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Diffstat (limited to 'secure/lib/libcrypto/man/SSL_shutdown.3')
| -rw-r--r-- | secure/lib/libcrypto/man/SSL_shutdown.3 | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/secure/lib/libcrypto/man/SSL_shutdown.3 b/secure/lib/libcrypto/man/SSL_shutdown.3 new file mode 100644 index 0000000..5a6b8fd --- /dev/null +++ b/secure/lib/libcrypto/man/SSL_shutdown.3 @@ -0,0 +1,237 @@ +.\" Automatically generated by Pod::Man version 1.15 +.\" Thu May 9 13:21:43 2002 +.\" +.\" Standard preamble: +.\" ====================================================================== +.de Sh \" Subsection heading +.br +.if t .Sp +.ne 5 +.PP +\fB\\$1\fR +.PP +.. +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Ip \" List item +.br +.ie \\n(.$>=3 .ne \\$3 +.el .ne 3 +.IP "\\$1" \\$2 +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R + +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. | will give a +.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used +.\" to do unbreakable dashes and therefore won't be available. \*(C` and +.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<> +.tr \(*W-|\(bv\*(Tr +.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' +.ie n \{\ +. ds -- \(*W- +. ds PI pi +. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch +. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch +. ds L" "" +. ds R" "" +. ds C` "" +. ds C' "" +'br\} +.el\{\ +. ds -- \|\(em\| +. ds PI \(*p +. ds L" `` +. ds R" '' +'br\} +.\" +.\" If the F register is turned on, we'll generate index entries on stderr +.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and +.\" index entries marked with X<> in POD. Of course, you'll have to process +.\" the output yourself in some meaningful fashion. +.if \nF \{\ +. de IX +. tm Index:\\$1\t\\n%\t"\\$2" +.. +. nr % 0 +. rr F +.\} +.\" +.\" For nroff, turn off justification. Always turn off hyphenation; it +.\" makes way too many mistakes in technical documents. +.hy 0 +.if n .na +.\" +.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). +.\" Fear. Run. Save yourself. 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It sends the +\&\*(L"close notify\*(R" shutdown alert to the peer. +.SH "NOTES" +.IX Header "NOTES" +\&\fISSL_shutdown()\fR tries to send the \*(L"close notify\*(R" shutdown alert to the peer. +Whether the operation succeeds or not, the \s-1SSL_SENT_SHUTDOWN\s0 flag is set and +a currently open session is considered closed and good and will be kept in the +session cache for further reuse. +.PP +The shutdown procedure consists of 2 steps: the sending of the \*(L"close notify\*(R" +shutdown alert and the reception of the peer's \*(L"close notify\*(R" shutdown +alert. According to the \s-1TLS\s0 standard, it is acceptable for an application +to only send its shutdown alert and then close the underlying connection +without waiting for the peer's response (this way resources can be saved, +as the process can already terminate or serve another connection). +When the underlying connection shall be used for more communications, the +complete shutdown procedure (bidirectional \*(L"close notify\*(R" alerts) must be +performed, so that the peers stay synchronized. +.PP +\&\fISSL_shutdown()\fR supports both uni- and bidirectional shutdown by its 2 step +behaviour. +.if n .Ip "When the application is the first party to send the """"close notify"""" alert, \fISSL_shutdown()\fR 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). \fISSL_shutdown()\fR will then return with 0. If a unidirectional shutdown is enough (the underlying connection shall be closed anyway), this first call to \fISSL_shutdown()\fR is sufficient. In order to complete the bidirectional shutdown handshake, \fISSL_shutdown()\fR must be called again. The second call will make \fISSL_shutdown()\fR wait for the peer's """"close notify"""" shutdown alert. On success, the second call to \fISSL_shutdown()\fR will return with 1." 4 +.el .Ip "When the application is the first party to send the ``close notify'' alert, \fISSL_shutdown()\fR 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). \fISSL_shutdown()\fR will then return with 0. If a unidirectional shutdown is enough (the underlying connection shall be closed anyway), this first call to \fISSL_shutdown()\fR is sufficient. In order to complete the bidirectional shutdown handshake, \fISSL_shutdown()\fR must be called again. The second call will make \fISSL_shutdown()\fR wait for the peer's ``close notify'' shutdown alert. On success, the second call to \fISSL_shutdown()\fR will return with 1." 