pptpd.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 <bio.h>
#include <ip.h>

#define	LOG	"pptpd"

typedef struct Call	Call;
typedef struct Event Event;

#define	SDB	if(debug) fprint(2, 
#define EDB	);

enum {
	Magic	= 0x1a2b3c4d,
	Nhash	= 17,
	Nchan	= 10,		/* maximum number of channels */
	Window	= 8,		/* default window size */
	Timeout	= 60,		/* timeout in seconds for control channel */
	Pktsize = 2000,		/* maximum packet size */
	Tick	= 500,		/* tick length in milliseconds */
	Sendtimeout = 4,	/* in ticks */
};

enum {
	Syncframe	= 0x1,
	Asyncframe	= 0x2,
	Analog		= 0x1,
	Digital		= 0x2,
	Version		= 0x100,
};

enum {
	Tstart		= 1,
	Rstart		= 2,
	Tstop		= 3,
	Rstop		= 4,
	Techo		= 5,
	Recho		= 6,
	Tcallout	= 7,
	Rcallout	= 8,
	Tcallreq	= 9,
	Rcallreq	= 10,
	Acallcon	= 11,
	Tcallclear	= 12,
	Acalldis	= 13,
	Awaninfo	= 14,
	Alinkinfo	= 15,
};


struct Event {
	QLock;
	QLock waitlk;
	int	wait;
	int ready;
};

struct Call {
	int	ref;
	QLock	lk;
	int	id;
	int	serial;
	int	pppfd;

	int	closed;

	int	pac;	/* server is acting as a PAC */

	int	recvwindow;	/* recv windows */
	int	sendwindow;	/* send windows */
	int	delay;

	int	sendaccm;
	int	recvaccm;

	uint	seq;		/* current seq number - for send */
	uint	ack;		/* current acked mesg - for send */
	uint	rseq;		/* highest recv seq number for in order packet  */
	uint	rack;		/* highest ack sent */

	Event	eack;		/* recved ack - for send */
	ulong	tick;

	uchar	remoteip[IPaddrlen];	/* remote ip address */
	int	dhcpfd[2];	/* pipe to dhcpclient */

	/* error stats */
	struct {
		int	crc;
		int	frame;
		int	hardware;
		int	overrun;
		int	timeout;
		int	align;
	} err;

	struct {
		int	send;
		int	sendack;
		int	recv;
		int	recvack;
		int	dropped;
		int	missing;
		int	sendwait;
		int	sendtimeout;
	} stat;

	Call	*next;
};

struct {
	QLock	lk;
	int	start;
	int	grefd;
	int	grecfd;
	uchar	local[IPaddrlen];
	uchar	remote[IPaddrlen];
	char	*tcpdir;
	uchar	ipaddr[IPaddrlen];		/* starting ip addresss to allocate */

	int	recvwindow;

	char	*pppdir;
	char	*pppexec;

	double	rcvtime;	/* time at which last request was received */
	int	echoid;		/* id of last echo request */

	Call	*hash[Nhash];
} srv;

/* GRE flag bits */
enum {
	GRE_chksum	= (1<<15),
	GRE_routing	= (1<<14),
	GRE_key		= (1<<13),
	GRE_seq		= (1<<12),
	GRE_srcrt	= (1<<11),
	GRE_recur	= (7<<8),
	GRE_ack		= (1<<7),
	GRE_ver		= 0x7,
};

/* GRE protocols */
enum {
	GRE_ppp		= 0x880b,
};

int	debug;
double	drop;

void	myfatal(char *fmt, ...);

#define	PSHORT(p, v)		((p)[0]=((v)>>8), (p)[1]=(v))
#define	PLONG(p, v)		(PSHORT(p, (v)>>16), PSHORT(p+2, (v)))
#define	PSTRING(d,s,n)		strncpy((char*)(d), s, n)
#define	GSHORT(p)		(((p)[0]<<8) | ((p)[1]<<0))
#define	GLONG(p)		((GSHORT((p))<<16) | ((GSHORT((p)+2))<<0))
#define	GSTRING(d,s,n)		strncpy(d, (char*)(s), n), d[(n)-1] = 0

void	serve(void);

int	sstart(uchar*, int);
int	sstop(uchar*, int);
int	secho(uchar*, int);
int	scallout(uchar*, int);
int	scallreq(uchar*, int);
int	scallcon(uchar*, int);
int	scallclear(uchar*, int);
int	scalldis(uchar*, int);
int	swaninfo(uchar*, int);
int	slinkinfo(uchar*, int);

