/*
	mserver.c

	internet modem server with lockfile support

	v0.10	5-9-94	Carl Declerck
	v0.11	1-10-94 ""
	v0.20	3-10-94 ""
	v0.21	16-4-96 "" (added tcpconn.c)
	v0.22	15-1-98 "" (improved SIGCHLD handling, ipaddr ACL bugfix)
	v0.23	18-1-98 "" (added syslogging, added baudrates >38400)
	v0.23a	28-1-98 "" (fixed endless loop on wait4())
*/


#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <ctype.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <errno.h>
#include <termios.h>
#include <netdb.h>
#include <syslog.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/time.h>

#include "config.h"
#include "stty.h"

#define VERSION		"0.23a"
#define BUFF_SIZE	4096

#ifndef PATH_MAX
#define PATH_MAX	512
#endif

#define DEV_BUSY	"DEVICE BUSY"
#define DEV_NOACCESS	"DEVICE INACCESSIBLE"
#define DEV_ERROR	"DEVICE ERROR"

#define max(x,y)	((x) > (y) ? (x) : (y))

typedef struct _netmodem
	{
		int chldpid;
		char *devname;
		char *params;
		char *clients;
		struct _netmodem *next;
	} NETMODEM;

typedef struct _netport
	{
		int port;
		int servfd;
		NETMODEM *netmods;
		struct sockaddr_in addr;
		struct _netport *next;
	} NETPORT;


NETPORT *netports = NULL;
char tmppath[PATH_MAX];


void errorf (char *fmt, ...)
{
	va_list argptr;

	va_start (argptr, fmt);
	fprintf (stderr, "mserver: ");
	vfprintf (stderr, fmt, argptr);
	exit (1);
}

/* read a single line from a stream, ignoring all irrelevant stuff */

int  read_line (char *buff, FILE *f)
{
    int b, i;

    *buff = 0;
    do
    {
        while ((b = fgetc(f)) != EOF && isspace(b));
        if (b == EOF) return (0);
        for (i = 0; b != EOF && b != '\n' && b != '\r'; i++)
        {
            buff[i] = (b == '\t') ? ' ': b;
            b = fgetc(f);
        }
        buff[i] = 0;
    }
    while (*buff == '#');

    return (1);
}

/* extract the first word from a string */

char *parse_arg (char *arg, char *buff)
{
	int i = 0, j = 0, quote = 0;

	*arg = 0;
	if (buff == NULL)
		return (NULL);
		
	while (buff[i] && isspace(buff[i])) i++;
	while (buff[i] && (!isspace(buff[i]) || quote))
	{
		switch (buff[i])
		{
			case '\\' :	arg[j++] = buff[++i]; break;
			case '"'  :	quote = !quote; break;
			default   :	arg[j++] = buff[i];
		}
		i++;
    	}	
	while (buff[i] && isspace(buff[i])) i++;
	arg[j] = 0;

	return (j ? buff + i : NULL);
}

int match (const char *s, const char *wc)
{
	while (*wc)
	{
		if (*s == *wc || *wc == '?')
		{
			wc++;
			s++;
		}
		else if (*wc == '*')
		{
			if (!*(++wc))
				return (1);

			while (!match(s, wc))
				if (!*(++s))
					return (0);
		}
		else
			return (0);
	}

	return (!*s);
}

char *leafname (char *path)
{
	int i = 0, j;
	
	for (j = 0; path[j]; j++)
		if (path[j] == '/')
			i = j + 1;
	
	return (path + i);
}

void read_config (void)
{
	NETPORT **wport;
	NETMODEM *tmpmod;
	FILE *f;
	int p;
	char line[BUFF_SIZE], arg[BUFF_SIZE], *tail;

	if ((f = fopen(CONFIG, "r")) == NULL)
		errorf ("can't open config file '%s'\n", CONFIG);

	while (read_line(line, f))
	{
		tail = parse_arg(arg, line);

		if ((p = atoi(arg)) < 0)
			errorf ("illegal port %d\n", p);

		for (wport = &netports; *wport && (*wport)->port != p; wport = &(*wport)->next);
		if (*wport == NULL)
		{
			if ((*wport = (NETPORT *) malloc(sizeof(NETPORT))) == NULL)
				errorf ("can't allocate space for netport\n");

			(*wport)->netmods = NULL;
			(*wport)->port = p;
			(*wport)->servfd = -1;
			(*wport)->next = NULL;
		}

		tmpmod = (*wport)->netmods;
		if (((*wport)->netmods = (NETMODEM *) malloc(sizeof(NETMODEM))) == NULL)
			errorf ("can't allocate space for exported modem\n");

