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

#include <u.h>
#include <libc.h>
#include <auth.h>
#include <bio.h>
#include <ip.h>
#include <libsec.h>
#include <ndb.h>
#include "ppp.h"

#define PATH 128

static	int	baud;
static	int	nocompress;
static 	int	pppframing = 1;
static	int	noipcompress;
static	int	server;
static	int	nip;		/* number of ip interfaces */
static	int	dying;		/* flag to signal to all threads its time to go */
static	int	primary;	/* this is the primary IP interface */
static	char	*chatfile;

int	debug;
char*	LOG = "ppp";
char*	keyspec = "";

enum
{
	Rmagic=	0x12345
};

/*
 * Calculate FCS - rfc 1331
 */
ushort fcstab[256] =
{
      0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
      0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
      0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
      0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
      0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
      0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
      0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
      0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
      0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
      0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
      0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
      0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
      0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
      0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
      0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
      0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
      0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
      0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
      0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
      0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
      0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
      0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
      0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
      0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
      0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
      0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
      0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
      0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
      0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
      0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
      0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
      0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
};

static char *snames[] =
{
	"Sclosed",
	"Sclosing",
	"Sreqsent",
	"Sackrcvd",
	"Sacksent",
	"Sopened",
};

static	void		authtimer(PPP*);
static	void		chapinit(PPP*);
static	void		config(PPP*, Pstate*, int);
static	uchar*		escapeuchar(PPP*, ulong, uchar*, ushort*);
static	void		getchap(PPP*, Block*);
static	Block*		getframe(PPP*, int*);
static	void		getlqm(PPP*, Block*);
static	int		getopts(PPP*, Pstate*, Block*);
static	void		getpap(PPP*, Block*);
static	void		init(PPP*);
static	void		invalidate(Ipaddr);
static	void		ipinproc(PPP*);
static	char*		ipopen(PPP*);
static	void		mediainproc(PPP*);
static	void		newstate(PPP*, Pstate*, int);
static	int		nipifcs(char*);
static	void		papinit(PPP*);
static	void		pinit(PPP*, Pstate*);
static	void		ppptimer(PPP*);
static	void		printopts(Pstate*, Block*, int);
static	void		ptimer(PPP*, Pstate*);
static	int		putframe(PPP*, int, Block*);
static	void		putlqm(PPP*);
static	void		putndb(PPP*, char*);
static	void		putpaprequest(PPP*);
static	void		rcv(PPP*, Pstate*, Block*);
static	void		rejopts(PPP*, Pstate*, Block*, int);
static	void		sendechoreq(PPP*, Pstate*);
static	void		sendtermreq(PPP*, Pstate*);
static	void		setphase(PPP*, int);
static	void		terminate(PPP*, int);
static	int		validv4(Ipaddr);
static  void		dmppkt(char *s, uchar *a, int na);
static	void		getauth(PPP*);

void
pppopen(PPP *ppp, int mediain, int mediaout, char *net,
	Ipaddr ipaddr, Ipaddr remip,
	int mtu, int framing)
{
	ppp->ipfd = -1;
	ppp->ipcfd = -1;
	invalidate(ppp->remote);
	invalidate(ppp->local);
	invalidate(ppp->curremote);
	invalidate(ppp->curlocal);
	invalidate(ppp->dns[0]);
	invalidate(ppp->dns[1]);
	invalidate(ppp->wins[0]);
	invalidate(ppp->wins[1]);

	ppp->mediain = mediain;
	ppp->mediaout = mediaout;
	if(validv4(remip)){
		ipmove(ppp->remote, remip);
		ppp->remotefrozen = 1;
	}
	if(validv4(ipaddr)){
		ipmove(ppp->local, ipaddr);
		ppp->localfrozen = 1;
	}
	ppp->mtu = Defmtu;
	ppp->mru = mtu;
	ppp->framing = framing;
	ppp->net = net;

	init(ppp);
	switch(rfork(RFPROC|RFMEM|RFNOWAIT)){
	case -1:
		sysfatal("forking mediainproc");
	case 0:
		mediainproc(ppp);
		terminate(ppp, 1);
		_exits(0);
	}
}

static void
init(PPP* ppp)
{
	if(ppp->inbuf == nil){
		ppp->inbuf = allocb(4096);
		if(ppp->inbuf == nil)
			abort();

