消息处理模块
消息处理模块由message.h和message.c组成，负责根据当前的状态生成并发送消息，接收以及处理消息。
以下是message.h的代码：
//message.h
#ifndef MESSAGE_H
#define MESSAGE_H
#include "peer.h"
int int_to_char(int i, unsigned char c[4]); // 将整型变量i的四个字节存放到数组c中
int char_to_int(unsigned char c[4]); // 将数组c中的四个字节转换为一个整型数
// 以下函数创建各个类型的消息，创建消息的函数参照BT协议
int create_handshake_msg(char *info_hash,char *peer_id,Peer *peer);
int create_keep_alive_msg(Peer *peer);
int create_chock_interested_msg(int type,Peer *peer);
int create_have_msg(int index,Peer *peer);
int create_bitfield_msg(char *bitfield,int bitfield_len,Peer *peer);
int create_request_msg(int index,int begin,int length,Peer *peer);
int create_piece_msg(int index,int begin,char *block,int b_len,Peer *peer);
int create_cancel_msg(int index,int begin,int length,Peer *peer);
int create_port_msg(int port,Peer *peer);
// 打印消息缓冲区中的消息, 用于调试
int print_msg_buffer(unsigned char *buffer, int len);
// 为发送have消息作准备,have消息较为特殊,它要发送给所有peer
int prepare_send_have_msg();
// 判断缓冲区中是否存放了一个完整的消息
int is_complete_message(unsigned char *buff,unsigned int len,int *ok_len);
// 处理收到的消息,接收缓冲区中存放着一个完整的消息
int parse_response(Peer *peer);
// 处理受到的消息,接收缓冲区中除了存放一个完整的消息外,还有不完整的消息
int parse_response_uncomplete_msg(Peer *p,int ok_len);
// 创建响应消息
int create_response_message(Peer *peer);
// 即将与peer断开时,丢弃发送缓冲区中的消息
void discard_send_buffer(Peer *peer);
#endifmessage.c的文件的头部包含的代码如下：
#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 //握手消息
#define KEEP_ALIVE -1 //keep_alive消息
#define CHOKE 0 //chock消息
#define UNCHOKE 1 //uchock消息
#define INTERESTED 2 //interested消息
#define UNINTERESTED 3 //uninterested消息
#define HAVE 4 //have消息
#define BITFIELD 5 //bitfield消息
#define REQUEST 6 //request消息
#define PIECE 7 //piece消息
#define CANCEL 8 //cancel消息
#define PORT 9 //port消息
// 如果45秒未给某peer发送消息，则发送keep_alive消息
#define KEEP_ALIVE_TIME 45
extern Bitmap *bitmap; // 在bitmap.c中定义，指向己方的位图
extern char info_hash[20]; // 在parse_metafile.c中定义，存放info_hash
extern char peer_id[20]; // 在parse_metafile.c中定义，存放peer_id
extern int have_piece_index[64]; // 在data.c中定义，存放下载到的piece的index
extern Peer *peer_head; // 在peer.c中定义，指向peer链表message.c中的函数代码如下：
int int_to_char(int i, unsigned char c[4])
将int型的i保存到字符数组c[4]中。
/*
*功能:将int型的各个字节放到char型数组里
*传入参数：i的各个字节，
*传出参数：字符数组c
*返回值：
* 0 保存成功
*/
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])
功能刚好和上面的函数相反。
/*
*功能:将char型数组放到int型中
*传入参数：字符数组c
*传出参数：
*返回值：
* i 转换结果
*/
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, char *peer_id, Peer *peer)
/*
*功能：创建握手消息
*传入参数：
* info_hash在parse_metafile.c中由种子文件计算而得
* peer_id也在parse_metafile.c中生成
* peer为要发送握手消息给某一个peer的指针变量
* 返回：
* 创建消息成功返回0,创建失败返回-1
*/
int create_handshake_msg(char *info_hash,char *peer_id,Peer *peer)
{
int i;
unsigned char keyword[20] = "BitTorrent protocol", c = 0x00;
//发送缓存区大小16K(slice)+2K(其他消息)
//跳过slice在缓冲区后追加其他消息
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)
/*
*功能:创建keep_alive消息
*传入参数：Peer
*传出参数：
*返回值：
* 1 成功
*/
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)
