From 5f07fe8cbb9d3696e94bb9c64625e23721c95c4e Mon Sep 17 00:00:00 2001
From: Mark Andrews <marka@isc.org>
Date: Thu, 15 Sep 2022 17:03:50 +1000
Subject: [PATCH] Use strnstr implementation from FreeBSD if not provided by OS

---
 configure.ac                 |  2 +-
 lib/isc/include/isc/string.h |  5 +++++
 lib/isc/string.c             | 28 ++++++++++++++++++++++++++++
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 037b10a0b6..04d400f8de 100644
--- a/configure.ac
+++ b/configure.ac
@@ -991,7 +991,7 @@ AS_IF([test "$enable_tcp_fastopen" = "yes"],
 #
 # Check for some other useful functions that are not ever-present.
 #
-AC_CHECK_FUNCS([strlcpy strlcat])
+AC_CHECK_FUNCS([strlcpy strlcat strnstr])
 
 #
 # Check for readline support
diff --git a/lib/isc/include/isc/string.h b/lib/isc/include/isc/string.h
index 5469d69a0e..fbf6129cbe 100644
--- a/lib/isc/include/isc/string.h
+++ b/lib/isc/include/isc/string.h
@@ -31,6 +31,11 @@ size_t
 strlcat(char *dst, const char *src, size_t size);
 #endif /* if !defined(HAVE_STRLCAT) */
 
+#if !defined(HAVE_STRNSTR)
+char *
+strnstr(const char *s, const char *find, size_t slen);
+#endif /* if !defined(HAVE_STRNSTR) */
+
 int
 isc_string_strerror_r(int errnum, char *buf, size_t buflen);
 
diff --git a/lib/isc/string.c b/lib/isc/string.c
index f1ee7748cd..09cf5d636c 100644
--- a/lib/isc/string.c
+++ b/lib/isc/string.c
@@ -12,9 +12,15 @@
  */
 
 /*
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
  * Copyright (c) 1990, 1993
  *	The Regents of the University of California.  All rights reserved.
  *
+ * This code is derived from software contributed to Berkeley by
+ * Chris Torek.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -109,6 +115,28 @@ strlcat(char *dst, const char *src, size_t size) {
 }
 #endif /* !defined(HAVE_STRLCAT) */
 
+#if !defined(HAVE_STRNSTR)
+char *
+strnstr(const char *s, const char *find, size_t slen) {
+	char c, sc;
+	size_t len;
+
+	if ((c = *find++) != '\0') {
+		len = strlen(find);
+		do {
+			do {
+				if (slen-- < 1 || (sc = *s++) == '\0')
+					return (NULL);
+			} while (sc != c);
+			if (len > slen)
+				return (NULL);
+		} while (strncmp(s, find, len) != 0);
+		s--;
+	}
+	return ((char *)s);
+}
+#endif
+
 int
 isc_string_strerror_r(int errnum, char *buf, size_t buflen) {
 	return (strerror_r(errnum, buf, buflen));