pptp.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

	memset(pkt, 0, sizeof pkt);

	hnputs(pkt+0, 156);
	hnputs(pkt+2, 1);
	hnputl(pkt+4, Magic);
	hnputs(pkt+8, Tstart);
	hnputs(pkt+12, PptpProto);
	hnputl(pkt+16, 1);
	hnputl(pkt+20, 1);
	hnputs(pkt+24, 1);
	name = sysname();
	if(name == nil)
		name = "gnot";
	strcpy((char*)pkt+28, name);
	strcpy((char*)pkt+92, "plan 9");

	if(debug)
		dumpctlpkt(pkt);

	rdexpect = Rstart;
	ewrite(ctlfd, pkt, 156);

	rpkt = recvp(rdchan);
	if(rpkt == nil)
		myfatal("recvp: %r");
	if(nhgets(rpkt) != 156)
		myfatal("Rstart wrong length %d != 156", nhgets(rpkt));
	if(rpkt[14] != 1)
		myfatal("Rstart error %d", rpkt[15]);
	free(rpkt);
}

void
tcallout(void)
{
	uchar pkt[200], *rpkt;

	pid = getpid();

	memset(pkt, 0, sizeof pkt);
	hnputs(pkt+0, 168);
	hnputs(pkt+2, 1);
	hnputl(pkt+4, Magic);
	hnputs(pkt+8, Tcallout);

	hnputl(pkt+16, 56000);
	hnputl(pkt+20, 768000);
	hnputl(pkt+24, 3);
	hnputl(pkt+28, 3);
	if(localwin == 0)
		localwin = Window;
	hnputs(pkt+32, localwin);

	if(debug)
		dumpctlpkt(pkt);

	rdexpect = Rcallout;
	ewrite(ctlfd, pkt, 168);

	rpkt = recvp(rdchan);
	if(rpkt == nil)
		myfatal("recvp: %r");
	if(nhgets(rpkt) != 32)
		myfatal("Rcallreq wrong length %d != 32", nhgets(rpkt));
	if(rpkt[16] != 1)
		myfatal("Rcallreq error %d", rpkt[17]);
	remid = nhgets(pkt+12);
	remwin = nhgets(pkt+24);
	free(rpkt);
}

/*
void
tcallreq(void)
{
	uchar pkt[200], *rpkt;

	pid = getpid();

	memset(pkt, 0, sizeof pkt);
	hnputs(pkt+0, 220);
	hnputs(pkt+2, 1);
	hnputl(pkt+4, Magic);
	hnputs(pkt+8, Tcallreq);

	if(debug)
		dumpctlpkt(pkt);

	rdexpect = Rcallreq;
	ewrite(ctlfd, pkt, 220);

	rpkt = recvp(rdchan);
	if(rpkt == nil)
		myfatal("recvp: %r");
	if(nhgets(rpkt) != 24)
		myfatal("Rcallreq wrong length %d != 24", nhgets(rpkt));
	if(rpkt[16] != 1)
		myfatal("Rcallreq error %d", rpkt[17]);
	remid = nhgets(pkt+12);
	remwin = nhgets(pkt+18);
	free(rpkt);
}

void
acallcon(void)
{
	uchar pkt[200];

	memset(pkt, 0, sizeof pkt);
	hnputs(pkt+0, 28);
	hnputs(pkt+2, 1);
	hnputl(pkt+4, Magic);
	hnputs(pkt+8, Acallcon);
	hnputs(pkt+12, remid);
	if(localwin == 0)
		localwin = Window;
	hnputs(pkt+20, localwin);
	hnputl(pkt+24, 1);

	if(debug)
		dumpctlpkt(pkt);

	ewrite(ctlfd, pkt, 28);
}
*/

int
pptp(char *addr)
{
	int p[2];
	char greaddr[128];

	addr = netmkaddr(addr, "net", "pptp");
	ctlfd = dial(addr, nil, tcpdir, nil);
	if(ctlfd < 0)
		myfatal("dial %s: %r", addr);
 	getaddrs();

	rdchan = chancreate(sizeof(void*), 0);
	proccreate(pptpctlproc, nil, Stack);

	tstart();
	tcallout();

	if(pipe(p) < 0)
		myfatal("pipe: %r");

	pppfd = p[0];
	topppfd = p[1];

	strcpy(greaddr, tcpdir);
	*strrchr(greaddr, '/') = '\0';
	sprint(strrchr(greaddr, '/')+1, "gre!%I!%d", remoteip, GrePPP);

	print("local %I remote %I gre %s remid %d remwin %d\n",
		localip, remoteip, greaddr, remid, remwin);

	grefd = dial(greaddr, nil, nil, nil);
	if(grefd < 0)
		myfatal("dial gre: %r");

