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

#include <u.h>
#include <libc.h>
#include <auth.h>
#include <fcall.h>

#define LOGFILE "telco"

/*
 * Rather than reading /adm/users, which is a lot of work for
 * a toy progdev, we assume all groups have the form
 *	NNN:user:user:
 * meaning that each user is the leader of his own group.
 */

enum
{
	OPERM	= 0x3,		/* mask of all permission types in open mode */
	Ndev	= 8,
	Nreq	= (Ndev*3)/2,
	Nrbuf	= 32*1024,
};

typedef struct Fid Fid;
typedef struct Dev Dev;
typedef struct Request Request;
typedef struct Type Type;

struct Fid
{
	Qid	qid;
	short	busy;
	short	open;
	int	fid;
	Fid	*next;
	char	*user;
};

struct Request
{
	Request	*next;

	Fid	*fid;
	ulong	tag;
	int	count;
	int	flushed;
};

struct Dev
{
	Lock;

	/* device state */
	int	ctl;		/* control fd */
	int	data;		/* data fd */
	char	*path;		/* to device */
	Type	*t;
	Type	*baset;
	int	speed;
	int	fclass;

	/* fs emulation */
	int	open;
	long	perm;
	char	*name;
	char	*user;
	char	msgbuf[128];
	Request	*r;
	Request *rlast;

	/* input reader */
	int	monitoring;	/* monitor pid */
	char	rbuf[Nrbuf];
	char	*rp;
	char	*wp;
	long	pid;
};

enum
{
	Devmask=	(Ndev-1)<<8,
	
	Qlvl1=		0,
	Qlvl2=		1,
	Qclone=		2,
	Qlvl3=		3,
	Qdata=		4,
	Qctl=		5,

	Pexec =		1,
	Pwrite = 	2,
	Pread = 	4,
	Pother = 	1,
	Pgroup = 	8,
	Powner =	64,
};

char *names[] =
{
[Qlvl1]		"/",
[Qlvl2]		"telco",
[Qclone]	"clone",
[Qlvl3]		"",
[Qdata]		"data",
[Qctl]		"ctl",
};

#define DEV(q) ((((ulong)(q).path)&Devmask)>>8)
#define TYPE(q) (((ulong)(q).path)&((1<<8)-1))
#define MKQID(t, i) ((((i)<<8)&Devmask) | (t))

enum
{
	/*
	 *  modem specific commands
	 */
	Cerrorcorrection	= 0,	/* error correction */
	Ccompression,			/* compression */
	Cflowctl,			/* CTS/RTS */
	Crateadjust,			/* follow line speed */
	Cfclass2,			/* set up for fax */
	Cfclass0,			/* set up for data */
	Ncommand,
};

struct Type
{
	char	*name;
	char	*ident;		/* inquire request */
	char	*response;	/* inquire response (strstr) */
	char	*basetype;	/* name of base type */

	char	*commands[Ncommand];
};

/*
 *  Fax setup summary
 *
 *	FCLASS=2	- set to service class 2, i.e., one where the fax handles timing 
 *	FTBC=0		- ???
 *	FREL=1		- ???
 *	FCQ=1		- receive copy quality checking enabled
 *	FBOR=1		- set reversed bit order for phase C data
 *	FCR=1		- the DCE can receive message data, bit 10 in the DIS or
 *			  DTC frame will be set
 *	FDIS=,3		- limit com speed to 9600 baud
 */

Type typetab[] =
{
 {	"Rockwell",		0,	0,	0,
	"AT\\N7",	/* auto reliable (V.42, fall back to MNP, to none) */
	"AT%C1\\J0",	/* negotiate for compression, don't change port baud rate */
	"AT\\Q3",	/* CTS/RTS flow control */
 	"AT\\J1",
	"AT+FCLASS=2\rAT+FCR=1\r",
	"AT+FCLASS=0",
 },

