unix-linux编程实践教程习题解答及代码.rar

/** sol12.4.c ** ------------------------------------------------------------ A version of webserv that logs all requests and the status of their replies is sol12.4.c. This program accepts the name of the logfile on the command line (with the -l filename option) and uses O_APPEND so it can write to the log safely. The program uses the fact that accept() records the address of the client. ** ------------------------------------------------------------ ** ** * webserv with new feature: logs requests and outcome of each request * * details of log function * a) Log is opened at start in O_APPEND mode to ensure that * multiple children will not lose data to race conditions * b) Each accept will record the ip address of the caller * That address will be passed to the child. * c) Each time a header is printed out, the webserver will * add to the log the time, the caller's ip number, * the request, and the first line of the header * (note: this requires passing the callers ipaddr down to * the request processing code) * * The method is to create a serverlog() object that stores * data in static variables and then can be told to write out * the information. * * webserv.c - a minimal web server (version 0.3) * usage: ws portnumber [ -l logfile ] * features: supports the GET command only * runs in the current directory * forks a new child to handle each request * has MAJOR security holes, for demo purposes only * has many other weaknesses, but is a good start * * build: cc sol12.4.c socklib.c -o sol12.4 */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #include <string.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <errno.h> #include <time.h> #include <ctype.h> #include "socklib.h" #define oops(s) { perror(s); exit(1);} int server_log(int, void *); int setup(int , char **); void read_til_crnl(FILE *); void process_rq( char *, int , struct in_addr ); void header( FILE *, char *); void cannot_do(int ); void do_404(char *, int ); int isadir(char *); int not_exist(char *); void do_ls(char *, int ); char * file_type(char *); int ends_in_cgi(char *); void do_exec( char *, int); void do_cat(char *, int ); int server_log(int , void *); int logwrite(int , struct in_addr , char *, char *); void safecpy(char *, char *, int ); /* ----------------------------------------------------- * logfile header material. Should be in serverlog.h */ #define LOGMODE 0600 #define SL_OPEN 0 #define SL_ADDR 1 #define SL_REQ 2 #define SL_REPLY 3 #define REPLY_MAX 10 #define REQUEST_MAX 2048 /* longest request allowed */ /* --- end of serverlog.h ------------ */ int main(int ac, char *av[]) { int sock, fd; FILE *fpin; char request[BUFSIZ]; struct sockaddr_in clnt_addr; int len; sock = setup(ac, av); /* * setup - process command line arguments * * returns a socket for the server * handles -l logfile opt * */ /* main loop here */ while(1){ /* wait for a call */ len = sizeof(struct sockaddr); fd = accept( sock, (struct sockaddr *) &clnt_addr, &len); /* * skip the EINTR returns from accept */ if ( fd == -1 && errno == EINTR ) continue; if ( fd == -1 ) oops("accept"); fpin = fdopen(fd, "r" ); /* read request */ fgets(request,BUFSIZ,fpin); printf("got a call: request = %s", request); read_til_crnl(fpin); /* do what client asks */ process_rq(request, fd, clnt_addr.sin_addr); fclose(fpin); } return 0; } int setup(int ac, char *av[]) { int portnum = -1; char *logfile = NULL; int pos; int sock; /* parse */ for(pos=1; pos<ac; pos++) { if ( isdigit(av[pos][0]) ) portnum = atoi(av[pos]); else if ( strcmp(av[pos], "-l") == 0 ){ if ( ++pos < ac ) logfile = av[pos]; else { fprintf(stderr,"missing logfilename\n"); exit(1); } } } /* act: make socket, make