创建chock消息。
/*
*功能:创建chock消息
*传入参数：type peer
*传出参数：
*返回值：
* 0 保存成功
*/
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;
}程序说明：chock消息的type值为0，unchoke消息1，interested消息为2，uninterested消息为3。
int create_have_msg(int index, Peer *peer)
/*
*功能:创建have消息
*传入参数：index peer
*传出参数：
*返回值：
* 0 创建成功
*/
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); // index为piece的下标
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)
/*
*功能:创建bitfield消息
*传入参数：bitfield bifield_len Peer
*传出参数：
*返回值：
* 0 创建成功
*/
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);
//组装位图消息
for(i = 0; i < 4; i++)
buffer[i] = c[i];
buffer[4] = 5;
创建bitfield消息
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)
/*
*功能：创建数据请求消息
*传入参数：
index为请求的piece的下标
begin为piece内的偏移量
length为请求数据的长度
*返回：0 创建成功
*/
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)
/*
*功能：创建piece消息
*传入参数：
block指向待发送的数据
b_len为block所指向的数据的长度
*返回： 0 创建成功
* -1 创建失败
*/
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,Peer *peer)
/*
*功能:创建cancel消息
*传入参数：index bdegin length peer
*传出参数：
*返回值：
* 0 创建成功
*/
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)
/*
*功能:创建Port消息
*传入参数： port peer
*传出参数：
*返回值：
* 0 创建成功
*/
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;
}int is_complete_message(unsigned char *buff, unsigned int len, int *ok_len)
/*
*功能:判断缓冲区中是否存放了一条完整的消息
*传入参数：buff len ok_len
*传出参数：
*返回值：
* 1 是
* -1 否
*/
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 print_mdg_buffer(unsigned char *buffer, int len)
/*
*功能:以十六进制的形式打印消息的内容,用于调试
*传入参数：buffer len
*传出参数：
*返回值：
* 0 创建成功
*/
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;
}处理的消息程序如下：
/*
*功能:处理接收到的一条握手消息
*传入参数：
从peer接收到这条握手消息
buff指向握手消息
len为buff的长度
*传出参数：
*返回值：
* 0
*/
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;//表明处于即将与Peer断开状态
// 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;
}
//获得Peer的ID
memcpy(peer->id,buff+48,20);
(peer->id)[20] = '\0';
// 若当前处于Initial状态，则发送握手消息给peer
if(peer->state == INITIAL)
{
peer->state = HANDSHAKED;//表明处于全握手状态
create_handshake_msg(info_hash,peer_id,peer);
}
// 若握手消息已发送，则状态转换为已握手状态
if(peer->state == HALFSHAKED)
peer->state = HANDSHAKED;
// 记录最近收到该peer消息的时间
// 若一定时间内(如两分钟)未收到来自该peer的任何消息，则关闭连接
peer->start_timestamp = time(NULL);
return 0;
}
/*
*功能:处理刚刚接收到的来自peer的keepv_alive消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
*/
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;
}
/*
*功能:处理收到的choke消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
* -1 没有
*/
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;//被Peer阻塞
peer->last_down_timestamp = 0;//最近下载数据开始时间
peer->down_count = 0;//下载的字节数
peer->down_rate = 0;//下载速度
}
peer->start_timestamp = time(NULL);//最近一次接收Peer消息的时间
return 0;
}
/*
*功能:处理unchoke消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
*/
int process_unchoke_msg(Peer *peer,unsigned char *buff,int len)
{
if(peer==NULL || buff==NULL) return -1;
// 若原来处于choke状态且与该peer的连接未被关闭
