DNS: extract geolocation information, if available (#2065)

The option NSID (RFC5001) is used by Google DNS to report the airport code of the metro where the DNS query is handled. This option is quite rare, but the added overhead in DNS code is pretty much zero for "normal" DNS traffic
ntop · Jul 31, 2023 · 5019022 · 5019022
1 parent d477da9
commit 5019022
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Showing 7 changed files with 72 additions and 1 deletion.
diff --git a/example/ndpiReader.c b/example/ndpiReader.c
@@ -1779,6 +1779,8 @@ static void printFlow(u_int32_t id, struct ndpi_flow_info *flow, u_int16_t threa
 
     if(flow->flow_extra_info[0] != '\0') fprintf(out, "[%s]", flow->flow_extra_info);
 
+    if(flow->dns.geolocation_iata_code[0] != '\0') fprintf(out, "[GeoLocation: %s]", flow->dns.geolocation_iata_code);
+
     if((flow->src2dst_packets+flow->dst2src_packets) > 5) {
       if(flow->iat_c_to_s && flow->iat_s_to_c) {
 	float data_ratio = ndpi_data_ratio(flow->src2dst_bytes, flow->dst2src_bytes);

diff --git a/example/reader_util.c b/example/reader_util.c
@@ -1228,6 +1228,8 @@ void process_ndpi_collected_info(struct ndpi_workflow * workflow, struct ndpi_fl
       /* For consistency across platforms replace :0: with :: */
       ndpi_patchIPv6Address(flow->info);
     }
+    if(flow->ndpi_flow->protos.dns.geolocation_iata_code[0] != '\0')
+      strcpy(flow->dns.geolocation_iata_code, flow->ndpi_flow->protos.dns.geolocation_iata_code);
   }
   /* MDNS */
   else if(is_ndpi_proto(flow, NDPI_PROTOCOL_MDNS)) {

diff --git a/example/reader_util.h b/example/reader_util.h
@@ -294,6 +294,10 @@ typedef struct ndpi_flow_info {
     char *username, *password;
   } telnet;
 
+  struct {
+    char geolocation_iata_code[4];
+  } dns;
+
   ndpi_multimedia_flow_type multimedia_flow_type;
 
   void *src_id, *dst_id;

diff --git a/src/include/ndpi_typedefs.h b/src/include/ndpi_typedefs.h
@@ -1486,6 +1486,7 @@ struct ndpi_flow_struct {
       u_int8_t num_queries, num_answers, reply_code, is_query;
       u_int16_t query_type, query_class, rsp_type, edns0_udp_payload_size;
       ndpi_ip_addr_t rsp_addr; /* The first address in a DNS response packet (A and AAAA) */
+      char geolocation_iata_code[4];
       char ptr_domain_name[64 /* large enough but smaller than { } tls */];
     } dns;
 

diff --git a/src/lib/protocols/dns.c b/src/lib/protocols/dns.c
@@ -547,7 +547,8 @@ static int search_valid_dns(struct ndpi_detection_module_struct *ndpi_struct,
 	  u_int16_t num;
 
 	  for(num = 0; num < dns_header->additional_rrs; num++) {
-	    u_int16_t data_len;
+	    u_int16_t data_len, rdata_len, opt_code, opt_len;
+	    const unsigned char *opt;
 
 	    if((x+6) > packet->payload_packet_len) {
 	      break;
@@ -576,6 +577,34 @@ static int search_valid_dns(struct ndpi_detection_module_struct *ndpi_struct,
 	      printf("[DNS] [response] edns0_udp_payload_size: %u\n", flow->protos.dns.edns0_udp_payload_size);
 #endif
 	      x += 6;
+
+	      rdata_len = ntohs(*((u_int16_t *)&packet->payload[x]));
+#ifdef DNS_DEBUG
+	      printf("[DNS] [response] rdata len: %u\n", rdata_len);
+#endif
+	      if(rdata_len > 0 &&
+		 x + 6 <= packet->payload_packet_len) {
+		opt_code = ntohs(*((u_int16_t *)&packet->payload[x + 2]));
+		opt_len = ntohs(*((u_int16_t *)&packet->payload[x + 4]));
+		opt = &packet->payload[x + 6];
+		/* TODO: parse the TLV list */
+		if(opt_code == 0x03 &&
+		   opt_len <= rdata_len + 4 &&
+		   opt_len > 6 &&
+		   x + 6 + opt_len <= packet->payload_packet_len) {
+#ifdef DNS_DEBUG
+		  printf("[DNS] NSID: [%.*s]\n", opt_len, opt);
+#endif
+		  if(memcmp(opt, "gpdns-", 6) == 0) {
+#ifdef DNS_DEBUG
+		    printf("[DNS] NSID Airport code [%.*s]\n", opt_len - 6, opt + 6);
+#endif
+		    memcpy(flow->protos.dns.geolocation_iata_code, opt + 6,
+			   ndpi_min(opt_len - 6, (int)sizeof(flow->protos.dns.geolocation_iata_code) - 1));
+		  }
+		}
+
+	      }
 	    } else {
 	      x += 6;
 	    }

