Fix 1478: receive unsubscriptions in XPUB when verbose

Fixes not receiving unsubscription messages in XPUB socket with
ZMQ_XPUB_VERBOSE and using a XSUB-XPUB proxy in front.

This adds two modifications:

- It adds a new flag, ZMQ_XPUB_VERBOSE_UNSUBSCRIBE, to enable verbose
  unsubscription messages, necessary when using a XSUB/XPUB proxy.

- It adds a boolean switch to zmq::mtrie_t::rm () to control if the
  callback is invoked every time or only in the last removal. Necessary
  when a pipe is terminated and the verbose mode for unsubscriptions is
  enabled.

doc/zmq_setsockopt.txt

@@ -14,8 +14,9 @@ SYNOPSIS
 
 Caution: All options, with the exception of ZMQ_SUBSCRIBE, ZMQ_UNSUBSCRIBE,
 ZMQ_LINGER, ZMQ_ROUTER_HANDOVER, ZMQ_ROUTER_MANDATORY, ZMQ_PROBE_ROUTER,
-ZMQ_XPUB_VERBOSE, ZMQ_REQ_CORRELATE, ZMQ_REQ_RELAXED, ZMQ_SNDHWM
+ZMQ_XPUB_VERBOSE, ZMQ_XPUB_VERBOSE_UNSUBSCRIBE, ZMQ_REQ_CORRELATE,
-and ZMQ_RCVHWM, only take effect for subsequent socket bind/connects.
+ZMQ_REQ_RELAXED, ZMQ_SNDHWM and ZMQ_RCVHWM, only take effect for
+subsequent socket bind/connects.
 
 Specifically, security options take effect for subsequent bind/connect calls,
 and can be changed at any time to affect subsequent binds and/or connects.
@@ -839,6 +840,25 @@ Default value:: 0
 Applicable socket types:: ZMQ_XPUB
 
 
+ZMQ_XPUB_VERBOSE_UNSUBSCRIBE: provide all unsubscription messages on XPUB sockets
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Sets the 'XPUB' socket behaviour on new subscriptions and unsubscriptions.
+A value of '0' is the default and passes only the last unsubscription message to
+upstream. A value of '1' passes all unsubscription messages upstream.
+
+This behaviour should be enabled in all the intermediary XPUB sockets if
+ZMQ_XPUB_VERBOSE is also being used in order to allow the correct forwarding
+of all the unsubscription messages.
+
+NOTE: This behaviour only takes effect when ZMQ_XPUB_VERBOSE is also enabled.
+
+[horizontal]
+Option value type:: int
+Option value unit:: 0, 1
+Default value:: 0
+Applicable socket types:: ZMQ_XPUB
+
+
 ZMQ_XPUB_MANUAL: change the subscription handling to manual
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Sets the 'XPUB' socket subscription handling mode manual/automatic.

include/zmq.h

@@ -319,6 +319,7 @@ ZMQ_EXPORT uint32_t zmq_msg_get_routing_id(zmq_msg_t *msg);
 #define ZMQ_HEARTBEAT_IVL 75
 #define ZMQ_HEARTBEAT_TTL 76
 #define ZMQ_HEARTBEAT_TIMEOUT 77
+#define ZMQ_XPUB_VERBOSE_UNSUBSCRIBE 78
 
 /*  Message options                                                           */
 #define ZMQ_MORE 1

src/mtrie.cpp

@@ -159,23 +159,28 @@ bool zmq::mtrie_t::add_helper (unsigned char *prefix_, size_t size_,
 
 void zmq::mtrie_t::rm (pipe_t *pipe_,
     void (*func_) (unsigned char *data_, size_t size_, void *arg_),
-    void *arg_)
+    void *arg_, bool call_on_uniq_)
 {
     unsigned char *buff = NULL;
-    rm_helper (pipe_, &buff, 0, 0, func_, arg_);
+    rm_helper (pipe_, &buff, 0, 0, func_, arg_, call_on_uniq_);
     free (buff);
 }
 
 void zmq::mtrie_t::rm_helper (pipe_t *pipe_, unsigned char **buff_,
     size_t buffsize_, size_t maxbuffsize_,
     void (*func_) (unsigned char *data_, size_t size_, void *arg_),
-    void *arg_)
+    void *arg_, bool call_on_uniq_)
 {
     //  Remove the subscription from this node.
-    if (pipes && pipes->erase (pipe_) && pipes->empty ()) {
+    if (pipes && pipes->erase (pipe_)) {
-        func_ (*buff_, buffsize_, arg_);
+        if (!call_on_uniq_ || pipes->empty ()) {
-        delete pipes;
+            func_ (*buff_, buffsize_, arg_);
-        pipes = 0;
+        }
+
+        if (pipes->empty ()) {
+            delete pipes;
+            pipes = 0;
+        }
     }
 
     //  Adjust the buffer.
@@ -194,7 +199,7 @@ void zmq::mtrie_t::rm_helper (pipe_t *pipe_, unsigned char **buff_,
         (*buff_) [buffsize_] = min;
         buffsize_++;
         next.node->rm_helper (pipe_, buff_, buffsize_, maxbuffsize_,
-            func_, arg_);
+            func_, arg_, call_on_uniq_);
 
