ppp.c

PPP拨号协议简单实现 适用于MCU和无系统的嵌入式应用

			//--------------------------------------------------
			//  		如Server请求CHAP则NAK，并请求 PAP 			  //				
			//--------------------------------------------------
			if ((in_buff [8] == 0x03) && (in_buff [10] == 0xC2)) {
				in_buff [4] = NAK; 
				in_buff [10] = 0xC0; // We suggest PAP instead
				send_ppp (in_buff, (BYTE)(in_buff[7]+6));
			} else
			//--------------------------------------------------
			//   如SERVER请求PAP,则ACK，且发送PAP包进行密码认证     
			//--------------------------------------------------
			if((in_buff[7]==0x08) && (in_buff[8]==0x03)){
				in_buff[4]=ACK;
				send_ppp (in_buff, (BYTE)(in_buff [7] + 6));
				Delay(100);
				//send_pap (REQ, (BYTE)(in_buff[5] + 1), a60i.User, a60i.Pass);
				send_pap (REQ, (BYTE)(in_buff[5] + 1), "gprs", "gprs");
			}
			break;

		case ACK:

			break;

		case NAK:
			break;

		case REJ:
			break;

		case TERMINATE_ACK: // Terminate ACK!
			if (DebugMode)
				Debug("ASCEND-> TERMINATE_ACK");
			break;
		}
		return LCP_NORMAL;
}

//接收PPP包字节,组包的过程.
BYTE ppp_receive (BYTE c) 
{
	switch (c) {
		case ESC: // 0x7D 
				if (build)
					isEsc = 1;
				break; 
		case END: //7E
			isEsc=0;
			if (build) {
				if(frm_size==0)
				{
					memset(in_buff,0x00,PPP_BUFFER_SIZE + 1);
					frm_size = 0;
					build=0x01;
				}else
				{
					in_buff[frm_size] = 0;
					build=0x00;
					frm_size = 0;
					return 1;
				}
			}
			else{
				memset(in_buff,0x00,PPP_BUFFER_SIZE + 1);
				frm_size = 0;
				build=0x01;
			}
			break;
		default:
			if (build){
				if (isEsc){
					in_buff[frm_size++]=0x20 ^ c;
					isEsc=0;
				}else{
					in_buff[frm_size++] = c;
				}
			}
			break;
	}
	return 0;
}


//发送密码校验包
void send_pap (BYTE Action, BYTE ID, char* user, char* password) {
	out_buff [0] = 0xFF;
	out_buff [1] = 0x03;
	out_buff [2] = 0xC0; // Format PAP packet header
	out_buff [3] = 0x23;
	out_buff [4] = Action;
	out_buff [5] = in_buff [5] + 1; // Increment ID
	out_buff [6] = 0;
	out_buff [7] = strlen (user) + strlen (password) + 6;// Set length of PAP
	out_buff [8] = strlen (user); // Set length of
	
	// Username lee
	//move (user, &out_buff [9], strlen (user)); // Store Username
	memcpy(&out_buff[9],user,strlen(user));
	
	out_buff [9 + strlen (user)] = strlen (password); // Set length of
	
	// password lee
	//move (password, &out_buff [10 + strlen (user)], strlen (password));
	memcpy(&out_buff [10 + strlen (user)],password,strlen(password));
	
	
	send_ppp ((BYTE *)out_buff, (BYTE)(out_buff[7] + 6)); // Send PAP packet
}

//IPCP,分配IP地址.
BYTE do_ipcp (void) {
	BYTE *dest = (BYTE *)&out_buff[8];
	BYTE *ptr = (BYTE *)&in_buff[8];
//	char IPStr[40];
	BYTE FrameSize;
	BYTE Option;
	BYTE Size;
	switch (in_buff [4] ) {
	case REQ:
		if ((in_buff [8] != 0x03) && (in_buff [7] > 0x0A)) {
			out_buff [0] = 0xFF;
			out_buff [1] = 0x03;
			out_buff [2] = 0x80; // Set IPCP protocol
			out_buff [3] = 0x21;
			out_buff [4] = REJ; // This will be a
			// REJ packet for now
			out_buff [5] = in_buff [5];
			out_buff [6] = 0x00;
			FrameSize = in_buff[7] - 4;
			///////// Ignore all but option #3 ///////
			while (FrameSize > 0) {
				Option = *ptr;
				Size = *(ptr + 1);
				FrameSize -= Size;
				if (Option == 3) {
					ptr += Size;
					//Set New Packet size
					out_buff [7] = in_buff [7] - Size;
				}
				else {
					while (Size-- ) {
						*dest++ = *ptr++;
					}
				}
			}