	tickchan = chancreate(sizeof(int), 0);
	proccreate(gretimeoutproc, nil, Stack);

	pidchan = chancreate(sizeof(int), 0);
	proccreate(grereadproc, nil, Stack);
	recvul(pidchan);
	proccreate(pppreadproc, nil, Stack);
	recvul(pidchan);

	close(topppfd);
	return pppfd;
}
	
void
pushppp(int fd)
{
	char *argv[16];
	int argc;

	argc = 0;
	argv[argc++] = "/bin/ip/ppp";
	argv[argc++] = "-C";
	argv[argc++] = "-m1450";
	if(debug)
		argv[argc++] = "-d";
	if(primary)
		argv[argc++] = "-P";
	if(pppnetmntpt){
		argv[argc++] = "-x";
		argv[argc++] = pppnetmntpt;
	}
	if(keyspec){
		argv[argc++] = "-k";
		argv[argc++] = keyspec;
	}
	argv[argc] = nil;

	switch(fork()){
	case -1:
		myfatal("fork: %r");
	default:
		return;
	case 0:
		dup(fd, 0);
		dup(fd, 1);
		exec(argv[0], argv);
		myfatal("exec: %r");
	}
}

int
aread(int timeout, int fd, void *buf, int nbuf)
{
	int n;

	alarmed = 0;
	alarm(timeout);
	n = read(fd, buf, nbuf);
	alarm(0);
	if(alarmed)
		return -1;
	if(n < 0)
		myfatal("read: %r");
	if(n == 0)
		myfatal("short read");
	return n;
}

void
ewrite(int fd, void *buf, int nbuf)
{
	char e[ERRMAX], path[64];

	if(write(fd, buf, nbuf) != nbuf){
		rerrstr(e, sizeof e);
		strcpy(path, "unknown");
		fd2path(fd, path, sizeof path);
		myfatal("write %d to %s: %s", nbuf, path, e);
	}
}

void*
emalloc(long n)
{
	void *v;

	v = malloc(n);
	if(v == nil)
		myfatal("out of memory");
	return v;
}

int
thread(void(*f)(void*), void *a)
{
	int pid;
	pid=rfork(RFNOWAIT|RFMEM|RFPROC);
	if(pid < 0)
		myfatal("rfork: %r");
	if(pid != 0)
		return pid;
	(*f)(a);
	_exits(nil);
	return 0; // never reaches here
}

void
dumpctlpkt(uchar *pkt)
{
	fprint(2, "pkt len %d mtype %d cookie 0x%.8ux type %d\n",
		nhgets(pkt), nhgets(pkt+2),
		nhgetl(pkt+4), nhgets(pkt+8));

	switch(nhgets(pkt+8)){
	default:
		fprint(2, "\tunknown type\n");
		break;
	case Tstart:
		fprint(2, "\tTstart proto %d framing %d bearer %d maxchan %d firmware %d\n",
			nhgets(pkt+12), nhgetl(pkt+16),
			nhgetl(pkt+20), nhgets(pkt+24),
			nhgets(pkt+26));
		fprint(2, "\thost %.64s\n", (char*)pkt+28);
		fprint(2, "\tvendor %.64s\n", (char*)pkt+92);
		break;
	case Rstart:
		fprint(2, "\tRstart proto %d res %d err %d framing %d bearer %d maxchan %d firmware %d\n",
			nhgets(pkt+12), pkt[14], pkt[15],
			nhgetl(pkt+16),
			nhgetl(pkt+20), nhgets(pkt+24),
			nhgets(pkt+26));
		fprint(2, "\thost %.64s\n", (char*)pkt+28);
		fprint(2, "\tvendor %.64s\n", (char*)pkt+92);
		break;

	case Tstop:
		fprint(2, "\tTstop reason %d\n", pkt[12]);
		break;

	case Rstop:
		fprint(2, "\tRstop res %d err %d\n", pkt[12], pkt[13]);
		break;

	case Techo:
		fprint(2, "\tTecho id %.8ux\n", nhgetl(pkt+12));
		break;

	case Recho:
		fprint(2, "\tRecho id %.8ux res %d err %d\n", nhgetl(pkt+12), pkt[16], pkt[17]);
		break;

	case Tcallout:
		fprint(2, "\tTcallout id %d serno %d bps %d-%d\n",
			nhgets(pkt+12), nhgets(pkt+14),
			nhgetl(pkt+16), nhgetl(pkt+20));
		fprint(2, "\tbearer 0x%x framing 0x%x recvwin %d delay %d\n",
			nhgetl(pkt+24), nhgetl(pkt+28),
			nhgets(pkt+32), nhgets(pkt+34));
		fprint(2, "\tphone len %d num %.64s\n", 
			nhgets(pkt+36), (char*)pkt+40);
		fprint(2, "\tsubaddr %.64s\n", (char*)pkt+104);
		break;

