telco.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

	default:
		return "file is a directory";
	case Qctl:
		d = &dev[DEV(f->qid)];
		clen = strlen(cmsg);
		if(cnt < clen || strncmp(thdr.data, cmsg, clen) != 0){
			/*
			 *  send control message to real control file
			 */
			if(seek(d->ctl, off, 0) < 0 || write(d->ctl, thdr.data, cnt) < 0){
				errstr(errbuf, sizeof errbuf);
				return errbuf;
			}
		} else {
			/*
			 *  connect
			 */
			cnt -= clen;
			if(cnt >= sizeof(buf))
				cnt = sizeof(buf) - 1;
			if(cnt < 0)
				return Ebadaddr;
			strncpy(buf, &thdr.data[clen], cnt);
			buf[cnt] = 0;
			cp = dialout(d, buf);
			if(cp)
				return cp;
		}
		rhdr.count = cnt;
		break;
	case Qdata:
		d = &dev[DEV(f->qid)];
		if(write(d->data, thdr.data, cnt) < 0){
			errstr(errbuf, sizeof errbuf);
			return errbuf;
		}
		rhdr.count = cnt;
		break;
	}
	return 0;
}

char *
rclunk(Fid *f)
{
	Dev *d;

	if(f->open)
		switch(TYPE(f->qid)){
		case Qdata:
		case Qctl:
			d = &dev[DEV(f->qid)];
			if(d->open == 1)
				onhook(d);
			d->open--;
			break;
		}
	free(f->user);
	f->busy = 0;
	f->open = 0;
	return 0;
}

char *
rremove(Fid *f)
{
	USED(f);
	return Eperm;
}

char *
rstat(Fid *f)
{
	Dir d;

	d.qid = f->qid;
	rhdr.stat = statbuf;
	rhdr.nstat = devstat(&d, statbuf, sizeof statbuf);
	return 0;
}

char *
rwstat(Fid *f)
{
	Dev *d;
	Dir dir;

	if(TYPE(f->qid) < Qlvl3)
		return Eperm;

	convM2D(thdr.stat, thdr.nstat, &dir, rhdr.data);	/* rhdr.data is a known place to scribble */
	d = &dev[DEV(f->qid)];

	/*
	 * To change mode, must be owner
	 */
	if(d->perm != dir.mode){
		if(strcmp(f->user, d->user) != 0)
		if(strcmp(f->user, user) != 0)
			return Eperm;
	}

	/* all ok; do it */
	d->perm = dir.mode & ~DMDIR;
	return 0;
}

Fid *
newfid(int fid)
{
	Fid *f, *ff;

	ff = 0;
	for(f = fids; f; f = f->next)
		if(f->fid == fid)
			return f;
		else if(!ff && !f->busy)
			ff = f;
	if(ff){
		ff->fid = fid;
		return ff;
	}
	f = emalloc(sizeof *f);
	f->fid = fid;
	f->next = fids;
	fids = f;
	return f;
}

/*
 *  read fs requests and dispatch them
 */
void
io(void)
{
	char *err;
	int n;

	for(;;){
		/*
		 * reading from a pipe or a network device
		 * will give an error after a few eof reads
		 * however, we cannot tell the difference
		 * between a zero-length read and an interrupt
		 * on the processes writing to us,
		 * so we wait for the error
		 */
		n = read9pmsg(mfd[0], mdata, messagesize);
		if(n == 0)
			continue;
		if(n < 0)
			error("mount read");
		if(convM2S(mdata, n, &thdr) != n)
			error("convM2S error");

		rhdr.data = (char*)mdata + IOHDRSZ;
		if(!fcalls[thdr.type])
			err = "bad fcall type";
		else
			err = (*fcalls[thdr.type])(newfid(thdr.fid));
		if(err){
			if(*err == 0)
				continue;	/* assigned to a slave */
			rhdr.type = Rerror;
			rhdr.ename = err;
		}else{
			rhdr.type = thdr.type + 1;
			rhdr.fid = thdr.fid;
		}
		rhdr.tag = thdr.tag;
		n = convS2M(&rhdr, mdata, messagesize);
		if(write(mfd[1], mdata, n) != n)
			error("mount write");
	}
}


int
perm(Fid *f, Dev *d, int p)
{
	if((p*Pother) & d->perm)
		return 1;
	if(strcmp(f->user, user)==0 && ((p*Pgroup) & d->perm))
		return 1;
	if(strcmp(f->user, d->user)==0 && ((p*Powner) & d->perm))
		return 1;
	return 0;
}

void
error(char *s)
{
	fprint(2, "%s: %s: %r\n", argv0, s);
	syslog(0, LOGFILE, "%s: %r", s);
	remove("/srv/telco");
	postnote(PNGROUP, getpid(), "exit");
	exits(s);
}

void *
emalloc(ulong n)
{
	void *p;

	p = mallocz(n, 1);
	if(!p)
		error("out of memory");
	return p;
}

void *
erealloc(void *p, ulong n)
{
	p = realloc(p, n);
	if(!p)
		error("out of memory");
	return p;
}

