MXS-3051: Show connection TLS cipher

This tells the user whether a session is using TLS or not. Currently, only
the client TLS cipher is shown in MaxCtrl as the backend ciphers require
additional formatting.

maxctrl/lib/show.js

@@ -208,6 +208,11 @@ const session_fields = [
         path: 'attributes.idle',
         description: 'How long the session has been idle, in seconds'
     },
+    {
+        name: 'Client TLS Cipher',
+        path: 'attributes.client.cipher',
+        description: 'Client TLS cipher'
+    },
     {
         name: 'Connections',
         path: 'attributes.connections[].server',

server/core/dcb.cc

@@ -3866,7 +3866,16 @@ json_t* dcb_to_json(DCB* dcb)
     char buf[25];
     snprintf(buf, sizeof(buf), "%p", dcb);
     json_object_set_new(obj, "id", json_string(buf));
-    json_object_set_new(obj, "server", json_string(dcb->server->name));
+
+    if (dcb->server)
+    {
+        json_object_set_new(obj, "server", json_string(dcb->server->name));
+    }
+
+    if (dcb->ssl)
+    {
+        json_object_set_new(obj, "cipher", json_string(SSL_get_cipher_name(dcb->ssl)));
+    }
 
     if (dcb->func.diagnostics_json)
     {

server/core/session.cc

@@ -876,6 +876,7 @@ json_t* session_json_data(const Session* session, const char* host)
     }
 
     json_object_set_new(attr, "connections", dcb_arr);
+    json_object_set_new(attr, "client", dcb_to_json(session->client_dcb));
 
     json_t* queries = session->queries_as_json();
     json_object_set_new(attr, "queries", queries);