SSL_CTX_FLUSH_SESSIONS(3) | Library Functions Manual | SSL_CTX_FLUSH_SESSIONS(3)

# NAME

`SSL_CTX_flush_sessions` — remove expired sessions

# SYNOPSIS

library “libssl” libcrypto
`#include <openssl/ssl.h>`

void
`SSL_CTX_flush_sessions`(SSL_CTX *ctx, long tm);

# DESCRIPTION

`SSL_CTX_flush_sessions`() causes a run through the session cache of ctx to remove sessions expired at time tm.

If enabled, the internal session cache will collect all sessions established up to the specified maximum number (see SSL_CTX_sess_set_cache_size(3)). As sessions will not be reused once they are expired, they should be removed from the cache to save resources. This can either be done automatically whenever 255 new sessions were established (see SSL_CTX_set_session_cache_mode(3)) or manually by calling `SSL_CTX_flush_sessions`().

The parameter tm specifies the time which should be used for the expiration test, in most cases the actual time given by `time`(0) will be used.

`SSL_CTX_flush_sessions`() will only check sessions stored in the internal cache. When a session is found and removed, the remove_session_cb is however called to synchronize with the external cache (see SSL_CTX_sess_set_get_cb(3)).

# SEE ALSO

ssl(3), SSL_CTX_sess_set_get_cb(3), SSL_CTX_set_session_cache_mode(3), SSL_CTX_set_timeout(3)

# HISTORY

`SSL_CTX_flush_sessions`() first appeared in SSLeay 0.8.0 and has been available since OpenBSD 2.4.

June 8, 2025 | Debian