【CSAPP】proxy Lab代理实验

这个实验较为简单，但是要写出来还是得花一天半天的时间。主要实现到是一个代理的功能，接受客户端到请求，再代替客户端请求服务器相应的内容后，再返回给客户端。

多线程程序gdb调试：

1.info thread 显示当前有几个线程

2.thread num  转换到标号为num的线程，当前线程结束后，通过Ctrl+C返回前一个线程

下面直接贴上代码了，并且在文章的最后说明了对该代理程序如何进行调试。

#include "csapp.h"/* * Function prototypes */void parse_url(char *ur, char *hostname, char *query_path, int *port);void format_log_entry(char *logstring, struct sockaddr_in *sockaddr, char *uri, int size);void *thread(void *arg);void client_error(int fd, char *cause, char *errnum, char *shortmsg, char *longmsg);int connect_server(char *hostname, int port, char *path );/* * varibles */struct args{    int fd;    struct sockaddr_in sockaddr;};pthread_mutex_t mutex;FILE* logfile;/*  * main - Main routine for the proxy program  */int main(int argc, char **argv){    FILE* logfile;    pthread_t tid;    /* Check arguments */    if (argc != 2) {fprintf(stderr, "Usage: %s <port number>\n", argv[0]);exit(0);    }    Signal(SIGPIPE, SIG_IGN);       logfile = Fopen("./logfile", "a");    int listenfd = Open_listenfd( atoi(argv[1]) );    while(1){        socklen_t len = sizeof(int);        struct args* p = (struct args*)Malloc(sizeof(struct args));        p->fd = Accept(listenfd, (SA*)(&p->sockaddr),&len);          Pthread_create(&tid, NULL, thread, p);    }    exit(1);}void *thread(void *arg){     rio_t rp;     char buf[MAXLINE];     char method[MAXLINE];     char url[MAXLINE];     char version[MAXLINE];         char hostname[MAXLINE];     char path[MAXLINE];      int port;     int serverfd;     int clength;     Pthread_detach(Pthread_self());     struct args* tmp = (struct args*)arg;     int fd =  tmp->fd;          struct sockaddr_in sockaddr = tmp->sockaddr;     Free(tmp);          Rio_readinitb(&rp, fd);      Rio_readlineb(&rp, buf, MAXLINE);    if(sscanf(buf, "%s %s %s", method, url, version) < 3){        fprintf(stderr, "sscanf error");        client_error(fd, method, "404","Not Found", "Not Found");          Close(fd);        return NULL;    }       if(strcmp(method,"GET")){        fprintf(stderr, "error request");        client_error(fd, method, "500","Not Implement", "Not Implement");          Close(fd);        return NULL;    }    /*忽略首部和实体*/    do{        Rio_readlineb(&rp, buf, MAXLINE);        }while(strcmp(buf, "\r\n"));        /*解析URL，请求服务器*/    parse_url(url,hostname, path, &port);     if( (serverfd = connect_server(hostname,port, path))  < 0){        Close(fd);        return NULL;    }        /*等待读取服务器响应，并送回请求客户端*/    do{       Rio_readinitb(&rp, serverfd);       Rio_readlineb(&rp, buf, MAXLINE);              if(strstr(buf, "Content-length:")){            sscanf(buf, "Content-length: %d\r\n", &clength);       Rio_writen(fd, buf, MAXLINE);       }      }while(strcmp(buf,"\r\n"));                char logstring[MAXLINE];        pthread_mutex_lock(&mutex);       format_log_entry(logstring, &sockaddr, url, clength);       pthread_mutex_unlock(&mutex);       fprintf(logfile, "%s\n", logstring);       fflush(logfile);       close(fd);       close(serverfd);}int connect_server(char *hostname, int port, char *path ){    static const char *user_agent = "User-Agent: Mozilla (X11; Linux i386; rv:10.0.3) Gecko/20120305 Firefox/10.0.3\r\n";    static const char *accept_str= "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\nAccept-Encoding: gzip, deflate\r\n";    static const char *connection = "Connection: close\r\nProxy-Connection: close\r\n";        char buf[MAXLINE];    /* connect to server */    int proxy_clientfd;    