test.c

这是tftp协议的具体实现

typedef unsigned char u8;	//unsigned char
typedef unsigned short u16;	//unsigned short
typedef unsigned int u32;	//unsigned int
 

struct MAC{
	u8 bDstMac[6];
	u8 bSrcMac[6];
	u16 wMacType;
}__attribute__((packed)) Mac, *MacHead;

struct IPHEAD{
	u8		bHeadLen:4;
	u8		bVersion:4;   
	u8		bTos;					// type of service
	u16		wTotalLen;				//IP数据包总长度，不包括MACHEAD部
	u16		wIdent;					// unique identifier
	u16		wFlags;          
	u8		bTtl;            		
	u8		bTransType;				//传输层协议类型(TCP,UDP,ICMP等)
	u16		wChecksum;       
	u32		nSrcIp;
	u32		nDstIp;
}__attribute__((packed)) Ip, *IpHead;

struct VUDPHEAD{
	u32 nSrcIp;
	u32 nDstIp;
	u8 bZero;
	u8 bProto;
	u16 wUdpLen;
}__attribute__((packed)) Vudp, *VudpHead;


struct UDPHEAD{
    u16 wSrcPort;					//Source port
    u16 wDstPort;					//Destination port
    u16 wLen;						//Datagram length
    u16 wCheckSum;					//Checksum
}__attribute__((packed)) Udp, *UdpHead;

u16 Checksum(u16 *pwData,u32 nSize)
{
	u32 nChksum=0;
	while(nSize>1){
		nChksum+=*pwData++;
		nSize-=sizeof(u16);
	}
	if(nSize)
		nChksum+=*(u8*)pwData;
	nChksum=(nChksum>>16)+(nChksum&0xffff);
	nChksum+=(nChksum>>16);
	return (u16)(~nChksum);
}

int BuildPacket(u8 *PacketPage, u8 *FileName)
{
	int i, j , useLen, macLen, ipLen, vudpLen, udpLen, tmpInt;
	char tmpCh, *tmp8;
	u16 *tmp16;
	u32 *tmp32;
	u8 MacInit[6]={0x00,0x11,0x22,0x33,0x44,0x55} ;
	u8 HostMac[6]={0x00,0x14,0x38,0x12,0x0a,0xbf};
	u8 HostIp[]={0xc0,0xa8,0x00,0x01};
	u8 ClientIp[]={0xc0,0xa8,0x00,0x6f};

	char Prot[]={"octet"};

	//MacHead build
	for(i = 0; i < 6; i++)
	{
		Mac.bDstMac[i] = HostMac[i];
		Mac.bSrcMac[i] = MacInit[i];
	}
	Mac.wMacType = 0x0800;
	MacHead = &Mac;
	macLen=14;

	// IpHead build
	Ip.bHeadLen = 0x5;
	Ip.bVersion = 0x4;
	Ip.bTos = 0;
	Ip.wTotalLen = 0x0042;
	Ip.wIdent = 0x0000;
	Ip.wFlags = 0x4000;
	Ip.bTtl = 0x40;
	Ip.bTransType = 0x11;
	Ip.wChecksum = 0;
	Ip.nSrcIp = (ClientIp[0]<<8)|(ClientIp[1]<<8)|(ClientIp[2]<<8)|(ClientIp[3]<<8);
	Ip.nDstIp = (HostIp[0]<<8)|(HostIp[1]<<8)|(HostIp[2]<<8)|(HostIp[3]<<8);
	IpHead = &Ip;
	ipLen=20;
	IpHead->wChecksum=Checksum((u16 *)IpHead,20);

	//UseData
	vudpLen=12;
	udpLen=8;
	tmpInt=macLen+ipLen+vudpLen+udpLen;
	PacketPage[tmpInt]=0x00;
	PacketPage[tmpInt+1]=0x01;
	for(i=0;FileName[i]!='\0';i++)
		PacketPage[2+tmpInt+i]=FileName[i];
	for(j=0;Prot[j]!='\0';j++)
		PacketPage[i+1+j+tmpInt]=Prot[j];
	useLen=i+j+4;

	// VudpHead build
	Vudp.nSrcIp= IpHead->nSrcIp;
	Vudp.nDstIp= IpHead->nDstIp;
	Vudp.bZero= 0;
	Vudp.bProto= 0x11;
	Vudp.wUdpLen=useLen+udpLen;
	VudpHead = &Vudp;
	vudpLen=12;

	//UdpHead build
	Udp.wSrcPort = 0xb315;
	Udp.wDstPort =0x45 ;
	Udp.wLen=useLen+udpLen;
	Udp.wCheckSum=0x0;
	UdpHead = &Udp;
	//to link
	*(struct MAC *)PacketPage= *MacHead;
	*(struct IPHEAD *)(PacketPage+macLen)=*IpHead;
	for(i=0;i<4;i++)
	{
		PacketPage[macLen+12+i]=ClientIp[i];
		PacketPage[macLen+16+i]=HostIp[i];
	}
	*(struct VUDPHEAD *)(PacketPage+macLen+ipLen)=*VudpHead;
//	*(PacketPage+macLen+ipLen)=VudpHead;
	*(struct UDPHEAD *)(PacketPage+macLen+ipLen+vudpLen)=*UdpHead;
	
	for(i=0;i<77;i++)
		printf("%x",PacketPage[i]);


	//clear VudpHead
/*	tmpInt = macLen+ipLen;
	for(i=0;i<udpLen+useLen;i++)
	{
		PacketPage[tmpInt+i]=PacketPage[tmpInt+vudpLen+i];
	}
	for(i=0;i<vudpLen;i++)
	{	
		PacketPage[tmpInt+udpLen+useLen+i]='\0';	
	}*/
	return macLen+ipLen+udpLen+useLen;
}

int main()
{
	int  i = 0, len;
	char PacketPage[1024], FileName[]={"abcdefghijklmnopqrstuvwxyz"};
	len=BuildPacket(PacketPage, FileName);
	printf("len = %d\n",len);
	for(i=0;i<len;i++){
		if(i%10==0)
			printf("\n");
		printf("%x",PacketPage[i]);
	}
	return 0;
}