Update-OpenVPNRoute.ps1

# Author: ak1ra
# Date: 2022-01-23
# 自动添加访问特定域名时使用 OpenVPN 网关作为下一条的路由

# 配置命令行选项
Param(
    [string]$Action = "add",
    [string]$Domain = "cloud.tencent.com",
    [Parameter(Mandatory=$false)][Int32]$InterfaceIndex,
    [string]$InterfaceDescription = "TAP-Windows Adapter V9",
    [string]$InterfaceAlias = "OpenVPN",
    [string]$DestinationPrefix = "10.0.0.0/9"
)

# 配置临时文件保存域名解析记录
$ResolveResultSaved = "${Env:TEMP}\resolve_${Domain}.txt"

# 根据 InterfaceDescription 获取网卡
$TapNetAdapter = Get-NetAdapter -InterfaceDescription $InterfaceDescription

if ($PSBoundParameters.ContainsKey('InterfaceIndex')) {
    # 直接使用命令行参数传入的 InterfaceIndex
    $InterfaceIndex = $InterfaceIndex
} elseif (($TapNetAdapter | Measure-Object).Count -eq 1) {
    # 通过 InterfaceDescription 获取网卡, 可能出现多个对象
    # 因此仅当存在 1 个 TAP 网卡时才使用此方法
    $InterfaceIndex = $TapNetAdapter.ifIndex
} else {
    # 也直接传入 TAP 网卡名称, 默认值为 OpenVPN
    $InterfaceIndex = (Get-NetAdapter -InterfaceAlias $InterfaceAlias).ifIndex
}

# 获取 OpenVPN 下发路由的下一跳地址
$NextHop = (Get-NetRoute -ifIndex $InterfaceIndex -DestinationPrefix $DestinationPrefix ).NextHop

# 查询 $Domain 的 A 记录并保存到文件(保存状态), 然后再读取循环添加路由
if ($Action -eq "Add") {
    $ResolveResult = (Resolve-DnsName -Type A $Domain).ipAddress | Tee-Object -FilePath $ResolveResultSaved
    $ResolveResult | ForEach-Object -Process {
        New-NetRoute -DestinationPrefix "$_/32" -NextHop $NextHop -InterfaceIndex $InterfaceIndex
    }
} elseif ($Action -match "(Del(ete)?|Remove)") {
    $ResolveResult = Get-Content -Path $ResolveResultSaved
    $ResolveResult | ForEach-Object -Process {
        Remove-NetRoute -DestinationPrefix "$_/32" -NextHop $NextHop -InterfaceIndex $InterfaceIndex -Confirm:$false
    }
    Remove-Item -Path $ResolveResultSaved
} else {
    Get-NetRoute -ifIndex $InterfaceIndex
}