diff --git a/src/diag_io.c b/src/diag_io.c
index b4313bb..087eecf 100644
--- a/src/diag_io.c
+++ b/src/diag_io.c
@@ -41,6 +41,9 @@
 	struct diag_send_desc_type send;
 	struct diag_hdlc_dest_type enc = { NULL, NULL, 0 };
 
+	if (di->flags & DIAG_INST_F_HEXDUMP)
+		printf("Tx: %s\n", msgb_hexdump(msg));
+
 	send.state = DIAG_STATE_START;
 	send.pkt = msgb_data(msg);
 	send.last = msgb_data(msg) + msgb_length(msg) - 1;
@@ -128,6 +131,10 @@
 			msgb_free(msg);
 			return NULL;
 		}
+
+		if (di->flags & DIAG_INST_F_HEXDUMP)
+			printf("Rx: %s\n", msgb_hexdump(msg));
+
 		return msg;
 	}
 
diff --git a/src/diag_io.h b/src/diag_io.h
index 953a089..1dffa15 100644
--- a/src/diag_io.h
+++ b/src/diag_io.h
@@ -4,6 +4,8 @@
 #include <osmocom/core/msgb.h>
 #include <osmocom/core/gsmtap_util.h>
 
+#define DIAG_INST_F_HEXDUMP	0x00000001
+
 struct diag_instance {
 	int fd;
 	struct {
@@ -12,6 +14,7 @@
 	struct {
 	} tx;
 	struct gsmtap_inst *gsmtap;
+	uint32_t flags;
 };
 
 struct msgb *msgb_alloc_diag(void);