9p2.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	"all.h"

#define MSIZE	(MAXDAT+128)

static void
seterror(Fcall *ou, int err)
{

	if(0 <= err && err < MAXERR)
		ou->ename = errstring[err];
	else
		ou->ename = "unknown error";
}

static int
fsversion(Chan* chan, Fcall* f, Fcall* r)
{
	if(f->msize < MSIZE)
		r->msize = f->msize;
	else
		r->msize = MSIZE;
	/*
	 * Should check the '.' stuff here.
	 * What happens if Tversion has already been seen?
	 */
	if(strcmp(f->version, VERSION9P) == 0){
		r->version = VERSION9P;
		chan->msize = r->msize;
	}else
		r->version = "unknown";

	fileinit(chan);
	return 0;
}

char *keyspec = "proto=p9any role=server";

static int
fsauth(Chan *chan, Fcall *f, Fcall *r)
{
	int err, fd;
	char *aname;
	File *file;
	int afd;
	AuthRpc *rpc;

	err = 0;
	if(chan == cons.srvchan)
		return Eauthmsg;
	file = filep(chan, f->afid, 1);
	if(file == nil)
		return Efidinuse;

	/* forget any previous authentication */
	file->cuid = 0;

	if(access("/mnt/factotum", 0) < 0)
		if((fd = open("/srv/factotum", ORDWR)) >= 0)
			mount(fd, -1, "/mnt", MBEFORE, "");

	afd = open("/mnt/factotum/rpc", ORDWR);
	if(afd < 0){
		err = Esystem;
		goto out;
	}
	rpc = auth_allocrpc(afd);
	if(rpc == nil){
		close(afd);
		err = Esystem;
		goto out;
	}
	file->rpc = rpc;
	if(auth_rpc(rpc, "start", keyspec, strlen(keyspec)) != ARok){
		err = Esystem;
		goto out;
	}

	aname = f->aname;
	if(!aname[0])
		aname = "main";
	file->fs = fsstr(aname);
	if(file->fs == nil){
		err = Ebadspc;
		goto out;
	}
	file->uid = strtouid(f->uname);
	if(file->uid < 0){
		err = Ebadu;
		goto out;
	}
	file->qid.path = 0;
	file->qid.vers = 0;
	file->qid.type = QTAUTH;
	r->qid = file->qid;

out:
	if(file != nil){
		qunlock(file);
		if(err != 0)
			freefp(file);
	}
	return err;
}

int
authread(File *file, uchar *data, int count)
{
	AuthInfo *ai;
	AuthRpc *rpc;
	int rv;

	rpc = file->rpc;
	if(rpc == nil)
		return -1;

	rv = auth_rpc(rpc, "read", nil, 0);
	switch(rv){
	case ARdone:
		ai = auth_getinfo(rpc);
		if(ai == nil)
			return -1;
		if(chat)
			print("authread identifies user as %s\n", ai->cuid);
		file->cuid = strtouid(ai->cuid);
		auth_freeAI(ai);
		if(file->cuid == 0)
			return -1;
		if(chat)
			print("%s is a known user\n", ai->cuid);
		return 0;
	case ARok:
		if(count < rpc->narg)
			return -1;
		memmove(data, rpc->arg, rpc->narg);
		return rpc->narg;
	case ARphase:
		return -1;
	default:
		return -1;
	}
}

int
authwrite(File *file, uchar *data, int count)
{
	int ret;

	ret = auth_rpc(file->rpc, "write", data, count);
	if(ret != ARok)
		return -1;
	return count;
}

void
mkqid9p1(Qid9p1* qid9p1, Qid* qid)
{
	if(qid->path & 0xFFFFFFFF00000000LL)
		panic("mkqid9p1: path %lluX\n", qid->path);
	qid9p1->path = qid->path & 0xFFFFFFFF;
	if(qid->type & QTDIR)
		qid9p1->path |= QPDIR;
	qid9p1->version = qid->vers;
}

