1 files changed, 222 insertions, 0 deletions
diff --git a/lib/cache/entry_pkt.c b/lib/cache/entry_pkt.c
new file mode 100644
index 0000000..4ed2047
--- /dev/null
+++ b/lib/cache/entry_pkt.c
@@ -0,0 +1,222 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+ *  SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+/** @file
+ * Implementation of packet-caching.  Prototypes in ./impl.h
+ *
+ * The packet is stashed in entry_h::data as uint16_t length + full packet wire format.
+ */
+
+#include "lib/utils.h"
+#include "lib/layer/iterate.h" /* kr_response_classify */
+#include "lib/cache/impl.h"
+
+
+/** Compute TTL for a packet.  Generally it's minimum TTL, with extra conditions. */
+KR_EXPORT
+uint32_t packet_ttl(const knot_pkt_t *pkt, bool is_negative)
+{
+	bool has_ttl = false;
+	uint32_t ttl = UINT32_MAX;
+	/* Find minimum entry TTL in the packet or SOA minimum TTL. */
+	for (knot_section_t i = KNOT_ANSWER; i <= KNOT_ADDITIONAL; ++i) {
+		const knot_pktsection_t *sec = knot_pkt_section(pkt, i);
+		for (unsigned k = 0; k < sec->count; ++k) {
+			const knot_rrset_t *rr = knot_pkt_rr(sec, k);
+			if (is_negative) {
+				/* Use SOA minimum TTL for negative answers. */
+				if (rr->type == KNOT_RRTYPE_SOA) {
+					return MIN(rr->ttl, knot_soa_minimum(rr->rrs.rdata));
+				} else {
+					continue; /* Use SOA only for negative answers. */
+				}
+			}
+			if (knot_rrtype_is_metatype(rr->type)) {
+				continue; /* Skip metatypes. */
+			}
+			ttl = MIN(ttl, rr->ttl);
+			has_ttl = true;
+		}
+	}
+	/* If no valid TTL present, go with zero (will get clamped to minimum). */
+	return has_ttl ? ttl : 0;
+}
+
+
+void stash_pkt(const knot_pkt_t *pkt, const struct kr_query *qry,
+		const struct kr_request *req, const bool needs_pkt)
+{
+	/* In some cases, stash also the packet. */
+	const bool is_negative = kr_response_classify(pkt)
+				& (PKT_NODATA|PKT_NXDOMAIN);
+	const struct kr_qflags * const qf = &qry->flags;
+	const bool want_negative = qf->DNSSEC_INSECURE || !qf->DNSSEC_WANT;
+	const bool want_pkt = qf->DNSSEC_BOGUS /*< useful for +cd answers */
+				|| (is_negative && want_negative) || needs_pkt;
+
+	if (!want_pkt || !knot_wire_get_aa(pkt->wire)
+	    || pkt->parsed != pkt->size /*< malformed packet; still can't detect KNOT_EFEWDATA */
+	   ) {
+		return;
+	}
+
+	/* Compute rank.  If cd bit is set or we got answer via non-validated
+	 * forwarding, make the rank bad; otherwise it depends on flags.
+	 * TODO: probably make validator attempt validation even with +cd. */
+	uint8_t rank = KR_RANK_AUTH;
+	const bool risky_vldr = is_negative && qf->FORWARD && qf->CNAME;
+		/* ^^ CNAME'ed NXDOMAIN answer in forwarding mode can contain
+		 * unvalidated records; original commit: d6e22f476. */
+	if (knot_wire_get_cd(req->qsource.packet->wire) || qf->STUB || risky_vldr) {
+		kr_rank_set(&rank, KR_RANK_OMIT);
+	} else {
+		if (qf->DNSSEC_BOGUS) {
+			kr_rank_set(&rank, KR_RANK_BOGUS);
+		} else if (qf->DNSSEC_INSECURE) {
+			kr_rank_set(&rank, KR_RANK_INSECURE);
+		} else if (!qf->DNSSEC_WANT) {
+			/* no TAs at all, leave _RANK_AUTH */
+		} else if (needs_pkt) {
+			/* All bad cases should be filtered above,
+			 * at least the same way as pktcache in kresd 1.5.x. */
+			kr_rank_set(&rank, KR_RANK_SECURE);
+		} else assert(false);
+	}
+
+	const uint16_t pkt_type = knot_pkt_qtype(pkt);
+	const knot_dname_t *owner = knot_pkt_qname(pkt); /* qname can't be compressed */
+
+	// LATER: nothing exists under NXDOMAIN.  Implement that (optionally)?
