1SSL_CTX_set_mode(3)                 OpenSSL                SSL_CTX_set_mode(3)
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NAME

6       SSL_CTX_set_mode, SSL_set_mode, SSL_CTX_get_mode, SSL_get_mode -
7       manipulate SSL engine mode
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SYNOPSIS

10        #include <openssl/ssl.h>
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12        long SSL_CTX_set_mode(SSL_CTX *ctx, long mode);
13        long SSL_set_mode(SSL *ssl, long mode);
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15        long SSL_CTX_get_mode(SSL_CTX *ctx);
16        long SSL_get_mode(SSL *ssl);
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DESCRIPTION

19       SSL_CTX_set_mode() adds the mode set via bitmask in mode to ctx.
20       Options already set before are not cleared.
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22       SSL_set_mode() adds the mode set via bitmask in mode to ssl.  Options
23       already set before are not cleared.
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25       SSL_CTX_get_mode() returns the mode set for ctx.
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27       SSL_get_mode() returns the mode set for ssl.
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NOTES

30       The following mode changes are available:
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32       SSL_MODE_ENABLE_PARTIAL_WRITE
33           Allow SSL_write(..., n) to return r with 0 < r < n (i.e. report
34           success when just a single record has been written). When not set
35           (the default), SSL_write() will only report success once the
36           complete chunk was written.  Once SSL_write() returns with r, r
37           bytes have been successfully written and the next call to
38           SSL_write() must only send the n-r bytes left, imitating the
39           behaviour of write().
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41       SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER
42           Make it possible to retry SSL_write() with changed buffer location
43           (the buffer contents must stay the same). This is not the default
44           to avoid the misconception that non-blocking SSL_write() behaves
45           like non-blocking write().
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47       SSL_MODE_AUTO_RETRY
48           Never bother the application with retries if the transport is
49           blocking.  If a renegotiation take place during normal operation, a
50           SSL_read(3) or SSL_write(3) would return with -1 and indicate the
51           need to retry with SSL_ERROR_WANT_READ.  In a non-blocking
52           environment applications must be prepared to handle incomplete
53           read/write operations.  In a blocking environment, applications are
54           not always prepared to deal with read/write operations returning
55           without success report. The flag SSL_MODE_AUTO_RETRY will cause
56           read/write operations to only return after the handshake and
57           successful completion.
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59       SSL_MODE_RELEASE_BUFFERS
60           When we no longer need a read buffer or a write buffer for a given
61           SSL, then release the memory we were using to hold it.  Released
62           memory is either appended to a list of unused RAM chunks on the
63           SSL_CTX, or simply freed if the list of unused chunks would become
64           longer than SSL_CTX->freelist_max_len, which defaults to 32.  Using
65           this flag can save around 34k per idle SSL connection.  This flag
66           has no effect on SSL v2 connections, or on DTLS connections.
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68       SSL_MODE_SEND_FALLBACK_SCSV
69           Send TLS_FALLBACK_SCSV in the ClientHello.  To be set only by
70           applications that reconnect with a downgraded protocol version; see
71           draft-ietf-tls-downgrade-scsv-00 for details.
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73           DO NOT ENABLE THIS if your application attempts a normal handshake.
74           Only use this in explicit fallback retries, following the guidance
75           in draft-ietf-tls-downgrade-scsv-00.
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RETURN VALUES

78       SSL_CTX_set_mode() and SSL_set_mode() return the new mode bitmask after
79       adding mode.
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81       SSL_CTX_get_mode() and SSL_get_mode() return the current bitmask.
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SEE ALSO

84       ssl(3), SSL_read(3), SSL_write(3)
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HISTORY

87       SSL_MODE_AUTO_RETRY as been added in OpenSSL 0.9.6.
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911.0.2o                            2018-03-27               SSL_CTX_set_mode(3)
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