2 * iterator/iter_resptype.c - response type information and classification.
4 * Copyright (c) 2007, NLnet Labs. All rights reserved.
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9 * modification, are permitted provided that the following conditions
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39 * This file defines the response type. DNS Responses can be classified as
40 * one of the response types.
43 #include "iterator/iter_resptype.h"
44 #include "iterator/iter_delegpt.h"
45 #include "services/cache/dns.h"
46 #include "util/net_help.h"
47 #include "util/data/dname.h"
48 #include "sldns/rrdef.h"
49 #include "sldns/pkthdr.h"
52 response_type_from_cache(struct dns_msg* msg,
53 struct query_info* request)
55 /* If the message is NXDOMAIN, then it is an ANSWER. */
56 if(FLAGS_GET_RCODE(msg->rep->flags) == LDNS_RCODE_NXDOMAIN)
57 return RESPONSE_TYPE_ANSWER;
58 if(request->qtype == LDNS_RR_TYPE_ANY)
59 return RESPONSE_TYPE_ANSWER;
61 /* First we look at the answer section. This can tell us if this is
62 * CNAME or positive ANSWER. */
63 if(msg->rep->an_numrrsets > 0) {
64 /* Now look at the answer section first. 3 states:
65 * o our answer is there directly,
66 * o our answer is there after a cname,
67 * o or there is just a cname. */
68 uint8_t* mname = request->qname;
69 size_t mname_len = request->qname_len;
71 for(i=0; i<msg->rep->an_numrrsets; i++) {
72 struct ub_packed_rrset_key* s = msg->rep->rrsets[i];
74 /* If we have encountered an answer (before or
75 * after a CNAME), then we are done! Note that
76 * if qtype == CNAME then this will be noted as
77 * an ANSWER before it gets treated as a CNAME,
79 if(ntohs(s->rk.type) == request->qtype &&
80 ntohs(s->rk.rrset_class) == request->qclass &&
81 query_dname_compare(mname, s->rk.dname) == 0) {
82 return RESPONSE_TYPE_ANSWER;
85 /* If we have encountered a CNAME, make sure that
87 if(ntohs(s->rk.type) == LDNS_RR_TYPE_CNAME &&
88 query_dname_compare(mname, s->rk.dname) == 0) {
89 get_cname_target(s, &mname, &mname_len);
93 /* if we encountered a CNAME (or a bunch of CNAMEs), and
94 * still got to here, then it is a CNAME response. (i.e.,
95 * the CNAME chain didn't terminate in an answer rrset.) */
96 if(mname != request->qname) {
97 return RESPONSE_TYPE_CNAME;
101 /* At this point, since we don't need to detect REFERRAL or LAME
102 * messages, it can only be an ANSWER. */
103 return RESPONSE_TYPE_ANSWER;
107 response_type_from_server(int rdset,
108 struct dns_msg* msg, struct query_info* request, struct delegpt* dp)
110 uint8_t* origzone = (uint8_t*)"\000"; /* the default */
111 struct ub_packed_rrset_key* s;
115 return RESPONSE_TYPE_THROWAWAY;
117 /* If the message is NXDOMAIN, then it answers the question. */
118 if(FLAGS_GET_RCODE(msg->rep->flags) == LDNS_RCODE_NXDOMAIN) {
119 /* make sure its not recursive when we don't want it to */
120 if( (msg->rep->flags&BIT_RA) &&
121 !(msg->rep->flags&BIT_AA) && !rdset)
122 return RESPONSE_TYPE_REC_LAME;
123 /* it could be a CNAME with NXDOMAIN rcode */
124 for(i=0; i<msg->rep->an_numrrsets; i++) {
125 s = msg->rep->rrsets[i];
126 if(ntohs(s->rk.type) == LDNS_RR_TYPE_CNAME &&
127 query_dname_compare(request->qname,
129 return RESPONSE_TYPE_CNAME;
132 return RESPONSE_TYPE_ANSWER;
135 /* Other response codes mean (so far) to throw the response away as
136 * meaningless and move on to the next nameserver. */
137 if(FLAGS_GET_RCODE(msg->rep->flags) != LDNS_RCODE_NOERROR)
138 return RESPONSE_TYPE_THROWAWAY;
140 /* Note: TC bit has already been handled */
146 /* First we look at the answer section. This can tell us if this is a
147 * CNAME or ANSWER or (provisional) ANSWER. */
148 if(msg->rep->an_numrrsets > 0) {
149 uint8_t* mname = request->qname;
150 size_t mname_len = request->qname_len;
152 /* Now look at the answer section first. 3 states: our
153 * answer is there directly, our answer is there after
154 * a cname, or there is just a cname. */
155 for(i=0; i<msg->rep->an_numrrsets; i++) {
156 s = msg->rep->rrsets[i];
158 /* if the answer section has NS rrset, and qtype ANY
159 * and the delegation is lower, and no CNAMEs followed,
160 * this is a referral where the NS went to AN section */
161 if((request->qtype == LDNS_RR_TYPE_ANY ||
162 request->qtype == LDNS_RR_TYPE_NS) &&
163 ntohs(s->rk.type) == LDNS_RR_TYPE_NS &&
164 ntohs(s->rk.rrset_class) == request->qclass &&
165 dname_strict_subdomain_c(s->rk.dname,
167 if((msg->rep->flags&BIT_AA))
168 return RESPONSE_TYPE_ANSWER;
169 return RESPONSE_TYPE_REFERRAL;
172 /* If we have encountered an answer (before or
173 * after a CNAME), then we are done! Note that
174 * if qtype == CNAME then this will be noted as an
175 * ANSWER before it gets treated as a CNAME, as
177 if(ntohs(s->rk.type) == request->qtype &&
178 ntohs(s->rk.rrset_class) == request->qclass &&
179 query_dname_compare(mname, s->rk.dname) == 0) {
180 if((msg->rep->flags&BIT_AA))
181 return RESPONSE_TYPE_ANSWER;
182 /* If the AA bit isn't on, and we've seen
183 * the answer, we only provisionally say
184 * 'ANSWER' -- it very well could be a
189 /* If we have encountered a CNAME, make sure that
191 if(ntohs(s->rk.type) == LDNS_RR_TYPE_CNAME &&
192 query_dname_compare(mname, s->rk.dname) == 0) {
193 get_cname_target(s, &mname, &mname_len);
196 /* not a referral, and qtype any, thus an answer */
197 if(request->qtype == LDNS_RR_TYPE_ANY)
198 return RESPONSE_TYPE_ANSWER;
199 /* if we encountered a CNAME (or a bunch of CNAMEs), and
200 * still got to here, then it is a CNAME response.
