lib: requery when nameserver returns (falsely) NXDOMAIN

diff --git a/lib/layer/iterate.c b/lib/layer/iterate.c
index e30089f0f603f0fbaf6022af2b7345170c898e17..19c5434d6289f277f394a3cd9b217bc9d640893e 100644 (file)
--- a/lib/layer/iterate.c
+++ b/lib/layer/iterate.c
@@ -209,11 +209,13 @@ static int process_answer(knot_pkt_t *pkt, struct kr_layer_param *param)
        /* Response for minimized QNAME.
         * NODATA   => may be empty non-terminal, retry (found zone cut)
         * NOERROR  => found zone cut, retry
-        * NXDOMAIN => parent is zone cut, terminate
+        * NXDOMAIN => parent is zone cut, retry as a workaround for bad authoritatives
         */
+       const knot_pktsection_t *an = knot_pkt_section(pkt, KNOT_ANSWER);
        bool is_minimized = (!knot_dname_is_equal(knot_pkt_qname(pkt), query->sname));
-       bool is_noerror = (knot_wire_get_rcode(pkt->wire) == KNOT_RCODE_NOERROR);
-       if (is_minimized && is_noerror) {
+       bool is_nodata = (knot_wire_get_rcode(pkt->wire) == KNOT_RCODE_NOERROR) && !an->count;
+       bool is_nxdomain = (knot_wire_get_rcode(pkt->wire) == KNOT_RCODE_NXDOMAIN);
+       if (is_minimized && (is_nodata || is_nxdomain)) {
                query->flags |= QUERY_NO_MINIMIZE;
                return KNOT_NS_PROC_DONE;
        }
@@ -227,7 +229,6 @@ static int process_answer(knot_pkt_t *pkt, struct kr_layer_param *param)
 
        /* Process answer section records. */
        const knot_dname_t *cname = query->sname;
-       const knot_pktsection_t *an = knot_pkt_section(pkt, KNOT_ANSWER);
        for (unsigned i = 0; i < an->count; ++i) {
                const knot_rrset_t *rr = knot_pkt_rr(an, i);
                int state = callback(rr, 0, param);

diff --git a/tests/testdata/iter_minim_a_nxdomain.rpl b/tests/testdata/iter_minim_a_nxdomain.rpl
new file mode 100644 (file)
index 0000000..cca9fa1
--- /dev/null
+++ b/tests/testdata/iter_minim_a_nxdomain.rpl
@@ -0,0 +1,107 @@
+; config options
+server:
+       target-fetch-policy: "0 0 0 0 0"
+       query-minimization: on
+
+stub-zone:
+       name: "."
+       stub-addr: 193.0.14.129         # K.ROOT-SERVERS.NET.
+CONFIG_END
+
+SCENARIO_BEGIN Test basic query minimization sub.www.example.com. when NS doesn't show empty non-terminal.
+
+; K.ROOT-SERVERS.NET.
+RANGE_BEGIN 0 100
+       ADDRESS 193.0.14.129 
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+. IN NS
+SECTION ANSWER
+. IN NS        K.ROOT-SERVERS.NET.
+SECTION ADDITIONAL
+K.ROOT-SERVERS.NET.    IN      A       193.0.14.129
+ENTRY_END
+
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+com. IN NS
+SECTION AUTHORITY
+com.   IN NS   a.gtld-servers.net.
+SECTION ADDITIONAL
+a.gtld-servers.net.    IN      A       192.5.6.30
+ENTRY_END
+RANGE_END
+
+; a.gtld-servers.net.
+RANGE_BEGIN 0 100
+       ADDRESS 192.5.6.30
+
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+example.com. IN NS
+SECTION AUTHORITY
+example.com.   IN NS   ns.example.com.
+SECTION ADDITIONAL
+ns.example.com.                IN      A       1.2.3.4
+ENTRY_END
+RANGE_END
+
+; ns.example.com.
+RANGE_BEGIN 0 100
+       ADDRESS 1.2.3.4
+
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NXDOMAIN 
+SECTION QUESTION
+www.example.com. IN NS
+SECTION ANSWER
+SECTION AUTHORITY
+example.com.   IN NS   ns.example.com.
+ENTRY_END
+
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+sub.www.example.com. IN A
+SECTION ANSWER
+sub.www.example.com. IN A      10.20.30.40
+SECTION AUTHORITY
+example.com.   IN NS   ns.example.com.
+SECTION ADDITIONAL
+ns.example.com.                IN      A       1.2.3.4
+ENTRY_END
+
+RANGE_END
+
+STEP 1 QUERY
+ENTRY_BEGIN
+REPLY RD
+SECTION QUESTION
+sub.www.example.com. IN A
+ENTRY_END
+
+; recursion happens here.
+STEP 10 CHECK_ANSWER
+ENTRY_BEGIN
+MATCH all
+REPLY QR RD RA NOERROR
+SECTION QUESTION
+sub.www.example.com. IN A
+SECTION ANSWER
+sub.www.example.com. IN A      10.20.30.40
+ENTRY_END
+
+SCENARIO_END