		}
		else {
		// Acknowledge IP Address //
			move (in_buff, out_buff, in_buff[7]+6);
			out_buff [4] = ACK;
			send_ppp ((BYTE *)out_buff, (BYTE)(out_buff[7] + 6));
			// Now Request IP address to complete 3-way handshake
			out_buff [4] = REQ; // Request command
			out_buff [5] = out_buff [5] + 1; // Packet ID = ID + 1
			out_buff [10] = 0; // IP address is set
			// to 0 so ISP server
			out_buff [11] = 0; // can assing us one
			out_buff [12] = 0;
			out_buff [13] = 0;
		}
		send_ppp ((BYTE *)out_buff, (BYTE)(out_buff[7] + 6));
		break;
	case ACK:
		if (in_buff [8] == 3) { // Reply of the only IPCP
			// Request we can send
			IPAddress [0] = in_buff [10]; // ISP assigned IP
			IPAddress [1] = in_buff [11];
			IPAddress [2] = in_buff [12];
			IPAddress [3] = in_buff [13];
			return PPP_OK;
		}
		break;
	case NAK:
		if ((in_buff [8] == 0x03) && (in_buff [7] <= 0x0A)) {
			/// Request IP Address ////
			move (in_buff, out_buff, in_buff[7]+8);
			out_buff [4] = 0x01;
			send_ppp ((BYTE *)out_buff, (BYTE)(out_buff[7] + 6));
		}
		break;
	case REJ:
		break;
	}
	return IPCP_NORMAL;
}

//把打成PPP发送到串口
void send_ppp (BYTE *Buffer, int len) {
	WORD Checksum;
	int i;
	
    Checksum=0; 
	
	//添加校验位
	Checksum = ppp_checksum (Buffer, len-2);
	Buffer [ len-2] = Checksum & 0xFF;
	Buffer [ len-1] = (Checksum >> 8) & 0xFF;

	if (DebugMode)
	{
		SendByte2UART0(0x01);
		SendByte2UART0(0x7E);
		SendBuf2UART0 (Buffer,len);
		SendByte2UART0(0x7E);
	}	
	
	SendChar2Modem(0x7E);//起始位
	//包内容
	for (i=0;i<len;i++){
		if (Buffer[i] < 0x20) {//小于0x20的字节需要转义,祥见PPP协议
			msend (0x7D);
			msend ((BYTE)(Buffer[i] ^ 0x20));
		} else {
			switch (Buffer[i]) {
				case 0x7E:
					msend (0x7D);
					msend (0x5E);
					break;
				case 0x7D:	//转义符
					msend (0x7D);
					msend (0x5D);
					break;
				default:
					msend (Buffer[i]);
					break;
			}
		}
	}
	SendChar2Modem (0x7E);	//结束位.
}


static WORD PPPfcs16 (WORD fcs, BYTE *cp, int len) {
	while (len--)
	fcs = (fcs >> 8) ^ fcstab[(fcs ^ *cp++) & 0xff];
	return (fcs);
}


WORD ppp_checksum (register unsigned char *cp, register int len) {
	return ~PPPfcs16( PPPINITFCS16, cp, len );
}


//检测是否是断开回应包

int ppp_disconnect(void)
{
	switch (in_buff [4] ) 
	{//
		case TERMINATE: //断开包,则回应ACK
			move (in_buff, out_buff, in_buff[7]+6);
			out_buff [4] = TERMINATE_ACK;
			send_ppp ((BYTE *)out_buff, (BYTE)(out_buff[7] + 6));	
			return 2;
			break;	
		case TERMINATE_ACK://是断开回应包
			return 1;
			break;
		default:
			break;
	}
	return 0;
}


//PPP断开,这里我们采用稍微复杂的流程,以确保PPP能断开
int disconnect(void)
{
	uint32 t;
	int i;
	char chr;
	ppp_terminate();//发送断开包

    Debug("\r\n start disconnect.\r\n");
    
	mstimeout(&t,0);
	
	//--------------------------------
	//这里还存在挂不断的情况！
	//--------------------------------
	while(1)
	{
		if (read_mb(&chr)) //检测是否有数据到达
		{ 
			if (ppp_receive(chr)) //能组成一个完整的PPP包?
			{
				if (ppp_disconnect()) //处理收到的PPP包(目前只处理 teminate seq 和 teminate ack 包,其他的包置之不理)
				{  //如果收到 teminate seq(则回应 teminate ack)  或 teminate ack 
					check_at_return(40); //检测AT
					delay(1000); //
					return(1);
				}
			}		
		}
		if (mstimeout(&t,5000))//5秒超时
		{
			
			if (i==10)
				return 0;
			if (check_at_return(40))//检测AT是否返回
				return 1;
			delay(400);
			ppp_terminate();	//AT没有返回则继续发送断开包
			i++;	
		}
		FeedWdt();	
	}
	
}