devsdp.c

著名操作系统Plan 9的第三版的部分核心源代码。现在很难找到了。Plan 9是bell实验室开发的Unix后继者。

sdpclone(Sdp *sdp)
{
	Conv *c, **pp, **ep;

	c = nil;
	ep = sdp->conv + nelem(sdp->conv);
	qlock(sdp);
	if(waserror()) {
		qunlock(sdp);
		nexterror();
	}
	for(pp = sdp->conv; pp < ep; pp++) {
		c = *pp;
		if(c == nil){
			c = malloc(sizeof(Conv));
			if(c == nil)
				error(Enomem);
			memset(c, 0, sizeof(Conv));
			qlock(c);
			c->sdp = sdp;
			c->id = pp - sdp->conv;
			*pp = c;
			sdp->nconv++;
			break;
		}
		if(c->ref == 0 && canqlock(c)){
			if(c->ref == 0)
				break;
			qunlock(c);
		}
	}
	poperror();
	qunlock(sdp);

	if(pp >= ep)
		return nil;

	assert(c->state == CFree);
	// set ref to 2 - 1 ref for open - 1 ref for channel state
	c->ref = 2;
	c->state = CInit;
	c->in.window = ~0;
	strncpy(c->owner, up->user, sizeof(c->owner));
	c->perm = 0660;
	qunlock(c);

	return c;
}

// assume c is locked
static void
convretryinit(Conv *c)
{
	c->retries = 0;
	// +2 to avoid rounding effects.
	c->timeout = TK2SEC(m->ticks) + 2;
}

// assume c is locked
static int
convretry(Conv *c, int reset)
{
	c->retries++;
	if(c->retries > MaxRetries) {
		if(reset)
			convoconnect(c, ConReset, c->dialid, c->acceptid);
		convsetstate(c, CClosed);
		return 0;
	}
	c->timeout = TK2SEC(m->ticks) + (c->retries+1);
	return 1;
}

// assumes c is locked
static void
convtimer(Conv *c, ulong sec)
{
	Block *b;

	if(c->timeout > sec)
		return;

	switch(c->state) {
	case CInit:
		break;
	case CDial:
		if(convretry(c, 1))
			convoconnect(c, ConOpenRequest, c->dialid, 0);
		break;
	case CAccept:
		if(convretry(c, 1))
			convoconnect(c, ConOpenAck, c->dialid, c->acceptid);
		break;
	case COpen:
		b = c->out.controlpkt;
		if(b != nil) {
			if(convretry(c, 1))
				convoput(c, TControl, ControlMesg, copyblock(b, blocklen(b)));
			break;
		}

		c->timeout = c->lastrecv + KeepAlive;
		if(c->timeout > sec)
			break;
		// keepalive - randomly spaced between KeepAlive and 2*KeepAlive
		if(c->timeout + KeepAlive > sec && nrand(c->lastrecv + 2*KeepAlive - sec) > 0)
			break;
		// can not use writecontrol
		b = allocb(4);
		c->out.controlseq++;
		hnputl(b->wp, c->out.controlseq);
		b->wp += 4;
		c->out.controlpkt = b;
		convretryinit(c);
		if(!waserror()) {
			convoput(c, TControl, ControlMesg, copyblock(b, blocklen(b)));
			poperror();
		}
		break;
	case CLocalClose:
		if(convretry(c, 0))
			convoconnect(c, ConClose, c->dialid, c->acceptid);
		break;
	case CRemoteClose:
	case CClosed:
		break;
	}
}


static void
sdpackproc(void *a)
{
	Sdp *sdp = a;
	ulong sec;
	int i;
	Conv *c;

	for(;;) {
		tsleep(&sdp->vous, return0, 0, 1000);
		sec = TK2SEC(m->ticks);
		qlock(sdp);
		for(i=0; i<sdp->nconv; i++) {
			c = sdp->conv[i];
			if(c->ref == 0)
				continue;
			qunlock(sdp);
			qlock(c);
			if(c->ref > 0 && !waserror()) {
				convtimer(c, sec);
				poperror();
			}
			qunlock(c);
			qlock(sdp);
		}
		qunlock(sdp);
	}
}

Dev sdpdevtab = {
	'E',
	"sdp",

	devreset,
	sdpinit,
	sdpattach,
	devclone,
	sdpwalk,
	sdpstat,
	sdpopen,
	devcreate,
	sdpclose,
	sdpread,
	devbread,
	sdpwrite,
	devbwrite,
	devremove,
	devwstat,
};

