Remove my local patch again, it was still not meant to be commited.
[dragonfly.git] / secure / lib / libssl / man / SSL_shutdown.3
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80.\" If the F register is turned on, we'll generate
81.\" index entries out stderr for the following things:
82.\" TH Title
83.\" SH Header
84.\" Sh Subsection
85.\" Ip Item
86.\" X<> Xref (embedded
87.\" Of course, you have to process the output yourself
88.\" in some meaninful fashion.
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96.TH SSL_shutdown 3 "0.9.7d" "2/Sep/2004" "OpenSSL"
97.UC
98.if n .hy 0
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188.\}
189.rm #[ #] #H #V #F C
984263bc 190.SH "NAME"
a7d27d5a 191SSL_shutdown \- shut down a TLS/SSL connection
984263bc 192.SH "SYNOPSIS"
a7d27d5a 193.PP
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194.Vb 1
195\& #include <openssl/ssl.h>
196.Ve
197.Vb 1
198\& int SSL_shutdown(SSL *ssl);
199.Ve
200.SH "DESCRIPTION"
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201\fISSL_shutdown()\fR shuts down an active TLS/SSL connection. It sends the
202\*(L"close notify\*(R" shutdown alert to the peer.
984263bc 203.SH "NOTES"
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204\fISSL_shutdown()\fR tries to send the \*(L"close notify\*(R" shutdown alert to the peer.
205Whether the operation succeeds or not, the SSL_SENT_SHUTDOWN flag is set and
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206a currently open session is considered closed and good and will be kept in the
207session cache for further reuse.
208.PP
209The shutdown procedure consists of 2 steps: the sending of the \*(L"close notify\*(R"
210shutdown alert and the reception of the peer's \*(L"close notify\*(R" shutdown
a7d27d5a 211alert. According to the TLS standard, it is acceptable for an application
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212to only send its shutdown alert and then close the underlying connection
213without waiting for the peer's response (this way resources can be saved,
214as the process can already terminate or serve another connection).
215When the underlying connection shall be used for more communications, the
216complete shutdown procedure (bidirectional \*(L"close notify\*(R" alerts) must be
217performed, so that the peers stay synchronized.
218.PP
a7d27d5a 219\fISSL_shutdown()\fR supports both uni- and bidirectional shutdown by its 2 step
984263bc 220behaviour.
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221.Ip "When the application is the first party to send the \*(N"close notify\*(T" alert, SSL_shutdown() will only send the alert and the set the \s-1SSL_SENT_SHUTDOWN\s0 flag (so that the session is considered good and will be kept in cache). SSL_shutdown() will then return with 0. If a unidirectional shutdown is enough (the underlying connection shall be closed anyway), this first call to SSL_shutdown() is sufficient. In order to complete the bidirectional shutdown handshake, SSL_shutdown() must be called again. The second call will make SSL_shutdown() wait for the peer's \*(N"close notify\*(T" shutdown alert. On success, the second call to SSL_shutdown() will return with 1." 4
222.Ip "If the peer already sent the \*(N"close notify\*(T" alert \fBand\fR it was already processed implicitly inside another function (SSL_read(3)), the \s-1SSL_RECEIVED_SHUTDOWN\s0 flag is set. SSL_shutdown() will send the \*(N"close notify\*(T" alert, set the \s-1SSL_SENT_SHUTDOWN\s0 flag and will immediately return with 1. Whether \s-1SSL_RECEIVED_SHUTDOWN\s0 is already set can be checked using the SSL_get_shutdown() (see also SSL_set_shutdown(3) call." 4
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223.PP
224It is therefore recommended, to check the return value of \fISSL_shutdown()\fR
225and call \fISSL_shutdown()\fR again, if the bidirectional shutdown is not yet
226complete (return value of the first call is 0). As the shutdown is not
227specially handled in the SSLv2 protocol, \fISSL_shutdown()\fR will succeed on
228the first call.
229.PP
230The behaviour of \fISSL_shutdown()\fR additionally depends on the underlying \s-1BIO\s0.
231.PP
232If the underlying \s-1BIO\s0 is \fBblocking\fR, \fISSL_shutdown()\fR will only return once the
233handshake step has been finished or an error occurred.
