This patch ensures that the mDNS daemon will not fork (daemonize) and will stop
when the port used on the Erlang side is closed.

--- mDNSResponder-878.1.1.orig/mDNSPosix/PosixDaemon.c	2017-01-11 21:40:20.000000000 +0100
+++ mDNSResponder-878.1.1.new/mDNSPosix/PosixDaemon.c	2017-11-26 15:31:03.000000000 +0100
@@ -98,26 +98,6 @@
     mDNS_ConfigChanged(m);
 }

-// Do appropriate things at startup with command line arguments. Calls exit() if unhappy.
-mDNSlocal void ParseCmdLinArgs(int argc, char **argv)
-{
-    if (argc > 1)
-    {
-        if (0 == strcmp(argv[1], "-debug")) mDNS_DebugMode = mDNStrue;
-        else printf("Usage: %s [-debug]\n", argv[0]);
-    }
-
-    if (!mDNS_DebugMode)
-    {
-        int result = daemon(0, 0);
-        if (result != 0) { LogMsg("Could not run as daemon - exiting"); exit(result); }
-#if __APPLE__
-        LogMsg("The POSIX mdnsd should only be used on OS X for testing - exiting");
-        exit(-1);
-#endif
-    }
-}
-
 mDNSlocal void DumpStateLog()
 // Dump a little log of what we've been up to.
 {
@@ -126,11 +106,29 @@
     LogMsg("----  END STATE LOG  ----");
 }

+mDNSlocal void CheckStdInClosed(int fd, short filter, void *context)
+{
+    int byte;
+    ssize_t bytes_read;
+
+    (void)filter; // Unused
+    (void)context; // Unused
+
+    bytes_read = read(fd, &byte, 1);
+    if (bytes_read == 0)
+    {
+        LogMsg("Stdin closed, terminating");
+        raise(SIGTERM);
+    }
+}
+
 mDNSlocal mStatus MainLoop(mDNS *m) // Loop until we quit.
 {
     sigset_t signals;
     mDNSBool gotData = mDNSfalse;

+    (void) mDNSPosixAddFDToEventLoop(STDIN_FILENO, CheckStdInClosed, NULL);
+
     mDNSPosixListenForSignalInEventLoop(SIGINT);
     mDNSPosixListenForSignalInEventLoop(SIGTERM);
     mDNSPosixListenForSignalInEventLoop(SIGUSR1);
@@ -172,7 +170,9 @@
 {
     mStatus err;

-    ParseCmdLinArgs(argc, argv);
+    (void)argc; // Unused
+    (void)argv; // Unused
+    mDNS_DebugMode = mDNStrue;

     LogMsg("%s starting", mDNSResponderVersionString);