From: Daniel Salzman <daniel.salzman@nic.cz>
Date: Fri, 5 Oct 2018 11:47:25 +0000 (+0200)
Subject: knotd: add configurable answer rrset rotation determined by a query ID
X-Git-Tag: v2.8.0~227
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=de7d217d317265cf0fcfdce0431d41c127e689bc;p=thirdparty%2Fknot-dns.git

knotd: add configurable answer rrset rotation determined by a query ID

close #612
---

diff --git a/doc/man/knot.conf.5in b/doc/man/knot.conf.5in
index 4ee4080921..048f79719f 100644
--- a/doc/man/knot.conf.5in
+++ b/doc/man/knot.conf.5in
@@ -191,6 +191,7 @@ server:
     max\-ipv4\-udp\-payload: SIZE
     max\-ipv6\-udp\-payload: SIZE
     edns\-client\-subnet: BOOL
+    answer\-rotation: BOOL
     listen: ADDR[@INT] ...
 .ft P
 .fi
@@ -298,10 +299,17 @@ Maximum EDNS0 UDP payload size for IPv6.
 \fIDefault:\fP 4096
 .SS edns\-client\-subnet
 .sp
-Enable or disable EDNS Client Subnet support. If enabled, responses to queries containing the EDNS Client Subnet option
+Enable or disable EDNS Client Subnet support. If enabled, responses to queries
+containing the EDNS Client Subnet option
 always contain a valid EDNS Client Subnet option according to \fI\%RFC 7871\fP\&.
 .sp
 \fIDefault:\fP off
+.SS answer\-rotation
+.sp
+Enable or disable sorted\-rrset rotation in the answer section of normal replies.
+The rotation shift is simply determined by a query ID.
+.sp
+\fIDefault:\fP off
 .SS listen
 .sp
 One or more IP addresses where the server listens for incoming queries.
diff --git a/doc/reference.rst b/doc/reference.rst
index 37f194edbf..76277f37d5 100644
--- a/doc/reference.rst
+++ b/doc/reference.rst
@@ -142,6 +142,7 @@ General options related to the server.
      max-ipv4-udp-payload: SIZE
      max-ipv6-udp-payload: SIZE
      edns-client-subnet: BOOL
+     answer-rotation: BOOL
      listen: ADDR[@INT] ...
 
 .. _server_identity:
@@ -317,11 +318,22 @@ Maximum EDNS0 UDP payload size for IPv6.
 edns-client-subnet
 ------------------
 
-Enable or disable EDNS Client Subnet support. If enabled, responses to queries containing the EDNS Client Subnet option
+Enable or disable EDNS Client Subnet support. If enabled, responses to queries
+containing the EDNS Client Subnet option
 always contain a valid EDNS Client Subnet option according to :rfc:`7871`.
 
 *Default:* off
 
+.. _server_answer-rotation:
+
+answer-rotation
+---------------
+
+Enable or disable sorted-rrset rotation in the answer section of normal replies.
+The rotation shift is simply determined by a query ID.
+
+*Default:* off
+
 .. _server_listen:
 
 listen
diff --git a/src/knot/conf/base.c b/src/knot/conf/base.c
index 29e83205d0..4fee4afa82 100644
--- a/src/knot/conf/base.c
+++ b/src/knot/conf/base.c
@@ -140,6 +140,9 @@ static void init_cache(
 
 	val = conf_get(conf, C_SRV, C_ECS);
 	conf->cache.use_ecs = conf_bool(&val);
+
+	val = conf_get(conf, C_SRV, C_ANS_ROTATION);
+	conf->cache.srv_ans_rotate = conf_bool(&val);
 }
 
 int conf_new(
diff --git a/src/knot/conf/base.h b/src/knot/conf/base.h
index aae7d76598..09a332f944 100644
--- a/src/knot/conf/base.h
+++ b/src/knot/conf/base.h
@@ -115,6 +115,7 @@ typedef struct {
 		int32_t ctl_timeout;
 		conf_val_t srv_nsid;
 		bool use_ecs;
+		bool srv_ans_rotate;
 	} cache;
 
 	/*! List of dynamically loaded modules. */
diff --git a/src/knot/conf/schema.c b/src/knot/conf/schema.c
index 95cfa1fe80..d903d75043 100644
--- a/src/knot/conf/schema.c
+++ b/src/knot/conf/schema.c
@@ -158,6 +158,7 @@ static const yp_item_t desc_server[] = {
 	{ C_LISTEN,               YP_TADDR, YP_VADDR = { 53 }, YP_FMULTI },
 	{ C_COMMENT,              YP_TSTR,  YP_VNONE },
 	{ C_ECS,                  YP_TBOOL, YP_VNONE },
+	{ C_ANS_ROTATION,         YP_TBOOL, YP_VNONE },
 	{ NULL }
 };
 
diff --git a/src/knot/conf/schema.h b/src/knot/conf/schema.h
index 63066c7857..5725ad8146 100644
--- a/src/knot/conf/schema.h
+++ b/src/knot/conf/schema.h
@@ -23,6 +23,7 @@
 #define C_ACTION		"\x06""action"
 #define C_ADDR			"\x07""address"
 #define C_ALG			"\x09""algorithm"
+#define C_ANS_ROTATION		"\x0F""answer-rotation"
 #define C_ANY			"\x03""any"
 #define C_APPEND		"\x06""append"
 #define C_ASYNC_START		"\x0B""async-start"
diff --git a/src/knot/nameserver/process_query.c b/src/knot/nameserver/process_query.c
index 4d3641c667..4114c6aca4 100644
--- a/src/knot/nameserver/process_query.c
+++ b/src/knot/nameserver/process_query.c
@@ -858,8 +858,9 @@ int process_query_put_rr(knot_pkt_t *pkt, knotd_qdata_t *qdata,
 		to_add = *rr;
 	}
 
+	uint16_t rotate = conf()->cache.srv_ans_rotate ? knot_wire_get_id(qdata->query->wire) : 0;
 	uint16_t prev_count = pkt->rrset_count;
-	ret = knot_pkt_put(pkt, compr_hint, &to_add, flags);
+	ret = knot_pkt_put_rotate(pkt, compr_hint, &to_add, rotate, flags);
 	if (ret != KNOT_EOK && (flags & KNOT_PF_FREE)) {
 		knot_rrset_clear(&to_add, &pkt->mm);
 		return ret;
diff --git a/tests/knot/test_confio.c b/tests/knot/test_confio.c
index ef67bbdf90..00af7956e2 100644
--- a/tests/knot/test_confio.c
+++ b/tests/knot/test_confio.c
@@ -909,7 +909,8 @@ static void test_conf_io_list(void)
 	      "server.max-udp-payload\n"
 	      "server.max-ipv4-udp-payload\n"
 	      "server.max-ipv6-udp-payload\n"
-	      "server.edns-client-subnet";
+	      "server.edns-client-subnet\n"
+	      "server.answer-rotation";
 	ok(strcmp(ref, out) == 0, "compare result");
 }
 
@@ -926,6 +927,7 @@ static const yp_item_t desc_server[] = {
 	{ C_MAX_IPV4_UDP_PAYLOAD, YP_TINT,  YP_VNONE },
 	{ C_MAX_IPV6_UDP_PAYLOAD, YP_TINT,  YP_VNONE },
 	{ C_ECS,                  YP_TBOOL, YP_VNONE },
+	{ C_ANS_ROTATION,         YP_TBOOL, YP_VNONE },
 	{ NULL }
 };