Tuning of TCP sockets is done at a single place

Instead of being spread throughout the codebase, the tuning
is done in tune_tcp_socket() function.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

src/ip.cpp

@@ -344,3 +344,27 @@ int zmq::resolve_local_path (sockaddr_storage *addr_, socklen_t *addr_len_,
 #endif
 }
 
+void zmq::tune_tcp_socket (fd_t s_)
+{
+    //  Disable Nagle's algorithm. We are doing data batching on 0MQ level,
+    //  so using Nagle wouldn't improve throughput in anyway, but it would
+    //  hurt latency.
+    int nodelay = 1;
+    int rc = setsockopt (s_, IPPROTO_TCP, TCP_NODELAY, (char*) &nodelay,
+        sizeof (int));
+#ifdef ZMQ_HAVE_WINDOWS
+    wsa_assert (rc != SOCKET_ERROR);
+#else
+    errno_assert (rc == 0);
+#endif
+
+#ifdef ZMQ_HAVE_OPENVMS
+    //  Disable delayed acknowledgements as they hurt latency is serious manner.
+    int nodelack = 1;
+    rc = setsockopt (s_, IPPROTO_TCP, TCP_NODELACK, (char*) &nodelack,
+        sizeof (int));
+    errno_assert (rc != SOCKET_ERROR);
+#endif
+}
+
+

src/ip.hpp

@@ -22,6 +22,7 @@
 #define __ZMQ_IP_HPP_INCLUDED__
 
 #include "platform.hpp"
+#include "fd.hpp"
 
 #ifdef ZMQ_HAVE_WINDOWS
 #include "windows.hpp"
@@ -30,6 +31,7 @@
 #include <sys/socket.h>
 #include <arpa/inet.h>
 #include <netinet/in.h>
+#include <netinet/tcp.h>
 #include <netdb.h>
 #endif
 
@@ -63,6 +65,9 @@ namespace zmq
     //  This function sets up address for UNIX domain transport.
     int resolve_local_path (sockaddr_storage *addr_, socklen_t *addr_len_,
         const char* pathname_);
+
+    //  Tunes the supplied TCP socket for the best latency.
+    void tune_tcp_socket (fd_t s_);
 }
 
 #endif 

src/tcp_connecter.cpp

@@ -26,8 +26,8 @@
 #include "io_thread.hpp"
 #include "platform.hpp"
 #include "random.hpp"
-#include "ip.hpp"
 #include "err.hpp"
+#include "ip.hpp"
 
 #if defined ZMQ_HAVE_WINDOWS
 #include "windows.hpp"
@@ -106,25 +106,7 @@ void zmq::tcp_connecter_t::out_event ()
         return;
     }
 
-    //  Disable Nagle's algorithm. We are doing data batching on 0MQ level,
-    //  so using Nagle wouldn't improve throughput in anyway, but it would
-    //  hurt latency.
-    int nodelay = 1;
-    int rc = setsockopt (fd, IPPROTO_TCP, TCP_NODELAY, (char*) &nodelay,
-        sizeof (int));
-#ifdef ZMQ_HAVE_WINDOWS
-    wsa_assert (rc != SOCKET_ERROR);
-#else
-    errno_assert (rc == 0);
-#endif
-
-#ifdef ZMQ_HAVE_OPENVMS
-    //  Disable delayed acknowledgements as they hurt latency is serious manner.
-    int nodelack = 1;
-    rc = setsockopt (fd, IPPROTO_TCP, TCP_NODELACK, (char*) &nodelack,
-        sizeof (int));
-    errno_assert (rc != SOCKET_ERROR);
-#endif
+    tune_tcp_socket (fd);
 
     //  Create the engine object for this connection.
     tcp_engine_t *engine = new (std::nothrow) tcp_engine_t (fd, options);

src/tcp_listener.cpp

@@ -29,6 +29,7 @@
 #include "session.hpp"
 #include "config.hpp"
 #include "err.hpp"
+#include "ip.hpp"
 
 #ifdef ZMQ_HAVE_WINDOWS
 #include "windows.hpp"
@@ -86,25 +87,7 @@ void zmq::tcp_listener_t::in_event ()
     if (fd == retired_fd)
         return;
 
-    //  Disable Nagle's algorithm. We are doing data batching on 0MQ level,
-    //  so using Nagle wouldn't improve throughput in anyway, but it would
-    //  hurt latency.
-    int nodelay = 1;
-    int rc = setsockopt (fd, IPPROTO_TCP, TCP_NODELAY, (char*) &nodelay,
-        sizeof (int));
-#ifdef ZMQ_HAVE_WINDOWS
-    wsa_assert (rc != SOCKET_ERROR);
-#else
-    errno_assert (rc == 0);
-#endif
-
-#ifdef ZMQ_HAVE_OPENVMS
-    //  Disable delayed acknowledgements as they hurt latency is serious manner.
-    int nodelack = 1;
-    rc = setsockopt (fd, IPPROTO_TCP, TCP_NODELACK, (char*) &nodelack,
-        sizeof (int));
-    errno_assert (rc != SOCKET_ERROR);
-#endif
+    tune_tcp_socket (fd);
 
     //  Create the engine object for this connection.
     tcp_engine_t *engine = new (std::nothrow) tcp_engine_t (fd, options);

src/vtcp_connecter.cpp

@@ -30,8 +30,8 @@
 #include "platform.hpp"
 #include "random.hpp"
 #include "likely.hpp"
-#include "ip.hpp"
 #include "err.hpp"
+#include "ip.hpp"
 
 #if defined ZMQ_HAVE_WINDOWS
 #include "windows.hpp"
@@ -220,6 +220,8 @@ zmq::fd_t zmq::vtcp_connecter_t::connect ()
         return retired_fd;
     }
 
+    tune_tcp_socket (s);
+
     fd_t result = s;
     s = retired_fd;
     return result;

src/vtcp_listener.cpp

@@ -30,6 +30,7 @@
 #include "session.hpp"
 #include "stdint.hpp"
 #include "err.hpp"
+#include "ip.hpp"
 
 zmq::vtcp_listener_t::vtcp_listener_t (io_thread_t *io_thread_,
         socket_base_t *socket_, options_t &options_) :
@@ -95,6 +96,8 @@ void zmq::vtcp_listener_t::in_event ()
     if (fd == retired_fd)
         return;
 
+    tune_tcp_socket (fd);
+
     //  Create the engine object for this connection.
     tcp_engine_t *engine = new (std::nothrow) tcp_engine_t (fd, options);
     alloc_assert (engine);