Sudden loss of WSL2 DNS for several devs

[devbeard]

Environment

Windows build number: Microsoft Windows [Version 10.0.19042.867]
Your Distribution version: Ubuntu, Release:        20.04
Whether the issue is on WSL 2 and/or WSL 1: Linux version 5.4.72-microsoft-standard-WSL2 (oe-user@oe-host) (gcc version 8.2.0 (GCC)) #1 SMP Wed Oct 28 23:40:43 UTC 2020

Steps to reproduce

Sudden loss of DNS across multiple dev's computers in enterprise (but not all). Internet connectivity fine, but DNS resolution suddenly no longer works in WSL2.

$ ping google.com
ping: google.com: Temporary failure in name resolution

$ 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: bond0: <BROADCAST,MULTICAST,MASTER> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether da:f5:e2:00:c9:f9 brd ff:ff:ff:ff:ff:ff
3: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 4e:fd:b7:0d:64:b1 brd ff:ff:ff:ff:ff:ff
4: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:15:5d:24:08:3b brd ff:ff:ff:ff:ff:ff
    inet 172.24.95.217/20 brd 172.24.95.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::215:5dff:fe24:83b/64 scope link
       valid_lft forever preferred_lft forever
5: sit0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN group default qlen 1000
    link/sit 0.0.0.0 brd 0.0.0.0

$ cat /etc/resolv.conf
# This file was automatically generated by WSL. To stop automatic generation of this file, add the following entry to /etc/wsl.conf:
# [network]
# generateResolvConf = false
nameserver 172.24.80.1

$ dig google.com @1.1.1.1

; <<>> DiG 9.16.1-Ubuntu <<>> google.com @1.1.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 53373
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;google.com.                    IN      A

;; ANSWER SECTION:
google.com.             228     IN      A       172.217.21.142

;; Query time: 10 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Fri Mar 26 09:41:09 CET 2021
;; MSG SIZE  rcvd: 55```

On Windows host

❯ Get-NetAdapter

Name                      InterfaceDescription                    ifIndex Status       MacAddress             LinkSpeed
----                      --------------------                    ------- ------       ----------             ---------
Bluetooth Network Connec… Bluetooth Device (Personal Area Networ…      18 Disconnected 04-33-C2-E5-2F-3A         3 Mbps
Ethernet 2                Cisco AnyConnect Secure Mobility Clien…      16 Disabled     00-05-9A-3C-7A-00        10 Mbps
Wi-Fi                     Intel(R) Wireless-AC 9560 160MHz             11 Up           04-33-C2-E5-2F-36       780 Mbps
vEthernet (WSL)           Hyper-V Virtual Ethernet Adapter             44 Up           00-15-5D-3F-86-F4        10 Gbps
Ethernet                  Intel(R) Ethernet Connection (6) I219-…       3 Disconnected F8-75-A4-F2-E4-6F          0 bps

❯ ipconfig /all
[...]
Ethernet adapter vEthernet (WSL):

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Hyper-V Virtual Ethernet Adapter
   Physical Address. . . . . . . . . : 00-15-5D-3F-86-F4
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
   Link-local IPv6 Address . . . . . : fe80::7517:82fd:88a8:9cca%44(Preferred)
   IPv4 Address. . . . . . . . . . . : 172.24.80.1(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.240.0
   Default Gateway . . . . . . . . . :
   DHCPv6 IAID . . . . . . . . . . . : 738202973
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-26-8E-6C-8F-F8-75-A4-F2-E4-6F
   DNS Servers . . . . . . . . . . . : fec0:0:0:ffff::1%1
                                       fec0:0:0:ffff::2%1
                                       fec0:0:0:ffff::3%1
   NetBIOS over Tcpip. . . . . . . . : Enabled
[...]

Expected behavior

Since resolv.conf IP == IPv4 of host, DNS queries should work through host (port 53).

Actual behavior

DNS queries fail.

Temporary failure in name resolution

[K2ouMais]

Are you using VPN?

[devbeard]

No, without a VPN connection. I have since removed everything related to WSL, and reinstalled/reenabled, but with no effect. Still no automatic DNS. I know that I can set the DNS manually, but this used to work flawlessly without - and I am actually more interested in finding out why it does not work than finding a workaround.

[deviantdev]

Happened to me today, twice.
And Hyper-V adapter network has been changed: 172.016.0.0/12 to 192.168.0.0/24

[meister245]

@devbeard Can you ping IP addresses from WSL2?

[devbeard]

Yes, pinging ips works fine.

[meister245]

On my work PC I have the same problem. In the end I found it is some security software called Symantec Endpoint Protection installed by the company, that is actively blocking all IP traffic on WSL2.

https://docs.microsoft.com/en-us/windows/wsl/troubleshooting

See "No internet access in WSL2", it lists products that are known to cause issues.

I am not able to modify this security software (no admin privileges on machine)
The only workaround that fixed my problem is "wsl-vpnkit".

https://github.com/sakai135/wsl-vpnkit

Hopefully I could help.

[JakubKoralewski]

Had same issue. Restarting fixed it, but still weird.

[microsoft-github-policy-service]

This issue has been automatically closed since it has not had any activity for the past year. If you're still experiencing this issue please re-file this as a new issue or feature request.

Thank you!