Add support to the ROUTER socket to reassign identities upon name collision.

include/zmq.h

@@ -292,6 +292,7 @@ ZMQ_EXPORT int zmq_msg_set (zmq_msg_t *msg, int option, int optval);
 #define ZMQ_REQ_RELAXED 53
 #define ZMQ_CONFLATE 54
 #define ZMQ_ZAP_DOMAIN 55
+#define ZMQ_ROUTER_REASSIGN_IDENTITES 56
 
 /*  Message options                                                           */
 #define ZMQ_MORE 1

src/router.cpp

@@ -35,7 +35,8 @@ zmq::router_t::router_t (class ctx_t *parent_, uint32_t tid_, int sid_) :
     mandatory (false),
     //  raw_sock functionality in ROUTER is deprecated
     raw_sock (false),       
-    probe_router (false)
+    probe_router (false),
+    reassign_identities(false)
 {
     options.type = ZMQ_ROUTER;
     options.recv_identity = true;
@@ -111,6 +112,12 @@ int zmq::router_t::xsetsockopt (int option_, const void *optval_,
                 return 0;
             }
             break;
+        case ZMQ_ROUTER_REASSIGN_IDENTITES: 
+            if (is_int && value >= 0) {
+                reassign_identities = (value != 0);
+                return 0;
+            }
+            break;
 
         default:
             break;
@@ -394,10 +401,38 @@ bool zmq::router_t::identify_peer (pipe_t *pipe_)
             outpipes_t::iterator it = outpipes.find (identity);
             msg.close ();
 
-            //  Ignore peers with duplicate ID.
             if (it != outpipes.end ())
+            {
+                if (!reassign_identities) {
+                    //  Ignore peers with duplicate ID.
                     return false;
                 }
+                else
+                {
+                    //  We will allow the new connection to take over this
+                    //  identity. Temporarily assign a new identity to the 
+                    //  existing pipe so we can terminate it asynchronously.
+                    unsigned char buf [5];
+                    buf [0] = 0;
+                    put_uint32 (buf + 1, next_peer_id++);
+                    blob_t new_identity = blob_t (buf, sizeof buf);
+
+                    it->second.pipe->set_identity (new_identity);
+                    outpipe_t existing_outpipe = 
+                        {it->second.pipe, it->second.active};
+                
+                    ok = outpipes.insert (outpipes_t::value_type (
+                        new_identity, existing_outpipe)).second;
+                    zmq_assert (ok);
+                
+                    //  Remove the existing identity entry to allow the new
+                    //  connection to take the identity.
+                    outpipes.erase (it);
+
+                    existing_outpipe.pipe->terminate (true);
+                }
+            }
+        }
     }
 
     pipe_->set_identity (identity);

src/router.hpp

@@ -115,6 +115,11 @@ namespace zmq
         // if true, send an empty message to every connected router peer
         bool probe_router;
 
+        // If true, the router will reassign an identity upon encountering a
+        // name collision. The new pipe will take the identity, the old pipe
+        // will be terminated.
+        bool reassign_identities;
+
         router_t (const router_t&);
         const router_t &operator = (const router_t&);
     };