Function tcp_log_event_

freebsd/netinet/tcp_log_buf.c:1519–1739

 */

struct tcp_log_buffer *
tcp_log_event_(struct tcpcb *tp, struct tcphdr *th, struct sockbuf *rxbuf,
    struct sockbuf *txbuf, uint8_t eventid, int errornum, uint32_t len,
    union tcp_log_stackspecific *stackinfo, int th_hostorder,
    const char *output_caller, const char *func, int line, const struct timeval *itv)
{
	struct tcp_log_mem *log_entry;
	struct tcp_log_buffer *log_buf;
	int attempt_count = 0;
	struct tcp_log_verbose *log_verbose;
	uint32_t logsn;

	KASSERT((func == NULL && line == 0) || (func != NULL && line > 0),
	    ("%s called with inconsistent func (%p) and line (%d) arguments",
		__func__, func, line));

	INP_WLOCK_ASSERT(tp->t_inpcb);
	if (tcp_disable_all_bb_logs) {
		/*
		 * The global shutdown logging
		 * switch has been thrown. Call
		 * the purge function that frees
		 * purges out the logs and
		 * turns off logging.
		 */
		tcp_log_purge_tp_logbuf(tp);
		return (NULL);
	}
	KASSERT(tp->t_logstate == TCP_LOG_STATE_HEAD ||
	    tp->t_logstate == TCP_LOG_STATE_TAIL ||
	    tp->t_logstate == TCP_LOG_STATE_CONTINUAL ||
	    tp->t_logstate == TCP_LOG_STATE_HEAD_AUTO ||
	    tp->t_logstate == TCP_LOG_STATE_TAIL_AUTO,
	    ("%s called with unexpected tp->t_logstate (%d)", __func__,
		tp->t_logstate));

	/*
	 * Get the serial number. We do this early so it will
	 * increment even if we end up skipping the log entry for some
	 * reason.
	 */
	logsn = tp->t_logsn++;

	/*
	 * Can we get a new log entry? If so, increment the lognum counter
	 * here.
	 */
retry:
	if (tp->t_lognum < tp->t_loglimit) {
		if ((log_entry = uma_zalloc(tcp_log_zone, M_NOWAIT)) != NULL)
			tp->t_lognum++;
	} else
		log_entry = NULL;

	/* Do we need to try to reuse? */
	if (log_entry == NULL) {
		/*
		 * Sacrifice auto-logged sessions without a log ID if