void
authfree(File *fp)
{
	if(fp->rpc != nil){
		close(fp->rpc->afd);
		free(fp->rpc);
		fp->rpc = nil;
	}
}

void
mkqid9p2(Qid* qid, Qid9p1* qid9p1, int mode)
{
	qid->path = (ulong)(qid9p1->path & ~QPDIR);
	qid->vers = qid9p1->version;
	qid->type = 0;
	if(mode & DDIR)
		qid->type |= QTDIR;
	if(mode & DAPND)
		qid->type |= QTAPPEND;
	if(mode & DLOCK)
		qid->type |= QTEXCL;
}

static int
checkattach(Chan *chan, File *afile, File *file, Filsys *fs)
{
	uchar buf[1];

	if(chan == cons.srvchan || chan == cons.chan)
		return 0;

	/* if no afile, this had better be none */
	if(afile == nil){
		if(file->uid == 0){
			if(!allownone && !chan->authed)
				return Eauth;
			return 0;
		}
		return Eauth;
	}

	/* otherwise, we'ld better have a usable cuid */
	if(!(afile->qid.type&QTAUTH))
		return Eauth;
	if(afile->uid != file->uid || afile->fs != fs)
		return Eauth;
	if(afile->cuid <= 0){
		if(authread(afile, buf, 0) != 0)
			return Eauth;
		if(afile->cuid <= 0)
			return Eauth;
	}
	file->uid = afile->cuid;

	/* once someone has authenticated on the channel, others can become none */
	chan->authed = 1;

	return 0;
}		

static int
fsattach(Chan* chan, Fcall* f, Fcall* r)
{
	char *aname;
	Iobuf *p;
	Dentry *d;
	File *file;
	File *afile;
	Filsys *fs;
	long raddr;
	int error, u;

	aname = f->aname;
	if(!aname[0])	/* default */
		aname = "main";
	p = nil;
	afile = filep(chan, f->afid, 0);
	file = filep(chan, f->fid, 1);
	if(file == nil){
		error = Efidinuse;
		goto out;
	}

	u = -1;
	if(chan != cons.chan){
		if(strcmp(f->uname, "adm") == 0){
			error = Eauth;
			goto out;
		}
		u = strtouid(f->uname);
		if(u < 0){
			error = Ebadu;
			goto out;
		}
	}
	file->uid = u;

	fs = fsstr(aname);
	if(fs == nil){
		error = Ebadspc;
		goto out;
	}

	if(error = checkattach(chan, afile, file, fs))
		goto out;

	raddr = getraddr(fs->dev);
	p = getbuf(fs->dev, raddr, Bread);
	d = getdir(p, 0);
	if(d == nil || checktag(p, Tdir, QPROOT) || !(d->mode & DALLOC)){
		error = Ealloc;
		goto out;
	}
	if(iaccess(file, d, DEXEC)){
		error = Eaccess;
		goto out;
	}
	if(file->uid == 0 && isro(fs->dev)) {
		/*
		 * 'none' not allowed on dump
		 */
		error = Eaccess;
		goto out;
	}
	accessdir(p, d, FREAD);
	mkqid(&file->qid, d, 1);
	file->fs = fs;
	file->addr = raddr;
	file->slot = 0;
	file->open = 0;
	freewp(file->wpath);
	file->wpath = 0;

	r->qid = file->qid;

