Problem: lingering subscriptions on XPUB sockets (#1566)

The patch fixes lingering subscriptions that occur upon disconnection
on XPUB sockets with option XPUB_MANUAL when used in a XPUB-XSUB
proxies.

src/xpub.cpp

@@ -153,11 +153,17 @@ int zmq::xpub_t::xsetsockopt (int option_, const void *optval_,
             manual = (*static_cast <const int*> (optval_) != 0);
     }
     else
-    if (option_ == ZMQ_SUBSCRIBE && manual && last_pipe != NULL)
-        subscriptions.add((unsigned char *)optval_, optvallen_, last_pipe);
+    if (option_ == ZMQ_SUBSCRIBE && manual) {
+        if (last_pipe != NULL) {
+            subscriptions.add((unsigned char *)optval_, optvallen_, last_pipe);
+        }
+    }
     else
-    if (option_ == ZMQ_UNSUBSCRIBE && manual && last_pipe != NULL)
-        subscriptions.rm((unsigned char *)optval_, optvallen_, last_pipe);
+    if (option_ == ZMQ_UNSUBSCRIBE && manual) {
+        if (last_pipe != NULL) {
+            subscriptions.rm((unsigned char *)optval_, optvallen_, last_pipe);
+        }
+    }
     else
     if (option_ == ZMQ_XPUB_WELCOME_MSG) {
         welcome_msg.close();
@@ -183,7 +189,7 @@ void zmq::xpub_t::xpipe_terminated (pipe_t *pipe_)
     //  Remove the pipe from the trie. If there are topics that nobody
     //  is interested in anymore, send corresponding unsubscriptions
     //  upstream.
-    subscriptions.rm (pipe_, send_unsubscription, this, !verbose_unsubs);
+    subscriptions.rm (pipe_, send_unsubscription, this, !(verbose_unsubs || manual));
 
     dist.pipe_terminated (pipe_);
 }
@@ -274,6 +280,7 @@ void zmq::xpub_t::send_unsubscription (unsigned char *data_, size_t size_,
         unsub [0] = 0;
         if (size_ > 0)
             memcpy (&unsub [1], data_, size_);
+        self->last_pipe = NULL;
         self->pending_data.push_back (unsub);
         self->pending_metadata.push_back (NULL);
         self->pending_flags.push_back (0);

tests/test_xpub_manual.cpp

@@ -29,9 +29,8 @@
 
 #include "testutil.hpp"
 
-int main (void)
+int test_basic()
 {
-    setup_test_environment();
     void *ctx = zmq_ctx_new ();
     assert (ctx);
 
@@ -90,3 +89,150 @@ int main (void)
 