Call	*callalloc(int id);
void	callclose(Call*);
void	callfree(Call*);
Call	*calllookup(int id);

void	gretimeout(void*);
void	pppread(void*);

void	srvinit(void);
void	greinit(void);
void	greread(void*);
void	greack(Call *c);

void	timeoutthread(void*);

ulong	parseip(uchar *ato, char *from);
int	argatoi(char *p);
void	usage(void);
int	ipaddralloc(Call *c);

void esignal(Event *e);
void ewait(Event *e);
ulong	thread(void(*f)(void*), void *a);
double realtime(void);
void *emallocz(int size);
int proc(char **argv, int fd0, int fd1, int fd2);

void
main(int argc, char *argv[])
{
	ARGBEGIN{
	case 'd': debug++; break;
	case 'p': srv.pppdir = ARGF(); break;
	case 'P': srv.pppexec = ARGF(); break;
	case 'w': srv.recvwindow = argatoi(ARGF()); break;
	case 'D': drop = atof(ARGF()); break;
	default:
		usage();
	}ARGEND

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

	rfork(RFNOTEG|RFREND);

	if(argc != 1)
		usage();

	srv.tcpdir = argv[0];

	srvinit();

	syslog(0, LOG, ": src=%I: pptp started: %d", srv.remote, getpid());

	SDB  "\n\n\n%I: pptp started\n", srv.remote EDB

	greinit();

	thread(timeoutthread, 0);

	serve();

	syslog(0, LOG, ": src=%I: server exits", srv.remote);

	exits(0);
}

void
usage(void)
{
	fprint(2, "usage: pptpd [-dD] [-p ppp-net] [-w window] tcpdir\n");
	exits("usage");
}

void
serve(void)
{
	uchar buf[2000], *p;
	int n, n2, len;
	int magic;
	int op, type;

	n = 0;
	for(;;) {
		n2 = read(0, buf+n, sizeof(buf)-n);
		if(n2 < 0)
			myfatal("bad read on ctl channel: %r");
		if(n2 == 0)
			break;
		n += n2;
		p = buf;
		for(;;) {
			if(n < 12)
				break;

			qlock(&srv.lk);
			srv.rcvtime = realtime();
			qunlock(&srv.lk);

			len = GSHORT(p);
			type = GSHORT(p+2);
			magic = GLONG(p+4);
			op = GSHORT(p+8);
			if(magic != Magic)
				myfatal("bad magic number: got %x", magic);
			if(type != 1)
				myfatal("bad message type: %d", type);
			switch(op) {
			default:
				myfatal("unknown control op: %d", op);
			case Tstart:		/* start-control-connection-request */
				n2 = sstart(p, n);
				break;
			case Tstop:
				n2 = sstop(p, n);
				if(n2 > 0)
					return;
				break;
			case Techo:
				n2 = secho(p, n);
				break;
			case Tcallout:
				n2 = scallout(p, n);
				break;
			case Tcallreq:
				n2 = scallreq(p, n);
				break;
			case Acallcon:
				n2 = scallcon(p, n);
				break;
			case Tcallclear:
				n2 = scallclear(p, n);
				break;
			case Acalldis:
				n2 = scalldis(p, n);
				break;
			case Awaninfo:
				n2 = swaninfo(p, n);
				break;
			case Alinkinfo:
				n2 = slinkinfo(p, n);
				break;
			}	
			if(n2 == 0)
				break;
			if(n2 != len)
				myfatal("op=%d: bad length: got %d expected %d", op, len, n2);
			n -= n2;
			p += n2;
			
		}

		/* move down partial message */
		if(p != buf && n != 0)
			memmove(buf, p, n);
	}

}

int
sstart(uchar *p, int n)
{
	int ver, frame, bearer, maxchan, firm;
	char host[64], vendor[64], *sysname;
	uchar buf[156];

	if(n < 156)
		return 0;
	ver = GSHORT(p+12);
	frame = GLONG(p+16);
	bearer = GLONG(p+20);
	maxchan = GSHORT(p+24);
	firm = GSHORT(p+26);
	GSTRING(host, p+28, 64);
	GSTRING(vendor, p+92, 64);