proxy_clientfd=open_clientfd(hostname,port);    /* if failed return */    if(proxy_clientfd<0)        return proxy_clientfd;    /* write request to server */    sprintf(buf,"GET %s HTTP/1.0\r\n", path);    Rio_writen(proxy_clientfd,buf,strlen(buf));    sprintf(buf,"Host: %s\r\n",hostname);    Rio_writen(proxy_clientfd,buf,strlen(buf));    Rio_writen(proxy_clientfd,user_agent,strlen(user_agent));    Rio_writen(proxy_clientfd,accept_str,strlen(accept_str));    Rio_writen(proxy_clientfd,connection,strlen(connection));    Rio_writen(proxy_clientfd,"\r\n",strlen("\r\n"));    printf("request to server is done.");    return proxy_clientfd;}/* parse request url */void parse_url(char *ur, char *hostname, char *query_path, int *port){    char url[100];    url[0]='\0';    strcat(url,ur);    hostname[0]=query_path[0]='\0';    char *p=strstr(url,"//");        /* skip "http://" and "https://" */    if(p!=NULL) {        p=p+2;    } else {        p=url;    }    char *q=strstr(p,":");            /* read ":<port>" and "/index.html" */    if(q!=NULL) {        *q='\0';        sscanf(p,"%s",hostname);        sscanf(q+1,"%d%s",port,query_path);    } else {        q=strstr(p,"/");        if(q!=NULL) {            *q='\0';            sscanf(p,"%s",hostname);            *q='/';            sscanf(q,"%s",query_path);        } else {            sscanf(p,"%s",hostname);        }        *port=80;    }    /* the default path */    if(strlen(query_path)<=1)        strcpy(query_path,"/index.html");    return;}/* * format_log_entry - Create a formatted log entry in logstring.  *  * The inputs are the socket address of the requesting client * (sockaddr), the URI from the request (uri), and the size in bytes * of the response from the server (size). */void format_log_entry(char *logstring, struct sockaddr_in *sockaddr,       char *uri, int size){    time_t now;    char time_str[MAXLINE];    unsigned long host;    unsigned char a, b, c, d;    /* Get a formatted time string */    now = time(NULL);    strftime(time_str, MAXLINE, "%a %d %b %Y %H:%M:%S %Z", localtime(&now));    /*      * Convert the IP address in network byte order to dotted decimal     * form. Note that we could have used inet_ntoa, but chose not to     * because inet_ntoa is a Class 3 thread unsafe function that     * returns a pointer to a static variable (Ch 13, CS:APP).     */    host = ntohl(sockaddr->sin_addr.s_addr);    a = host >> 24;    b = (host >> 16) & 0xff;    c = (host >> 8) & 0xff;    d = host & 0xff;    /* Return the formatted log entry string */    sprintf(logstring, "%s: %d.%d.%d.%d %s", time_str, a, b, c, d, uri);}void client_error(int fd, char *cause, char *errnum,                  char *shortmsg, char *longmsg) {    char buf[MAXLINE], body[MAXBUF];    /* Build the HTTP response body */    sprintf(body, "%s: %s\r\n", errnum, shortmsg);    sprintf(body, "%s%s: %s", body, longmsg, cause);    /* Print the HTTP response */    sprintf(buf, "HTTP/1.0 %s %s\r\n", errnum, shortmsg);    Rio_writen(fd, buf, strlen(buf));    sprintf(buf, "Content-type: text/html\r\n");    Rio_writen(fd, buf, strlen(buf));    sprintf(buf, "Content-length: %d\r\n\r\n", (int)strlen(body));    Rio_writen(fd, buf, strlen(buf));    Rio_writen(fd, body, strlen(body));}

如何调试本程序：使用nc这个小巧的工具，常见用法自行man。

在这里我们先选择一个空闲到端口，并在一个终端执行以下命令：

nc -l 5000

此命令使得nc作为端口5000的监听服务器，可以接受信息。

然后我们再选择一个空闲端口运行代理程序：

./proxy 10000 &

接着，我们使用curl这个工具模拟客户端产生HTTP请求：

curl  -v  -proxy  http://127.0.0.1:10000/  http://127.0.0.1:500/

此时我们便能看到服务器接收到我们客户端发出的请求了。