multiplex: In ZRTP header, use network byte order for Magic Cookie. Also detect received ZRTP messages with it.

src/reception_flow.cc

@@ -674,6 +674,13 @@ void uvgrtp::reception_flow::process_packet(int rce_flags)
                         }
                     }
 
+                    /* -------------------- ZRTP check -------------------- */
+
+                    if (ntohl((uint32_t)ptr[4]) == 0x5a525450) {
+                        // TODO: Add functionality
+                        UVG_LOG_INFO("ZRTP message");
+                    }
+
                     // Here we don't lock ring mutex because the chaging is only done above. 
                     // NOTE: If there is a need for multiple processing threads, the read should be guarded
                     switch ((ret = (*handler.second.primary)(ring_buffer_[ring_read_index_].read,

src/zrtp/zrtp_message.cc

@@ -59,7 +59,7 @@ void uvgrtp::zrtp_msg::zrtp_message::set_zrtp_start_base(uvgrtp::zrtp_msg::zrtp_
     std::string msgblock)
 {
     start.header.version = 0;
-    start.header.magic = ZRTP_MAGIC;
+    start.header.magic = htonl(ZRTP_MAGIC);
     start.preamble = ZRTP_PREAMBLE;
     start.length = packet_to_header_len(len_);
     memcpy(&start.msgblock, msgblock.c_str(), 8);