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

#include <u.h>
#include <libc.h>
#include <auth.h>
#include <fcall.h>
#include <bio.h>
#include <ctype.h>
#include <ndb.h>
#include <ip.h>
#include <String.h>

enum
{
	Nreply=			20,
	Maxreply=		256,
	Maxrequest=		128,
	Maxpath=		128,
	Maxfdata=		8192,
	Maxhost=		64,		/* maximum host name size */
	Maxservice=		64,		/* maximum service name size */

	Qdir=			0,
	Qcs=			1,
};

typedef struct Mfile	Mfile;
typedef struct Mlist	Mlist;
typedef struct Network	Network;
typedef struct Flushreq	Flushreq;
typedef struct Job	Job;

int vers;		/* incremented each clone/attach */

struct Mfile
{
	int		busy;

	char		*user;
	Qid		qid;
	int		fid;

	/*
	 *  current request
	 */
	char		*net;
	char		*host;
	char		*serv;
	char		*rem;

	/*
	 *  result of the last lookup
	 */
	Network		*nextnet;
	int		nreply;
	char		*reply[Nreply];
	int		replylen[Nreply];
};

struct Mlist
{
	Mlist	*next;
	Mfile	mf;
};


//
//  active requests
//
struct Job
{
	Job	*next;
	int	flushed;
	Fcall	request;
	Fcall	reply;
};
Lock	joblock;
Job	*joblist;

Mlist	*mlist;
int	mfd[2];
int	debug;
int	paranoia;
jmp_buf	masterjmp;	/* return through here after a slave process has been created */
int	*isslave;	/* *isslave non-zero means this is a slave process */
char	*dbfile;
Ndb	*db, *netdb;

void	rversion(Job*);
void	rflush(Job*);
void	rattach(Job*, Mfile*);
char*	rwalk(Job*, Mfile*);
void	ropen(Job*, Mfile*);
void	rcreate(Job*, Mfile*);
void	rread(Job*, Mfile*);
void	rwrite(Job*, Mfile*);
void	rclunk(Job*, Mfile*);
void	rremove(Job*, Mfile*);
void	rstat(Job*, Mfile*);
void	rwstat(Job*, Mfile*);
void	rauth(Job*);
void	sendmsg(Job*, char*);
void	error(char*);
void	mountinit(char*, char*);
void	io(void);
void	ndbinit(void);
void	netinit(int);
void	netadd(char*);
char	*genquery(Mfile*, char*);
char*	ipinfoquery(Mfile*, char**, int);
int	needproto(Network*, Ndbtuple*);
int	lookup(Mfile*);
Ndbtuple*	reorder(Ndbtuple*, Ndbtuple*);
void	ipid(void);
void	readipinterfaces(void);
void*	emalloc(int);
char*	estrdup(char*);
Job*	newjob(void);
void	freejob(Job*);
void	setext(char*, int, char*);
void	cleanmf(Mfile*);

extern void	paralloc(void);

Lock	dblock;		/* mutex on database operations */
Lock	netlock;	/* mutex for netinit() */

char	*logfile = "cs";
char	*paranoiafile = "cs.paranoia";

char	mntpt[Maxpath];
char	netndb[Maxpath];

/*
 *  Network specific translators
 */
Ndbtuple*	iplookup(Network*, char*, char*, int);
char*		iptrans(Ndbtuple*, Network*, char*, char*, int);
Ndbtuple*	telcolookup(Network*, char*, char*, int);
char*		telcotrans(Ndbtuple*, Network*, char*, char*, int);
Ndbtuple*	dnsiplookup(char*, Ndbs*);

struct Network
{
	char		*net;
	Ndbtuple	*(*lookup)(Network*, char*, char*, int);
	char		*(*trans)(Ndbtuple*, Network*, char*, char*, int);
	int		considered;
	int		fasttimeouthack;
	Network		*next;
};

enum
{
	Nilfast,
	Ntcp,
	Nil,
	Nudp,
	Nicmp,
	Nicmpv6,
	Nrudp,
	Ntelco,
};

/*
 *  net doesn't apply to (r)udp, icmp(v6), or telco (for speed)
 */
Network network[] = {
[Ntcp]		{ "tcp",	iplookup,	iptrans,	0, 0 },
[Nilfast]	{ "il",		iplookup,	iptrans,	0, 1 },
[Nil]		{ "il",		iplookup,	iptrans,	0, 0 },
[Nudp]		{ "udp",	iplookup,	iptrans,	1, 0 },
[Nicmp]		{ "icmp",	iplookup,	iptrans,	1, 0 },
[Nicmpv6]	{ "icmpv6",	iplookup,	iptrans,	1, 0 },
[Nrudp]		{ "rudp",	iplookup,	iptrans,	1, 0 },
[Ntelco]	{ "telco",	telcolookup,	telcotrans,	1, 0 },
		{ 0 },
};

