diff --git a/libc/netbsd/nameser/ns_samedomain.c b/libc/netbsd/nameser/ns_samedomain.c
new file mode 100644
index 0000000..04fdb61
--- /dev/null
+++ b/libc/netbsd/nameser/ns_samedomain.c
@@ -0,0 +1,211 @@
+/*	$NetBSD: ns_samedomain.c,v 1.2 2004/05/20 20:35:05 christos Exp $	*/
+
+/*
+ * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
+ * Copyright (c) 1995,1999 by Internet Software Consortium.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
+ * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/cdefs.h>
+#ifndef lint
+#ifdef notdef
+static const char rcsid[] = "Id: ns_samedomain.c,v 1.1.2.2.4.2 2004/03/16 12:34:17 marka Exp";
+#else
+__RCSID("$NetBSD: ns_samedomain.c,v 1.2 2004/05/20 20:35:05 christos Exp $");
+#endif
+#endif
+
+#include <sys/types.h>
+#include "arpa_nameser.h"
+#include <errno.h>
+#include <string.h>
+
+#ifndef _LIBC
+/*
+ * int
+ * ns_samedomain(a, b)
+ *	Check whether a name belongs to a domain.
+ * Inputs:
+ *	a - the domain whose ancestory is being verified
+ *	b - the potential ancestor we're checking against
+ * Return:
+ *	boolean - is a at or below b?
+ * Notes:
+ *	Trailing dots are first removed from name and domain.
+ *	Always compare complete subdomains, not only whether the
+ *	domain name is the trailing string of the given name.
+ *
+ *	"host.foobar.top" lies in "foobar.top" and in "top" and in ""
+ *	but NOT in "bar.top"
+ */
+
+int
+ns_samedomain(const char *a, const char *b) {
+	size_t la, lb;
+	int diff, i, escaped;
+	const char *cp;
+
+	la = strlen(a);
+	lb = strlen(b);
+
+	/* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */
+	if (la != 0U && a[la - 1] == '.') {
+		escaped = 0;
+		/* Note this loop doesn't get executed if la==1. */
+		for (i = la - 2; i >= 0; i--)
+			if (a[i] == '\\') {
+				if (escaped)
+					escaped = 0;
+				else
+					escaped = 1;
+			} else
+				break;
+		if (!escaped)
+			la--;
+	}
+
+	/* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */
+	if (lb != 0U && b[lb - 1] == '.') {
+		escaped = 0;
+		/* note this loop doesn't get executed if lb==1 */
+		for (i = lb - 2; i >= 0; i--)
+			if (b[i] == '\\') {
+				if (escaped)
+					escaped = 0;
+				else
+					escaped = 1;
+			} else
+				break;
+		if (!escaped)
+			lb--;
+	}
+
+	/* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */
+	if (lb == 0U)
+		return (1);
+
+	/* 'b' longer than 'a' means 'a' can't be in 'b'. */
+	if (lb > la)
+		return (0);
+
+	/* 'a' and 'b' being equal at this point indicates sameness. */
+	if (lb == la)
+		return (strncasecmp(a, b, lb) == 0);
+
+	/* Ok, we know la > lb. */
+
+	diff = la - lb;
+
+	/*
+	 * If 'a' is only 1 character longer than 'b', then it can't be
+	 * a subdomain of 'b' (because of the need for the '.' label
+	 * separator).
+	 */
+	if (diff < 2)
+		return (0);
+
+	/*
+	 * If the character before the last 'lb' characters of 'b'
+	 * isn't '.', then it can't be a match (this lets us avoid
+	 * having "foobar.com" match "bar.com").
+	 */
+	if (a[diff - 1] != '.')
+		return (0);
+
+	/*
+	 * We're not sure about that '.', however.  It could be escaped
+         * and thus not a really a label separator.
+	 */
+	escaped = 0;
+	for (i = diff - 2; i >= 0; i--)
+		if (a[i] == '\\') {
+			if (escaped)
+				escaped = 0;
+			else
+				escaped = 1;
+		} else
+			break;
+	if (escaped)
+		return (0);
+
+	/* Now compare aligned trailing substring. */
+	cp = a + diff;
+	return (strncasecmp(cp, b, lb) == 0);
+}
+
+/*
+ * int
+ * ns_subdomain(a, b)
+ *	is "a" a subdomain of "b"?
+ */
+int
+ns_subdomain(const char *a, const char *b) {
+	return (ns_samename(a, b) != 1 && ns_samedomain(a, b));
+}
+#endif
+
+/*
+ * int
+ * ns_makecanon(src, dst, dstsize)
+ *	make a canonical copy of domain name "src"
+ * notes:
+ *	foo -> foo.
+ *	foo. -> foo.
+ *	foo.. -> foo.
+ *	foo\. -> foo\..
+ *	foo\\. -> foo\\.
+ */
+
+int
+ns_makecanon(const char *src, char *dst, size_t dstsize) {
+	size_t n = strlen(src);
+
+	if (n + sizeof "." > dstsize) {			/* Note: sizeof == 2 */
+		errno = EMSGSIZE;
+		return (-1);
+	}
+	strcpy(dst, src);
+	while (n >= 1U && dst[n - 1] == '.')		/* Ends in "." */
+		if (n >= 2U && dst[n - 2] == '\\' &&	/* Ends in "\." */
+		    (n < 3U || dst[n - 3] != '\\'))	/* But not "\\." */
+			break;
+		else
+			dst[--n] = '\0';
+	dst[n++] = '.';
+	dst[n] = '\0';
+	return (0);
+}
+
+/*
+ * int
+ * ns_samename(a, b)
+ *	determine whether domain name "a" is the same as domain name "b"
+ * return:
+ *	-1 on error
+ *	0 if names differ
+ *	1 if names are the same
+ */
+
+int
+ns_samename(const char *a, const char *b) {
+	char ta[NS_MAXDNAME], tb[NS_MAXDNAME];
+
+	if (ns_makecanon(a, ta, sizeof ta) < 0 ||
+	    ns_makecanon(b, tb, sizeof tb) < 0)
+		return (-1);
+	if (strcasecmp(ta, tb) == 0)
+		return (1);
+	else
+		return (0);
+}