4 +.IX Item "When the application is the first party to send the "close notify alert, SSL_shutdown() will only send the alert and the set the SSL_SENT_SHUTDOWN 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 close notify shutdown alert. On success, the second call to SSL_shutdown() will return with 1." +.PD 0 +.if n .Ip "If the peer already sent the """"close notify"""" alert \fBand\fR it was already processed implicitly inside another function (SSL_read(3)), the \s-1SSL_RECEIVED_SHUTDOWN\s0 flag is set. \fISSL_shutdown()\fR will send the """"close notify"""" 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 \fISSL_get_shutdown()\fR (see also SSL_set_shutdown(3) call." 4 +.el .Ip "If the peer already sent the ``close notify'' alert \fBand\fR it was already processed implicitly inside another function (SSL_read(3)), the \s-1SSL_RECEIVED_SHUTDOWN\s0 flag is set. \fISSL_shutdown()\fR will send the ``close notify'' 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 \fISSL_get_shutdown()\fR (see also SSL_set_shutdown(3) call." 4 +.IX Item "If the peer already sent the "close notify alert and it was already processed implicitly inside another function (SSL_read(3)), the SSL_RECEIVED_SHUTDOWN flag is set. SSL_shutdown() will send the close notify alert, set the SSL_SENT_SHUTDOWN flag and will immediately return with 1. Whether SSL_RECEIVED_SHUTDOWN is already set can be checked using the SSL_get_shutdown() (see also SSL_set_shutdown(3) call." +.PD +.PP +It is therefore recommended, to check the return value of \fISSL_shutdown()\fR +and call \fISSL_shutdown()\fR again, if the bidirectional shutdown is not yet +complete (return value of the first call is 0). As the shutdown is not +specially handled in the SSLv2 protocol, \fISSL_shutdown()\fR will succeed on +the first call. +.PP +The behaviour of \fISSL_shutdown()\fR additionally depends on the underlying \s-1BIO\s0. +.PP +If the underlying \s-1BIO\s0 is \fBblocking\fR, \fISSL_shutdown()\fR will only return once the +handshake step has been finished or an error occurred. +.PP +If the underlying \s-1BIO\s0 is \fBnon-blocking\fR, \fISSL_shutdown()\fR will also return +when the underlying \s-1BIO\s0 could not satisfy the needs of \fISSL_shutdown()\fR +to continue the handshake. In this case a call to \fISSL_get_error()\fR with the +return value of \fISSL_shutdown()\fR will yield \fB\s-1SSL_ERROR_WANT_READ\s0\fR or +\&\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR. The calling process then must repeat the call after +taking appropriate action to satisfy the needs of \fISSL_shutdown()\fR. +The action depends on the underlying \s-1BIO\s0. When using a non-blocking socket, +nothing is to be done, but \fIselect()\fR can be used to check for the required +condition. When using a buffering \s-1BIO\s0, like a \s-1BIO\s0 pair, data must be written +into or retrieved out of the \s-1BIO\s0 before being able to continue. +.PP +\&\fISSL_shutdown()\fR can be modified to only set the connection to \*(L"shutdown\*(R" +state but not actually send the \*(L"close notify\*(R" alert messages, +see SSL_CTX_set_quiet_shutdown(3). +When \*(L"quiet shutdown\*(R" is enabled, \fISSL_shutdown()\fR will always succeed +and return 1. +.SH "RETURN VALUES" +.IX Header "RETURN VALUES" +The following return values can occur: +.Ip "1" 4 +.IX Item "1" +The shutdown was successfully completed. The \*(L"close notify\*(R" alert was sent +and the peer's \*(L"close notify\*(R" alert was received. +.Ip "0" 4 +The shutdown is not yet finished. Call \fISSL_shutdown()\fR for a second time, +if a bidirectional shutdown shall be performed. +The output of SSL_get_error(3) may be misleading, as an +erroneous \s-1SSL_ERROR_SYSCALL\s0 may be flagged even though no error occurred. +.Ip "\-1" 4 +.IX Item "-1" +The shutdown was not successful because a fatal error occurred either +at the protocol level or a connection failure occurred. It can also occur if +action is need to continue the operation for non-blocking BIOs. +Call SSL_get_error(3) with the return value \fBret\fR +to find out the reason. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +SSL_get_error(3), SSL_connect(3), +SSL_accept(3), SSL_set_shutdown(3), +SSL_CTX_set_quiet_shutdown(3), +SSL_clear(3), SSL_free(3), +ssl(3), bio(3) |
