Use openvpn inside WSL2 and be able to route traffic from windows through linux

vpn-nat.ps1

# On linux side you need iptables
# On windows side you need sudo which can be installed with scoop

$CidrBlocks = "10.0.0.0/16", "10.1.0.0/16", "10.70.0.0/16", "10.3.0.0/16"
$WslIP = "$(wsl -- ip addr show dev eth0 | Select-String -Pattern 'inet ')"
$WslIP = $WslIP.Split(' ').Where{ $_.Length }[1].Split('/')[0]

function BuildIptablesRoute {
    param (
        [Parameter(Mandatory = $true)]
        [String]
        $CidrBlock
    )

    return "iptables --table nat --append POSTROUTING --destination '$CidrBlock' -j MASQUERADE"
}

function BuildWindowsRoute {
    param (
        [Parameter(Mandatory = $true)]
        [String]
        $CidrBlock,
        [Parameter(Mandatory = $true)]
        [String]
        $GatewayIp
    )
    $Ip, $NetmaskBits = $CidrBlock.Split("/")
    $Netmask = NetmaskBitsToString -NetmaskBits $NetmaskBits

    return "route add $Ip mask $Netmask $GatewayIp"
}

function NetmaskBitsToString {
    param (
        [Parameter(Mandatory = $true)]
        [ValidateRange(0, 32)]
        [UInt32]
        $NetmaskBits
    )

    $Mask = ([System.Math]::Pow(2, (32 - $NetmaskBits)) - 1) -bxor [System.UInt32]::MaxValue
    
    $Bytes = 3..0 | ForEach-Object { $Mask -shr $_ * 8 -band [System.Byte]::MaxValue }
    return $Bytes | Join-String -Separator "."
}

Write-Output "Setting up linux side with", $CidrBlocks
$IptablesRules = (
    $CidrBlocks | 
    ForEach-Object { BuildIptablesRoute -CidrBlock $_ } | 
    Join-String -Separator " && "
)

Write-Output "Type the sudo password for your user on linux"
wsl -- sudo bash -exc "${IptablesRules}"

Write-Output "Adding routes on windows side"

$WindowsRoutes = (
    $CidrBlocks | 
    ForEach-Object { BuildWindowsRoute -CidrBlock $_ -GatewayIp $WslIP } | 
    Join-String -Separator "; " 
)
sudo powershell -Command "Set-PSDebug -Trace 1 ; $WindowsRoutes"