add option to reorder cached RRs in answers

Fixes https://gitlab.labs.nic.cz/knot/resolver/issues/93.
API of a KR_EXPORT function is changed, so ABIVER is bumped.

NEWS

@@ -1,3 +1,8 @@
+Knot Resolver 1.x.y (2016-xx-yy)
+================================
+
+- It now requires knot >= 2.3.1 to link successfully.
+
 Knot Resolver 1.1.1 (2016-08-24)
 ================================
 

config.mk

@@ -2,7 +2,7 @@
 MAJOR := 1
 MINOR := 1
 PATCH := 1
-ABIVER := 1
+ABIVER := 2
 BUILDMODE := dynamic
 HARDENING := yes
 

daemon/README.rst

@@ -394,6 +394,14 @@ Environment
     "Use in-bailiwick glue", "normal, permissive"
     "Use any glue records", "permissive"
 
+.. function:: reorder_RR([true | false])
+
+   :param boolean value: New value for the option *(optional)*
+   :return: The (new) value of the option
+
+   If set, resolver will vary the order of resource records within RR-sets
+   every time when answered from cache.  It is disabled by default.
+
 .. function:: user(name, [group])
 
    :param string name: user name

daemon/engine.c

@@ -66,6 +66,7 @@ static int l_help(lua_State *L)
 		"verbose(true|false)\n    toggle verbose mode\n"
 		"option(opt[, new_val])\n    get/set server option\n"
 		"mode(strict|normal|permissive)\n    set resolver strictness level\n"
+		"reorder_RR([true|false])\n    set/get reordering of RRs within RRsets\n"
 		"resolve(name, type[, class, flags, callback])\n    resolve query, callback when it's finished\n"
 		"todname(name)\n    convert name to wire format\n"
 		"tojson(val)\n    convert value to JSON\n"

daemon/lua/sandbox.lua

@@ -49,6 +49,11 @@ function mode(m)
 	return true
 end
 
+-- Trivial option alias
+function reorder_RR(val)
+	return option('REORDER_RR', val)
+end
+
 -- Function aliases
 -- `env.VAR returns os.getenv(VAR)`
 env = {}

lib/cache.c

@@ -326,7 +326,8 @@ int kr_cache_peek_rank(struct kr_cache *cache, uint8_t tag, const knot_dname_t *
 	return found->rank;
 }
 
-int kr_cache_materialize(knot_rrset_t *dst, const knot_rrset_t *src, uint32_t drift, knot_mm_t *mm)
+int kr_cache_materialize(knot_rrset_t *dst, const knot_rrset_t *src, uint32_t drift,
+		uint reorder, knot_mm_t *mm)
 {
 	if (!dst || !src || dst == src) {
 		return kr_error(EINVAL);
@@ -339,17 +340,36 @@ int kr_cache_materialize(knot_rrset_t *dst, const knot_rrset_t *src, uint32_t dr
 		return kr_error(ENOMEM);
 	}
 
-	/* Copy valid records */
+	/* Find valid records */
+	knot_rdata_t **valid = malloc(sizeof(knot_rdata_t *) * src->rrs.rr_count);
+	uint16_t valid_count = 0;
 	knot_rdata_t *rd = src->rrs.data;
 	for (uint16_t i = 0; i < src->rrs.rr_count; ++i) {
 		if (knot_rdata_ttl(rd) >= drift) {
-			if (knot_rdataset_add(&dst->rrs, rd, mm) != 0) {
-				knot_rrset_clear(dst, mm);
-				return kr_error(ENOMEM);
-			}
+			valid[valid_count++] = rd;
 		}
 		rd = kr_rdataset_next(rd);
 	}
+
+	if (reorder && valid_count > 1) {
+		/* Reorder the valid part; it's a reversed rotation,
+		 * done by two array reversals. */
+		uint16_t shift = reorder % valid_count;
+		for (uint16_t i = 0; i < shift / 2; ++i) {
+			SWAP(valid[i], valid[shift - 1 - i]);
+		}
+		for (uint16_t i = 0; i < (valid_count - shift) / 2; ++i) {
+			SWAP(valid[shift + i], valid[valid_count - 1 - i]);
+		}
+	}
+
+	int err = knot_rdataset_gather(&dst->rrs, valid, valid_count, mm);
+	free(valid);
+	if (err) {
+		knot_rrset_clear(dst, mm);
+		return kr_error(err);
+	}
+
 	/* Fixup TTL by time passed */
 	rd = dst->rrs.data;
 	for (uint16_t i = 0; i < dst->rrs.rr_count; ++i) {

