src/resolve/resolved-dns-answer.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2014 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include "resolved-dns-answer.h"
  23 #include "dns-domain.h"
  24
  25 DnsAnswer *dns_answer_new(unsigned n) {
  26         DnsAnswer *a;
  27
  28         a = malloc0(offsetof(DnsAnswer, rrs) + sizeof(DnsResourceRecord*) * n);
  29         if (!a)
  30                 return NULL;
  31
  32         a->n_ref = 1;
  33         a->n_allocated = n;
  34
  35         return a;
  36 }
  37
  38 DnsAnswer *dns_answer_ref(DnsAnswer *a) {
  39         if (!a)
  40                 return NULL;
  41
  42         assert(a->n_ref > 0);
  43         a->n_ref++;
  44         return a;
  45 }
  46
  47 DnsAnswer *dns_answer_unref(DnsAnswer *a) {
  48         if (!a)
  49                 return NULL;
  50
  51         assert(a->n_ref > 0);
  52
  53         if (a->n_ref == 1) {
  54                 unsigned i;
  55
  56                 for (i = 0; i < a->n_rrs; i++)
  57                         dns_resource_record_unref(a->rrs[i]);
  58
  59                 free(a);
  60         } else
  61                 a->n_ref--;
  62
  63         return NULL;
  64 }
  65
  66 int dns_answer_add(DnsAnswer *a, DnsResourceRecord *rr) {
  67         unsigned i;
  68         int r;
  69
  70         assert(a);
  71         assert(rr);
  72
  73         for (i = 0; i < a->n_rrs; i++) {
  74                 r = dns_resource_record_equal(a->rrs[i], rr);
  75                 if (r < 0)
  76                         return r;
  77                 if (r > 0) {
  78                         /* Entry already exists, keep the entry with
  79                          * the higher RR, or the one with TTL 0 */
  80
  81                         if (rr->ttl == 0 || (rr->ttl > a->rrs[i]->ttl && a->rrs[i]->ttl != 0)) {
  82                                 dns_resource_record_ref(rr);
  83                                 dns_resource_record_unref(a->rrs[i]);
  84                                 a->rrs[i] = rr;
  85                         }
  86
  87                         return 0;
  88                 }
  89         }
  90
  91         if (a->n_rrs >= a->n_allocated)
  92                 return -ENOSPC;
  93
  94         a->rrs[a->n_rrs++] = dns_resource_record_ref(rr);
  95         return 1;
  96 }
  97
  98 int dns_answer_add_soa(DnsAnswer *a, const char *name, uint32_t ttl) {
  99         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *soa = NULL;
 100
 101         soa = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_SOA, name);
 102         if (!soa)
 103                 return -ENOMEM;
 104
 105         soa->ttl = ttl;
 106
 107         soa->soa.mname = strdup(name);
 108         if (!soa->soa.mname)
 109                 return -ENOMEM;
 110
 111         soa->soa.rname = strappend("root.", name);
 112         if (!soa->soa.rname)
 113                 return -ENOMEM;
 114
 115         soa->soa.serial = 1;
 116         soa->soa.refresh = 1;
 117         soa->soa.retry = 1;
 118         soa->soa.expire = 1;
 119         soa->soa.minimum = ttl;
 120
 121         return dns_answer_add(a, soa);
 122 }
 123
 124 int dns_answer_contains(DnsAnswer *a, DnsResourceKey *key) {
 125         unsigned i;
 126         int r;
 127
 128         assert(a);
 129         assert(key);
 130
 131         for (i = 0; i < a->n_rrs; i++) {
 132                 r = dns_resource_key_match_rr(key, a->rrs[i]);
 133                 if (r < 0)
 134                         return r;
 135                 if (r > 0)
 136                         return 1;
 137         }
 138
 139         return 0;
 140 }
 141
 142 int dns_answer_find_soa(DnsAnswer *a, DnsResourceKey *key, DnsResourceRecord **ret) {
 143         unsigned i;
 144
 145         assert(a);
 146         assert(key);
 147         assert(ret);
 148
 149         /* For a SOA record we can never find a matching SOA record */
 150         if (key->type == DNS_TYPE_SOA)
 151                 return 0;
 152
 153         for (i = 0; i < a->n_rrs; i++) {
 154
 155                 if (a->rrs[i]->key->class != DNS_CLASS_IN)
 156                         continue;
 157
 158                 if (a->rrs[i]->key->type != DNS_TYPE_SOA)
 159                         continue;
 160
 161                 if (dns_name_endswith(DNS_RESOURCE_KEY_NAME(key), DNS_RESOURCE_KEY_NAME(a->rrs[i]->key))) {
 162                         *ret = a->rrs[i];
 163                         return 1;
 164                 }
 165         }
 166
 167         return 0;
 168 }
 169
 170 DnsAnswer *dns_answer_merge(DnsAnswer *a, DnsAnswer *b) {
 171         _cleanup_(dns_answer_unrefp) DnsAnswer *ret = NULL;
 172         DnsAnswer *k;
 173         unsigned i;
 174         int r;
 175
 176         if (a && (!b || b->n_rrs <= 0))
 177                 return dns_answer_ref(a);
 178         if ((!a || a->n_rrs <= 0) && b)
 179                 return dns_answer_ref(b);
 180
 181         ret = dns_answer_new((a ? a->n_rrs : 0) + (b ? b->n_rrs : 0));
 182         if (!ret)
 183                 return NULL;
 184
 185         if (a) {
 186                 for (i = 0; i < a->n_rrs; i++) {
 187                         r = dns_answer_add(ret, a->rrs[i]);
 188                         if (r < 0)
 189                                 return NULL;
 190                 }
 191         }
 192
 193         if (b) {
 194                 for (i = 0; i < b->n_rrs; i++) {
 195                         r = dns_answer_add(ret, b->rrs[i]);
 196                         if (r < 0)
 197                                 return NULL;
 198                 }
 199         }
 200
 201         k = ret;
 202         ret = NULL;
 203
 204         return k;
 205 }
 206
 207 void dns_answer_order_by_scope(DnsAnswer *a, bool prefer_link_local) {
 208         DnsResourceRecord **rrs;
 209         unsigned i, start, end;
 210         assert(a);
 211
 212         if (a->n_rrs <= 1)
 213                 return;
 214
 215         start = 0;
 216         end = a->n_rrs-1;
 217
 218         /* RFC 4795, Section 2.6 suggests we should order entries
 219          * depending on whether the sender is a link-local address. */
 220
 221         rrs = newa(DnsResourceRecord*, a->n_rrs);
 222         for (i = 0; i < a->n_rrs; i++) {
 223
 224                 if (a->rrs[i]->key->class == DNS_CLASS_IN &&
 225                     ((a->rrs[i]->key->type == DNS_TYPE_A && in_addr_is_link_local(AF_INET, (union in_addr_union*) &a->rrs[i]->a.in_addr) != prefer_link_local) ||
 226                      (a->rrs[i]->key->type == DNS_TYPE_AAAA && in_addr_is_link_local(AF_INET6, (union in_addr_union*) &a->rrs[i]->aaaa.in6_addr) != prefer_link_local)))
 227                         /* Order address records that are are not preferred to the end of the array */
 228                         rrs[end--] = a->rrs[i];
 229                 else
 230                         /* Order all other records to the beginning of the array */
 231                         rrs[start++] = a->rrs[i];
 232         }
 233
 234         assert(start == end+1);
 235         memcpy(a->rrs, rrs, sizeof(DnsResourceRecord*) * a->n_rrs);
 236 }