5d27351f85
Apart from dropping redundant information, this fixes an issue where, due to broken DNS servers, we can only be certain of whether an apparent NODATA response is in fact an NXDOMAIN response after explicitly resolving the canonical name. This issue is outlined in RFC2308. Moreover, by caching NXDOMAIN for an existing name, we would mistakenly return NXDOMAIN for types which should not be redirected. I.e., a query for AAAA on test-nx-1.jklm.no correctly returns NXDOMAIN, but a query for CNAME should return the record and a query for DNAME should return NODATA. Note that this means we will not cache an NXDOMAIN response in the presence of redirection, meaning one redundant roundtrip in case the name is queried again.
99 lines
4.1 KiB
C
99 lines
4.1 KiB
C
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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#pragma once
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/***
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This file is part of systemd.
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Copyright 2014 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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typedef struct DnsAnswer DnsAnswer;
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typedef struct DnsAnswerItem DnsAnswerItem;
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#include "macro.h"
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#include "resolved-dns-rr.h"
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/* A simple array of resource records. We keep track of the
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* originating ifindex for each RR where that makes sense, so that we
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* can qualify A and AAAA RRs referring to a local link with the
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* right ifindex.
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*
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* Note that we usually encode the empty answer as a simple NULL. */
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struct DnsAnswerItem {
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DnsResourceRecord *rr;
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int ifindex;
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};
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struct DnsAnswer {
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unsigned n_ref;
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unsigned n_rrs, n_allocated;
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DnsAnswerItem items[0];
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};
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DnsAnswer *dns_answer_new(unsigned n);
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DnsAnswer *dns_answer_ref(DnsAnswer *a);
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DnsAnswer *dns_answer_unref(DnsAnswer *a);
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int dns_answer_add(DnsAnswer *a, DnsResourceRecord *rr, int ifindex);
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int dns_answer_add_extend(DnsAnswer **a, DnsResourceRecord *rr, int ifindex);
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int dns_answer_add_soa(DnsAnswer *a, const char *name, uint32_t ttl);
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int dns_answer_match_key(DnsAnswer *a, const DnsResourceKey *key);
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int dns_answer_contains_rr(DnsAnswer *a, DnsResourceRecord *rr);
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int dns_answer_find_soa(DnsAnswer *a, const DnsResourceKey *key, DnsResourceRecord **ret);
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int dns_answer_find_cname_or_dname(DnsAnswer *a, const DnsResourceKey *key, DnsResourceRecord **ret);
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int dns_answer_merge(DnsAnswer *a, DnsAnswer *b, DnsAnswer **ret);
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int dns_answer_extend(DnsAnswer **a, DnsAnswer *b);
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void dns_answer_order_by_scope(DnsAnswer *a, bool prefer_link_local);
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int dns_answer_reserve(DnsAnswer **a, unsigned n_free);
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int dns_answer_reserve_or_clone(DnsAnswer **a, unsigned n_free);
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int dns_answer_remove_by_key(DnsAnswer **a, const DnsResourceKey *key);
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int dns_answer_copy_by_key(DnsAnswer **a, DnsAnswer *source, const DnsResourceKey *key);
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static inline unsigned dns_answer_size(DnsAnswer *a) {
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return a ? a->n_rrs : 0;
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}
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DEFINE_TRIVIAL_CLEANUP_FUNC(DnsAnswer*, dns_answer_unref);
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#define _DNS_ANSWER_FOREACH(q, kk, a) \
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for (unsigned UNIQ_T(i, q) = ({ \
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(kk) = ((a) && (a)->n_rrs > 0) ? (a)->items[0].rr : NULL; \
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0; \
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}); \
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(a) && (UNIQ_T(i, q) < (a)->n_rrs); \
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UNIQ_T(i, q)++, (kk) = (UNIQ_T(i, q) < (a)->n_rrs ? (a)->items[UNIQ_T(i, q)].rr : NULL))
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#define DNS_ANSWER_FOREACH(kk, a) _DNS_ANSWER_FOREACH(UNIQ, kk, a)
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#define _DNS_ANSWER_FOREACH_IFINDEX(q, kk, ifi, a) \
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for (unsigned UNIQ_T(i, q) = ({ \
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(kk) = ((a) && (a)->n_rrs > 0) ? (a)->items[0].rr : NULL; \
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(ifi) = ((a) && (a)->n_rrs > 0) ? (a)->items[0].ifindex : 0; \
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0; \
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}); \
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(a) && (UNIQ_T(i, q) < (a)->n_rrs); \
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UNIQ_T(i, q)++, (kk) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].rr : NULL), (ifi) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].ifindex : 0))
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#define DNS_ANSWER_FOREACH_IFINDEX(kk, ifindex, a) _DNS_ANSWER_FOREACH_IFINDEX(UNIQ, kk, ifindex, a)
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