devip.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	"../port/lib.h"
#include	"mem.h"
#include	"dat.h"
#include	"fns.h"
#include	"../port/error.h"
#include	"../ip/ip.h"

enum
{
	Qtopdir=	1,		/* top level directory */
	Qtopbase,
	Qarp=		Qtopbase,
	Qbootp,
	Qndb,
	Qiproute,
	Qipselftab,
	Qlog,

	Qprotodir,			/* directory for a protocol */
	Qprotobase,
	Qclone=		Qprotobase,
	Qstats,

	Qconvdir,			/* directory for a conversation */
	Qconvbase,
	Qctl=		Qconvbase,
	Qdata,
	Qerr,
	Qlisten,
	Qlocal,
	Qremote,
	Qstatus,
	Qsnoop,

	Logtype=	5,
	Masktype=	(1<<Logtype)-1,
	Logconv=	12,
	Maskconv=	(1<<Logconv)-1,
	Shiftconv=	Logtype,
	Logproto=	8,
	Maskproto=	(1<<Logproto)-1,
	Shiftproto=	Logtype + Logconv,

	Nfs=		128,
};
#define TYPE(x) 	( ((ulong)(x).path) & Masktype )
#define CONV(x) 	( (((ulong)(x).path) >> Shiftconv) & Maskconv )
#define PROTO(x) 	( (((ulong)(x).path) >> Shiftproto) & Maskproto )
#define QID(p, c, y) 	( ((p)<<(Shiftproto)) | ((c)<<Shiftconv) | (y) )

static char network[] = "network";

QLock	fslock;
Fs	*ipfs[Nfs];	/* attached fs's */
Queue	*qlog;

extern	void nullmediumlink(void);
extern	void pktmediumlink(void);
	long ndbwrite(Fs *f, char *a, ulong off, int n);

static int
ip3gen(Chan *c, int i, Dir *dp)
{
	Qid q;
	Conv *cv;
	char *p;

	cv = ipfs[c->dev]->p[PROTO(c->qid)]->conv[CONV(c->qid)];
	if(cv->owner == nil)
		kstrdup(&cv->owner, eve);
	mkqid(&q, QID(PROTO(c->qid), CONV(c->qid), i), 0, QTFILE);

	switch(i) {
	default:
		return -1;
	case Qctl:
		devdir(c, q, "ctl", 0, cv->owner, cv->perm, dp);
		return 1;
	case Qdata:
		devdir(c, q, "data", qlen(cv->rq), cv->owner, cv->perm, dp);
		return 1;
	case Qerr:
		devdir(c, q, "err", qlen(cv->eq), cv->owner, cv->perm, dp);
		return 1;
	case Qlisten:
		devdir(c, q, "listen", 0, cv->owner, cv->perm, dp);
		return 1;
	case Qlocal:
		p = "local";
		break;
	case Qremote:
		p = "remote";
		break;
	case Qsnoop:
		if(strcmp(cv->p->name, "ipifc") != 0)
			return -1;
		devdir(c, q, "snoop", qlen(cv->sq), cv->owner, 0400, dp);
		return 1;
	case Qstatus:
		p = "status";
		break;
	}
	devdir(c, q, p, 0, cv->owner, 0444, dp);
	return 1;
}

static int
ip2gen(Chan *c, int i, Dir *dp)
{
	Qid q;

	switch(i) {
	case Qclone:
		mkqid(&q, QID(PROTO(c->qid), 0, Qclone), 0, QTFILE);
		devdir(c, q, "clone", 0, network, 0666, dp);
		return 1;
	case Qstats:
		mkqid(&q, QID(PROTO(c->qid), 0, Qstats), 0, QTFILE);
		devdir(c, q, "stats", 0, network, 0444, dp);
		return 1;
	}
	return -1;
}

static int
ip1gen(Chan *c, int i, Dir *dp)
{
	Qid q;
	char *p;
	int prot;
	int len = 0;
	Fs *f;
	extern ulong	kerndate;

	f = ipfs[c->dev];

	prot = 0666;
	mkqid(&q, QID(0, 0, i), 0, QTFILE);
	switch(i) {
	default:
		return -1;
	case Qarp:
		p = "arp";
		prot = 0664;
		break;
	case Qbootp:
		p = "bootp";
		break;
	case Qndb:
		p = "ndb";
		len = strlen(f->ndb);
		q.vers = f->ndbvers;
		break;
	case Qiproute:
		p = "iproute";
		prot = 0664;
		break;
	case Qipselftab:
		p = "ipselftab";
		prot = 0444;
		break;
	case Qlog:
		p = "log";
		break;
	}
	devdir(c, q, p, len, network, prot, dp);
	if(i == Qndb && f->ndbmtime > kerndate)
		dp->mtime = f->ndbmtime;
	return 1;
}

