C언어로 MAC 어드레스 받아오기 (Linux)

#include "stdio.h"
#include "string.h"
#include "net/if.h"
#include "sys/ioctl.h"

//
// Global public data
//
unsigned char cMacAddr[8]; // Server's MAC address

static int GetSvrMacAddress( char *pIface )
{
int nSD; // Socket descriptor
struct ifreq sIfReq; // Interface request
struct if_nameindex *pIfList; // Ptr to interface name index
struct if_nameindex *pListSave; // Ptr to interface name index

//
// Initialize this function
//
pIfList = (struct if_nameindex *)NULL;
pListSave = (struct if_nameindex *)NULL;
#ifndef SIOCGIFADDR
// The kernel does not support the required ioctls
return( 0 );
#endif

//
// Create a socket that we can use for all of our ioctls
//
nSD = socket( PF_INET, SOCK_STREAM, 0 );
if ( nSD < 0 )
{
// Socket creation failed, this is a fatal error
printf( "File %s: line %d: Socket failed\n", __FILE__, __LINE__ );
return( 0 );
}

//
// Obtain a list of dynamically allocated structures
//
pIfList = pListSave = if_nameindex();

//
// Walk thru the array returned and query for each interface's
// address
//
for ( pIfList; *(char *)pIfList != 0; pIfList++ )
{
//
// Determine if we are processing the interface that we
// are interested in
//
if ( strcmp(pIfList->if_name, pIface) )
// Nope, check the next one in the list
continue;
strncpy( sIfReq.ifr_name, pIfList->if_name, IF_NAMESIZE );

//
// Get the MAC address for this interface
//
if ( ioctl(nSD, SIOCGIFHWADDR, &sIfReq) != 0 )
{
// We failed to get the MAC address for the interface
printf( "File %s: line %d: Ioctl failed\n", __FILE__, __LINE__ );
return( 0 );
}
memmove( (void *)&cMacAddr[0], (void *)&sIfReq.ifr_ifru.ifru_hwaddr.sa_data[0], 6 );
break;
}

//
// Clean up things and return
//
if_freenameindex( pListSave );
close( nSD );
return( 1 );
}

int main( int argc, char * argv[] )
{
//
// Initialize this program
//
bzero( (void *)&cMacAddr[0], sizeof(cMacAddr) );
if ( !GetSvrMacAddress("eth0") )
{
// We failed to get the local host's MAC address
printf( "Fatal error: Failed to get local host's MAC address\n" );
}
printf( "HWaddr %02X:%02X:%02X:%02X:%02X:%02X\n",
cMacAddr[0], cMacAddr[1], cMacAddr[2],
cMacAddr[3], cMacAddr[4], cMacAddr[5] );

//
// And exit
//
exit( 0 );
}

[링크 : http://www.linuxquestions.org/questions/programming-9/getting-mac-address-with-c-linux-325037/]

위의 소스 작동하는 것 확인함.
아무튼, struct ifreq 에 ioctl함수로 받아오는 식으로 구현되어 있음.

man 7 netdevice

struct ifreq {        char ifr_name[IFNAMSIZ]; /* Interface name */        union {            struct sockaddr ifr_addr;            struct sockaddr ifr_dstaddr;            struct sockaddr ifr_broadaddr;            struct sockaddr ifr_netmask;            struct sockaddr ifr_hwaddr;            short           ifr_flags;            int           ifr_ifindex;            int           ifr_metric;            int           ifr_mtu;            struct ifmap    ifr_map;            char           ifr_slave[IFNAMSIZ];            char           ifr_newname[IFNAMSIZ];            char *           ifr_data;        };        }; [링크 : http://unixhelp.ed.ac.uk/CGI/man-cgi?netdevice+7]

$ vi /usr/inclue/bits/socket.h 161 /* Structure describing a generic socket address.  */ 162 struct sockaddr 163   { 164     __SOCKADDR_COMMON (sa_);    /* Common data: address family and length.  */ 165     char sa_data[14];           /* Address data.  */ 166   };

[링크 : http://adywicaksono.wordpress.com/2007/11/08/detecting-mac-address-using-c-application/]
[링크 : http://www.joinc.co.kr/modules/moniwiki/wiki.php/Code/C/ifinfo]