//	if(cons.flags & attachflag)
//		print("9p2: attach %s %T to \"%s\" C%d\n",
//			chan->whoname, chan->whotime, fs->name, chan->chan);

out:
//	if((cons.flags & attachflag) && error)
//		print("9p2: attach %s %T SUCK EGGS --- %s\n",
//			f->uname, time(), errstr[error]);
	if(p != nil)
		putbuf(p);
	if(afile != nil)
		qunlock(afile);
	if(file != nil){
		qunlock(file);
		if(error)
			freefp(file);
	}

	return error;
}

static int
fsflush(Chan* chan, Fcall*, Fcall*)
{
	runlock(&chan->reflock);
	wlock(&chan->reflock);
	wunlock(&chan->reflock);
	rlock(&chan->reflock);

	return 0;
}

static void
clone(File* nfile, File* file)
{
	Wpath *wpath;

	nfile->qid = file->qid;

	lock(&wpathlock);
	nfile->wpath = file->wpath;
	for(wpath = nfile->wpath; wpath != nil; wpath = wpath->up)
		wpath->refs++;
	unlock(&wpathlock);

	nfile->fs = file->fs;
	nfile->addr = file->addr;
	nfile->slot = file->slot;
	nfile->uid = file->uid;
	nfile->cuid = 0;
	nfile->open = file->open & ~FREMOV;
}

static int
walkname(File* file, char* wname, Qid* wqid)
{
	Wpath *w;
	Iobuf *p, *p1;
	Dentry *d, *d1;
	int error, slot;
	long addr, qpath;

	p = p1 = nil;

	/*
	 * File must not have been opened for I/O by an open
	 * or create message and must represent a directory.
	 */
	if(file->open != 0){
		error = Emode;
		goto out;
	}

	p = getbuf(file->fs->dev, file->addr, Bread);
	if(p == nil || checktag(p, Tdir, QPNONE)){
		error = Edir1;
		goto out;
	}
	if((d = getdir(p, file->slot)) == nil || !(d->mode & DALLOC)){
		error = Ealloc;
		goto out;
	}
	if(!(d->mode & DDIR)){
		error = Edir1;
		goto out;
	}
	if(error = mkqidcmp(&file->qid, d))
		goto out;

	/*
	 * For walked elements the implied user must
	 * have permission to search the directory.
	 */
	if(file->cp != cons.chan && iaccess(file, d, DEXEC)){
		error = Eaccess;
		goto out;
	}
	accessdir(p, d, FREAD);

	if(strcmp(wname, ".") == 0){
setdot:
		if(wqid != nil)
			*wqid = file->qid;
		goto out;
	}
	if(strcmp(wname, "..") == 0){
		if(file->wpath == 0)
			goto setdot;
		putbuf(p);
		p = nil;
		addr = file->wpath->addr;
		slot = file->wpath->slot;
		p1 = getbuf(file->fs->dev, addr, Bread);
		if(p1 == nil || checktag(p1, Tdir, QPNONE)){
			error = Edir1;
			goto out;
		}
		if((d1 = getdir(p1, slot)) == nil || !(d1->mode & DALLOC)){
			error = Ephase;
			goto out;
		}
		lock(&wpathlock);
		file->wpath->refs--;
		file->wpath = file->wpath->up;
		unlock(&wpathlock);
		goto found;
	}

	for(addr = 0; ; addr++){
		if(p == nil){
			p = getbuf(file->fs->dev, file->addr, Bread);
			if(p == nil || checktag(p, Tdir, QPNONE)){
				error = Ealloc;
				goto out;
			}
			d = getdir(p, file->slot);
			if(d == nil ||  !(d->mode & DALLOC)){
				error = Ealloc;
				goto out;
			}
		}
		qpath = d->qid.path;
		p1 = dnodebuf1(p, d, addr, 0);
		p = nil;
		if(p1 == nil || checktag(p1, Tdir, qpath)){
			error = Eentry;
			goto out;
		}
		for(slot = 0; slot < DIRPERBUF; slot++){
			d1 = getdir(p1, slot);
			if(!(d1->mode & DALLOC))
				continue;
			if(strncmp(wname, d1->name, NAMELEN) != 0)
				continue;
			/*
			 * update walk path
			 */
			if((w = newwp()) == nil){
				error = Ewalk;
				goto out;
			}
			w->addr = file->addr;
			w->slot = file->slot;
			w->up = file->wpath;
			file->wpath = w;
			slot += DIRPERBUF*addr;
			goto found;
		}
		putbuf(p1);
		p1 = nil;
	}

