telnetd.c

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· C语言 代码 · 共 1,646 行 · 第 1/3 页

		    SYNCHing = 1;
		}

		/*
		 * Something to read from the network...
		 */
		if (FD_ISSET(net, &ibits)) {
#if	!defined(SO_OOBINLINE)
			/*
			 * In 4.2 (and 4.3 beta) systems, the
			 * OOB indication and data handling in the kernel
			 * is such that if two separate TCP Urgent requests
			 * come in, one byte of TCP data will be overlaid.
			 * This is fatal for Telnet, but we try to live
			 * with it.
			 *
			 * In addition, in 4.2 (and...), a special protocol
			 * is needed to pick up the TCP Urgent data in
			 * the correct sequence.
			 *
			 * What we do is:  if we think we are in urgent
			 * mode, we look to see if we are "at the mark".
			 * If we are, we do an OOB receive.  If we run
			 * this twice, we will do the OOB receive twice,
			 * but the second will fail, since the second
			 * time we were "at the mark", but there wasn't
			 * any data there (the kernel doesn't reset
			 * "at the mark" until we do a normal read).
			 * Once we've read the OOB data, we go ahead
			 * and do normal reads.
			 *
			 * There is also another problem, which is that
			 * since the OOB byte we read doesn't put us
			 * out of OOB state, and since that byte is most
			 * likely the TELNET DM (data mark), we would
			 * stay in the TELNET SYNCH (SYNCHing) state.
			 * So, clocks to the rescue.  If we've "just"
			 * received a DM, then we test for the
			 * presence of OOB data when the receive OOB
			 * fails (and AFTER we did the normal mode read
			 * to clear "at the mark").
			 */
		    if (SYNCHing) {
			int atmark;

			ioctl(net, SIOCATMARK, (char *)&atmark);
			if (atmark) {
			    ncc = recv(net, netibuf, sizeof (netibuf), MSG_OOB);
			    if ((ncc == -1) && (errno == EINVAL)) {
				ncc = read(net, netibuf, sizeof (netibuf));
				if (sequenceIs(didnetreceive, gotDM)) {
				    SYNCHing = stilloob(net);
				}
			    }
			} else {
			    ncc = read(net, netibuf, sizeof (netibuf));
			}
		    } else {
			ncc = read(net, netibuf, sizeof (netibuf));
		    }
		    settimer(didnetreceive);
#else	/* !defined(SO_OOBINLINE)) */
		    ncc = read(net, netibuf, sizeof (netibuf));
#endif	/* !defined(SO_OOBINLINE)) */
		    if (ncc < 0 && errno == EWOULDBLOCK)
			ncc = 0;
		    else {
			if (ncc <= 0) {
			    break;
			}
			netip = netibuf;
		    }
		}

		/*
		 * Something to read from the pty...
		 */
		if (FD_ISSET(p, &ibits)) {
			pcc = read(p, ptyibuf, BUFSIZ);
			if (pcc < 0 && errno == EWOULDBLOCK)
				pcc = 0;
			else {
				if (pcc <= 0)
					break;
				ptyip = ptyibuf;
			}
		}

		while (pcc > 0) {
			if ((&netobuf[BUFSIZ] - nfrontp) < 2)
				break;
			c = *ptyip++ & 0377, pcc--;
			if (c == IAC)
				*nfrontp++ = c;
			*nfrontp++ = c;
			if (c == '\r') {
				if (pcc > 0 && ((*ptyip & 0377) == '\n')) {
					*nfrontp++ = *ptyip++ & 0377;
					pcc--;
				} else
					*nfrontp++ = '\0';
			}
		}
		if (FD_ISSET(f, &obits) && (nfrontp - nbackp) > 0)
			netflush();
		if (ncc > 0)
			telrcv();
		if (FD_ISSET(p, &obits) && (pfrontp - pbackp) > 0)
			ptyflush();
	}
	cleanup();
}
	
/*
 * State for recv fsm
 */
#define	TS_DATA		0	/* base state */
#define	TS_IAC		1	/* look for double IAC's */
#define	TS_CR		2	/* CR-LF ->'s CR */
#define	TS_SB		3	/* throw away begin's... */
#define	TS_SE		4	/* ...end's (suboption negotiation) */
#define	TS_WILL		5	/* will option negotiation */
#define	TS_WONT		6	/* wont " */
#define	TS_DO		7	/* do " */
#define	TS_DONT		8	/* dont " */

telrcv()
{
	register int c;
	static int state = TS_DATA;

	while (ncc > 0) {
		if ((&ptyobuf[BUFSIZ] - pfrontp) < 2)
			return;
		c = *netip++ & 0377, ncc--;
		switch (state) {

		case TS_CR:
			state = TS_DATA;
			if ((c == 0) || (c == '\n')) {
				break;
			}
			/* FALL THROUGH */

		case TS_DATA:
			if (c == IAC) {
				state = TS_IAC;
				break;
			}
			if (inter > 0)
				break;

