resolve_host.c

   1 /*
   2  * resolving DNS hostname routine
   3  *
   4  * Copyright (C) 2010 Jeff Layton (jlayton@samba.org)
   5  * Copyright (C) 2010 Igor Druzhinin (jaxbrigs@gmail.com)
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 3 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #ifdef HAVE_CONFIG_H
  22 #include "config.h"
  23 #endif /* HAVE_CONFIG_H */
  24
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <sys/socket.h>
  28 #include <arpa/inet.h>
  29 #include <netdb.h>
  30 #include "mount.h"
  31 #include "util.h"
  32 #include "resolve_host.h"
  33
  34 /*
  35  * resolve hostname to comma-separated list of address(es)
  36  */
  37 int resolve_host(const char *host, char *addrstr)
  38 {
  39         int rc;
  40         /* 10 for max width of decimal scopeid */
  41         char tmpbuf[NI_MAXHOST + 1 + 10 + 1];
  42         const char *ipaddr;
  43         size_t len;
  44         struct addrinfo *addrlist, *addr;
  45         struct sockaddr_in *sin;
  46         struct sockaddr_in6 *sin6;
  47
  48         rc = getaddrinfo(host, NULL, NULL, &addrlist);
  49         if (rc != 0)
  50                 return EX_USAGE;
  51
  52         addr = addrlist;
  53         while (addr) {
  54                 /* skip non-TCP entries */
  55                 if (addr->ai_socktype != SOCK_STREAM ||
  56                     addr->ai_protocol != IPPROTO_TCP) {
  57                         addr = addr->ai_next;
  58                         continue;
  59                 }
  60
  61                 switch (addr->ai_addr->sa_family) {
  62                 case AF_INET6:
  63                         sin6 = (struct sockaddr_in6 *)addr->ai_addr;
  64                         ipaddr = inet_ntop(AF_INET6, &sin6->sin6_addr, tmpbuf,
  65                                            sizeof(tmpbuf));
  66                         if (!ipaddr) {
  67                                 rc = EX_SYSERR;
  68                                 goto resolve_host_out;
  69                         }
  70
  71                         if (sin6->sin6_scope_id) {
  72                                 len = strnlen(tmpbuf, sizeof(tmpbuf));
  73                                 snprintf(tmpbuf + len, sizeof(tmpbuf) - len, "%%%u",
  74                                          sin6->sin6_scope_id);
  75                         }
  76                         break;
  77                 case AF_INET:
  78                         sin = (struct sockaddr_in *)addr->ai_addr;
  79                         ipaddr = inet_ntop(AF_INET, &sin->sin_addr, tmpbuf,
  80                                            sizeof(tmpbuf));
  81                         if (!ipaddr) {
  82                                 rc = EX_SYSERR;
  83                                 goto resolve_host_out;
  84                         }
  85
  86                         break;
  87                 default:
  88                         addr = addr->ai_next;
  89                         continue;
  90                 }
  91
  92                 if (addr == addrlist)
  93                         *addrstr = '\0';
  94                 else
  95                         strlcat(addrstr, ",", MAX_ADDR_LIST_LEN);
  96
  97                 strlcat(addrstr, tmpbuf, MAX_ADDR_LIST_LEN);
  98                 addr = addr->ai_next;
  99         }
 100
 101 resolve_host_out:
 102         freeaddrinfo(addrlist);
 103         return rc;
 104 }