src/ifspec.c

   1 // $Id: ifspec.c,v 1.4 2004/02/20 16:59:40 ensc Exp $
   2
   3 // Copyright (C) 2003 Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de>
   4 // based on ifspec.cc by Jacques Gelinas
   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 2, or (at your option)
   9 // 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, write to the Free Software
  18 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19
  20 /*
  21         Prints the specs of a network device in shell like form
  22
  23         ADDR=
  24         NETMASK=
  25         BCAST=
  26 */
  27 #ifdef HAVE_CONFIG_H
  28 #  include <config.h>
  29 #endif
  30
  31 #include <stdio.h>
  32 #include <stdlib.h>
  33 #include <string.h>
  34 #include <ctype.h>
  35 #include <unistd.h>
  36 #include <sys/socket.h>
  37 #include <sys/ioctl.h>
  38 #include <netinet/in.h>
  39 #include <net/if.h>
  40
  41 static void usage()
  42 {
  43         fprintf (stderr,"ifspec version %s\n",VERSION);
  44         fprintf (stderr
  45                 ,"ifspec network-device [ ipaddr netmask broadcast ]\n"
  46                  "prints device specification in a shell usable way\n");
  47         exit (-1);
  48 }
  49
  50 static int ifconfig_ioctl(
  51         int fd,
  52         const char *ifname,
  53         int cmd,
  54         struct ifreq *ifr)
  55 {
  56         strcpy(ifr->ifr_name, ifname);
  57         return ioctl(fd, cmd,ifr);
  58 }
  59
  60 static unsigned long ip_cnv (const char *str)
  61 {
  62         const char *start_str = str;
  63         unsigned tb[4];
  64         int no = 0;
  65         unsigned long ret;
  66
  67         memset (tb,-1,sizeof(tb));
  68         while (*str != '\0' && no < 4){
  69                 if (isdigit(*str)){
  70                         int val = atoi(str);
  71                         if (val > 255) break;
  72                         tb[no++] = val;
  73                         while (isdigit(*str)) str++;
  74                         if (*str == '.'){
  75                                 str++;
  76                         }else{
  77                                 break;
  78                         }
  79                 }else{
  80                         break;
  81                 }
  82         }
  83
  84         ret = (tb[0] << 24) | (tb[1]<<16) | (tb[2] << 8) | tb[3];
  85         if (no != 4 || *str != '\0'){
  86                 fprintf (stderr,"Invalid IP number or netmask: %s\n",start_str);
  87                 ret = 0xffffffff;
  88         }
  89         return ret;
  90 }
  91
  92
  93 /*
  94         Fetch the IP number of an interface from the kernel.
  95         Assume the device is already available in the kernel
  96         Return -1 if any error.
  97 */
  98 int ifconfig_print (
  99         const char *ifname,
 100         const char *addrstr,
 101         const char *maskstr,
 102         const char *bcaststr)
 103 {
 104         int ret = -1;
 105         int skfd = socket(AF_INET, SOCK_DGRAM, 0);
 106         if (skfd != -1){
 107                 struct ifreq ifr;
 108                 struct {
 109                         unsigned long addr;
 110                         unsigned long mask;
 111                 } solved = {0,0};
 112                 if (addrstr != NULL && addrstr[0] != '\0'){
 113                         printf ("ADDR=%s\n",addrstr);
 114                         solved.addr = ip_cnv (addrstr);
 115                 }else if (ifconfig_ioctl(skfd,ifname,SIOCGIFADDR, &ifr) >= 0){
 116                         struct sockaddr_in *sin = (struct sockaddr_in*)&ifr.ifr_addr;
 117                         unsigned long addr = ntohl(sin->sin_addr.s_addr);
 118                         printf ("ADDR=%lu.%lu.%lu.%lu\n"
 119                                 ,(addr>>24)&0xff
 120                                 ,(addr>>16)&0xff
 121                                 ,(addr>>8)&0xff
 122                                 ,addr&0xff);
 123                         solved.addr = addr;
 124                         ret = 0;
 125                 }
 126                 else {
 127                   perror("ifspec: ioctl(SIOCGIFADDR)");
 128                 }
 129
 130                 if (maskstr != NULL && maskstr[0] != '\0'){
 131                         printf ("NETMASK=%s\n",maskstr);
 132                         solved.mask = ip_cnv (maskstr);
 133                 }else           if (ifconfig_ioctl(skfd,ifname,SIOCGIFNETMASK, &ifr) >= 0){
 134                         struct sockaddr_in *sin = (struct sockaddr_in*)&ifr.ifr_addr;
 135                         unsigned long addr = ntohl(sin->sin_addr.s_addr);
 136                         printf ("NETMASK=%lu.%lu.%lu.%lu\n"
 137                                 ,(addr>>24)&0xff
 138                                 ,(addr>>16)&0xff
 139                                 ,(addr>>8)&0xff
 140                                 ,addr&0xff);
 141                         solved.mask = addr;
 142                         ret = 0;
 143                 }
 144                 else {
 145                   perror("ifspec: ioctl(SIOCGIFNETMASK)");
 146                 }
 147
 148                 if (bcaststr != NULL && bcaststr[0] != '\0'){
 149                         printf ("BCAST=%s\n",bcaststr);
 150                 }else if (ifconfig_ioctl(skfd,ifname,SIOCGIFBRDADDR, &ifr) >= 0){
 151                         struct sockaddr_in *sin = (struct sockaddr_in*)&ifr.ifr_addr;
 152                         unsigned long addr = ntohl(sin->sin_addr.s_addr);
 153                         printf ("BCAST=%lu.%lu.%lu.%lu\n"
 154                                 ,(addr>>24)&0xff
 155                                 ,(addr>>16)&0xff
 156                                 ,(addr>>8)&0xff
 157                                 ,addr&0xff);
 158                         ret = 0;
 159                 }else if (solved.addr!=0 && solved.mask!=0) {
 160                         // Can't get it from the kernel, compute it from the IP
 161                         // and the netmask
 162                         unsigned long addr = (solved.addr & solved.mask)
 163                                 | ~solved.mask;
 164                         printf ("BCAST=%lu.%lu.%lu.%lu\n"
 165                                 ,(addr>>24)&0xff
 166                                 ,(addr>>16)&0xff
 167                                 ,(addr>>8)&0xff
 168                                 ,addr&0xff);
 169
 170                 }
 171                 close (skfd);
 172         }
 173         return ret;
 174 }
 175
 176
 177 int main (int argc, char *argv[])
 178 {
 179         int ret = -1;
 180         if (argc < 2){
 181                 usage();
 182         }else{
 183                 const char *addrstr = argc >= 3 ? argv[2] : NULL;
 184                 const char *maskstr = argc >= 4 ? argv[3] : NULL;
 185                 const char *bcaststr = argc >= 5 ? argv[4] : NULL;
 186                 ret = ifconfig_print (argv[1],addrstr,maskstr,bcaststr);
 187         }
 188         return ret;
 189 }
 190
 191
 192