diff --git a/include/haproxy/tools.h b/include/haproxy/tools.h
index 1a1751597..6e3848f49 100644
--- a/include/haproxy/tools.h
+++ b/include/haproxy/tools.h
@@ -915,6 +915,8 @@ void calltrace(char *fmt, ...);
 /* same as strstr() but case-insensitive */
 const char *strnistr(const char *str1, int len_str1, const char *str2, int len_str2);
 
+int strordered(const char *s1, const char *s2, const char *s3);
+
 /* after increasing a pointer value, it can exceed the first buffer
  * size. This function transform the value of <ptr> according with
  * the expected position. <chunks> is an array of the one or two
diff --git a/src/tools.c b/src/tools.c
index 34f86321c..5d5e1b02d 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -4363,6 +4363,15 @@ const char *strnistr(const char *str1, int len_str1, const char *str2, int len_s
 	return NULL;
 }
 
+/* Returns true if s1 < s2 < s3 otherwise zero. Both s1 and s3 may be NULL and
+ * in this case only non-null strings are compared. This allows to pass initial
+ * values in iterators and in sort functions.
+ */
+int strordered(const char *s1, const char *s2, const char *s3)
+{
+	return (!s1 || strcmp(s1, s2) < 0) && (!s3 || strcmp(s2, s3) < 0);
+}
+
 /* This function read the next valid utf8 char.
  * <s> is the byte srray to be decode, <len> is its length.
  * The function returns decoded char encoded like this: