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NAME

SSL_CTX_set_mode, SSL_set_mode, SSL_CTX_clear_mode, SSL_clear_mode, SSL_CTX_get_mode, SSL_get_mode — manipulate SSL engine mode

SYNOPSIS

/* -lssl -lcrypto */
#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_clear_mode(SSL_CTX *ctx, long mode);

long
SSL_clear_mode(SSL *ssl, long mode);

long
SSL_CTX_get_mode(SSL_CTX *ctx);

long
SSL_get_mode(SSL *ssl);

DESCRIPTION

SSL_CTX_set_mode() and SSL_set_mode() enable the options contained in the bitmask mode for the ctx or ssl object, respectively. Options that were already enabled before the call are not disabled.

SSL_CTX_clear_mode() and SSL_clear_mode() disable the options contained in the bitmask mode for the ctx or ssl object.

SSL_CTX_get_mode() and SSL_get_mode() return a bitmask representing the options that are currently enabled for the ctx or ssl object.

The following options are available:

SSL_MODE_ENABLE_PARTIAL_WRITE

Allow SSL_write(..., 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).

SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER

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).

SSL_MODE_AUTO_RETRY

Never bother the application with retries if the transport is blocking. If a renegotiation takes 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.

SSL_MODE_RELEASE_BUFFERS

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.

RETURN VALUES

SSL_CTX_set_mode(), SSL_set_mode(), SSL_CTX_clear_mode(), and SSL_clear_mode() return the new mode bitmask after adding or clearing mode.

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

SEE ALSO

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

HISTORY

SSL_CTX_set_mode(), SSL_set_mode(), SSL_CTX_get_mode(), and SSL_get_mode() first appeared in OpenSSL 0.9.4 and have been available since OpenBSD 2.6.

SSL_CTX_clear_mode() and SSL_clear_mode() first appeared in OpenSSL 0.9.8m and have been available since OpenBSD 4.9.

SSL_MODE_AUTO_RETRY was added in OpenSSL 0.9.6.