add Test-IptablesRule

expose_forwards.ps1

@@ -27,6 +27,31 @@ function Add-IptablesChain {
         iptables -t $Table -N $Chain
     }
 }
+function Test-IptablesRule {
+    param (
+        [string]$Chain,
+        [string]$Table = 'nat',
+        [array]$Rule
+    )
+
+    $argument_list = @(
+        '-t'
+        $Table
+        '-C'
+        $Chain
+    )+$Rule
+
+    $check_splat = @{
+        FilePath     = 'iptables'
+        ArgumentList = $argument_list
+        Wait         = $true
+        PassThru     = $true
+    }
+
+    $check = Start-Process @check_splat
+
+    Write-Output ($check.ExitCode -eq 0)
+}
 
 # setup SWARM-NAT chain
 $chain = 'SWARM-NAT'