diff --git a/netdissect.c b/netdissect.c
new file mode 100644
index 0000000..0215c83
--- /dev/null
+++ b/netdissect.c
@@ -0,0 +1,146 @@
+/*
+ * Copyright (c) 1988-1997
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Copyright (c) 1998-2012  Michael Richardson <mcr@tcpdump.org>
+ *      The TCPDUMP project
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that: (1) source code distributions
+ * retain the above copyright notice and this paragraph in its entirety, (2)
+ * distributions including binary code include the above copyright notice and
+ * this paragraph in its entirety in the documentation or other materials
+ * provided with the distribution, and (3) all advertising materials mentioning
+ * features or use of this software display the following acknowledgement:
+ * ``This product includes software developed by the University of California,
+ * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
+ * the University nor the names of its contributors may be used to endorse
+ * or promote products derived from this software without specific prior
+ * written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <netdissect-stdinc.h>
+#include "netdissect.h"
+#include <string.h>
+#include <stdio.h>
+
+#ifdef USE_LIBSMI
+#include <smi.h>
+#endif
+
+/*
+ * Initialize anything that must be initialized before dissecting
+ * packets.
+ *
+ * This should be called at the beginning of the program; it does
+ * not need to be called, and should not be called, for every
+ * netdissect_options structure.
+ */
+int
+nd_init(char *errbuf, size_t errbuf_size)
+{
+#ifdef _WIN32
+	WORD wVersionRequested;
+	WSADATA wsaData;
+	int err;
+
+	/*
+	 * Request Winsock 2.2; we expect Winsock 2.
+	 */
+	wVersionRequested = MAKEWORD(2, 2);
+	err = WSAStartup(wVersionRequested, &wsaData);
+	if (err != 0) {
+		strlcpy(errbuf, "Attempting to initialize Winsock failed",
+		    errbuf_size);
+		return (-1);
+	}
+#endif /* _WIN32 */
+
+#ifdef USE_LIBSMI
+	/*
+	 * XXX - should we just fail if this fails?  Some of the
+	 * libsmi calls may fail.
+	 */
+	smiInit("tcpdump");
+#endif
+
+	/*
+	 * Clears the error buffer, and uses it so we don't get
+	 * "unused argument" warnings at compile time.
+	 */
+	strlcpy(errbuf, "", errbuf_size);
+	return (0);
+}
+
+/*
+ * Clean up anything that ndo_init() did.
+ */
+void
+nd_cleanup(void)
+{
+#ifdef USE_LIBSMI
+	/*
+	 * This appears, in libsmi 0.4.8, to do nothing if smiInit()
+	 * wasn't done or failed, so we call it unconditionally.
+	 */
+	smiExit();
+#endif
+
+#ifdef _WIN32
+	/*
+	 * Undo the WSAStartup() call above.
+	 */
+	WSACleanup();
+#endif
+}
+
+int
+nd_have_smi_support(void)
+{
+#ifdef USE_LIBSMI
+	return (1);
+#else
+	return (0);
+#endif
+}
+
+/*
+ * Indicates whether an SMI module has been loaded, so that we can use
+ * libsmi to translate OIDs.
+ */
+int nd_smi_module_loaded;
+
+int
+nd_load_smi_module(const char *module, char *errbuf, size_t errbuf_size)
+{
+#ifdef USE_LIBSMI
+	if (smiLoadModule(module) == 0) {
+		snprintf(errbuf, errbuf_size, "could not load MIB module %s",
+		    module);
+		return (-1);
+	}
+	nd_smi_module_loaded = 1;
+	return (0);
+#else
+	snprintf(errbuf, errbuf_size, "MIB module %s not loaded: no libsmi support",
+	    module);
+	return (-1);
+#endif
+}
+
+const char *
+nd_smi_version_string(void)
+{
+#ifdef USE_LIBSMI
+	return (smi_version_string);
+#else
+	return (NULL);
+#endif
+}