Close file descriptors on exec (issue 218)

When exec is executed to start a different process image old
0MQ file descriptors could stay open, thus blocking TCP ports
and alike. This patch should solve the problem.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

src/ip.cpp

@@ -36,6 +36,29 @@
 #include <ioctl.h>
 #endif
 
+zmq::fd_t zmq::open_socket (int domain_, int type_, int protocol_)
+{
+    //  Setting this option result in sane behaviour when exec() functions
+    //  are used. Old sockets are closed and don't block TCP ports etc.
+#if defined SOCK_CLOEXEC
+    type_ |= SOCK_CLOEXEC;
+#endif
+
+    fd_t s = socket (domain_, type_, protocol_);
+    if (s == retired_fd)
+        return retired_fd;
+
+    //  If there's no SOCK_CLOEXEC, let's try the second best option. Note that
+    //  race condition can cause socket not to be closed (if fork happens
+    //  between socket creation and this point).
+#if !defined SOCK_CLOEXEC && defined FD_CLOEXEC
+    int rc = fcntl (s, F_SETFD, FD_CLOEXEC);
+    errno_assert (rc != -1);
+#endif
+
+    return s;
+}
+
 void zmq::tune_tcp_socket (fd_t s_)
 {
     //  Disable Nagle's algorithm. We are doing data batching on 0MQ level,

src/ip.hpp

@@ -26,6 +26,9 @@
 namespace zmq
 {
 
+    //  Same as socket(2), but allows for transparent tweaking the options.
+    fd_t open_socket (int domain_, int type_, int protocol_);
+
     //  Tunes the supplied TCP socket for the best latency.
     void tune_tcp_socket (fd_t s_);
 

src/ipc_connecter.cpp

@@ -174,7 +174,7 @@ int zmq::ipc_connecter_t::open ()
     zmq_assert (s == retired_fd);
 
     //  Create the socket.
-    s = socket (AF_UNIX, SOCK_STREAM, 0);
+    s = open_socket (AF_UNIX, SOCK_STREAM, 0);
     if (s == -1)
         return -1;
 

src/ipc_listener.cpp

@@ -32,6 +32,7 @@
 #include "session.hpp"
 #include "config.hpp"
 #include "err.hpp"
+#include "ip.hpp"
 
 #include <unistd.h>
 #include <sys/socket.h>
@@ -108,7 +109,7 @@ int zmq::ipc_listener_t::set_address (const char *addr_)
         return -1;
 
     //  Create a listening socket.
-    s = ::socket (AF_UNIX, SOCK_STREAM, 0);
+    s = open_socket (AF_UNIX, SOCK_STREAM, 0);
     if (s == -1)
         return -1;
 

src/signaler.cpp

@@ -240,7 +240,7 @@ int zmq::signaler_t::make_fdpair (fd_t *r_, fd_t *w_)
 
     //  Create listening socket.
     SOCKET listener;
-    listener = socket (AF_INET, SOCK_STREAM, 0);
+    listener = open_socket (AF_INET, SOCK_STREAM, 0);
     wsa_assert (listener != INVALID_SOCKET);
 
     //  Set SO_REUSEADDR and TCP_NODELAY on listening socket.
@@ -308,7 +308,7 @@ int zmq::signaler_t::make_fdpair (fd_t *r_, fd_t *w_)
     lcladdr.sin_addr.s_addr = htonl (INADDR_LOOPBACK);
     lcladdr.sin_port = 0;
 
-    int listener = socket (AF_INET, SOCK_STREAM, 0);
+    int listener = open_socket (AF_INET, SOCK_STREAM, 0);
     errno_assert (listener != -1);
 
     int on = 1;
@@ -329,7 +329,7 @@ int zmq::signaler_t::make_fdpair (fd_t *r_, fd_t *w_)
     rc = listen (listener, 1);
     errno_assert (rc != -1);
 
-    *w_ = socket (AF_INET, SOCK_STREAM, 0);
+    *w_ = open_socket (AF_INET, SOCK_STREAM, 0);
     errno_assert (*w_ != -1);
 
     rc = setsockopt (*w_, IPPROTO_TCP, TCP_NODELAY, &on, sizeof (on));

src/tcp_address.cpp

@@ -25,6 +25,7 @@
 #include "platform.hpp"
 #include "stdint.hpp"
 #include "err.hpp"
+#include "ip.hpp"
 
 #ifdef ZMQ_HAVE_WINDOWS
 #include "windows.hpp"
@@ -56,7 +57,7 @@ int zmq::tcp_address_t::resolve_nic_name (const char *nic_, bool ipv4only_)
     (void) ipv4only_;
 
     //  Create a socket.
-    int fd = socket (AF_INET, SOCK_DGRAM, 0);
+    int fd = open_socket (AF_INET, SOCK_DGRAM, 0);
     zmq_assert (fd != -1);
 
     //  Retrieve number of interfaces.
@@ -121,7 +122,7 @@ int zmq::tcp_address_t::resolve_nic_name (const char *nic_, bool ipv4only_)
     (void) ipv4only_;
 
     //  Create a socket.
-    int sd = socket (AF_INET, SOCK_DGRAM, 0);
+    int sd = open_socket (AF_INET, SOCK_DGRAM, 0);
     zmq_assert (sd != -1);
 
     struct ifreq ifr; 

src/tcp_connecter.cpp

@@ -184,7 +184,7 @@ int zmq::tcp_connecter_t::open ()
     zmq_assert (s == retired_fd);
 
     //  Create the socket.
-    s = socket (address.family (), SOCK_STREAM, IPPROTO_TCP);
+    s = open_socket (address.family (), SOCK_STREAM, IPPROTO_TCP);
 #ifdef ZMQ_HAVE_WINDOWS
     if (s == INVALID_SOCKET) {
         wsa_error_to_errno ();

src/tcp_listener.cpp

@@ -126,7 +126,7 @@ int zmq::tcp_listener_t::set_address (const char *addr_)
         return -1;
 
     //  Create a listening socket.
-    s = ::socket (address.family (), SOCK_STREAM, IPPROTO_TCP);
+    s = open_socket (address.family (), SOCK_STREAM, IPPROTO_TCP);
 #ifdef ZMQ_HAVE_WINDOWS
     if (s == INVALID_SOCKET)
         wsa_error_to_errno ();