Problem: epoll leaks socket on fork+exec

Solution: if available, use epoll_create1 with EPOLL_CLOEXEC flag to
make the process close the socket on fork+exec

CMakeLists.txt

@@ -101,6 +101,10 @@ if (POLLER STREQUAL "")
     set (CMAKE_REQUIRED_INCLUDES)
     if (HAVE_EPOLL)
         set (POLLER "epoll")
+        check_function_exists (epoll_create1 HAVE_EPOLL_CLOEXEC)
+        if (HAVE_EPOLL_CLOEXEC)
+            set (ZMQ_USE_EPOLL_CLOEXEC 1)
+        endif ()
     endif ()
 endif ()
 

acinclude.m4

@@ -801,6 +801,7 @@ kqueue();
 
 dnl ################################################################################
 dnl # LIBZMQ_CHECK_POLLER_EPOLL_RUN([action-if-found], [action-if-not-found])      #
+dnl # LIBZMQ_CHECK_POLLER_EPOLL_CLOEXEC([action-if-found], [action-if-not-found])  #
 dnl # Checks epoll polling system can actually run #
 dnl # For cross-compile, only requires that epoll can link #
 dnl ################################################################################
@@ -828,6 +829,30 @@ epoll_create(10);
     )
 }])
 
+AC_DEFUN([LIBZMQ_CHECK_POLLER_EPOLL_CLOEXEC], [{
+    AC_RUN_IFELSE([
+        AC_LANG_PROGRAM([
+#include <sys/epoll.h>
+        ],[[
+struct epoll_event t_ev;
+int r;
+r = epoll_create1(EPOLL_CLOEXEC);
+return(r < 0);
+        ]])],
+        [$1],[$2],[
+            AC_LINK_IFELSE([
+                AC_LANG_PROGRAM([
+#include <sys/epoll.h>
+                ],[[
+struct epoll_event t_ev;
+epoll_create1(EPOLL_CLOEXEC);
+                ]])],
+                [$1], [$2]
+            )
+        ]
+    )
+}])
+
 dnl ################################################################################
 dnl # LIBZMQ_CHECK_POLLER_DEVPOLL([action-if-found], [action-if-not-found])        #
 dnl # Checks devpoll polling system                                                #
@@ -938,10 +963,17 @@ AC_DEFUN([LIBZMQ_CHECK_POLLER], [{
                 ])
             ;;
             epoll)
-                LIBZMQ_CHECK_POLLER_EPOLL([
-                    AC_MSG_NOTICE([Using 'epoll' polling system])
+                LIBZMQ_CHECK_POLLER_EPOLL_CLOEXEC([
+                    AC_MSG_NOTICE([Using 'epoll' polling system with CLOEXEC])
                     AC_DEFINE(ZMQ_USE_EPOLL, 1, [Use 'epoll' polling system])
+                    AC_DEFINE(ZMQ_USE_EPOLL_CLOEXEC, 1, [Use 'epoll' polling system with CLOEXEC])
                     poller_found=1
+                    ],[
+                    LIBZMQ_CHECK_POLLER_EPOLL([
+                        AC_MSG_NOTICE([Using 'epoll' polling system with CLOEXEC])
+                        AC_DEFINE(ZMQ_USE_EPOLL, 1, [Use 'epoll' polling system])
+                        poller_found=1
+                    ])
                 ])
             ;;
             devpoll)

builds/cmake/platform.hpp.in

@@ -3,6 +3,7 @@
 
 #cmakedefine ZMQ_USE_KQUEUE
 #cmakedefine ZMQ_USE_EPOLL
+#cmakedefine ZMQ_USE_EPOLL_CLOEXEC
 #cmakedefine ZMQ_USE_DEVPOLL
 #cmakedefine ZMQ_USE_POLL
 #cmakedefine ZMQ_USE_SELECT

src/epoll.cpp

@@ -48,7 +48,14 @@ zmq::epoll_t::epoll_t (const zmq::ctx_t &ctx_) :
     ctx(ctx_),
     stopping (false)
 {
+#ifdef ZMQ_USE_EPOLL_CLOEXEC
+    //  Setting this option result in sane behaviour when exec() functions
+    //  are used. Old sockets are closed and don't block TCP ports, avoid
+    //  leaks, etc.
+    epoll_fd = epoll_create1 (EPOLL_CLOEXEC);
+#else
     epoll_fd = epoll_create (1);
+#endif
     errno_assert (epoll_fd != -1);
 }