ZMQ_MULTICAST_HOPS socket option added

Sets the time-to-live field in every multicast packet sent from the socket.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

doc/zmq_getsockopt.txt

@@ -283,7 +283,7 @@ Applicable socket types:: all, only for connection-oriented transports
 ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The options shall retrieve limit for the inbound messages. If a peer sends
+The option shall retrieve limit for the inbound messages. If a peer sends
 a message larger than ZMQ_MAXMSGSIZE it is disconnected. Value of -1 means
 'no limit'.
 
@@ -294,6 +294,19 @@ Default value:: -1
 Applicable socket types:: all
 
 
+ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packets
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The option shell retrieve time-to-live used for outbound multicast packets.
+The default of 1 means that the multicast packets don't leave the local network.
+
+[horizontal]
+Option value type:: int
+Option value unit:: network hops
+Default value:: 1
+Applicable socket types:: all, when using multicast transports
+
+
 ZMQ_FD: Retrieve file descriptor associated with the socket
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The 'ZMQ_FD' option shall retrieve the file descriptor associated with the

doc/zmq_setsockopt.txt

@@ -296,6 +296,18 @@ Option value unit:: bytes
 Default value:: -1
 Applicable socket types:: all
 
+ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packets
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Sets the time-to-live field in every multicast packet sent from this socket.
+The default is 1 which means that the multicast packets don't leave the local
+network.
+
+[horizontal]
+Option value type:: int
+Option value unit:: network hops
+Default value:: 1
+Applicable socket types:: all, when using multicast transports
 
 RETURN VALUE
 ------------

include/zmq.h

@@ -179,6 +179,7 @@ ZMQ_EXPORT int zmq_term (void *context);
 #define ZMQ_MAXMSGSIZE 22
 #define ZMQ_SNDHWM 23
 #define ZMQ_RCVHWM 24
+#define ZMQ_MULTICAST_HOPS 25
     
 /*  Send/recv options.                                                        */
 #define ZMQ_DONTWAIT 1

src/options.cpp

@@ -29,6 +29,7 @@ zmq::options_t::options_t () :
     affinity (0),
     rate (100),
     recovery_ivl (10000),
+    multicast_hops (1),
     sndbuf (0),
     rcvbuf (0),
     type (-1),
@@ -165,6 +166,14 @@ int zmq::options_t::setsockopt (int option_, const void *optval_,
         maxmsgsize = *((int64_t*) optval_);
         return 0;
 
+    case ZMQ_MULTICAST_HOPS:
+        if (optvallen_ != sizeof (int) || *((int*) optval_) <= 0) {
+            errno = EINVAL;
+            return -1;
+        }
+        multicast_hops = *((int*) optval_);
+        return 0;
+
     }
 
     errno = EINVAL;
@@ -301,6 +310,15 @@ int zmq::options_t::getsockopt (int option_, void *optval_, size_t *optvallen_)
         *optvallen_ = sizeof (int64_t);
         return 0;
 
+    case ZMQ_MULTICAST_HOPS:
+        if (*optvallen_ < sizeof (int)) {
+            errno = EINVAL;
+            return -1;
+        }
+        *((int*) optval_) = multicast_hops;
+        *optvallen_ = sizeof (int);
+        return 0;
+
     }
 
     errno = EINVAL;

src/options.hpp

@@ -48,6 +48,9 @@ namespace zmq
         //  Reliability time interval [ms]. Default 10 seconds.
         int recovery_ivl;
 
+        // Sets the time-to-live field in every multicast packet sent.
+        int multicast_hops;
+
         // SO_SNDBUF and SO_RCVBUF to be passed to underlying transport sockets.
         int sndbuf;
         int rcvbuf;

src/pgm_socket.cpp

@@ -169,24 +169,30 @@ int zmq::pgm_socket_t::init (bool udp_encapsulation_, const char *network_)
     }
 
     {
-        const int rcvbuf = (int) options.rcvbuf,
-                  sndbuf = (int) options.sndbuf,
-                  max_tpdu = (int) pgm_max_tpdu;
+        //  Propagate various socket options to the OpenPGM layer.
+        const int rcvbuf = (int) options.rcvbuf;
         if (rcvbuf) {
             if (!pgm_setsockopt (sock, SOL_SOCKET, SO_RCVBUF, &rcvbuf,
                   sizeof (rcvbuf)))
                 goto err_abort;
         }
+
+        const int sndbuf = (int) options.sndbuf;
         if (sndbuf) {
             if (!pgm_setsockopt (sock, SOL_SOCKET, SO_SNDBUF, &sndbuf,
                   sizeof (sndbuf)))
                 goto err_abort;
         }
 
-        //  Set maximum transport protocol data unit size (TPDU).
+        const int max_tpdu = (int) pgm_max_tpdu;
         if (!pgm_setsockopt (sock, IPPROTO_PGM, PGM_MTU, &max_tpdu,
               sizeof (max_tpdu)))
             goto err_abort;
+
+        const int multicast_hops = (int) options.multicast_hops;
+        if (!pgm_setsockopt (sock, IPPROTO_PGM, PGM_MULTICAST_HOPS,
+              &multicast_hops, sizeof (int)))
+            goto err_abort;
     }
 
     if (receiver) {