 {	"ATT2400",	"ATI9",	"E2400",	"Rockwell",
	"AT\\N3",	/* auto reliable (MNP, fall back to none) */
	0,	
	0,
	0,
	0,
 	0,
 },

 {	"ATT14400",	"ATI9",	"E14400",	"Rockwell",
	0,
	0,	
	0,
	0,
	0,
 	0,
 },

 {	"MT1432",	"ATI2",	"MT1432",	0,
	"AT&E1",	/* auto reliable (V.42, fall back to none) */
	"AT&E15$BA0",	/* negotiate for compression */
	"AT&E4",	/* CTS/RTS flow control */
	"AT$BA1",	/* don't change port baud rate */
	"AT+FCLASS=2\rAT+FTBC=0\rAT+FREL=1\rAT+FCQ=1\rAT+FBOR=1\rAT+FCR=1\rAT+FDIS=,3",
	"AT+FCLASS=0",
 },

 {	"MT2834",	"ATI2",	"MT2834",	"MT1432",
	0,
	0,
	0,
	0,
 	"AT+FCLASS=2\rAT+FTBC=0\rAT+FREL=1\rAT+FCQ=1\rAT+FBOR=1\rAT+FCR=1",
	0,
 },

 {	"VOCAL",	"ATI6",	"144DPL+FAX",	"Rockwell",
	"AT\\N3",	/* auto reliable (V.42, fall back to MNP, fall back to none) */
	"AT%C3\\J0",	/* negotiate for compression, don't change port baud rate */	
	0,
	0,
 	"AT+FCLASS=2\rAT+FTBC=0\rAT+FREL=1\rAT+FCQ=1\rAT+FBOR=1\rAT+FCR=1",
	"AT+FCLASS=0",
 },

 { 0, },
};

/*
 *  modem return codes
 */
enum
{
	Ok,
	Success,
	Failure,
	Noise,
	Found,
};

/*
 *  modem return messages
 */
typedef struct Msg	Msg;
struct Msg
{
	char	*text;
	int	type;
};

Msg msgs[] =
{
	{ "OK",			Ok, },
	{ "NO CARRIER", 	Failure, },
	{ "ERROR",		Failure, },
	{ "NO DIALTONE",	Failure, },
	{ "BUSY",		Failure, },
	{ "NO ANSWER",		Failure, },
	{ "CONNECT",		Success, },
	{ 0,			0 },
};

Fid	*fids;
Dev	*dev;
int	ndev;
int	mfd[2];
char	*user;
uchar	mdata[8192+IOHDRSZ];
int	messagesize = sizeof mdata;
Fcall	thdr;
Fcall	rhdr;
char	errbuf[ERRMAX];
uchar	statbuf[STATMAX];
int	pulsed;
int	verbose;
int	maxspeed = 56000;
char	*srcid = "plan9";
int	answer = 1;

Fid	*newfid(int);
int	devstat(Dir*, uchar*, int);
int	devgen(Qid, int, Dir*, uchar*, int);
void	error(char*);
void	io(void);
void	*erealloc(void*, ulong);
void	*emalloc(ulong);
void	usage(void);
int	perm(Fid*, Dev*, int);
void	setspeed(Dev*, int);
int	getspeed(char*, int);
char	*dialout(Dev*, char*);
void	onhook(Dev*);
int	readmsg(Dev*, int, char*);
void	monitor(Dev*);
int	getinput(Dev*, char*, int);
void	serve(Dev*);
void	receiver(Dev*);
char*	modemtype(Dev*, int, int);


char	*rflush(Fid*), *rversion(Fid*),
	*rattach(Fid*), *rauth(Fid*), *rwalk(Fid*),
	*ropen(Fid*), *rcreate(Fid*),
	*rread(Fid*), *rwrite(Fid*), *rclunk(Fid*),
	*rremove(Fid*), *rstat(Fid*), *rwstat(Fid*);

