message.c

linux下bt下载C源码

#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <sys/socket.h>
#include "parse_metafile.h"
#include "bitfield.h"
#include "peer.h"
#include "data.h"
#include "policy.h"
#include "message.h"

#define HANDSHAKE   -2
#define KEEP_ALIVE  -1
#define CHOKE        0
#define UNCHOKE      1
#define INTERESTED   2
#define UNINTERESTED 3
#define HAVE         4
#define BITFIELD     5
#define REQUEST      6
#define PIECE        7
#define CANCEL       8
#define PORT         9

#define KEEP_ALIVE_TIME 45

extern Bitmap *bitmap;
extern char    info_hash[20];
extern char    peer_id[20];
extern int     have_piece_index[64];
extern Peer   *peer_head;

int int_to_char(int i, unsigned char c[4])
{
	c[3] = i%256;
	c[2] = (i-c[3])/256%256;
	c[1] = (i-c[3]-c[2]*256)/256/256%256;
	c[0] = (i-c[3]-c[2]*256-c[1]*256*256)/256/256/256%256;

	return 0;
}

int char_to_int(unsigned char c[4])
{
	int i;

	i = c[0]*256*256*256 + c[1]*256*256 + c[2]*256 + c[3];
	
	return i;
}

int create_handshake_msg(char *info_hash,char *peer_id,Peer *peer)
{
	int            i;
	unsigned char  keyword[20] = "BitTorrent protocol", c = 0x00;
	unsigned char  *buffer = peer->out_msg + peer->msg_len;
	int            len = MSG_SIZE - peer->msg_len;

	if(len < 68)  return -1;  // 68为握手消息的固定长度

	buffer[0] = 19;
	for(i = 0; i < 19; i++)  buffer[i+1]  = keyword[i];
	for(i = 0; i < 8;  i++)  buffer[i+20] = c;
	for(i = 0; i < 20; i++)  buffer[i+28] = info_hash[i];
	for(i = 0; i < 20; i++)  buffer[i+48] = peer_id[i];

	peer->msg_len += 68;
	return 0;
}

int create_keep_alive_msg(Peer *peer)
{
	unsigned char  *buffer = peer->out_msg + peer->msg_len;
	int            len = MSG_SIZE - peer->msg_len;

	if(len < 4)  return -1;  // 4为keep_alive消息的固定长度

	memset(buffer,0,4);
	peer->msg_len += 4;
	return 0;
}

int create_chock_interested_msg(int type,Peer *peer)
{
	unsigned char  *buffer = peer->out_msg + peer->msg_len;
	int            len = MSG_SIZE - peer->msg_len;

	// 5为choke、unchoke、interested、uninterested消息的固定长度
	if(len < 5)  return -1;

	memset(buffer,0,5);
	buffer[3] = 1;
	buffer[4] = type;

	peer->msg_len += 5;
	return 0;
}

int create_have_msg(int index,Peer *peer)
{
	unsigned char  *buffer = peer->out_msg + peer->msg_len;
	int            len = MSG_SIZE - peer->msg_len;
	unsigned char  c[4];

	if(len < 9)  return -1;  // 9为have消息的固定长度
	
	memset(buffer,0,9);	
	buffer[3] = 5;
	buffer[4] = 4;
	
	int_to_char(index,c);
	buffer[5] = c[0];
	buffer[6] = c[1];
	buffer[7] = c[2];
	buffer[8] = c[3];
	
	peer->msg_len += 9;
	return 0;
}

int create_bitfield_msg(char *bitfield,int bitfield_len,Peer *peer)
{
	int            i;
	unsigned char  c[4];
	unsigned char  *buffer = peer->out_msg + peer->msg_len;
	int            len = MSG_SIZE - peer->msg_len;

	if( len < bitfield_len+5 )  {  // bitfield消息的长度为bitfield_len+5
		printf("%s:%d buffer too small\n",__FILE__,__LINE__); 
		return -1;
	}

	int_to_char(bitfield_len+1,c);
	for(i = 0; i < 4; i++)  buffer[i] = c[i];
	buffer[4] = 5;
	for(i = 0; i < bitfield_len; i++) buffer[i+5] = bitfield[i];

	peer->msg_len += bitfield_len+5;  
	return 0;
}

int create_request_msg(int index,int begin,int length,Peer *peer)
{
	int            i;
	unsigned char  c[4];
	unsigned char  *buffer = peer->out_msg + peer->msg_len;
	int            len = MSG_SIZE - peer->msg_len;

	if(len < 17)  return -1;  // 17为request消息的固定长度

	memset(buffer,0,17);
	buffer[3] = 13;
	buffer[4] = 6;
	int_to_char(index,c);
	for(i = 0; i < 4; i++)  buffer[i+5]  = c[i];
	int_to_char(begin,c);
	for(i = 0; i < 4; i++)  buffer[i+9]  = c[i];
	int_to_char(length,c);
	for(i = 0; i < 4; i++)  buffer[i+13] = c[i];

