The TFTP client, and possibly server, doesn't handle file sizes larger then
32 MBytes properly. This is attributed to the variable callouts (int
instead of short int, etc) and truncation of like, but different sized,
variables.

The current implementation will transfer 32 MBytes (or one block size less
then 32 MBytes) and then time out. The following tftp.c file (a messy hack,
with lies) produces a fix for this problem, that with limited testing seems
to work well.

-----------------modified tftp.c-----------------
/*
 * Copyright (c) 1983 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.
 */

/*
 * From: @(#)tftp.c	5.10 (Berkeley) 3/1/91
 */
char tftp_rcsid[] = 
  "$Id: tftp.c,v 1.8 1999/12/12 18:05:06 dholland Exp $";

/* Many bug fixes are from Jim Guyton <guyton@rand-unix> */

/*
 * TFTP User Program -- Protocol Machines
 */
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>

#include <netinet/in.h>
/* #include <netinet/ip.h> <--- unused? */
#include <arpa/tftp.h>

#include <signal.h>
#include <stdio.h>
#include <errno.h>
#include <setjmp.h>
#include <unistd.h>
#include <string.h>

#include "tftpsubs.h"

#include "../version.h"

extern  struct sockaddr_in s_inn;  /* filled in by main */
extern  int     f;                      /* the opened socket */
extern  int     trace;
extern  int     verbose;
extern  int     rexmtval;
extern  int     maxtimeout;
extern sigjmp_buf toplevel;
void sendfile(int fd, char *name, char *modestr);
void recvfile(int fd, char *name, char *modestr);


#define PKTSIZE    SEGSIZE+4
static char ackbuf[PKTSIZE];
static int timeout;
static sigjmp_buf timeoutbuf;


static int makerequest(int request, char *name, 
		       struct tftphdr *tp, char *mode);
static void nak(int errnor);
static void tpacket(const char *s, struct tftphdr *tp, int n);
static void startclock(void);
static void stopclock(void);
static void printstats(const char *direction, unsigned long amount);

static
void
timer(int signum)
{
	(void)signum;

	timeout += rexmtval;
	if (timeout >= maxtimeout) {
		printf("Transfer timed out.\n");
		siglongjmp(toplevel, -1);
	}
	siglongjmp(timeoutbuf, 1);
}

/*
 * Send the requested file.
 */
void
sendfile(int fd, char *name, char *mode)
{
	register struct tftphdr *ap;       /* data and ack packets */
	struct tftphdr *dp;
	int sendreq = 1;
	volatile unsigned short int block = 0;
	volatile int size = 0;
	int n;
	volatile unsigned long amount = 0;
	struct sockaddr_in from;
	socklen_t fromlen;
	volatile int convert;            /* true if doing nl->crlf conversion */
	FILE *file;

	startclock();           /* start stat's clock */
	dp = r_init();          /* reset fillbuf/read-ahead code */
	ap = (struct tftphdr *)ackbuf;
	file = fdopen(fd, "r");
	convert = !strcmp(mode, "netascii");

	signal(SIGALRM, timer);
	do {
		if (sendreq)
			size = makerequest(WRQ, name, dp, mode) - 4;
		else {
		/*      size = read(fd, dp->th_data, SEGSIZE);   */
			size = readit(file, &dp, convert);
			if (size < 0) {
				nak(errno + 100);
				break;
			}
			dp->th_opcode = htons((u_short)DATA);
			dp->th_block = htons((u_short)block);
		}
		timeout = 0;
		(void) sigsetjmp(timeoutbuf, 1);
send_data:
		if (trace)
			tpacket("sent", dp, size + 4);
		n = sendto(f, dp, size + 4, 0,
		    (struct sockaddr *)&s_inn, sizeof(s_inn));
		if (n != size + 4) {
			perror("tftp: sendto");
			goto abort;
		}
		read_ahead(file, convert);
		for ( ; ; ) {
			alarm(rexmtval);
			do {
				fromlen = sizeof (from);
				n = recvfrom(f, ackbuf, sizeof (ackbuf), 0,
				    (struct sockaddr *)&from, &fromlen);
			} while (n <= 0);
			alarm(0);
			if (n < 0) {
				perror("tftp: recvfrom");
				goto abort;
			}
			s_inn.sin_port = from.sin_port;   /* added */
			if (trace)
				tpacket("received", ap, n);
			/* should verify packet came from server */
			ap->th_opcode = ntohs(ap->th_opcode);
			ap->th_block = ntohs(ap->th_block);
			if (ap->th_opcode == ERROR) {
				printf("Error code %d: %s\n", ap->th_code,
					ap->th_msg);
				goto abort;
			}
			if (ap->th_opcode == ACK) {
				volatile int j = 0;