diff --git a/tests/cfgs/default/pcap/dns-google-nsid.pcapng b/tests/cfgs/default/pcap/dns-google-nsid.pcapng
diff --git a/tests/cfgs/default/result/dns-google-nsid.pcapng.out b/tests/cfgs/default/result/dns-google-nsid.pcapng.out
@@ -0,0 +1,33 @@
+Guessed flow protos:	0
+
+DPI Packets (UDP):	14	(2.00 pkts/flow)
+Confidence DPI              : 7 (flows)
+Num dissector calls: 7 (1.00 diss/flow)
+LRU cache ookla:      0/0/0 (insert/search/found)
+LRU cache bittorrent: 0/0/0 (insert/search/found)
+LRU cache zoom:       0/0/0 (insert/search/found)
+LRU cache stun:       0/0/0 (insert/search/found)
+LRU cache tls_cert:   0/0/0 (insert/search/found)
+LRU cache mining:     0/0/0 (insert/search/found)
+LRU cache msteams:    0/0/0 (insert/search/found)
+LRU cache stun_zoom:  0/0/0 (insert/search/found)
+Automa host:          12/8 (search/found)
+Automa domain:        12/0 (search/found)
+Automa tls cert:      0/0 (search/found)
+Automa risk mask:     6/0 (search/found)
+Automa common alpns:  0/0 (search/found)
+Patricia risk mask:   6/0 (search/found)
+Patricia risk:        0/0 (search/found)
+Patricia protocols:   3/3 (search/found)
+
+DNS	6	952	3
+ntop	4	514	2
+Wikipedia	4	704	2
+
+	1	UDP [2001:b07:a3d:c112:b332:20d:89ab:105e]:41624 <-> [2001:4860:4860::8844]:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][DPI packets: 2][cat: Network/14][1 pkts/106 bytes <-> 1 pkts/314 bytes][Goodput ratio: 41/80][0.01 sec][::][GeoLocation: mil][PLAIN TEXT (servers)][Plen Bins: 0,50,0,0,0,0,0,50,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+	2	UDP [2a03:b0c0:2:d0::360:4001]:44924 <-> [2001:4860:4860::8888]:53 [proto: 5.176/DNS.Wikipedia][IP: 0/Unknown][ClearText][Confidence: DPI][DPI packets: 2][cat: Network/14][1 pkts/123 bytes <-> 1 pkts/256 bytes][Goodput ratio: 49/75][0.20 sec][Hostname/SNI: www.wikipedia.it][18.67.39.58][GeoLocation: ams][PLAIN TEXT (wikipedia)][Plen Bins: 0,50,0,0,0,0,50,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+	3	UDP 192.168.1.29:62500 <-> 8.8.4.4:53 [proto: 5.176/DNS.Wikipedia][IP: 126/Google][ClearText][Confidence: DPI][DPI packets: 2][cat: Network/14][1 pkts/91 bytes <-> 1 pkts/234 bytes][Goodput ratio: 53/82][0.27 sec][Hostname/SNI: www.wikipedia.it][108.157.194.28][PLAIN TEXT (wikipedia)][Plen Bins: 0,50,0,0,0,0,50,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+	4	UDP [2a03:b0c0:2:d0::360:4001]:43660 <-> [2001:4860:4860::8888]:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][DPI packets: 2][cat: Network/14][1 pkts/124 bytes <-> 1 pkts/169 bytes][Goodput ratio: 50/63][0.01 sec][Hostname/SNI: www.wireshark.org][104.26.10.240][GeoLocation: ams][PLAIN TEXT (wireshark)][Plen Bins: 0,50,0,50,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+	5	UDP [2a03:b0c0:2:d0::360:4001]:46618 <-> [2001:4860:4860::8888]:53 [proto: 5.26/DNS.ntop][IP: 0/Unknown][ClearText][Confidence: DPI][DPI packets: 2][cat: Network/14][1 pkts/119 bytes <-> 1 pkts/164 bytes][Goodput ratio: 47/62][0.02 sec][Hostname/SNI: www.ntop.org][178.62.197.130][GeoLocation: ams][PLAIN TEXT (digitalocean)][Plen Bins: 0,50,0,50,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+	6	UDP 192.168.1.29:51166 <-> 8.8.4.4:53 [proto: 5/DNS][IP: 126/Google][ClearText][Confidence: DPI][DPI packets: 2][cat: Network/14][1 pkts/92 bytes <-> 1 pkts/147 bytes][Goodput ratio: 54/71][0.02 sec][Hostname/SNI: www.wireshark.org][104.26.10.240][PLAIN TEXT (wireshark)][Plen Bins: 0,50,0,50,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+	7	UDP 192.168.1.29:58580 <-> 8.8.4.4:53 [proto: 5.26/DNS.ntop][IP: 126/Google][ClearText][Confidence: DPI][DPI packets: 2][cat: Network/14][1 pkts/87 bytes <-> 1 pkts/144 bytes][Goodput ratio: 51/70][0.03 sec][Hostname/SNI: www.ntop.org][178.62.197.130][GeoLocation: mil][PLAIN TEXT (digitalocean)][Plen Bins: 0,50,0,50,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]