			/*
			 * We now map \r\n ==> \r for pragmatic reasons.
			 * Many client implementations send \r\n when
			 * the user hits the CarriageReturn key.
			 *
			 * We USED to map \r\n ==> \n, since \r\n says
			 * that we want to be in column 1 of the next
			 * printable line, and \n is the standard
			 * unix way of saying that (\r is only good
			 * if CRMOD is set, which it normally is).
			 */
			if ((c == '\r') && (hisopts[TELOPT_BINARY] == OPT_NO)) {
				state = TS_CR;
			}
			*pfrontp++ = c;
			break;

		case TS_IAC:
			switch (c) {

			/*
			 * Send the process on the pty side an
			 * interrupt.  Do this with a NULL or
			 * interrupt char; depending on the tty mode.
			 */
			case IP:
				interrupt();
				break;

			case BREAK:
				sendbrk();
				break;

			/*
			 * Are You There?
			 */
			case AYT:
				strcpy(nfrontp, "\r\n[Yes]\r\n");
				nfrontp += 9;
				break;

			/*
			 * Abort Output
			 */
			case AO: {
					struct ltchars tmpltc;

					ptyflush();	/* half-hearted */
					ioctl(pty, TIOCGLTC, &tmpltc);
					if (tmpltc.t_flushc != '\377') {
						*pfrontp++ = tmpltc.t_flushc;
					}
					netclear();	/* clear buffer back */
					*nfrontp++ = IAC;
					*nfrontp++ = DM;
					neturg = nfrontp-1; /* off by one XXX */
					break;
				}

			/*
			 * Erase Character and
			 * Erase Line
			 */
			case EC:
			case EL: {
					struct sgttyb b;
					char ch;

					ptyflush();	/* half-hearted */
					ioctl(pty, TIOCGETP, &b);
					ch = (c == EC) ?
						b.sg_erase : b.sg_kill;
					if (ch != '\377') {
						*pfrontp++ = ch;
					}
					break;
				}

			/*
			 * Check for urgent data...
			 */
			case DM:
				SYNCHing = stilloob(net);
				settimer(gotDM);
				break;


			/*
			 * Begin option subnegotiation...
			 */
			case SB:
				state = TS_SB;
				continue;

			case WILL:
				state = TS_WILL;
				continue;

			case WONT:
				state = TS_WONT;
				continue;

			case DO:
				state = TS_DO;
				continue;

			case DONT:
				state = TS_DONT;
				continue;

			case IAC:
				*pfrontp++ = c;
				break;
			}
			state = TS_DATA;
			break;

		case TS_SB:
			if (c == IAC) {
				state = TS_SE;
			} else {
				SB_ACCUM(c);
			}
			break;

		case TS_SE:
			if (c != SE) {
				if (c != IAC) {
					SB_ACCUM(IAC);
				}
				SB_ACCUM(c);
				state = TS_SB;
			} else {
				SB_TERM();
				suboption();	/* handle sub-option */
				state = TS_DATA;
			}
			break;

		case TS_WILL:
			if (hisopts[c] != OPT_YES)
				willoption(c);
			state = TS_DATA;
			continue;

		case TS_WONT:
			if (hisopts[c] != OPT_NO)
				wontoption(c);
			state = TS_DATA;
			continue;

		case TS_DO:
			if (myopts[c] != OPT_YES)
				dooption(c);
			state = TS_DATA;
			continue;

		case TS_DONT:
			if (myopts[c] != OPT_NO) {
				dontoption(c);
			}
			state = TS_DATA;
			continue;

		default:
			syslog(LOG_ERR, "telnetd: panic state=%d\n", state);
			printf("telnetd: panic state=%d\n", state);
			exit(1);
		}
	}
}

willoption(option)
	int option;
{
	char *fmt;

	switch (option) {

	case TELOPT_BINARY:
		mode(RAW, 0);
		fmt = doopt;
		break;

	case TELOPT_ECHO:
		not42 = 0;		/* looks like a 4.2 system */
		/*
		 * Now, in a 4.2 system, to break them out of ECHOing
		 * (to the terminal) mode, we need to send a "WILL ECHO".
		 * Kludge upon kludge!
		 */
		if (myopts[TELOPT_ECHO] == OPT_YES) {
		    dooption(TELOPT_ECHO);
		}
		fmt = dont;
		break;

