Wake-on-LAN(远端唤醒) 原理及实现

Wake-on-LAN简称WOL或WoL，我们一般将其称为“网络唤醒”、“远端唤醒”技术。WOL是一种技术，同时也是该技术的规范标准，它的功效在于让已经进入休眠状态或关机状态的电脑，透过局域网（多半为以太网）的另一端对其发令，使其从休眠状态唤醒、恢复成运作状态，或从关机状态转成开机状态。此外，与WOL相关的技术也包括远端下令关机、远端下令重新开机等相关的遥控机制。

Wake-on-LAN功能需要有主板和网卡的支持，在主板BIOS中的网卡设置中必须有“Wake On LAN”设置（开启：On），并且相应网卡也得支持该功能。因为，在关闭计算机以后，其实网卡仍然通电的（unless 你把插排电源也关了），这样你就可以通过发送一段Magic Packet给网卡，让网卡将计算机唤醒。

Magic Packet
Magic Packet是一个广播帧（frame），透过端口7或端口9进行发送，且可以用无连接（Connectionless protocol）的通讯协议（如UDP、IPX）来传递，不过一般而言多是用UDP，原因是Novell公司的Netware网络操作系统的IPX协定已经很少使用。
在Magic Packet内，每次都会先有连续6个"FF"（十六进制，换算成二进制即：11111111）的资料，即：FF FF FF FF FF FF，在连续6个"FF"后则开始带出MAC地址，有时还会带出4字节或6字节的密码，一旦经由网卡侦测、解读、研判（广播）Magic Packet的内容，内容中的MAC地址、密码若与电脑自身的地址、密码吻合，就会启动唤醒、开机的程序。

示例:
假设你的网卡物理地址为00:15:17:53:d4:f9, 这段Magic Packet内容如下:

    FFFFFFFFFFFF00151753d4f900151753d4f900151753d4f900151753d4f9
    00151753d4f900151753d4f900151753d4f900151753d4f900151753d4f9
    00151753d4f900151753d4f900151753d4f900151753d4f900151753d4f9
    00151753d4f900151753d4f9

 

以下是根据wakelan代码修改的工具,添加了绑定网卡的支持(参数 -i devname).

/* * * Copyright (C) 1998 by Christopher Chan-Nui * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * */ #define HAVE_GETOPT_H #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <netdb.h> #include <netinet/in.h> #include <sys/socket.h> #ifdef HAVE_GETOPT_H #include <getopt.h> #endif #include <errno.h> #include <net/if.h> //#include <linux/if.h> #ifndef DEFAULTMAC #define DEFAULTMAC "00a0c9852a5f" #endif #ifndef DEFAULTTARGET #define DEFAULTTARGET "255.255.255.255" #endif static char *rcsid="@(#) $Id: wakelan.c,v 1.8 1998/08/30 05:04:28 channui Exp $"; static void *use_rcsid = ( void * )( ( char * )&use_rcsid || ( void * )&rcsid ); char *versionid = "1.0"; void usage( char *name ) { printf ( "Usage: %s [options] [mac] [broadcast] [port]/n" " -b addr broadcast address/n" " -m mac mac address of host/n" " -p port UDP port to broadcast to/n" " -i dev bind socket to net device/n" " -v[v] version/n" , name ); exit ( 0 ); } int parse_mac( unsigned char *mac, char *str ) { int i; int count; char c; unsigned char val; int colon_ok = 1; for ( i = 0; i < 6; i++ ) { mac[i] = 0; } for ( i = 0; i < 6; i++ ) { count = 0; val = 0; do { c = toupper( *str++ ); if ( c >= '0' && c <= '9' ) { val = ( val * 16 ) + ( c - '0' ); } else if ( c >= 'A' && c <= 'F' ) { val = ( val * 16 ) + ( c - 'A' ) + 10; } else if ( c == ':' ) { if ( colon_ok || count-- != 0 ) break; } else if ( c == '/0' ) { str--; break; } else { return 0; } colon_ok=1; } while ( ++count < 2 ); colon_ok=( count<2 ); *mac++ = val; } if ( *str ) return 0; return 1; } int main ( int argc, char *argv[] ) { int sock; int optval = 1; int version =0; int i, j, c, rc; char msg[1024]; int msglen = 0; struct sockaddr_in bcast; struct hostent *he; struct in_addr inaddr; unsigned char macaddr[6]; char *mac = DEFAULTMAC; char *target = DEFAULTTARGET; short bport = htons( 32767 ); struct ifreq if_bind; char *devname = NULL; while ( ( c = getopt( argc, argv, "hvp:m:b:i:" ) ) != EOF ) { switch ( c ) { case 'b': target = optarg; break; case 'm': mac = optarg; break; case 'p': bport = htons( atoi( optarg ) ); break; case 'v': version++; break; case 'i': devname = optarg; break; case 'h': case '?': usage( argv[0] ); } } if ( version ) { printf ( "Version: %s/n", versionid ); if ( version > 1 ) { printf ( " RCSID: %s/n", rcsid ); } exit ( 0 ); } if ( argv[optind] != NULL ) { mac = argv[optind++]; } if ( argv[optind] != NULL ) { target = argv[optind++]; } if ( argv[optind] != NULL ) { bport = htons( atoi( argv[optind++] ) ); } if ( argv[optind] != NULL ) { usage( argv[0] ); } if ( !parse_mac( macaddr, mac ) ) { printf ( "Illegal MAC address '%s'/n", mac ); exit ( 1 ); } if ( !inet_aton( target, &inaddr ) ) { he = gethostbyname( target ); inaddr = *( struct in_addr * )he->h_addr_list[0]; } for ( i = 0; i < 6; i++ ) { msg[msglen++] = 0xff; } for ( i = 0; i < 16; i++ ) { for ( j = 0; j < sizeof( macaddr ); j++ ) { msg[msglen++] = macaddr[j]; } } memset( &bcast, 0, sizeof( bcast ) ); bcast.sin_family = AF_INET; bcast.sin_addr.s_addr = inaddr.s_addr; bcast.sin_port = bport; sock = socket( AF_INET, SOCK_DGRAM, 0 ); if ( sock < 0 ) { printf ( "Can't allocate socket/n" ); exit ( 1 ); } rc = setsockopt( sock, SOL_SOCKET, SO_BROADCAST, &optval, sizeof( optval ) ); if ( rc < 0 ) { printf ( "Can't socket option SO_BROADCAST: rc = %d, errno=%s(%d)/n", rc, strerror( errno ), errno ); exit ( 1 ); } if ( NULL != devname ) { memset( &if_bind, 0x0, sizeof( if_bind ) ); strncpy( if_bind.ifr_name, devname, IFNAMSIZ ); rc = setsockopt( sock, SOL_SOCKET, SO_BINDTODEVICE, &if_bind, sizeof( if_bind ) ); if ( rc < 0 ) { printf( "Can't socket option SO_BINDTODEVICE: rc = %d, errno=%s(%d)/n", rc, strerror( errno ), errno ); exit( 1 ); } } sendto( sock, &msg, msglen, 0, ( struct sockaddr * )&bcast, sizeof( bcast ) ); close( sock ); return 0; }
参考:

 Wake on LAN mini HOWTO http://gsd.di.uminho.pt/jpo/software/wakeonlan/mini-howto/
 Wake-on-LAN  http://en.wikipedia.org/wiki/Wake-on-LAN
 wakelan      Author: Christopher Chan-Nui ftp://metalab.unc.edu/pub/Linux/system/network/misc/wakelan-1.1.tar.gz