From e46ae80b00eab500bd93a86c8077a0595ce79de0 Mon Sep 17 00:00:00 2001
From: Matt Kotsenas <mattkot@microsoft.com>
Date: Wed, 5 Jan 2022 15:46:42 -0800
Subject: [PATCH] Refactor DllImports in Microsoft.Extensions.Hosting.Systemd

Refactor the DllImports in Microsoft.Extensions.Hosting.Systemd into
Common/src/Interop following the interop guidelines.
---
 .../Common/src/Interop/Unix/Interop.Libraries.cs    |  2 ++
 .../src/Interop/Unix/libc/Interop.GetParentPid.cs   | 13 +++++++++++++
 .../src/Microsoft.Extensions.Hosting.Systemd.csproj |  5 +++++
 .../src/SystemdHelpers.cs                           |  6 +-----
 4 files changed, 21 insertions(+), 5 deletions(-)
 create mode 100644 src/libraries/Common/src/Interop/Unix/libc/Interop.GetParentPid.cs

diff --git a/src/libraries/Common/src/Interop/Unix/Interop.Libraries.cs b/src/libraries/Common/src/Interop/Unix/Interop.Libraries.cs
index 8e2d9046af8987..1a0114cca21895 100644
--- a/src/libraries/Common/src/Interop/Unix/Interop.Libraries.cs
+++ b/src/libraries/Common/src/Interop/Unix/Interop.Libraries.cs
@@ -5,6 +5,8 @@ internal static partial class Interop
 {
     internal static partial class Libraries
     {
+        internal const string Libc = "libc";
+
         // Shims
         internal const string SystemNative = "libSystem.Native";
         internal const string NetSecurityNative = "libSystem.Net.Security.Native";
diff --git a/src/libraries/Common/src/Interop/Unix/libc/Interop.GetParentPid.cs b/src/libraries/Common/src/Interop/Unix/libc/Interop.GetParentPid.cs
new file mode 100644
index 00000000000000..95b27abf158287
--- /dev/null
+++ b/src/libraries/Common/src/Interop/Unix/libc/Interop.GetParentPid.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class libc
+    {
+        [GeneratedDllImport(Libraries.Libc, EntryPoint = "getppid")]
+        internal static partial int GetParentPid();
+    }
+}
diff --git a/src/libraries/Microsoft.Extensions.Hosting.Systemd/src/Microsoft.Extensions.Hosting.Systemd.csproj b/src/libraries/Microsoft.Extensions.Hosting.Systemd/src/Microsoft.Extensions.Hosting.Systemd.csproj
index 5d375e67feab7c..b9faefd40f2f07 100644
--- a/src/libraries/Microsoft.Extensions.Hosting.Systemd/src/Microsoft.Extensions.Hosting.Systemd.csproj
+++ b/src/libraries/Microsoft.Extensions.Hosting.Systemd/src/Microsoft.Extensions.Hosting.Systemd.csproj
@@ -18,6 +18,11 @@
     <Compile Remove="SystemdLifetime.netstandard.cs" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Compile Include="$(CommonPath)Interop\Unix\libc\Interop.GetParentPid.cs" Link="Common\Interop\Unix\libc\Interop.GetParentPid.cs" />
+    <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs" Link="Common\Interop\Unix\Interop.Libraries.cs" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Extensions.Hosting\src\Microsoft.Extensions.Hosting.csproj" />
   </ItemGroup>
diff --git a/src/libraries/Microsoft.Extensions.Hosting.Systemd/src/SystemdHelpers.cs b/src/libraries/Microsoft.Extensions.Hosting.Systemd/src/SystemdHelpers.cs
index 244e41c69e179d..b582580c9e97fe 100644
--- a/src/libraries/Microsoft.Extensions.Hosting.Systemd/src/SystemdHelpers.cs
+++ b/src/libraries/Microsoft.Extensions.Hosting.Systemd/src/SystemdHelpers.cs
@@ -4,7 +4,6 @@
 using System;
 using System.Globalization;
 using System.IO;
-using System.Runtime.InteropServices;
 using System.Text;
 
 namespace Microsoft.Extensions.Hosting.Systemd
@@ -34,7 +33,7 @@ private static bool CheckParentIsSystemd()
             try
             {
                 // Check whether our direct parent is 'systemd'.
-                int parentPid = GetParentPid();
+                int parentPid = Interop.libc.GetParentPid();
                 string ppidString = parentPid.ToString(NumberFormatInfo.InvariantInfo);
                 byte[] comm = File.ReadAllBytes("/proc/" + ppidString + "/comm");
                 return comm.AsSpan().SequenceEqual(Encoding.ASCII.GetBytes("systemd\n"));
@@ -45,8 +44,5 @@ private static bool CheckParentIsSystemd()
 
             return false;
         }
-
-        [GeneratedDllImport("libc", EntryPoint = "getppid")]
-        private static partial int GetParentPid();
     }
 }