				if (ap->th_block == block) {
					break;
				}
				/* On an error, try to synchronize
				 * both sides.
				 */
				j = synchnet(f);
				if (j && trace) {
					printf("discarded %d packets\n",
							j);
				}
				if (ap->th_block == (block-1)) {
					goto send_data;
				}
			}
		}
		if (sendreq) {
			sendreq = 0;
			size = SEGSIZE; /* lie to stay in the while loop */
		} else {
			amount += size;
		}
		block++;
	} while (size == SEGSIZE);
abort:
	fclose(file);
	stopclock();
	if (amount > 0)
		printstats("Sent", amount);
}

/*
 * Receive a file.
 */
void
recvfile(int fd, char *name, char *mode)
{
	register struct tftphdr *ap;
	struct tftphdr *dp;
	volatile unsigned short int block = 1;
	volatile int size = 0;
	int n; 
	volatile unsigned long amount = 0;
	struct sockaddr_in from;
	socklen_t fromlen;
	volatile int firsttrip = 1;
	FILE *file;
	volatile int convert;            /* true if converting crlf -> lf */

	startclock();
	dp = w_init();
	ap = (struct tftphdr *)ackbuf;
	file = fdopen(fd, "w");
	convert = !strcmp(mode, "netascii");

	signal(SIGALRM, timer);
	do {
		if (firsttrip) {
			size = makerequest(RRQ, name, ap, mode);
			firsttrip = 0;
		} else {
			ap->th_opcode = htons((u_short)ACK);
			ap->th_block = htons((u_short)(block));
			size = 4;
			block++;
		}
		timeout = 0;
		(void) sigsetjmp(timeoutbuf, 1);
send_ack:
		if (trace)
			tpacket("sent", ap, size);
		if (sendto(f, ackbuf, size, 0, (struct sockaddr *)&s_inn,
		    sizeof (s_inn)) != size) {
			alarm(0);
			perror("tftp: sendto");
			goto abort;
		}
		write_behind(file, convert);
		for ( ; ; ) {
			alarm(rexmtval);
			do  {
				fromlen = sizeof (from);
				n = recvfrom(f, dp, PKTSIZE, 0,
				    (struct sockaddr *)&from, &fromlen);
			} while (n <= 0);
			alarm(0);
			if (n < 0) {
				perror("tftp: recvfrom");
				goto abort;
			}
			s_inn.sin_port = from.sin_port;   /* added */
			if (trace)
				tpacket("received", dp, n);
			/* should verify client address */
			dp->th_opcode = ntohs(dp->th_opcode);
			dp->th_block = ntohs(dp->th_block);
			if (dp->th_opcode == ERROR) {
				printf("Error code %d: %s\n", dp->th_code,
					dp->th_msg);
				goto abort;
			}
			if (dp->th_opcode == DATA) {
				volatile int j = 0;

				if (dp->th_block == block) {
					break;          /* have next packet */
				}
				/* On an error, try to synchronize
				 * both sides.
				 */
				j = synchnet(f);
				if (j && trace) {
					printf("discarded %d packets\n", j);
				}
				if (dp->th_block == (block-1)) {
					goto send_ack;  /* resend ack */
				}
			}
		}
	/*      size = write(fd, dp->th_data, n - 4); */
		size = writeit(file, &dp, n - 4, convert);
		if (size < 0) {
			nak(errno + 100);
			break;
		}
		amount += size;
	} while (size == SEGSIZE);
abort:                                          /* ok to ack, since user */
	ap->th_opcode = htons((u_short)ACK);    /* has seen err msg */
	ap->th_block = htons((u_short)block);
	(void) sendto(f, ackbuf, 4, 0, (struct sockaddr *)&s_inn, sizeof(s_inn));
	write_behind(file, convert);     /* flush last buffer */
	fclose(file);
	stopclock();
	if (amount > 0)
		printstats("Received", amount);
}

