Function bbr_alloc

freebsd/netinet/tcp_stacks/bbr.c:3291–3311

* Allocate a sendmap from our zone. */

 * Allocate a sendmap from our zone.
 */
static struct bbr_sendmap *
bbr_alloc(struct tcp_bbr *bbr)
{
	struct bbr_sendmap *rsm;

	BBR_STAT_INC(bbr_to_alloc);
	rsm = uma_zalloc(bbr_zone, (M_NOWAIT | M_ZERO));
	if (rsm) {
		bbr->r_ctl.rc_num_maps_alloced++;
		return (rsm);
	}
	if (bbr->r_ctl.rc_free_cnt) {
		BBR_STAT_INC(bbr_to_alloc_emerg);
		rsm = TAILQ_FIRST(&bbr->r_ctl.rc_free);
		TAILQ_REMOVE(&bbr->r_ctl.rc_free, rsm, r_next);
		bbr->r_ctl.rc_free_cnt--;
		return (rsm);
	}
	BBR_STAT_INC(bbr_to_alloc_failed);
	return (NULL);
}

static struct bbr_sendmap *
bbr_alloc_full_limit(struct tcp_bbr *bbr)