/**************************************************************************** * lsrv_funcs2.c * functions for the license server - version 2 *    includes ticket_reclaim(), do_validate(), and expanded handle_request */#include <stdio.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <netdb.h>#include <signal.h>#include <sys/errno.h>#define SERVER_PORTNUM	2020		/* Our server's port number */#define MSGLEN		128		/* Size of our datagrams */#define TICKET_AVAIL	0		/* Slot is available for use */#define MAXUSERS	3		/* Only 3 users for us */#define	oops(x)	{ perror(x); exit(-1); }#define RECLAIM_INTERVAL 5		/* Expire every 60 seconds *//**************************************************************************** * Important variables */int ticket_array[MAXUSERS];	/* Our ticket array */int sd = -1;			/* Our socket */int num_tickets_out = 0;	/* Number of tickets outstanding */static char *do_hello();static char *do_goodbye();static char *do_validate();/**************************************************************************** * setup() - initialize license server */setup(){	sd = make_dgram_server_socket(SERVER_PORTNUM);	if ( sd == -1 )		oops("make socket");	free_all_tickets();	return sd;}free_all_tickets(){	int	i;	for(i=0; i<MAXUSERS; i++)		ticket_array[i] = TICKET_AVAIL;}/**************************************************************************** * shut_down() - close down license server */shut_down(){	close(sd);}/**************************************************************************** * handle_request(request, clientaddr, addrlen) *   branch on code in request */handle_request(char *req,struct sockaddr *client, socklen_t addlen){	char	*response;	int	ret;	/* act and compose a response */	if ( strncmp(req, "HELO", 4) == 0 )		response = do_hello(req);	else if ( strncmp(req, "GBYE", 4) == 0 )		response = do_goodbye(req);	else if ( strncmp(req, "VALD", 4) == 0 )		response = do_validate(req);	else		response = "FAIL invalid request";	/* send the response to the client */	narrate("SAID:", response, client);	ret = sendto(sd, response, strlen(response),0, client, addlen);	if ( ret == -1 )		perror("SERVER sendto failed");}/**************************************************************************** * do_hello * Give out a ticket if any are available * IN  msg_p			message received from client * Results: ptr to response *    NOTE: return is in static buffer overwritten by each call */static char *do_hello(char *msg_p){	int x;	static char replybuf[MSGLEN];	if(num_tickets_out >= MAXUSERS) 		return("FAIL no tickets available");	/* else find a free ticket and give it to client */	for(x = 0; x<MAXUSERS && ticket_array[x] != TICKET_AVAIL; x++) 		;	/* A sanity check - should never happen */	if(x == MAXUSERS) {		narrate("database corrupt","",NULL);		return("FAIL database corrupt");	}	/* Found a free ticket.  Record "name" of user (pid) in array.	 * 	generate ticket of form: pid.slot	 */	ticket_array[x] = atoi(msg_p + 5); /* get pid in msg */	sprintf(replybuf, "TICK %d.%d", ticket_array[x], x);	num_tickets_out++;	return(replybuf);} /* do_hello *//**************************************************************************** * do_goodbye * Take back ticket client is returning * IN  msg_p			message received from client * Results: ptr to response */static char *do_goodbye(char *msg_p){	int pid, slot;		/* components of ticket	*/	/* The user's giving us back a ticket.  First we need to get 	 * the ticket out of the message, which looks like:	 *	 * 	GBYE pid.slot	 */	if((sscanf((msg_p + 5), "%d.%d", &pid, &slot) != 2) ||	   (ticket_array[slot] != pid)) {		narrate("Bogus ticket", msg_p+5, NULL);		return("FAIL invalid ticket");	}	/* The ticket is valid.  Release it. */	ticket_array[slot] = TICKET_AVAIL;	num_tickets_out--;	/* Return response */	return("THNX See ya!");} /* do_goodbye *//**************************************************************************** * narrate() - chatty news for debugging and logging purposes */narrate(char *msg1, char *msg2, struct sockaddr_in *clientp){	fprintf(stderr,"\t\tSERVER: %s %s ", msg1, msg2);	if ( clientp )		fprintf(stderr,"(%s:%d)", inet_ntoa(clientp->sin_addr),					  ntohs(clientp->sin_port) );	putc('\n', stderr);}/* ------------------------ VERSION 2 ADDITIONS HERE --------------------- *//**************************************************************************** * do_validate * Validate client's ticket * IN  msg_p			message received from client * Results: ptr to response */static char *do_validate(char *msg){	int pid, slot;          /* components of ticket */	/* msg looks like VAD pid.slot - parse it and validate */	 	if (sscanf(msg+5,"%d.%d",&pid,&slot)==2 && ticket_array[slot] == pid) 		return("GOOD Valid ticket");	/* bad ticket */	narrate("Bogus ticket", msg+5, NULL);	return("FAIL invalid ticket");} /**************************************************************************** * ticket_reclaim * go through all tickets and reclaim ones belonging to dead processes * Results: none */void ticket_reclaim(){	int	i;	char	tick[BUFSIZ];	for(i = 0; i < MAXUSERS; i++) {		if((ticket_array[i] != TICKET_AVAIL) &&		   (kill(ticket_array[i], 0) == -1) && (errno == ESRCH)) {			/* Process is gone - free up slot */			sprintf(tick, "%d.%d", ticket_array[i],i);			narrate("freeing", tick, NULL);			ticket_array[i] = TICKET_AVAIL;			num_tickets_out--;		}	}	alarm(RECLAIM_INTERVAL);	/* reset alarm clock */}