// assume hold lock on c
static void
convsetstate(Conv *c, int state)
{

if(1)print("convsetstate %d: %s -> %s\n", c->id, convstatename[c->state], convstatename[state]);

	switch(state) {
	default:
		panic("setstate: bad state: %d", state);
	case CDial:
		assert(c->state == CInit);
		c->dialid = (rand()<<16) + rand();
		convretryinit(c);
		convoconnect(c, ConOpenRequest, c->dialid, 0);
		break;
	case CAccept:
		assert(c->state == CInit);
		c->acceptid = (rand()<<16) + rand();
		convretryinit(c);
		convoconnect(c, ConOpenAck, c->dialid, c->acceptid);
		break;
	case COpen:
		assert(c->state == CDial || c->state == CAccept);
		c->lastrecv = TK2SEC(m->ticks);
		if(c->state == CDial) {
			convretryinit(c);
			convoconnect(c, ConOpenAckAck, c->dialid, c->acceptid);
			hnputl(c->in.secret, c->acceptid);
			hnputl(c->in.secret+4, c->dialid);
			hnputl(c->out.secret, c->dialid);
			hnputl(c->out.secret+4, c->acceptid);
		} else {
			hnputl(c->in.secret, c->dialid);
			hnputl(c->in.secret+4, c->acceptid);
			hnputl(c->out.secret, c->acceptid);
			hnputl(c->out.secret+4, c->dialid);
		}
		setalg(c, "hmac_md5_96", authalg, &c->auth);
		break;
	case CLocalClose:
		assert(c->state == CAccept || c->state == COpen);
		convretryinit(c);
		convoconnect(c, ConClose, c->dialid, c->acceptid);
		break;
	case CRemoteClose:
		wakeup(&c->in.controlready);
		wakeup(&c->out.controlready);
		break;
	case CClosed:
		wakeup(&c->in.controlready);
		wakeup(&c->out.controlready);
		if(c->readproc)
			postnote(c->readproc, 1, "interrupt", 0);
		if(c->state != CClosed)
			convderef(c);
		break;
	}
	c->state = state;
}


//assumes c is locked
static void
convderef(Conv *c)
{
	c->ref--;
	if(c->ref > 0) {
		return;
	}
	assert(c->ref == 0);
	assert(c->dataopen == 0);
	assert(c->controlopen == 0);
if(0)print("convderef: %d: ref == 0!\n", c->id);
	c->state = CFree;
	if(c->chan) {	
		cclose(c->chan);
		c->chan = nil;
	}
	if(c->channame) {
		free(c->channame);
		c->channame = nil;
	}
	c->cipher = nil;
	c->auth = nil;
	c->comp = nil;
	strcpy(c->owner, "network");
	c->perm = 0660;
	c->dialid = 0;
	c->acceptid = 0;
	c->timeout = 0;
	c->retries = 0;
	c->drop = 0;
	onewaycleanup(&c->in);
	onewaycleanup(&c->out);
	memset(&c->lstats, 0, sizeof(Stats));
	memset(&c->rstats, 0, sizeof(Stats));
}

static void
onewaycleanup(OneWay *ow)
{
	if(ow->controlpkt)
		freeb(ow->controlpkt);
	if(ow->authstate)
		free(ow->authstate);
	if(ow->cipherstate)
		free(ow->cipherstate);
	if(ow->compstate)
		free(ow->compstate);
	memset(ow, 0, sizeof(OneWay));
}


// assumes conv is locked
static void
convopenchan(Conv *c, char *path)
{
	if(c->state != CInit || c->chan != nil)
		error("already connected");
	c->chan = namec(path, Aopen, ORDWR, 0);
	c->channame = smalloc(strlen(path)+1);
	strcpy(c->channame, path);
	if(waserror()) {
		cclose(c->chan);
		c->chan = nil;
		free(c->channame);
		c->channame = nil;
		nexterror();
	}
	kproc("convreader", convreader, c);

	assert(c->reader == 0 && c->ref > 0);
	// after kproc in case it fails
	c->reader = 1;
	c->ref++;

	poperror();
}

static void
convstats(Conv *c, int local, char *buf, int n)
{
	Stats *stats;
	char *p, *ep;
	int i;

	if(local) {
		stats = &c->lstats;
	} else {
		if(!waserror()) {
			writecontrol(c, 0, 0, 1);
			poperror();
		}
		stats = &c->rstats;
	}