if( peer->state!=CLOSING && peer->peer_choking==1 )
{
peer->peer_choking = 0;//Peer解除对客服端的阻塞
//客服端对Peer感兴趣，则构造request消息请求peer发送数据
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);//最近一次接收Peer消息的时间
return 0;
}
/*
*功能:处理收到的interested消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
*/
int process_interested_msg(Peer *peer,unsigned char *buff,int len)
{
if(peer==NULL || buff==NULL) return -1;
//客户端与peer的连接未被关闭且交换数据状态
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);//创建非阻塞消息
}
peer->start_timestamp = time(NULL);
return 0;
}
/*
*功能:处理收到的uninterested消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
* -1 出错
*/
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;//Peer对客服端不感兴趣
cancel_requested_list(peer);//撤销请求队列
}
peer->start_timestamp = time(NULL);
return 0;
}
/*
*功能:处理have消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
*/
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;
srand(time(NULL));
rand_num = rand() % 3;
if( peer->state!=CLOSING && peer->state==DATA )
{
c[0] = buff[5];
c[1] = buff[6];
c[2] = buff[7];
c[3] = buff[8];
if(peer->bitmap.bitfield != NULL)
set_bit_value(&(peer->bitmap),char_to_int(c),1);//更新位图
if(peer->am_interested == 0)
{
peer->am_interested = is_interested(&(peer->bitmap), bitmap);
// 由原来的对peer不感兴趣变为感兴趣时,发interested消息
if(peer->am_interested == 1)
create_chock_interested_msg(2,peer);
}
else
{ // 收到三个have则发一个interested消息
if(rand_num == 0)
create_chock_interested_msg(2,peer);
}
}
peer->start_timestamp = time(NULL);
return 0;
}
/*
*功能:处理cancel消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
* -1 出错
*/
int process_cancel_msg(Peer *peer,unsigned char *buff,int len)
{
unsigned char c[4];
int index, begin, length;
if(peer==NULL || buff==NULL)
return -1;
c[0] = buff[5];
c[1] = buff[6];
c[2] = buff[7];
c[3] = buff[8];
index = char_to_int(c);//获得index
c[0] = buff[9];
c[1] = buff[10];
c[2] = buff[11];
c[3] = buff[12];
begin = char_to_int(c);//获得begin
c[0] = buff[13];
c[1] = buff[14];
c[2] = buff[15];
c[3] = buff[16];
length = char_to_int(c);//获得Length
// 在被请求队列中删除指定的请求
Request_piece *p, *q;
p = q = peer->Requested_piece_head;//取得Peer请求队列头指针
while(p != NULL)
{
if( p->index==index && p->begin==begin && p->length==length )
{
if(p == peer->Requested_piece_head)
peer->Requested_piece_head = p->next;
else
q->next = p->next;
free(p);
break;
}
q = p;
p = p->next;
}
peer->start_timestamp = time(NULL);
return 0;
}
/*
*功能:处理收到的位图消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
* -1 出错
*/
int process_bitfield_msg(Peer *peer,unsigned char *buff,int len)
{
unsigned char c[4];
if(peer==NULL || buff==NULL) return -1;
//握手和已发送位图状态
if(peer->state==HANDSHAKED || peer->state==SENDBITFIELD)
{
c[0] = buff[0];
c[1] = buff[1];
c[2] = buff[2];
c[3] = buff[3];
// 若原先已收到一个位图消息，则清空原来的位图
if( peer->bitmap.bitfield != NULL )
{
free(peer->bitmap.bitfield);
peer->bitmap.bitfield = NULL;
}
peer->bitmap.valid_length = bitmap->valid_length;
// 若收到的一个错误位图
if(bitmap->bitfield_length != char_to_int(c)-1)
