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/*
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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.
*/
#pragma once
#include <s2n.h>
/**
* @file npn.h
*
* The Next Protocol Negotiation Extension, or NPN, was an RFC proposal to
* negotiate an application protocol. This proposal was never standardized, and
* it was eventually replaced with the ALPN Extension. However, an early draft
* version of the NPN Extension was implemented in Openssl.
* Now, OpenSSL clients and servers may require this extension in order to connect.
*
* s2n-tls supports NPN to make it easier for users whose peers require this
* extension, but s2n-tls does NOT recommend its use. The specific draft version
* supported is https://datatracker.ietf.org/doc/html/draft-agl-tls-nextprotoneg-03,
* which provides interoperability with OpenSSL.
*/
/**
* Turns on support for the NPN extension.
*
* This will allow an s2n-tls client to send the NPN extension and an s2n-tls
* server to respond to receiving the NPN extension. However, if their peer
* also indicates support for the ALPN extension, s2n-tls will prefer that.
*
* Use s2n_config_append_protocol_preference() to set up a list of supported protocols.
* After the negotiation for the connection has completed, the agreed-upon protocol
* can be retrieved with s2n_get_application_protocol().
*
* @param config A pointer to the config object
* @param enable Set to true to enable. Set to false to disable.
* @returns S2N_SUCCESS on success, S2N_FAILURE on error.
*/
S2N_API int s2n_config_set_npn(struct s2n_config *config, bool enable);
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