static int
ipgen(Chan *c, char*, Dirtab*, int, int s, Dir *dp)
{
	Qid q;
	Conv *cv;
	Fs *f;

	f = ipfs[c->dev];

	switch(TYPE(c->qid)) {
	case Qtopdir:
		if(s == DEVDOTDOT){
			mkqid(&q, QID(0, 0, Qtopdir), 0, QTDIR);
			sprint(up->genbuf, "#I%lud", c->dev);
			devdir(c, q, up->genbuf, 0, network, 0555, dp);
			return 1;
		}
		if(s < f->np) {
			if(f->p[s]->connect == nil)
				return 0;	/* protocol with no user interface */
			mkqid(&q, QID(s, 0, Qprotodir), 0, QTDIR);
			devdir(c, q, f->p[s]->name, 0, network, 0555, dp);
			return 1;
		}
		s -= f->np;
		return ip1gen(c, s+Qtopbase, dp);
	case Qarp:
	case Qbootp:
	case Qndb:
	case Qlog:
	case Qiproute:
	case Qipselftab:
		return ip1gen(c, TYPE(c->qid), dp);
	case Qprotodir:
		if(s == DEVDOTDOT){
			mkqid(&q, QID(0, 0, Qtopdir), 0, QTDIR);
			sprint(up->genbuf, "#I%lud", c->dev);
			devdir(c, q, up->genbuf, 0, network, 0555, dp);
			return 1;
		}
		if(s < f->p[PROTO(c->qid)]->ac) {
			cv = f->p[PROTO(c->qid)]->conv[s];
			sprint(up->genbuf, "%d", s);
			mkqid(&q, QID(PROTO(c->qid), s, Qconvdir), 0, QTDIR);
			devdir(c, q, up->genbuf, 0, cv->owner, 0555, dp);
			return 1;
		}
		s -= f->p[PROTO(c->qid)]->ac;
		return ip2gen(c, s+Qprotobase, dp);
	case Qclone:
	case Qstats:
		return ip2gen(c, TYPE(c->qid), dp);
	case Qconvdir:
		if(s == DEVDOTDOT){
			s = PROTO(c->qid);
			mkqid(&q, QID(s, 0, Qprotodir), 0, QTDIR);
			devdir(c, q, f->p[s]->name, 0, network, 0555, dp);
			return 1;
		}
		return ip3gen(c, s+Qconvbase, dp);
	case Qctl:
	case Qdata:
	case Qerr:
	case Qlisten:
	case Qlocal:
	case Qremote:
	case Qstatus:
	case Qsnoop:
		return ip3gen(c, TYPE(c->qid), dp);
	}
	return -1;
}

static void
ipreset(void)
{
	nullmediumlink();
	pktmediumlink();

	fmtinstall('i', eipfmt);
	fmtinstall('I', eipfmt);
	fmtinstall('E', eipfmt);
	fmtinstall('V', eipfmt);
	fmtinstall('M', eipfmt);
}

static Fs*
ipgetfs(int dev)
{
	extern void (*ipprotoinit[])(Fs*);
	Fs *f;
	int i;

	if(dev >= Nfs)
		return nil;

	qlock(&fslock);
	if(ipfs[dev] == nil){
		f = smalloc(sizeof(Fs));
		ip_init(f);
		arpinit(f);
		netloginit(f);
		for(i = 0; ipprotoinit[i]; i++)
			ipprotoinit[i](f);
		f->dev = dev;
		ipfs[dev] = f;
	}
	qunlock(&fslock);

	return ipfs[dev];
}

IPaux*
newipaux(char *owner, char *tag)
{
	IPaux *a;
	int n;

	a = smalloc(sizeof(*a));
	kstrdup(&a->owner, owner);
	memset(a->tag, ' ', sizeof(a->tag));
	n = strlen(tag);
	if(n > sizeof(a->tag))
		n = sizeof(a->tag);
	memmove(a->tag, tag, n);
	return a;
}

#define ATTACHER(c) (((IPaux*)((c)->aux))->owner)

static Chan*
ipattach(char* spec)
{
	Chan *c;
	int dev;

	dev = atoi(spec);
	if(dev >= Nfs)
		error("bad specification");

	ipgetfs(dev);
	c = devattach('I', spec);
	mkqid(&c->qid, QID(0, 0, Qtopdir), 0, QTDIR);
	c->dev = dev;

	c->aux = newipaux(commonuser(), "none");

	return c;
}

static Walkqid*
ipwalk(Chan* c, Chan *nc, char **name, int nname)
{
	IPaux *a = c->aux;
	Walkqid* w;

	w = devwalk(c, nc, name, nname, nil, 0, ipgen);
	if(w != nil && w->clone != nil)
		w->clone->aux = newipaux(a->owner, a->tag);
	return w;
}


