Improve comments
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 7d2cff1..8cb1923 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -2303,7 +2303,9 @@
}
exit:
- /* prevent misuse of the vrfy callback */
+ /* prevent misuse of the vrfy callback - VERIFY_FAILED would be ignored by
+ * the SSL module for authmode optional, but non-zero return from the
+ * callback means a fatal error so it shouldn't be ignored */
if( ret == MBEDTLS_ERR_X509_CERT_VERIFY_FAILED )
ret = MBEDTLS_ERR_X509_FATAL_ERROR;