	SDB "%I: start ver = %x f = %d b = %d maxchan = %d firm = %d host = %s vendor = %s\n",
		srv.remote, ver, frame, bearer, maxchan, firm, host, vendor EDB

	if(ver != Version)
		myfatal("bad version: got %x expected %x", ver, Version);

	if(srv.start)
		myfatal("multiple start messages");

	srv.start = 1;

	sysname = getenv("sysname");
	if(sysname == 0)
		strcpy(host, "gnot");
	else
		strncpy(host, sysname, 64);
	free(sysname);

	memset(buf, 0, sizeof(buf));

	PSHORT(buf+0, sizeof(buf));	/* length */
	PSHORT(buf+2, 1);		/* message type */
	PLONG(buf+4, Magic);		/* magic */
	PSHORT(buf+8, Rstart);		/* op */
	PSHORT(buf+12, Version);	/* version */
	buf[14] = 1;			/* result = ok */
	PLONG(buf+16, Syncframe|Asyncframe);	/* frameing */
	PLONG(buf+20, Digital|Analog);	/* berear capabilities */
	PSHORT(buf+24, Nchan);		/* max channels */
	PSHORT(buf+26, 1);		/* driver version */
	PSTRING(buf+28, host, 64);	/* host name */
	PSTRING(buf+92, "plan 9", 64);	/* vendor */

	if(write(1, buf, sizeof(buf)) < sizeof(buf))
		myfatal("write failed: %r");

	return 156;
}

int
sstop(uchar *p, int n)
{
	int reason;
	uchar buf[16];

	if(n < 16)
		return 0;
	reason = p[12];
	
	SDB "%I: stop %d\n", srv.remote, reason EDB

	memset(buf, 0, sizeof(buf));
	PSHORT(buf+0, sizeof(buf));	/* length */
	PSHORT(buf+2, 1);		/* message type */
	PLONG(buf+4, Magic);		/* magic */
	PSHORT(buf+8, Rstop);		/* op */
	buf[12] = 1;			/* ok */

	if(write(1, buf, sizeof(buf)) < sizeof(buf))
		myfatal("write failed: %r");

	return 16;
}

int
secho(uchar *p, int n)
{
	int id;
	uchar buf[20];

	if(n < 16)
		return 0;
	id = GLONG(p+12);
	
	SDB "%I: echo %d\n", srv.remote, id EDB

	memset(buf, 0, sizeof(buf));
	PSHORT(buf+0, sizeof(buf));	/* length */
	PSHORT(buf+2, 1);		/* message type */
	PLONG(buf+4, Magic);		/* magic */
	PSHORT(buf+8, Recho);		/* op */
	PLONG(buf+12, id);		/* id */
	p[16] = 1;			/* ok */

	if(write(1, buf, sizeof(buf)) < sizeof(buf))
		myfatal("write failed: %r");

	return 16;
}

int
scallout(uchar *p, int n)
{
	int id, serial;
	int minbps, maxbps, bearer, frame;
	int window, delay;
	int nphone;
	char phone[64], sub[64], buf[32];
	Call *c;

	if(n < 168)
		return 0;

	if(!srv.start)
		myfatal("%I: did not recieve start message", srv.remote);
	
	id = GSHORT(p+12);
	serial = GSHORT(p+14);
	minbps = GLONG(p+16);
	maxbps = GLONG(p+20);
	bearer = GLONG(p+24);
	frame = GLONG(p+28);
	window = GSHORT(p+32);
	delay = GSHORT(p+34);
	nphone = GSHORT(p+36);
	GSTRING(phone, p+40, 64);
	GSTRING(sub, p+104, 64);

	SDB "%I: callout id = %d serial = %d bps=[%d,%d] b=%x f=%x win = %d delay = %d np=%d phone=%s sub=%s\n",
		srv.remote, id, serial, minbps, maxbps, bearer, frame, window, delay, nphone, phone, sub EDB

	c = callalloc(id);
	c->sendwindow = window;
	c->delay = delay;
	c->pac = 1;
	c->recvwindow = srv.recvwindow;

	memset(buf, 0, sizeof(buf));
	PSHORT(buf+0, sizeof(buf));	/* length */
	PSHORT(buf+2, 1);		/* message type */
	PLONG(buf+4, Magic);		/* magic */
	PSHORT(buf+8, Rcallout);	/* op */
	PSHORT(buf+12, id);		/* call id */
	PSHORT(buf+14, id);		/* peer id */
	buf[16] = 1;			/* ok */
	PLONG(buf+20, 10000000);	/* speed */
	PSHORT(buf+24, c->recvwindow);	/* window size */
	PSHORT(buf+26, 0);		/* delay */
	PLONG(buf+28, 0);		/* channel id */
	
