u9fs.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

/* already in plan9.h #include <sys/types.h> *//* for struct passwd, struct group, struct stat ... */
/* plan9.h is first to get the large file support definitions as early as possible */
#include <plan9.h>
#include <sys/stat.h>	/* for stat, umask */
#include <stdlib.h>	/* for malloc */
#include <string.h>	/* for strcpy, memmove */
#include <pwd.h>	/* for getpwnam, getpwuid */
#include <grp.h>	/* for getgrnam, getgrgid */
#include <unistd.h>	/* for gethostname, pread, pwrite, read, write */
#include <utime.h>	/* for utime */
#include <dirent.h>	/* for readdir */
#include <errno.h>	/* for errno */
#include <stdio.h>	/* for remove [sic] */
#include <fcntl.h>	/* for O_RDONLY, etc. */

#include <sys/socket.h>	/* various networking crud */
#include <netinet/in.h>
#include <netdb.h>

#include <fcall.h>
#include <oldfcall.h>
#include <u9fs.h>

/* #ifndef because can be given in makefile */
#ifndef DEFAULTLOG
#define DEFAULTLOG "/tmp/u9fs.log"
#endif

char *logfile = DEFAULTLOG;

#define S_ISSPECIAL(m) (S_ISCHR(m) || S_ISBLK(m) || S_ISFIFO(m))

enum {
	Tdot = 1,
	Tdotdot
};

enum {
	P9P1,
	P9P2000
};

typedef struct User User;
struct User {
	int id;
	gid_t defaultgid;
	char *name;
	char **mem;	/* group members */
	int nmem;
	User *next;
};

struct Fid {
	int fid;
	char *path;
	struct stat st;
	User *u;
	int omode;
	DIR *dir;
	int diroffset;
	int fd;
	struct dirent *dirent;
	Fid *next;
	Fid *prev;
	int auth;
	void *authmagic;
};

void*	emalloc(size_t);
void*	erealloc(void*, size_t);
char*	estrdup(char*);
char*	estrpath(char*, char*);
void	sysfatal(char*, ...);
int	okuser(char*);

void	rversion(Fcall*, Fcall*);
void	rauth(Fcall*, Fcall*);
void	rattach(Fcall*, Fcall*);
void	rflush(Fcall*, Fcall*);
void	rclone(Fcall*, Fcall*);
void	rwalk(Fcall*, Fcall*);
void	ropen(Fcall*, Fcall*);
void	rcreate(Fcall*, Fcall*);
void	rread(Fcall*, Fcall*);
void	rwrite(Fcall*, Fcall*);
void	rclunk(Fcall*, Fcall*);
void	rstat(Fcall*, Fcall*);
void	rwstat(Fcall*, Fcall*);
void	rclwalk(Fcall*, Fcall*);
void	rremove(Fcall*, Fcall*);

User*	uname2user(char*);
User*	gname2user(char*);
User*	uid2user(int);
User*	gid2user(int);

Fid*	newfid(int, char**);
Fid*	oldfidex(int, int, char**);
Fid*	oldfid(int, char**);
int	fidstat(Fid*, char**);
void	freefid(Fid*);

int	userchange(User*, char**);
int	userwalk(User*, char**, char*, Qid*, char**);
int	useropen(Fid*, int, char**);
int	usercreate(Fid*, char*, int, long, char**);
int	userremove(Fid*, char**);
int	userperm(User*, char*, int, int);
int	useringroup(User*, User*);

Qid	stat2qid(struct stat*);

void	getfcallold(int, Fcall*, int);
void	putfcallold(int, Fcall*);

char	Eauth[] =	"authentication failed";
char	Ebadfid[] =	"fid unknown or out of range";
char	Ebadoffset[] =	"bad offset in directory read";
char	Ebadusefid[] =	"bad use of fid";
char	Edirchange[] =	"wstat can't convert between files and directories";
char	Eexist[] =	"file or directory already exists";
char	Efidactive[] =	"fid already in use";
char	Enotdir[] =	"not a directory";
char	Enotingroup[] =	"not a member of proposed group";
char	Enotowner[] = 	"only owner can change group in wstat";
char	Eperm[] =	"permission denied";
char	Especial0[] =	"already attached without access to special files";
char	Especial1[] =	"already attached with access to special files";
char	Especial[] =	"no access to special file";
char	Etoolarge[] =	"i/o count too large";
char	Eunknowngroup[] = "unknown group";
char	Eunknownuser[] = "unknown user";
char	Ewstatbuffer[] = "bogus wstat buffer";

ulong	msize = IOHDRSZ+8192;
uchar*	rxbuf;
uchar*	txbuf;
void*	databuf;
int	connected;
int	devallowed;
char*	autharg;
char*	defaultuser;
char	hostname[256];
char	remotehostname[256];
int	chatty9p = 0;
int	network = 1;
int	old9p = -1;
int	authed;
User*	none;

