Function rack_proc_sack_blk

freebsd/netinet/tcp_stacks/rack.c:6954–7361

}

static uint32_t
rack_proc_sack_blk(struct tcpcb *tp, struct tcp_rack *rack, struct sackblk *sack,
		   struct tcpopt *to, struct rack_sendmap **prsm, uint32_t cts, int *moved_two)
{
	uint32_t start, end, changed = 0;
	struct rack_sendmap stack_map;
	struct rack_sendmap *rsm, *nrsm, fe, *insret, *prev, *next;
	int32_t used_ref = 1;
	int moved = 0;

	start = sack->start;
	end = sack->end;
	rsm = *prsm;
	memset(&fe, 0, sizeof(fe));
do_rest_ofb:
	if ((rsm == NULL) ||
	    (SEQ_LT(end, rsm->r_start)) ||
	    (SEQ_GEQ(start, rsm->r_end)) ||
	    (SEQ_LT(start, rsm->r_start))) {
		/*
		 * We are not in the right spot,
		 * find the correct spot in the tree.
		 */
		used_ref = 0;
		fe.r_start = start;
		rsm = RB_FIND(rack_rb_tree_head, &rack->r_ctl.rc_mtree, &fe);
		moved++;
	}
	if (rsm == NULL) {
		/* TSNH */
		goto out;
	}
	/* Ok we have an ACK for some piece of this rsm */
	if (rsm->r_start != start) {
		if ((rsm->r_flags & RACK_ACKED) == 0) {
			/**
			 * Need to split this in two pieces the before and after,
			 * the before remains in the map, the after must be
			 * added. In other words we have:
			 * rsm        |--------------|
			 * sackblk        |------->
			 * rsm will become
			 *     rsm    |---|
			 * and nrsm will be  the sacked piece
			 *     nrsm       |----------|
			 *
			 * But before we start down that path lets
			 * see if the sack spans over on top of
			 * the next guy and it is already sacked.
			 */
			next = RB_NEXT(rack_rb_tree_head, &rack->r_ctl.rc_mtree, rsm);
			if (next && (next->r_flags & RACK_ACKED) &&
			    SEQ_GEQ(end, next->r_start)) {
				/**
				 * So the next one is already acked, and
				 * we can thus by hookery use our stack_map
				 * to reflect the piece being sacked and
				 * then adjust the two tree entries moving