int
makerequest(int request, char *name, struct tftphdr *tp, char *mode)
{
	register char *cp;

	tp->th_opcode = htons((u_short)request);
	cp = tp->th_stuff;
	strcpy(cp, name);
	cp += strlen(name);
	*cp++ = '\0';
	strcpy(cp, mode);
	cp += strlen(mode);
	*cp++ = '\0';
	return (cp - (char *)tp);
}

struct errmsg {
	int e_code;
	const char *e_msg;
} errmsgs[] = {
	{ EUNDEF,	"Undefined error code" },
	{ ENOTFOUND,	"File not found" },
	{ EACCESS,	"Access violation" },
	{ ENOSPACE,	"Disk full or allocation exceeded" },
	{ EBADOP,	"Illegal TFTP operation" },
	{ EBADID,	"Unknown transfer ID" },
	{ EEXISTS,	"File already exists" },
	{ ENOUSER,	"No such user" },
	{ -1,		0 }
};

/*
 * Send a nak packet (error message).
 * Error code passed in is one of the
 * standard TFTP codes, or a UNIX errno
 * offset by 100.
 */
void
nak(int error)
{
	register struct errmsg *pe;
	register struct tftphdr *tp;
	int length;

	tp = (struct tftphdr *)ackbuf;
	tp->th_opcode = htons((u_short)ERROR);
	tp->th_code = htons((u_short)error);
	for (pe = errmsgs; pe->e_code >= 0; pe++)
		if (pe->e_code == error)
			break;
	if (pe->e_code < 0) {
		pe->e_msg = strerror(error - 100);
		tp->th_code = EUNDEF;
	}
	strcpy(tp->th_msg, pe->e_msg);
	length = strlen(pe->e_msg) + 4;
	if (trace)
		tpacket("sent", tp, length);
	if (sendto(f, ackbuf, length, 0, (struct sockaddr *)&s_inn,
	    sizeof (s_inn)) != length)
		perror("nak");
}

static
void
tpacket(const char *s, struct tftphdr *tp, int n)
{
	static const char *opcodes[] =
	   { "#0", "RRQ", "WRQ", "DATA", "ACK", "ERROR" };
	register char *cp, *file;
	u_short op = ntohs(tp->th_opcode);

	if (op < RRQ || op > ERROR)
		printf("%s opcode=%x ", s, op);
	else
		printf("%s %s ", s, opcodes[op]);
	switch (op) {

	case RRQ:
	case WRQ:
		n -= 2;
		file = cp = tp->th_stuff;
		cp = cp + strlen(cp);
		printf("<file=%s, mode=%s>\n", file, cp + 1);
		break;

	case DATA:
		printf("<block=%d, %d bytes>\n", ntohs(tp->th_block), n - 4);
		break;

	case ACK:
		printf("<block=%d>\n", ntohs(tp->th_block));
		break;

	case ERROR:
		printf("<code=%d, msg=%s>\n", ntohs(tp->th_code), tp->th_msg);
		break;
	}
}

struct timeval tstart;
struct timeval tstop;
struct timezone zone;

void
startclock(void) {
	gettimeofday(&tstart, &zone);
}

void
stopclock(void) {
	gettimeofday(&tstop, &zone);
}

void
printstats(const char *direction, unsigned long amount)
{
	double delta;
			/* compute delta in 1/10's second units */
	delta = ((tstop.tv_sec*10.)+(tstop.tv_usec/100000)) -
		((tstart.tv_sec*10.)+(tstart.tv_usec/100000));
	delta = delta/10.;      /* back to seconds */
	printf("%s %ld bytes in %.1f seconds", direction, amount, delta);
	if (verbose)
		printf(" [%.0f bits/sec]", (amount*8.)/delta);
	putchar('\n');
}