	peer->msg_len += 17;
	return 0;
}

int create_piece_msg(int index,int begin,char *block,int b_len,Peer *peer)
{
	int            i;
	unsigned char  c[4];
	unsigned char  *buffer = peer->out_msg + peer->msg_len;
	int            len = MSG_SIZE - peer->msg_len;

	if( len < b_len+13 ) {  // piece消息的长度为b_len+13
		printf("IP:%s len:%d\n",peer->ip,len);
		printf("%s:%d buffer too small\n",__FILE__,__LINE__); 
		return -1;
	}
	
	int_to_char(b_len+9,c);
	for(i = 0; i < 4; i++)      buffer[i]    = c[i];
	buffer[4] = 7;
	int_to_char(index,c);
	for(i = 0; i < 4; i++)      buffer[i+5]  = c[i];
	int_to_char(begin,c);
	for(i = 0; i < 4; i++)      buffer[i+9]  = c[i];
	for(i = 0; i < b_len; i++)  buffer[i+13] = block[i];

	peer->msg_len += b_len+13;  
	return 0;
}

int create_cancel_msg(int index,int begin,int length,Peer *peer)
{
	int            i;
	unsigned char  c[4];
	unsigned char  *buffer = peer->out_msg + peer->msg_len;
	int            len = MSG_SIZE - peer->msg_len;
	
	if(len < 17)  return -1;  // 17为cancel消息的固定长度
	
	memset(buffer,0,17);
	buffer[3] = 13;
	buffer[4] = 8;
	int_to_char(index,c);
	for(i = 0; i < 4; i++)  buffer[i+5]  = c[i];
	int_to_char(begin,c);
	for(i = 0; i < 4; i++)  buffer[i+9]  = c[i];
	int_to_char(length,c);
	for(i = 0; i < 4; i++)  buffer[i+13] = c[i];

	peer->msg_len += 17;	
	return 0;
}

int create_port_msg(int port,Peer *peer)
{
	unsigned char  c[4];
	unsigned char  *buffer = peer->out_msg + peer->msg_len;
	int            len = MSG_SIZE - peer->msg_len;

	if( len < 7)  return 0;  // 7为port消息的固定长度

	memset(buffer,0,7);
	buffer[3] = 3;
	buffer[4] = 9;
	int_to_char(port,c);
	buffer[5] = c[2];
	buffer[6] = c[3];

	peer->msg_len += 7;
	return 0;
}

// 以十六进制的形式打印消息的内容,用于调试
int print_msg_buffer(unsigned char *buffer, int len)
{
	int i;

	for(i = 0; i < len; i++) {
		printf("%.2x ",buffer[i]);
		if( (i+1) % 16 == 0 )  printf("\n");
	}
	printf("\n");

	return 0;
}

// 判断缓冲区中是否存放了一条完整的消息
int is_complete_message(unsigned char *buff,unsigned int len,int *ok_len)
{
	unsigned int   i;
	char           btkeyword[20];

	unsigned char  keep_alive[4]   = { 0x0, 0x0, 0x0, 0x0 };
	unsigned char  chocke[5]       = { 0x0, 0x0, 0x0, 0x1, 0x0};
	unsigned char  unchocke[5]     = { 0x0, 0x0, 0x0, 0x1, 0x1};
	unsigned char  interested[5]   = { 0x0, 0x0, 0x0, 0x1, 0x2};
	unsigned char  uninterested[5] = { 0x0, 0x0, 0x0, 0x1, 0x3};
	unsigned char  have[5]         = { 0x0, 0x0, 0x0, 0x5, 0x4};
	unsigned char  request[5]      = { 0x0, 0x0, 0x0, 0xd, 0x6};
	unsigned char  cancel[5]       = { 0x0, 0x0, 0x0, 0xd, 0x8};
	unsigned char  port[5]         = { 0x0, 0x0, 0x0, 0x3, 0x9};
	
	if(buff==NULL || len<=0 || ok_len==NULL)  return -1;
	*ok_len = 0;
	
	btkeyword[0] = 19;
	memcpy(&btkeyword[1],"BitTorrent protocol",19);  // BitTorrent协议关键字

	unsigned char  c[4];
	unsigned int   length;
	
