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SSL_dup, SSL_new, SSL_up_ref - create an SSL structure for a connection


 #include <openssl/ssl.h>
 SSL *SSL_dup(SSL *s);
 SSL *SSL_new(SSL_CTX *ctx);
 int SSL_up_ref(SSL *s);


SSL_new() creates a new SSL structure which is needed to hold the data for a TLS/SSL connection. The new structure inherits the settings of the underlying context ctx: connection method, options, verification settings, timeout settings. An SSL structure is reference counted. Creating an SSL structure for the first time increments the reference count. Freeing it (using SSL_free) decrements it. When the reference count drops to zero, any memory or resources allocated to the SSL structure are freed.

SSL_up_ref() increments the reference count for an existing SSL structure.

The function SSL_dup() creates and returns a new SSL structure from the same SSL_CTX that was used to create s. It additionally duplicates a subset of the settings in s into the new SSL object.

For SSL_dup() to work, the connection MUST be in its initial state and MUST NOT have yet started the SSL handshake. For connections that are not in their initial state SSL_dup() just increments an internal reference count and returns the same handle. It may be possible to use SSL_clear(3) to recycle an SSL handle that is not in its initial state for re-use, but this is best avoided. Instead, save and restore the session, if desired, and construct a fresh handle for each connection.

The subset of settings in s that are duplicated are:

SSL_set_tmp_dh(3), SSL_set_tmp_dh_callback(3), or SSL_set_dh_auto(3)
SSL_set_min_proto_version(3) or SSL_set_max_proto_version(3) (Note: Only from OpenSSL 1.1.1h and above)
SSL_set_verify(3) or SSL_set_verify_depth(3) or any configured X509 verification parameters
SSL_set_msg_callback(3) or SSL_set_info_callback(3)
SSL_set0_CA_list(3), SSL_set0_client_CA_list() or similar functions


The following return values can occur:

The creation of a new SSL structure failed. Check the error stack to find out the reason.
The return value points to an allocated SSL structure.

SSL_up_ref() returns 1 for success and 0 for failure.


SSL_free(3), SSL_clear(3), SSL_CTX_set_options(3), SSL_get_SSL_CTX(3), ssl(7)


Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <>.

2021-09-11 3.0.0