SSL_set_num_tickets, SSL_get_num_tickets, SSL_CTX_set_num_tickets, SSL_CTX_get_num_tickets - control the number of TLSv1.3 session tickets that are issued
#include <openssl/ssl.h> int SSL_set_num_tickets(SSL *s, size_t num_tickets); size_t SSL_get_num_tickets(SSL *s); int SSL_CTX_set_num_tickets(SSL_CTX *ctx, size_t num_tickets); size_t SSL_CTX_get_num_tickets(SSL_CTX *ctx);
SSL_CTX_set_num_tickets() and SSL_set_num_tickets() can be called for a server application and set the number of TLSv1.3 session tickets that will be sent to the client after a full handshake. Set the desired value (which could be 0) in the num_tickets argument. Typically these functions should be called before the start of the handshake.
The default number of tickets is 2. Following a resumption the number of tickets issued will never be more than 1 regardless of the value set via SSL_set_num_tickets() or SSL_CTX_set_num_tickets(). If num_tickets is set to 0 then no tickets will be issued for either a normal connection or a resumption.
Tickets are also issued on receipt of a post-handshake certificate from the client following a request by the server using SSL_verify_client_post_handshake(3). These new tickets will be associated with the updated client identity (i.e. including their certificate and verification status). The number of tickets issued will normally be the same as was used for the initial handshake. If the initial handshake was a full handshake then SSL_set_num_tickets() can be called again prior to calling SSL_verify_client_post_handshake() to update the number of tickets that will be sent.
SSL_CTX_get_num_tickets() and SSL_get_num_tickets() return the number of tickets set by a previous call to SSL_CTX_set_num_tickets() or SSL_set_num_tickets(), or 2 if no such call has been made.
SSL_CTX_set_num_tickets() and SSL_set_num_tickets() return 1 on success or 0 on failure.
SSL_CTX_get_num_tickets() and SSL_get_num_tickets() return the number of tickets that have been previously set.
These functions were added in OpenSSL 1.1.1.
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