Merge pull request #700 from hashstat/master

Add documentation on Linux ipc abstract namespace support and a bug fix.

.gitignore

@@ -69,6 +69,7 @@ tests/test_inproc_connect
 tests/test_linger
 tests/test_security_null
 tests/test_security_plain
+tests/test_abstract_ipc
 tests/test*.log
 tests/test*.trs
 src/platform.hpp*

doc/zmq_ipc.txt

@@ -48,6 +48,11 @@ NOTE: the endpoint pathname must be writable by the process. When the endpoint
 starts with '/', e.g., `ipc:///pathname`, this will be an _absolute_ pathname.
 If the endpoint specifies a directory that does not exist, the bind shall fail.
 
+NOTE: on Linux only, when the endpoint pathname starts with `@`, the abstract
+namespace shall be used.  The abstract namespace is independent of the
+filesystem and if a process attempts to bind an endpoint already bound by a
+process, it will fail.  See unix(7) for details.
+
 Connecting a socket
 ~~~~~~~~~~~~~~~~~~~
 When connecting a 'socket' to a peer address using _zmq_connect()_ with the

src/ipc_address.cpp

@@ -51,11 +51,18 @@ int zmq::ipc_address_t::resolve (const char *path_)
         errno = ENAMETOOLONG;
         return -1;
     }
+#if defined ZMQ_HAVE_LINUX
+    if (path_[0] == '@' && !path_[1]) {
+            errno = EINVAL;
+            return -1;
+    }
+#endif
 
     address.sun_family = AF_UNIX;
     strcpy (address.sun_path, path_);
 #if defined ZMQ_HAVE_LINUX
-    if (*path_ == '@')
+    /* Abstract sockets on Linux start with '\0' */
+    if (path_[0] == '@')
         *address.sun_path = '\0';
 #endif
     return 0;
@@ -73,10 +80,10 @@ int zmq::ipc_address_t::to_string (std::string &addr_)
     s << "ipc://" << address.sun_path;
 #else
     s << "ipc://";
-    if (*address.sun_path)
-       s << address.sun_path;
-    else
+    if (!address.sun_path[0] && address.sun_path[1])
        s << "@" << address.sun_path + 1;
+    else
+       s << address.sun_path;
 #endif
     addr_ = s.str ();
     return 0;
@@ -89,6 +96,10 @@ const sockaddr *zmq::ipc_address_t::addr () const
 
 socklen_t zmq::ipc_address_t::addrlen () const
 {
+#if defined ZMQ_HAVE_LINUX
+    if (!address.sun_path[0] && address.sun_path[1])
+        return (socklen_t) strlen(address.sun_path + 1) + sizeof (sa_family_t) + 1;
+#endif
     return (socklen_t) sizeof (address);
 }