Problem: zmq_connect fails after disconnect due to RECONNECT_IVL == -1

Solution: when a connection breaks and ZMQ_RECONNECT_IVL is set to -1,
which means a reconnection will not be attempted, send a message from
the I/O thread to the application thread to make the socket call
term_endpoint, which is the equivalent of manually calling
zmq_disconnect.
This way subsequent zmq_connect call to the same endpoint will attempt
again to do a connection.
Otherwise, for some socket types like SUBs, those new connects will
fail as the endpoint is recorded, despite the connection having been
permanently closed.

Add test cases to exercise this corner case with TCP and IPC.

.gitignore

@@ -139,6 +139,7 @@ test_base85
 test_bind_after_connect_tcp
 test_sodium
 test_zmq_poll_fd
+test_reconnect_ivl
 tests/test*.log
 tests/test*.trs
 src/platform.hpp*

Makefile.am

@@ -418,6 +418,7 @@ test_apps = \
 	tests/test_base85 \
 	tests/test_bind_after_connect_tcp \
 	tests/test_sodium \
+	tests/test_reconnect_ivl \
 	tests/test_socket_null
 
 tests_test_ancillaries_SOURCES = tests/test_ancillaries.cpp
@@ -638,6 +639,9 @@ tests_test_sodium_LDADD = src/libzmq.la
 tests_test_socket_null_SOURCES = tests/test_socket_null.cpp
 tests_test_socket_null_LDADD = src/libzmq.la
 
+tests_test_reconnect_ivl_SOURCES = tests/test_reconnect_ivl.cpp
+tests_test_reconnect_ivl_LDADD = src/libzmq.la
+
 if HAVE_CURVE
 
 test_apps += \

src/command.hpp

@@ -30,6 +30,7 @@
 #ifndef __ZMQ_COMMAND_HPP_INCLUDED__
 #define __ZMQ_COMMAND_HPP_INCLUDED__
 
+#include <string>
 #include "stdint.hpp"
 
 namespace zmq
@@ -69,6 +70,7 @@ namespace zmq
             term_req,
             term,
             term_ack,
+            term_endpoint,
             reap,
             reaped,
             inproc_connected,
@@ -153,6 +155,12 @@ namespace zmq
             struct {
             } term_ack;
 
+            //  Sent by session_base (I/O thread) to socket (application thread)
+            //  to ask to disconnect the endpoint.
+            struct {
+                std::string *endpoint;
+            } term_endpoint;
+
             //  Transfers the ownership of the closed socket
             //  to the reaper thread.
             struct {

src/object.cpp

@@ -134,6 +134,10 @@ void zmq::object_t::process_command (command_t &cmd_)
         process_term_ack ();
         break;
 
+    case command_t::term_endpoint:
+        process_term_endpoint (cmd_.args.term_endpoint.endpoint);
+        break;
+
     case command_t::reap:
         process_reap (cmd_.args.reap.socket);
         break;
@@ -332,6 +336,16 @@ void zmq::object_t::send_term_ack (own_t *destination_)
     send_command (cmd);
 }
 
+void zmq::object_t::send_term_endpoint (own_t *destination_,
+        std::string *endpoint_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::term_endpoint;
+    cmd.args.term_endpoint.endpoint = endpoint_;
+    send_command (cmd);
+}
+
 void zmq::object_t::send_reap (class socket_base_t *socket_)
 {
     command_t cmd;
@@ -435,6 +449,11 @@ void zmq::object_t::process_term_ack ()
     zmq_assert (false);
 }
 
+void zmq::object_t::process_term_endpoint (std::string *)
+{
+    zmq_assert (false);
+}
+
 void zmq::object_t::process_reap (class socket_base_t *)
 {
     zmq_assert (false);

src/object.hpp

@@ -107,6 +107,7 @@ namespace zmq
             zmq::own_t *object_);
         void send_term (zmq::own_t *destination_, int linger_);
         void send_term_ack (zmq::own_t *destination_);
+        void send_term_endpoint (own_t *destination_, std::string *endpoint_);
         void send_reap (zmq::socket_base_t *socket_);
         void send_reaped ();
         void send_done ();
@@ -127,6 +128,7 @@ namespace zmq
         virtual void process_term_req (zmq::own_t *object_);
         virtual void process_term (int linger_);
         virtual void process_term_ack ();
+        virtual void process_term_endpoint (std::string *endpoint_);
         virtual void process_reap (zmq::socket_base_t *socket_);
         virtual void process_reaped ();
 

src/session_base.cpp

@@ -536,6 +536,11 @@ void zmq::session_base_t::reconnect ()
     //  Reconnect.
     if (options.reconnect_ivl != -1)
         start_connecting (true);
+    else {
+        std::string *ep = new (std::string);
+        addr->to_string (*ep);
+        send_term_endpoint (socket, ep);
+    }
 
     //  For subscriber sockets we hiccup the inbound pipe, which will cause
     //  the socket object to resend all the subscriptions.

src/socket_base.cpp

@@ -1425,6 +1425,12 @@ void zmq::socket_base_t::process_term (int linger_)
     own_t::process_term (linger_);
 }
 