		ppp->outbuf = allocb(4096);
		if(ppp->outbuf == nil)
			abort();

		ppp->lcp = mallocz(sizeof(*ppp->lcp), 1);
		if(ppp->lcp == nil)
			abort();
		ppp->lcp->proto = Plcp;
		ppp->lcp->state = Sclosed;

		ppp->ccp = mallocz(sizeof(*ppp->ccp), 1);
		if(ppp->ccp == nil)
			abort();
		ppp->ccp->proto = Pccp;
		ppp->ccp->state = Sclosed;

		ppp->ipcp = mallocz(sizeof(*ppp->ipcp), 1);
		if(ppp->ipcp == nil)
			abort();
		ppp->ipcp->proto = Pipcp;
		ppp->ipcp->state = Sclosed;

		ppp->chap = mallocz(sizeof(*ppp->chap), 1);
		if(ppp->chap == nil)
			abort();
		ppp->chap->proto = APmschap;
		ppp->chap->state = Cunauth;
		auth_freechal(ppp->chap->cs);
		ppp->chap->cs = nil;

		switch(rfork(RFPROC|RFMEM|RFNOWAIT)){
		case -1:
			sysfatal("forking ppptimer");
		case 0:
			ppptimer(ppp);
			_exits(0);
		}
	}

	ppp->ctcp = compress_init(ppp->ctcp);
	pinit(ppp, ppp->lcp);
	setphase(ppp, Plink);
}

static void
setphase(PPP *ppp, int phase)
{
	int oldphase;

	oldphase = ppp->phase;

	ppp->phase = phase;
	switch(phase){
	default:
		sysfatal("ppp: unknown phase %d", phase);
	case Pdead:
		/* restart or exit? */
		pinit(ppp, ppp->lcp);
		setphase(ppp, Plink);
		break;
	case Plink:
		/* link down */
		switch(oldphase) {
		case Pauth:
			auth_freechal(ppp->chap->cs);
			ppp->chap->cs = nil;
			ppp->chap->state = Cunauth;
			break;
		case Pnet:
			auth_freechal(ppp->chap->cs);
			ppp->chap->cs = nil;
			ppp->chap->state = Cunauth;
			newstate(ppp, ppp->ccp, Sclosed);
			newstate(ppp, ppp->ipcp, Sclosed);
		}
		break;
	case Pauth:
		if(server)
			chapinit(ppp);
		else if(ppp->chap->proto == APpasswd)
			papinit(ppp);
		else
			setphase(ppp, Pnet);
		break;
	case Pnet:
		pinit(ppp, ppp->ccp);
		pinit(ppp, ppp->ipcp);
		break;
	case Pterm:
		/* what? */
		break;
	}
}

static void
pinit(PPP *ppp, Pstate *p)
{
	p->timeout = 0;

	switch(p->proto){
	case Plcp:
		ppp->magic = truerand();
		ppp->xctlmap = 0xffffffff;
		ppp->period = 0;
		p->optmask = 0xffffffff;
		if(!server)
			p->optmask &=  ~(Fauth|Fmtu);
		ppp->rctlmap = 0;
		ppp->ipcp->state = Sclosed;
		ppp->ipcp->optmask = 0xffffffff;

		p->echotimeout = 0;

		/* quality goo */
		ppp->timeout = 0;
		memset(&ppp->in, 0, sizeof(ppp->in));
		memset(&ppp->out, 0, sizeof(ppp->out));
		memset(&ppp->pin, 0, sizeof(ppp->pin));
		memset(&ppp->pout, 0, sizeof(ppp->pout));
		memset(&ppp->sin, 0, sizeof(ppp->sin));
		break;
	case Pccp:
		if(nocompress)
			p->optmask = 0;
		else
			p->optmask = Fcmppc;

		if(ppp->ctype != nil)
			(*ppp->ctype->fini)(ppp->cstate);
		ppp->ctype = nil;
		ppp->ctries = 0;
		ppp->cstate = nil;

		if(ppp->unctype)
			(*ppp->unctype->fini)(ppp->uncstate);
		ppp->unctype = nil;
		ppp->uncstate = nil;
		break;
	case Pipcp:
		p->optmask = 0xffffffff;
		ppp->ctcp = compress_init(ppp->ctcp);
		break;
	}
	p->confid = p->rcvdconfid = -1;
	config(ppp, p, 1);
	newstate(ppp, p, Sreqsent);
}

