libcli/dns/resolvconf.c

   1 /*
   2  *  Unix SMB/CIFS implementation.
   3  *  Internal DNS query structures
   4  *  Copyright (C) Volker Lendecke 2018
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "replace.h"
  21 #include <stdio.h>
  22 #include <errno.h>
  23 #include "libcli/dns/resolvconf.h"
  24 #include "lib/util/memory.h"
  25
  26 int parse_resolvconf_fp(
  27         FILE *fp,
  28         TALLOC_CTX *mem_ctx,
  29         char ***pnameservers,
  30         size_t *pnum_nameservers)
  31 {
  32         char *line = NULL;
  33         size_t len = 0;
  34         char **nameservers = NULL;
  35         size_t num_nameservers = 0;
  36         int ret = 0;
  37
  38         while (true) {
  39                 char *saveptr, *option, *ns;
  40                 char **tmp;
  41                 ssize_t n;
  42
  43                 n = getline(&line, &len, fp);
  44                 if (n < 0) {
  45                         if (!feof(fp)) {
  46                                 /* real error */
  47                                 ret = errno;
  48                         }
  49                         break;
  50                 }
  51                 if ((n > 0) && (line[n-1] == '\n')) {
  52                         line[n-1] = '\0';
  53                 }
  54
  55                 if ((line[0] == '#') || (line[0] == ';')) {
  56                         continue;
  57                 }
  58
  59                 option = strtok_r(line, " \t", &saveptr);
  60                 if (option == NULL) {
  61                         continue;
  62                 }
  63
  64                 if (strcmp(option, "nameserver") != 0) {
  65                         continue;
  66                 }
  67
  68                 ns = strtok_r(NULL, " \t", &saveptr);
  69                 if (ns == NULL) {
  70                         continue;
  71                 }
  72
  73                 tmp = talloc_realloc(
  74                         mem_ctx,
  75                         nameservers,
  76                         char *,
  77                         num_nameservers+1);
  78                 if (tmp == NULL) {
  79                         ret = ENOMEM;
  80                         break;
  81                 }
  82                 nameservers = tmp;
  83
  84                 nameservers[num_nameservers] = talloc_strdup(nameservers, ns);
  85                 if (nameservers[num_nameservers] == NULL) {
  86                         ret = ENOMEM;
  87                         break;
  88                 }
  89                 num_nameservers += 1;
  90         }
  91
  92         SAFE_FREE(line);
  93
  94         if (ret == 0) {
  95                 *pnameservers = nameservers;
  96                 *pnum_nameservers = num_nameservers;
  97         } else {
  98                 TALLOC_FREE(nameservers);
  99         }
 100
 101         return ret;
 102 }
 103
 104 int parse_resolvconf(
 105         const char *resolvconf,
 106         TALLOC_CTX *mem_ctx,
 107         char ***pnameservers,
 108         size_t *pnum_nameservers)
 109 {
 110         FILE *fp;
 111         int ret;
 112
 113         fp = fopen(resolvconf ? resolvconf : "/etc/resolv.conf", "r");
 114         if (fp == NULL) {
 115                 return errno;
 116         }
 117
 118         ret = parse_resolvconf_fp(fp, mem_ctx, pnameservers, pnum_nameservers);
 119
 120         fclose(fp);
 121
 122         return ret;
 123 }