ppp.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

	av[0] = "dns";
	av[1] = "wins";
	sprint(ip, "%I", ppp->local);
	t = csipinfo(ppp->net, "ip", ip, av, 2);
	ndns = nwins = 0;
	for(nt = t; nt != nil; nt = nt->entry){
		if(strcmp(nt->attr, "dns") == 0){
			if(ndns < 2)
				parseip(ppp->dns[ndns++], nt->val);
		} else if(strcmp(nt->attr, "wins") == 0){
			if(nwins < 2)
				parseip(ppp->wins[nwins++], nt->val);
		}
	}
	if(t != nil)
		ndbfree(t);
}

/*
 *  parse configuration request, sends an ack or reject packet
 *
 *	returns:	-1 if request was syntacticly incorrect
 *			 0 if packet was accepted
 *			 1 if packet was rejected
 */
static int
getopts(PPP *ppp, Pstate *p, Block *b)
{
	Lcpmsg *m, *repm;	
	Lcpopt *o;
	uchar *cp, *ap;
	ulong rejecting, nacking, flags, proto, chapproto;
	ulong mtu, ctlmap, period;
	ulong x;
	Block *repb;
	Comptype *ctype;
	Ipaddr ipaddr;

	rejecting = 0;
	nacking = 0;
	flags = 0;

	/* defaults */
	invalidate(ipaddr);
	mtu = ppp->mtu;
	ctlmap = 0xffffffff;
	period = 0;
	ctype = nil;
	chapproto = 0;

	m = (Lcpmsg*)b->rptr;
	repb = alloclcp(Lconfack, m->id, BLEN(b), &repm);

	/* copy options into ack packet */
	memmove(repm->data, m->data, b->wptr - m->data);
	repb->wptr += b->wptr - m->data;

	/* look for options we don't recognize or like */
	for(cp = m->data; cp < b->wptr; cp += o->len){
		o = (Lcpopt*)cp;
		if(cp + o->len > b->wptr || o->len==0){
			freeb(repb);
			netlog("ppp: bad option length %ux\n", o->type);
			return -1;
		}

		switch(p->proto){
		case Plcp:
			switch(o->type){
			case Oac:
				flags |= Fac;
				continue;
			case Opc:
				flags |= Fpc;
				continue;
			case Omtu:
				mtu = nhgets(o->data);
				continue;
			case Omagic:
				if(ppp->magic == nhgetl(o->data))
					netlog("ppp: possible loop\n");
				continue;
			case Octlmap:
				ctlmap = nhgetl(o->data);
				continue;
			case Oquality:
				proto = nhgets(o->data);
				if(proto != Plqm)
					break;
				x = nhgetl(o->data+2)*10;
				period = (x+Period-1)/Period;
				continue;
			case Oauth:
				proto = nhgets(o->data);
				if(proto == Ppasswd && !server){
					chapproto = APpasswd;
					continue;
				}
				if(proto != Pchap)
					break;
				if(o->data[2] != APmd5 && o->data[2] != APmschap)
					break;
				chapproto = o->data[2];
				continue;
			}
			break;
		case Pccp:
			if(nocompress)
				break;
			switch(o->type){
			case Octhwack:
				break;
			/*
				if(o->len == 2){
					ctype = &cthwack;
					continue;
				}
				if(!nacking){
					nacking = 1;
					repb->wptr = repm->data;
					repm->code = Lconfnak;
				}
				puto(repb, Octhwack);
				continue;
			*/
			case Ocmppc:
				x = nhgetl(o->data);

				// hack for Mac
				// if(x == 0)
				//	continue;