Auth *authmethods[] = {	/* first is default */
	&authrhosts,
	&authp9any,
	&authnone,
};

Auth *auth;

void
getfcallnew(int fd, Fcall *fc, int have)
{
	int len;

	if(have > BIT32SZ)
		sysfatal("cannot happen");

	if(have < BIT32SZ && readn(fd, rxbuf+have, BIT32SZ-have) != BIT32SZ-have)
		sysfatal("couldn't read message");

	len = GBIT32(rxbuf);
	if(len <= BIT32SZ)
		sysfatal("bogus message");

	len -= BIT32SZ;
	if(readn(fd, rxbuf+BIT32SZ, len) != len)
		sysfatal("short message");

	if(convM2S(rxbuf, len+BIT32SZ, fc) != len+BIT32SZ)
		sysfatal("badly sized message type %d", rxbuf[0]);
}

void
getfcallold(int fd, Fcall *fc, int have)
{
	int len, n;

	if(have > 3)
		sysfatal("cannot happen");

	if(have < 3 && readn(fd, rxbuf, 3-have) != 3-have)
		sysfatal("couldn't read message");

	len = oldhdrsize(rxbuf[0]);
	if(len < 3)
		sysfatal("bad message %d", rxbuf[0]);
	if(len > 3 && readn(fd, rxbuf+3, len-3) != len-3)
		sysfatal("couldn't read message");

	n = iosize(rxbuf);
	if(readn(fd, rxbuf+len, n) != n)
		sysfatal("couldn't read message");
	len += n;

	if(convM2Sold(rxbuf, len, fc) != len)
		sysfatal("badly sized message type %d", rxbuf[0]);
}

void
putfcallnew(int wfd, Fcall *tx)
{
	uint n;

	if((n = convS2M(tx, txbuf, msize)) == 0)
		sysfatal("couldn't format message type %d", tx->type);
	if(write(wfd, txbuf, n) != n)
		sysfatal("couldn't send message");
}

void
putfcallold(int wfd, Fcall *tx)
{
	uint n;

	if((n = convS2Mold(tx, txbuf, msize)) == 0)
		sysfatal("couldn't format message type %d", tx->type);
	if(write(wfd, txbuf, n) != n)
		sysfatal("couldn't send message");
}

void
getfcall(int fd, Fcall *fc)
{
	if(old9p == 1){
		getfcallold(fd, fc, 0);
		return;
	}
	if(old9p == 0){
		getfcallnew(fd, fc, 0);
		return;
	}

	/* auto-detect */
	if(readn(fd, rxbuf, 3) != 3)
		sysfatal("couldn't read message");

	/* is it an old (9P1) message? */
	if(50 <= rxbuf[0] && rxbuf[0] <= 87 && (rxbuf[0]&1)==0 && GBIT16(rxbuf+1) == 0xFFFF){
		old9p = 1;
		getfcallold(fd, fc, 3);
		return;
	}

	getfcallnew(fd, fc, 3);
	old9p = 0;
}

void
seterror(Fcall *f, char *error)
{
	f->type = Rerror;
	f->ename = error ? error : "programmer error";
}

int
isowner(User *u, Fid *f)
{
	return u->id == f->st.st_uid;
}



void
serve(int rfd, int wfd)
{
	Fcall rx, tx;

	for(;;){
		getfcall(rfd, &rx);

		if(chatty9p)
			fprint(2, "<- %F\n", &rx);

		memset(&tx, 0, sizeof tx);
		tx.type = rx.type+1;
		tx.tag = rx.tag;
		switch(rx.type){
		case Tflush:
			break;
		case Tversion:
			rversion(&rx, &tx);
			break;
		case Tauth:
			rauth(&rx, &tx);
			break;
		case Tattach:
			rattach(&rx, &tx);
			break;
		case Twalk:
			rwalk(&rx, &tx);
			break;
		case Tstat:
			tx.stat = databuf;
			rstat(&rx, &tx);
			break;
		case Twstat:
			rwstat(&rx, &tx);
			break;
		case Topen:
			ropen(&rx, &tx);
			break;
		case Tcreate:
			rcreate(&rx, &tx);
			break;
		case Tread:
			tx.data = databuf;
			rread(&rx, &tx);
			break;
		case Twrite:
			rwrite(&rx, &tx);
			break;
		case Tclunk:
			rclunk(&rx, &tx);
			break;
		case Tremove:
			rremove(&rx, &tx);
			break;
		default:
			fprint(2, "unknown message %F\n", &rx);
			seterror(&tx, "bad message");
			break;
		}

		if(chatty9p)
			fprint(2, "-> %F\n", &tx);