	qlock(c);
	p = buf;
	ep = buf + n;
	p += snprint(p, ep-p, "outPackets: %lud\n", stats->outPackets);
	p += snprint(p, ep-p, "outDataPackets: %lud\n", stats->outDataPackets);
	p += snprint(p, ep-p, "outDataBytes: %lud\n", stats->outDataBytes);
	p += snprint(p, ep-p, "outCompDataBytes: %lud\n", stats->outCompDataBytes);
	for(i=0; i<NCompStats; i++) {
		if(stats->outCompStats[i] == 0)
			continue;
		p += snprint(p, ep-p, "outCompStats[%d]: %lud\n", i, stats->outCompStats[i]);
	}
	p += snprint(p, ep-p, "inPackets: %lud\n", stats->inPackets);
	p += snprint(p, ep-p, "inDataPackets: %lud\n", stats->inDataPackets);
	p += snprint(p, ep-p, "inDataBytes: %lud\n", stats->inDataBytes);
	p += snprint(p, ep-p, "inCompDataBytes: %lud\n", stats->inCompDataBytes);
	p += snprint(p, ep-p, "inMissing: %lud\n", stats->inMissing);
	p += snprint(p, ep-p, "inDup: %lud\n", stats->inDup);
	p += snprint(p, ep-p, "inReorder: %lud\n", stats->inReorder);
	p += snprint(p, ep-p, "inBadComp: %lud\n", stats->inBadComp);
	p += snprint(p, ep-p, "inBadAuth: %lud\n", stats->inBadAuth);
	p += snprint(p, ep-p, "inBadSeq: %lud\n", stats->inBadSeq);
	p += snprint(p, ep-p, "inBadOther: %lud\n", stats->inBadOther);
	USED(p);
	qunlock(c);
}

// c is locked
static void
convack(Conv *c)
{
	Block *b;
	AckPkt *ack;
	Stats *s;
	int i;

	b = allocb(sizeof(AckPkt));
	ack = (AckPkt*)b->wp;
	b->wp += sizeof(AckPkt);
	s = &c->lstats;
	hnputl(ack->cseq, c->in.controlseq);
	hnputl(ack->outPackets, s->outPackets);
	hnputl(ack->outDataPackets, s->outDataPackets);
	hnputl(ack->outDataBytes, s->outDataBytes);
	hnputl(ack->outCompDataBytes, s->outCompDataBytes);
	for(i=0; i<NCompStats; i++)
		hnputl(ack->outCompStats+i*4, s->outCompStats[i]);
	hnputl(ack->inPackets, s->inPackets);
	hnputl(ack->inDataPackets, s->inDataPackets);
	hnputl(ack->inDataBytes, s->inDataBytes);
	hnputl(ack->inCompDataBytes, s->inCompDataBytes);
	hnputl(ack->inMissing, s->inMissing);
	hnputl(ack->inDup, s->inDup);
	hnputl(ack->inReorder, s->inReorder);
	hnputl(ack->inBadComp, s->inBadComp);
	hnputl(ack->inBadAuth, s->inBadAuth);
	hnputl(ack->inBadSeq, s->inBadSeq);
	hnputl(ack->inBadOther, s->inBadOther);
	convoput(c, TControl, ControlAck, b);
}


// assume we hold lock for c
static Block *
conviput(Conv *c, Block *b, int control)
{
	int type, subtype;
	ulong seq, seqwrap;
	long seqdiff;
	int pad;

	c->lstats.inPackets++;

	if(BLEN(b) < 4) {
		c->lstats.inBadOther++;
		freeb(b);
		return nil;
	}
	
	type = b->rp[0] >> 4;
	subtype = b->rp[0] & 0xf;
	b->rp += 1;
	if(type == TConnect) {
		conviconnect(c, subtype, b);
		return nil;
	}

	switch(c->state) {
	case CInit:
	case CDial:
		c->lstats.inBadOther++;
		convoconnect(c, ConReset, c->dialid, c->acceptid);
		convsetstate(c, CClosed);
		break;
	case CAccept:
	case CRemoteClose:
	case CLocalClose:
		c->lstats.inBadOther++;
		freeb(b);
		return nil;
	}

	seq = (b->rp[0]<<16) + (b->rp[1]<<8) + b->rp[2];
	b->rp += 3;

	seqwrap = c->in.seqwrap;
	seqdiff = seq - c->in.seq;
	if(seqdiff < -(SeqMax*3/4)) {
		seqwrap++;
		seqdiff += SeqMax;
	} else if(seqdiff > SeqMax*3/4) {
		seqwrap--;
		seqdiff -= SeqMax;
	}

	if(seqdiff <= 0) {
		if(seqdiff <= -SeqWindow) {
print("old sequence number: %ld (%ld %ld)\n", seq, c->in.seqwrap, seqdiff);
			c->lstats.inBadSeq++;
			freeb(b);
			return nil;
		}