log object */ if ( portnum == -1 ){ fprintf(stderr,"usage: ws portnum\n"); exit(1); } sock = make_server_socket( portnum ); if ( sock == -1 ) { perror("socket"); exit(2); } if ( logfile ) server_log(SL_OPEN, logfile); return sock; } /* ------------------------------------------------------ * read_til_crnl(FILE *) skip over all request info until a CRNL is seen ------------------------------------------------------ */ void read_til_crnl(FILE *fp) { char buf[BUFSIZ]; while( fgets(buf,BUFSIZ,fp) != NULL && strcmp(buf,"\r\n") != 0 ) ; } /* ------------------------------------------------------ * process_rq( char *rq, int fd, struct in_addr caller ) do what the request asks for and write reply to fd handles request in a new process rq is HTTP command: GET /foo/bar.html HTTP/1.0 ------------------------------------------------------ */ void process_rq( char *rq, int fd , struct in_addr caller) { char cmd[BUFSIZ], arg[BUFSIZ]; /* create a new process and return if not the child */ if ( fork() != 0 ) return; /* add more data to the log entry */ server_log(SL_REQ, rq); server_log(SL_ADDR, &caller); strcpy(arg, "./"); /* precede args with ./ */ if ( sscanf(rq, "%s%s", cmd, arg+2) != 2 ) return; if ( strcmp(cmd,"GET") != 0 ) cannot_do(fd); else if ( not_exist( arg ) ) do_404(arg, fd ); else if ( isadir( arg ) ) do_ls( arg, fd ); else if ( ends_in_cgi( arg ) ) do_exec( arg, fd ); else do_cat( arg, fd ); } /* ------------------------------------------------------ * the reply header thing: all functions need one if content_type is NULL then don't send content type ------------------------------------------------------ */ void header( FILE *fp, char *content_type ) { fprintf(fp, "HTTP/1.0 200 OK\r\n"); if ( content_type ) fprintf(fp, "Content-type: %s\r\n", content_type ); server_log(SL_REPLY, "200"); } /* ------------------------------------------------------ * simple functions first: cannot_do(fd) unimplemented HTTP command and do_404(item,fd) no such object ------------------------------------------------------ */ void cannot_do(int fd) { FILE *fp = fdopen(fd,"w"); fprintf(fp, "HTTP/1.0 501 Not Implemented\r\n"); fprintf(fp, "Content-type: text/plain\r\n"); fprintf(fp, "\r\n"); fprintf(fp, "That command is not yet implemented\r\n"); fclose(fp); server_log(SL_REPLY, "501"); } void do_404(char *item, int fd) { FILE *fp = fdopen(fd,"w"); fprintf(fp, "HTTP/1.0 404 Not Found\r\n"); fprintf(fp, "Content-type: text/plain\r\n"); fprintf(fp, "\r\n"); fprintf(fp, "The item you requested: %s\r\nis not found\r\n", item); fclose(fp); server_log(SL_REPLY, "404"); } /* ------------------------------------------------------ * the directory listing section isadir() uses stat, not_exist() uses stat do_ls runs ls. It should not ------------------------------------------------------ */ int isadir(char *f) { struct stat info; return ( stat(f, &info) != -1 && S_ISDIR(info.st_mode) ); } int not_exist(char *f) { struct stat info; return( stat(f,&info) == -1 ); } void do_ls(char *dir, int fd) { FILE *fp ; fp = fdopen(fd,"w"); header(fp, "text/plain"); fprintf(fp,"\r\n"); fflush(fp); dup2(fd,1); dup2(fd,2); close(fd); execlp("ls","ls","-l",dir,NULL); perror(dir); exit(1); } /* ------------------------------------------------------ * the cgi stuff. function to check extension and one to run the program. ------------------------------------------------------ */ /* returns 'extension' of file */ char * file_type(char *f) { char *cp; if ( (cp = strrchr(f, '.' )) != NULL ) return cp+1; return ""; } int ends_in_cgi(char *f) { return ( strcmp( file_type(f), "cgi" ) == 0 ); } void do_exec( char *prog, int fd ) { FILE *fp ; fp = fdopen(fd,"w"); header(fp, NULL); fflush(fp);