=pod

=head1 NAME

SSL_set_incoming_stream_policy, SSL_INCOMING_STREAM_POLICY_AUTO,
SSL_INCOMING_STREAM_POLICY_ACCEPT,
SSL_INCOMING_STREAM_POLICY_REJECT - manage the QUIC incoming stream
rejection policy

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 #define SSL_INCOMING_STREAM_POLICY_AUTO
 #define SSL_INCOMING_STREAM_POLICY_ACCEPT
 #define SSL_INCOMING_STREAM_POLICY_REJECT

 int SSL_set_incoming_stream_policy(SSL *conn, int policy,
                                           uint64_t app_error_code);

=head1 DESCRIPTION

SSL_set_incoming_stream_policy() policy changes the incoming stream
rejection policy for a QUIC connection. Depending on the policy configured,
OpenSSL QUIC may automatically reject incoming streams initiated by the peer.
This is intended to ensure that legacy applications using single-stream
operation with a default stream on a QUIC connection SSL object are not passed
remotely-initiated streams by a peer which those applications are not prepared
to handle.

I<app_error_code> is an application error code which will be used in any QUIC
B<STOP_SENDING> or B<RESET_STREAM> frames generated to implement the rejection
policy. The default application error code is 0.

The valid values for I<policy> are:

=over 4

=item SSL_INCOMING_STREAM_POLICY_AUTO

This is the default setting. Incoming streams are accepted according to the
following rules:

=over 4

=item *

An incoming stream is accepted if L<SSL_detach_stream(3)> has ever been called
on a QUIC connection SSL object, as the application is assumed to be
stream-aware in this case.

=item *

Otherwise, if the default stream mode (configured using
L<SSL_set_default_stream_mode(3)>) is set to
B<SSL_DEFAULT_STREAM_MODE_AUTO_BIDI> (the default) or
B<SSL_DEFAULT_STREAM_MODE_AUTO_UNI>, the incoming stream is rejected.

=item *

Otherwise (where the default stream mode is B<SSL_DEFAULT_STREAM_MODE_NONE>),
the application is assumed to be stream aware, and the incoming stream is
accepted.

=back

=item SSL_INCOMING_STREAM_POLICY_ACCEPT

Always accept incoming streams, allowing them to be dequeued using
L<SSL_accept_stream(3)>.

=item SSL_INCOMING_STREAM_POLICY_REJECT

Always reject incoming streams.

=back

Where an incoming stream is rejected, it is rejected immediately and it is not
possible to gain access to the stream using L<SSL_accept_stream(3)>. The stream
is rejected using QUIC B<STOP_SENDING> and B<RESET_STREAM> frames as
appropriate.

=head1 RETURN VALUES

Returns 1 on success and 0 on failure.

This function fails if called on a QUIC stream SSL object, or on a non-QUIC SSL
object.

=head1 SEE ALSO

L<SSL_attach_stream(3)>, L<SSL_detach_stream(3)>,
L<SSL_set_default_stream_mode(3)>, L<SSL_accept_stream(3)>

=head1 HISTORY

SSL_set_incoming_stream_policy() was added in OpenSSL 3.2.

=head1 COPYRIGHT

Copyright 2002-2023 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

=cut