		if(c->in.window & (1<<-seqdiff)) {
print("dup sequence number: %ld (%ld %ld)\n", seq, c->in.seqwrap, seqdiff);
			c->lstats.inDup++;
			freeb(b);
			return nil;
		}

		c->lstats.inReorder++;
	}

	// ok the sequence number looks ok
if(0) print("coniput seq=%ulx\n", seq);
	if(c->in.auth != 0) {
		if(!(*c->in.auth)(&c->in, b->rp-4, BLEN(b)+4)) {
print("bad auth %ld\n", BLEN(b)+4);
			c->lstats.inBadAuth++;
			freeb(b);
			return nil;
		}
		b->wp -= c->in.authlen;
	}

	if(c->in.cipher != 0) {
		if(!(*c->in.cipher)(&c->in, b->rp, BLEN(b))) {
print("bad cipher\n");
			c->lstats.inBadOther++;
			freeb(b);
			return nil;
		}
		b->rp += c->in.cipherivlen;
		if(c->in.cipherblklen > 1) {
			pad = b->wp[-1];
			if(pad > BLEN(b)) {
print("pad too big\n");
				c->lstats.inBadOther++;
				freeb(b);
				return nil;
			}
			b->wp -= pad;
		}
	}

	// ok the packet is good
	if(seqdiff > 0) {
		while(seqdiff > 0 && c->in.window != 0) {
			if((c->in.window & (1<<(SeqWindow-1))) == 0) {
//print("missing packet: %ld\n", seq - seqdiff);
				c->lstats.inMissing++;
			}
			c->in.window <<= 1;
			seqdiff--;
		}
		if(seqdiff > 0) {
//print("missing packets: %ld-%ld\n", seq - SeqWindow - seqdiff+1, seq-SeqWindow);
			c->lstats.inMissing += seqdiff;
		}
		c->in.seq = seq;
		c->in.seqwrap = seqwrap;
		c->in.window |= 1;
	}
	c->lastrecv = TK2SEC(m->ticks);

	switch(type) {
	case TControl:
		convicontrol(c, subtype, b);
		return nil;
	case TData:
		c->lstats.inDataPackets++;
		c->lstats.inDataBytes += BLEN(b);
		if(control)
			break;
		return b;
	case TCompData:
		c->lstats.inDataPackets++;
		c->lstats.inCompDataBytes += BLEN(b);
		b = convicomp(c, subtype, seq, b);
		if(b == nil) {
			c->lstats.inBadComp++;
			return nil;
		}
		c->lstats.inDataBytes += BLEN(b);
		if(control)
			break;
		return b;
	}
print("droping packet %d n=%ld\n", type, BLEN(b));
	c->lstats.inBadOther++;
	freeb(b);
	return nil;
}

// assume hold conv lock
static void
conviconnect(Conv *c, int subtype, Block *b)
{
	ulong dialid;
	ulong acceptid;

	if(BLEN(b) != 8) {
		freeb(b);
		return;
	}
	dialid = nhgetl(b->rp);
	acceptid = nhgetl(b->rp + 4);
	freeb(b);

if(0)print("conviconnect: %s: %d %uld %uld\n", convstatename[c->state], subtype, dialid, acceptid);

	if(subtype == ConReset) {
		convsetstate(c, CClosed);
		return;
	}

	switch(c->state) {
	default:
		panic("unknown state: %d", c->state);
	case CInit:
		break;
	case CDial:
		if(dialid != c->dialid)
			goto Reset;
		break;
	case CAccept:
	case COpen:
	case CLocalClose:
	case CRemoteClose:
		if(dialid != c->dialid
		|| subtype != ConOpenRequest && acceptid != c->acceptid)
			goto Reset;
		break;
	case CClosed:
		goto Reset;
	}