lib/cache.h

@@ -207,11 +207,13 @@ int kr_cache_peek_rr(struct kr_cache *cache, knot_rrset_t *rr, uint8_t *rank, ui
  * @param dst destination for materialized RRSet
  * @param src read-only RRSet (its rdataset may be changed depending on the result)
  * @param drift time passed between cache time and now
+ * @param reorder (pseudo)-random seed to reorder the data or zero
  * @param mm memory context
  * @return 0 or an errcode
  */
 KR_EXPORT
-int kr_cache_materialize(knot_rrset_t *dst, const knot_rrset_t *src, uint32_t drift, knot_mm_t *mm);
+int kr_cache_materialize(knot_rrset_t *dst, const knot_rrset_t *src, uint32_t drift,
+		uint reorder, knot_mm_t *mm);
 
 /**
  * Insert RRSet into cache, replacing any existing data.

lib/layer/rrcache.c

@@ -78,7 +78,7 @@ static int loot_rr(struct kr_cache *cache, knot_pkt_t *pkt, const knot_dname_t *
 
 	/* Update packet answer */
 	knot_rrset_t rr_copy;
-	ret = kr_cache_materialize(&rr_copy, &cache_rr, drift, &pkt->mm);
+	ret = kr_cache_materialize(&rr_copy, &cache_rr, drift, qry->reorder, &pkt->mm);
 	if (ret == 0) {
 		ret = knot_pkt_put(pkt, KNOT_COMPR_HINT_QNAME, &rr_copy, KNOT_PF_FREE);
 		if (ret != 0) {

lib/rplan.c

@@ -132,6 +132,9 @@ static struct kr_query *kr_rplan_push_query(struct kr_rplan *rplan,
 	qry->ns.addr[0].ip.sa_family = AF_UNSPEC;
 	gettimeofday(&qry->timestamp, NULL);
 	kr_zonecut_init(&qry->zone_cut, (const uint8_t *)"", rplan->pool);
+	qry->reorder = qry->flags & QUERY_REORDER_RR
+		? knot_wire_get_id(rplan->request->answer->wire)
+		: 0;
 	array_push(rplan->pending, qry);
 
 	return qry;

lib/rplan.h

@@ -48,7 +48,8 @@
 	X(PERMISSIVE,      1 << 20) /**< Permissive resolver mode. */ \
 	X(STRICT,          1 << 21) /**< Strict resolver mode. */ \
 	X(BADCOOKIE_AGAIN, 1 << 22) /**< Query again because bad cookie returned. */ \
-	X(CNAME,	   1 << 23) /**< Query response contains CNAME in answer section. */
+	X(CNAME,	   1 << 23) /**< Query response contains CNAME in answer section. */ \
+	X(REORDER_RR,      1 << 24) /**< Reorder cached RRs. */
 
 /** Query flags */
 enum kr_query_flag {
@@ -73,6 +74,7 @@ struct kr_query {
 	uint32_t flags;
 	uint32_t secret;
 	uint16_t fails;
+	uint16_t reorder; /**< Seed to reorder (cached) RRs in answer or zero. */
 	struct timeval timestamp;
 	struct kr_zonecut zone_cut;
 	struct kr_nsrep ns;

lib/utils.h

@@ -166,3 +166,12 @@ int kr_rrarray_add(rr_array_t *array, const knot_rrset_t *rr, knot_mm_t *pool);
  */
 KR_EXPORT
 char *kr_module_call(struct kr_context *ctx, const char *module, const char *prop, const char *input);
+
+/** Swap two places.  Note: the parameters need to be without side effects. */
+#define SWAP(x, y) do { /* http://stackoverflow.com/a/3982430/587396 */ \
+	unsigned char swap_temp[sizeof(x) == sizeof(y) ? (ssize_t)sizeof(x) : -1]; \
+	memcpy(swap_temp, &y, sizeof(x)); \
+	memcpy(&y,        &x, sizeof(x)); \
+	memcpy(&x, swap_temp, sizeof(x)); \
+	} while(0)
+

lib/zonecut.c

@@ -330,7 +330,7 @@ static int fetch_ns(struct kr_context *ctx, struct kr_zonecut *cut, const knot_d
 
