exportfs.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

/*
 * exportfs - Export a plan 9 name space across a network
 */
#include <u.h>
#include <libc.h>
#include <auth.h>
#include <fcall.h>
#include <libsec.h>
#define Extern
#include "exportfs.h"

#define QIDPATH	((1LL<<48)-1)
vlong newqid = 0;

enum {
	Encnone,
	Encssl,
	Enctls,
};

void (*fcalls[])(Fsrpc*) =
{
	[Tversion]	Xversion,
	[Tauth]	Xauth,
	[Tflush]	Xflush,
	[Tattach]	Xattach,
	[Twalk]		Xwalk,
	[Topen]		slave,
	[Tcreate]	Xcreate,
	[Tclunk]	Xclunk,
	[Tread]		slave,
	[Twrite]	slave,
	[Tremove]	Xremove,
	[Tstat]		Xstat,
	[Twstat]	Xwstat,
};

/* accounting and debugging counters */
int	filecnt;
int	freecnt;
int	qidcnt;
int	qfreecnt;
int	ncollision;

int	netfd;
int	srvfd = -1;
int	nonone = 1;
char	*filterp;
char	*ealgs = "rc4_256 sha1";
char	*aanfilter = "/bin/aan";
int	encproto = Encnone;
int	readonly;

static void	mksecret(char *, uchar *);
static int localread9pmsg(int, void *, uint, ulong *);
static char *anstring  = "tcp!*!0";
int	filter(int, char *);

void
usage(void)
{
	fprint(2, "usage:	%s [-adnsR] [-f dbgfile] [-m msize] [-r root] [-S srvfile] [-e 'crypt hash'] [-P exclusion-file] [-A announce-string] [-B address]\n", argv0);
	fatal("usage");
}

void
main(int argc, char **argv)
{
	char buf[ERRMAX], ebuf[ERRMAX], *srvfdfile;
	Fsrpc *r;
	int doauth, n, fd;
	char *dbfile, *srv, *na, *nsfile, *keyspec;
	AuthInfo *ai;
	ulong initial;

	dbfile = "/tmp/exportdb";
	srv = nil;
	srvfd = -1;
	srvfdfile = nil;
	na = nil;
	nsfile = nil;
	keyspec = "";
	doauth = 0;

	ai = nil;
	ARGBEGIN{
	case 'a':
		doauth = 1;
		break;

	case 'd':
		dbg++;
		break;

	case 'e':
		ealgs = EARGF(usage());
		if(*ealgs == 0 || strcmp(ealgs, "clear") == 0)
			ealgs = nil;
		break;

	case 'f':
		dbfile = EARGF(usage());
		break;

	case 'k':
		keyspec = EARGF(usage());
		break;

	case 'm':
		messagesize = strtoul(EARGF(usage()), nil, 0);
		break;

	case 'n':
		nonone = 0;
		break;

	case 'r':
		srv = EARGF(usage());
		break;

	case 's':
		srv = "/";
		break;

	case 'A':
		anstring = EARGF(usage());
		break;

	case 'B':
		na = EARGF(usage());
		break;

	case 'F':
		/* accepted but ignored, for backwards compatibility */
		break;

	case 'N':
		nsfile = EARGF(usage());
		break;

	case 'P':
		patternfile = EARGF(usage());
		break;

	case 'R':
		readonly = 1;
		break;

	case 'S':
		if(srvfdfile)
			usage();
		srvfdfile = EARGF(usage());
		break;

	default:
		usage();
	}ARGEND
	USED(argc, argv);

	if(doauth){
		/*
		 * We use p9any so we don't have to visit this code again, with the
		 * cost that this code is incompatible with the old world, which
		 * requires p9sk2. (The two differ in who talks first, so compatibility
		 * is awkward.)
		 */
		ai = auth_proxy(0, auth_getkey, "proto=p9any role=server %s", keyspec);
		if(ai == nil)
			fatal("auth_proxy: %r");
		if(nonone && strcmp(ai->cuid, "none") == 0)
			fatal("exportfs by none disallowed");
		if(auth_chuid(ai, nsfile) < 0)
			fatal("auth_chuid: %r");
		putenv("service", "exportfs");
	}