         //  Prune the node if it was made redundant by the removal
         if (next.node->is_redundant ()) {
@@ -217,7 +222,7 @@ void zmq::mtrie_t::rm_helper (pipe_t *pipe_, unsigned char **buff_,
         (*buff_) [buffsize_] = min + c;
         if (next.table [c]) {
             next.table [c]->rm_helper (pipe_, buff_, buffsize_ + 1,
-                maxbuffsize_, func_, arg_);
+                maxbuffsize_, func_, arg_, call_on_uniq_);
 
             //  Prune redundant nodes from the mtrie
             if (next.table [c]->is_redundant ()) {

src/mtrie.hpp

@@ -54,11 +54,12 @@ namespace zmq
         bool add (unsigned char *prefix_, size_t size_, zmq::pipe_t *pipe_);
 
         //  Remove all subscriptions for a specific peer from the trie.
-        //  If there are no subscriptions left on some topics, invoke the
+        //  The call_on_uniq_ flag controls if the callback is invoked
-        //  supplied callback function.
+        //  when there are no subscriptions left on some topics or on
+        //  every removal.
         void rm (zmq::pipe_t *pipe_,
             void (*func_) (unsigned char *data_, size_t size_, void *arg_),
-            void *arg_);
+            void *arg_, bool call_on_uniq_);
 
         //  Remove specific subscription from the trie. Return true is it was
         //  actually removed rather than de-duplicated.
@@ -75,7 +76,7 @@ namespace zmq
         void rm_helper (zmq::pipe_t *pipe_, unsigned char **buff_,
             size_t buffsize_, size_t maxbuffsize_,
             void (*func_) (unsigned char *data_, size_t size_, void *arg_),
-            void *arg_);
+            void *arg_, bool call_on_uniq_);
         bool rm_helper (unsigned char *prefix_, size_t size_,
             zmq::pipe_t *pipe_);
         bool is_redundant () const;

src/xpub.cpp

@@ -36,7 +36,8 @@
 
 zmq::xpub_t::xpub_t (class ctx_t *parent_, uint32_t tid_, int sid_) :
     socket_base_t (parent_, tid_, sid_),
-    verbose (false),
+    verbose_subs (false),
+    verbose_unsubs (false),
     more (false),
     lossy (true),
 	manual(false),
@@ -101,9 +102,11 @@ void zmq::xpub_t::xread_activated (pipe_t *pipe_)
 				else
 					unique = subscriptions.add(data + 1, size - 1, pipe_);
 
-				//  If the subscription is not a duplicate store it so that it can be
+				//  If the (un)subscription is not a duplicate store it so that it can be
-				//  passed to used on next recv call. (Unsubscribe is not verbose.)
+				//  passed to the user on next recv call unless verbose mode is enabled
-				if (options.type == ZMQ_XPUB && (unique || (*data && verbose))) {
+				//  which makes to pass always these messages.
+				if (options.type == ZMQ_XPUB && (unique || (*data == 1 && verbose_subs) ||
+						(*data == 0 && verbose_unsubs && verbose_subs))) {
 					pending_data.push_back(blob_t(data, size));
 					pending_flags.push_back(0);
 				}
@@ -126,7 +129,8 @@ void zmq::xpub_t::xwrite_activated (pipe_t *pipe_)
 int zmq::xpub_t::xsetsockopt (int option_, const void *optval_,
     size_t optvallen_)
 {	
-	if (option_ == ZMQ_XPUB_VERBOSE || option_ == ZMQ_XPUB_NODROP || option_ == ZMQ_XPUB_MANUAL)
+	if (option_ == ZMQ_XPUB_VERBOSE || option_ == ZMQ_XPUB_VERBOSE_UNSUBSCRIBE ||
+		option_ == ZMQ_XPUB_NODROP || option_ == ZMQ_XPUB_MANUAL)
 	{
 		if (optvallen_ != sizeof(int) || *static_cast <const int*> (optval_) < 0) {
 			errno = EINVAL;
@@ -134,7 +138,10 @@ int zmq::xpub_t::xsetsockopt (int option_, const void *optval_,
 		}
 
 		if (option_ == ZMQ_XPUB_VERBOSE)
-			verbose = (*static_cast <const int*> (optval_) != 0);
+			verbose_subs = (*static_cast <const int*> (optval_) != 0);
+		else
+		if (option_ == ZMQ_XPUB_VERBOSE_UNSUBSCRIBE)
+			verbose_unsubs = (*static_cast <const int*> (optval_) != 0);
 		else
 		if (option_ == ZMQ_XPUB_NODROP)
 			lossy = (*static_cast <const int*> (optval_) == 0);
@@ -173,7 +180,7 @@ 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);
+    subscriptions.rm (pipe_, send_unsubscription, this, !verbose_unsubs);
 
     dist.pipe_terminated (pipe_);
 }

src/xpub.hpp

@@ -84,7 +84,11 @@ namespace zmq
 
         // If true, send all subscription messages upstream, not just
         // unique ones
-        bool verbose;
+        bool verbose_subs;
+
+        // If true, send all unsubscription messages upstream, not just
+        // unique ones
+        bool verbose_unsubs;
 
         //  True if we are in the middle of sending a multi-part message.
         bool more;