Lock ipifclock;
Ipifc *ipifcs;

char	eaddr[16];		/* ascii ethernet address */
char	ipaddr[64];		/* ascii internet address */
uchar	ipa[IPaddrlen];		/* binary internet address */
char	*mysysname;

Network *netlist;		/* networks ordered by preference */
Network *last;

static void
nstrcpy(char *to, char *from, int len)
{
	strncpy(to, from, len);
	to[len-1] = 0;
}

void
usage(void)
{
	fprint(2, "usage: %s [-d] [-f ndb-file] [-x netmtpt] [-n]\n", argv0);
	exits("usage");
}

void
main(int argc, char *argv[])
{
	char servefile[Maxpath];
	int justsetname;
	char *p;
	char ext[Maxpath];

	justsetname = 0;
	setnetmtpt(mntpt, sizeof(mntpt), nil);
	ext[0] = 0;
	ARGBEGIN{
	case 'd':
		debug = 1;
		break;
	case 'f':
		p = ARGF();
		if(p == nil)
			usage();
		dbfile = p;
		break;
	case 'x':
		p = ARGF();
		if(p == nil)
			usage();
		setnetmtpt(mntpt, sizeof(mntpt), p);
		setext(ext, sizeof(ext), mntpt);
		break;
	case 'n':
		justsetname = 1;
		break;
	}ARGEND
	USED(argc);
	USED(argv);

	rfork(RFREND|RFNOTEG);

	snprint(servefile, sizeof(servefile), "#s/cs%s", ext);
	snprint(netndb, sizeof(netndb), "%s/ndb", mntpt);
	unmount(servefile, mntpt);
	remove(servefile);

	fmtinstall('E', eipfmt);
	fmtinstall('I', eipfmt);
	fmtinstall('M', eipfmt);
	fmtinstall('F', fcallfmt);

	ndbinit();
	netinit(0);

	if(!justsetname){
		mountinit(servefile, mntpt);
		io();
	}
	exits(0);
}

/*
 *  if a mount point is specified, set the cs extention to be the mount point
 *  with '_'s replacing '/'s
 */
void
setext(char *ext, int n, char *p)
{
	int i, c;

	n--;
	for(i = 0; i < n; i++){
		c = p[i];
		if(c == 0)
			break;
		if(c == '/')
			c = '_';
		ext[i] = c;
	}
	ext[i] = 0;
}

void
mountinit(char *service, char *mntpt)
{
	int f;
	int p[2];
	char buf[32];

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

	/*
	 *  make a /srv/cs
	 */
	f = create(service, OWRITE|ORCLOSE, 0666);
	if(f < 0)
		error(service);
	snprint(buf, sizeof(buf), "%d", p[1]);
	if(write(f, buf, strlen(buf)) != strlen(buf))
		error("write /srv/cs");

	switch(rfork(RFFDG|RFPROC|RFNAMEG)){
	case 0:
		close(p[1]);
		break;
	case -1:
		error("fork failed\n");
	default:
		/*
		 *  put ourselves into the file system
		 */
		close(p[0]);
		if(mount(p[1], -1, mntpt, MAFTER, "") < 0)
			error("mount failed\n");
		_exits(0);
	}
	mfd[0] = mfd[1] = p[0];
}

void
ndbinit(void)
{
	db = ndbopen(dbfile);
	if(db == nil)
		error("can't open network database");

	netdb = ndbopen(netndb);
	if(netdb != nil){
		netdb->nohash = 1;
		db = ndbcat(netdb, db);
	}
}

Mfile*
newfid(int fid)
{
	Mlist *f, *ff;
	Mfile *mf;

	ff = 0;
	for(f = mlist; f; f = f->next)
		if(f->mf.busy && f->mf.fid == fid)
			return &f->mf;
		else if(!ff && !f->mf.busy)
			ff = f;
	if(ff == 0){
		ff = emalloc(sizeof *f);
		ff->next = mlist;
		mlist = ff;
	}
	mf = &ff->mf;
	memset(mf, 0, sizeof *mf);
	mf->fid = fid;
	return mf;
}

Job*
newjob(void)
{
	Job *job;

	job = mallocz(sizeof(Job), 1);
	lock(&joblock);
	job->next = joblist;
	joblist = job;
	job->request.tag = -1;
	unlock(&joblock);
	return job;
}

void
freejob(Job *job)
{
	Job **l;

	lock(&joblock);
	for(l = &joblist; *l; l = &(*l)->next){
		if((*l) == job){
			*l = job->next;
			free(job);
			break;
		}
	}
	unlock(&joblock);
}

void
flushjob(int tag)
{
	Job *job;

	lock(&joblock);
	for(job = joblist; job; job = job->next){
		if(job->request.tag == tag && job->request.type != Tflush){
			job->flushed = 1;
			break;
		}
	}
	unlock(&joblock);
}

void
io(void)
{
	long n;
	Mfile *mf;
	int slaveflag;
	uchar mdata[IOHDRSZ + Maxfdata];
	Job *job;