char 	*(*fcalls[])(Fid*) = {
	[Tflush]	rflush,
	[Tversion]	rversion,
	[Tattach]	rattach,
	[Tauth]	rauth,
	[Twalk]		rwalk,
	[Topen]		ropen,
	[Tcreate]	rcreate,
	[Tread]		rread,
	[Twrite]	rwrite,
	[Tclunk]	rclunk,
	[Tremove]	rremove,
	[Tstat]		rstat,
	[Twstat]	rwstat,
};

char	Eperm[] =	"permission denied";
char	Enotdir[] =	"not a directory";
char	Enotexist[] =	"file does not exist";
char	Ebadaddr[] = 	"bad address";
char	Eattn[] = 	"can't get modem's attention";
char	Edial[] = 	"can't dial";
char	Enoauth[] =	"telco: authentication not required";
char	Eisopen[] = 	"file already open for I/O";
char	Enodev[] = 	"no free modems";
char	Enostream[] =	"stream closed prematurely";

void
usage(void)
{
	fprint(2, "usage: %s [-vp] [-i srcid] dev ...\n", argv0);
	exits("usage");
}

void
notifyf(void *a, char *s)
{
	USED(a);
	if(strncmp(s, "interrupt", 9) == 0)
		noted(NCONT);
	noted(NDFLT);
}

void
main(int argc, char *argv[])
{
	int p[2];
	int fd;
	char buf[10];
	Dev *d;

	ARGBEGIN{
	case 'p':
		pulsed = 1;
		break;
	case 'v':
		verbose = 1;
		break;
	case 'i':
		srcid = ARGF();
		break;
	case 's':
		maxspeed = atoi(ARGF());
		break;
	case 'n':
		answer = 0;
		break;
	default:
		usage();
	}ARGEND

	if(argc == 0)
		usage();
	if(argc > Ndev)
		argc = Ndev;

	if(pipe(p) < 0)
		error("pipe failed");

	notify(notifyf);
	fmtinstall('F', fcallfmt);
	user = getuser();

	switch(rfork(RFFDG|RFPROC|RFREND|RFNOTEG)){
	case -1:
		error("fork");
	case 0:
		close(p[1]);
		mfd[0] = mfd[1] = p[0];
		break;
	default:
		close(p[0]);
		fd = create("/srv/telco", OWRITE, 0666);
		if(fd < 0)
			error("create of /srv/telco failed");
		sprint(buf, "%d", p[1]);
		if(write(fd, buf, strlen(buf)) < 0)
			error("writing /srv/telco");
		close(fd);
		if(mount(p[1], -1, "/net", MBEFORE, "") < 0)
			error("mount failed");
		exits(0);
	}

	dev = mallocz(argc*sizeof(Dev), 1);
	for(ndev = 0; ndev < argc; ndev++){
		d = &dev[ndev];
		d->path = argv[ndev];
		d->rp = d->wp = d->rbuf;
		monitor(d);
		d->open++;
		onhook(d);
		d->open--;
	}

	io();
}

/*
 *  generate a stat structure for a qid
 */
int
devstat(Dir *dir, uchar *buf, int nbuf)
{
	Dev *d;
	int t;
	static char tmp[10][32];
	static int ntmp;

	t = TYPE(dir->qid);
	if(t != Qlvl3)
		dir->name = names[t];
	else{
		dir->name = tmp[ntmp % nelem(tmp)];
		sprint(dir->name, "%lud", DEV(dir->qid));
		ntmp++;
	}
	dir->mode = 0755;
	dir->uid = user;
	dir->gid = user;
	dir->muid = user;
	if(t >= Qlvl3){
		d = &dev[DEV(dir->qid)];
		if(d->open){
			dir->mode = d->perm;
			dir->uid = d->user;
		}
	}
	if(dir->qid.type & QTDIR)
		dir->mode |= DMDIR;
	if(t == Qdata){
		d = &dev[DEV(dir->qid)];
		dir->length = d->wp - d->rp;
		if(dir->length < 0)
			dir->length += Nrbuf;
	} else
		dir->length = 0;
	dir->atime = time(0);
	dir->mtime = dir->atime;
	if(buf)
		return convD2M(dir, buf, nbuf);
	return 0;
}