		(old9p ? putfcallold : putfcallnew)(wfd, &tx);
	}
}

void
rversion(Fcall *rx, Fcall *tx)
{
	if(msize > rx->msize)
		msize = rx->msize;
	tx->msize = msize;
	if(strncmp(rx->version, "9P", 2) != 0)
		tx->version = "unknown";
	else
		tx->version = "9P2000";
}

void
rauth(Fcall *rx, Fcall *tx)
{
	char *e;

	if((e = auth->auth(rx, tx)) != nil)
		seterror(tx, e);
}

void
rattach(Fcall *rx, Fcall *tx)
{
	char *e;
	Fid *fid;
	User *u;

	if(rx->aname == nil)
		rx->aname = "";

	if(strcmp(rx->aname, "device") == 0){
		if(connected && !devallowed){
			seterror(tx, Especial0);
			return;
		}
		devallowed = 1;
	}else{
		if(connected && devallowed){
			seterror(tx, Especial1);
			return;
		}
	}

	if(strcmp(rx->uname, "none") == 0){
		if(authed == 0){
			seterror(tx, Eauth);
			return;
		}
	} else {
		if((e = auth->attach(rx, tx)) != nil){
			seterror(tx, e);
			return;
		}
		authed++;
	}

	if((fid = newfid(rx->fid, &e)) == nil){
		seterror(tx, e);
		return;
	}
	fid->path = estrdup("/");
	if(fidstat(fid, &e) < 0){
		seterror(tx, e);
		freefid(fid);
		return;
	}

	if(defaultuser)
		rx->uname = defaultuser;

	if((u = uname2user(rx->uname)) == nil
	|| (!defaultuser && u->id == 0)){
		/* we don't know anyone named root... */
		seterror(tx, Eunknownuser);
		freefid(fid);
		return;
	}

	fid->u = u;
	tx->qid = stat2qid(&fid->st);
	return;
}

void
rwalk(Fcall *rx, Fcall *tx)
{
	int i;
	char *path, *e;
	Fid *fid, *nfid;

	e = nil;
	if((fid = oldfid(rx->fid, &e)) == nil){
		seterror(tx, e);
		return;
	}

	if(fid->omode != -1){
		seterror(tx, Ebadusefid);
		return;
	}

	if(fidstat(fid, &e) < 0){
		seterror(tx, e);
		return;
	}

	if(!S_ISDIR(fid->st.st_mode) && rx->nwname){
		seterror(tx, Enotdir);
		return;
	}

	nfid = nil;
	if(rx->newfid != rx->fid && (nfid = newfid(rx->newfid, &e)) == nil){
		seterror(tx, e);
		return;
	}

	path = estrdup(fid->path);
	e = nil;
	for(i=0; i<rx->nwname; i++)
		if(userwalk(fid->u, &path, rx->wname[i], &tx->wqid[i], &e) < 0)
			break;

	if(i == rx->nwname){		/* successful clone or walk */
		tx->nwqid = i;
		if(nfid){
			nfid->path = path;
			nfid->u = fid->u;
		}else{
			free(fid->path);
			fid->path = path;
		}
	}else{
		if(i > 0)		/* partial walk? */
			tx->nwqid = i;
		else
			seterror(tx, e);

		if(nfid)		/* clone implicit new fid */
			freefid(nfid);
		free(path);
	}
	return;
}

void
ropen(Fcall *rx, Fcall *tx)
{
	char *e;
	Fid *fid;

	if((fid = oldfid(rx->fid, &e)) == nil){
		seterror(tx, e);
		return;
	}

	if(fid->omode != -1){
		seterror(tx, Ebadusefid);
		return;
	}

	if(fidstat(fid, &e) < 0){
		seterror(tx, e);
		return;
	}

	if(!devallowed && S_ISSPECIAL(fid->st.st_mode)){
		seterror(tx, Especial);
		return;
	}

	if(useropen(fid, rx->mode, &e) < 0){
		seterror(tx, e);
		return;
	}

	tx->iounit = 0;
	tx->qid = stat2qid(&fid->st);
}

void
rcreate(Fcall *rx, Fcall *tx)
{
	char *e;
	Fid *fid;

	if((fid = oldfid(rx->fid, &e)) == nil){
		seterror(tx, e);
		return;
	}

	if(fid->omode != -1){
		seterror(tx, Ebadusefid);
		return;
	}

	if(fidstat(fid, &e) < 0){
		seterror(tx, e);
		return;
	}

	if(!S_ISDIR(fid->st.st_mode)){
		seterror(tx, Enotdir);
		return;
	}

	if(usercreate(fid, rx->name, rx->mode, rx->perm, &e) < 0){
		seterror(tx, e);
		return;
	}

	if(fidstat(fid, &e) < 0){
		seterror(tx, e);
		return;
	}

	tx->iounit = 0;
	tx->qid = stat2qid(&fid->st);
}

uchar
modebyte(struct stat *st)
{
	uchar b;

	b = 0;

	if(S_ISDIR(st->st_mode))