	/*
	 *  if we ask dns to fulfill requests,
	 *  a slave process is created to wait for replies.  The
	 *  master process returns immediately via a longjmp
	 *  through 'masterjmp'.
	 *
	 *  *isslave is a pointer into the call stack to a variable
	 *  that tells whether or not the current process is a slave.
	 */
	slaveflag = 0;		/* init slave variable */
	isslave = &slaveflag;
	setjmp(masterjmp);

	for(;;){
		n = read9pmsg(mfd[0], mdata, sizeof mdata);
		if(n<=0)
			error("mount read");
		job = newjob();
		if(convM2S(mdata, n, &job->request) != n){
			syslog(1, logfile, "format error %ux %ux %ux %ux %ux",
				mdata[0], mdata[1], mdata[2], mdata[3], mdata[4]);
			freejob(job);
			continue;
		}
		lock(&dblock);
		mf = newfid(job->request.fid);
		if(debug)
			syslog(0, logfile, "%F", &job->request);
	
	
		switch(job->request.type){
		default:
			syslog(1, logfile, "unknown request type %d", job->request.type);
			break;
		case Tversion:
			rversion(job);
			break;
		case Tauth:
			rauth(job);
			break;
		case Tflush:
			rflush(job);
			break;
		case Tattach:
			rattach(job, mf);
			break;
		case Twalk:
			rwalk(job, mf);
			break;
		case Topen:
			ropen(job, mf);
			break;
		case Tcreate:
			rcreate(job, mf);
			break;
		case Tread:
			rread(job, mf);
			break;
		case Twrite:
			rwrite(job, mf);
			break;
		case Tclunk:
			rclunk(job, mf);
			break;
		case Tremove:
			rremove(job, mf);
			break;
		case Tstat:
			rstat(job, mf);
			break;
		case Twstat:
			rwstat(job, mf);
			break;
		}
		unlock(&dblock);

		freejob(job);

		/*
		 *  slave processes die after replying
		 */
		if(*isslave){
			if(debug)
				syslog(0, logfile, "slave death %d", getpid());
			_exits(0);
		}
	}
}

void
rversion(Job *job)
{
	if(job->request.msize > IOHDRSZ + Maxfdata)
		job->reply.msize = IOHDRSZ + Maxfdata;
	else
		job->reply.msize = job->request.msize;
	if(strncmp(job->request.version, "9P2000", 6) != 0)
		sendmsg(job, "unknown 9P version");
	else{
		job->reply.version = "9P2000";
		sendmsg(job, 0);
	}
}

void
rauth(Job *job)
{
	sendmsg(job, "cs: authentication not required");
}

/*
 *  don't flush till all the slaves are done
 */
void
rflush(Job *job)
{
	flushjob(job->request.oldtag);
	sendmsg(job, 0);
}

void
rattach(Job *job, Mfile *mf)
{
	if(mf->busy == 0){
		mf->busy = 1;
		mf->user = estrdup(job->request.uname);
	}
	mf->qid.vers = vers++;
	mf->qid.type = QTDIR;
	mf->qid.path = 0LL;
	job->reply.qid = mf->qid;
	sendmsg(job, 0);
}


char*
rwalk(Job *job, Mfile *mf)
{
	char *err;
	char **elems;
	int nelems;
	int i;
	Mfile *nmf;
	Qid qid;

	err = 0;
	nmf = nil;
	elems = job->request.wname;
	nelems = job->request.nwname;
	job->reply.nwqid = 0;

	if(job->request.newfid != job->request.fid){
		/* clone fid */
		nmf = newfid(job->request.newfid);
		if(nmf->busy){
			nmf = nil;
			err = "clone to used channel";
			goto send;
		}
		*nmf = *mf;
		nmf->user = estrdup(mf->user);
		nmf->fid = job->request.newfid;
		nmf->qid.vers = vers++;
		mf = nmf;
	}
	/* else nmf will be nil */

	qid = mf->qid;
	if(nelems > 0){
		/* walk fid */
		for(i=0; i<nelems && i<MAXWELEM; i++){
			if((qid.type & QTDIR) == 0){
				err = "not a directory";
				break;
			}
			if(strcmp(elems[i], "..") == 0 || strcmp(elems[i], ".") == 0){
				qid.type = QTDIR;
				qid.path = Qdir;
    Found:
				job->reply.wqid[i] = qid;
				job->reply.nwqid++;
				continue;
			}
			if(strcmp(elems[i], "cs") == 0){
				qid.type = QTFILE;
				qid.path = Qcs;
				goto Found;
			}
			err = "file does not exist";
			break;
		}
	}

    send:
	if(nmf != nil && (err!=nil || job->reply.nwqid<nelems)){
		cleanmf(nmf);
		free(nmf->user);
		nmf->user = 0;
		nmf->busy = 0;
		nmf->fid = 0;
	}
	if(err == nil)
		mf->qid = qid;
	sendmsg(job, err);
	return err;
}

void
ropen(Job *job, Mfile *mf)