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tftp_subs.cpp
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tftp_subs.cpp
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/*
* 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: @(#)tftpsubs.c 5.6 (Berkeley) 2/28/91
*/
// char subs_rcsid[] = "$Id: tftpsubs.c,v 1.8 2000/07/22 19:06:29 dholland Exp
// $";
/* 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 "tftp/tftpsubs.h"
#include <csignal>
#include <cstring>
#include <netinet/in.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <syslog.h>
#include <unistd.h>
constexpr size_t max_buffer{2};
struct buffer
{
ssize_t counter; /* size of data in buffer, or flag */
char buf[MAXPKTSIZE]; /* RFC2348 room for data packet */
};
static struct buffer bfs[max_buffer];
/* Values for buffer.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 size_t nextone; /* index of next buffer to use */
static size_t current; /* index of buffer in use */
/* control flags for crlf conversions */
static bool newline = false; /* fillbuf: in middle of newline expansion */
static int prevchar = -1; /* putbuf: previous char (cr check) */
/*
* init for either read-ahead or write-behind
* zero for write-behind, one for read-head
*/
struct tftphdr *rw_init(int x)
{
newline = false; /* 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 reinterpret_cast<struct tftphdr *>(bfs[0].buf);
}
#if 0
/*
* 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,
bool convert /* if true, convert to ascii */)
{
struct buffer *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, bool convert /* if true, convert to ascii */)
{
int i;
char *p;
int c;
struct buffer *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) {
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 = false;
} else {
c = getc(file);
if (c == EOF) {
break;
}
if (c == '\n' || c == '\r') {
prevchar = c;
c = '\r';
newline = true;
}
}
*p++ = c;
}
b->counter = (int)(p - dp->th_data);
}
#endif
/*
* Update count associated with the buffer, get new buffer from the queue.
* NOTE: Calls write_behind only if next buffer not available.
*/
ssize_t writeit(FILE *file, struct tftphdr **dpp, size_t count, bool convert)
{
ssize_t written = count;
// NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
bfs[current].counter = count; /* set size of data to write */
current = ((current + 1) % max_buffer); /* switch to other buffer */
// NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
if (bfs[current].counter != BF_FREE) { /* if not free */
written = write_behind(file, convert); /* flush it */
}
// NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
bfs[current].counter = BF_ALLOC; /* mark as alloc'd */
*dpp = reinterpret_cast<struct tftphdr *>(bfs[current].buf);
return written; // this may 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.
*/
ssize_t write_behind(FILE *file, bool /*convert*/)
{
// NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
struct buffer *b = &bfs[nextone];
if (b->counter < -1) { /* anything to flush? */
// NOLINTNEXTLINE(cppcoreguidelines-pro-type-vararg)
syslog(LOG_INFO, "tftpd: write() nothing to flush!\n");
return 0; /* just nop if nothing to do */
}
ssize_t const count = b->counter; /* remember byte count */
b->counter = BF_FREE; /* reset flag */
auto *dp = reinterpret_cast<struct tftphdr *>(b->buf);
nextone = ((nextone + 1) % max_buffer); /* incr for next time */
// NOLINTNEXTLINE(cppcoreguidelines-pro-type-union-access)
char *buf = dp->th_data;
if (count < 0) {
// NOLINTNEXTLINE(cppcoreguidelines-pro-type-vararg)
syslog(LOG_ERR, "tftpd: write() invalid buffer count!\n");
return -1; /* TBD: no nak logic! CK */
}
#ifndef USE_CONVERT
return write(fileno(file), buf, count);
#else
if (!convert) {
return write(fileno(file), buf, count);
}
char *p = buf;
ssize_t ct = count;
while ((ct--) != 0) { /* loop over the buffer */
int c; /* current character */
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;
#endif
}