/*
 *  change protocol to a new state.
 */
static void
newstate(PPP *ppp, Pstate *p, int state)
{
	char *err;

	netlog("ppp: %ux %s->%s ctlmap %lux/%lux flags %lux mtu %ld mru %ld\n",
		p->proto, snames[p->state], snames[state], ppp->rctlmap,
		ppp->xctlmap, p->flags,
		ppp->mtu, ppp->mru);
	syslog(0, "ppp", "%ux %s->%s ctlmap %lux/%lux flags %lux mtu %ld mru %ld",
		p->proto, snames[p->state], snames[state], ppp->rctlmap,
		ppp->xctlmap, p->flags,
		ppp->mtu, ppp->mru);

	if(p->proto == Plcp) {
		if(state == Sopened)
			setphase(ppp, Pauth);
		else if(state == Sclosed)
			setphase(ppp, Pdead);
		else if(p->state == Sopened)
			setphase(ppp, Plink);
	}

	if(p->proto == Pccp && state == Sopened) {
		if(ppp->unctype)
			(*ppp->unctype->fini)(ppp->uncstate);
		ppp->unctype = nil;
		ppp->uncstate = nil;
		if(p->optmask & Fcmppc) {
			ppp->unctype = &uncmppc;
			ppp->uncstate = (*uncmppc.init)(ppp);
		}
		if(p->optmask & Fcthwack){
			ppp->unctype = &uncthwack;
			ppp->uncstate = (*uncthwack.init)(ppp);
		}
	}

	if(p->proto == Pipcp && state == Sopened) {
		if(server && ppp->chap->state != Cauthok)
			abort();

		err = ipopen(ppp);
		if(err != nil)
			sysfatal("%s", err);
	}

	p->state = state;
}

/* returns (protocol, information) */
static Block*
getframe(PPP *ppp, int *protop)
{
	uchar *p, *from, *to;
	int n, len, proto;
	ulong c;
	ushort fcs;
	Block *buf, *b;

	*protop = 0;
	if(ppp->framing == 0) {
		/* assume data is already framed */
		b = allocb(2000);
		len = b->lim - b->wptr;
		n = read(ppp->mediain, b->wptr, len);
 		dmppkt("RX", b->wptr, n);
		if(n <= 0 || n == len){
			freeb(b);

			return nil;
		}
		b->wptr += n;

		/* should probably copy to another block if small */

		if(pppframing && b->rptr[0] == PPP_addr && b->rptr[1] == PPP_ctl)
			b->rptr += 2;
		proto = *b->rptr++;
		if((proto & 0x1) == 0)
			proto = (proto<<8) | *b->rptr++;

		if(b->rptr >= b->wptr){
			freeb(b);
			return nil;
		}

		ppp->in.uchars += n;
		ppp->in.packets++;
		*protop = proto;
		netlog("getframe 0x%x\n", proto);
		return b;
	}

	buf = ppp->inbuf;
	for(;;){
		/* read till we hit a frame uchar or run out of room */
		for(p = buf->rptr; buf->wptr < buf->lim;){
			for(; p < buf->wptr; p++)
				if(*p == HDLC_frame)
					break;
			if(p != buf->wptr)
				break;

			len = buf->lim - buf->wptr;
			n = read(ppp->mediain, buf->wptr, len);
			if(n <= 0){
				syslog(0, LOG, "medium read returns %d: %r", n);
				buf->wptr = buf->rptr;
				return nil;
			}
 			dmppkt("RX", buf->wptr, n);
			buf->wptr += n;
		}

		/* copy into block, undoing escapes, and caculating fcs */
		fcs = PPP_initfcs;
		b = allocb(p - buf->rptr);
		to = b->wptr;
		for(from = buf->rptr; from != p;){
			c = *from++;
			if(c == HDLC_esc){
				if(from == p)
					break;
				c = *from++ ^ 0x20;
			} else if((c < 0x20) && (ppp->rctlmap & (1 << c)))
				continue;
			*to++ = c;
			fcs = (fcs >> 8) ^ fcstab[(fcs ^ c) & 0xff];
		}

