Networks and Protocols Course: International University Bremen Date: Dr. Jürgen Schönwälder Deadline:

Transcription

1 Networks and Protocols Course: International University Bremen Date: Dr. Jürgen Schönwälder Deadline: Problem Sheet #10 Problem 10.1: finger rpc server and client implementation ( =10 points) The finger protocol (described in RFC 1288) can be used to retrieve information about accounts active on remote systems. You have already implemented the finger protocol as part of previous homeworks. This time, you have to implement the finger service by using ONC remote procedure calls. particular, you have to solve the following tasks: In a) Write an XDR RPC language definition which defines RPC procedures for retrieving user information in long and short format. The procedures should allow a client to specify whether information for a particular user is retrieved or information about all active users on the system. b) Use the rpcgen tool to generate stub functions from the remote procedure definition. c) Write a client application which performs RPC calls to retrieve the requested information. Your client should accept the following command syntax: finger [-l] [-s] [user]@host Elements in square brackets are optional. The -l option requests long format while the -s option requests short format. If no option is given, the format defaults to short format when the user name is empty and long format otherwise. Some examples: finger root@thesun.iu-bremen.de finger finger -s root@thesun.iu-bremen.de Make sure your program handles all possible errors. d) Write a server application which implements the RPC functions. Again, make sure your program handles all possible errors. Solution: Below is a sample finger RPC definition. finger.x -- Definition of a simple finger service. Using the RPC interface, it probably does not really make sense to distinguish between short and long format anymore. But we do so in order to be consistent with the original finger service. const LOGIN_MAXLEN = 32; const USER_MAXLEN = 32; const TTY_MAXLEN = 32; struct finger string login<login_maxlen>;

2 string user<user_maxlen>; string tty<tty_maxlen>; ; typedef finger finger_array<>; program FINGERPROG = ; version FINGER_1 finger_array finger_short(string user<user_maxlen>) = 1; finger_array finger_long(string user<user_maxlen>) = 2; = 1; Below is a sample finger RPC client implementation. finger-rpc/finger_client.c -- Implementation of the finger client for the finger RPC server. #include "finger.h" #include <unistd.h> static const char progname = "finger"; finger_at_host(const char user, const char host, const int lflag) CLIENT clnt; finger_array result; char arg = (char ) user; int i; #ifndef DEBUG clnt = clnt_create (host, FINGERPROG, FINGER_1, "udp"); if (clnt == NULL) clnt_pcreateerror (host); exit(exit_failure); #endif DEBUG result = (lflag)? finger_long_1(&arg, clnt) : finger_short_1(&arg, clnt); if (result == NULL) clnt_perror(clnt, "call failed"); clnt_destroy(clnt); if (! lflag) printf("%-8s %-24s %-12s \r\n", "Login", "Name", "Tty"); for (i = 0; i < result->finger_array_len; i++) finger f = &result->finger_array_val[i]; if (lflag) printf("%slogin: %-24s Name: %-24s\r\nTty: %s\r\n",

3 i? "\r\n" : "", f->login, f->user? f->user : "?", f->tty); else printf("%-8s %-24s %-12s \r\n", f->login, f->user? f->user : "?", f->tty); #ifndef DEBUG clnt_destroy(clnt); #endif DEBUG int main (int argc, char argv[]) int i, c; char user, host; int lopt = 0, sopt = 0, lflag; while ((c = getopt(argc, argv, "ls")) >= 0) switch (c) case l : lopt = 1; sopt = 0; break; case s : sopt = 1; lopt = 0; break; if (argc == optind) fprintf(stderr, "usage: %s [-l] [-s] [-p port] [user]@host...\n", progname); return EXIT_FAILURE; for (i = optind; i < argc; i++) if (i > optind) printf("\n"); user = argv[i]; host = ); if (! host) fprintf(stderr, "%s: format must be [user]@host\n", progname); continue; host = 0; host++; lflag = (user[0]!= 0); if (sopt) lflag = 0; if (lopt) lflag = 1; finger_at_host(user, host, lflag);

4 return EXIT_SUCCESS; Below is a sample finger RPC server implementation. finger-rpc/finger_server.c -- Implementation of the finger procedures on the RPC server side. Both RPC calls (short and long format) are implemented using a common internal function. #include "finger.h" #define _GNU_SOURCE #include <stdio.h> #include <sys/types.h> #include <utmp.h> #include <pwd.h> #define WFLAG 0x01 finger_free(finger_array result) int i; if (! result->finger_array_val) for (i = 0; i < result->finger_array_len; i++) if (result->finger_array_val[i].login) free(result->finger_array_val[i].login); if (result->finger_array_val[i].user) free(result->finger_array_val[i].user); if (result->finger_array_val[i].tty) free(result->finger_array_val[i].tty); if (result->finger_array_val) free(result->finger_array_val); result->finger_array_val = NULL; result->finger_array_len = 0; finger_impl(finger_array result, const char user, int flags) int cnt = 0, alloc = 0; struct utmp utent; struct passwd pw; setutent(); while ((utent = getutent())!= NULL) if (utent->ut_type == USER_PROCESS && (! user! user strcmp(user, utent->ut_user) == 0)) if (alloc <= cnt) alloc += 10;

5 result->finger_array_val = realloc(result->finger_array_val, alloc sizeof(finger)); if (! result->finger_array_val) result->finger_array_len = 0; pw = getpwnam(utent->ut_user); result->finger_array_val[cnt].login = strdup(utent->ut_user); result->finger_array_val[cnt].user = strdup( (pw && pw->pw_gecos)? pw->pw_gecos : "?"); result->finger_array_val[cnt].tty = strdup( (flags & WFLAG)? utent->ut_line : ""); cnt++; result->finger_array_len = cnt; finger_array finger_short_1_svc(char argp, struct svc_req rqstp) static finger_array result = 0, NULL ; finger_free(&result); finger_impl(&result, argp? argp : NULL, 0); return &result; finger_array finger_long_1_svc(char argp, struct svc_req rqstp) static finger_array result = 0, NULL ; finger_free(&result); finger_impl(&result, argp? argp : NULL, WFLAG); return &result;