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SSL_CTX_SET_MODE(3) Library Functions Manual SSL_CTX_SET_MODE(3)

SSL_CTX_set_mode, SSL_set_mode, SSL_CTX_get_mode, SSL_get_modemanipulate SSL engine mode

#include <openssl/ssl.h>

long
SSL_CTX_set_mode(SSL_CTX *ctx, long mode);

long
SSL_set_mode(SSL *ssl, long mode);

long
SSL_CTX_get_mode(SSL_CTX *ctx);

long
SSL_get_mode(SSL *ssl);

() adds the mode set via bitmask in mode to ctx. Options already set before are not cleared.

() adds the mode set via bitmask in mode to ssl. Options already set before are not cleared.

() returns the mode set for ctx.

() returns the mode set for ssl.

The following mode changes are available:

Allow (..., n) to return r with 0<r<n (i.e., report success when just a single record has been written). When not set (the default), SSL_write(3) will only report success once the complete chunk was written. Once SSL_write(3) returns with r, r bytes have been successfully written and the next call to SSL_write(3) must only send the n − r bytes left, imitating the behaviour of write(2).
Make it possible to retry SSL_write(3) with changed buffer location (the buffer contents must stay the same). This is not the default to avoid the misconception that non-blocking SSL_write(3) behaves like non-blocking write(2).
Never bother the application with retries if the transport is blocking. If a renegotiation take place during normal operation, a SSL_read(3) or SSL_write(3) would return with −1 and indicate the need to retry with SSL_ERROR_WANT_READ. In a non-blocking environment applications must be prepared to handle incomplete read/write operations. In a blocking environment, applications are not always prepared to deal with read/write operations returning without success report. The flag SSL_MODE_AUTO_RETRY will cause read/write operations to only return after the handshake and successful completion.
When we no longer need a read buffer or a write buffer for a given SSL, then release the memory we were using to hold it. Using this flag can save around 34k per idle SSL connection. This flag has no effect on SSL v2 connections, or on DTLS connections.

SSL_CTX_set_mode() and SSL_set_mode() return the new mode bitmask after adding mode.

SSL_CTX_get_mode() and SSL_get_mode() return the current bitmask.

ssl(3), SSL_read(3), SSL_write(3)

SSL_MODE_AUTO_RETRY was added in OpenSSL 0.9.6.

December 1, 2016 OpenBSD-6.1