네트워크 상태 체크 질문입니다.

ifconfig 해보시면

eth0 Link encap:Ethernet HWaddr 00:02:9E:00:03:A9
inet addr:111.111.111.111 Bcast:192.168.33.255 Mask:255.255.255.0
UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
RX packets:380160 errors:0 dropped:0 overruns:0 frame:0
TX packets:46156 errors:6 dropped:0 overruns:6 carrier:6
collisions:0 txqueuelen:100
RX bytes:536201499 (511.3 Mb) TX bytes:2944513 (2.8 Mb)
Interrupt:10 Base address:0x8000

여기서 RUNNING 상태가 선의 연결상태입니다.
그러면 이 플래그는 어떻게 얻어올까라는 질문을 던지시겠죠?

예전에 여기 한번 올렸던거 같은데 모르겠네요. 다시 올립니다.

/*
 Copyright (c) 2002 Information Equipment co.,LTD.
 All Right Reserved.

 Code by JaeHyuk Cho <minzkn@infoeq.co.kr>

 - Simple is best
 
*/

#if !defined(DEF_ifconfig_c)
#define DEF_ifconfig_c "ifconfig.c"

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <net/if.h>
#include <netinet/if_ether.h>
#include <arpa/inet.h>
#include <netdb.h>

int main(int s_Argc, char **s_Argv);

int main(int s_Argc, char **s_Argv)
{
 int s_SocketHandle;	
 int s_RequestCount = 10;
 struct ifconf s_ifconfig;
 struct ifreq *s_ifrequest;
 struct sockaddr_in *s_SockAddr_In;
 
 char s_StringBuffer[1 << 10];
 char *s_MyTitle;
 char *s_MyDevice;
 char *s_MyIP, *s_MyBroadcastIP, *s_MyNetmaskIP;
 char *s_MyHWAddr;
 char *s_MyFlagString;
 int  s_MyFlags, s_MyMTU, s_MyMetric;
 fprintf(stdout, "MZ_ifconfig v0.0.1b - Copyright(c)InfoEQ co.,LTD - %s %s\n", __DATE__, __TIME__);
 fprintf(stdout, "Code by JaeHyuk Cho - <minzkn@infoeq.co.kr>\n\n");
 s_SocketHandle = socket(AF_INET, SOCK_DGRAM, 0);
 if(s_SocketHandle >= 0)
 {
  memset((void *)&s_ifconfig, 0, sizeof(struct ifconf));
  do
  {
   if(s_ifconfig.ifc_buf)free(s_ifconfig.ifc_buf);
   s_ifconfig.ifc_len = sizeof(struct ifreq) * s_RequestCount;
   s_ifconfig.ifc_buf = malloc(s_ifconfig.ifc_len);
   if(s_ifconfig.ifc_buf)
   {
    if(ioctl(s_SocketHandle, SIOCGIFCONF, &s_ifconfig) == 0)
    {
     if(s_ifconfig.ifc_len < (sizeof(struct ifreq) * s_RequestCount))
     {
      s_ifrequest = s_ifconfig.ifc_req;
      if(s_ifrequest)
      {
       for(s_RequestCount = 0;s_RequestCount < s_ifconfig.ifc_len;s_RequestCount += sizeof(struct ifreq), s_ifrequest++)
       {
        /* ------------------------------------------------------------------------ */	       
	s_MyDevice = strdup(s_ifrequest->ifr_name);
	
	ioctl(s_SocketHandle, SIOCGIFADDR, s_ifrequest);        
	s_SockAddr_In       = (struct sockaddr_in *)(&s_ifrequest->ifr_addr);
        s_MyIP              = strdup(inet_ntoa(s_SockAddr_In->sin_addr));	
	ioctl(s_SocketHandle, SIOCGIFBRDADDR, s_ifrequest);        
	s_SockAddr_In       = (struct sockaddr_in *)&s_ifrequest->ifr_broadaddr;
        s_MyBroadcastIP     = strdup(inet_ntoa(s_SockAddr_In->sin_addr));	
	ioctl(s_SocketHandle, SIOCGIFNETMASK, s_ifrequest);        
	s_SockAddr_In       = (struct sockaddr_in *)&s_ifrequest->ifr_netmask;
        s_MyNetmaskIP       = strdup(inet_ntoa(s_SockAddr_In->sin_addr));	
	
