到WSL2实例的IP地址，并从容器内部引用该IP地址来访问从WSL2实例（在WSL2术语中称为“distribution”）启动的端口。但今天出现了问题。
我想要弄清楚是什么出了问题，而不是一遇到WSL2+DockerDesktop相关问题就重启电脑。可能是企业的Forticlient VPN也有干扰，但这不是我的选择。
Details
我通过以下方式找到IP：
WSL2:» ip -br a
lo UNKNOWN 127.0.0.1/8 ::1/128
bond0 DOWN
dummy0 DOWN
sit0@NONE DOWN
eth0 UP 172.26.183.209/20 fe80::215:5dff:fef9:cc5c/64
WSL2机器的IP地址是172.26.183.209。
现在我在WSL2进程中监听端口8080上的Web服务器可以通过http://172.26.183.209:8080访问，这也经过了来自WSL2的nmap和curl的确认：
WSL2@~» nmap -Pn -p 8080 172.26.183.209
Starting Nmap 7.80 ( https://nmap.org ) at 2020-12-23 16:15 CET
Nmap scan report for ubuntu-wsl2 (172.26.183.209)
Host is up (0.000045s latency).
PORT STATE SERVICE
8080/tcp open http-proxy
Nmap done: 1 IP address (1 host up) scanned in 0.02 seconds
WSL2@~» curl http://172.26.183.209:8080 > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
然而，从容器内部来看：
[root@0467b7ef17e7 /]# nmap -Pn -p 8080 172.26.183.209
Starting Nmap 7.70 ( https://nmap.org ) at 2020-12-23 15:12 UTC
Nmap done: 1 IP address (0 hosts up) scanned in 0.43 seconds
[root@0467b7ef17e7 /]# curl http://172.26.183.209:8080
curl: (7) Failed to connect to 172.26.183.209 port 8080: No route to host
它还可以在 docker-desktop WSL2 容器内部运行：
WSL2@~» wsl.exe -d docker-desktop wget http://172.26.183.209:8080
Connecting to 172.26.183.209:8080 (172.26.183.209:8080)
Connecting to host.docker.internal:8180 (192.168.0.202:8180)
index.html 100% |********************************| 7308 0:00:00 ETA
仅限于容器外部，直到我重启。AAAAAAARRRRRHHHHHHHHHHHHHHHH :-)
一个提示——有一件事对我来说不合理——这是在容器内部吗：
[root@0467b7ef17e7 /]# ping 172.26.183.209
PING 172.26.183.209 (172.26.183.209) 56(84) bytes of data.
From 172.26.0.2 icmp_seq=1 Destination Host Unreachable
From 172.26.0.2 icmp_seq=2 Destination Host Unreachable
From 172.26.0.2 icmp_seq=3 Destination Host Unreachable
^C
--- 172.26.183.209 ping statistics ---
6 packets transmitted, 0 received, +3 errors, 100% packet loss, time 202ms
pipe 4
“172.26.0.2”是什么？嗯……
网络设置：
（由于它在企业网络中，我已经修改了Ethernet 3的IP地址）
WSL2@~» ip -br a
lo UNKNOWN 127.0.0.1/8 ::1/128
bond0 DOWN
dummy0 DOWN
sit0@NONE DOWN
eth0 UP 172.26.183.209/20 fe80::215:5dff:fef9:cc5c/64
WSL2@~» ipconfig.exe
Windows IP Configuration
Ethernet adapter Ethernet 3:
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::405f:b7d2:70b4:b405%19
IPv4 Address. . . . . . . . . . . : 10.14.11.17
Subnet Mask . . . . . . . . . . . : 255.255.255.255
Default Gateway . . . . . . . . . : 10.14.11.18
Ethernet adapter Ethernet 4:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Ethernet adapter Ethernet:
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::7cd1:5641:ac65:7004%15
IPv4 Address. . . . . . . . . . . : 192.168.0.202
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.0.1
Ethernet adapter VirtualBox Host-Only Network:
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::f06d:9785:cff5:2ad0%6
IPv4 Address. . . . . . . . . . . : 192.168.225.1
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :
Wireless LAN adapter Wi-Fi:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Wireless LAN adapter Local Area Connection* 7:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Wireless LAN adapter Local Area Connection* 10:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Ethernet adapter Ethernet 2:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Ethernet adapter Bluetooth Network Connection:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Ethernet adapter vEthernet (WSL):
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::c507:3c2b:62d:7270%39
IPv4 Address. . . . . . . . . . . : 172.26.176.1
Subnet Mask . . . . . . . . . . . : 255.255.240.0
Default Gateway . . . . . . . . . :
WSL2@~» route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 172.26.176.1 0.0.0.0 UG 0 0 0 eth0
172.26.176.0 0.0.0.0 255.255.240.0 U 0 0 0 eth0