	switch(subtype) {
	case ConOpenRequest:
		switch(c->state) {
		case CInit:
			c->dialid = dialid;
			convsetstate(c, CAccept);
			return;
		case CAccept:
		case COpen:
			// duplicate ConOpenRequest that we ignore
			return;
		}
		break;
	case ConOpenAck:
		switch(c->state) {
		case CDial:
			c->acceptid = acceptid;
			convsetstate(c, COpen);
			return;
		case COpen:
			// duplicate that we have to ack
			convoconnect(c, ConOpenAckAck, acceptid, dialid);
			return;
		}
		break;
	case ConOpenAckAck:
		switch(c->state) {
		case CAccept:
			convsetstate(c, COpen);
			return;
		case COpen:
		case CLocalClose:
		case CRemoteClose:
			// duplicate that we ignore
			return;
		}
		break;
	case ConClose:
		switch(c->state) {
		case COpen:
			convoconnect(c, ConCloseAck, dialid, acceptid);
			convsetstate(c, CRemoteClose);
			return;
		case CRemoteClose:
			// duplicate ConClose
			convoconnect(c, ConCloseAck, dialid, acceptid);
			return;
		}
		break;
	case ConCloseAck:
		switch(c->state) {
		case CLocalClose:
			convsetstate(c, CClosed);
			return;
		}
		break;
	}
Reset:
	// invalid connection message - reset to sender
if(0)print("invalid conviconnect - sending reset\n");
	convoconnect(c, ConReset, dialid, acceptid);
	convsetstate(c, CClosed);
}

static void
convicontrol(Conv *c, int subtype, Block *b)
{
	ulong cseq;
	AckPkt *ack;
	int i;

	if(BLEN(b) < 4)
		return;
	cseq = nhgetl(b->rp);
	
	switch(subtype){
	case ControlMesg:
		if(cseq == c->in.controlseq) {
print("duplicate control packet: %ulx\n", cseq);
			// duplicate control packet
			freeb(b);
			if(c->in.controlpkt == nil)
				convack(c);
			return;
		}

		if(cseq != c->in.controlseq+1)
			return;
		c->in.controlseq = cseq;
		b->rp += 4;
		if(BLEN(b) == 0) {
			// just a ping
			freeb(b);
			convack(c);
		} else {
			c->in.controlpkt = b;
if(0) print("recv %ld size=%ld\n", cseq, BLEN(b));
			wakeup(&c->in.controlready);
		}
		return;
	case ControlAck:
		if(cseq != c->out.controlseq)
			return;
		if(BLEN(b) < sizeof(AckPkt))
			return;
		ack = (AckPkt*)(b->rp);
		c->rstats.outPackets = nhgetl(ack->outPackets);
		c->rstats.outDataPackets = nhgetl(ack->outDataPackets);
		c->rstats.outDataBytes = nhgetl(ack->outDataBytes);
		c->rstats.outCompDataBytes = nhgetl(ack->outCompDataBytes);
		for(i=0; i<NCompStats; i++)
			c->rstats.outCompStats[i] = nhgetl(ack->outCompStats + 4*i);
		c->rstats.inPackets = nhgetl(ack->inPackets);
		c->rstats.inDataPackets = nhgetl(ack->inDataPackets);
		c->rstats.inDataBytes = nhgetl(ack->inDataBytes);
		c->rstats.inCompDataBytes = nhgetl(ack->inCompDataBytes);
		c->rstats.inMissing = nhgetl(ack->inMissing);
		c->rstats.inDup = nhgetl(ack->inDup);
		c->rstats.inReorder = nhgetl(ack->inReorder);
		c->rstats.inBadComp = nhgetl(ack->inBadComp);
		c->rstats.inBadAuth = nhgetl(ack->inBadAuth);
		c->rstats.inBadSeq = nhgetl(ack->inBadSeq);
		c->rstats.inBadOther = nhgetl(ack->inBadOther);
		freeb(b);
		freeb(c->out.controlpkt);
		c->out.controlpkt = nil;
		c->timeout = c->lastrecv + KeepAlive;
		wakeup(&c->out.controlready);
		return;
	}
}

static Block*
convicomp(Conv *c, int subtype, ulong seq, Block *b)
{
	if(c->in.comp == nil) {
		freeb(b);
		return nil;
	}
	if(!(*c->in.comp)(c, subtype, seq, &b))
		return nil;
	return b;
}

// c is locked
static void
convwriteblock(Conv *c, Block *b)
{
	// simulated errors
	if(c->drop && nrand(c->drop) == 0)
		return;

	if(waserror()) {
		convsetstate(c, CClosed);
		nexterror();
	}
	devtab[c->chan->type]->bwrite(c->chan, b, 0);
	poperror();
}


// assume hold conv lock
static void
convoput(Conv *c, int type, int subtype, Block *b)
{
	int pad;
	
	c->lstats.outPackets++;
	/* Make room for sdp trailer */
	if(c->out.cipherblklen > 1)
		pad = c->out.cipherblklen - (BLEN(b) + c->out.cipherivlen) % c->out.cipherblklen;
	else
		pad = 0;

	b = padblock(b, -(pad+c->out.authlen));

	if(pad) {
		memset(b->wp, 0, pad-1);