pinctrl: dns: Ignore additional records.

EDNS is backwards compatible so it's safe to just ignore additional ARs.

Reported-at: ovn-org#228
Reported-at: https://issues.redhat.com/browse/FDP-222
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
Acked-by: Mark Michelson <mmichels@redhat.com>
(cherry picked from commit b7fe2c8)

Author: dceara

controller/pinctrl.c

@@ -2949,6 +2949,8 @@ dns_build_ptr_answer(
     free(encoded_answer);
 }
 
+#define DNS_QUERY_TYPE_CLASS_LEN (2 * sizeof(ovs_be16))
+
 /* Called with in the pinctrl_handler thread context. */
 static void
 pinctrl_handle_dns_lookup(
@@ -3010,18 +3012,13 @@ pinctrl_handle_dns_lookup(
         goto exit;
     }
 
-    /* Check if there is an additional record present, which is unsupported */
-    if (in_dns_header->arcount) {
-        VLOG_DBG_RL(&rl, "Received DNS query with additional records, which"
-                    " is unsupported");
-        goto exit;
-    }
-
     struct udp_header *in_udp = dp_packet_l4(pkt_in);
     size_t udp_len = ntohs(in_udp->udp_len);
     size_t l4_len = dp_packet_l4_size(pkt_in);
+    uint8_t *l4_start = (uint8_t *) in_udp;
     uint8_t *end = (uint8_t *)in_udp + MIN(udp_len, l4_len);
     uint8_t *in_dns_data = (uint8_t *)(in_dns_header + 1);
+    uint8_t *in_dns_data_start = in_dns_data;
     uint8_t *in_queryname = in_dns_data;
     uint16_t idx = 0;
     struct ds query_name;
@@ -3045,7 +3042,7 @@ pinctrl_handle_dns_lookup(
     in_dns_data += idx;
 
     /* Query should have TYPE and CLASS fields */
-    if (in_dns_data + (2 * sizeof(ovs_be16)) > end) {
+    if (in_dns_data + DNS_QUERY_TYPE_CLASS_LEN > end) {
         ds_destroy(&query_name);
         goto exit;
     }
@@ -3059,6 +3056,10 @@ pinctrl_handle_dns_lookup(
         goto exit;
     }
 
+    uint8_t *rest = in_dns_data + DNS_QUERY_TYPE_CLASS_LEN;
+    uint32_t query_size = rest - in_dns_data_start;
+    uint32_t query_l4_size = rest - l4_start;
+
     uint64_t dp_key = ntohll(pin->flow_metadata.flow.metadata);
     const char *answer_data = NULL;
     struct shash_node *iter;
@@ -3127,7 +3128,7 @@ pinctrl_handle_dns_lookup(
         goto exit;
     }
 
-    uint16_t new_l4_size = ntohs(in_udp->udp_len) +  dns_answer.size;
+    uint16_t new_l4_size = query_l4_size + dns_answer.size;
     size_t new_packet_size = pkt_in->l4_ofs + new_l4_size;
     struct dp_packet pkt_out;
     dp_packet_init(&pkt_out, new_packet_size);
@@ -3160,7 +3161,7 @@ pinctrl_handle_dns_lookup(
     out_dns_header->arcount = 0;
 
     /* Copy the Query section. */
-    dp_packet_put(&pkt_out, dp_packet_data(pkt_in), dp_packet_size(pkt_in));
+    dp_packet_put(&pkt_out, dp_packet_data(pkt_in), query_size);
 
     /* Copy the answer sections. */
     dp_packet_put(&pkt_out, dns_answer.data, dns_answer.size);

tests/ovn.at

@@ -11115,6 +11115,57 @@ OVN_CLEANUP([hv1])
 AT_CLEANUP
 ])
 
+OVN_FOR_EACH_NORTHD([
+AT_SETUP([dns lookup : EDNS])
+AT_SKIP_IF([test $HAVE_SCAPY = no])
+ovn_start
+
+check ovn-nbctl ls-add ls \
+    -- lsp-add ls lsp     \
+    -- lsp-set-addresses lsp "00:00:00:00:00:01 10.0.0.1"
+
+d=$(ovn-nbctl create dns records={})
+
+check ovn-nbctl set dns $d records:foo.ovn.org="10.0.0.42"
+check ovn-nbctl set Logical_switch ls dns_records="$d"
+
+net_add n1
+sim_add hv1
+
+as hv1
+ovs-vsctl add-br br-phys
+ovn_attach n1 br-phys 192.168.0.1
+check ovs-vsctl add-port br-int hv1-vif1 -- \
+    set interface hv1-vif1 external-ids:iface-id=lsp \
+    options:tx_pcap=hv1/vif1-tx.pcap \
+    options:rxq_pcap=hv1/vif1-rx.pcap
+
+OVN_POPULATE_ARP
+wait_for_ports_up
+check ovn-nbctl --wait=hv sync
+
+dns_req=$(fmt_pkt "Ether(dst='00:00:00:00:00:02', src='00:00:00:00:00:01') / \
+                   IP(dst='10.0.0.254', src='10.0.0.1') / \
+                   UDP(sport=42424, dport=53) / \
+                   DNS(rd=1, qd=DNSQR(qname='foo.ovn.org'), arcount=1, ar=[ \
+                       DNSRR(type='OPT', rclass=4096, \
+                             rdata=EDNS0ClientSubnet(source_plen=24, \
+                                                     address='10.0.0.1'))])")
+dns_reply=$(fmt_pkt "Ether(dst='00:00:00:00:00:01', src='00:00:00:00:00:02') / \
+                     IP(dst='10.0.0.1', src='10.0.0.254') / \
+                     UDP(sport=53, dport=42424,chksum=0) / \
+                     DNS(qr=1, qd=DNSQR(qname='foo.ovn.org'), \
+                         an=DNSRR(rrname='foo.ovn.org', type='A', ttl=3600, \
+                                  rdata='10.0.0.42'))")
+echo ${dns_reply} > expected
+
+as hv1 ovs-appctl netdev-dummy/receive hv1-vif1 ${dns_req}
+OVN_CHECK_PACKETS_REMOVE_BROADCAST([hv1/vif1-tx.pcap], [expected])
+
+OVN_CLEANUP([hv1])
+AT_CLEANUP
+])
+
 OVN_FOR_EACH_NORTHD([
 AT_SETUP([4 HV, 1 LS, 1 LR, packet test with HA distributed router gateway port])
 ovn_start