	if(srvfdfile){
		if((srvfd = open(srvfdfile, ORDWR)) < 0)
			sysfatal("open '%s': %r", srvfdfile);
	}

	if(na){
		if(srv == nil)
			sysfatal("-B requires -s");

		if((fd = dial(netmkaddr(na, 0, "importfs"), 0, 0, 0)) < 0)
			sysfatal("can't dial %s: %r", na);
	
		ai = auth_proxy(fd, auth_getkey, "proto=p9any role=client %s", keyspec);
		if(ai == nil)
			sysfatal("%r: %s", na);

		dup(fd, 0);
		dup(fd, 1);
		close(fd);
	}

	exclusions();

	if(dbg) {
		n = create(dbfile, OWRITE|OTRUNC, 0666);
		dup(n, DFD);
		close(n);
	}

	if(srvfd >= 0 && srv){
		fprint(2, "exportfs: -S cannot be used with -r or -s\n");
		usage();
	}

	DEBUG(DFD, "exportfs: started\n");

	rfork(RFNOTEG);

	if(messagesize == 0){
		messagesize = iounit(netfd);
		if(messagesize == 0)
			messagesize = 8192+IOHDRSZ;
	}

	Workq = emallocz(sizeof(Fsrpc)*Nr_workbufs);
//	for(i=0; i<Nr_workbufs; i++)
//		Workq[i].buf = emallocz(messagesize);
	fhash = emallocz(sizeof(Fid*)*FHASHSIZE);

	fmtinstall('F', fcallfmt);

	/*
	 * Get tree to serve from network connection,
	 * check we can get there and ack the connection
 	 */
	if(srvfd != -1) {
		/* do nothing */
	}
	else if(srv) {
		chdir(srv);
		DEBUG(DFD, "invoked as server for %s", srv);
		strncpy(buf, srv, sizeof buf);
	}
	else {
		buf[0] = 0;
		n = read(0, buf, sizeof(buf)-1);
		if(n < 0) {
			errstr(buf, sizeof buf);
			fprint(0, "read(0): %s", buf);
			DEBUG(DFD, "read(0): %s", buf);
			exits(buf);
		}
		buf[n] = 0;
		if(chdir(buf) < 0) {
			errstr(ebuf, sizeof ebuf);
			fprint(0, "chdir(%d:\"%s\"): %s", n, buf, ebuf);
			DEBUG(DFD, "chdir(%d:\"%s\"): %s", n, buf, ebuf);
			exits(ebuf);
		}
	}

	DEBUG(DFD, "\niniting root\n");
	initroot();

	DEBUG(DFD, "exportfs: %s\n", buf);

	if(srv == nil && srvfd == -1 && write(0, "OK", 2) != 2)
		fatal("open ack write");

	if (readn(netfd, &initial, sizeof(ulong)) < sizeof(ulong))
		fatal("can't read initial string: %r\n");

	if (!strncmp((char *)&initial, "impo", sizeof(ulong))) {
		char buf[128], *p, *args[3];

		// New import.  Read import's parameters...
		initial = 0;

		p = buf;
		while (p - buf < sizeof buf) {
			if ((n = read(netfd, p, 1)) < 0)
				fatal("can't read impo arguments: %r\n");

			if (n == 0)
				fatal("connection closed while reading arguments\n");

			if (*p == '\n') 
				*p = '\0';
			if (*p++ == '\0')
				break;
		}
		
		if (tokenize(buf, args, nelem(args)) != 2)
			fatal("impo arguments invalid: impo%s...\n", buf);

		if (!strcmp(args[0], "aan"))
			filterp = aanfilter;
		else if (strcmp(args[0], "nofilter"))
			fatal("import filter argument unsupported: %s\n", args[0]);

		if (!strcmp(args[1], "ssl"))
			encproto = Encssl;
		else if (!strcmp(args[1], "tls"))
			encproto = Enctls;
		else if (strcmp(args[1], "clear"))
			fatal("import encryption proto unsupported: %s\n", args[1]);

		if (encproto == Enctls)
			sysfatal("%s: tls has not yet been implemented\n", argv[0]);
	}

	if (encproto != Encnone && ealgs && ai) {
		uchar key[16];
		uchar digest[SHA1dlen];
		char fromclientsecret[21];
		char fromserversecret[21];
		int i;

		memmove(key+4, ai->secret, ai->nsecret);