234.PP
235If the underlying \s-1BIO\s0 is \fBnon-blocking\fR, \fISSL_shutdown()\fR will also return
236when the underlying \s-1BIO\s0 could not satisfy the needs of \fISSL_shutdown()\fR
237to continue the handshake. In this case a call to \fISSL_get_error()\fR with the
238return value of \fISSL_shutdown()\fR will yield \fB\s-1SSL_ERROR_WANT_READ\s0\fR or
a7d27d5a 239\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR. The calling process then must repeat the call after
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240taking appropriate action to satisfy the needs of \fISSL_shutdown()\fR.
241The action depends on the underlying \s-1BIO\s0. When using a non-blocking socket,
242nothing is to be done, but \fIselect()\fR can be used to check for the required
243condition. When using a buffering \s-1BIO\s0, like a \s-1BIO\s0 pair, data must be written
244into or retrieved out of the \s-1BIO\s0 before being able to continue.
245.PP
a7d27d5a 246\fISSL_shutdown()\fR can be modified to only set the connection to \*(L"shutdown\*(R"
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247state but not actually send the \*(L"close notify\*(R" alert messages,
248see SSL_CTX_set_quiet_shutdown(3).
249When \*(L"quiet shutdown\*(R" is enabled, \fISSL_shutdown()\fR will always succeed
250and return 1.
251.SH "RETURN VALUES"
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252The following return values can occur:
253.Ip "1" 4
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254The shutdown was successfully completed. The \*(L"close notify\*(R" alert was sent
255and the peer's \*(L"close notify\*(R" alert was received.
256.Ip "0" 4
257The shutdown is not yet finished. Call \fISSL_shutdown()\fR for a second time,
258if a bidirectional shutdown shall be performed.
259The output of SSL_get_error(3) may be misleading, as an
260erroneous \s-1SSL_ERROR_SYSCALL\s0 may be flagged even though no error occurred.
a7d27d5a 261.Ip "-1" 4
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262The shutdown was not successful because a fatal error occurred either
263at the protocol level or a connection failure occurred. It can also occur if
264action is need to continue the operation for non-blocking BIOs.
265Call SSL_get_error(3) with the return value \fBret\fR
266to find out the reason.
267.SH "SEE ALSO"
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268SSL_get_error(3), SSL_connect(3),
269SSL_accept(3), SSL_set_shutdown(3),
270SSL_CTX_set_quiet_shutdown(3),
271SSL_clear(3), SSL_free(3),
272ssl(3), bio(3)
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273
274.rn }` ''
275.IX Title "SSL_shutdown 3"
276.IX Name "SSL_shutdown - shut down a TLS/SSL connection"
277
278.IX Header "NAME"
279
280.IX Header "SYNOPSIS"
281
282.IX Header "DESCRIPTION"
283
284.IX Header "NOTES"
285
286.IX Item "When the application is the first party to send the \*(N"close notify\*(T" alert, SSL_shutdown() will only send the alert and the set the \s-1SSL_SENT_SHUTDOWN\s0 flag (so that the session is considered good and will be kept in cache). SSL_shutdown() will then return with 0. If a unidirectional shutdown is enough (the underlying connection shall be closed anyway), this first call to SSL_shutdown() is sufficient. In order to complete the bidirectional shutdown handshake, SSL_shutdown() must be called again. The second call will make SSL_shutdown() wait for the peer's \*(N"close notify\*(T" shutdown alert. On success, the second call to SSL_shutdown() will return with 1."
287
288.IX Item "If the peer already sent the \*(N"close notify\*(T" alert \fBand\fR it was already processed implicitly inside another function (SSL_read(3)), the \s-1SSL_RECEIVED_SHUTDOWN\s0 flag is set. SSL_shutdown() will send the \*(N"close notify\*(T" alert, set the \s-1SSL_SENT_SHUTDOWN\s0 flag and will immediately return with 1. Whether \s-1SSL_RECEIVED_SHUTDOWN\s0 is already set can be checked using the SSL_get_shutdown() (see also SSL_set_shutdown(3) call."
289
290.IX Header "RETURN VALUES"
291
292.IX Item "1"
293
294.IX Item "0"
295
296.IX Item "-1"
297
298.IX Header "SEE ALSO"
299