LIBZMQ-195 allow explicitly setting sndbuf and rcvbuf to 0 (see…

LIBZMQ-195 allow explicitly setting sndbuf and rcvbuf to 0 (see https://support.microsoft.com/en-us/kb/201213)

src/options.cpp

@@ -41,8 +41,8 @@ zmq::options_t::options_t () :
     rate (100),
     recovery_ivl (10000),
     multicast_hops (1),
-    sndbuf (0),
-    rcvbuf (0),
+    sndbuf (-1),
+    rcvbuf (-1),
     tos (0),
     type (-1),
     linger (-1),

src/pgm_socket.cpp

@@ -196,14 +196,14 @@ int zmq::pgm_socket_t::init (bool udp_encapsulation_, const char *network_)
 
     {
 		const int rcvbuf = (int) options.rcvbuf;
-		if (rcvbuf) {
+		if (rcvbuf >= 0) {
 		    if (!pgm_setsockopt (sock, SOL_SOCKET, SO_RCVBUF, &rcvbuf,
 		          sizeof (rcvbuf)))
 		        goto err_abort;
 		}
 
 		const int sndbuf = (int) options.sndbuf;
-		if (sndbuf) {
+		if (sndbuf >= 0) {
 		    if (!pgm_setsockopt (sock, SOL_SOCKET, SO_SNDBUF, &sndbuf,
 		          sizeof (sndbuf)))
 		        goto err_abort;

src/socks_connecter.cpp

@@ -340,9 +340,9 @@ int zmq::socks_connecter_t::connect_to_proxy ()
     unblock_socket (s);
 
     //  Set the socket buffer limits for the underlying socket.
-    if (options.sndbuf != 0)
+    if (options.sndbuf >= 0)
         set_tcp_send_buffer (s, options.sndbuf);
-    if (options.rcvbuf != 0)
+    if (options.rcvbuf >= 0)
         set_tcp_receive_buffer (s, options.rcvbuf);
 
     // Set the IP Type-Of-Service for the underlying socket

src/tcp_connecter.cpp

@@ -258,9 +258,9 @@ int zmq::tcp_connecter_t::open ()
     unblock_socket (s);
 
     //  Set the socket buffer limits for the underlying socket.
-    if (options.sndbuf != 0)
+    if (options.sndbuf >= 0)
         set_tcp_send_buffer (s, options.sndbuf);
-    if (options.rcvbuf != 0)
+    if (options.rcvbuf >= 0)
         set_tcp_receive_buffer (s, options.rcvbuf);
 
     // Set the IP Type-Of-Service for the underlying socket

src/tcp_listener.cpp

@@ -207,9 +207,9 @@ int zmq::tcp_listener_t::set_address (const char *addr_)
         set_ip_type_of_service (s, options.tos);
 
     //  Set the socket buffer limits for the underlying socket.
-    if (options.sndbuf != 0)
+    if (options.sndbuf >= 0)
         set_tcp_send_buffer (s, options.sndbuf);
-    if (options.rcvbuf != 0)
+    if (options.rcvbuf >= 0)
         set_tcp_receive_buffer (s, options.rcvbuf);
 
     //  Allow reusing of the address.