static int
ipstat(Chan* c, uchar* db, int n)
{
	return devstat(c, db, n, nil, 0, ipgen);
}

static int
incoming(void* arg)
{
	Conv *conv;

	conv = arg;
	return conv->incall != nil;
}

static int m2p[] = {
	[OREAD]		4,
	[OWRITE]	2,
	[ORDWR]		6
};

static Chan*
ipopen(Chan* c, int omode)
{
	Conv *cv, *nc;
	Proto *p;
	int perm;
	Fs *f;

	perm = m2p[omode&3];

	f = ipfs[c->dev];

	switch(TYPE(c->qid)) {
	default:
		break;
	case Qndb:
		if(omode & (OWRITE|OTRUNC) && !iseve())
			error(Eperm);
		if((omode & (OWRITE|OTRUNC)) == (OWRITE|OTRUNC))
			f->ndb[0] = 0;
		break;
	case Qlog:
		netlogopen(f);
		break;
	case Qiproute:
	case Qarp:
		if(omode != OREAD && !iseve())
			error(Eperm);
		break;
	case Qtopdir:
	case Qprotodir:
	case Qconvdir:
	case Qstatus:
	case Qremote:
	case Qlocal:
	case Qstats:
	case Qbootp:
	case Qipselftab:
		if(omode != OREAD)
			error(Eperm);
		break;
	case Qsnoop:
		if(omode != OREAD)
			error(Eperm);
		p = f->p[PROTO(c->qid)];
		cv = p->conv[CONV(c->qid)];
		if(strcmp(ATTACHER(c), cv->owner) != 0 && !iseve())
			error(Eperm);
		incref(&cv->snoopers);
		break;
	case Qclone:
		p = f->p[PROTO(c->qid)];
		qlock(p);
		if(waserror()){
			qunlock(p);
			nexterror();
		}
		cv = Fsprotoclone(p, ATTACHER(c));
		qunlock(p);
		poperror();
		if(cv == nil) {
			error(Enodev);
			break;
		}
		mkqid(&c->qid, QID(p->x, cv->x, Qctl), 0, QTFILE);
		break;
	case Qdata:
	case Qctl:
	case Qerr:
		p = f->p[PROTO(c->qid)];
		qlock(p);
		cv = p->conv[CONV(c->qid)];
		qlock(cv);
		if(waserror()) {
			qunlock(cv);
			qunlock(p);
			nexterror();
		}
		if((perm & (cv->perm>>6)) != perm) {
			if(strcmp(ATTACHER(c), cv->owner) != 0)
				error(Eperm);
		 	if((perm & cv->perm) != perm)
				error(Eperm);

		}
		cv->inuse++;
		if(cv->inuse == 1){
			kstrdup(&cv->owner, ATTACHER(c));
			cv->perm = 0660;
		}
		qunlock(cv);
		qunlock(p);
		poperror();
		break;
	case Qlisten:
		cv = f->p[PROTO(c->qid)]->conv[CONV(c->qid)];
		if((perm & (cv->perm>>6)) != perm) {
			if(strcmp(ATTACHER(c), cv->owner) != 0)
				error(Eperm);
		 	if((perm & cv->perm) != perm)
				error(Eperm);

		}

		if(cv->state != Announced)
			error("not announced");

		if(waserror()){
			closeconv(cv);
			nexterror();
		}
		qlock(cv);
		cv->inuse++;
		qunlock(cv);

		nc = nil;
		while(nc == nil) {
			/* give up if we got a hangup */
			if(qisclosed(cv->rq))
				error("listen hungup");

			qlock(&cv->listenq);
			if(waserror()) {
				qunlock(&cv->listenq);
				nexterror();
			}

			/* wait for a connect */
			sleep(&cv->listenr, incoming, cv);

			qlock(cv);
			nc = cv->incall;
			if(nc != nil){
				cv->incall = nc->next;
				mkqid(&c->qid, QID(PROTO(c->qid), nc->x, Qctl), 0, QTFILE);
				kstrdup(&cv->owner, ATTACHER(c));
			}
			qunlock(cv);

			qunlock(&cv->listenq);
			poperror();
		}
		closeconv(cv);
		poperror();
		break;
	}
	c->mode = openmode(omode);
	c->flag |= COPEN;
	c->offset = 0;
	return c;
}

static void
ipcreate(Chan*, char*, int, ulong)
{
	error(Eperm);
}

static void
ipremove(Chan*)
{
	error(Eperm);
}

static int
ipwstat(Chan *c, uchar *dp, int n)
{
	Dir d;
	Conv *cv;
	Fs *f;
	Proto *p;

	f = ipfs[c->dev];
	switch(TYPE(c->qid)) {
	default:
		error(Eperm);
		break;
	case Qctl:
	case Qdata:
		break;
	}

