WSL 2 uses a Hyper-V Virtual Network adapter. Network connectivity works without any issue when a VPN is not in use. However when a Cisco AnyConnect VPN session is established Firewall Rules and Routes are added which breaks connectivity within the WSL 2 VM. This issue is tracked WSL/issues/4277
Below outline steps to automatically configure the Interface metric on VPN connect and update DNS settings (/etc/resolv.conf) on connect/disconnect.
After connecting to the VPN, you'll want to modify the Interface Metric of the Cisco VPN Adapter
PS C:\Users\gyurgyik> Get-NetAdapter | Where-Object {$_.InterfaceDescription -Match "Cisco AnyConnect"} | Set-NetIPInterface -InterfaceMetric 6000
Run the following command in Powershell with Administrative permission.
At this point you should have connectivity in your container (but without name resolution). You can test this by running ping 8.8.8.8
.
Once connected the VPN determine the DNS servers that are configured:
PS C:\Users\gyurgyik> (Get-NetAdapter | Where-Object InterfaceDescription -like "Cisco AnyConnect*" | Get-DnsClientServerAddress).ServerAddresses
10.10.0.124
10.10.0.132
Update /etc/resolv.conf
N-20S5PF20MB4R:~$ cat /etc/resolv.conf
nameserver 10.10.0.124
nameserver 10.10.0.132
Verify Connectivity
ping google.com -c 4
Save the following scripts to %homepath%\wsl\scripts
Get-NetAdapter | Where-Object {$_.InterfaceDescription -Match "Cisco AnyConnect"} | Set-NetIPInterface -InterfaceMetric 6000
$dnsServers = (Get-NetAdapter | Where-Object InterfaceDescription -like "Cisco AnyConnect*" | Get-DnsClientServerAddress).ServerAddresses -join ','
$searchSuffix = (Get-DnsClientGlobalSetting).SuffixSearchList -join ','
function set-DnsWsl($distro) {
if ( $dnsServers ) {
wsl.exe -d $distro -u root /opt/wsl_dns.py --servers $dnsServers --search $searchSuffix
}
else {
wsl.exe -d $distro -u root /opt/wsl_dns.py
}
}
set-DnsWsl fedora
Download from: https://gist.githubusercontent.com/pyther/20bba4aee1a7e1485dd065adbf736891/raw/bb00f46d30da1b1eb7ba0fec4e6946a654c7b186/wsl_dns.py
For each Linux instance:
- Disable automatic updating of resolv.conf by WSL
$ cat <<EOF > /etc/wsl.conf [network] generateResolvConf = false EOF
- Restart/Shutdown WSL:
wsl --shutdown
(WARNING: this will kill all current sessions!)
For each VM, run:
$ cp /mnt/c/Users/$username/wsl/scripts/wsl_dns.py /opt/wsl_dns.py
$ chmod +x /opt/wsl_dns.py
Windows Scheduled Tasks allows you to trigger an action when a certain log event comes in. The Cisco AnyConnect VPN client generates a number of log events.
We will create two tasks. The first task, will configure the interface metric when the VPN connects. The second task, will execute the dns update script inside of your Linux VM when the VPN Connects and Disconnects.
- 2039: VPN Established and Passing Data
- 2061: Network Interface for the VPN has gone down
- 2010: VPN Termination
- 2041: The entire VPN connection has been re-established.
- Open Task Scheduler
- Create a Folder called
WSL
(Optional, but easier to find rules later) - Create Rules
- Update AnyConnect Adapter Interface Metric for WSL2
- General: Check: Run with highest privileges
- Triggers:
- On an Event, Log:
Cisco AnyConnect Secure Mobility Client
, Source:acvpnagent
, Event ID:2039
- On an Event, Log:
Cisco AnyConnect Secure Mobility Client
, Source:acvpnagent
, Event ID:2041
- On an Event, Log:
- Action: Start a program, Program:
Powershell.exe
, Add arguments:-WindowStyle Hidden -NonInteractive -ExecutionPolicy Bypass -File %HOMEPATH%\wsl\scripts\setCiscoVpnMetric.ps1
- Condition: Uncheck: Start the task only if the computer is on AC power
- Update DNS in WSL2 Linux VMs
- Triggers:
- On an Event, Log:
Cisco AnyConnect Secure Mobility Client
, Source:acvpnagent
, Event ID:2039
- On an Event, Log:
Cisco AnyConnect Secure Mobility Client
, Source:acvpnagent
, Event ID:2010
- On an Event, Log:
Cisco AnyConnect Secure Mobility Client
, Source:acvpnagent
, Event ID:2061
- On an Event, Log:
Cisco AnyConnect Secure Mobility Client
, Source:acvpnagent
, Event ID:2041
- At log on: At log on of $USER
- On an Event, Log:
- Action: Start a program, Program:
Powershell.exe
, Add arguments:-WindowStyle Hidden -NonInteractive -ExecutionPolicy Bypass -File %HOMEPATH%\wsl\scripts\setDns.ps1
- Condition: Uncheck: Start the task only if the computer is on AC power
- Triggers:
- Update AnyConnect Adapter Interface Metric for WSL2
- Test: Connect to the VPN, a powershell window should pop-up briefly
Q: Does traffic orginating from the Linux VM still route through the VPN?
A: Yes, I believe so. I did not see any leaked traffic when running a tcpdump on my router.
Q: Are VPN resources accessible from the Linux VM?
A: Yes
Q: Can the Linux VM communicate with Windows?
A: No, it appears a firewall rule is preventing traffic between Windows and the Linux VM.
Q: Can I still run WSL1 instances?
A: Yes, you can run WSL1 and WSL2 insatnces simutaneously
Q: How do I revert/disable these changes?
A: Disable scheduled Tasks, remove/modify /etc/wsl.conf
from each WSL Instance, Reboot
works great but i added an additional trigger with Event ID
2040
. That should re-run the script if AnyConnect decides to reconnect the VPN Tunnel. In my case this caused the Interface Metrics to be wrong again