From 9b63dbe49c69a2be89a7de76ffa19e48c73ab913 Mon Sep 17 00:00:00 2001
From: Prince Pereira <ppereira@microsoft.com>
Date: Fri, 28 Jul 2023 12:15:26 +0530
Subject: [PATCH] Adding port exhaustion script.

---
 .../checkPortExhaustion.ps1                   | 86 +++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 scripts/portCountAvailable/checkPortExhaustion.ps1

diff --git a/scripts/portCountAvailable/checkPortExhaustion.ps1 b/scripts/portCountAvailable/checkPortExhaustion.ps1
new file mode 100644
index 0000000..36de7cb
--- /dev/null
+++ b/scripts/portCountAvailable/checkPortExhaustion.ps1
@@ -0,0 +1,86 @@
+function CountAvailableEphemeralPorts([string]$protocol = "TCP") {
+
+    [uint32]$portRangeSize = 64
+    # First, remove all the text bells and whistle (plain text, table headers, dashes, empty lines, ...) from netsh output 
+    $tcpRanges = (netsh int ipv4 sh excludedportrange $protocol) -replace "[^0-9,\ ]", '' | ? { $_.trim() -ne "" }
+ 
+    # Then, remove any extra space characters. Only capture the numbers representing the beginning and end of range
+    $tcpRangesArray = $tcpRanges -replace "\s+(\d+)\s+(\d+)\s+", '$1,$2' | ConvertFrom-String -Delimiter ","
+    #Convert from PSCustomObject to Object[] type
+    $tcpRangesArray = @($tcpRangesArray)
+    
+    # Extract the ephemeral ports ranges
+    $EphemeralPortRange = (netsh int ipv4 sh dynamicportrange $protocol) -replace "[^0-9]", '' | ? { $_.trim() -ne "" }
+    $EphemeralPortStart = [Convert]::ToUInt32($EphemeralPortRange[0])
+    $EphemeralPortEnd = $EphemeralPortStart + [Convert]::ToUInt32($EphemeralPortRange[1]) - 1
+
+    # Find the external interface
+    $externalInterfaceIdx = (Get-NetRoute -DestinationPrefix "0.0.0.0/0")[0].InterfaceIndex
+    $hostIP = (Get-NetIPConfiguration -ifIndex $externalInterfaceIdx).IPv4Address.IPAddress
+
+    # Extract the used TCP ports from the external interface
+    $usedTcpPorts = (Get-NetTCPConnection -LocalAddress $hostIP -ErrorAction Ignore).LocalPort
+    $usedTcpPorts | % { $tcpRangesArray += [pscustomobject]@{P1 = $_; P2 = $_ } }
+
+    # Extract the used TCP ports from the 0.0.0.0 interface
+    $usedTcpGlobalPorts = (Get-NetTCPConnection -LocalAddress "0.0.0.0" -ErrorAction Ignore).LocalPort
+    $usedTcpGlobalPorts | % { $tcpRangesArray += [pscustomobject]@{P1 = $_; P2 = $_ } }
+    # Sort the list and remove duplicates
+    $tcpRangesArray = ($tcpRangesArray | Sort-Object { $_.P1 } -Unique)
+
+    $tcpRangesList = New-Object System.Collections.ArrayList($null)
+    $tcpRangesList.AddRange($tcpRangesArray)
+
+    # Remove overlapping ranges
+    for ($i = $tcpRangesList.P1.Length - 2; $i -gt 0 ; $i--) { 
+        if ($tcpRangesList[$i].P2 -gt $tcpRangesList[$i + 1].P1 ) { 
+            $tcpRangesList.Remove($tcpRangesList[$i + 1])
+            $i++
+        } 
+    }
+
+    # Remove the non-ephemeral port reservations from the list
+    $filteredTcpRangeArray = $tcpRangesList | ? { $_.P1 -ge $EphemeralPortStart }
+    $filteredTcpRangeArray = $filteredTcpRangeArray | ? { $_.P2 -le $EphemeralPortEnd }
+    
+    if ($null -eq $filteredTcpRangeArray) {
+        $freeRanges = @($EphemeralPortRange[1])
+    }
+    else {
+        $freeRanges = @()
+        # The first free range goes from $EphemeralPortStart to the beginning of the first reserved range
+        $freeRanges += ([Convert]::ToUInt32($filteredTcpRangeArray[0].P1) - $EphemeralPortStart)
+
+        for ($i = 1; $i -lt $filteredTcpRangeArray.length; $i++) {
+            # Subsequent free ranges go from the end of the previous reserved range to the beginning of the current reserved range
+            $freeRanges += ([Convert]::ToUInt32($filteredTcpRangeArray[$i].P1) - [Convert]::ToUInt32($filteredTcpRangeArray[$i - 1].P2) - 1)
+        }
+
+        # The last free range goes from the end of the last reserved range to $EphemeralPortEnd
+        $freeRanges += ($EphemeralPortEnd - [Convert]::ToUInt32($filteredTcpRangeArray[$filteredTcpRangeArray.length - 1].P2))
+    }
+    
+    # Count the number of available free ranges
+    [uint32]$freeRangesCount = 0
+    ($freeRanges | % { $freeRangesCount += [Math]::Floor($_ / $portRangeSize) } )
+
+    return $freeRangesCount
+}
+
+function CheckPortExhaustion {
+    Write-Host "Checking Port Exhaustion"
+    $avTcpPorts = CountAvailableEphemeralPorts -protocol TCP
+    if($avTcpPorts -lt 10) {
+        Write-Host "Available TCP ports are $avTcpPorts. Port exhaustion suspected." -ForegroundColor Red
+        return $true
+    }
+    $avUdpPorts = CountAvailableEphemeralPorts -protocol UDP
+    if($avTcpPorts -lt 10) {
+        Write-Host "Available UDP ports are $avUdpPorts. Port exhaustion suspected." -ForegroundColor Red
+        return $true
+    }
+    Write-Host "Available TCP Ports :  $avTcpPorts , UDP Ports : $avUdpPorts . No port exhaustion suspected." -ForegroundColor Green
+    return $false
+}
+
+CheckPortExhaustion
\ No newline at end of file