cs.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

{
	int mode;
	char *err;

	err = 0;
	mode = job->request.mode;
	if(mf->qid.type & QTDIR){
		if(mode)
			err = "permission denied";
	}
	job->reply.qid = mf->qid;
	job->reply.iounit = 0;
	sendmsg(job, err);
}

void
rcreate(Job *job, Mfile *mf)
{
	USED(mf);
	sendmsg(job, "creation permission denied");
}

void
rread(Job *job, Mfile *mf)
{
	int i, n, cnt;
	long off, toff, clock;
	Dir dir;
	uchar buf[Maxfdata];
	char *err;

	n = 0;
	err = 0;
	off = job->request.offset;
	cnt = job->request.count;
	if(mf->qid.type & QTDIR){
		clock = time(0);
		if(off == 0){
			dir.name = "cs";
			dir.qid.type = QTFILE;
			dir.qid.vers = vers;
			dir.qid.path = Qcs;
			dir.mode = 0666;
			dir.length = 0;
			dir.uid = mf->user;
			dir.gid = mf->user;
			dir.muid = mf->user;
			dir.atime = clock;	/* wrong */
			dir.mtime = clock;	/* wrong */
			n = convD2M(&dir, buf, sizeof buf);
		}
		job->reply.data = (char*)buf;
	} else {
		for(;;){
			/* look for an answer at the right offset */
			toff = 0;
			for(i = 0; mf->reply[i] && i < mf->nreply; i++){
				n = mf->replylen[i];
				if(off < toff + n)
					break;
				toff += n;
			}
			if(i < mf->nreply)
				break;		/* got something to return */

			/* try looking up more answers */
			if(lookup(mf) == 0){
				/* no more */
				n = 0;
				goto send;
			}
		}

		/* give back a single reply (or part of one) */
		job->reply.data = mf->reply[i] + (off - toff);
		if(cnt > toff - off + n)
			n = toff - off + n;
		else
			n = cnt;
	}
send:
	job->reply.count = n;
	sendmsg(job, err);
}
void
cleanmf(Mfile *mf)
{
	int i;

	if(mf->net != nil){
		free(mf->net);
		mf->net = nil;
	}
	if(mf->host != nil){
		free(mf->host);
		mf->host = nil;
	}
	if(mf->serv != nil){
		free(mf->serv);
		mf->serv = nil;
	}
	if(mf->rem != nil){
		free(mf->rem);
		mf->rem = nil;
	}
	for(i = 0; i < mf->nreply; i++){
		free(mf->reply[i]);
		mf->reply[i] = nil;
		mf->replylen[i] = 0;
	}
	mf->nreply = 0;
	mf->nextnet = netlist;
}

void
rwrite(Job *job, Mfile *mf)
{
	int cnt, n;
	char *err;
	char *field[4];
	char curerr[64];

	err = 0;
	cnt = job->request.count;
	if(mf->qid.type & QTDIR){
		err = "can't write directory";
		goto send;
	}
	if(cnt >= Maxrequest){
		err = "request too long";
		goto send;
	}
	job->request.data[cnt] = 0;

	/*
	 *  toggle debugging
	 */
	if(strncmp(job->request.data, "debug", 5)==0){
		debug ^= 1;
		syslog(1, logfile, "debug %d", debug);
		goto send;
	}

	/*
	 *  toggle debugging
	 */
	if(strncmp(job->request.data, "paranoia", 8)==0){
		paranoia ^= 1;
		syslog(1, logfile, "paranoia %d", paranoia);
		goto send;
	}

	/*
	 *  add networks to the default list
	 */
	if(strncmp(job->request.data, "add ", 4)==0){
		if(job->request.data[cnt-1] == '\n')
			job->request.data[cnt-1] = 0;
		netadd(job->request.data+4);
		readipinterfaces();
		goto send;
	}

	/*
	 *  refresh all state
	 */
	if(strncmp(job->request.data, "refresh", 7)==0){
		netinit(1);
		goto send;
	}

	/* start transaction with a clean slate */
	cleanmf(mf);

	/*
	 *  look for a general query
	 */
	if(*job->request.data == '!'){
		err = genquery(mf, job->request.data+1);
		goto send;
	}

	if(debug)
		syslog(0, logfile, "write %s", job->request.data);
	if(paranoia)
		syslog(0, paranoiafile, "write %s by %s", job->request.data, mf->user);

	/*
	 *  break up name
	 */
	n = getfields(job->request.data, field, 4, 1, "!");
	switch(n){
	case 1:
		mf->net = strdup("net");
		mf->host = strdup(field[0]);
		break;
	case 4:
		mf->rem = strdup(field[3]);
		/* fall through */
	case 3:
		mf->serv = strdup(field[2]);
		/* fall through */
	case 2:
		mf->host = strdup(field[1]);
		mf->net = strdup(field[0]);
		break;
	}

