date and time created 87/10/06 00:36:06 by edward

[unix-history] / usr / src / usr.bin / telnet / network.c

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>

#include <errno.h>

#include <arpa/telnet.h>

#include "defines.h"
#include "externs.h"

char	netobuf[2*BUFSIZ], *nfrontp, *nbackp;
static char	*neturg;		/* one past last byte of urgent data */

/*
 * Initialize internal network data structures.
 */

init_network()
{
    nfrontp = nbackp = netobuf;
    NetTrace = stdout;
}


/*
 * Check to see if any out-of-band data exists on a socket (for
 * Telnet "synch" processing).
 */

int
stilloob(s)
int	s;		/* socket number */
{
    static struct timeval timeout = { 0 };
    fd_set	excepts;
    int value;

    do {
	FD_ZERO(&excepts);
	FD_SET(s, &excepts);
	value = select(s+1, (fd_set *)0, (fd_set *)0, &excepts, &timeout);
    } while ((value == -1) && (errno == EINTR));

    if (value < 0) {
	perror("select");
	quit();
    }
    if (FD_ISSET(s, &excepts)) {
	return 1;
    } else {
	return 0;
    }
}


/*
 *  setneturg()
 *
 *	Sets "neturg" to the current location.
 */

void
setneturg()
{
    neturg = NETLOC()-1;	/* Some systems are off by one XXX */
}


/*
 *  netflush
 *		Send as much data as possible to the network,
 *	handling requests for urgent data.
 *
 *		The return value indicates whether we did any
 *	useful work.
 */


int
netflush()
{
    int n;

    if ((n = nfrontp - nbackp) > 0) {
	if (!neturg) {
	    n = send(net, nbackp, n, 0);	/* normal write */
	} else {
	    n = neturg - nbackp;
	    /*
	     * In 4.2 (and 4.3) systems, there is some question about
	     * what byte in a sendOOB operation is the "OOB" data.
	     * To make ourselves compatible, we only send ONE byte
	     * out of band, the one WE THINK should be OOB (though
	     * we really have more the TCP philosophy of urgent data
	     * rather than the Unix philosophy of OOB data).
	     */
	    if (n > 1) {
		n = send(net, nbackp, n-1, 0);	/* send URGENT all by itself */
	    } else {
		n = send(net, nbackp, n, MSG_OOB);	/* URGENT data */
	    }
	}
    }
    if (n < 0) {
	if (errno != ENOBUFS && errno != EWOULDBLOCK) {
	    setcommandmode();
	    perror(hostname);
	    NetClose(net);
	    neturg = 0;
	    longjmp(peerdied, -1);
	    /*NOTREACHED*/
	}
	n = 0;
    }
    if (netdata && n) {
	Dump('>', nbackp, n);
    }
    nbackp += n;
    if (nbackp >= neturg) {
	neturg = 0;
    }
    if (nbackp == nfrontp) {
	nbackp = nfrontp = netobuf;
    }
    return n > 0;
}
\f
/*
 * nextitem()
 *
 *	Return the address of the next "item" in the TELNET data
 * stream.  This will be the address of the next character if
 * the current address is a user data character, or it will
 * be the address of the character following the TELNET command
 * if the current address is a TELNET IAC ("I Am a Command")
 * character.
 */

static char *
nextitem(current)
char	*current;
{
    if ((*current&0xff) != IAC) {
	return current+1;
    }
    switch (*(current+1)&0xff) {
    case DO:
    case DONT:
    case WILL:
    case WONT:
	return current+3;
    case SB:		/* loop forever looking for the SE */
	{
	    register char *look = current+2;

	    for (;;) {
		if ((*look++&0xff) == IAC) {
		    if ((*look++&0xff) == SE) {
			return look;
		    }
		}
	    }
	}
    default:
	return current+2;
    }
}
/*
 * netclear()
 *
 *	We are about to do a TELNET SYNCH operation.  Clear
 * the path to the network.
 *
 *	Things are a bit tricky since we may have sent the first
 * byte or so of a previous TELNET command into the network.
 * So, we have to scan the network buffer from the beginning
 * until we are up to where we want to be.
 *
 *	A side effect of what we do, just to keep things
 * simple, is to clear the urgent data pointer.  The principal
 * caller should be setting the urgent data pointer AFTER calling
 * us in any case.
 */

void
netclear()
{
    register char *thisitem, *next;
    char *good;
#define	wewant(p)	((nfrontp > p) && ((*p&0xff) == IAC) && \
				((*(p+1)&0xff) != EC) && ((*(p+1)&0xff) != EL))

    thisitem = netobuf;

    while ((next = nextitem(thisitem)) <= nbackp) {
	thisitem = next;
    }

    /* Now, thisitem is first before/at boundary. */

    good = netobuf;	/* where the good bytes go */

    while (nfrontp > thisitem) {
	if (wewant(thisitem)) {
	    int length;

	    next = thisitem;
	    do {
		next = nextitem(next);
	    } while (wewant(next) && (nfrontp > next));
	    length = next-thisitem;
	    memcpy(good, thisitem, length);
	    good += length;
	    thisitem = next;
	} else {
	    thisitem = nextitem(thisitem);
	}
    }

    nbackp = netobuf;
    nfrontp = good;		/* next byte to be sent */
    neturg = 0;
}