				/* stop ppp loops */
				if((x&0x41) == 0 || ppp->ctries++ > 5) {
					/*
					 * turn off requests as well - I don't think this
					 * is needed in the standard
					 */
					p->optmask &= ~Fcmppc;
					break;
				}
				if(rejecting)
					continue;
				if(x & 1) {
					ctype = &cmppc;
					ppp->sendencrypted = (o->data[3]&0x40) == 0x40;
					continue;
				}
				if(!nacking){
					nacking = 1;
					repb->wptr = repm->data;
					repm->code = Lconfnak;
				}
				*repb->wptr++ = Ocmppc;
				*repb->wptr++ = 6;
				*repb->wptr++ = 0;
				*repb->wptr++ = 0;
				*repb->wptr++ = 0;
				*repb->wptr++ = 0x41;
				continue;
			}
			break;
		case Pipcp:
			switch(o->type){
			case Oipaddr:	
				v4tov6(ipaddr, o->data);
				if(!validv4(ppp->remote))
					continue;
				if(!validv4(ipaddr) && !rejecting){
					/* other side requesting an address */
					if(!nacking){
						nacking = 1;
						repb->wptr = repm->data;
						repm->code = Lconfnak;
					}
					putv4o(repb, Oipaddr, ppp->remote);
				}
				continue;
			case Oipdns:
				ap = ppp->dns[0];
				goto ipinfo;
			case Oipdns2:	
				ap = ppp->dns[1];
				goto ipinfo;
			case Oipwins:	
				ap = ppp->wins[0];
				goto ipinfo;
			case Oipwins2:
				ap = ppp->wins[1];
				goto ipinfo;
			ipinfo:
				if(!validv4(ap))
					getipinfo(ppp);
				if(!validv4(ap))
					break;
				v4tov6(ipaddr, o->data);
				if(!validv4(ipaddr) && !rejecting){
					/* other side requesting an address */
					if(!nacking){
						nacking = 1;
						repb->wptr = repm->data;
						repm->code = Lconfnak;
					}
					putv4o(repb, o->type, ap);
				}
				continue;
			case Oipcompress:
				/*
				 * don't compress tcp header if we've negotiated data compression.
				 * tcp header compression has very poor performance if there is an error.
				 */
				proto = nhgets(o->data);
				if(noipcompress || proto != Pvjctcp || ppp->ctype != nil)
					break;
				if(compress_negotiate(ppp->ctcp, o->data+2) < 0)
					break;
				flags |= Fipcompress;
				continue;
			}
			break;
		}

		/* come here if option is not recognized */
		if(!rejecting){
			rejecting = 1;
			repb->wptr = repm->data;
			repm->code = Lconfrej;
		}
		netlog("ppp: bad %ux option %d\n", p->proto, o->type);
		memmove(repb->wptr, o, o->len);
		repb->wptr += o->len;
	}

	/* permanent changes only after we know that we liked the packet */
	if(!rejecting && !nacking){
		switch(p->proto){
		case Plcp:
			ppp->period = period;
			ppp->xctlmap = ctlmap;
			if(mtu > Maxmtu)
				mtu = Maxmtu;
			if(mtu < Minmtu)
				mtu = Minmtu;
			ppp->mtu = mtu;
			if(chapproto)
				ppp->chap->proto = chapproto;
			
			break;
		case Pccp:
			if(ppp->ctype != nil){
				(*ppp->ctype->fini)(ppp->cstate);
				ppp->cstate = nil;
			}
			ppp->ctype = ctype;
			if(ctype)
				ppp->cstate = (*ctype->init)(ppp);
			break;
		case Pipcp:
			if(validv4(ipaddr) && ppp->remotefrozen == 0)
 				ipmove(ppp->remote, ipaddr);
			break;
		}
		p->flags = flags;
	}

	hnputs(repm->len, BLEN(repb));
	printopts(p, repb, 1);
	putframe(ppp, p->proto, repb);
	freeb(repb);

	return rejecting || nacking;
}
static void
dmppkt(char *s, uchar *a, int na)
{
	int i;

	if (debug < 3)
		return;

	fprint(2, "%s", s);
	for(i = 0; i < na; i++)
		fprint(2, " %.2ux", a[i]);
	fprint(2, "\n");
}

static void
dropoption(Pstate *p, Lcpopt *o)
{
	unsigned n = o->type;

	switch(n){
		case Oipdns:
			p->optmask &= ~Fipdns;
			break;
		case Oipwins:
			p->optmask &= ~Fipwins;
			break;
		case Oipdns2:
			p->optmask &= ~Fipdns2;
			break;
		case Oipwins2:
			p->optmask &= ~Fipwins2;
			break;
		default:
			if(o->type < 8*sizeof(p->optmask))
				p->optmask &= ~(1<<o->type);
			break;
	}
}

/*
 *  parse configuration rejection, just stop sending anything that they
 *  don't like (except for ipcp address nak).
 */
static void
rejopts(PPP *ppp, Pstate *p, Block *b, int code)
{
	Lcpmsg *m;
	Lcpopt *o;
	uchar newip[IPaddrlen];

	/* just give up trying what the other side doesn't like */
	m = (Lcpmsg*)b->rptr;
	for(b->rptr = m->data; b->rptr < b->wptr; b->rptr += o->len){
		o = (Lcpopt*)b->rptr;
		if(b->rptr + o->len > b->wptr){
			netlog("ppp: bad roption length %ux\n", o->type);
			return;
		}

		if(code == Lconfrej){
			dropoption(p, o);
			netlog("ppp: %ux rejecting %d\n",
					p->proto, o->type);
			continue;
		}

		switch(p->proto){
		case Plcp:
			switch(o->type){
			case Octlmap:
				ppp->rctlmap = nhgetl(o->data);
				break;
			case Oauth:
				/* don't allow client to request no auth */
				/* could try different auth protocol here */
				fprint(2, "ppp: can not reject CHAP\n");
				exits("ppp: CHAP");
				break;
			default:
				if(o->type < 8*sizeof(p->optmask))
					p->optmask &= ~(1<<o->type);
				break;
			};
			break;
		case Pccp:
			switch(o->type){
			default:
				dropoption(p, o);
				break;
			}
			break;
		case Pipcp:
			switch(o->type){
			case Oipaddr:
syslog(0, "ppp", "rejected addr %I with %V", ppp->local, o->data);
				/* if we're a server, don't let other end change our addr */
				if(ppp->localfrozen){
					dropoption(p, o);
					break;
				}