	n = convM2D(dp, n, &d, nil);
	if(n > 0){
		p = f->p[PROTO(c->qid)];
		cv = p->conv[CONV(c->qid)];
		if(!iseve() && strcmp(ATTACHER(c), cv->owner) != 0)
			error(Eperm);
		if(d.uid[0])
			kstrdup(&cv->owner, d.uid);
		cv->perm = d.mode & 0777;
	}
	return n;
}

void
closeconv(Conv *cv)
{
	Conv *nc;
	Ipmulti *mp;

	qlock(cv);

	if(--cv->inuse > 0) {
		qunlock(cv);
		return;
	}

	/* close all incoming calls since no listen will ever happen */
	for(nc = cv->incall; nc; nc = cv->incall){
		cv->incall = nc->next;
		closeconv(nc);
	}
	cv->incall = nil;

	kstrdup(&cv->owner, network);
	cv->perm = 0660;

	while((mp = cv->multi) != nil)
		ipifcremmulti(cv, mp->ma, mp->ia);

	cv->r = nil;
	cv->rgen = 0;
	cv->p->close(cv);
	cv->state = Idle;
	qunlock(cv);
}

static void
ipclose(Chan* c)
{
	Fs *f;

	f = ipfs[c->dev];
	switch(TYPE(c->qid)) {
	default:
		break;
	case Qlog:
		if(c->flag & COPEN)
			netlogclose(f);
		break;
	case Qdata:
	case Qctl:
	case Qerr:
		if(c->flag & COPEN)
			closeconv(f->p[PROTO(c->qid)]->conv[CONV(c->qid)]);
		break;
	case Qsnoop:
		if(c->flag & COPEN)
			decref(&f->p[PROTO(c->qid)]->conv[CONV(c->qid)]->snoopers);
		break;
	}
	free(((IPaux*)c->aux)->owner);
	free(c->aux);
}

enum
{
	Statelen=	32*1024,
};

static long
ipread(Chan *ch, void *a, long n, vlong off)
{
	Conv *c;
	Proto *x;
	char *buf, *p;
	long rv;
	Fs *f;
	ulong offset = off;

	f = ipfs[ch->dev];

	p = a;
	switch(TYPE(ch->qid)) {
	default:
		error(Eperm);
	case Qtopdir:
	case Qprotodir:
	case Qconvdir:
		return devdirread(ch, a, n, 0, 0, ipgen);
	case Qarp:
		return arpread(f->arp, a, offset, n);
 	case Qbootp:
 		return bootpread(a, offset, n);
 	case Qndb:
		return readstr(offset, a, n, f->ndb);
	case Qiproute:
		return routeread(f, a, offset, n);
	case Qipselftab:
		return ipselftabread(f, a, offset, n);
	case Qlog:
		return netlogread(f, a, offset, n);
	case Qctl:
		buf = smalloc(16);
		sprint(buf, "%lud", CONV(ch->qid));
		rv = readstr(offset, p, n, buf);
		free(buf);
		return rv;
	case Qremote:
		buf = smalloc(Statelen);
		x = f->p[PROTO(ch->qid)];
		c = x->conv[CONV(ch->qid)];
		if(x->remote == nil) {
			sprint(buf, "%I!%d\n", c->raddr, c->rport);
		} else {
			(*x->remote)(c, buf, Statelen-2);
		}
		rv = readstr(offset, p, n, buf);
		free(buf);
		return rv;
	case Qlocal:
		buf = smalloc(Statelen);
		x = f->p[PROTO(ch->qid)];
		c = x->conv[CONV(ch->qid)];
		if(x->local == nil) {
			sprint(buf, "%I!%d\n", c->laddr, c->lport);
		} else {
			(*x->local)(c, buf, Statelen-2);
		}
		rv = readstr(offset, p, n, buf);
		free(buf);
		return rv;
	case Qstatus:
		buf = smalloc(Statelen);
		x = f->p[PROTO(ch->qid)];
		c = x->conv[CONV(ch->qid)];
		(*x->state)(c, buf, Statelen-2);
		rv = readstr(offset, p, n, buf);
		free(buf);
		return rv;
	case Qdata:
		c = f->p[PROTO(ch->qid)]->conv[CONV(ch->qid)];
		return qread(c->rq, a, n);
	case Qerr:
		c = f->p[PROTO(ch->qid)]->conv[CONV(ch->qid)];
		return qread(c->eq, a, n);
	case Qsnoop:
		c = f->p[PROTO(ch->qid)]->conv[CONV(ch->qid)];
		return qread(c->sq, a, n);
	case Qstats:
		x = f->p[PROTO(ch->qid)];
		if(x->stats == nil)
			error("stats not implemented");
		buf = smalloc(Statelen);
		(*x->stats)(x, buf, Statelen);
		rv = readstr(offset, p, n, buf);
		free(buf);
		return rv;
	}
}

static Block*