Gateway-keepaliveForPowershell/GateWay-KeepAlive.ps1

. $(-Join($(pwd).Path, '\config.ps1'))
. $(-Join($(pwd).Path, '\proxy-test.ps1'))

function isDhcpEnable(){
    return Get-NetIPConfiguration | select-object InterfaceAlias, IPv4Address, @{n="dhcp";e={$_.NetIPv4Interface.DHCP}} | Select-Object -ExpandProperty dhcp
}

function isForeignConnected {
    # check foreign network availability
    $result = Test-NetConnection -ComputerName $Global:TestDomain -Port 443

    if ($result.TcpTestSucceeded) {
        Write-Host "Successfully connected to $($Global:TestDomain) via HTTPS. isCustomGateway:$($Global:isCustomGateway)"
        return $true
    } else {
        Write-Host "Failed to connect to $($Global:TestDomain) via HTTPS. isCustomGateway:$($Global:isCustomGateway)"
        return $false
    }  
}

function isNetworkConnected {
    # check network availability
    $result = $(Test-Connection -ComputerName $Global:TestIP -Count 1).Status -eq 'Success'
    if ($result) {
        Write-Host "Successfully connected to $($Global:TestIP) via ICMP. isCustomGateway:$($Global:isCustomGateway)"
        return $true
    } else {
        Write-Host "Failed to connect to $($Global:TestIP) via ICMP. isCustomGateway:$($Global:isCustomGateway)"
        return $false
    }  
}

function setDhcp($enable){
    if($enable){
        Set-NetIPInterface -InterfaceAlias $Global:TargetNetworkAdapter.name -Dhcp Enabled
        Write-Host enable dhcp
    } else {
        Set-NetIPInterface -InterfaceAlias $Global:TargetNetworkAdapter.name -Dhcp Disabled
        Write-Host disable dhcp
    }
}

function changeGateway{
    param(
        $adapter,$isCustomGateway
    )
    Write-Host "Changing gateway for adapter: $($adapter.Name) isCustomGateway $($isCustomGateway)"
    
  
    # check gateway availability
    if($isCustomGateway){
        $currentGateway = $(Get-NetIPConfiguration).IPv4DefaultGateway.NextHop
        if($currentGateway -eq $Global:TargetGateway){
            Write-Host "current gateway is $currentGateway same as targetGateway $Global:TargetGateway, change gateway canceled"
            $Global:isCustomGateway = $true
            return
        }
        $result = $(Test-Connection $Global:TargetGateway -Count 1).Status
        if (! ($result -eq 'Success')){
            Write-Host custom gateway $Global:TargetGateway is $result, refuse to change
            return
        }
    }

    # check current ip configuration
    $existingIP = Get-NetIPAddress -InterfaceAlias $adapter.Name -AddressFamily IPv4

    # if have ip configuration, delete it
    if ($existingIP) {
        Write-Host "Removing existing IP address: $($existingIP.IPAddress)"
        Remove-NetIPAddress -InterfaceAlias $adapter.Name -Confirm:$false
    }

    # delete current route(gateway)
    $existingRoute = Get-NetRoute -InterfaceAlias $adapter.Name -DestinationPrefix "0.0.0.0/0"
    if ($existingRoute) {
        Write-Host "Removing existing default route..."
        Remove-NetRoute -InterfaceAlias $adapter.Name  -Confirm:$false
    }

    if ($isCustomGateway){ #setting gateway

        # config customGateway
        $Global:isCustomGateway = $true

        # setting dns server
        Set-DnsClientServerAddress -InterfaceAlias $adapter.name -ServerAddresses ($Global:TargetGateway, $Global:TargetGateway)
        # disable dhcp
        setDhcp($false)
        # setting gateway to customGateway
        New-NetIPAddress -InterfaceAlias $adapter.Name -AddressFamily IPv4 -IPAddress $Global:TargetIP -PrefixLength 24 -DefaultGateway $Global:TargetGateway
    } else {
        # config originalGateway
        $Global:isCustomGateway = $false

        # setting dns server
        Set-DnsClientServerAddress -InterfaceAlias $adapter.name -ServerAddresses ($Global:originalDns, $Global:originalDns)

        # setting gateway to originalGateway
        New-NetIPAddress -InterfaceAlias $adapter.Name -AddressFamily IPv4 -IPAddress $Global:TargetIP -PrefixLength 24 -DefaultGateway $Global:originalGateway
    }
    Start-Sleep 3
}


function getIPAddress(){
    $IP = Get-NetIPConfiguration | Select-Object -ExpandProperty IPV4Address | Select-Object -ExpandProperty IPAddress
    return $IP
}

function getNetworkAdapter(){
    $networkAdapters = Get-NetAdapter | ForEach-Object {
        [PSCustomObject]@{
            Name       = $_.Name
            Interface  = $_.InterfaceDescription
            Status     = $_.Status
            LinkSpeed  = $_.LinkSpeed
            MacAddress = $_.MacAddress
        }
    }
    
    foreach ($networkAdapter in $networkAdapters){
        if($networkAdapter.name.Contains($TargetNetworkAdapterKeyword)){
            $Global:TargetNetworkAdapter = $networkAdapter
            break;
        }
    }
    Write-Host "getNetworkAdapter: " $Global:TargetNetworkAdapter
}

function init {
    # check permission
    $IsAdmin = [Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()
    if (-not $IsAdmin.IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)) {
        # if not admin permission, restart it with admin permission
        Write-Host "Requesting Administrator privileges..."
        Start-Process pwsh -ArgumentList "-NoExit", "-File", $PSCommandPath -Verb RunAs
        exit
    }

    Write-Host "Running with Administrator privileges!"

    # get netAdapter instance
    getNetworkAdapter

    Write-Host "current adapter: $($Global:TargetNetworkAdapter.name)"

    # try to change to customGateway at start
    changeGateway $Global:TargetNetworkAdapter $true
}

function loop(){
    while($true){
        # if network offline and using customGateway, try to restore to originalGateway
        if((!$(isNetworkConnected)) -and $Global:isCustomGateway){
            changeGateway $Global:TargetNetworkAdapter $false
        } 

        # if customGateway proxy is working and using original gateway, try to change to customGateway
        if($(Test-SocksProxy -ProxyHost $Global:TargetGateway -ProxyPort 1070) -and (!$Global:isCustomGateway)){
            Write-Host isCustomGateway $Global:isCustomGateway
            changeGateway $Global:TargetNetworkAdapter $true
        }

        # if customGateway proxy is not working but network still online, do nothing

        Start-Sleep 1
    }
}

init
loop