				/* accept whatever server tells us */
				if(!validv4(ppp->local)){
					v4tov6(ppp->local, o->data);
					dropoption(p, o);
					break;
				}

				/* if he didn't like our addr, ask for a generic one */
				v4tov6(newip, o->data);
				if(!validv4(newip)){
					invalidate(ppp->local);
					break;
				}

				/* if he gives us something different, use it anyways */
				v4tov6(ppp->local, o->data);
				dropoption(p, o);
				break;
			case Oipdns:
				if (!validv4(ppp->dns[0])){
					v4tov6(ppp->dns[0], o->data);
					dropoption(p, o);
					break;
				}
				v4tov6(newip, o->data);
				if(!validv4(newip)){
					invalidate(ppp->dns[0]);
					break;
				}
				v4tov6(ppp->dns[0], o->data);
				dropoption(p, o);
				break;
			case Oipwins:
				if (!validv4(ppp->wins[0])){
					v4tov6(ppp->wins[0], o->data);
					dropoption(p, o);
					break;
				}
				v4tov6(newip, o->data);
				if(!validv4(newip)){
					invalidate(ppp->wins[0]);
					break;
				}
				v4tov6(ppp->wins[0], o->data);
				dropoption(p, o);
				break;
			case Oipdns2:
				if (!validv4(ppp->dns[1])){
					v4tov6(ppp->dns[1], o->data);
					dropoption(p, o);
					break;
				}
				v4tov6(newip, o->data);
				if(!validv4(newip)){
					invalidate(ppp->dns[1]);
					break;
				}
				v4tov6(ppp->dns[1], o->data);
				dropoption(p, o);
				break;
			case Oipwins2:
				if (!validv4(ppp->wins[1])){
					v4tov6(ppp->wins[1], o->data);
					dropoption(p, o);
					break;
				}
				v4tov6(newip, o->data);
				if(!validv4(newip)){
					invalidate(ppp->wins[1]);
					break;
				}
				v4tov6(ppp->wins[1], o->data);
				dropoption(p, o);
				break;
			default:
				dropoption(p, o);
				break;
			}
			break;
		}
	}
}


/*
 *  put a messages through the lcp or ipcp state machine.  They are
 *  very similar.
 */
static void
rcv(PPP *ppp, Pstate *p, Block *b)
{
	ulong len;
	int err;
	Lcpmsg *m;
	int proto;

	if(BLEN(b) < 4){
		netlog("ppp: short lcp message\n");
		freeb(b);
		return;
	}
	m = (Lcpmsg*)b->rptr;
	len = nhgets(m->len);
	if(BLEN(b) < len){
		netlog("ppp: short lcp message\n");
		freeb(b);
		return;
	}

	netlog("ppp: %ux rcv %d len %ld id %d/%d/%d\n",
		p->proto, m->code, len, m->id, p->confid, p->id);

	if(p->proto != Plcp && ppp->lcp->state != Sopened){
		netlog("ppp: non-lcp with lcp not open\n");
		freeb(b);
		return;
	}

	qlock(ppp);
	switch(m->code){
	case Lconfreq:
		printopts(p, b, 0);
		err = getopts(ppp, p, b);
		if(err < 0)
			break;

		if(m->id == p->rcvdconfid)
			break;			/* don't change state for duplicates */

		switch(p->state){
		case Sackrcvd:
			if(err)
				break;
			newstate(ppp, p, Sopened);
			break;
		case Sclosed:
		case Sopened:
			config(ppp, p, 1);
			if(err == 0)
				newstate(ppp, p, Sacksent);
			else
				newstate(ppp, p, Sreqsent);
			break;
		case Sreqsent:
		case Sacksent:
			if(err == 0)
				newstate(ppp, p, Sacksent);
			else
				newstate(ppp, p, Sreqsent);
			break;
		}
		break;
	case Lconfack:
		if(p->confid != m->id){
			/* ignore if it isn't the message we're sending */
			netlog("ppp: dropping confack\n");
			break;
		}
		p->confid = -1;		/* ignore duplicates */
		p->id++;		/* avoid sending duplicates */