201 * (This is regardless of the AA bit at this point) */
202 if(mname != request->qname) {
203 return RESPONSE_TYPE_CNAME;
207 /* Looking at the authority section, we just look and see if
208 * there is a SOA record, that means a NOERROR/NODATA */
209 for(i = msg->rep->an_numrrsets; i < (msg->rep->an_numrrsets +
210 msg->rep->ns_numrrsets); i++) {
211 s = msg->rep->rrsets[i];
213 /* The normal way of detecting NOERROR/NODATA. */
214 if(ntohs(s->rk.type) == LDNS_RR_TYPE_SOA &&
215 dname_subdomain_c(request->qname, s->rk.dname)) {
216 /* we do our own recursion, thank you */
217 if( (msg->rep->flags&BIT_RA) &&
218 !(msg->rep->flags&BIT_AA) && !rdset)
219 return RESPONSE_TYPE_REC_LAME;
220 return RESPONSE_TYPE_ANSWER;
223 /* Looking at the authority section, we just look and see if
224 * there is a delegation NS set, turning it into a delegation.
225 * Otherwise, we will have to conclude ANSWER (either it is
226 * NOERROR/NODATA, or an non-authoritative answer). */
227 for(i = msg->rep->an_numrrsets; i < (msg->rep->an_numrrsets +
228 msg->rep->ns_numrrsets); i++) {
229 s = msg->rep->rrsets[i];
231 /* Detect REFERRAL/LAME/ANSWER based on the relationship
232 * of the NS set to the originating zone name. */
233 if(ntohs(s->rk.type) == LDNS_RR_TYPE_NS) {
234 /* If we are getting an NS set for the zone we
235 * thought we were contacting, then it is an answer.*/
236 if(query_dname_compare(s->rk.dname, origzone) == 0) {
237 /* see if mistakenly a recursive server was
238 * deployed and is responding nonAA */
239 if( (msg->rep->flags&BIT_RA) &&
240 !(msg->rep->flags&BIT_AA) && !rdset)
241 return RESPONSE_TYPE_REC_LAME;
242 /* Or if a lame server is deployed,
243 * which gives ns==zone delegation from cache
244 * without AA bit as well, with nodata nosoa*/
245 /* real answer must be +AA and SOA RFC(2308),
246 * so this is wrong, and we SERVFAIL it if
247 * this is the only possible reply, if it
248 * is misdeployed the THROWAWAY makes us pick
249 * the next server from the selection */
250 if(msg->rep->an_numrrsets==0 &&
251 !(msg->rep->flags&BIT_AA) && !rdset)
252 return RESPONSE_TYPE_THROWAWAY;
253 return RESPONSE_TYPE_ANSWER;
255 /* If we are getting a referral upwards (or to
256 * the same zone), then the server is 'lame'. */
257 if(dname_subdomain_c(origzone, s->rk.dname)) {
258 if(rdset) /* forward or reclame not LAME */
259 return RESPONSE_TYPE_THROWAWAY;
260 return RESPONSE_TYPE_LAME;
262 /* If the NS set is below the delegation point we
263 * are on, and it is non-authoritative, then it is
264 * a referral, otherwise it is an answer. */
265 if(dname_subdomain_c(s->rk.dname, origzone)) {
266 /* NOTE: I no longer remember in what case
267 * we would like this to be an answer.
268 * NODATA should have a SOA or nothing,
270 * True, referrals should not have the AA
273 /* if((msg->rep->flags&BIT_AA))
274 return RESPONSE_TYPE_ANSWER; */
275 return RESPONSE_TYPE_REFERRAL;
277 /* Otherwise, the NS set is irrelevant. */
281 /* If we've gotten this far, this is NOERROR/NODATA (which could
282 * be an entirely empty message) */
283 /* check if recursive answer; saying it has empty cache */
284 if( (msg->rep->flags&BIT_RA) && !(msg->rep->flags&BIT_AA) && !rdset)
285 return RESPONSE_TYPE_REC_LAME;
286 return RESPONSE_TYPE_ANSWER;