tftpsubs.c

unix下tftp服务器源码

/* tftp-hpa: $Id: tftpsubs.c,v 1.7 2001/11/16 20:15:27 hpa Exp $ */

/* $OpenBSD: tftpsubs.c,v 1.2 1996/06/26 05:40:36 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. 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.
 */

#include "tftpsubs.h"

#ifndef lint
/* static char sccsid[] = "@(#)tftpsubs.c	8.1 (Berkeley) 6/6/93"; */
/* static char rcsid[] = "$OpenBSD: tftpsubs.c,v 1.2 1996/06/26 05:40:36 deraadt Exp $"; */
static const char *rcsid UNUSED =
"tftp-hpa: $Id: tftpsubs.c,v 1.7 2001/11/16 20:15:27 hpa Exp $";
#endif /* not lint */

/* 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/ioctl.h>

#define PKTSIZE MAX_SEGSIZE+4       /* should be moved to tftp.h */

int segsize = SEGSIZE;		/* Default segsize */

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

				/* 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 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) */

static struct tftphdr *rw_init(int);

struct tftphdr *w_init() { return rw_init(0); }         /* write-behind */
struct tftphdr *r_init() { return rw_init(1); }         /* read-ahead */

/* init for either read-ahead or write-behind */
/* x == 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)
{
	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);      /* 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 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, segsize);
		return;
	}

	p = dp->th_data;
	for (i = 0 ; i < segsize; 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 */
		(void)write_behind(file, convert); /* flush it */
	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) return -1;      /* nak logic? */

	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 */
		   fseek(file, -1, 1);  /* smash lf on top of the cr */
		else
		   if (c == '\0')       /* if have cr,nul then */
			goto skipit;    /* just skip over the putc */
		/* else just fall through and allow it */
	    }
	    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)		/* socket to flush */
{
  int pktcount = 0;
  char rbuf[PKTSIZE];
  struct sockaddr_in from;
  int fromlen;
  fd_set socketset;
  struct timeval notime;
  
  while ( 1 ) {
    notime.tv_sec = notime.tv_usec = 0;
    
    FD_ZERO(&socketset);
    FD_SET(f, &socketset);
    
    if ( select(f, &socketset, NULL, NULL, &notime) <= 0 )
      break;			/* Nothing to read */
	
    /* Otherwise drain the packet */
    pktcount++;
    fromlen = sizeof from;
    (void) recvfrom(f, rbuf, sizeof (rbuf), 0,
		    (struct sockaddr *)&from, &fromlen);
  }

  return pktcount;		/* Return packets drained */
}