		netlog("ppp: recv confack\n");
		switch(p->state){
		case Sopened:
		case Sackrcvd:
			config(ppp, p, 1);
			newstate(ppp, p, Sreqsent);
			break;
		case Sreqsent:
			newstate(ppp, p, Sackrcvd);
			break;
		case Sacksent:
			newstate(ppp, p, Sopened);
			break;
		}
		break;
	case Lconfrej:
	case Lconfnak:
		if(p->confid != m->id) {
			/* ignore if it isn't the message we're sending */
			netlog("ppp: dropping confrej or confnak\n");
			break;
		}
		p->confid = -1;		/* ignore duplicates */
		p->id++;		/* avoid sending duplicates */

		switch(p->state){
		case Sopened:
		case Sackrcvd:
			config(ppp, p, 1);
			newstate(ppp, p, Sreqsent);
			break;
		case Sreqsent:
		case Sacksent:
			printopts(p, b, 0);
			rejopts(ppp, p, b, m->code);
			config(ppp, p, 1);
			break;
		}
		break;
	case Ltermreq:
		m->code = Ltermack;
		putframe(ppp, p->proto, b);

		switch(p->state){
		case Sackrcvd:
		case Sacksent:
			newstate(ppp, p, Sreqsent);
			break;
		case Sopened:
			newstate(ppp, p, Sclosing);
			break;
		}
		break;
	case Ltermack:
		if(p->termid != m->id)	/* ignore if it isn't the message we're sending */
			break;

		if(p->proto == Plcp)
			ppp->ipcp->state = Sclosed;
		switch(p->state){
		case Sclosing:
			newstate(ppp, p, Sclosed);
			break;
		case Sackrcvd:
			newstate(ppp, p, Sreqsent);
			break;
		case Sopened:
			config(ppp, p, 0);
			newstate(ppp, p, Sreqsent);
			break;
		}
		break;
	case Lcoderej:
		//newstate(ppp, p, Sclosed);
		syslog(0, LOG, "code reject %d\n", m->data[0]);
		break;
	case Lprotorej:
		proto = nhgets(m->data);
		netlog("ppp: proto reject %ux\n", proto);
		if(proto == Pccp)
			newstate(ppp, ppp->ccp, Sclosed);
		break;
	case Lechoreq:
		if(BLEN(b) < 8){
			netlog("ppp: short lcp echo request\n");
			freeb(b);
			return;
		}
		m->code = Lechoack;
		hnputl(m->data, ppp->magic);
		putframe(ppp, p->proto, b);
		break;
	case Lechoack:
		p->echoack = 1;
		break;
	case Ldiscard:
		/* nothing to do */
		break;
	case Lresetreq:
		if(p->proto != Pccp)
			break;
		ppp->stat.compreset++;
		if(ppp->ctype != nil)
			b = (*ppp->ctype->resetreq)(ppp->cstate, b);
		if(b != nil) {
			m = (Lcpmsg*)b->rptr;
			m->code = Lresetack;
			putframe(ppp, p->proto, b);
		}
		break;
	case Lresetack:
		if(p->proto != Pccp)
			break;
		if(ppp->unctype != nil)
			(*ppp->unctype->resetack)(ppp->uncstate, b);
		break;
	}

	qunlock(ppp);
	freeb(b);
}

/*
 *  timer for protocol state machine
 */
static void
ptimer(PPP *ppp, Pstate *p)
{
	if(p->state == Sopened || p->state == Sclosed)
		return;

	p->timeout--;
	switch(p->state){
	case Sclosing:
		sendtermreq(ppp, p);
		break;
	case Sreqsent:
	case Sacksent:
		if(p->timeout <= 0)
			newstate(ppp, p, Sclosed);
		else {
			config(ppp, p, 0);
		}
		break;
	case Sackrcvd:
		if(p->timeout <= 0)
			newstate(ppp, p, Sclosed);
		else {
			config(ppp, p, 0);
			newstate(ppp, p, Sreqsent);
		}
		break;
	}
}

/* paptimer -- pap timer event handler
 *
 * If PAP authorization hasn't come through, resend an authreqst.  If
 * the maximum number of requests have been sent (~ 30 seconds), give
 * up.
 *
 */
static void
authtimer(PPP* ppp)
{
	if(ppp->chap->proto != APpasswd)
		return;

	if(ppp->chap->id < 21)
		putpaprequest(ppp);
	else {
		terminate(ppp, 0);
		netlog("ppp: pap timed out--not authorized\n");
	}
}


/*
 *  timer for ppp
 */
static void
ppptimer(PPP *ppp)
{
	while(!dying){
		sleep(Period);
		qlock(ppp);

		netlog("ppp: ppptimer\n");
		ptimer(ppp, ppp->lcp);
		if(ppp->lcp->state == Sopened) {
			switch(ppp->phase){
			case Pnet:
				ptimer(ppp, ppp->ccp);
				ptimer(ppp, ppp->ipcp);
				break;
			case Pauth:
				authtimer(ppp);
				break;