C language linux network card detection improved version

The methods of C +shell to realize linux network card status detection and C to realize linux network card connection detection have their own defects. For example, some systems need root permission to execute ifconfig, or they do not support ioctl(fd, SIOCGMIIPHY, & ifr). The improved implementation of C language for linux card connection detection has the same function as C language +shell language for linux card status detection.

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
 
 
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/if.h>
#include <linux/mii.h>
#include <linux/sockios.h>
#include <errno.h>
 
#include <ifaddrs.h>
#include <arpa/inet.h> 
 
#include <linux/ethtool.h>
 
int cshell_netlink_status(char *if_name)
{
 char  buffer[BUFSIZ];
 char  cmd[100];
 FILE  *read_fp;
 int    chars_read;
 int    ret =0;
 
 memset( buffer, 0, BUFSIZ );
 memset( cmd, 0, 100 );
 sprintf(cmd, "ifconfig -a | grep %s",if_name);
 read_fp = popen(cmd, "r");
 if ( read_fp != NULL )
 {
 chars_read = fread(buffer, sizeof(char), BUFSIZ-1, read_fp);
 pclose(read_fp);
 
 if (chars_read > 0)
 {
  ret = 1;
 }
 else
 {
  fprintf(stderr, "DEVICE_NONE\r\n");
  return 0;
 }
 }
 
 if(ret == 1)
 {
 memset( buffer, 0, BUFSIZ );
 memset( cmd, 0, 100 );
 sprintf(cmd, "ifconfig |grep %s",if_name);
 read_fp = popen(cmd, "r");
 if ( read_fp != NULL )
 {
  chars_read = fread(buffer, sizeof(char), BUFSIZ-1, read_fp);
  pclose(read_fp);
 
  if (chars_read > 0)
  {
  ret = 2;
  }
  else
  {
  fprintf(stderr, "DEVICE_DOWN\r\n");
  return 1;
  }
 }
 }
 
 if(ret == 2)
 {
 memset( buffer, 0, BUFSIZ );
 memset( cmd, 0, 100 );
 sprintf(cmd, "ifconfig %s | grep RUNNING | awk '{print $3}'",if_name);
 read_fp = popen(cmd, "r");
 if ( read_fp != NULL )
 {
   chars_read = fread(buffer, sizeof(char), BUFSIZ-1, read_fp);
   pclose(read_fp);
  
   if (chars_read > 0)
   {
  fprintf(stderr, "DEVICE_LINKED\r\n");
  return 3;
   }
   else
   {
  fprintf(stderr, "DEVICE_UNPLUGGED\r\n");
  return 2;
   }
 }
 }
 
 return -1;
}
 
 
int c_netlink_status(const char *if_name )
{
 int fd = -1; 
 struct ifreq ifr; 
 
 struct ifconf ifc; 
 struct ifreq ifrs_buf[100]; 
 int if_number =0;
 int i;
 
 
 if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
 {
 fprintf(stderr, "%s: socket error [%d] %s\r\n",if_name, errno, strerror(errno));
 close(fd);
 return -1; 
 }
 
 ifc.ifc_len = sizeof(ifrs_buf); 
 ifc.ifc_buf = (caddr_t)ifrs_buf; 
 if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) <0) 
 {
 fprintf(stderr, "%s: ioctl SIOCGIFCONF error [%d] %s\r\n",if_name, errno, strerror(errno));
 close(fd);
 return -1; 
 }
 
 if_number = ifc.ifc_len / sizeof(struct ifreq);
 for(i=0; i< if_number; i++)
 {
 if(strcmp(if_name,ifrs_buf[i].ifr_name ) == 0)
 {
  break;
 }
 }
 
 if(i >= if_number)
 {
 close(fd);
 fprintf(stderr, "DEVICE_NONE\r\n");
 return 0;
 }
 
 bzero(&ifr, sizeof(ifr));
 strncpy(ifr.ifr_name, if_name, IFNAMSIZ-1); 
 ifr.ifr_name[IFNAMSIZ-1] = 0; 
 if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifr) <0) 
 {
 fprintf(stderr, "%s: ioctl SIOCGIFFLAGS error [%d] %s\r\n",if_name, errno, strerror(errno));
 close(fd);
 return -1; 
 }
#if 1 
 if(!(ifr.ifr_flags & IFF_UP))
 {
 close(fd);
 fprintf(stderr, "DEVICE_DOWN\r\n");
 return 1;
 }
 
 if(!(ifr.ifr_flags & IFF_RUNNING))
 {
 close(fd);
 fprintf(stderr, "DEVICE_UNPLUGGED\r\n");
 return 2 ;
 }
 
 fprintf(stderr, "DEVICE_LINKED\r\n");
 return 3;
 
#else
{
 struct ethtool_value edata;
 if(!(ifr.ifr_flags & IFF_UP) || !(ifr.ifr_flags & IFF_RUNNING))
 {
 close(fd);
 fprintf(stderr, "%s: DOWN\r\n",if_name);
 return 1;
 }
 edata.cmd = ETHTOOL_GLINK;
 edata.data = 0;
 ifr.ifr_data = (char *) &edata;
 if(ioctl( fd, SIOCETHTOOL, &ifr ) < 0)
 {
 fprintf(stderr, "%s: ioctl SIOCETHTOOL error [%d] %s\r\n",if_name, errno, strerror(errno));
 close(fd);
 return -1; 
 }
 
 if(edata.data == 0)
 {
 fprintf(stderr, "DEVICE_UNPLUGGED\r\n");
 return 2; 
 }
 else
 {
 fprintf(stderr, "DEVICE_LINKED\r\n");
 return 3; 
 }
}
#endif
}
 
int main(int argc, char* argv[])
{
 int i=0;
 if(argc != 2)
 {
 fprintf(stderr, "usage: %s <ethname>\r\n", argv[0]);
 return -1;
 }
 
 i = cshell_netlink_status(argv[1]);
 
 printf( "cshell_netlink_status if_status = %d\n", i );
 
 i = c_netlink_status(argv[1]);
 printf( "c_netlink_status if_status = %d\n", i );
 
 return 0;
}