+#if 0
+	if (knot_wire_get_rcode(pkt->wire) == KNOT_RCODE_NXDOMAIN
+	 /* && !qf->DNSSEC_INSECURE */ ) {
+		pkt_type = KNOT_RRTYPE_NS;
+	}
+#endif
+
+	/* Construct the key under which the pkt will be stored. */
+	struct key k_storage, *k = &k_storage;
+	knot_db_val_t key;
+	int ret = kr_dname_lf(k->buf, owner, false);
+	if (ret) {
+		/* A server might (incorrectly) reply with QDCOUNT=0. */
+		assert(owner == NULL);
+		return;
+	}
+	key = key_exact_type_maypkt(k, pkt_type);
+
+	/* For now we stash the full packet byte-exactly as it came from upstream. */
+	const uint16_t pkt_size = pkt->size;
+	knot_db_val_t val_new_entry = {
+		.data = NULL,
+		.len = offsetof(struct entry_h, data) + sizeof(pkt_size) + pkt->size,
+	};
+	/* Prepare raw memory for the new entry and fill it. */
+	struct kr_cache *cache = &req->ctx->cache;
+	ret = entry_h_splice(&val_new_entry, rank, key, k->type, pkt_type,
+				owner, qry, cache, qry->timestamp.tv_sec);
+	if (ret) return; /* some aren't really errors */
+	assert(val_new_entry.data);
+	struct entry_h *eh = val_new_entry.data;
+	memset(eh, 0, offsetof(struct entry_h, data));
+	eh->time = qry->timestamp.tv_sec;
+	eh->ttl  = MAX(MIN(packet_ttl(pkt, is_negative), cache->ttl_max), cache->ttl_min);
+	eh->rank = rank;
+	eh->is_packet = true;
+	eh->has_optout = qf->DNSSEC_OPTOUT;
+	memcpy(eh->data, &pkt_size, sizeof(pkt_size));
+	memcpy(eh->data + sizeof(pkt_size), pkt->wire, pkt_size);
+
+	WITH_VERBOSE(qry) {
+		auto_free char *type_str = kr_rrtype_text(pkt_type),
+			*owner_str = kr_dname_text(owner);
+		VERBOSE_MSG(qry, "=> stashed packet: rank 0%.2o, TTL %d, "
+				"%s %s (%d B)\n",
+				eh->rank, eh->ttl,
+				type_str, owner_str, (int)val_new_entry.len);
+	}
+}
+
+
+int answer_from_pkt(kr_layer_t *ctx, knot_pkt_t *pkt, uint16_t type,
+		const struct entry_h *eh, const void *eh_bound, uint32_t new_ttl)
+{
+	struct kr_request *req = ctx->req;
+	struct kr_query *qry = req->current_query;
+
+	const uint16_t msgid = knot_wire_get_id(pkt->wire);
+
+	/* Ensure the wire buffer is large enough.  Strategy: fit and at least double. */
+	uint16_t pkt_len;
+	memcpy(&pkt_len, eh->data, sizeof(pkt_len));
+	if (pkt_len > pkt->max_size) {
+		pkt->max_size = MIN(KNOT_WIRE_MAX_PKTSIZE,
+				    MAX(pkt->max_size * 2, pkt_len));
+		mm_free(&ctx->req->pool, pkt->wire); /* no-op, but... */
+		pkt->wire = mm_alloc(&ctx->req->pool, pkt->max_size);
+		pkt->compr.wire = pkt->wire;
+		/* TODO: ^^ nicer way how to replace knot_pkt_t::wire ? */
+	}
+	assert(pkt->max_size >= pkt_len);
+
+	/* Copy answer and reparse it, but keep the original message id. */
+	knot_pkt_clear(pkt);
+	memcpy(pkt->wire, eh->data + 2, pkt_len);
+	pkt->size = pkt_len;
+	int ret = knot_pkt_parse(pkt, 0);
+	if (ret == KNOT_EFEWDATA || ret == KNOT_EMALF) {
+		return kr_error(ENOENT);
+		/* LATER(opt): try harder to avoid stashing such packets */
+	}
+	if (ret != KNOT_EOK) {
+		assert(!ret);
+		return kr_error(ret);
+	}
+	knot_wire_set_id(pkt->wire, msgid);
+
+	/* Add rank into the additional field. */
+	for (size_t i = 0; i < pkt->rrset_count; ++i) {
+		assert(!pkt->rr[i].additional);
+		uint8_t *rr_rank = mm_alloc(&pkt->mm, sizeof(*rr_rank));
+		if (!rr_rank) {
+			return kr_error(ENOMEM);
+		}
+		*rr_rank = eh->rank;
+		pkt->rr[i].additional = rr_rank;
+	}
+
+	/* Adjust TTL in each record. */
+	const uint32_t drift = eh->ttl - new_ttl;
+	for (knot_section_t i = KNOT_ANSWER; i <= KNOT_ADDITIONAL; ++i) {
+		const knot_pktsection_t *sec = knot_pkt_section(pkt, i);
+		for (unsigned k = 0; k < sec->count; ++k) {
+			knot_rrset_t *rrs = // vv FIXME??
+				/*const-cast*/(knot_rrset_t *)knot_pkt_rr(sec, k);
+			/* We need to be careful: due to enforcing minimum TTL
+			 * on packet, some records may be below that value.
+			 * We keep those records at TTL 0. */
+			if (rrs->ttl >= drift) {
+				rrs->ttl -= drift;
+			} else {
+				rrs->ttl = 0;
+			}
+		}
+	}
+
+	/* Finishing touches. TODO: perhaps factor out */
+	struct kr_qflags * const qf = &qry->flags;
+	qf->EXPIRING = is_expiring(eh->ttl, new_ttl);
+	qf->CACHED = true;
+	qf->NO_MINIMIZE = true;
+	qf->DNSSEC_INSECURE = kr_rank_test(eh->rank, KR_RANK_INSECURE);
+	qf->DNSSEC_BOGUS = kr_rank_test(eh->rank, KR_RANK_BOGUS);
+	if (qf->DNSSEC_INSECURE || qf->DNSSEC_BOGUS) {
+		qf->DNSSEC_WANT = false;
+	}
+	qf->DNSSEC_OPTOUT = eh->has_optout;
+	VERBOSE_MSG(qry, "=> satisfied by exact packet: rank 0%.2o, new TTL %d\n",
+			eh->rank, new_ttl);
+	return kr_ok();
+}
+