Synchronize Routing Table with Azure Service Tag Listing

sync.ps1

#region Azure Automation bootstrap
try
{
    $servicePrincipalConnection = Get-AutomationConnection -Name "AzureRunAsConnection"
    "Logging in to Azure..."
    Connect-AzAccount `
        -ServicePrincipal `
        -TenantId $servicePrincipalConnection.TenantId `
        -ApplicationId $servicePrincipalConnection.ApplicationId `
        -CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint 
}
catch {
    if (!$servicePrincipalConnection)
    {
        $ErrorMessage = "Connection AzureRunAsConnection not found."
        throw $ErrorMessage
    } else{
        Write-Error -Message $_.Exception
        throw $_.Exception
    }
}

$smtpCredential = Get-AutomationPSCredential -Name "SendGridCredentials"
#endregion

#region Configuration
# Azure
$routeTableResourceGroupName = "test_group"
$routeTableName = "RT-ForcedTunneling"
$routeNamePrefix = "ps-" # used only to detect candidates for deletion
$services = @{
    "AzureBackup" = @("WestEurope", "NorthEurope")
}
# Mail notifications
$smtpServer = "smtp.sendgrid.net"
$emailFrom = "Azure Automations <[email protected]>"
$emailTo = "[email protected]" # CC added to every e-mail sent by this script

#endregion

$routeTable = Get-AzRouteTable -ResourceGroupName $routeTableResourceGroupName -Name $routeTableName
$serviceTags = Get-AzNetworkServiceTag -Location "westeurope"

$seenPrefixes = @()
$addedPrefixes = @()
foreach($service in $services.GetEnumerator()) {
    $serviceName = $service.Name
    $regions = $service.Value

    foreach($region in $regions) {
        $serviceGroups = $serviceTags.Values | Where-Object { $_.Properties.SystemService -eq $serviceName -and $_.Properties.Region -eq $region }
        $prefixes = $serviceGroups | Select-Object -ExpandProperty Properties | Select-Object -ExpandProperty AddressPrefixes

        foreach($prefix in $prefixes) {
            $existingRoute = $routeTable.Routes | Where-Object AddressPrefix -eq $prefix
            if($existingRoute) {
                $seenPrefixes += $existingRoute.AddressPrefix

                continue # nothing else is needed
            }
            
            $routeName = "$($routeNamePrefix)$($serviceName).$($region)-$($prefix.Replace("/", "_"))"
            Write-Output " - Inserting new route for prefix $prefix with name $routeName"
            Add-AzRouteConfig -RouteTable $routeTable -Name $routeName -AddressPrefix $prefix -NextHopType "Internet" | Out-Null
            $addedPrefixes += $prefix
        }
    }
}

Write-Output "Commiting changes to the route table"
Set-AzRouteTable -RouteTable $routeTable | Out-Null

# What can be removed?
$routesToRemove = $routeTable.Routes | Where-Object { $_.AddressPrefix -notin $seenPrefixes -and $_.AddressPrefix -notin $addedPrefixes -and $_.Name.StartsWith($routeNamePrefix) }

# should we send an email notification?
if($addedPrefixes.Count -gt 0 -or $removePrefixes) {
    
}

#region Functions
function Build-HtmlTable {
    param(
        $Object,
        $Columns,
        $CustomPrefix,
        $Tag = "td",
        $Style = ""
    )

    $row = "<tr style='text-align: left' valign=top>$($CustomPrefix)"
    foreach($column in $Columns) {
        if($Object) {
            $value = $Object.$column
        } else {
            $value = $column
        }

        $row += "<$($tag) style=`"$($Style)`">$($value)</$($tag)>"
    }
    $row += "</tr>"

    $row
}

$css = @{
    th = "text-align:left;color: #495057; background-color: #e9ecef; border-color: #dee2e6;line-height: 22px; font-size: 14px; border-top-width: 1px; border-top-style: solid; border-bottom-width: 1px; border-bottom-style: solid; margin: 0; padding: 12px;"
    td = "text-align:left;border-spacing: 0px; border-collapse: collapse; line-height: 22px; font-size: 14px; border-color: #e9ecef;  border-top-width: 1px; border-top-style: solid; border-bottom-width: 1px; border-bottom-style: solid; margin: 0; padding: 12px;" 
}

$tableColumns = [Ordered]@{
    Indexer = ""
    Name = "Name"
    AddressPrefix = "Prefix"
    NextHopType = "Next Hop Type"
}
#endregion

$messageBody  = "<html><head><meta http-equiv='Content-Type' content='text/html; charset=utf-8'></head><body style='font-size: 14px; font-family: Helvetica, Arial, sans-serif;'>"
$messageBody += "<p style='font-size: 14px;'>Routing table <strong>$($routeTableName)</strong> in the resource group <strong>$($routeTableResourceGroupName)</strong> has been updated.</p>"

if($addedPrefixes.Count -gt 0) {
    $routes = $routeTable.Routes | Where-Object AddressPrefix -In $addedPrefixes

    $messageBody += "<div style=`"margin-top: 20px; margin-bottom: 10px; font-weight: 500; color: inherit; vertical-align: baseline; font-size: 20px; line-height: 24.4px;`">Created routes</div>"
    $messageBody += '<table border="0" cellpadding="0" cellspacing="0" style="font-family: Helvetica, Arial, sans-serif; mso-table-lspace: 0pt; mso-table-rspace: 0pt; border-spacing: 0px; border-collapse: collapse; width: 100%; max-width: 100%;" bgcolor="#ffffff">'
    $messageBody += Build-HtmlTable -Columns $tableColumns.Values -Tag "th" -Style $css.th

    $i = 1
    foreach($route in $routes) {
        $rowData = $route | Select-Object @{ Name = "Indexer"; Expression = { "<strong>$($i).</strong>" } }, *
        $messageBody += Build-HtmlTable -Object $rowData -Columns $tableColumns.Keys -Style $css.td
        $i += 1
    }

    $messageBody += "</table>"
}

if($routesToRemove) {
    $messageBody += "<div style=`"margin-top: 20px; margin-bottom: 10px; font-weight: 500; color: inherit; vertical-align: baseline; font-size: 20px; line-height: 24.4px;`">No longer needed routes</div>"
    $messageBody += "<p style='font-size: 14px;'>These routes might be removed from the routing table as their prefixes are no longer present in Azure Service Tags reference list.</p>"
    $messageBody += '<table border="0" cellpadding="0" cellspacing="0" style="font-family: Helvetica, Arial, sans-serif; mso-table-lspace: 0pt; mso-table-rspace: 0pt; border-spacing: 0px; border-collapse: collapse; width: 100%; max-width: 100%;" bgcolor="#ffffff">'
    $messageBody += Build-HtmlTable -Columns $tableColumns.Values -Tag "th" -Style $css.th

    $i = 1
    foreach($route in $routesToRemove) {
        $rowData = $route | Select-Object @{ Name = "Indexer"; Expression = { "<strong>$($i).</strong>" } }, *
        $messageBody += Build-HtmlTable -Object $rowData -Columns $tableColumns.Keys -Style $css.td
        $i += 1
    }

    $messageBody += "</table>"
}

$messageBody += "</body></html>"
$messageBody | Set-Clipboard

if($addedPrefixes.Count -gt 0 -or $routesToRemove) {
    Send-MailMessage -SmtpServer $smtpServer -Credential $smtpCredential -UseSsl -Port 587 `
                     -From $emailFrom -To $emailTo -Subject "Updated Routing Table $($routeTableName)" `
                     -Body $messageBody -BodyAsHtml -Encoding UTF8
}