implement Start-IptablesProcess

this strips away some splatting boilerplate of the other iptables functions

expose_forwards.ps1

@@ -1,6 +1,20 @@
 #Requires -Modules powershell-yaml
 $ErrorActionPreference = 'Stop'
 
+function Start-IptablesProcess {
+    param (
+        [array]$ArgumentList
+    )
+
+    $splat = @{
+        FilePath     = 'iptables'
+        ArgumentList = $ArgumentList
+        Wait         = $true
+        PassThru     = $true
+    }
+
+    Start-Process @splat
+}
 function Test-IptablesChain {
     param (
         [string]$Chain,
@@ -41,14 +55,7 @@ function Test-IptablesRule {
         $Chain
     )+$Rule
 
-    $check_splat = @{
-        FilePath     = 'iptables'
-        ArgumentList = $argument_list
-        Wait         = $true
-        PassThru     = $true
-    }
-
-    $check = Start-Process @check_splat
+    $check = Start-IptablesProcess -ArgumentList $argument_list
 
     Write-Output ($check.ExitCode -eq 0)
 }
@@ -66,16 +73,11 @@ function Add-IptablesRule {
         $Chain
     )+$Rule
 
-    $add_splat = @{
-        FilePath     = 'iptables'
-        ArgumentList = $argument_list
-        Wait         = $true
-        PassThru     = $true
-    }
-
     if(-not (Test-IptablesRule -Chain $Chain -Rule $Rule)) {
-        $add = Start-Process @add_splat
-        if(0 -ne $add.ExitCode) {
+        $add = Start-IptablesProcess -ArgumentList $argument_list
+        if(0 -eq $add.ExitCode) {
+            Write-Output $true
+        } else {
             Write-Error 'Adding iptables rule failed'
         }
     }