	/*
	 *  do the first net worth of lookup
	 */
	if(lookup(mf) == 0){
		rerrstr(curerr, sizeof curerr);
		err = curerr;
	}
send:
	job->reply.count = cnt;
	sendmsg(job, err);
}

void
rclunk(Job *job, Mfile *mf)
{
	cleanmf(mf);
	free(mf->user);
	mf->user = 0;
	mf->busy = 0;
	mf->fid = 0;
	sendmsg(job, 0);
}

void
rremove(Job *job, Mfile *mf)
{
	USED(mf);
	sendmsg(job, "remove permission denied");
}

void
rstat(Job *job, Mfile *mf)
{
	Dir dir;
	uchar buf[IOHDRSZ+Maxfdata];

	if(mf->qid.type & QTDIR){
		dir.name = ".";
		dir.mode = DMDIR|0555;
	} else {
		dir.name = "cs";
		dir.mode = 0666;
	}
	dir.qid = mf->qid;
	dir.length = 0;
	dir.uid = mf->user;
	dir.gid = mf->user;
	dir.muid = mf->user;
	dir.atime = dir.mtime = time(0);
	job->reply.nstat = convD2M(&dir, buf, sizeof buf);
	job->reply.stat = buf;
	sendmsg(job, 0);
}

void
rwstat(Job *job, Mfile *mf)
{
	USED(mf);
	sendmsg(job, "wstat permission denied");
}

void
sendmsg(Job *job, char *err)
{
	int n;
	uchar mdata[IOHDRSZ + Maxfdata];
	char ename[ERRMAX];

	if(err){
		job->reply.type = Rerror;
		snprint(ename, sizeof(ename), "cs: %s", err);
		job->reply.ename = ename;
	}else{
		job->reply.type = job->request.type+1;
	}
	job->reply.tag = job->request.tag;
	n = convS2M(&job->reply, mdata, sizeof mdata);
	if(n == 0){
		syslog(1, logfile, "sendmsg convS2M of %F returns 0", &job->reply);
		abort();
	}
	lock(&joblock);
	if(job->flushed == 0)
		if(write(mfd[1], mdata, n)!=n)
			error("mount write");
	unlock(&joblock);
	if(debug)
		syslog(0, logfile, "%F %d", &job->reply, n);
}

void
error(char *s)
{
	syslog(1, "cs", "%s: %r", s);
	_exits(0);
}

static int
isvalidip(uchar *ip)
{
	return ipcmp(ip, IPnoaddr) != 0 && ipcmp(ip, v4prefix) != 0;
}

static uchar loopbacknet[IPaddrlen] = {
	0, 0, 0, 0,
	0, 0, 0, 0,
	0, 0, 0xff, 0xff,
	127, 0, 0, 0
};
static uchar loopbackmask[IPaddrlen] = {
	0xff, 0xff, 0xff, 0xff,
	0xff, 0xff, 0xff, 0xff,
	0xff, 0xff, 0xff, 0xff,
	0xff, 0, 0, 0
};

void
readipinterfaces(void)
{
	if(myipaddr(ipa, mntpt) != 0)
		ipmove(ipa, IPnoaddr);
	sprint(ipaddr, "%I", ipa);
	if (debug)
		syslog(0, "dns", "ipaddr is %s\n", ipaddr);
}

/*
 *  get the system name
 */
void
ipid(void)
{
	uchar addr[6];
	Ndbtuple *t, *tt;
	char *p, *attr;
	Ndbs s;
	int f;
	char buf[Maxpath];

	/* use environment, ether addr, or ipaddr to get system name */
	if(mysysname == 0){
		/*
		 *  environment has priority.
		 *
		 *  on the sgi power the default system name
		 *  is the ip address.  ignore that.
		 *
		 */
		p = getenv("sysname");
		if(p && *p){
			attr = ipattr(p);
			if(strcmp(attr, "ip") != 0)
				mysysname = strdup(p);
		}

		/*
		 *  the /net/ndb contains what the network
		 *  figured out from DHCP.  use that name if
		 *  there is one. 
		 */
		if(mysysname == 0 && netdb != nil){
			ndbreopen(netdb);
			for(tt = t = ndbparse(netdb); t != nil; t = t->entry){
				if(strcmp(t->attr, "sys") == 0){
					mysysname = strdup(t->val);
					break;
				}
			}
			ndbfree(tt);
		}

		/* next network database, ip address, and ether address to find a name */
		if(mysysname == 0){
			t = nil;
			if(isvalidip(ipa))
				free(ndbgetvalue(db, &s, "ip", ipaddr, "sys", &t));
			if(t == nil){
				for(f = 0; f < 3; f++){
					snprint(buf, sizeof buf, "%s/ether%d", mntpt, f);
					if(myetheraddr(addr, buf) >= 0){
						snprint(eaddr, sizeof(eaddr), "%E", addr);
						free(ndbgetvalue(db, &s, "ether", eaddr, "sys", &t));
						if(t != nil)
							break;
					}
				}
			}
			for(tt = t; tt != nil; tt = tt->entry){
				if(strcmp(tt->attr, "sys") == 0){
					mysysname = strdup(tt->val);
					break;
				}
			}
			ndbfree(t);
		}

		/* nothing else worked, use the ip address */
		if(mysysname == 0 && isvalidip(ipa))
			mysysname = strdup(ipaddr);
					

