updates (also dnssec): cancel-out mode of changeset merge

src/knot/journal/journal.c

@@ -1180,7 +1180,7 @@ static int merge_itercb(iteration_ctx_t *ctx)
 
 	int ret = vals_to_changeset(ctx->val, ctx->chunk_count, ctx->txn->j->zone, &ch);
 	if (ret == KNOT_EOK) {
-		ret = changeset_merge(mch, ch);
+		ret = changeset_merge(mch, ch, 0);
 		changeset_free(ch);
 	}
 	return ret;

src/knot/updates/changesets.c

@@ -143,8 +143,14 @@ static knot_rrset_t get_next_rr(changeset_iter_t *ch_it, trie_it_t *t_it)
 	return node_rrset_at(ch_it->node, ch_it->node_pos++);
 }
 
-static void check_redundancy(zone_contents_t *counterpart, const knot_rrset_t *rr)
+// removes from counterpart what is in rr.
+// fixed_rr is an output parameter, holding a copy of rr without what has been removed from counterpart
+static void check_redundancy(zone_contents_t *counterpart, const knot_rrset_t *rr, knot_rrset_t **fixed_rr)
 {
+	if (fixed_rr != NULL) {
+		*fixed_rr = knot_rrset_copy(rr, NULL);
+	}
+
 	zone_node_t *node = zone_contents_find_node_for_rr(counterpart, rr);
 	if (node == NULL) {
 		return;
@@ -156,6 +162,14 @@ static void check_redundancy(zone_contents_t *counterpart, const knot_rrset_t *r
 
 	// Subtract the data from node's RRSet.
 	knot_rdataset_t *rrs = node_rdataset(node, rr->type);
+
+	if (fixed_rr != NULL && *fixed_rr != NULL) {
+		int ret = knot_rdataset_subtract(&(*fixed_rr)->rrs, rrs, true, NULL);
+		if (ret != KNOT_EOK) {
+			return;
+		}
+	}
+
 	int ret = knot_rdataset_subtract(rrs, &rr->rrs, true, NULL);
 	if (ret != KNOT_EOK) {
 		return;
@@ -266,6 +280,8 @@ int changeset_add_addition(changeset_t *ch, const knot_rrset_t *rrset, changeset
 		return handle_soa(&ch->soa_to, rrset);
 	}
 
+	knot_rrset_t *rrset_cancelout = NULL;
+
 	/* Check if there's any removal and remove that, then add this
 	 * addition anyway. Required to change TTLs. */
 	if (flags & CHANGESET_CHECK) {
@@ -275,14 +291,17 @@ int changeset_add_addition(changeset_t *ch, const knot_rrset_t *rrset, changeset
 			return KNOT_ENOMEM;
 		}
 
-		check_redundancy(ch->remove, rrset);
+		check_redundancy(ch->remove, rrset,
+				 ((flags & CHANGESET_CHECK_CANCELOUT) ? &rrset_cancelout : NULL));
 	}
 
-	int ret = add_rr_to_contents(ch->add, rrset);
+	const knot_rrset_t *to_add = (rrset_cancelout == NULL ? rrset : rrset_cancelout);
+	int ret = knot_rrset_empty(to_add) ? KNOT_EOK : add_rr_to_contents(ch->add, to_add);
 
 	if (flags & CHANGESET_CHECK) {
 		knot_rrset_free((knot_rrset_t **)&rrset, NULL);
 	}
+	knot_rrset_free(&rrset_cancelout, NULL);
 
 	return ret;
 }
@@ -298,6 +317,8 @@ int changeset_add_removal(changeset_t *ch, const knot_rrset_t *rrset, changeset_
 		return handle_soa(&ch->soa_from, rrset);
 	}
 
+	knot_rrset_t *rrset_cancelout = NULL;
+
 	/* Check if there's any addition and remove that, then add this
 	 * removal anyway. */
 	if (flags & CHANGESET_CHECK) {
@@ -307,15 +328,19 @@ int changeset_add_removal(changeset_t *ch, const knot_rrset_t *rrset, changeset_
 			return KNOT_ENOMEM;
 		}
 
-		check_redundancy(ch->add, rrset);
+		check_redundancy(ch->add, rrset,
+				 ((flags & CHANGESET_CHECK_CANCELOUT) ? &rrset_cancelout : NULL));
 	}
 
