SSL_pending.3ossl 6.9 KB

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  133. .\" ========================================================================
  134. .\"
  135. .IX Title "SSL_PENDING 3ossl"
  136. .TH SSL_PENDING 3ossl "2024-09-03" "3.3.2" "OpenSSL"
  137. .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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  139. .if n .ad l
  140. .nh
  141. .SH "NAME"
  142. SSL_pending, SSL_has_pending \- check for readable bytes buffered in an
  143. SSL object
  144. .SH "SYNOPSIS"
  145. .IX Header "SYNOPSIS"
  146. .Vb 1
  147. \& #include <openssl/ssl.h>
  148. \&
  149. \& int SSL_pending(const SSL *ssl);
  150. \& int SSL_has_pending(const SSL *s);
  151. .Ve
  152. .SH "DESCRIPTION"
  153. .IX Header "DESCRIPTION"
  154. Data is received in whole blocks known as records from the peer. A whole record
  155. is processed (e.g. decrypted) in one go and is buffered by OpenSSL until it is
  156. read by the application via a call to \fBSSL_read_ex\fR\|(3) or \fBSSL_read\fR\|(3).
  157. .PP
  158. \&\fBSSL_pending()\fR returns the number of bytes which have been processed, buffered
  159. and are available inside \fBssl\fR for immediate read.
  160. .PP
  161. If the \fB\s-1SSL\s0\fR object's \fIread_ahead\fR flag is set (see
  162. \&\fBSSL_CTX_set_read_ahead\fR\|(3)), additional protocol bytes (beyond the current
  163. record) may have been read containing more \s-1TLS/SSL\s0 records. This also applies to
  164. \&\s-1DTLS\s0 and pipelining (see \fBSSL_CTX_set_split_send_fragment\fR\|(3)). These
  165. additional bytes will be buffered by OpenSSL but will remain unprocessed until
  166. they are needed. As these bytes are still in an unprocessed state \fBSSL_pending()\fR
  167. will ignore them. Therefore, it is possible for no more bytes to be readable from
  168. the underlying \s-1BIO\s0 (because OpenSSL has already read them) and for \fBSSL_pending()\fR
  169. to return 0, even though readable application data bytes are available (because
  170. the data is in unprocessed buffered records).
  171. .PP
  172. \&\fBSSL_has_pending()\fR returns 1 if \fBs\fR has buffered data (whether processed or
  173. unprocessed) and 0 otherwise. Note that it is possible for \fBSSL_has_pending()\fR to
  174. return 1, and then a subsequent call to \fBSSL_read_ex()\fR or \fBSSL_read()\fR to return no
  175. data because the unprocessed buffered data when processed yielded no application
  176. data (for example this can happen during renegotiation). It is also possible in
  177. this scenario for \fBSSL_has_pending()\fR to continue to return 1 even after an
  178. \&\fBSSL_read_ex()\fR or \fBSSL_read()\fR call because the buffered and unprocessed data is
  179. not yet processable (e.g. because OpenSSL has only received a partial record so
  180. far).
  181. .SH "RETURN VALUES"
  182. .IX Header "RETURN VALUES"
  183. \&\fBSSL_pending()\fR returns the number of buffered and processed application data
  184. bytes that are pending and are available for immediate read. \fBSSL_has_pending()\fR
  185. returns 1 if there is buffered record data in the \s-1SSL\s0 object and 0 otherwise.
  186. .SH "SEE ALSO"
  187. .IX Header "SEE ALSO"
  188. \&\fBSSL_read_ex\fR\|(3), \fBSSL_read\fR\|(3), \fBSSL_CTX_set_read_ahead\fR\|(3),
  189. \&\fBSSL_CTX_set_split_send_fragment\fR\|(3), \fBssl\fR\|(7)
  190. .SH "HISTORY"
  191. .IX Header "HISTORY"
  192. The \fBSSL_has_pending()\fR function was added in OpenSSL 1.1.0.
  193. .SH "COPYRIGHT"
  194. .IX Header "COPYRIGHT"
  195. Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved.
  196. .PP
  197. Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use
  198. this file except in compliance with the License. You can obtain a copy
  199. in the file \s-1LICENSE\s0 in the source distribution or at
  200. <https://www.openssl.org/source/license.html>.