Adding TLS 1.3 variant to SSL*.

Change-Id: I3de3c48a1de59c2b8de348253ce62a648aa6d6eb
Reviewed-on: https://boringssl-review.googlesource.com/17724
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/include/openssl/ssl.h b/include/openssl/ssl.h
index ca1e9e8..256485c 100644
--- a/include/openssl/ssl.h
+++ b/include/openssl/ssl.h
@@ -3148,6 +3148,12 @@
 OPENSSL_EXPORT void SSL_CTX_set_tls13_variant(SSL_CTX *ctx,
                                               enum tls13_variant_t variant);
 
+/* SSL_set_tls13_variant sets which variant of TLS 1.3 we negotiate. On the
+ * server, if |variant| is not |tls13_default|, all variants are enabled. On the
+ * client, only the configured variant is enabled. */
+OPENSSL_EXPORT void SSL_set_tls13_variant(SSL *ssl,
+                                          enum tls13_variant_t variant);
+
 /* SSL_MAX_CERT_LIST_DEFAULT is the default maximum length, in bytes, of a peer
  * certificate chain. */
 #define SSL_MAX_CERT_LIST_DEFAULT (1024 * 100)