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8-3-http-analyze.c
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8-3-http-analyze.c
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#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <assert.h>
#define BUFFER_SIZE 4096 /*读缓冲区的大小*/
/*主状态机的两种可能状态,分别表示:当前正在分析请求行,当前正在分析头部字段
* */
enum CHECK_STATE { CHECK_STATE_REQUESTLINE = 0, CHECK_STATE_HEADER };
/*从状态机的三种可能状态,即行的读取状态, 分别表示:读取到一个完整的行,
* 行出错和行数据尚且不完整*/
enum LINE_STATUS { LINE_OK = 0, LINE_BAD, LINE_OPEN };
/* 服务器处理HTTP请求的结果,
* NO_REQUEST表示请求不完整,需要继续读取客户数据;GET_REQUEST表示获得了一个完整的客户请求;
* BAD_REQUEST表示客户请求有语法错误;
* FORBIDDEN_REQUSET表示客户对资源没有足够的访问权限;
* INTERNAL_ERROR表示服务器内部错误;
* CLOSED_CONNECTION表示客户端已经关闭连接了.*
*/
enum HTTP_CODE { NO_REQUEST, GET_REQUEST, BAD_REQUEST,
FORRBIDEN_REQUEST, INTERNAL_ERROR, CLOSED_CONNECTION };
/*为简化问题,
* 我们没有给客户端发送一个完整的HTTP应答报文,而只是根据服务器的处理结果发送如下发成功或失败信息
*/
static const char* szret[] = {"I get a correct result\n", "Something wrong\n" };
/*从状态机,用于解析出一行内容 */
LINE_STATUS parse_line(char *buffer, int &checked_index, int &read_index)
{
char temp;
/*checked_index指向buffer(应用程序的读缓冲区)中当前正在分析的字节,
* read_index指向buffer中客户数据的为尾部的下一字节。
* buffer中第0~check_index字节都已经分析完毕,第checked_index~(read_index
* -1)字节又下面的循环挨个分析 */
for(; checked_index < read_index; ++checked_index)
{
/*获得当前要分析的字节 */
temp = buffer[checked_index];
/*如果当前的字节是"\r",即回车符, 则说明可能读到一个完整的行 */
if (temp == '\r')
{
/*如果“\r”字符碰巧是目前buffer中的最后一个已经被读入的客户数据,那么这次分析没有读取到一个完整的行,
* 返回LINE_OPEN以表示还需要继续读取客户数据才能进一步分析 *
*/
if ((checked_index + 1) == read_index )
{
return LINE_OPEN;
}
/*如果下一个字符是"\n", 则说明我们成功读取到一个完整的行 */
else if (buffer[checked_index + 1] == '\n')
{
buffer[checked_index ++] = '\0';
buffer[checked_index ++] = '\0';
return LINE_OK;
}
/*否则的话, 说明客户发送的HTTP请求存在语法问题*/
return LINE_BAD;
}
/*如果当前字节是“\n”,即换行符,则也说明可能读取到一个完整的行 */
else if (temp == '\n')
{
if ((checked_index > 1) && buffer[checked_index - 1] == '\r')
{
buffer[checked_index - 1] = '\0';
buffer[checked_index ++ ] = '\0';
return LINE_OK;
}
return LINE_BAD;
}
}
/* 如果所有内容都分析完毕也没有遇到"\r"字符,则返回LINE_OPEN,
* 表示还需要继续读取客户数据才能近一步分析
*/
return LINE_OPEN;
}
/*分析请求行*/
HTTP_CODE parse_requestline(char *temp, CHECK_STATE &checkstate)
{
char *url = strpbrk(temp, " \t");
/*如果请求行中没有空白字符或“\t”字符,则HTTP请求必有问题 */
if (!url)
{
return BAD_REQUEST;
}
*url ++ = '\0';
char *method = temp;
if (strcasecmp(method, "GET") == 0) /*仅支持GET方法*/
{
fprintf(stdout, "The request method is GET\n");
}
else
{
return BAD_REQUEST;
}
url += strspn(url, " \t");
char *version = strpbrk(url, " \t");
if (!version)
{
return BAD_REQUEST;
}
/*仅支持HTTP/1.1 */
if (strcasecmp(version, "HTTP/1.1") != 0)
{
return BAD_REQUEST;
}
/*检查URL是否合法 */
if (strncasecmp(url, "http:https://", 7)== 0)
{
url += 7;
url = strchr(url, '/');
}
if (!url || url[0] != '/')
{
return BAD_REQUEST;
}
fprintf(stdout, "The request URL is: %s\n", url);
/*HTTP 请求行处理完毕, 状态转移到头部字段分析 */
checkstate = CHECK_STATE_HEADER;
return NO_REQUEST;
}
/*分析头部字段 */
HTTP_CODE parse_headers(char *temp)
{
/*遇到一个空行,说明我们得到一个正确的HTTP请求 */
if (temp[0] == '\0')
{
return GET_REQUEST;
}
