Add mbedtls_x509_crt_parse_cn_inet_pton() tests
Extended from https://github.com/Mbed-TLS/mbedtls/pull/2906
contributed by Eugene K <eugene.kobyakov@netfoundry.io>
Signed-off-by: Glenn Strauss <gstrauss@gluelogic.com>
diff --git a/library/x509_invasive.h b/library/x509_invasive.h
new file mode 100644
index 0000000..d8fd74b
--- /dev/null
+++ b/library/x509_invasive.h
@@ -0,0 +1,53 @@
+/**
+ * \file x509_invasive.h
+ *
+ * \brief x509 module: interfaces for invasive testing only.
+ *
+ * The interfaces in this file are intended for testing purposes only.
+ * They SHOULD NOT be made available in library integrations except when
+ * building the library for testing.
+ */
+/*
+ * Copyright The Mbed TLS Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MBEDTLS_X509_INVASIVE_H
+#define MBEDTLS_X509_INVASIVE_H
+
+#include "common.h"
+
+#if defined(MBEDTLS_TEST_HOOKS)
+
+/**
+ * \brief This function parses a CN string as an IP address.
+ *
+ * \param cn The CN string to parse. CN string MUST be NUL-terminated.
+ * \param dst The target buffer to populate with the binary IP address.
+ * The buffer MUST be 16 bytes to save IPv6, and should be
+ * 4-byte aligned if the result will be used as struct in_addr.
+ * e.g. uint32_t dst[4]
+ *
+ * \note \cn is parsed as an IPv6 address if string contains ':',
+ * else \cn is parsed as an IPv4 address.
+ *
+ * \return Length of binary IP address; num bytes written to target.
+ * \return \c 0 on failure to parse CN string as an IP address.
+ */
+size_t mbedtls_x509_crt_parse_cn_inet_pton(const char *cn, void *dst);
+
+#endif /* MBEDTLS_TEST_HOOKS */
+
+#endif /* MBEDTLS_X509_INVASIVE_H */