/*
 *  enumerate file's we can walk to from q
 */
int
devgen(Qid q, int i, Dir *d, uchar *buf, int nbuf)
{
	static ulong v;

	d->qid.vers = v++;
	switch(TYPE(q)){
	case Qlvl1:
		if(i != 0)
			return -1;
		d->qid.type = QTDIR;
		d->qid.path = Qlvl2;
		break;
	case Qlvl2:
		switch(i){
		case -1:
			d->qid.type = QTDIR;
			d->qid.path = Qlvl1;
			break;
		case 0:
			d->qid.type = QTFILE;
			d->qid.path = Qclone;
			break;
		default:
			if(i > ndev)
				return -1;
			d->qid.type = QTDIR;
			d->qid.path = MKQID(Qlvl3, i-1);
			break;
		}
		break;
	case Qlvl3:
		switch(i){
		case -1:
			d->qid.type = QTDIR;
			d->qid.path = Qlvl2;
			break;
		case 0:
			d->qid.type = QTFILE;
			d->qid.path = MKQID(Qdata, DEV(q));
			break;
		case 1:
			d->qid.type = QTFILE;
			d->qid.path = MKQID(Qctl, DEV(q));
			break;
		default:
			return -1;
		}
		break;
	default:
		return -1;
	}
	return devstat(d, buf, nbuf);
}

char*
rversion(Fid *)
{
	Fid *f;

	for(f = fids; f; f = f->next)
		if(f->busy)
			rclunk(f);

	if(thdr.msize < 256)
		return "version: message size too small";
	messagesize = thdr.msize;
	if(messagesize > sizeof mdata)
		messagesize = sizeof mdata;
	rhdr.msize = messagesize;
	if(strncmp(thdr.version, "9P2000", 6) != 0)
		return "unrecognized 9P version";
	rhdr.version = "9P2000";
	return 0;
}

char*
rflush(Fid *f)
{
	Request *r, **l;
	Dev *d;

	USED(f);
	for(d = dev; d < &dev[ndev]; d++){
		lock(d);
		for(l = &d->r; r = *l; l = &r->next)
			if(r->tag == thdr.oldtag){
				*l = r->next;
				free(r);
				break;
			}
		unlock(d);
	}
	return 0;
}

char *
rauth(Fid *f)
{
	USED(f);
	return Enoauth;
}

char*
rattach(Fid *f)
{
	f->busy = 1;
	f->qid.type = QTDIR;
	f->qid.path = Qlvl1;
	f->qid.vers = 0;
	rhdr.qid = f->qid;
	if(thdr.uname[0])
		f->user = strdup(thdr.uname);
	else
		f->user = "none";
	return 0;
}

char*
rwalk(Fid *f)
{
	Fid *nf;
	int i, nqid;
	char *name, *err;
	Dir dir;
	Qid q;

	nf = nil;
	if(thdr.fid != thdr.newfid){
		if(f->open)
			return Eisopen;
		if(f->busy == 0)
			return Enotexist;
		nf = newfid(thdr.newfid);
		nf->busy = 1;
		nf->open = 0;
		nf->qid = f->qid;
		nf->user = strdup(f->user);
		f = nf;	/* walk f */
	}