{
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;
}
// 生成该peer的位图
peer->bitmap.bitfield_length = char_to_int(c) - 1;
peer->bitmap.bitfield = (unsigned char *)malloc(peer->bitmap.bitfield_length);
memcpy(peer->bitmap.bitfield,&buff[5],peer->bitmap.bitfield_length);
// 如果原状态为已握手,收到位图后应该向peer发位图
if(peer->state == HANDSHAKED)
{
create_bitfield_msg(bitmap->bitfield,bitmap->bitfield_length,peer);
peer->state = DATA;
}
// 如果原状态为已发送位图，收到位图后可以准备交换数据
if(peer->state == SENDBITFIELD)
{
peer->state = DATA;
}
// 判断peer是否对我们感兴趣
peer->peer_interested = is_interested(bitmap,&(peer->bitmap));
// 判断对peer是否感兴趣,若是则发送interested消息
peer->am_interested = is_interested(&(peer->bitmap), bitmap);
if(peer->am_interested == 1)
create_chock_interested_msg(2,peer);
}
peer->start_timestamp = time(NULL);
return 0;
}
/*
*功能：处理收到的request消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
* -1 出错
*/
int process_request_msg(Peer *peer,unsigned char *buff,int len)
{
unsigned char c[4];
int index, begin, length;
Request_piece *request_piece, *p;
if(peer==NULL || buff==NULL) return -1;
if(peer->am_choking==0 && peer->peer_interested==1)
{
c[0] = buff[5]; c[1] = buff[6];
c[2] = buff[7]; c[3] = buff[8];
index = char_to_int(c);
c[0] = buff[9]; c[1] = buff[10];
c[2] = buff[11]; c[3] = buff[12];
begin = char_to_int(c);
c[0] = buff[13]; c[1] = buff[14];
c[2] = buff[15]; c[3] = buff[16];
length = char_to_int(c);
// 错误的slice请求
if( begin%(16*1024) != 0 )
{
return 0;
}
// 查看该请求是否已存在,若已存在,则不进行处理
p = peer->Requested_piece_head;
while(p != NULL)
{
if(p->index==index && p->begin==begin && p->length==length)
{
break;
}
p = p->next;
}
if(p != NULL) //请求存在
return 0;
// 将请求加入到请求队列中
request_piece = (Request_piece *)malloc(sizeof(Request_piece));
if(request_piece == NULL)
{
printf("%s:%d error",__FILE__,__LINE__);
return 0;
}
request_piece->index = index;
request_piece->begin = begin;
request_piece->length = length;
request_piece->next = NULL;
if( peer->Requested_piece_head == NULL )
peer->Requested_piece_head = request_piece;
else
{
p = peer->Requested_piece_head;
while(p->next != NULL)
p = p->next;
p->next = request_piece;
}
//printf("*** add a request FROM IP:%s index:%-6d begin:%-6x ***\n",
// peer->ip,index,begin);
}
peer->start_timestamp = time(NULL);
return 0;
}
/*
*功能：处理收到的piece消息
*传入参数：peer buff len
*传出参数：
*返回值：
* 0 处理成功
* -1 出错
*/
int process_piece_msg(Peer *peer,unsigned char *buff,int len)
{
unsigned char c[4];
int index, begin, length;
Request_piece *p;
if(peer==NULL || buff==NULL)
return -1;
if(peer->peer_choking==0)
{
c[0] = buff[0]; c[1] = buff[1];
c[2] = buff[2]; c[3] = buff[3];
length = char_to_int(c) - 9;
c[0] = buff[5]; c[1] = buff[6];
c[2] = buff[7]; c[3] = buff[8];
index = char_to_int(c);
c[0] = buff[9]; c[1] = buff[10];
c[2] = buff[11]; c[3] = buff[12];
begin = char_to_int(c);
//查看请求是否存在
p = peer->Request_piece_head;
while(p != NULL)
{
if(p->index==index && p->begin==begin && p->length==length)
break;
p = p->next;
}
