encode.c

来自「此dns服务器是在mydns基础上改写」· C语言 代码 · 共 199 行

/**************************************************************************************************
	$Id: encode.c,v 1.36 2006/01/18 20:46:47 bboy Exp $

	Copyright (C) 2002-2005  Don Moore <[e-mail]>

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at Your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
**************************************************************************************************/

#include "named.h"

/* Make this nonzero to enable debugging for this source file */
#define	DEBUG_ENCODE	1

/* Set this to nonzero to disable encoding */
#define	NO_ENCODING		0


/**************************************************************************************************
	NAME_REMEMBER
	Adds the specified name + offset to the `Labels' array within the specified task.
**************************************************************************************************/
inline int
name_remember(TASK *t, char *name, unsigned int offset)
{
	if (!name || strlen(name) > 64)						/* Don't store labels > 64 bytes in length */
		return (0);

#if DYNAMIC_NAMES
	if (!t->Names)
	{
		if (!(t->Names = (char **)malloc(1 * sizeof(char *))))
			Err(_("out of memory"));
	}
	else
	{
		if (!(t->Names = realloc(t->Names, (t->numNames + 1) * sizeof(char *))))
			Err(_("out of memory"));
	}
	if (!(t->Names[t->numNames] = strdup(name)))
		Err("strdup");
	if (!t->Offsets)
	{
		if (!(t->Offsets = malloc(sizeof(unsigned int))))
			Err(_("out of memory"));
	}
	else
	{
		if (!(t->Offsets = realloc(t->Offsets, (t->numNames + 1) * sizeof(unsigned int))))
			Err(_("out of memory"));
	}
#else
	if (t->numNames >= MAX_STORED_NAMES - 1)
		return dnserror(t, DNS_RCODE_SERVFAIL, ERR_RR_NAME_TOO_LONG);
	strncpy(t->Names[t->numNames], name, sizeof(t->Names[t->numNames]) - 1);
#endif

#if DEBUG_ENABLED && DEBUG_ENCODE
	Debug("remembering name \"%s\" at offset %u", name, offset);
#endif

	t->Offsets[t->numNames] = offset;
	t->numNames++;
	return (0);
}
/*--- name_remember() ---------------------------------------------------------------------------*/


/**************************************************************************************************
	NAME_FORGET
	Forget all names in the specified task.
**************************************************************************************************/
inline void
name_forget(TASK *t)
{
#if DYNAMIC_NAMES
	register int n;

	for (n = 0; n < t->numNames; n++)
		Free(t->Names[n]);
	Free(t->Names);
	Free(t->Offsets);
#endif
	t->numNames = 0;
}
/*--- name_forget() -----------------------------------------------------------------------------*/


/**************************************************************************************************
	NAME_FIND
	Searches the task's remembered names arary for `name'.
	Returns the offset within the reply if found, or 0 if not found.
**************************************************************************************************/
unsigned int
name_find(TASK *t, char *name)
{
	register unsigned int n;

	for (n = 0; n < t->numNames; n++)
		if (!strcasecmp(t->Names[n], name))
		{
#if DEBUG_ENABLED && DEBUG_ENCODE
			Debug("found name \"%s\" at offset %u", name, t->Offsets[n]);
#endif
			return (t->Offsets[n]);
		}
	return (0);
}
/*--- name_find() -------------------------------------------------------------------------------*/


/**************************************************************************************************
	NAME_ENCODE
	Encodes `in_name' into `dest'.  Returns the length of data in `dest', or -1 on error.
	If `name' is not NULL, it should be DNS_MAXNAMELEN bytes or bigger.
**************************************************************************************************/
int
name_encode(TASK *t, char *dest, char *name, unsigned int dest_offset, int compression)
{
	char				namebuf[DNS_MAXNAMELEN+1];
	register char	*c, *d, *this_name, *cp;
	register int	len = 0;
	register unsigned int offset;

#if DEBUG_ENABLED && DEBUG_ENCODE
	Debug("encoding \"%s\" at dest offset %u", name, dest_offset);
#endif

	strncpy(namebuf, name, sizeof(namebuf)-1);

	/* Label must end in the root zone (with a dot) */
	if (LASTCHAR(namebuf) != '.')
		return dnserror(t, DNS_RCODE_SERVFAIL, ERR_NAME_FORMAT);

	/* Examine name one label at a time */
	for (c = namebuf, d = dest; *c; c++)
		if (c == namebuf || *c == '.')
		{
			if (!c[1])
			{
				len++;
				if (len > DNS_MAXNAMELEN)
					return dnserror(t, DNS_RCODE_SERVFAIL, ERR_RR_NAME_TOO_LONG);
				*d++ = 0;
				return (len);
			}
			this_name = (c == namebuf) ? c : (++c);

#if !NO_ENCODING
			if (compression && !t->no_markers && (offset = name_find(t, this_name)))
			{
				/* Found marker for this name - output offset pointer and we're done */
				len += SIZE16;
				if (len > DNS_MAXNAMELEN)
					return dnserror(t, DNS_RCODE_SERVFAIL, ERR_RR_NAME_TOO_LONG);
				offset |= 0xC000;
				DNS_PUT16(d, offset);
				return (len);
			}
			else		/* No marker for this name; encode current label and store marker */
#endif
			{
				register unsigned int nlen;

				if ((cp = strchr(this_name, '.')))
					*cp = '\0';
				nlen = strlen(this_name);
				if (nlen > DNS_MAXLABELLEN)
					return dnserror(t, DNS_RCODE_SERVFAIL, ERR_RR_LABEL_TOO_LONG);
				len += nlen + 1;
				if (len > DNS_MAXNAMELEN)
					return dnserror(t, DNS_RCODE_SERVFAIL, ERR_RR_NAME_TOO_LONG);
				*d++ = (unsigned char)nlen;
				memcpy(d, this_name, nlen);
				d += nlen;
				if (cp)
					*cp = '.';
				if (!t->no_markers && (name_remember(t, this_name, dest_offset + (c - namebuf)) < 0))
					return (-1);
			}
		}
	return (len);
}
/*--- name_encode() -----------------------------------------------------------------------------*/

/* vi:set ts=3: */
/* NEED_PO */