/*
 *  send bytes to modem
 */
int
send(Dev *d, char *x)
{
	if(verbose)
		syslog(0, LOGFILE, "->%s", x);
	return write(d->data, x, strlen(x));
}

/*
 *  apply a string of commands to modem
 */
int
apply(Dev *d, char *s, char *substr, int secs)
{
	char buf[128];
	char *p;
	int c, m;

	p = buf;
	m = Ok;
	while(*s){
		c = *p++ = *s++;
		if(c == '\r' || *s == 0){
			if(c != '\r')
				*p++ = '\r';
			*p = 0;
			if(send(d, buf) < 0)
				return Failure;
			m = readmsg(d, secs, substr);
			p = buf;
		}
	}
	return m;
}

/*
 *  apply a command type
 */
int
applyspecial(Dev *d, int index)
{
	char *cmd;

	cmd = d->t->commands[index];
	if(cmd == 0 && d->baset)
		cmd = d->baset->commands[index];
	if(cmd == 0)
		return Failure;

	return apply(d, cmd, 0, 2);
}

/*
 *  get modem into command mode if it isn't already
 */
int
attention(Dev *d)
{
	int i;

	for(i = 0; i < 2; i++){
		sleep(250);
		if(send(d, "+") < 0)
			continue;
		sleep(250);
		if(send(d, "+") < 0)
			continue;
		sleep(250);
		if(send(d, "+") < 0)
			continue;
		sleep(250);
		readmsg(d, 0, 0);
		if(apply(d, "ATZH0", 0, 2) == Ok)
			return Ok;
	}
	return Failure;
}

int portspeed[] = { 56000, 38400, 19200, 14400, 9600, 4800, 2400, 1200, 600, 300, 0 };

/*
 *  get the modem's type and speed
 */
char*
modemtype(Dev *d, int limit,  int fax)
{
	int *p;
	Type *t, *bt;
	char buf[28];

	d->t = typetab;
	d->baset = 0;

	/* assume we're at a good speed, try getting attention a few times */
	attention(d);

	/* find a common port rate */
	for(p = portspeed; *p; p++){
		if(*p > limit)
			continue;
		setspeed(d, *p);
		if(attention(d) == Ok)
			break;
	}
	if(*p == 0)
		return Eattn;
	d->speed = *p;
	if(verbose)
		syslog(0, LOGFILE, "port speed %d", *p);

	/*
	 *  basic Hayes commands everyone implements (we hope)
	 *	Q0 = report result codes
	 * 	V1 = full word result codes
	 *	E0 = don't echo commands
	 *	M1 = speaker on until on-line
	 *	S0=0 = autoanswer off
	 */
	if(apply(d, "ATQ0V1E0M1S0=0", 0, 2) != Ok)
		return Eattn;

	/* find modem type */
	for(t = typetab; t->name; t++){
		if(t->ident == 0 || t->response == 0)
			continue;
		if(apply(d, t->ident, t->response, 2) == Found)
			break;
		readmsg(d, 0, 0);
	}
	readmsg(d, 0, 0);
	if(t->name){
		d->t = t;
		if(t->basetype){
			for(bt = typetab; bt->name; bt++)
				if(strcmp(bt->name, t->basetype) == 0)
					break;
			if(bt->name)
				d->baset = bt;
		}
	}
	if(verbose)
		syslog(0, LOGFILE, "modem %s", d->t->name);

	/* try setting fax modes */
	d->fclass = 0;
	if(fax){
		/* set up fax parameters */
		if(applyspecial(d, Cfclass2) != Failure)
			d->fclass = 2;

		/* setup a source id */
		if(srcid){
			sprint(buf, "AT+FLID=\"%s\"", srcid);
			apply(d, buf, 0, 2);
		}

		/* allow both data and fax calls in */
		apply(d, "AT+FAA=1", 0, 2);
	} else
		applyspecial(d, Cfclass0);
	return 0;
}