	for(i = 0; i < len; ) {
		// 握手、chocke、have等消息的长度是固定的
		if( i+68<=len && memcmp(&buff[i],btkeyword,20)==0 )         i += 68;
		else if( i+4 <=len && memcmp(&buff[i],keep_alive,4)==0 )    i += 4;
		else if( i+5 <=len && memcmp(&buff[i],chocke,5)==0 )        i += 5;
		else if( i+5 <=len && memcmp(&buff[i],unchocke,5)==0 )      i += 5;
		else if( i+5 <=len && memcmp(&buff[i],interested,5)==0 )    i += 5;
		else if( i+5 <=len && memcmp(&buff[i],uninterested,5)==0 )  i += 5;
		else if( i+9 <=len && memcmp(&buff[i],have,5)==0 )          i += 9;
		else if( i+17<=len && memcmp(&buff[i],request,5)==0 )       i += 17;
		else if( i+17<=len && memcmp(&buff[i],cancel,5)==0 )        i += 17;
		else if( i+7 <=len && memcmp(&buff[i],port,5)==0 )          i += 7;
		// bitfield消息的长度是变化的
		else if( i+5 <=len && buff[i+4]==5 )  {
			c[0] = buff[i];   c[1] = buff[i+1];
			c[2] = buff[i+2]; c[3] = buff[i+3];
			length = char_to_int(c);	
			// 消息长度占4字节,消息本身占length个字节
			if( i+4+length <= len )  i += 4+length;
			else { *ok_len = i; return -1; }
		}
		// piece消息的长度也是变化的
		else if( i+5 <=len && buff[i+4]==7 )  {
			c[0] = buff[i];   c[1] = buff[i+1];
			c[2] = buff[i+2]; c[3] = buff[i+3];
			length = char_to_int(c);
			// 消息长度占4字节,消息本身占length个字节
			if( i+4+length <= len )  i += 4+length;
			else { *ok_len = i; return -1; }
		}
		else {
			// 处理未知类型的消息
			if(i+4 <= len) {
				c[0] = buff[i];   c[1] = buff[i+1];
				c[2] = buff[i+2]; c[3] = buff[i+3];
				length = char_to_int(c);
				// 消息长度占4字节,消息本身占length个字节
				if(i+4+length <= len)  { i += 4+length; continue; }
				else { *ok_len = i; return -1; }
			}
			// 如果也不是未知消息类型,则认为目前接收的数据还不是一个完整的消息
			*ok_len = i;
			return -1;
		}
	}
	
	*ok_len = i;
	return 1;
}

int process_handshake_msg(Peer *peer,unsigned char *buff,int len)
{
	if(peer==NULL || buff==NULL)  return -1;

	if(memcmp(info_hash,buff+28,20) != 0) { 
		peer->state = CLOSING;
		// 丢弃发送缓冲区中的数据
		discard_send_buffer(peer);
		clear_btcache_before_peer_close(peer);
		close(peer->socket);
		return -1;
	}
	
	memcpy(peer->id,buff+48,20);
	(peer->id)[20] = '\0';
	
	if(peer->state == INITIAL) {
		peer->state = HANDSHAKED;
		create_handshake_msg(info_hash,peer_id,peer);
	}
	if(peer->state == HALFSHAKED)  peer->state = HANDSHAKED;

	peer->start_timestamp = time(NULL);
	return 0;
}

int process_keep_alive_msg(Peer *peer,unsigned char *buff,int len)
{
	if(peer==NULL || buff==NULL)  return -1;

	peer->start_timestamp = time(NULL);
	return 0;
}

int process_choke_msg(Peer *peer,unsigned char *buff,int len)
{
	if(peer==NULL || buff==NULL)  return -1;

	if( peer->state!=CLOSING && peer->peer_choking==0 ) {
		peer->peer_choking = 1;
		peer->last_down_timestamp = 0;
		peer->down_count          = 0;
		peer->down_rate           = 0;
	}

	peer->start_timestamp = time(NULL);
	return 0;
}

int process_unchoke_msg(Peer *peer,unsigned char *buff,int len)
{
	if(peer==NULL || buff==NULL)  return -1;

	if( peer->state!=CLOSING && peer->peer_choking==1 ) {
		peer->peer_choking = 0;
		if(peer->am_interested == 1)  create_req_slice_msg(peer);
		else {
			peer->am_interested = is_interested(&(peer->bitmap), bitmap);
			if(peer->am_interested == 1) create_req_slice_msg(peer);
			else printf("Received unchoke but Not interested to IP:%s \n",peer->ip);
		}

		peer->last_down_timestamp = 0;
		peer->down_count          = 0;
		peer->down_rate           = 0;
	}

	peer->start_timestamp = time(NULL);
	return 0;
}

int process_interested_msg(Peer *peer,unsigned char *buff,int len)
{
	if(peer==NULL || buff==NULL)  return -1;

	if( peer->state!=CLOSING && peer->state==DATA ) {
		peer->peer_interested = is_interested(bitmap, &(peer->bitmap));
		if(peer->peer_interested == 0)  return -1;
		if(peer->am_choking == 0) create_chock_interested_msg(1,peer);
	}

	peer->start_timestamp = time(NULL);
	return 0;
}

int process_uninterested_msg(Peer *peer,unsigned char *buff,int len)
{
	if(peer==NULL || buff==NULL)  return -1;

	if( peer->state!=CLOSING && peer->state==DATA ) {
		peer->peer_interested = 0;
		cancel_requested_list(peer);
	}

	peer->start_timestamp = time(NULL);
	return 0;
}

int process_have_msg(Peer *peer,unsigned char *buff,int len)
{
	int           rand_num;
	unsigned char c[4];

	if(peer==NULL || buff==NULL)  return -1;