     return 0 ;
 }
+
+int test_xpub_proxy_unsubscribe_on_disconnect()
+{
+    const char* frontend = "ipc://frontend";
+    const char* backend = "ipc://backend";
+    const char* topic = "1";
+    const char* payload = "X";
+
+    int manual = 1;
+
+    void *ctx = zmq_ctx_new ();
+    assert (ctx);
+
+    // proxy frontend
+    void *xsub_proxy = zmq_socket (ctx, ZMQ_XSUB);
+    assert (xsub_proxy);
+    assert (zmq_bind (xsub_proxy, frontend) == 0);
+
+    // proxy backend
+    void *xpub_proxy = zmq_socket (ctx, ZMQ_XPUB);
+    assert (xpub_proxy);
+    assert (zmq_setsockopt (xpub_proxy, ZMQ_XPUB_MANUAL, &manual, 4) == 0);
+    assert (zmq_bind (xpub_proxy, backend) == 0);
+
+    // publisher
+    void *pub = zmq_socket (ctx, ZMQ_PUB);
+    assert (zmq_connect (pub, frontend) == 0);
+
+    // first subscriber subscribes
+    void *sub1 = zmq_socket (ctx, ZMQ_SUB);
+    assert (sub1);
+    assert (zmq_connect (sub1, backend) == 0);
+    assert (zmq_setsockopt (sub1, ZMQ_SUBSCRIBE, topic, 1) == 0);
+
+    // wait
+    assert (zmq_poll (0, 0, 100) == 0);
+
+    // proxy reroutes and confirms subscriptions
+    char sub_buff[2];
+    assert (zmq_recv (xpub_proxy, sub_buff, 2, ZMQ_DONTWAIT) == 2);
+    assert (sub_buff [0] == 1);
+    assert (sub_buff [1] == *topic);
+    assert (zmq_setsockopt (xpub_proxy, ZMQ_SUBSCRIBE, topic, 1) == 0);
+    assert (zmq_send (xsub_proxy, sub_buff, 2, 0) == 2);
+
+    // second subscriber subscribes
+    void *sub2 = zmq_socket (ctx, ZMQ_SUB);
+    assert (sub2);
+    assert (zmq_connect (sub2, backend) == 0);
+    assert (zmq_setsockopt (sub2, ZMQ_SUBSCRIBE, topic, 1) == 0);
+
+    // wait
+    assert (zmq_poll (0, 0, 100) == 0);
+
+    // proxy reroutes
+    assert (zmq_recv (xpub_proxy, sub_buff, 2, ZMQ_DONTWAIT) == 2);
+    assert (sub_buff [0] == 1);
+    assert (sub_buff [1] == *topic);
+    assert (zmq_setsockopt (xpub_proxy, ZMQ_SUBSCRIBE, topic, 1) == 0);
+    assert (zmq_send (xsub_proxy, sub_buff, 2, 0) == 2);
+
+    // wait
+    assert (zmq_poll (0, 0, 100) == 0);
+
+    // let publisher send a msg
+    assert (zmq_send (pub, topic, 1, ZMQ_SNDMORE) == 1);
+    assert (zmq_send (pub, payload, 1, 0) == 1);
+
+    // wait
+    assert (zmq_poll (0, 0, 100) == 0);
+
+    // proxy reroutes data messages to subscribers
+    char topic_buff[1];
+    char data_buff[1];
+    assert (zmq_recv (xsub_proxy, topic_buff, 1, ZMQ_DONTWAIT) == 1);
+    assert (topic_buff [0] == *topic);
+    assert (zmq_recv (xsub_proxy, data_buff, 1, ZMQ_DONTWAIT) == 1);
+    assert (data_buff [0] == *payload);
+    assert (zmq_send (xpub_proxy, topic_buff, 1, ZMQ_SNDMORE) == 1);
+    assert (zmq_send (xpub_proxy, data_buff, 1, 0) == 1);
+
+    // wait
+    assert (zmq_poll (0, 0, 100) == 0);
+
+    // each subscriber should now get a message
+    assert (zmq_recv (sub2, topic_buff, 1, ZMQ_DONTWAIT) == 1);
+    assert (topic_buff [0] == *topic);
+    assert (zmq_recv (sub2, data_buff, 1, ZMQ_DONTWAIT) == 1);
+    assert (data_buff [0] == *payload);
+
+    assert (zmq_recv (sub1, topic_buff, 1, ZMQ_DONTWAIT) == 1);
+    assert (topic_buff [0] == *topic);
+    assert (zmq_recv (sub1, data_buff, 1, ZMQ_DONTWAIT) == 1);
+    assert (data_buff [0] == *payload);
+
+    //  Disconnect both subscribers
+    assert (zmq_close (sub1) == 0);
+    assert (zmq_close (sub2) == 0);
+
+    // wait
+    assert (zmq_poll (0, 0, 100) == 0);
+
+    // unsubscribe messages are passed from proxy to publisher
+    assert (zmq_recv (xpub_proxy, sub_buff, 2, 0) == 2);
+    assert (sub_buff [0] == 0);
+    assert (sub_buff [1] == *topic);
+    assert (zmq_setsockopt (xpub_proxy, ZMQ_UNSUBSCRIBE, topic, 1) == 0);
+    assert (zmq_send (xsub_proxy, sub_buff, 2, 0) == 2);
+
+    // should receive another unsubscribe msg
+    assert (zmq_recv (xpub_proxy, sub_buff, 2, ZMQ_DONTWAIT) == 2
+        && "Should receive the second unsubscribe message.");
+    assert (sub_buff [0] == 0);
+    assert (sub_buff [1] == *topic);
+    assert (zmq_setsockopt (xpub_proxy, ZMQ_UNSUBSCRIBE, topic, 1) == 0);
+    assert (zmq_send (xsub_proxy, sub_buff, 2, 0) == 2);
+
+    // wait
+    assert (zmq_poll (0, 0, 100) == 0);
+
+    // let publisher send a msg
+    assert (zmq_send (pub, topic, 1, ZMQ_SNDMORE) == 1);
+    assert (zmq_send (pub, payload, 1, 0) == 1);
+
+     // wait
+    assert (zmq_poll (0, 0, 100) == 0);
+
+    // nothing should come to the proxy
+    assert (zmq_recv (xsub_proxy, topic_buff, 1, ZMQ_DONTWAIT) == -1);
+    assert (errno == EAGAIN);
+
+    assert (zmq_close (pub) == 0);
+    assert (zmq_close (xpub_proxy) == 0);
+    assert (zmq_close (xsub_proxy) == 0);
+    assert (zmq_ctx_term (ctx) == 0);
+
+    return 0;
+}
+
+int main(void)
+{
+    setup_test_environment ();
+    test_basic ();
+    test_xpub_proxy_unsubscribe_on_disconnect ();
+
+    return 0;
+}