1 files changed, 94 insertions, 0 deletions
diff --git a/lib/cache/knot_pkt.c b/lib/cache/knot_pkt.c
new file mode 100644
index 0000000..31fa7e9
--- /dev/null
+++ b/lib/cache/knot_pkt.c
@@ -0,0 +1,94 @@
+/*  Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ *  SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+/** @file
+ * Implementation of preparing knot_pkt_t for filling with RRs.
+ * Prototypes in ./impl.h
+ */
+
+#include "lib/cache/impl.h"
+
+int pkt_renew(knot_pkt_t *pkt, const knot_dname_t *name, uint16_t type)
+{
+	/* Update packet question if needed. */
+	if (!knot_dname_is_equal(knot_pkt_qname(pkt), name)
+	    || knot_pkt_qtype(pkt) != type || knot_pkt_qclass(pkt) != KNOT_CLASS_IN) {
+		int ret = kr_pkt_recycle(pkt);
+		if (ret) return kr_error(ret);
+		ret = knot_pkt_put_question(pkt, name, KNOT_CLASS_IN, type);
+		if (ret) return kr_error(ret);
+	}
+
+	pkt->parsed = pkt->size = KR_PKT_SIZE_NOWIRE;
+	knot_wire_set_qr(pkt->wire);
+	knot_wire_set_aa(pkt->wire);
+	return kr_ok();
+}
+
+/** Reserve space for additional `count` RRsets.
+ * \note pkt->rr_info gets correct length but is always zeroed
+ */
+static int pkt_alloc_space(knot_pkt_t *pkt, int count)
+{
+	size_t allocd_orig = pkt->rrset_allocd;
+	if (pkt->rrset_count + count <= allocd_orig) {
+		return kr_ok();
+	}
+	/* A simple growth strategy, amortized O(count). */
+	pkt->rrset_allocd = MAX(
+			pkt->rrset_count + count,
+			pkt->rrset_count + allocd_orig);
+
+	pkt->rr = mm_realloc(&pkt->mm, pkt->rr,
+				sizeof(pkt->rr[0]) * pkt->rrset_allocd,
+				sizeof(pkt->rr[0]) * allocd_orig);
+	if (!pkt->rr) {
+		return kr_error(ENOMEM);
+	}
+	/* Allocate pkt->rr_info to be certain, but just leave it zeroed. */
+	mm_free(&pkt->mm, pkt->rr_info);
+	pkt->rr_info = mm_calloc(&pkt->mm, pkt->rrset_allocd, sizeof(pkt->rr_info[0]));
+	if (!pkt->rr_info) {
+		return kr_error(ENOMEM);
+	}
+	return kr_ok();
+}
+
+int pkt_append(knot_pkt_t *pkt, const struct answer_rrset *rrset, uint8_t rank)
+{
+	/* allocate space, to be sure */
+	int rrset_cnt = (rrset->set.rr->rrs.count > 0) + (rrset->sig_rds.count > 0);
+	int ret = pkt_alloc_space(pkt, rrset_cnt);
+	if (ret) return kr_error(ret);
+	/* write both sets */
+	const knot_rdataset_t *rdss[2] = { &rrset->set.rr->rrs, &rrset->sig_rds };
+	for (int i = 0; i < rrset_cnt; ++i) {
+		if (kr_fails_assert(rdss[i]->count))
+			return kr_error(EINVAL);
+		/* allocate rank */
+		uint8_t *rr_rank = mm_alloc(&pkt->mm, sizeof(*rr_rank));
+		if (!rr_rank) return kr_error(ENOMEM);
+		*rr_rank = (i == 0) ? rank : (KR_RANK_OMIT | KR_RANK_AUTH);
+			/* rank for RRSIGs isn't really useful: ^^ */
+		if (i == 0) {
+			pkt->rr[pkt->rrset_count] = *rrset->set.rr;
+			pkt->rr[pkt->rrset_count].additional = rr_rank;
+		} else {
+		/* append the RR array */
+			pkt->rr[pkt->rrset_count] = (knot_rrset_t){
+				.owner = knot_dname_copy(rrset->set.rr->owner, &pkt->mm),
+					/* ^^ well, another copy isn't really needed */
+				.ttl = rrset->set.rr->ttl,
+				.type = KNOT_RRTYPE_RRSIG,
+				.rclass = KNOT_CLASS_IN,
+				.rrs = *rdss[i],
+				.additional = rr_rank,
+			};
+		}
+		++pkt->rrset_count;
+		++(pkt->sections[pkt->current].count);
+	}
+	return kr_ok();
+}
+