Function tcp_stats_sample_rollthedice

freebsd/netinet/tcp_stats.c:186–212

#ifdef _KERNEL
int
tcp_stats_sample_rollthedice(struct tcpcb *tp, void *seed_bytes,
    size_t seed_len)
{
	struct rm_priotracker tracker;
	int tpl;

	tpl = -1;

	if (V_tcp_stats_nrates > 0) {
		rm_rlock(&tcp_stats_tpl_sampling_lock, &tracker);
		tpl = stats_tpl_sample_rollthedice(V_tcp_perconn_stats_sample_rates,
		    V_tcp_stats_nrates, seed_bytes, seed_len);
		rm_runlock(&tcp_stats_tpl_sampling_lock, &tracker);

		if (tpl >= 0) {
			INP_WLOCK_ASSERT(tp->t_inpcb);
			if (tp->t_stats != NULL)
				stats_blob_destroy(tp->t_stats);
			tp->t_stats = stats_blob_alloc(tpl, 0);
			if (tp->t_stats == NULL)
				tpl = -ENOMEM;
		}
	}

	return (tpl);
}

/*
 * Callback function for stats_tpl_sample_rates() to interact with the TCP