-	int ret = add_rr_to_contents(ch->remove, rrset);
+	const knot_rrset_t *to_remove = (rrset_cancelout == NULL ? rrset : rrset_cancelout);
+	int ret = knot_rrset_empty(to_remove) ? KNOT_EOK : add_rr_to_contents(ch->remove, to_remove);
 
 	if (flags & CHANGESET_CHECK) {
 		knot_rrset_free((knot_rrset_t **)&rrset, NULL);
 	}
 
+	knot_rrset_free(&rrset_cancelout, NULL);
+
 	// we don't care of TTLs at removals anyway (updates/apply.c/can_remove()/compare_ttls)
 	// in practice, this happens at merging changesets
 	return (ret == KNOT_ETTL ? KNOT_EOK : ret);
@@ -351,14 +376,14 @@ int changeset_remove_removal(changeset_t *ch, const knot_rrset_t *rrset)
 	return zone_contents_remove_rr(ch->remove, rrset, &n);
 }
 
-int changeset_merge(changeset_t *ch1, const changeset_t *ch2)
+int changeset_merge(changeset_t *ch1, const changeset_t *ch2, int flags)
 {
 	changeset_iter_t itt;
 	changeset_iter_rem(&itt, ch2);
 
 	knot_rrset_t rrset = changeset_iter_next(&itt);
 	while (!knot_rrset_empty(&rrset)) {
-		int ret = changeset_add_removal(ch1, &rrset, CHANGESET_CHECK);
+		int ret = changeset_add_removal(ch1, &rrset, CHANGESET_CHECK | flags);
 		if (ret != KNOT_EOK) {
 			changeset_iter_clear(&itt);
 			return ret;
@@ -371,7 +396,7 @@ int changeset_merge(changeset_t *ch1, const changeset_t *ch2)
 
 	rrset = changeset_iter_next(&itt);
 	while (!knot_rrset_empty(&rrset)) {
-		int ret = changeset_add_addition(ch1, &rrset, CHANGESET_CHECK);
+		int ret = changeset_add_addition(ch1, &rrset, CHANGESET_CHECK | flags);
 		if (ret != KNOT_EOK) {
 			changeset_iter_clear(&itt);
 			return ret;

src/knot/updates/changesets.h

@@ -24,6 +24,7 @@
 typedef enum {
 	CHANGESET_NONE = 0,
 	CHANGESET_CHECK = 1 << 0, /*! Perform redundancy check on additions/removals */
+	CHANGESET_CHECK_CANCELOUT = 1 << 1, /*! Do the complete cancelout on addition/removal/merge (depends on CHANGESET_CHECK */
 } changeset_flag_t;
 
 /*! \brief One zone change, from 'soa_from' to 'soa_to'. */
@@ -130,10 +131,11 @@ int changeset_remove_removal(changeset_t *ch, const knot_rrset_t *rrset);
  *
  * \param ch1  Merge into this changeset.
  * \param ch2  Merge this changeset.
+ * \param flags  Flags how to handle rendundancies.
  *
  * \return KNOT_E*
  */
-int changeset_merge(changeset_t *ch1, const changeset_t *ch2);
+int changeset_merge(changeset_t *ch1, const changeset_t *ch2, int flags);
 
 /*!
  * \brief Remove from changeset those rdata which won't be added/removed from zone.

src/knot/updates/zone-update.c

@@ -448,7 +448,7 @@ int zone_update_apply_changeset(zone_update_t *update, const changeset_t *change
 {
 	int ret = KNOT_EOK;
 	if (update->flags & UPDATE_INCREMENTAL) {
-		ret = changeset_merge(&update->change, changes);
+		ret = changeset_merge(&update->change, changes, CHANGESET_CHECK_CANCELOUT);
 	}
 	if (ret == KNOT_EOK) {
 		ret = apply_changeset_directly(&update->a_ctx, changes);

tests/test_changeset.c

@@ -143,7 +143,7 @@ int main(int argc, char *argv[])
 	assert(ret == KNOT_EOK);
 
 	// Test merge.
-	ret = changeset_merge(ch, ch2);
+	ret = changeset_merge(ch, ch2, 0);
 	ok(ret == KNOT_EOK && changeset_size(ch) == 5, "changeset: merge");
 
 	// Test preapply fix.