/*
 *  a process to read input from a modem.
 */
void
monitor(Dev *d)
{
	int n;
	char *p;
	char file[256];
	int background;

	background = 0;
	d->ctl = d->data = -1;

	for(;;){
		lock(d);
		sprint(file, "%sctl", d->path);
		d->ctl = open(file, ORDWR);
		if(d->ctl < 0)
			error("opening ctl");
		d->data = open(d->path, ORDWR);
		if(d->data < 0)
			error("opening data");
		d->wp = d->rp = d->rbuf;
		unlock(d);

		if(!background){
			background = 1;
			switch(d->pid = rfork(RFPROC|RFMEM)){
			case -1:
				error("out of processes");
			case 0:
				break;
			default:
				return;
			}
		}

		/* wait for ring or off hook */
		while(d->open == 0){
			d->rp = d->rbuf;
			p = d->wp;
			n = read(d->data, p, 1);
			if(n < 1)
				continue;
			if(p < &d->rbuf[Nrbuf] - 2)
				d->wp++;
			if(*p == '\r' || *p == '\n'){
				*(p+1) = 0;
				if(verbose)
					syslog(0, LOGFILE, "<:-%s", d->rp);
				if(answer && strncmp(d->rp, "RING", 4) == 0){
					receiver(d);
					continue;
				}
				if(d->open == 0)
					d->wp = d->rbuf;
			}
		}

		/* shuttle bytes till on hook */
		while(d->open){
			if(d->wp >= d->rp)
				n = &d->rbuf[Nrbuf] - d->wp;
			else
				n = d->rp - d->wp - 1;
			if(n > 0)
				n = read(d->data, d->wp, n);
			else {
				read(d->data, file, sizeof(file));
				continue;
			}
			if(n < 0)
				break;
			lock(d);
			if(d->wp + n >= &d->rbuf[Nrbuf])
				d->wp = d->rbuf;
			else
				d->wp += n;
			serve(d);
			unlock(d);
		}

		close(d->ctl);
		close(d->data);
	}
}

/*
 *  get bytes input by monitor() (only routine that changes d->rp)
 */
int
getinput(Dev *d, char *buf, int n)
{
	char *p;
	int i;

	p = buf;
	while(n > 0){
		if(d->wp == d->rp)
			break;
		if(d->wp < d->rp)
			i = &d->rbuf[Nrbuf] - d->rp;
		else
			i = d->wp - d->rp;
		if(i > n)
			i = n;
		memmove(p, d->rp, i);
		if(d->rp + i == &d->rbuf[Nrbuf])
			d->rp = d->rbuf;
		else
			d->rp += i;
		n -= i;
		p += i;
	}
	return p - buf;
}

/*
 *  fulfill a read request (we assume d is locked)
 */
void
serve(Dev *d)
{
	Request *r;
	int n;
	Fcall rhdr;
	uchar *mdata;
	char *buf;

	mdata = malloc(messagesize);
	buf = malloc(messagesize-IOHDRSZ);

	for(;;){
		if(d->r == 0 || d->rp == d->wp)
			break;
		r = d->r;
		if(r->count > sizeof(buf))
			r->count = sizeof(buf);

		n = getinput(d, buf, r->count);
		if(n == 0)
			break;
		d->r = r->next;

		rhdr.type = Rread;
		rhdr.fid = r->fid->fid;
		rhdr.tag = r->tag;
		rhdr.data = buf;
		rhdr.count = n;
		n = convS2M(&rhdr, mdata, messagesize);
		if(write(mfd[1], mdata, n) != n)
			fprint(2, "telco: error writing\n");
		free(r);
	}
	free(mdata);
	free(buf);
}

/*
 *  dial a number
 */
char*
dialout(Dev *d, char *number)
{
	int i, m, compress, rateadjust, speed, fax;
	char *err;
	char *field[5];
	char dialstr[128];

	compress = Ok;
	rateadjust = Failure;
	speed = maxspeed;
	fax = Failure;

	m = getfields(number, field, 5, 1, "!");
	for(i = 1; i < m; i++){
		if(field[i][0] >= '0' && field[i][0] <= '9')
			speed = atoi(field[i]);
		else if(strcmp(field[i], "nocompress") == 0)
			compress = Failure;
		else if(strcmp(field[i], "fax") == 0)
			fax = Ok;
	}

	syslog(0, LOGFILE, "dialing %s speed=%d %s", number, speed, fax==Ok?"fax":"");
	
	err = modemtype(d, speed, fax == Ok);
	if(err)
		return err;

	/*
	 *  extented Hayes commands, meaning depends on modem (VGA all over again)
	 */
	if(fax != Ok){
		if(d->fclass != 0)
			applyspecial(d, Cfclass0);
		applyspecial(d, Cerrorcorrection);
		if(compress == Ok)
			compress = applyspecial(d, Ccompression);
		if(compress != Ok)
			rateadjust = applyspecial(d, Crateadjust);
	}
	applyspecial(d, Cflowctl);