		/* copy down what's left in buffer */
		p++;
		memmove(buf->rptr, p, buf->wptr - p);
		n = p - buf->rptr;
		buf->wptr -= n;
		b->wptr = to - 2;

		/* return to caller if checksum matches */
		if(fcs == PPP_goodfcs){
			if(b->rptr[0] == PPP_addr && b->rptr[1] == PPP_ctl)
				b->rptr += 2;
			proto = *b->rptr++;
			if((proto & 0x1) == 0)
				proto = (proto<<8) | *b->rptr++;
			if(b->rptr < b->wptr){
				ppp->in.uchars += n;
				ppp->in.packets++;
				*protop = proto;
				netlog("getframe 0x%x\n", proto);
				return b;
			}
		} else if(BLEN(b) > 0){
			if(ppp->ctcp)
				compress_error(ppp->ctcp);
			ppp->in.discards++;
			netlog("ppp: discard len %ld/%ld cksum %ux (%ux %ux %ux %ux)\n",
				BLEN(b), BLEN(buf), fcs, b->rptr[0],
				b->rptr[1], b->rptr[2], b->rptr[3]);
		}

		freeb(b);
	}
}

/* send a PPP frame */
static int
putframe(PPP *ppp, int proto, Block *b)
{
	Block *buf;
	uchar *to, *from;
	ushort fcs;
	ulong ctlmap;
	uchar c;
	Block *bp;

	ppp->out.packets++;

	if(proto == Plcp)
		ctlmap = 0xffffffff;
	else
		ctlmap = ppp->xctlmap;

	/* make sure we have head room */
	if(b->rptr - b->base < 4){
		b = padb(b, 4);
		b->rptr += 4;
	}

	netlog("ppp: putframe 0x%ux %ld\n", proto, b->wptr-b->rptr);

	/* add in the protocol and address, we'd better have left room */
	from = b->rptr;
	*--from = proto;
	if(!(ppp->lcp->flags&Fpc) || proto > 0x100 || proto == Plcp)
		*--from = proto>>8;
	if(pppframing && (!(ppp->lcp->flags&Fac) || proto == Plcp)){
		*--from = PPP_ctl;
		*--from = PPP_addr;
	}

	qlock(&ppp->outlock);
	buf = ppp->outbuf;

	if(ppp->framing == 0) {
		to = buf->rptr;
		for(bp = b; bp; bp = bp->next){
			if(bp != b)
				from = bp->rptr;
			memmove(to, from, bp->wptr-from);
			to += bp->wptr-from;
		}
	} else {
		/* escape and checksum the body */
		fcs = PPP_initfcs;
		to = buf->rptr;
	
		/* add frame marker */
		*to++ = HDLC_frame;

		for(bp = b; bp; bp = bp->next){
			if(bp != b)
				from = bp->rptr;
			for(; from < bp->wptr; from++){
				c = *from;
				if(c == HDLC_frame || c == HDLC_esc
				   || (c < 0x20 && ((1<<c) & ctlmap))){
					*to++ = HDLC_esc;
					*to++ = c ^ 0x20;
				} else 
					*to++ = c;
				fcs = (fcs >> 8) ^ fcstab[(fcs ^ c) & 0xff];
			}
		}

		/* add on and escape the checksum */
		fcs = ~fcs;
		c = fcs;
		if(c == HDLC_frame || c == HDLC_esc
		   || (c < 0x20 && ((1<<c) & ctlmap))){
			*to++ = HDLC_esc;
			*to++ = c ^ 0x20;
		} else 
			*to++ = c;
		c = fcs>>8;
		if(c == HDLC_frame || c == HDLC_esc
		   || (c < 0x20 && ((1<<c) & ctlmap))){
			*to++ = HDLC_esc;
			*to++ = c ^ 0x20;
		} else 
			*to++ = c;
	
		/* add frame marker */
		*to++ = HDLC_frame;
	}

	/* send */
	buf->wptr = to;
 	dmppkt("TX", buf->rptr, BLEN(buf));
	if(write(ppp->mediaout, buf->rptr, BLEN(buf)) < 0){
		qunlock(&ppp->outlock);
		return -1;
	}
	ppp->out.uchars += BLEN(buf);

	qunlock(&ppp->outlock);
	return 0;
}

Block*
alloclcp(int code, int id, int len, Lcpmsg **mp)
{
	Block *b;
	Lcpmsg *m;