	case Rcallout:
		fprint(2, "\tRcallout id %d peerid %d res %d err %d cause %d\n",
			nhgets(pkt+12), nhgets(pkt+14),
			pkt[16], pkt[17], nhgets(pkt+18));
		fprint(2, "\tconnect %d recvwin %d delay %d chan 0x%.8ux\n",
			nhgetl(pkt+20), nhgets(pkt+24),
			nhgets(pkt+26), nhgetl(pkt+28));
		break;

	case Tcallreq:
		fprint(2, "\tTcallreq id %d serno %d bearer 0x%x id 0x%x\n",
			nhgets(pkt+12), nhgets(pkt+14),
			nhgetl(pkt+16), nhgetl(pkt+20));
		fprint(2, "\tdialed len %d num %.64s\n",
			nhgets(pkt+24), (char*)pkt+28);
		fprint(2, "\tdialing len %d num %.64s\n",
			nhgets(pkt+26), (char*)pkt+92);
		fprint(2, "\tsubaddr %.64s\n", (char*)pkt+156);
		break;

	case Rcallreq:
		fprint(2, "\tRcallout id %d peerid %d res %d err %d recvwin %d delay %d\n",
			nhgets(pkt+12), nhgets(pkt+14),
			pkt[16], pkt[17], nhgets(pkt+18),
			nhgets(pkt+20));
		break;

	case Acallcon:
		fprint(2, "\tAcallcon peerid %d connect %d recvwin %d delay %d framing 0x%x\n",
			nhgets(pkt+12), nhgetl(pkt+16),
			nhgets(pkt+20), nhgets(pkt+22),
			nhgetl(pkt+24));
		break;

	case Tcallclear:
		fprint(2, "\tTcallclear callid %d\n",
			nhgets(pkt+12));
		break;

	case Acalldis:
		fprint(2, "\tAcalldis callid %d res %d err %d cause %d\n",
			nhgets(pkt+12), pkt[14], pkt[15],
			nhgets(pkt+16));
		fprint(2, "\tstats %.128s\n", (char*)pkt+20);
		break;

	case Awaninfo:
		fprint(2, "\tAwaninfo peerid %d\n", nhgets(pkt+12));
		fprint(2, "\tcrc errors %d\n", nhgetl(pkt+16));
		fprint(2, "\tframe errors %d\n", nhgetl(pkt+20));
		fprint(2, "\thardware overruns %d\n", nhgetl(pkt+24));
		fprint(2, "\tbuffer overruns %d\n", nhgetl(pkt+28));
		fprint(2, "\ttime-out errors %d\n", nhgetl(pkt+32));
		fprint(2, "\talignment errors %d\n", nhgetl(pkt+36));
		break;

	case Alinkinfo:
		fprint(2, "\tAlinkinfo peerid %d sendaccm 0x%ux recvaccm 0x%ux\n",
			nhgets(pkt+12), nhgetl(pkt+16),
			nhgetl(pkt+20));
		break;
	}
}

void
getaddrs(void)
{
	char buf[128];
	int fd, n;

	sprint(buf, "%s/local", tcpdir);
	if((fd = open(buf, OREAD)) < 0)
		myfatal("could not open %s: %r", buf);
	if((n = read(fd, buf, sizeof(buf))) < 0)
		myfatal("could not read %s: %r", buf);
	buf[n] = 0;
	parseip(localip, buf);
	close(fd);

	sprint(buf, "%s/remote", tcpdir);
	if((fd = open(buf, OREAD)) < 0)
		myfatal("could not open %s: %r", buf);
	if((n = read(fd, buf, sizeof(buf))) < 0)
		myfatal("could not read %s: %r", buf);
	buf[n] = 0;
	parseip(remoteip, buf);
	close(fd);
}

void
myfatal(char *fmt, ...)
{
	char sbuf[512];
	va_list arg;
	uchar buf[16];

	memset(buf, 0, sizeof(buf));
	hnputs(buf+0, sizeof(buf));	/* length */
	hnputs(buf+2, 1);		/* message type */
	hnputl(buf+4, Magic);		/* magic */
	hnputs(buf+8, Tstop);		/* op */
	buf[12] = 3;			/* local shutdown */
	write(ctlfd, buf, sizeof(buf));

	va_start(arg, fmt);
	vseprint(sbuf, sbuf+sizeof(sbuf), fmt, arg);
	va_end(arg);

	fprint(2, "fatal: %s\n", sbuf);
	threadexitsall(nil);
}