Problem: socks_connecter_t duplicates code around opening and configuring a TCP socket

Solution: use tcp_open_socket function

src/socks_connecter.cpp

@@ -215,49 +215,26 @@ int zmq::socks_connecter_t::connect_to_proxy ()
     zmq_assert (_s == retired_fd);
 
     //  Resolve the address
-    LIBZMQ_DELETE (_proxy_addr->resolved.tcp_addr);
-    _proxy_addr->resolved.tcp_addr = new (std::nothrow) tcp_address_t ();
-    alloc_assert (_proxy_addr->resolved.tcp_addr);
+    if (_addr->resolved.tcp_addr != NULL) {
+        LIBZMQ_DELETE (_addr->resolved.tcp_addr);
+    }
 
-    int rc = _proxy_addr->resolved.tcp_addr->resolve (
-      _proxy_addr->address.c_str (), false, options.ipv6);
-    if (rc != 0) {
-        LIBZMQ_DELETE (_proxy_addr->resolved.tcp_addr);
+    _addr->resolved.tcp_addr = new (std::nothrow) tcp_address_t ();
+    alloc_assert (_addr->resolved.tcp_addr);
+    //  Automatic fallback to ipv4 is disabled here since this was the existing
+    //  behaviour, however I don't see a real reason for this. Maybe this can
+    //  be changed to true (and then the parameter can be removed entirely).
+    _s = tcp_open_socket (_addr->address.c_str (), options, false,
+                          _addr->resolved.tcp_addr);
+    if (_s == retired_fd) {
+        LIBZMQ_DELETE (_addr->resolved.tcp_addr);
         return -1;
     }
-    zmq_assert (_proxy_addr->resolved.tcp_addr != NULL);
-    const tcp_address_t *tcp_addr = _proxy_addr->resolved.tcp_addr;
+    zmq_assert (_addr->resolved.tcp_addr != NULL);
 
-    //  Create the socket.
-    _s = open_socket (tcp_addr->family (), SOCK_STREAM, IPPROTO_TCP);
-    if (_s == retired_fd)
-        return -1;
+    const tcp_address_t *const tcp_addr = _addr->resolved.tcp_addr;
 
-    //  On some systems, IPv4 mapping in IPv6 sockets is disabled by default.
-    //  Switch it on in such cases.
-    if (tcp_addr->family () == AF_INET6)
-        enable_ipv4_mapping (_s);
-
-    // Set the IP Type-Of-Service priority for this socket
-    if (options.tos != 0)
-        set_ip_type_of_service (_s, options.tos);
-
-    // Bind the socket to a device if applicable
-    if (!options.bound_device.empty ())
-        bind_to_device (_s, options.bound_device);
-
-    // Set the socket to non-blocking mode so that we get async connect().
-    unblock_socket (_s);
-
-    //  Set the socket buffer limits for the underlying socket.
-    if (options.sndbuf >= 0)
-        set_tcp_send_buffer (_s, options.sndbuf);
-    if (options.rcvbuf >= 0)
-        set_tcp_receive_buffer (_s, options.rcvbuf);
-
-    // Set the IP Type-Of-Service for the underlying socket
-    if (options.tos != 0)
-        set_ip_type_of_service (_s, options.tos);
+    int rc;
 
     // Set a source address for conversations
     if (tcp_addr->has_src_addr ()) {

src/tcp.cpp

@@ -385,6 +385,7 @@ void zmq::tcp_tune_loopback_fast_path (const fd_t socket_)
 
 zmq::fd_t zmq::tcp_open_socket (const char *address_,
                                 const zmq::options_t &options_,
+                                bool fallback_to_ipv4_,
                                 zmq::tcp_address_t *out_tcp_addr_)
 {
     //  Convert the textual address into address structure.
@@ -396,8 +397,9 @@ zmq::fd_t zmq::tcp_open_socket (const char *address_,
     fd_t s = open_socket (out_tcp_addr_->family (), SOCK_STREAM, IPPROTO_TCP);
 
     //  IPv6 address family not supported, try automatic downgrade to IPv4.
-    if (s == retired_fd && out_tcp_addr_->family () == AF_INET6
-        && errno == EAFNOSUPPORT && options_.ipv6) {
+    if (s == retired_fd && fallback_to_ipv4_
+        && out_tcp_addr_->family () == AF_INET6 && errno == EAFNOSUPPORT
+        && options_.ipv6) {
         rc = out_tcp_addr_->resolve (address_, false, false);
         if (rc != 0) {
             return retired_fd;

src/tcp.hpp

@@ -79,6 +79,7 @@ void tcp_tune_loopback_fast_path (const fd_t socket_);
 //  errno is set to an error code describing the cause of the error.
 fd_t tcp_open_socket (const char *address_,
                       const options_t &options_,
+                      bool fallback_to_ipv4_,
                       tcp_address_t *out_tcp_addr_);
 }
 

src/tcp_connecter.cpp

@@ -174,7 +174,7 @@ int zmq::tcp_connecter_t::open ()
 
     _addr->resolved.tcp_addr = new (std::nothrow) tcp_address_t ();
     alloc_assert (_addr->resolved.tcp_addr);
-    _s = tcp_open_socket (_addr->address.c_str (), options,
+    _s = tcp_open_socket (_addr->address.c_str (), options, true,
                           _addr->resolved.tcp_addr);
     if (_s == retired_fd) {
         LIBZMQ_DELETE (_addr->resolved.tcp_addr);

src/tcp_listener.cpp

@@ -103,7 +103,7 @@ zmq::tcp_listener_t::get_socket_name (zmq::fd_t fd_,
 
 int zmq::tcp_listener_t::create_socket (const char *addr_)
 {
-    _s = tcp_open_socket (addr_, options, &_address);
+    _s = tcp_open_socket (addr_, options, true, &_address);
     if (_s == retired_fd) {
         return -1;
     }