	if(write(1, buf, sizeof(buf)) < sizeof(buf))
		myfatal("write failed: %r");

	return 168;
}

int
scallreq(uchar *p, int n)
{
	USED(p);
	USED(n);

	myfatal("callreq: not done yet");
	return 0;
}

int
scallcon(uchar *p, int n)
{
	USED(p);
	USED(n);

	myfatal("callcon: not done yet");
	return 0;
}

int
scallclear(uchar *p, int n)
{
	Call *c;
	int id;
	uchar buf[148];

	if(n < 16)
		return 0;
	id = GSHORT(p+12);
	
	SDB "%I: callclear id=%d\n", srv.remote, id EDB
	
	if(c = calllookup(id)) {
		callclose(c);
		callfree(c);
	}

	memset(buf, 0, sizeof(buf));
	PSHORT(buf+0, sizeof(buf));	/* length */
	PSHORT(buf+2, 1);		/* message type */
	PLONG(buf+4, Magic);		/* magic */
	PSHORT(buf+8, Acalldis);	/* op */
	PSHORT(buf+12, id);		/* id */
	buf[14] = 3;			/* reply to callclear */

	if(write(1, buf, sizeof(buf)) < sizeof(buf))
		myfatal("write failed: %r");

	return 16;
}

int
scalldis(uchar *p, int n)
{
	Call *c;
	int id, res;

	if(n < 148)
		return 0;
	id = GSHORT(p+12);
	res = p[14];

	SDB "%I: calldis id=%d res=%d\n", srv.remote, id, res EDB

	if(c = calllookup(id)) {
		callclose(c);
		callfree(c);
	}

	return 148;
}

int
swaninfo(uchar *p, int n)
{
	Call *c;
	int id;

	if(n < 40)
		return 0;
	
	id = GSHORT(p+12);
	SDB "%I: waninfo id = %d\n", srv.remote, id EDB
	
	c = calllookup(id);
	if(c != 0) {
		c->err.crc = GLONG(p+16);
		c->err.frame = GLONG(p+20);
		c->err.hardware = GLONG(p+24);
		c->err.overrun = GLONG(p+28);
		c->err.timeout = GLONG(p+32);
		c->err.align = GLONG(p+36);

		callfree(c);
	}

	
	return 40;
}

int
slinkinfo(uchar *p, int n)
{
	Call *c;
	int id;
	int sendaccm, recvaccm;

	if(n < 24)
		return 0;
	id = GSHORT(p+12);
	sendaccm = GLONG(p+16);
	recvaccm = GLONG(p+20);

	SDB "%I: linkinfo id=%d saccm=%ux raccm=%ux\n", srv.remote, id, sendaccm, recvaccm EDB

	if(c = calllookup(id)) {
		c->sendaccm = sendaccm;
		c->recvaccm = recvaccm;

		callfree(c);
	}
	
	return 24;
}

Call*
callalloc(int id)
{
	uint h;
	Call *c;
	char buf[300], *argv[30], local[20], remote[20], **p;
	int fd, pfd[2], n;

	h = id%Nhash;

	qlock(&srv.lk);
	for(c=srv.hash[h]; c; c=c->next)
		if(c->id == id)
			myfatal("callalloc: duplicate id: %d", id);
	c = emallocz(sizeof(Call));
	c->ref = 1;
	c->id = id;
	c->sendaccm = ~0;
	c->recvaccm = ~0;

	if(!ipaddralloc(c))
		myfatal("callalloc: could not alloc remote ip address");

	if(pipe(pfd) < 0)
		myfatal("callalloc: pipe failed: %r");

	sprint(buf, "%s/ipifc/clone", srv.pppdir);
	fd = open(buf, OWRITE);
	if(fd < 0)
		myfatal("callalloc: could not open %s: %r", buf);

	n = sprint(buf, "iprouting");
	if(write(fd, buf, n) < n)
		myfatal("callalloc: write to ifc failed: %r");
	close(fd);

	p = argv;
	*p++ = srv.pppexec;
	*p++ = "-SC";
	*p++ = "-x";
	*p++ = srv.pppdir;
	if(debug)
		*p++ = "-d";
	sprint(local, "%I", srv.ipaddr);
	*p++ = local;
	sprint(remote, "%I", c->remoteip);
	*p++ = remote;
	*p = 0;