if(p == NULL)
{
printf("did not found matched request\n");
return -1;
}
if(peer->last_down_timestamp == 0)
peer->last_down_timestamp = time(NULL);
peer->down_count += length;
peer->down_total += length;
//将slice写入缓存区
write_slice_to_btcache(index,begin,length,buff+13,length,peer);
create_req_slice_msg(peer);
}
peer->start_timestamp = time(NULL);
return 0;
}
/*
*功能:处理收到的消息（peer的接收缓冲区中可能存放着多条消息）
*传入参数：peer
*传出参数：
*返回值：
* 0 处理成功
* -1 出错
*/
int parse_response(Peer *peer)
{
unsigned char btkeyword[20];
unsigned char keep_alive[4] = { 0x0, 0x0, 0x0, 0x0 };
int index;
unsigned char *buff = peer->in_buff;//获取接收到的消息
int len = peer->buff_len;//缓冲区的长度
if(buff==NULL || peer==NULL)
return -1;
btkeyword[0] = 19;
memcpy(&btkeyword[1],"BitTorrent protocol",19); // BitTorrent协议关键字
// 分别处理12种消息
for(index = 0; index < len; )
{
if( (len-index >= 68) && (memcmp(&buff[index],btkeyword,20) == 0) )
{
process_handshake_msg(peer,buff+index,68);
index += 68;
}
else if( (len-index >= 4) && (memcmp(&buff[index],keep_alive,4) == 0))
{
process_keep_alive_msg(peer,buff+index,4);
index += 4;
}
else if( (len-index >= 5) && (buff[index+4] == CHOKE) )
{
process_choke_msg(peer,buff+index,5);
index += 5;
}
else if( (len-index >= 5) && (buff[index+4] == UNCHOKE) )
{
process_unchoke_msg(peer,buff+index,5);
index += 5;
}
else if( (len-index >= 5) && (buff[index+4] == INTERESTED) )
{
process_interested_msg(peer,buff+index,5);
index += 5;
}
else if( (len-index >= 5) && (buff[index+4] == UNINTERESTED) )
{
process_uninterested_msg(peer,buff+index,5);
index += 5;
}
else if( (len-index >= 9) && (buff[index+4] == HAVE) )
{
process_have_msg(peer,buff+index,9);
index += 9;
}
else if( (len-index >= 5) && (buff[index+4] == BITFIELD) )
{
process_bitfield_msg(peer,buff+index,peer->bitmap.bitfield_length+5);
index += peer->bitmap.bitfield_length + 5;
}
else if( (len-index >= 17) && (buff[index+4] == REQUEST) )
{
process_request_msg(peer,buff+index,17);
index += 17;
}
else if( (len-index >= 13) && (buff[index+4] == PIECE) )
{
unsigned char c[4];
int length;
c[0] = buff[index]; c[1] = buff[index+1];
c[2] = buff[index+2]; c[3] = buff[index+3];
length = char_to_int(c) - 9;
process_piece_msg(peer,buff+index,length+13);
index += length + 13; // length+13为piece消息的长度
}
else if( (len-index >= 17) && (buff[index+4] == CANCEL) )
{
process_cancel_msg(peer,buff+index,17);
index += 17;
}
else if( (len-index >= 7) && (buff[index+4] == PORT) )
{
index += 7;
}
else
{
// 如果是未知的消息类型,则跳过不予处理
unsigned char c[4];
int length;
if(index+4 <= len)
{
c[0] = buff[index]; c[1] = buff[index+1];
c[2] = buff[index+2]; c[3] = buff[index+3];
length = char_to_int(c);
if(index+4+length <= len)
{
index += 4+length;
continue;
}
}
// 如果是一条错误的消息,清空接收缓冲区
peer->buff_len = 0;
return -1;
}
} // end for
// 接收缓冲区中的消息处理完毕后,清空接收缓冲区
peer->buff_len = 0;
return 0;
}
/*
*功能:处理收到的不完整的消息
*传入参数：
ok_len为接收缓冲区中完整消息的长度
*传出参数：
*返回值：
* 0 处理成功
* -1 出错
*/
int parse_response_uncomplete_msg(Peer *p,int ok_len)
{