		/* set /dev/sysname if we now know it */
		if(mysysname){
			f = open("/dev/sysname", OWRITE);
			if(f >= 0){
				write(f, mysysname, strlen(mysysname));
				close(f);
			}
		}
	}
}

/*
 *  Set up a list of default networks by looking for
 *  /net/ * /clone.
 */
void
netinit(int background)
{
	char clone[Maxpath];
	Network *np;
	static int working;

	if(background){
		switch(rfork(RFPROC|RFNOTEG|RFMEM|RFNOWAIT)){
		case 0:
			break;
		default:
			return;
		}
		lock(&netlock);
	}

	/* add the mounted networks to the default list */
	for(np = network; np->net; np++){
		if(np->considered)
			continue;
		snprint(clone, sizeof(clone), "%s/%s/clone", mntpt, np->net);
		if(access(clone, AEXIST) < 0)
			continue;
		if(netlist)
			last->next = np;
		else
			netlist = np;
		last = np;
		np->next = 0;
		np->considered = 1;
	}

	/* find out what our ip address is */
	readipinterfaces();

	/* set the system name if we need to, these says ip is all we have */
	ipid();

	if(debug)
		syslog(0, logfile, "mysysname %s eaddr %s ipaddr %s ipa %I\n",
			mysysname?mysysname:"???", eaddr, ipaddr, ipa);

	if(background){
		unlock(&netlock);
		_exits(0);
	}
}

/*
 *  add networks to the standard list
 */
void
netadd(char *p)
{
	Network *np;
	char *field[12];
	int i, n;

	n = getfields(p, field, 12, 1, " ");
	for(i = 0; i < n; i++){
		for(np = network; np->net; np++){
			if(strcmp(field[i], np->net) != 0)
				continue;
			if(np->considered)
				break;
			if(netlist)
				last->next = np;
			else
				netlist = np;
			last = np;
			np->next = 0;
			np->considered = 1;
		}
	}
}

int
lookforproto(Ndbtuple *t, char *proto)
{
	for(; t != nil; t = t->entry)
		if(strcmp(t->attr, "proto") == 0 && strcmp(t->val, proto) == 0)
			return 1;
	return 0;
}

/*
 *  lookup a request.  the network "net" means we should pick the
 *  best network to get there.
 */
int
lookup(Mfile *mf)
{
	Network *np;
	char *cp;
	Ndbtuple *nt, *t;
	char reply[Maxreply];
	int i, rv;
	int hack;

	/* open up the standard db files */
	if(db == 0)
		ndbinit();
	if(db == 0)
		error("can't open mf->network database\n");

	rv = 0;

	if(mf->net == nil)
		return 0;	/* must have been a genquery */

	if(strcmp(mf->net, "net") == 0){ 
		/*
		 *  go through set of default nets
		 */
		for(np = mf->nextnet; np; np = np->next){
			nt = (*np->lookup)(np, mf->host, mf->serv, 1);
			if(nt == nil)
				continue;
			hack = np->fasttimeouthack && !lookforproto(nt, np->net);
			for(t = nt; mf->nreply < Nreply && t; t = t->entry){
				cp = (*np->trans)(t, np, mf->serv, mf->rem, hack);
				if(cp){
					/* avoid duplicates */
					for(i = 0; i < mf->nreply; i++)
						if(strcmp(mf->reply[i], cp) == 0)
							break;
					if(i == mf->nreply){
						/* save the reply */
						mf->replylen[mf->nreply] = strlen(cp);
						mf->reply[mf->nreply++] = cp;
						rv++;
					}
				}
			}
			ndbfree(nt);
			np = np->next;
			break;
		}
		mf->nextnet = np;
		return rv;
	}

	/*
	 *  if not /net, we only get one lookup
	 */
	if(mf->nreply != 0)
		return 0;
	/*
	 *  look for a specific network
	 */
	for(np = netlist; np && np->net != nil; np++){
		if(np->fasttimeouthack)
			continue;
		if(strcmp(np->net, mf->net) == 0)
			break;
	}

	if(np && np->net != nil){
		/*
		 *  known network
		 */
		nt = (*np->lookup)(np, mf->host, mf->serv, 1);
		for(t = nt; mf->nreply < Nreply && t; t = t->entry){
			cp = (*np->trans)(t, np, mf->serv, mf->rem, 0);
			if(cp){
				mf->replylen[mf->nreply] = strlen(cp);
				mf->reply[mf->nreply++] = cp;
				rv++;
			}
		}
		ndbfree(nt);
		return rv;
	} else {
		/*
		 *  not a known network, don't translate host or service
		 */
		if(mf->serv)
			snprint(reply, sizeof(reply), "%s/%s/clone %s!%s",
				mntpt, mf->net, mf->host, mf->serv);
		else
			snprint(reply, sizeof(reply), "%s/%s/clone %s",
				mntpt, mf->net, mf->host);
		mf->reply[0] = strdup(reply);
		mf->replylen[0] = strlen(reply);
		mf->nreply = 1;
		return 1;
	}
}

/*
 *  translate an ip service name into a port number.  If it's a numeric port
 *  number, look for restricted access.
 *