found:
	file->addr = p1->addr;
	mkqid(&file->qid, d1, 1);
	putbuf(p1);
	p1 = nil;
	file->slot = slot;
	if(wqid != nil)
		*wqid = file->qid;

out:
	if(p1 != nil)
		putbuf(p1);
	if(p != nil)
		putbuf(p);

	return error;
}

static int
fswalk(Chan* chan, Fcall* f, Fcall* r)
{
	int error, nwname;
	File *file, *nfile, tfile;

	/*
	 * The file identified by f->fid must be valid in the
	 * current session and must not have been opened for I/O
	 * by an open or create message.
	 */
	if((file = filep(chan, f->fid, 0)) == nil)
		return Efid;
	if(file->open != 0){
		qunlock(file);
		return Emode;
	}

	/*
	 * If newfid is not the same as fid, allocate a new file;
	 * a side effect is checking newfid is not already in use (error);
	 * if there are no names to walk this will be equivalent to a
	 * simple 'clone' operation.
	 * Otherwise, fid and newfid are the same and if there are names
	 * to walk make a copy of 'file' to be used during the walk as
	 * 'file' must only be updated on success.
	 * Finally, it's a no-op if newfid is the same as fid and f->nwname
	 * is 0.
	 */
	r->nwqid = 0;
	if(f->newfid != f->fid){
		if((nfile = filep(chan, f->newfid, 1)) == nil){
			qunlock(file);
			return Efidinuse;
		}
	}
	else if(f->nwname != 0){
		nfile = &tfile;
		memset(nfile, 0, sizeof(File));
		nfile->cp = chan;
		nfile->fid = ~0;
	}
	else{
		qunlock(file);
		return 0;
	}
	clone(nfile, file);

	/*
	 * Should check name is not too long.
	 */
	error = 0;
	for(nwname = 0; nwname < f->nwname; nwname++){
		error = walkname(nfile, f->wname[nwname], &r->wqid[r->nwqid]);
		if(error != 0 || ++r->nwqid >= MAXDAT/sizeof(Qid))
			break;
	}

	if(f->nwname == 0){
		/*
		 * Newfid must be different to fid (see above)
		 * so this is a simple 'clone' operation - there's
		 * nothing to do except unlock unless there's
		 * an error.
		 */
		if(error){
			freewp(nfile->wpath);
			qunlock(nfile);
			freefp(nfile);
		}
		else
			qunlock(nfile);
	}
	else if(r->nwqid < f->nwname){
		/*
		 * Didn't walk all elements, 'clunk' nfile
		 * and leave 'file' alone.
		 * Clear error if some of the elements were
		 * walked OK.
		 */
		freewp(nfile->wpath);
		if(nfile != &tfile){
			qunlock(nfile);
			freefp(nfile);
		}
		if(r->nwqid != 0)
			error = 0;
	}
	else{
		/*
		 * Walked all elements. If newfid is the same
		 * as fid must update 'file' from the temporary
		 * copy used during the walk.
		 * Otherwise just unlock (when using tfile there's
		 * no need to unlock as it's a local).
		 */
		if(nfile == &tfile){
			file->qid = nfile->qid;
			freewp(file->wpath);
			file->wpath = nfile->wpath;
			file->addr = nfile->addr;
			file->slot = nfile->slot;
		}
		else
			qunlock(nfile);
	}
	qunlock(file);

	return error;
}

static int
fsopen(Chan* chan, Fcall* f, Fcall* r)
{
	Iobuf *p;
	Dentry *d;
	File *file;
	Tlock *t;
	Qid qid;
	int error, ro, fmod, wok;

	wok = 0;
	p = nil;

	if(chan == cons.chan || writeallow)
		wok = 1;

	if((file = filep(chan, f->fid, 0)) == nil){
		error = Efid;
		goto out;
	}