		/* exchange random numbers */
		srand(truerand());
		for(i = 0; i < 4; i++)
			key[i+12] = rand();

		if (initial) 
			fatal("Protocol botch: old import\n");
		if(readn(netfd, key, 4) != 4)
			fatal("can't read key part; %r\n");

		if(write(netfd, key+12, 4) != 4)
			fatal("can't write key part; %r\n");

		/* scramble into two secrets */
		sha1(key, sizeof(key), digest, nil);
		mksecret(fromclientsecret, digest);
		mksecret(fromserversecret, digest+10);

		if (filterp)
			netfd = filter(netfd, filterp);

		switch (encproto) {
		case Encssl:
			netfd = pushssl(netfd, ealgs, fromserversecret, 
						fromclientsecret, nil);
			break;
		case Enctls:
		default:
			fatal("Unsupported encryption protocol\n");
		}

		if(netfd < 0)
			fatal("can't establish ssl connection: %r");
	}
	else if (filterp) {
		if (initial) 
			fatal("Protocol botch: don't know how to deal with this\n");
		netfd = filter(netfd, filterp);
	}

	/*
	 * Start serving file requests from the network
	 */
	for(;;) {
		r = getsbuf();
		if(r == 0)
			fatal("Out of service buffers");
			
		n = localread9pmsg(netfd, r->buf, messagesize, &initial);
		if(n <= 0)
			fatal(nil);

		if(convM2S(r->buf, n, &r->work) == 0)
			fatal("convM2S format error");

		DEBUG(DFD, "%F\n", &r->work);
		(fcalls[r->work.type])(r);
	}
}

// WARNING: Replace this with the original version as soon as all 
// _old_ imports have been replaced with negotiating imports.  Also
// cpu relies on this (which needs to be fixed!) -- pb.
static int
localread9pmsg(int fd, void *abuf, uint n, ulong *initial)
{
	int m, len;
	uchar *buf;

	buf = abuf;

	/* read count */
	assert(BIT32SZ == sizeof(ulong));
	if (*initial) {
		memcpy(buf, initial, BIT32SZ);
		*initial = 0;
	}
	else {
		m = readn(fd, buf, BIT32SZ);
		if(m != BIT32SZ){
			if(m < 0)
				return -1;
			return 0;
		}
	}

	len = GBIT32(buf);
	if(len <= BIT32SZ || len > n){
		werrstr("bad length in 9P2000 message header");
		return -1;
	}
	len -= BIT32SZ;
	m = readn(fd, buf+BIT32SZ, len);
	if(m < len)
		return 0;
	return BIT32SZ+m;
}
void
reply(Fcall *r, Fcall *t, char *err)
{
	uchar *data;
	int n;

	t->tag = r->tag;
	t->fid = r->fid;
	if(err) {
		t->type = Rerror;
		t->ename = err;
	}
	else 
		t->type = r->type + 1;

	DEBUG(DFD, "\t%F\n", t);

	data = malloc(messagesize);	/* not mallocz; no need to clear */
	if(data == nil)
		fatal(Enomem);
	n = convS2M(t, data, messagesize);
	if(write(netfd, data, n)!=n)
{syslog(0, "exportfs", "short write: %r");
		fatal("mount write");
}
	free(data);
}

Fid *
getfid(int nr)
{
	Fid *f;

	for(f = fidhash(nr); f; f = f->next)
		if(f->nr == nr)
			return f;

	return 0;
}

int
freefid(int nr)
{
	Fid *f, **l;