59 lines
2.3 KiB
Text
59 lines
2.3 KiB
Text
=pod
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=head1 NAME
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SSL_pending, SSL_has_pending - check for readable bytes buffered in an
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SSL object
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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int SSL_pending(const SSL *ssl);
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int SSL_has_pending(const SSL *s);
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=head1 DESCRIPTION
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Data is received in whole blocks known as records from the peer. A whole record
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is processed (e.g. decrypted) in one go and is buffered by OpenSSL until it is
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read by the application via a call to L<SSL_read(3)>.
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SSL_pending() returns the number of bytes which have been processed, buffered
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and are available inside B<ssl> for immediate read.
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If the B<SSL> object's I<read_ahead> flag is set (see
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L<SSL_CTX_set_read_ahead(3)>), additional protocol bytes (beyond the current
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record) may have been read containing more TLS/SSL records. This also applies to
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DTLS and pipelining (see L<SSL_CTX_set_split_send_fragment(3)>). These
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additional bytes will be buffered by OpenSSL but will remain unprocessed until
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they are needed. As these bytes are still in an unprocessed state SSL_pending()
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will ignore them. Therefore it is possible for no more bytes to be readable from
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the underlying BIO (because OpenSSL has already read them) and for SSL_pending()
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to return 0, even though readable application data bytes are available (because
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the data is in unprocessed buffered records).
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SSL_has_pending() returns 1 if B<s> has buffered data (whether processed or
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unprocessed) and 0 otherwise. Note that it is possible for SSL_has_pending() to
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return 1, and then a subsequent call to SSL_read() to return no data because the
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unprocessed buffered data when processed yielded no application data (for
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example this can happen during renegotiation). It is also possible in this
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scenario for SSL_has_pending() to continue to return 1 even after an SSL_read()
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call because the buffered and unprocessed data is not yet processable (e.g.
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because OpenSSL has only received a partial record so far).
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=head1 RETURN VALUES
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SSL_pending() returns the number of buffered and processed application data
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bytes that are pending and are available for immediate read. SSL_has_pending()
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returns 1 if there is buffered record data in the SSL object and 0 otherwise.
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=head1 SEE ALSO
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L<SSL_read(3)>, L<SSL_CTX_set_read_ahead(3)>,
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L<SSL_CTX_set_split_send_fragment(3)>, L<ssl(3)>
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=head1 HISTORY
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The SSL_has_pending() function was added in OpenSSL 1.1.0.
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=cut
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