	/* dialout */
	sprint(dialstr, "ATD%c%s\r", pulsed ? 'P' : 'T', number);
	if(send(d, dialstr) < 0)
		return Edial;

	if(fax == Ok)
		return 0;		/* fax sender worries about the rest */

	switch(readmsg(d, 120, 0)){
	case Success:
		break;
	default:
		return d->msgbuf;
	}

	/* change line rate if not compressing */
	if(rateadjust == Ok)
		setspeed(d, getspeed(d->msgbuf, d->speed));

	return 0;
}

/*
 *  start a receiving process
 */
void
receiver(Dev *d)
{
	int fd;
	char file[256];
	char *argv[8];
	int argc;
	int pfd[2];
	char *prog;

	pipe(pfd);
	switch(rfork(RFPROC|RFMEM|RFFDG|RFNAMEG)){
	case -1:
		return;
	case 0:
		fd = open("/srv/telco", ORDWR);
		if(fd < 0){
			syslog(0, LOGFILE, "can't open telco: %r");
			exits(0);
		}
		if(mount(fd, -1, "/net", MAFTER, "") < 0){
			syslog(0, LOGFILE, "can't mount: %r");
			exits(0);
		}
		close(fd);

		/* open connection through the file system interface */
		sprint(file, "/net/telco/%ld/data", d - dev);
		fd = open(file, ORDWR);
		if(fd < 0){
			syslog(0, LOGFILE, "can't open %s: %r", file);
			exits(0);
		}

		/* let parent continue */
		close(pfd[0]);
		close(pfd[1]);

		/* answer the phone and see what flavor call this is */
		prog = "/bin/service/telcodata";
		switch(apply(d, "ATA", "+FCON", 30)){
		case Success:
			break;
		case Found:
			prog = "/bin/service/telcofax";
			break;
		default:
			syslog(0, LOGFILE, "bad ATA response");
			exits(0);
		}

		/* fork a receiving process */
		dup(fd, 0);
		dup(fd, 1);
		close(fd);
		argc = 0;
		argv[argc++] = strrchr(prog, '/')+1;
		argv[argc++] = file;
		argv[argc++] = dev->t->name;
		argv[argc] = 0;
		exec(prog, argv);
		syslog(0, LOGFILE, "can't exec %s: %r\n", prog);
		exits(0);
	default:
		/* wait till child gets the device open */
		close(pfd[1]);
		read(pfd[0], file, 1);
		close(pfd[0]);
		break;
	}
}

/*
 *  hang up an connections in progress
 */
void
onhook(Dev *d)
{
	write(d->ctl, "d0", 2);
	write(d->ctl, "r0", 2);
	sleep(250);
	write(d->ctl, "r1", 2);
	write(d->ctl, "d1", 2);
	modemtype(d, maxspeed, 1);
}

/*
 *  read till we see a message or we time out
 */
int
readmsg(Dev *d, int secs, char *substr)
{
	ulong start;
	char *p;
	int i, len;
	Msg *pp;
	int found = 0;

	p = d->msgbuf;
	len = sizeof(d->msgbuf) - 1;
	for(start = time(0); time(0) <= start+secs;){
		if(len && d->rp == d->wp){
			sleep(100);
			continue;
		}
		i = getinput(d, p, 1);
		if(i == 0)
			continue;
		if(*p == '\n' || *p == '\r' || len == 0){
			*p = 0;
			if(verbose && p != d->msgbuf)
				syslog(0, LOGFILE, "<-%s", d->msgbuf);
			if(substr && strstr(d->msgbuf, substr))
				found = 1;
			for(pp = msgs; pp->text; pp++)
				if(strncmp(pp->text, d->msgbuf, strlen(pp->text))==0)
					return found ? Found : pp->type;
			start = time(0);
			p = d->msgbuf;
			len = sizeof(d->msgbuf) - 1;
			continue;
		}
		len--;
		p++;
	}
	strcpy(d->msgbuf, "No response from modem");
	return found ? Found : Noise;
}

/*
 *  get baud rate from a connect message
 */
int
getspeed(char *msg, int speed)
{
	char *p;
	int s;

	p = msg + sizeof("CONNECT") - 1;
	while(*p == ' ' || *p == '\t')
		p++;
	s = atoi(p);
	if(s <= 0)
		return speed;
	else
		return s;
}

/*
 *  set speed and RTS/CTS modem flow control
 */
void
setspeed(Dev *d, int baud)
{
	char buf[32];

	if(d->ctl < 0)
		return;
	sprint(buf, "b%d", baud);
	write(d->ctl, buf, strlen(buf));
	write(d->ctl, "m1", 2);
}