		(*wport)->netmods->next = tmpmod;
		(*wport)->netmods->chldpid = -1;

		tail = parse_arg(arg, tail);
		if (access(arg, F_OK) != 0)
			errorf ("can't export non-existant modem (%s)\n", arg);
		strcpy ((*wport)->netmods->devname = malloc(strlen(arg) + 1), arg);

		tail = parse_arg(arg, tail);
		strcpy ((*wport)->netmods->params = malloc(strlen(arg) + 1), arg);

		tail = parse_arg(arg, tail);
		strcpy ((*wport)->netmods->clients = malloc(strlen(arg) + 1), arg);
	}

	fclose (f);
}			

void bind_ports (void)
{
	NETPORT *w;

	for (w = netports; w; w = w->next)
	{
		if ((w->servfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
			errorf ("can't create server socket\n");

		bzero ((char *) &w->addr, sizeof(w->addr));
		w->addr.sin_family = AF_INET;
		w->addr.sin_addr.s_addr = htonl(INADDR_ANY);
		w->addr.sin_port = htons(w->port);
		if (bind(w->servfd, (struct sockaddr *)	&w->addr, sizeof(w->addr)) < 0)
			errorf ("can't bind server socket\n");

		if (listen(w->servfd, 5) < 0)
			errorf ("can't listen on server socket\n");
	}
}

char lockpath[PATH_MAX];

int create_lock (char *devname)
{
	FILE *f;
	int ok;

	if ((f = fopen(tmppath, "w")) == NULL)
		return (0);

	fprintf (f, "%10d", getpid());
	fclose (f);

	sprintf (lockpath, "%s/LCK..%s", LOCK_DIR, leafname(devname));
	ok = (link(tmppath, lockpath) == 0);
	unlink (tmppath);

	return (ok);
}

static struct { int ibaud, speed; } btable[] = 
	{
#if !defined(BSD)
		{ 460800,	B460800 },
#endif
		{ 230400,	B230400 },
		{ 115200,	B115200 },
		{ 57600,	B57600 },
		{ 38400,	B38400 },
		{ 19200,	B19200 },
		{ 9600,		B9600 },
		{ 4800, 	B4800 },
		{ 4800, 	B4800 },
		{ 2400,		B2400 },
		{ 1200,		B1200 },
		{ 600,		B600 },
		{ 300,		B300 },
		{ 200,		B200 },
		{ 150,		B150 },
		{ 110,		B110 },
		{ 75,		B75 },
		{ 50,		B50 },
		{ 0,		0 }
	};

static struct { int idata, cdata; } dtable[] =
	{
		{ 8,	CS8 },
		{ 7,	CS7 },
		{ 6,	CS6 },
		{ 5,	CS5 },
		{ 0,	0 }
	};

void set_lineparams (int fd, char *par)
{
	struct termios tio;
	speed_t speed = B38400;
	int i, baud, data = CS8, stop = 1, parity = 0;
	char *p;

	if ((p = strtok(par, ",")) != NULL)
		baud = atoi(p);
	if ((p = strtok(NULL, ",")) != NULL)
		data = atoi(p);
	if ((p = strtok(NULL, ",")) != NULL)
		parity = toupper(*p);
	if ((p = strtok(NULL, ",")) != NULL)
		stop = atoi(p);

	for (i = 0; btable[i].ibaud; i++)
		if (baud == btable[i].ibaud)
		{
			speed = btable[i].speed;
			break;
		}

	for (i = 0; dtable[i].idata; i++)
		if (data == dtable[i].idata)
		{
			data = dtable[i].cdata;
			break;
		}

	switch (parity)
	{
		case 'E' : parity = PARENB; break;
		case 'O' : parity = PARENB | PARODD; break;
		default  : parity = IGNPAR; break;
	}

	tcgetattr (fd, &tio);
	tio.c_cflag &= ~CSIZE;
	tio.c_cflag |= data;
	tio.c_iflag = (parity == IGNPAR) ? (tio.c_iflag | IGNPAR) : (tio.c_iflag & ~IGNPAR);
	tio.c_cflag = (parity == IGNPAR) ? tio.c_cflag : (tio.c_cflag | parity);
	tio.c_cflag = (stop == 2) ? (tio.c_cflag | CSTOPB) : (tio.c_cflag & ~CSTOPB);
	cfsetispeed (&tio, speed);
	cfsetospeed (&tio, speed);
	tcsetattr (fd, TCSANOW, &tio);
}

void closedown_netmodem (void)
{
	if (*lockpath) {
		unlink (lockpath);
		syslog (LOG_INFO, "device released");
	}
	stty_orig ();
}

void connect_netmodem (NETPORT *port, int sockfd, struct sockaddr_in *peer)
{
	FILE *f;
	NETMODEM *mod;
	struct hostent *phost;
	struct in_addr iaddr;
	fd_set readset;
	int n, devfd, ok, fdmax = 0, quit = 0, *pidp;
	char buff[BUFF_SIZE], *s, **ss;

	for (mod = port->netmods; mod; mod = mod->next)
		if (mod->chldpid == -1)
			if (create_lock(mod->devname))
				break;
	if (mod == NULL)	
	{
		pidp = &ok;
		*lockpath = 0;
	}
	else
		pidp = &mod->chldpid;

	*pidp = fork();
	if (*pidp < 0) {
		if (*lockpath)
			unlink (lockpath);
		return;
	} else if (*pidp > 0)
		return;