+void zmq::socket_base_t::process_term_endpoint (std::string *endpoint_)
+{
+    term_endpoint (endpoint_->c_str());
+    delete endpoint_;
+}
+
 void zmq::socket_base_t::update_pipe_options(int option_)
 {
     if (option_ == ZMQ_SNDHWM || option_ == ZMQ_RCVHWM)

src/socket_base.hpp

@@ -250,6 +250,7 @@ namespace zmq
         void process_stop ();
         void process_bind (zmq::pipe_t *pipe_);
         void process_term (int linger_);
+        void process_term_endpoint (std::string *endpoint_);
 
         void update_pipe_options(int option_);
 

tests/CMakeLists.txt

@@ -70,6 +70,7 @@ set(tests
         test_sodium
         test_monitor
 		test_socket_null
+	test_reconnect_ivl
 )
 if(ZMQ_HAVE_CURVE)
   list(APPEND tests 

tests/test_reconnect_ivl.cpp

+/*
+    Copyright (c) 2017 Contributors as noted in the AUTHORS file
+
+    This file is part of libzmq, the ZeroMQ core engine in C++.
+
+    libzmq is free software; you can redistribute it and/or modify it under
+    the terms of the GNU Lesser General Public License (LGPL) as published
+    by the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    As a special exception, the Contributors give you permission to link
+    this library with independent modules to produce an executable,
+    regardless of the license terms of these independent modules, and to
+    copy and distribute the resulting executable under terms of your choice,
+    provided that you also meet, for each linked independent module, the
+    terms and conditions of the license of that module. An independent
+    module is a module which is not derived from or based on this library.
+    If you modify this library, you must extend this exception to your
+    version of the library.
+
+    libzmq is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+    License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "testutil.hpp"
+
+
+#ifndef ZMQ_HAVE_WINDOWS
+void test_reconnect_ivl_ipc (void)
+{
+    void *ctx = zmq_ctx_new ();
+    assert (ctx);
+
+    void *sb = zmq_socket (ctx, ZMQ_PAIR);
+    assert (sb);
+    int rc = zmq_bind (sb, "ipc:///tmp/test_reconnect_ivl");
+    assert (rc == 0);
+
+    void *sc = zmq_socket (ctx, ZMQ_PAIR);
+    assert (sc);
+    int interval = -1;
+    rc = zmq_setsockopt (sc, ZMQ_RECONNECT_IVL, &interval, sizeof (int));
+    assert (rc == 0);
+    rc = zmq_connect (sc, "ipc:///tmp/test_reconnect_ivl");
+    assert (rc == 0);
+
+    bounce (sb, sc);
+
+    rc = zmq_unbind (sb, "ipc:///tmp/test_reconnect_ivl");
+    assert (rc == 0);
+
+    expect_bounce_fail (sb, sc);
+
+    rc = zmq_bind (sb, "ipc:///tmp/test_reconnect_ivl");
+    assert (rc == 0);
+
+    expect_bounce_fail (sb, sc);
+
+    rc = zmq_connect (sc, "ipc:///tmp/test_reconnect_ivl");
+    assert (rc == 0);
+
+    bounce (sb, sc);
+
+    rc = zmq_close (sc);
+    assert (rc == 0);
+
+    rc = zmq_close (sb);
+    assert (rc == 0);
+
+    rc = zmq_ctx_term (ctx);
+    assert (rc == 0);
+}
+#endif
+
+void test_reconnect_ivl_tcp (const char *address)
+{
+    size_t len = MAX_SOCKET_STRING;
+    char my_endpoint[MAX_SOCKET_STRING];
+    void *ctx = zmq_ctx_new ();
+    assert (ctx);
+
+    if (streq (address, "tcp://[::1]:*")) {
+        if (is_ipv6_available ()) {
+            zmq_ctx_set(ctx, ZMQ_IPV6, 1);
+        } else {
+            zmq_ctx_term (ctx);
+            return;
+        }
+    }
+
+    void *sb = zmq_socket (ctx, ZMQ_PAIR);
+    assert (sb);
+    int rc = zmq_bind (sb, address);
+    assert (rc == 0);
+    rc = zmq_getsockopt (sb, ZMQ_LAST_ENDPOINT, my_endpoint, &len);
+    assert (rc == 0);
+
+    void *sc = zmq_socket (ctx, ZMQ_PAIR);
+    assert (sc);
+    int interval = -1;
+    rc = zmq_setsockopt (sc, ZMQ_RECONNECT_IVL, &interval, sizeof (int));
+    assert (rc == 0);
+    rc = zmq_connect (sc, my_endpoint);
+    assert (rc == 0);
+
+    bounce (sb, sc);
+
+    rc = zmq_unbind (sb, my_endpoint);
+    assert (rc == 0);
+
+    expect_bounce_fail (sb, sc);
+
+    rc = zmq_bind (sb, my_endpoint);
+    assert (rc == 0);
+
+    expect_bounce_fail (sb, sc);
+
+    rc = zmq_connect (sc, my_endpoint);
+    assert (rc == 0);
+
+    bounce (sb, sc);
+
+    rc = zmq_close (sc);
+    assert (rc == 0);
+
+    rc = zmq_close (sb);
+    assert (rc == 0);
+
+    rc = zmq_ctx_term (ctx);
+    assert (rc == 0);
+}
+
+int main (void)
+{
+    setup_test_environment ();
+
+#ifndef ZMQ_HAVE_WINDOWS
+    test_reconnect_ivl_ipc ();
+#endif
+    test_reconnect_ivl_tcp ("tcp://127.0.0.1:*");
+    test_reconnect_ivl_tcp ("tcp://[::1]:*");
+
+    return 0 ;
+}