	err = nil;
	dir.qid = f->qid;
	nqid = 0;
	if(thdr.nwname > 0){
		for(; nqid < thdr.nwname; nqid++) {
			if((dir.qid.type & QTDIR) == 0){
				err = Enotdir;
				break;
			}
			name = thdr.wname[nqid];
			if(strcmp(name, ".") == 0){
				/* nothing to do */
			}else if(strcmp(name, "..") == 0) {
				if(devgen(f->qid, -1, &dir, 0, 0) < 0)
					break;
			}
			else{
				q = dir.qid;
				for(i = 0;; i++){
					if(devgen(q, i, &dir, 0, 0) < 0)
						goto Out;
					if(strcmp(name, dir.name) == 0)
						break;
				}
			}
			rhdr.wqid[nqid] = dir.qid;
		}
    Out:
		if(nqid == 0 && err == nil)
			err = Enotexist;
		if(nf != nil && thdr.fid != thdr.newfid && nqid < thdr.nwname)
			rclunk(nf);
	}

	rhdr.nwqid = nqid;
	if(nqid > 0 && nqid == thdr.nwname)
		f->qid = dir.qid;
	return err;
}

char *
ropen(Fid *f)
{
	Dev *d;
	int mode, t;

	if(f->open)
		return Eisopen;
	mode = thdr.mode;
	mode &= OPERM;
	if(f->qid.type & QTDIR){
		if(mode != OREAD)
			return Eperm;
		rhdr.qid = f->qid;
		return 0;
	}
	if(mode==OEXEC)
		return Eperm;
	t = TYPE(f->qid);
	if(t == Qclone){
		for(d = dev; d < &dev[ndev]; d++)
			if(d->open == 0)
				break;
		if(d == &dev[ndev])
			return Enodev;
		f->qid.path = MKQID(Qctl, d-dev);
		t = Qctl;
	}
	switch(t){
	case Qdata:
	case Qctl:
		d = &dev[DEV(f->qid)];
		if(d->open == 0){
			d->user = strdup(f->user);
			d->perm = 0660;
		}else {
			if(mode==OWRITE || mode==ORDWR)
				if(!perm(f, d, Pwrite))
					return Eperm;
			if(mode==OREAD || mode==ORDWR)
				if(!perm(f, d, Pread))
					return Eperm;
		}
		d->open++;
		break;
	}
	rhdr.qid = f->qid;
	rhdr.iounit = messagesize - IOHDRSZ;
	f->open = 1;
	return 0;
}

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

/*
 *  intercept a note
 */
void
takeanote(void *u, char *note)
{
	USED(u);
	if(strstr(note, "flushed"))
		noted(NCONT);
	noted(NDFLT);
}

char*
rread(Fid *f)
{
	char *buf;
	long off, start;
	int i, m, n, cnt, t;
	Dir dir;
	char num[32];
	Dev *d;
	Request *r;

	n = 0;
	rhdr.count = 0;
	off = thdr.offset;
	cnt = thdr.count;
	buf = rhdr.data;
	t = TYPE(f->qid);
	switch(t){
	default:
		start = 0;
		for(i = 0; n < cnt; i++){
			m = devgen(f->qid, i, &dir, (uchar*)buf+n, cnt-n);
			if(m <= BIT16SZ)
				break;
			if(start >= off)
				n += m;
			start += m;
		}
		break;
	case Qctl:
		i = sprint(num, "%lud", DEV(f->qid));
		if(off < i){
			n = cnt;
			if(off + n > i)
				n = i - off;
			memmove(buf, num + off, n);
		} else
			n = 0;
		break;
	case Qdata:
		d = &dev[DEV(f->qid)];
		r = mallocz(sizeof(Request), 1);
		r->tag = thdr.tag;
		r->count = thdr.count;
		r->fid = f;
		r->flushed = 0;
		lock(d);
		if(d->r)
			d->rlast->next = r;
		else
			d->r = r;
		d->rlast = r;
		serve(d);
		unlock(d);
		return "";
	}
	rhdr.count = n;
	return 0;
}

char *cmsg = "connect ";
int clen;

char*
rwrite(Fid *f)
{
	Dev *d;
	ulong off;
	int cnt;
	char *cp;
	char buf[64];

	off = thdr.offset;
	cnt = thdr.count;
	switch(TYPE(f->qid)){