 	/* Materialize as we'll going to do more cache lookups. */
 	knot_rrset_t rr_copy;
-	ret = kr_cache_materialize(&rr_copy, &cached_rr, drift, cut->pool);
+	ret = kr_cache_materialize(&rr_copy, &cached_rr, drift, 0, cut->pool);
 	if (ret != 0) {
 		return ret;
 	}
@@ -380,7 +380,7 @@ static int fetch_rrset(knot_rrset_t **rr, struct kr_cache *cache,
 		return kr_error(ENOMEM);
 	}
 
-	ret = kr_cache_materialize(*rr, &cached_rr, drift, pool);
+	ret = kr_cache_materialize(*rr, &cached_rr, drift, 0, pool);
 	if (ret != 0) {
 		knot_rrset_free(rr, pool);
 		return ret;

tests/test_cache.c

@@ -39,17 +39,19 @@ knot_db_val_t global_namedb_data = {namedb_data, NAMEDB_DATA_SIZE};
 #define CACHE_TTL 10
 #define CACHE_TIME 0
 
-int (*original_knot_rdataset_add)(knot_rdataset_t *rrs, const knot_rdata_t *rr, knot_mm_t *mm) = NULL;
+int (*original_knot_rdataset_gather)(knot_rdataset_t *dst, knot_rdata_t **src,
+		uint16_t count, knot_mm_t *mm) = NULL;
 
-int knot_rdataset_add(knot_rdataset_t *rrs, const knot_rdata_t *rr, knot_mm_t *mm)
+int knot_rdataset_gather(knot_rdataset_t *dst, knot_rdata_t **src, uint16_t count,
+		knot_mm_t *mm)
 {
 	int err, err_mock;
 	err_mock = (int)mock();
-	if (original_knot_rdataset_add == NULL) {
-		original_knot_rdataset_add = dlsym(RTLD_NEXT,"knot_rdataset_add");
-		assert_non_null (original_knot_rdataset_add);
+	if (original_knot_rdataset_gather == NULL) {
+		original_knot_rdataset_gather = dlsym(RTLD_NEXT,"knot_rdataset_gather");
+		assert_non_null (original_knot_rdataset_gather);
 	}	
-	err = original_knot_rdataset_add(rrs, rr, mm);
+	err = original_knot_rdataset_gather(dst, src, count, mm);
 	if (err_mock != 0)
 	    err = err_mock;
 	return err;
@@ -235,7 +237,7 @@ static void test_materialize(void **state)
 
 	global_rr.owner = NULL;
 	knot_rrset_init(&output_rr, NULL, 0, 0);
-	kr_cache_materialize(&output_rr, &global_rr, 0, &global_mm);
+	kr_cache_materialize(&output_rr, &global_rr, 0, 0, &global_mm);
 	res_cmp_ok_empty = knot_rrset_equal(&global_rr, &output_rr, KNOT_RRSET_COMPARE_HEADER);
 	res_cmp_fail_empty = knot_rrset_equal(&global_rr, &output_rr, KNOT_RRSET_COMPARE_WHOLE);
 	knot_rrset_clear(&output_rr, &global_mm);
@@ -244,15 +246,15 @@ static void test_materialize(void **state)
 	assert_false(res_cmp_fail_empty);
 
 	knot_rrset_init(&output_rr, NULL, 0, 0);
-	will_return (knot_rdataset_add, 0);
-	kr_cache_materialize(&output_rr, &global_rr, 0, &global_mm);
+	will_return (knot_rdataset_gather, 0);
+	kr_cache_materialize(&output_rr, &global_rr, 0, 0, &global_mm);
 	res_cmp_ok = knot_rrset_equal(&global_rr, &output_rr, KNOT_RRSET_COMPARE_WHOLE);
 	knot_rrset_clear(&output_rr, &global_mm);
 	assert_true(res_cmp_ok);
 
 	knot_rrset_init(&output_rr, NULL, 0, 0);
-	will_return (knot_rdataset_add, KNOT_EINVAL);
-	kr_cache_materialize(&output_rr, &global_rr, 0, &global_mm);
+	will_return (knot_rdataset_gather, KNOT_ENOMEM);
+	kr_cache_materialize(&output_rr, &global_rr, 0, 0, &global_mm);
 	res_cmp_fail = knot_rrset_equal(&global_rr, &output_rr, KNOT_RRSET_COMPARE_WHOLE);
 	knot_rrset_clear(&output_rr, &global_mm);
 	assert_false(res_cmp_fail);