Fix dish socket multicast bind issue

src/udp_address.cpp

@@ -125,7 +125,6 @@ int zmq::udp_address_t::resolve (const char *name_, bool bind_, bool ipv6_)
         if (_is_multicast || !bind_) {
             _bind_address = ip_addr_t::any (_target_address.family ());
             _bind_address.set_port (port);
-            _bind_interface = 0;
         } else {
             //  If we were asked for a bind socket and the address
             //  provided was not multicast then it was really meant as
@@ -141,9 +140,12 @@ int zmq::udp_address_t::resolve (const char *name_, bool bind_, bool ipv6_)
 
     //  For IPv6 multicast we *must* have an interface index since we can't
     //  bind by address.
-    if (ipv6_ && _is_multicast && _bind_interface < 0) {
-        errno = ENODEV;
-        return -1;
+    if (ipv6_ && _is_multicast && bind_) {
+        if (_bind_interface < 0) {
+            errno = ENODEV;
+            return -1;
+        }
+        _target_address.ipv6.sin6_scope_id = _bind_interface;
     }
 
     return 0;

src/udp_engine.cpp

@@ -133,7 +133,6 @@ void zmq::udp_engine_t::plug (io_thread_t *io_thread_, session_base_t *session_)
         rc = rc | set_udp_reuse_address (_fd, true);
 
         const ip_addr_t *bind_addr = udp_addr->bind_addr ();
-        ip_addr_t any = ip_addr_t::any (bind_addr->family ());
         const ip_addr_t *real_bind_addr;
 
         const bool multicast = udp_addr->is_mcast ();
@@ -143,11 +142,10 @@ void zmq::udp_engine_t::plug (io_thread_t *io_thread_, session_base_t *session_)
             //  one port as all ports should receive the message
             rc = rc | set_udp_reuse_port (_fd, true);
 
-            //  In multicast we should bind ANY and use the mreq struct to
-            //  specify the interface
-            any.set_port (bind_addr->port ());
+            //  In multicast we should bind the target address and use the
+            //  mreq struct to specify the interface
 
-            real_bind_addr = &any;
+            real_bind_addr = udp_addr->target_addr ();
         } else {
             real_bind_addr = bind_addr;
         }

tests/test_radio_dish.cpp

@@ -261,7 +261,7 @@ MAKE_TEST_V4V6 (test_radio_dish_udp)
 static const char *mcast_url (int ipv6_)
 {
     if (ipv6_) {
-        return "udp://[" MCAST_IPV6 "]:5555";
+        return "udp://eth0;[" MCAST_IPV6 "]:5555";
     }
     return "udp://" MCAST_IPV4 ":5555";
 }

unittests/unittest_udp_address.cpp

@@ -23,7 +23,8 @@ static void test_resolve (bool bind_,
                           const char *target_addr_,
                           uint16_t expected_port_,
                           const char *bind_addr_,
-                          bool multicast_)
+                          bool multicast_,
+                          uint16_t expected_zone = 0)
 {
     if (family_ == AF_INET6 && !is_ipv6_available ()) {
         TEST_IGNORE_MESSAGE ("ipv6 is not available");
@@ -53,7 +54,7 @@ static void test_resolve (bool bind_,
     }
 
     validate_address (family_, addr.target_addr (), target_addr_,
-                      expected_port_);
+                      expected_port_, expected_zone);
     validate_address (family_, addr.bind_addr (), bind_addr_, expected_port_);
 }
 
@@ -62,10 +63,11 @@ static void test_resolve_bind (int family_,
                                const char *dest_addr_,
                                uint16_t expected_port_ = 0,
                                const char *bind_addr_ = NULL,
-                               bool multicast_ = false)
+                               bool multicast_ = false,
+                               uint16_t expected_zone = 0)
 {
     test_resolve (true, family_, name_, dest_addr_, expected_port_, bind_addr_,
-                  multicast_);
+                  multicast_, expected_zone);
 }
 
 static void test_resolve_connect (int family_,
@@ -172,7 +174,7 @@ static void test_resolve_ipv4_bind_mcast ()
 
 static void test_resolve_ipv6_bind_mcast ()
 {
-    test_resolve_bind (AF_INET6, "[ff00::1]:1234", "ff00::1", 1234, "::", true);
+    test_resolve_bind (AF_INET6, "eth0;[ff00::1]:1234", "ff00::1", 1234, "fe80::", true, 2);
 }
 
 static void test_resolve_ipv4_connect_mcast ()
@@ -232,7 +234,7 @@ static void test_resolve_ipv6_mcast_src_connect ()
     }
 
     zmq::udp_address_t addr;
-    int rc = addr.resolve ("[1:2:3::4];[ff01::1]:5555", false, true);
+    int rc = addr.resolve ("[1:2:3::4];[ff01::1]:5555", true, true);
 
     //  For the time being this fails because we only support binding multicast
     //  by interface name, not interface IP