	/* child */

	atexit (closedown_netmodem);
	dup2 (sockfd, STDOUT_FILENO);

	openlog ("mserver", LOG_PID, LOG_DAEMON);

	phost = gethostbyaddr((char *) &peer->sin_addr, sizeof(peer->sin_addr), AF_INET);

	/* all modems on this port in use? */

	if (mod == NULL)
	{
		printf ("%s\r\n", DEV_BUSY);
		syslog (LOG_INFO, "device busy for %s", phost->h_name);
		exit (1);
	}

	/* is the peer allowed to connect to this modem? */

	ok = 0;
	s = *mod->clients ? strtok(mod->clients, ",") : mod->clients;
	do
	{
		if (match(inet_ntoa(peer->sin_addr), s))
			ok = 1;
		else if (!*s || match(phost->h_name, s))
			ok = 1;
		else for (ss = phost->h_aliases; !ok && *ss; ss++)
			if (match(*ss, s))
				ok = 1;
	}
	while (!ok && (s = strtok(NULL, ",")) != NULL);
	
	if (!ok)
	{
		printf ("%s\r\n", DEV_NOACCESS);
		syslog (LOG_INFO, "rejected access to %s for %s", mod->devname, phost->h_name);
		exit (1);
	}

	/* we'll probably be around for a while so update pid in lockfile */

	if ((f = fopen(lockpath, "w")) != NULL) {
		fprintf (f, "%10d", getpid());
		fclose (f);
	}

	/* open device */

	if ((devfd = open(mod->devname, O_RDWR)) < 0)
	{
		printf ("%s\r\n", DEV_ERROR);
		exit (1);
	}

	/* close stdout and set line discipline */

	close (STDOUT_FILENO);
	stty_initstore ();
	stty_raw (devfd);
	stty_clocal (devfd, 1);
	set_lineparams (devfd, mod->params);

	fdmax = max(sockfd, devfd);

	syslog (LOG_INFO, "granted access to %s for %s", mod->devname, phost->h_name);

	/* main server loop */

	while (!quit)
	{
		FD_ZERO (&readset);
		FD_SET (devfd, &readset);
		FD_SET (sockfd, &readset);
		select (fdmax + 1, &readset, NULL, NULL, NULL);

		if (FD_ISSET(devfd, &readset))
		{
			if ((n = read(devfd, buff, BUFF_SIZE)) > 0)
			{
				if (write(sockfd, buff, n) < 0)
					exit (1);
			}
		}

		if (FD_ISSET(sockfd, &readset))
		{
			if ((n = read(sockfd, buff, BUFF_SIZE)) > 0)
			{
				if (write(devfd, buff, n) < 0)
					exit (1);
			}
			else quit = 1;
		}
	}

	exit (0);
}

void sigchld (int sig)
{
	NETPORT *wport;
	NETMODEM *wmod;
	int pid, status;

	while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
		for (wport = netports; wport; wport = wport->next)
			for (wmod = wport->netmods; wmod; wmod = wmod->next)
				if (pid == wmod->chldpid)
					wmod->chldpid = -1;
	}
}

int main (int argc, char **argv)
{
	NETPORT *wport;
	fd_set readset;
	struct sigaction sig;
	struct sockaddr_in peer;
	int len, sockfd, fdmax;

	/* setup */

	read_config ();
	bind_ports ();
	sprintf (tmppath, "%s/tmp_lck.%d", LOCK_DIR, getpid());

	/* daemonize */

	close (STDIN_FILENO); close (STDOUT_FILENO); close (STDERR_FILENO);
	if (fork() != 0) exit (0);
	chdir ("/");
#if !defined(BSD)
	setpgrp ();
#endif
	signal (SIGHUP, SIG_IGN);
	if (fork() != 0) exit (0);

	sigemptyset (&sig.sa_mask);
	sigaddset (&sig.sa_mask, SIGCHLD);
	sig.sa_handler = sigchld;
	sig.sa_flags = 0;
	/* sig.sa_flags = SA_RESTART; */
	if (sigaction(SIGCHLD, &sig, NULL) < 0)
		exit (1);

	/* tell'em we appear to be up & ok */

	openlog ("mserver", LOG_PID, LOG_DAEMON);
	syslog (LOG_INFO, "v%s starting ...", VERSION);
	closelog ();

	/* main daemon loop */

	while (1)
	{
		do
		{
			fdmax = 0;
			FD_ZERO (&readset);
			for (wport = netports; wport; wport = wport->next)	
				/* if (wport->chldpid == -1) */
				{
					FD_SET (wport->servfd, &readset);
					if (wport->servfd > fdmax)
						fdmax = wport->servfd;
				}
		}
		while (select(fdmax + 1, &readset, NULL, NULL, NULL) == -1 && errno == EINTR);

		for (wport = netports; wport; wport = wport->next)
			if (FD_ISSET(wport->servfd, &readset))
			{
				len = sizeof(peer);
				if ((sockfd = accept(wport->servfd, 
					(struct sockaddr *) &peer, &len)) >= 0)
				{
					/* reap any stale children */
					sigchld (SIGCHLD);

					connect_netmodem (wport, sockfd, &peer);
					close (sockfd);
				}
			}
	}

	return (0);
}