	if(ioctl(s_SocketHandle, SIOCGIFHWADDR, s_ifrequest) == 0)
	{
	 unsigned char s_NullHWAddr[] = {0, 0, 0, 0, 0, 0};
         if(memcmp(&s_ifrequest->ifr_hwaddr.sa_data[0], &s_NullHWAddr[0], sizeof(s_NullHWAddr)) == 0)
	 {
          strcpy(s_StringBuffer, "");
	 }
	 else
	 {
	  sprintf(s_StringBuffer, "HWAddr %02x:%02x:%02x:%02x:%02x:%02x",
		 s_ifrequest->ifr_hwaddr.sa_data[0] & 0xff,
		 s_ifrequest->ifr_hwaddr.sa_data[1] & 0xff,
		 s_ifrequest->ifr_hwaddr.sa_data[2] & 0xff,
		 s_ifrequest->ifr_hwaddr.sa_data[3] & 0xff,
		 s_ifrequest->ifr_hwaddr.sa_data[4] & 0xff,
		 s_ifrequest->ifr_hwaddr.sa_data[5] & 0xff
	        );
	 }
	}
	else strcpy(s_StringBuffer, "HWAddr <ERROR>");
	s_MyHWAddr = strdup(s_StringBuffer);
	
	if(ioctl(s_SocketHandle, SIOCGIFFLAGS, s_ifrequest) == 0)s_MyFlags = s_ifrequest->ifr_flags;
	else s_MyFlags = 0;
       	strcpy(s_StringBuffer, "");
	if(s_MyFlags == 0)strcpy(s_StringBuffer, "[NO FLAGS]");
	else
	{
	 if(s_MyFlags & IFF_UP          )strcat(s_StringBuffer, "UP ");	
	 if(s_MyFlags & IFF_BROADCAST   )strcat(s_StringBuffer, "BROADCAST ");	
	 if(s_MyFlags & IFF_DEBUG       )strcat(s_StringBuffer, "DEBUG ");	
	 if(s_MyFlags & IFF_LOOPBACK    )strcat(s_StringBuffer, "LOOPBACK ");	
	 if(s_MyFlags & IFF_POINTOPOINT )strcat(s_StringBuffer, "POINTOPOINT ");	
	 if(s_MyFlags & IFF_NOTRAILERS  )strcat(s_StringBuffer, "NOTRAILERS ");	
	 if(s_MyFlags & IFF_RUNNING     )strcat(s_StringBuffer, "RUNNING ");	
	 if(s_MyFlags & IFF_NOARP       )strcat(s_StringBuffer, "NOARP ");	
	 if(s_MyFlags & IFF_PROMISC     )strcat(s_StringBuffer, "PROMISC ");	
	 if(s_MyFlags & IFF_ALLMULTI    )strcat(s_StringBuffer, "ALLMULTI ");	
	 if(s_MyFlags & IFF_SLAVE       )strcat(s_StringBuffer, "SLAVE ");	
	 if(s_MyFlags & IFF_MASTER      )strcat(s_StringBuffer, "MASTER ");	
	 if(s_MyFlags & IFF_MULTICAST   )strcat(s_StringBuffer, "MULTICAST ");	
	}
	s_MyFlagString = strdup(s_StringBuffer);

        s_MyTitle = strdup("Unknown"); /* Not support */ 
	
	if(ioctl(s_SocketHandle, SIOCGIFMTU, s_ifrequest) == 0)s_MyMTU = s_ifrequest->ifr_mtu;
	else s_MyMTU = 0;
	
	if(ioctl(s_SocketHandle, SIOCGIFMETRIC, s_ifrequest) == 0)s_MyMetric = s_ifrequest->ifr_metric;
	else s_MyMetric = 0;
        
	/* Print. */
	fprintf(stdout, 
		"%-8s Link encap:%s  %s\n"
		"%-8s inet addr %-15s  Broadcast %-15s  Netmask %-15s\n"
		"%-8s %s MTU:%d Metric:%d\n"
		"\n", 
	        s_MyDevice, s_MyTitle, s_MyHWAddr,
		"", s_MyIP, s_MyBroadcastIP, s_MyNetmaskIP,
		"", s_MyFlagString, s_MyMTU, s_MyMetric ? s_MyMetric : 1
	       );
	
	/* Free. */
	if(s_MyTitle      )free(s_MyTitle);
	if(s_MyDevice     )free(s_MyDevice);
	if(s_MyIP         )free(s_MyIP);
	if(s_MyBroadcastIP)free(s_MyBroadcastIP);
	if(s_MyNetmaskIP  )free(s_MyNetmaskIP);
	if(s_MyHWAddr     )free(s_MyHWAddr);
	if(s_MyFlagString )free(s_MyFlagString);
        /* ------------------------------------------------------------------------ */	       
       }
      }
      break; 
     }
     else s_RequestCount += 10; 
    }
    else break;
   }
   else break;
  }while(1);  
  if(s_ifconfig.ifc_buf)free(s_ifconfig.ifc_buf);
  close(s_SocketHandle);	  
 }
 else fprintf(stderr, "Can not open socket !!!\n");
 return(0);
}

#endif 

/* End of source */