diff --git a/sys/conf/files b/sys/conf/files
index 74f25c1c7c97..34477986ed2a 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -2559,6 +2559,7 @@ netinet/if_atm.c		optional atm
 netinet/if_ether.c		optional inet ether
 netinet/igmp.c			optional inet
 netinet/in.c			optional inet
+netinet/in_debug.c		optional inet ddb
 netinet/ip_carp.c		optional inet carp | inet6 carp
 netinet/in_gif.c		optional gif inet | netgraph_gif inet
 netinet/ip_gre.c		optional gre inet
diff --git a/sys/netinet/in_debug.c b/sys/netinet/in_debug.c
new file mode 100644
index 000000000000..7624f1deedfc
--- /dev/null
+++ b/sys/netinet/in_debug.c
@@ -0,0 +1,120 @@
+/*-
+ * Copyright (c) 2010 Bjoern A. Zeeb <bz@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_ddb.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/socket.h>
+
+#ifdef DDB
+#include <ddb/ddb.h>
+#endif
+
+#include <net/if.h>
+#include <net/if_var.h>
+
+#include <netinet/in.h>
+#include <netinet/in_var.h>
+
+#ifdef DDB
+static void
+in_show_sockaddr_in(struct sockaddr_in *sin)
+{
+
+#define	SIN_DB_RPINTF(f, e)	db_printf("\t   %s = " f "\n", #e, sin->e);
+	db_printf("\tsockaddr_in = %p\n", sin);
+	SIN_DB_RPINTF("%u", sin_len);
+	SIN_DB_RPINTF("%u", sin_family);
+	SIN_DB_RPINTF("%u", sin_port);
+	SIN_DB_RPINTF("0x%08x", sin_addr.s_addr);
+	db_printf("\t   %s = %02x%02x%02x%02x%02x%02x%02x%02x\n",
+	    "sin_zero[8]",
+	    sin->sin_zero[0], sin->sin_zero[1],
+	    sin->sin_zero[2], sin->sin_zero[3],
+	    sin->sin_zero[4], sin->sin_zero[5],
+	    sin->sin_zero[6], sin->sin_zero[7]);
+#undef SIN_DB_RPINTF
+}
+
+DB_SHOW_COMMAND(sin, db_show_sin)
+{
+	struct sockaddr_in *sin;
+
+	sin = (struct sockaddr_in *)addr;
+	if (sin == NULL) {
+		/* usage: No need to confess if you didn't sin. */
+		db_printf("usage: show sin <struct sockaddr_in *>\n");
+		return;
+	}
+
+	in_show_sockaddr_in(sin);
+}
+
+static void
+in_show_in_ifaddr(struct in_ifaddr *ia)
+{
+
+#define	IA_DB_RPINTF(f, e)	db_printf("\t   %s = " f "\n", #e, ia->e);
+#define	IA_DB_RPINTF_PTR(f, e)	db_printf("\t   %s = " f "\n", #e, &ia->e);
+#define	IA_DB_RPINTF_DPTR(f, e)	db_printf("\t  *%s = " f "\n", #e, *ia->e);
+	db_printf("\tin_ifaddr = %p\n", ia);
+	IA_DB_RPINTF_PTR("%p", ia_ifa);
+	IA_DB_RPINTF("0x%08lx", ia_net);
+	IA_DB_RPINTF("0x%08lx", ia_netmask);
+	IA_DB_RPINTF("0x%08lx", ia_subnet);
+	IA_DB_RPINTF("0x%08lx", ia_subnetmask);
+	IA_DB_RPINTF("0x%08x", ia_netbroadcast.s_addr);
+	IA_DB_RPINTF("%p", ia_hash.le_next);
+	IA_DB_RPINTF("%p", ia_hash.le_prev);
+	IA_DB_RPINTF_DPTR("%p", ia_hash.le_prev);
+	IA_DB_RPINTF("%p", ia_link.tqe_next);
+	IA_DB_RPINTF("%p", ia_link.tqe_prev);
+	IA_DB_RPINTF_DPTR("%p", ia_link.tqe_prev);
+	IA_DB_RPINTF_PTR("%p", ia_addr);
+	IA_DB_RPINTF_PTR("%p", ia_dstaddr);
+	IA_DB_RPINTF_PTR("%p", ia_sockmask);
+#undef IA_DB_RPINTF_DPTR
+#undef IA_DB_RPINTF_PTR
+#undef IA_DB_RPINTF
+}
+
+DB_SHOW_COMMAND(in_ifaddr, db_show_in_ifaddr)
+{
+	struct in_ifaddr *ia;
+
+	ia = (struct in_ifaddr *)addr;
+	if (ia == NULL) {
+		db_printf("usage: show in_ifaddr <struct in_ifaddr *>\n");
+		return;
+	}
+
+	in_show_in_ifaddr(ia);
+}
+#endif