	case TELOPT_TTYPE:
		settimer(ttypeopt);
		if (hisopts[TELOPT_TTYPE] == OPT_YES_BUT_ALWAYS_LOOK) {
		    hisopts[TELOPT_TTYPE] = OPT_YES;
		    return;
		}
		fmt = doopt;
		break;

	case TELOPT_SGA:
		fmt = doopt;
		break;

	case TELOPT_TM:
		fmt = dont;
		break;

	default:
		fmt = dont;
		break;
	}
	if (fmt == doopt) {
		hisopts[option] = OPT_YES;
	} else {
		hisopts[option] = OPT_NO;
	}
	(void) sprintf(nfrontp, fmt, option);
	nfrontp += sizeof (dont) - 2;
}

wontoption(option)
	int option;
{
	char *fmt;

	switch (option) {
	case TELOPT_ECHO:
		not42 = 1;		/* doesn't seem to be a 4.2 system */
		break;

	case TELOPT_BINARY:
		mode(0, RAW);
		break;

	case TELOPT_TTYPE:
	    settimer(ttypeopt);
	    break;
	}

	fmt = dont;
	hisopts[option] = OPT_NO;
	sprintf(nfrontp, fmt, option);
	nfrontp += sizeof (doopt) - 2;
}

dooption(option)
	int option;
{
	char *fmt;

	switch (option) {

	case TELOPT_TM:
		fmt = wont;
		break;

	case TELOPT_ECHO:
		mode(ECHO|CRMOD, 0);
		fmt = will;
		break;

	case TELOPT_BINARY:
		mode(RAW, 0);
		fmt = will;
		break;

	case TELOPT_SGA:
		fmt = will;
		break;

	default:
		fmt = wont;
		break;
	}
	if (fmt == will) {
	    myopts[option] = OPT_YES;
	} else {
	    myopts[option] = OPT_NO;
	}
	sprintf(nfrontp, fmt, option);
	nfrontp += sizeof (doopt) - 2;
}


dontoption(option)
int option;
{
    char *fmt;

    switch (option) {
    case TELOPT_ECHO:		/* we should stop echoing */
	mode(0, ECHO|CRMOD);
	fmt = wont;
	break;

    default:
	fmt = wont;
	break;
    }

    if (fmt = wont) {
	myopts[option] = OPT_NO;
    } else {
	myopts[option] = OPT_YES;
    }
    (void) sprintf(nfrontp, fmt, option);
    nfrontp += sizeof (wont) - 2;
}

/*
 * suboption()
 *
 *	Look at the sub-option buffer, and try to be helpful to the other
 * side.
 *
 *	Currently we recognize:
 *
 *	Terminal type is
 */

suboption()
{
    switch (SB_GET()) {
    case TELOPT_TTYPE: {		/* Yaaaay! */
	static char terminalname[5+41] = "TERM=";

	settimer(ttypesubopt);

	if (SB_GET() != TELQUAL_IS) {
	    return;		/* ??? XXX but, this is the most robust */
	}

	terminaltype = terminalname+strlen(terminalname);

	while ((terminaltype < (terminalname + sizeof terminalname-1)) &&
								    !SB_EOF()) {
	    register int c;

	    c = SB_GET();
	    if (isupper(c)) {
		c = tolower(c);
	    }
	    *terminaltype++ = c;    /* accumulate name */
	}
	*terminaltype = 0;
	terminaltype = terminalname;
	break;
    }

    default:
	;
    }
}

mode(on, off)
	int on, off;
{
	struct sgttyb b;

	ptyflush();
	ioctl(pty, TIOCGETP, &b);
	b.sg_flags |= on;
	b.sg_flags &= ~off;
	ioctl(pty, TIOCSETP, &b);
}

/*
 * Send interrupt to process on other side of pty.
 * If it is in raw mode, just write NULL;
 * otherwise, write intr char.
 */
interrupt()
{
	struct sgttyb b;
	struct tchars tchars;

	ptyflush();	/* half-hearted */
	ioctl(pty, TIOCGETP, &b);
	if (b.sg_flags & RAW) {
		*pfrontp++ = '\0';
		return;
	}
	*pfrontp++ = ioctl(pty, TIOCGETC, &tchars) < 0 ?
		'\177' : tchars.t_intrc;
}

/*
 * Send quit to process on other side of pty.
 * If it is in raw mode, just write NULL;
 * otherwise, write quit char.