1 files changed, 26 insertions, 0 deletions
diff --git a/src/or/proto_control0.c b/src/or/proto_control0.c
new file mode 100644
index 0000000000..c17ba34948
--- /dev/null
+++ b/src/or/proto_control0.c
@@ -0,0 +1,26 @@
+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2017, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#include "or.h"
+#include "buffers.h"
+#include "proto_control0.h"
+
+/** Return 1 iff buf looks more like it has an (obsolete) v0 controller
+ * command on it than any valid v1 controller command. */
+int
+peek_buf_has_control0_command(buf_t *buf)
+{
+  if (buf_datalen(buf) >= 4) {
+    char header[4];
+    uint16_t cmd;
+    buf_peek(buf, header, sizeof(header));
+    cmd = ntohs(get_uint16(header+2));
+    if (cmd <= 0x14)
+      return 1; /* This is definitely not a v1 control command. */
+  }
+  return 0;
+}
+