src/ifspec.c

   1 // $Id: ifspec.c,v 1.1.4.1 2003/11/21 16:01:09 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 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <ctype.h>
  31 #include <unistd.h>
  32 #include <sys/socket.h>
  33 #include <sys/ioctl.h>
  34 #include <netinet/in.h>
  35 #include <net/if.h>
  36
  37 static void usage()
  38 {
  39         fprintf (stderr,"ifspec version %s\n",VERSION);
  40         fprintf (stderr
  41                 ,"ifspec network-device [ ipaddr netmask broadcast ]\n"
  42                  "prints device specification in a shell usable way\n");
  43         exit (-1);
  44 }
  45
  46 static int ifconfig_ioctl(
  47         int fd,
  48         const char *ifname,
  49         int cmd,
  50         struct ifreq *ifr)
  51 {
  52         strcpy(ifr->ifr_name, ifname);
  53         return ioctl(fd, cmd,ifr);
  54 }
  55
  56 static unsigned long ip_cnv (const char *str)
  57 {
  58         const char *start_str = str;
  59         unsigned tb[4];
  60         int no = 0;
  61         unsigned long ret;
  62
  63         memset (tb,-1,sizeof(tb));
  64         while (*str != '\0' && no < 4){
  65                 if (isdigit(*str)){
  66                         int val = atoi(str);
  67                         if (val > 255) break;
  68                         tb[no++] = val;
  69                         while (isdigit(*str)) str++;
  70                         if (*str == '.'){
  71                                 str++;
  72                         }else{
  73                                 break;
  74                         }
  75                 }else{
  76                         break;
  77                 }
  78         }
  79
  80         ret = (tb[0] << 24) | (tb[1]<<16) | (tb[2] << 8) | tb[3];
  81         if (no != 4 || *str != '\0'){
  82                 fprintf (stderr,"Invalid IP number or netmask: %s\n",start_str);
  83                 ret = 0xffffffff;
  84         }
  85         return ret;
  86 }
  87
  88
  89 /*
  90         Fetch the IP number of an interface from the kernel.
  91         Assume the device is already available in the kernel
  92         Return -1 if any error.
  93 */
  94 int ifconfig_print (
  95         const char *ifname,
  96         const char *addrstr,
  97         const char *maskstr,
  98         const char *bcaststr)
  99 {
 100         int ret = -1;
 101         int skfd = socket(AF_INET, SOCK_DGRAM, 0);
 102         if (skfd != -1){
 103                 struct ifreq ifr;
 104                 struct {
 105                         unsigned long addr;
 106                         unsigned long mask;
 107                 } solved = {0,0};
 108                 if (addrstr != NULL && addrstr[0] != '\0'){
 109                         printf ("ADDR=%s\n",addrstr);
 110                         solved.addr = ip_cnv (addrstr);
 111                 }else if (ifconfig_ioctl(skfd,ifname,SIOCGIFADDR, &ifr) >= 0){
 112                         struct sockaddr_in *sin = (struct sockaddr_in*)&ifr.ifr_addr;
 113                         unsigned long addr = ntohl(sin->sin_addr.s_addr);
 114                         printf ("ADDR=%lu.%lu.%lu.%lu\n"
 115                                 ,(addr>>24)&0xff
 116                                 ,(addr>>16)&0xff
 117                                 ,(addr>>8)&0xff
 118                                 ,addr&0xff);
 119                         solved.addr = addr;
 120                         ret = 0;
 121                 }
 122                 else {
 123                   perror("ioctl(SIOCGIFADDR)");
 124                 }
 125
 126                 if (maskstr != NULL && maskstr[0] != '\0'){
 127                         printf ("NETMASK=%s\n",maskstr);
 128                         solved.mask = ip_cnv (maskstr);
 129                 }else           if (ifconfig_ioctl(skfd,ifname,SIOCGIFNETMASK, &ifr) >= 0){
 130                         struct sockaddr_in *sin = (struct sockaddr_in*)&ifr.ifr_addr;
 131                         unsigned long addr = ntohl(sin->sin_addr.s_addr);
 132                         printf ("NETMASK=%lu.%lu.%lu.%lu\n"
 133                                 ,(addr>>24)&0xff
 134                                 ,(addr>>16)&0xff
 135                                 ,(addr>>8)&0xff
 136                                 ,addr&0xff);
 137                         solved.mask = addr;
 138                         ret = 0;
 139                 }
 140                 else {
 141                   perror("ioctl(SIOCGIFNETMASK)");
 142                 }
 143
 144                 if (bcaststr != NULL && bcaststr[0] != '\0'){
 145                         printf ("BCAST=%s\n",bcaststr);
 146                 }else if (ifconfig_ioctl(skfd,ifname,SIOCGIFBRDADDR, &ifr) >= 0){
 147                         struct sockaddr_in *sin = (struct sockaddr_in*)&ifr.ifr_addr;
 148                         unsigned long addr = ntohl(sin->sin_addr.s_addr);
 149                         printf ("BCAST=%lu.%lu.%lu.%lu\n"
 150                                 ,(addr>>24)&0xff
 151                                 ,(addr>>16)&0xff
 152                                 ,(addr>>8)&0xff
 153                                 ,addr&0xff);
 154                         ret = 0;
 155                 }else if (solved.addr!=0 && solved.mask!=0) {
 156                         // Can't get it from the kernel, compute it from the IP
 157                         // and the netmask
 158                         unsigned long addr = (solved.addr & solved.mask)
 159                                 | ~solved.mask;
 160                         printf ("BCAST=%lu.%lu.%lu.%lu\n"
 161                                 ,(addr>>24)&0xff
 162                                 ,(addr>>16)&0xff
 163                                 ,(addr>>8)&0xff
 164                                 ,addr&0xff);
 165
 166                 }
 167                 close (skfd);
 168         }
 169         return ret;
 170 }
 171
 172
 173 int main (int argc, char *argv[])
 174 {
 175         int ret = -1;
 176         if (argc < 2){
 177                 usage();
 178         }else{
 179                 const char *addrstr = argc >= 3 ? argv[2] : NULL;
 180                 const char *maskstr = argc >= 4 ? argv[3] : NULL;
 181                 const char *bcaststr = argc >= 5 ? argv[4] : NULL;
 182                 ret = ifconfig_print (argv[1],addrstr,maskstr,bcaststr);
 183         }
 184         return ret;
 185 }
 186
 187
 188