char *tmp_buff;
int tmp_buff_len;
// 分配存储空间,并保存接收缓冲区中不完整的消息
tmp_buff_len = p->buff_len - ok_len;
if(tmp_buff_len <= 0)
return -1;
tmp_buff = (char *)malloc(tmp_buff_len);
if(tmp_buff == NULL)
{
printf("%s:%d error\n",__FILE__,__LINE__);
return -1;
}
memcpy(tmp_buff,p->in_buff+ok_len,tmp_buff_len);
// 处理接收缓冲区中前面完整的消息
p->buff_len = ok_len;
parse_response(p);
// 将不完整的消息拷贝到接收缓冲区的开始处
memcpy(p->in_buff,tmp_buff,tmp_buff_len);
p->buff_len = tmp_buff_len;
if(tmp_buff != NULL)
free(tmp_buff);
return 0;
}
int prepare_send_have_msg()
/*
*功能:当下载完一个piece时,应该向所有的peer发送have消息
*传入参数：
*传出参数：
*返回值：
* 0 处理成功
* -1 出错
*/
int prepare_send_have_msg()
{
Peer *p = peer_head;//获得当前与客服端通信的Peer链表头指针
int i;
if(peer_head == NULL)
return -1;
if(have_piece_index[0] == -1)
return -1;
while(p != NULL)
{
for(i = 0; i < 64; i++)
{
if(have_piece_index[i] != -1)
{
create_have_msg(have_piece_index[i],p);
}
else
{
break;
}
}
p = p->next;
}
for(i = 0; i < 64; i++)
{
if(have_piece_index[i] == -1)
{
break;
}
else
{
have_piece_index[i] = -1;
}
}
return 0;
}int create_response_message(Peer *peer)
/*
*功能:主动创建发送给peer的消息,而不是等收到某个消息再作出响应
*传入参数：peer
*传出参数：
*返回值：
* 0 处理成功
*/
int create_response_message(Peer *peer)
{
if(peer==NULL) return -1;
if(peer->state == INITIAL)
{
//创建握手消息
create_handshake_msg(info_hash,peer_id,peer);
peer->state = HALFSHAKED;
return 0;
}
if(peer->state == HANDSHAKED)
{
if(bitmap == NULL)
return -1;
//创建位图消息
create_bitfield_msg(bitmap->bitfield,bitmap->bitfield_length,peer);
peer->state = SENDBITFIELD;
return 0;
}
// 发送piece消息,即发送下载文件的内容
if( peer->am_choking==0 && peer->Requested_piece_head!=NULL )
{
Request_piece *req_p = peer->Requested_piece_head;
//从缓存区获取slice消息
int ret = read_slice_for_send(req_p->index,req_p->begin,req_p->length,peer);
if(ret < 0 )
{
printf("read_slice_for_send ERROR\n");
}
else
{
//更新Peer结构体中的信息
if(peer->last_up_timestamp == 0)
peer->last_up_timestamp = time(NULL);
peer->up_count += req_p->length;
peer->up_total += req_p->length;
peer->Requested_piece_head = req_p->next;
//printf("********* sending a slice TO:%s index:%-5d begin:%-5x *********\n",
//peer->ip,req_p->index,req_p->begin);
free(req_p);
return 0;
}
}
// 如果3分钟没有收到任何消息关闭连接
time_t now = time(NULL); // 获取当前时间
long interval1 = now - peer->start_timestamp;
if( interval1 > 180 )
{
peer->state = CLOSING;
discard_send_buffer(peer); // 丢弃发送缓冲区中的数据
clear_btcache_before_peer_close(peer);
close(peer->socket);
}
// 如果45秒没有发送和接收消息,则发送一个keep_alive消息
long interval2 = now - peer->recet_timestamp;
if( interval1>45 && interval2>45 && peer->msg_len==0)
create_keep_alive_msg(peer);
return 0;
}void discard_send_buffer(Peer *peer)
/*
*功能:即将与peer断开时,丢弃发送缓冲区中的消息
*传入参数：peer
*传出参数：
*返回值：
*/
void discard_send_buffer(Peer *peer)
{
struct linger lin;
int lin_len;
lin.l_onoff = 1;
lin.l_linger = 0;
lin_len = sizeof(lin);
if(peer->socket > 0)
{
setsockopt(peer->socket,SOL_SOCKET,SO_LINGER,(char *)&lin,lin_len);
}
}
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