static int s2n_advance_message()

in tls/s2n_handshake_io.c [849:895]

• 26 lines of code
• 11 McCabe index (conditional complexity)

static int s2n_advance_message(struct s2n_connection *conn)
{
    /* Get the mode: 'C'lient or 'S'erver */
    char previous_writer = ACTIVE_STATE(conn).writer;
    char this_mode = CONNECTION_WRITER(conn);

    /* Actually advance the message number */
    conn->handshake.message_number++;

    /* When reading and using TLS1.3, skip optional change_cipher_spec states. */
    if (ACTIVE_STATE(conn).writer != this_mode && EXPECTED_RECORD_TYPE(conn) == TLS_CHANGE_CIPHER_SPEC && IS_TLS13_HANDSHAKE(conn)) {
        conn->handshake.message_number++;
    }

    /* Set TCP_QUICKACK to avoid artificial delay during the handshake */
    POSIX_GUARD(s2n_socket_quickack(conn));

    /* If optimized io hasn't been enabled or if the caller started out with a corked socket,
     * we don't mess with it
     */
    if (!conn->corked_io || s2n_socket_was_corked(conn)) {
        return S2N_SUCCESS;
    }

    /* Are we changing I/O directions */
    if (ACTIVE_STATE(conn).writer == previous_writer || ACTIVE_STATE(conn).writer == 'A') {
        return S2N_SUCCESS;
    }

    /* We're the new writer */
    if (ACTIVE_STATE(conn).writer == this_mode) {
        if (s2n_connection_is_managed_corked(conn)) {
            /* Set TCP_CORK/NOPUSH */
            POSIX_GUARD(s2n_socket_write_cork(conn));
        }

        return S2N_SUCCESS;
    }

    /* We're the new reader, or we reached the "B" writer stage indicating that
       we're at the application data stage  - uncork the data */
    if (s2n_connection_is_managed_corked(conn)) {
        POSIX_GUARD(s2n_socket_write_uncork(conn));
    }

    return S2N_SUCCESS;
}