zmq: add monitor code for sockets but disable it

according to the ZMQ dev guide, one can use a socket monitor
to get informed about changes to a socket, e.g. when a client disconnected.

This is useful to detect when a UE dropped the connection to reinitialize
the socket and timers in a eNB.

This commit adds code to create such a socket monitor but leaves
it disabled because it still doesn't work as expected.

lib/src/phy/rf/rf_zmq_imp.c

@@ -657,6 +657,47 @@ void rf_zmq_get_time(void* h, time_t* secs, double* frac_secs)
   }
 }
 
+#if ZMQ_MONITOR
+static int rf_zmq_rx_get_monitor_event(void* monitor, int* value, char** address)
+{
+  // First frame in message contains event number and value
+  zmq_msg_t msg;
+  zmq_msg_init(&msg);
+  if (zmq_msg_recv(&msg, monitor, 0) == -1) {
+    printf("zmq_msg_recv failed!\n");
+    return -1; // Interruped, presumably
+  }
+
+  if (zmq_msg_more(&msg)) {
+    printf("more to read\n");
+  }
+
+  uint8_t* data  = (uint8_t*)zmq_msg_data(&msg);
+  uint16_t event = *(uint16_t*)(data);
+  if (value) {
+    *value = *(uint32_t*)(data + 2);
+  }
+
+  // Second frame in message contains event address
+  zmq_msg_init(&msg);
+  if (zmq_msg_recv(&msg, monitor, 0) == -1) {
+    return -1; // Interruped, presumably
+  }
+  if (zmq_msg_more(&msg)) {
+    printf("error in msg_more \n");
+  }
+
+  if (address) {
+    uint8_t* data = (uint8_t*)zmq_msg_data(&msg);
+    size_t   size = zmq_msg_size(&msg);
+    *address      = (char*)malloc(size + 1);
+    memcpy(*address, data, size);
+    *address[size] = 0;
+  }
+  return event;
+}
+#endif // ZMQ_MONITOR
+
 int rf_zmq_recv_with_time(void* h, void* data, uint32_t nsamples, bool blocking, time_t* secs, double* frac_secs)
 {
   return rf_zmq_recv_with_time_multi(h, &data, nsamples, blocking, secs, frac_secs);
@@ -757,6 +798,23 @@ int rf_zmq_recv_with_time_multi(void*    h,
         if (count[i] < nsamples_baserate && handler->receiver[i].running) {
           // Keep receiving
           int32_t n = rf_zmq_rx_baseband(&handler->receiver[i], &ptr[count[i]], nsamples_baserate);
+#if ZMQ_MONITOR
+          // handle socket events
+          int event = rf_zmq_rx_get_monitor_event(handler->receiver[i].socket_monitor, NULL, NULL);
+          if (event != -1) {
+            printf("event=0x%X\n", event);
+            switch (event) {
+              case ZMQ_EVENT_CONNECTED:
+                handler->receiver[i].tx_connected = true;
+                break;
+              case ZMQ_EVENT_CLOSED:
+                handler->receiver[i].tx_connected = false;
+                break;
+              default:
+                break;
+            }
+          }
+#endif // ZMQ_MONITOR
           if (n > 0) {
             // No error
             count[i] += n;

lib/src/phy/rf/rf_zmq_imp_rx.c

@@ -118,14 +118,32 @@ int rf_zmq_rx_open(rf_zmq_rx_t* q, rf_zmq_opts_t opts, void* zmq_ctx, char* sock
       fprintf(stderr, "[zmq] Error: creating transmitter socket\n");
       goto clean_exit;
     }
-    q->socket_type   = opts.socket_type;
+    q->socket_type        = opts.socket_type;
     q->sample_format = opts.sample_format;
     q->frequency_mhz = opts.frequency_mhz;
+    q->fail_on_disconnect = opts.fail_on_disconnect;
 
     if (opts.socket_type == ZMQ_SUB) {
       zmq_setsockopt(q->sock, ZMQ_SUBSCRIBE, "", 0);
     }
 
+#if ZMQ_MONITOR
+    // Monitor all events (monitoring only works over inproc://)
+    ret = zmq_socket_monitor(q->sock, "inproc://monitor-client", ZMQ_EVENT_ALL);
+    if (ret == -1) {
+      fprintf(stderr, "Error: creating socket monitor: %s\n", zmq_strerror(zmq_errno()));
+      goto clean_exit;
+    }
+
+    // create socket socket for monitoring and connect monitor
+    q->socket_monitor = zmq_socket(zmq_ctx, ZMQ_PAIR);
+    ret               = zmq_connect(q->socket_monitor, "inproc://monitor-client");
+    if (ret) {
+      fprintf(stderr, "Error: connecting monitor socket: %s\n", zmq_strerror(zmq_errno()));
+      goto clean_exit;
+    }
+#endif // ZMQ_MONITOR
+
     rf_zmq_info(q->id, "Connecting receiver: %s\n", sock_args);
 
     ret = zmq_connect(q->sock, sock_args);
@@ -242,4 +260,11 @@ void rf_zmq_rx_close(rf_zmq_rx_t* q)
     zmq_close(q->sock);
     q->sock = NULL;
   }
+
+#if ZMQ_MONITOR
+  if (q->socket_monitor) {
+    zmq_close(q->socket_monitor);
+    q->socket_monitor = NULL;
+  }
+#endif // ZMQ_MONITOR
 }

lib/src/phy/rf/rf_zmq_imp_trx.h

@@ -33,6 +33,7 @@
 
 /* Definitions */
 #define VERBOSE (0)
+#define ZMQ_MONITOR (0)
 #define NSAMPLES2NBYTES(X) (((uint32_t)(X)) * sizeof(cf_t))
 #define NBYTES2NSAMPLES(X) ((X) / sizeof(cf_t))
 #define ZMQ_MAX_BUFFER_SIZE (NSAMPLES2NBYTES(3072000)) // 10 subframes at 20 MHz
@@ -62,6 +63,10 @@ typedef struct {
   uint32_t            socket_type;
   rf_zmq_format_t     sample_format;
   void*               sock;
+#if ZMQ_MONITOR
+  void* socket_monitor;
+  bool  tx_connected;
+#endif
   uint64_t            nsamples;
   bool                running;
   pthread_t           thread;