Add support for setting umask when binding

This is needed to be able to control the permissions of any created ipc
sockets.

CMakeLists.txt

@@ -6,7 +6,7 @@ include(GNUInstallDirs)
 
 set(LOKIMQ_VERSION_MAJOR 1)
 set(LOKIMQ_VERSION_MINOR 1)
-set(LOKIMQ_VERSION_PATCH 4)
+set(LOKIMQ_VERSION_PATCH 5)
 set(LOKIMQ_VERSION "${LOKIMQ_VERSION_MAJOR}.${LOKIMQ_VERSION_MINOR}.${LOKIMQ_VERSION_PATCH}")
 message(STATUS "lokimq v${LOKIMQ_VERSION}")
 

lokimq/lokimq.h

@@ -246,6 +246,13 @@ public:
     /// Allows you to set options on the internal zmq context object.  For advanced use only.
     int set_zmq_context_option(int option, int value);
 
+    /** The umask to apply when constructing sockets (which affects any new ipc:// listening sockets
+     * that get created).  Does nothing if set to -1 (the default), and does nothing on Windows.
+     * Note that the umask is applied temporarily during `start()`, so may affect other threads that
+     * create files/directories at the same time as the start() call.
+     */
+    int STARTUP_UMASK = -1;
+
 private:
 
     /// The lookup function that tells us where to connect to a peer, or empty if not found.

lokimq/proxy.cpp

@@ -2,6 +2,12 @@
 #include "lokimq-internal.h"
 #include "hex.h"
 
+#ifndef _WIN32
+extern "C" {
+#include <sys/stat.h>
+}
+#endif
+
 namespace lokimq {
 
 void LokiMQ::proxy_quit() {
@@ -330,6 +336,12 @@ void LokiMQ::proxy_loop() {
     if (!workers.empty())
         throw std::logic_error("Internal error: proxy thread started with active worker threads");
 
+#ifndef _WIN32
+    int saved_umask = -1;
+    if (STARTUP_UMASK >= 0)
+        saved_umask = umask(STARTUP_UMASK);
+#endif
+
     for (size_t i = 0; i < bind.size(); i++) {
         auto& b = bind[i].second;
         zmq::socket_t listener{context, zmq::socket_type::router};
@@ -354,6 +366,12 @@ void LokiMQ::proxy_loop() {
         incoming_conn_index[conn_id] = connections.size() - 1;
         b.index = connections.size() - 1;
     }
+
+#ifndef _WIN32
+    if (saved_umask != -1)
+        umask(saved_umask);
+#endif
+
     pollitems_stale = true;
 
     // Also add an internal connection to self so that calling code can avoid needing to