else if (strncasecmp(temp, "Host:", 5) == 0) /*处理”HOST“头部字段 */
{
temp += 5;
temp += strspn(temp, " \t");
fprintf(stdout, "the request host is: %s\n", temp);
}
else /*其他头部字段都不处理 */
{
fprintf(stdout, "I can not handle this header\n");
}
return NO_REQUEST;
}
/*分析HTTP请求的入口函数 */
HTTP_CODE parse_content(char *buffer, int &checked_index, CHECK_STATE &checkstate,
int &read_index, int &start_line)
{
LINE_STATUS linestatus = LINE_OK; /*记录当前行的读取状态 */
HTTP_CODE retcode = NO_REQUEST; /*记录HTTP请求的处理结果 */
/*主状态机, 用于从buffer中取出所有完整的行 */
while((linestatus = parse_line(buffer, checked_index, read_index)) == LINE_OK)
{
char *temp = buffer + start_line; /*start_line 是行在buffer中的起始位置*/
start_line = checked_index; /*记录下一行的起始位置*/
/*checkstatus 记录主机状态当前的状态 */
switch(checkstate)
{
case CHECK_STATE_REQUESTLINE:
{
retcode = parse_requestline(temp, checkstate);
if (retcode == BAD_REQUEST)
{
return BAD_REQUEST;
}
break;
}
case CHECK_STATE_HEADER:
{
retcode = parse_headers(temp);
if (retcode == BAD_REQUEST)
{
return BAD_REQUEST;
}
else if (retcode == GET_REQUEST)
{
return GET_REQUEST;
}
break;
}
default:
{
return INTERNAL_ERROR;
}
}
}
/*若没有读取到一个完整的行, 则表示还需要继续读取客户数据才能进一步分析 */
if (linestatus == LINE_OPEN)
{
return NO_REQUEST;
}
else
{
return BAD_REQUEST;
}
}
int main(int argc, const char *argv[])
{
if (argc <= 2)
{
fprintf(stdout, "usage: %s ip_address port_number\n", basename(argv[0]));
return 1;
}
const char *ip = argv[1];
int port = atoi(argv[2]);
struct sockaddr_in address;
bzero(&address, sizeof(address));
address.sin_family = AF_INET;
inet_pton(AF_INET, ip, &address.sin_addr);
address.sin_port = htons(port);
int listenfd = socket(PF_INET, SOCK_STREAM, 0);
assert(listenfd >= 0);
int ret = bind(listenfd, (struct sockaddr *)&address, sizeof(address));
assert(ret != -1);
ret = listen(listenfd, 5);
assert(ret != -1);
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);
int fd = accept(listenfd, (struct sockaddr *)&client_address, &client_addrlength);
if (fd < 0)
{
fprintf(stderr, "accept error! errno:%d, errstr:%s\n", errno, strerror(errno));
}
else
{
char buffer[BUFFER_SIZE]; /* reading buffer */
memset(buffer, '\0', BUFFER_SIZE);
int data_read = 0;
int read_index = 0;
int checked_index= 0; /*how many bytes data have read from request,currently*/
int start_line = 0; /*the start postion of row in buffer */
/*set the main state machine's initial state */
CHECK_STATE checkstate = CHECK_STATE_REQUESTLINE;
while(1)
{
data_read = recv(fd, buffer + read_index, BUFFER_SIZE - read_index, 0);
if(data_read == -1)
{
fprintf(stderr, "read falied, sockfd:%d\n", fd);
break;
}
else if (data_read == 0)
{
fprintf(stdout, "remote client has closed the connection\n");
break;
}
read_index += data_read;
/*analyze data which has read from client */
HTTP_CODE result = parse_content(buffer, checked_index, checkstate,
read_index, start_line);
if (result == NO_REQUEST)
{
continue;
}
else if (result == GET_REQUEST)
{
send(fd, szret[0], strlen(szret[0]), 0);
break;
}
else
{
send(fd, szret[1], strlen(szret[1]), 0);
break;
}
}
close(fd);
}
close(listenfd);
return 0;
}