Add shutdownIfUnreadable file feature: shut down if shutdownIfUnreadable in home folder is in fact existent but unreadable (e.g. broken link). This enables nifty shutdown on .app trashing feature for OSX.

node/Node.cpp

@@ -467,6 +467,7 @@ Node::ReasonForTermination Node::run()
 
 	// Core I/O loop
 	try {
+		std::string shutdownIfUnreadablePath(_r->homePath + ZT_PATH_SEPARATOR_S + "shutdownIfUnreadable");
 		uint64_t lastNetworkAutoconfCheck = Utils::now() - 5000; // check autoconf again after 5s for startup
 		uint64_t lastPingCheck = 0;
 		uint64_t lastClean = Utils::now(); // don't need to do this immediately
@@ -476,6 +477,13 @@ Node::ReasonForTermination Node::run()
 		long lastDelayDelta = 0;
 
 		while (impl->reasonForTermination == NODE_RUNNING) {
+			if (Utils::fileExists(shutdownIfUnreadablePath.c_str(),false)) {
+				FILE *tmpf = fopen(shutdownIfUnreadablePath.c_str(),"r");
+				if (!tmpf)
+					return impl->terminateBecause(Node::NODE_NORMAL_TERMINATION,"shutdownIfUnreadable was not readable");
+				fclose(tmpf);
+			}
+
 			uint64_t now = Utils::now();
 			bool resynchronize = false;
 

node/Utils.cpp

@@ -246,7 +246,7 @@ no getSecureRandom() implementation;
 
 void Utils::lockDownFile(const char *path,bool isDir)
 {
-#if defined(__APPLE__) || defined(__linux__) || defined(linux) || defined(__LINUX__) || defined(__linux)
+#ifdef __UNIX_LIKE__
 	chmod(path,isDir ? 0700 : 0600);
 #else
 #ifdef _WIN32
@@ -263,6 +263,16 @@ uint64_t Utils::getLastModified(const char *path)
 	return (((uint64_t)s.st_mtime) * 1000ULL);
 }
 
+bool Utils::fileExists(const char *path,bool followLinks)
+{
+	struct stat s;
+#ifdef __UNIX_LIKE__
+	if (!followLinks)
+		return (lstat(path,&s) == 0);
+#endif
+	return (stat(path,&s) == 0);
+}
+
 int64_t Utils::getFileSize(const char *path)
 {
 	struct stat s;

node/Utils.hpp

@@ -177,12 +177,10 @@ public:
 
 	/**
 	 * @param path Path to check
+	 * @param followLinks Follow links (on platforms with that concept)
 	 * @return True if file or directory exists at path location
 	 */
-	static inline bool fileExists(const char *path)
-	{
-		return (getLastModified(path) != 0);
-	}
+	static bool fileExists(const char *path,bool followLinks = true);
 
 	/**
 	 * @param path Path to file