path: root/usr.bin/tftp/tftpsubs.c

/*	$OpenBSD: tftpsubs.c,v 1.14 2009/10/27 23:59:44 deraadt Exp $	*/
/*	$NetBSD: tftpsubs.c,v 1.3 1994/12/08 09:51:31 jtc Exp $	*/

/*
 * Copyright (c) 1983, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Simple minded read-ahead/write-behind subroutines for tftp user and
 * server.  Written originally with multiple buffers in mind, but current
 * implementation has two buffer logic wired in.
 *
 * Todo:  add some sort of final error check so when the write-buffer
 * is finally flushed, the caller can detect if the disk filled up
 * (or had an i/o error) and return a nak to the other side.
 *
 *			Jim Guyton 10/85
 */

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

#include <netinet/in.h>
#include <arpa/tftp.h>

#include <stdio.h>
#include <unistd.h>

#include "tftpsubs.h"

					/* values for bf.counter */
#define BF_ALLOC	-3		/* alloc'd but not yet filled */
#define BF_FREE		-2		/* free */
/* [-1 .. SEGSIZE] = size of data in the data buffer */

static struct tftphdr	*rw_init(int);

struct bf {
	int	counter;		/* size of data in buffer, or flag */
	char	buf[SEGSIZE_MAX + 4];	/* room for data packet */
} bfs[2];

static int	nextone;	/* index of next buffer to use */
static int	current;	/* index of buffer in use */
				/* control flags for crlf conversions */
int		newline = 0;	/* fillbuf: in middle of newline expansion */
int		prevchar = -1;	/* putbuf: previous char (cr check) */

struct tftphdr *
w_init(void)
{
	return (rw_init(0));	/* write-behind */
}

struct tftphdr *
r_init(void)
{
	return (rw_init(1));	/* read-ahead */
}

/*
 * Init for either read-ahead or write-behind.
 * Zero for write-behind, one for read-head.
 */
static struct tftphdr *
rw_init(int x)
{
	newline = 0;			/* init crlf flag */
	prevchar = -1;
	bfs[0].counter = BF_ALLOC;	/* pass out the first buffer */
	current = 0;
	bfs[1].counter = BF_FREE;
	nextone = x;			/* ahead or behind? */

	return ((struct tftphdr *)bfs[0].buf);
}

/*
 * Have emptied current buffer by sending to net and getting ack.
 * Free it and return next buffer filled with data.
 */
int
readit(FILE *file, struct tftphdr **dpp, int convert, int segment_size)
{
	struct bf	*b;

	bfs[current].counter = BF_FREE;		/* free old one */
	current = !current;			/* "incr" current */

	b = &bfs[current];			/* look at new buffer */
	if (b->counter == BF_FREE)		/* if it's empty */
		read_ahead(file, convert, segment_size);	/* fill it */
	/* assert(b->counter != BF_FREE); */	/* check */
	*dpp = (struct tftphdr *)b->buf;	/* set caller's ptr */

	return (b->counter);
}

/*
 * Fill the input buffer, doing ascii conversions if requested.
 * Conversions are lf -> cr, lf and cr -> cr, nul.
 */
void
read_ahead(FILE *file, int convert, int segment_size)
{
	int		 i;
	char		*p;
	int		 c;
	struct bf	*b;
	struct tftphdr	*dp;

	b = &bfs[nextone];			/* look at "next" buffer */
	if (b->counter != BF_FREE)		/* nop if not free */
		return;
	nextone = !nextone;			/* "incr" next buffer ptr */

	dp = (struct tftphdr *)b->buf;

	if (convert == 0) {
		b->counter = read(fileno(file), dp->th_data, segment_size);
		return;
	}

	p = dp->th_data;
	for (i = 0; i < segment_size; i++) {
		if (newline) {
			if (prevchar == '\n')
				c = '\n';	/* lf to cr, lf */
			else
				c = '\0';	/* cr to cr, nul */
			newline = 0;
		} else {
			c = getc(file);
			if (c == EOF)
				break;
			if (c == '\n' || c == '\r') {
				prevchar = c;
				c = '\r';
				newline = 1;
			}
		}
	       *p++ = c;
	}
	b->counter = (int)(p - dp->th_data);
}

/*
 * Update count associated with the buffer, get new buffer
 * from the queue.  Calls write_behind only if next buffer not
 * available.
 */
int
writeit(FILE *file, struct tftphdr **dpp, int ct, int convert)
{
	bfs[current].counter = ct;		/* set size of data to write */
	current = !current;			/* switch to other buffer */
	if (bfs[current].counter != BF_FREE)	/* if not free */
		/* flush it */
		(void)write_behind(file, convert);
	bfs[current].counter = BF_ALLOC;	/* mark as alloc'd */
	*dpp =  (struct tftphdr *)bfs[current].buf;

	return (ct);				/* this is a lie of course */
}

/*
 * Output a buffer to a file, converting from netascii if requested.
 * CR, NUL -> CR and CR, LF -> LF.
 * Note spec is undefined if we get CR as last byte of file or a
 * CR followed by anything else.  In this case we leave it alone.
 */
int
write_behind(FILE *file, int convert)
{
	char		*buf;
	int		 count;
	int		 ct;
	char		*p;
	int		 c; /* current character */
	struct bf	*b;
	struct tftphdr	*dp;

	b = &bfs[nextone];
	if (b->counter < -1)		/* anything to flush? */
		return (0);		/* just nop if nothing to do */

	count = b->counter;		/* remember byte count */
	b->counter = BF_FREE;		/* reset flag */
	dp = (struct tftphdr *)b->buf;
	nextone = !nextone;		/* incr for next time */
	buf = dp->th_data;

	if (count <= 0)			/* nak logic? */
		return (-1);

	if (convert == 0)
		return (write(fileno(file), buf, count));

	p = buf;
	ct = count;
	while (ct--) {				/* loop over the buffer */
		c = *p++;			/* pick up a character */
		if (prevchar == '\r') {		/* if prev char was cr */
			if (c == '\n')		/* if have cr,lf then just */
				/* smash lf on top of the cr */
				fseek(file, -1, SEEK_CUR);
			else if (c == '\0')	/* if have cr,nul then */
				goto skipit;	/* just skip over the putc */
			/* FALLTHROUGH */
		}
		putc(c, file);
skipit:
		prevchar = c;
	}

	return (count);
}

/*
 * When an error has occurred, it is possible that the two sides
 * are out of synch.  Ie: that what I think is the other side's
 * response to packet N is really their response to packet N-1.
 *
 * So, to try to prevent that, we flush all the input queued up
 * for us on the network connection on our host.
 *
 * We return the number of packets we flushed (mostly for reporting
 * when trace is active).
 */
int
synchnet(int f)
{
	int			i, j = 0;
	char			rbuf[SEGSIZE_MIN];
	struct sockaddr_in	from;
	socklen_t		fromlen;

	for (;;) {
		(void)ioctl(f, FIONREAD, &i);
		if (i) {
			j++;
			fromlen = sizeof(from);
			(void)recvfrom(f, rbuf, sizeof(rbuf), 0,
			    (struct sockaddr *)&from, &fromlen);
		} else
			return (j);
	}
}