	/*
	 *  leave room for header
	 */
	b = allocb(len);

	m = (Lcpmsg*)b->wptr;
	m->code = code;
	m->id = id;
	b->wptr += 4;

	*mp = m;
	return b;
}


static void
putlo(Block *b, int type, ulong val)
{
	*b->wptr++ = type;
	*b->wptr++ = 6;
	hnputl(b->wptr, val);
	b->wptr += 4;
}

static void
putv4o(Block *b, int type, Ipaddr val)
{
	*b->wptr++ = type;
	*b->wptr++ = 6;
	v6tov4(b->wptr, val);
	b->wptr += 4;
}

static void
putso(Block *b, int type, ulong val)
{
	*b->wptr++ = type;
	*b->wptr++ = 4;
	hnputs(b->wptr, val);
	b->wptr += 2;
}

static void
puto(Block *b, int type)
{
	*b->wptr++ = type;
	*b->wptr++ = 2;
}

/*
 *  send configuration request
 */
static void
config(PPP *ppp, Pstate *p, int newid)
{
	Block *b;
	Lcpmsg *m;
	int id;

	if(newid){
		id = p->id++;
		p->confid = id;
		p->timeout = Timeout;
	} else
		id = p->confid;
	b = alloclcp(Lconfreq, id, 256, &m);
	USED(m);

	switch(p->proto){
	case Plcp:
		if(p->optmask & Fctlmap)
			putlo(b, Octlmap, 0);	/* we don't want anything escaped */
		if(p->optmask & Fmagic)
			putlo(b, Omagic, ppp->magic);
		if(p->optmask & Fmtu)
			putso(b, Omtu, ppp->mru);
		if(p->optmask & Fauth) {
			*b->wptr++ = Oauth;
			*b->wptr++ = 5;
			hnputs(b->wptr, Pchap);
			b->wptr += 2;
			*b->wptr++ = ppp->chap->proto;
		}
		if(p->optmask & Fpc)
			puto(b, Opc);
		if(p->optmask & Fac)
			puto(b, Oac);
		break;
	case Pccp:
		if(p->optmask & Fcthwack)
			puto(b, Octhwack);
		else if(p->optmask & Fcmppc) {
			*b->wptr++ = Ocmppc;
			*b->wptr++ = 6;
			*b->wptr++ = 0;
			*b->wptr++ = 0;
			*b->wptr++ = 0;
			*b->wptr++ = 0x41;
		}
		break;
	case Pipcp:
		if(p->optmask & Fipaddr)
{syslog(0, "ppp", "requesting %I", ppp->local);
			putv4o(b, Oipaddr, ppp->local);
}
		if(primary && (p->optmask & Fipdns))
			putv4o(b, Oipdns, ppp->dns[0]);
		if(primary && (p->optmask & Fipdns2))
			putv4o(b, Oipdns2, ppp->dns[1]);
		if(primary && (p->optmask & Fipwins))
			putv4o(b, Oipwins, ppp->wins[0]);
		if(primary && (p->optmask & Fipwins2))
			putv4o(b, Oipwins2, ppp->wins[1]);
		/*
		 * don't ask for header compression while data compression is still pending.
		 * perhaps we should restart ipcp negotiation if compression negotiation fails.
		 */
		if(!noipcompress && !ppp->ccp->optmask && (p->optmask & Fipcompress)) {
			*b->wptr++ = Oipcompress;
			*b->wptr++ = 6;
			hnputs(b->wptr, Pvjctcp);
			b->wptr += 2;
			*b->wptr++ = MAX_STATES-1;
			*b->wptr++ = 1;
		}
		break;
	}
	hnputs(m->len, BLEN(b));
	printopts(p, b, 1);
	putframe(ppp, p->proto, b);
	freeb(b);
}

static void
getipinfo(PPP *ppp)
{
	char *av[3];
	int ndns, nwins;
	char ip[64];
	Ndbtuple *t, *nt;

	if(!validv4(ppp->local))
		return;