指定PING的网卡

 struct ifreq ifr;

 // 绑定在eth0上

 memset( &ifr, , sizeof( struct ifreq ) );

 snprintf( ifr.ifr_name, sizeof( ifr.ifr_name ), "%s", ifname );

 if ( setsockopt( fd, SOL_SOCKET, SO_BINDTODEVICE, ( const void* )&ifr, sizeof( struct ifreq ) ) == - )

 {

     perror( "setsockopt[SO_BINDTODEVICE]" );

     goto err_exit;

 }