| Sergei Steshenko |
04-04-2010 09:23 AM |
Quote:
Originally Posted by btp10
(Post 3923724)
I have looked into the function source and I could not figure out anything from that as there are too many flags that I do not understand. Moreover, the source was pretty difficult to find so that when I did find the code I wasn't sure whether it was for the actual function that I am using or the source code for some other version of the function.
PS: I don't know whether you realize it or not but your response is ---- 1. Rude, 2. Not helpful at all. Thanks a lot anyways.
|
So, now copy the source into your program, changing the function name, and adding 'printf' statements, so you'll be able to trace which statements are executed and why you are getting the error message.
The above is trivial.
The source apparently is in 'glibc' - at least, this is where I find it.
The sources:
Code:
int
dn_expand(const u_char *msg, const u_char *eom, const u_char *src,
char *dst, int dstsiz)
{
int n = ns_name_uncompress(msg, eom, src, dst, (size_t)dstsiz);
if (n > 0 && dst[0] == '.')
dst[0] = '\0';
return (n);
}
Code:
int
ns_name_uncompress(const u_char *msg, const u_char *eom, const u_char *src,
char *dst, size_t dstsiz)
{
u_char tmp[NS_MAXCDNAME];
int n;
if ((n = ns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
return (-1);
if (ns_name_ntop(tmp, dst, dstsiz) == -1)
return (-1);
return (n);
}
Code:
int
ns_name_ntop(const u_char *src, char *dst, size_t dstsiz)
{
const u_char *cp;
char *dn, *eom;
u_char c;
u_int n;
int l;
cp = src;
dn = dst;
eom = dst + dstsiz;
while ((n = *cp++) != 0) {
if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
/* Some kind of compression pointer. */
__set_errno (EMSGSIZE);
return (-1);
}
if (dn != dst) {
if (dn >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
*dn++ = '.';
}
if ((l = labellen(cp - 1)) < 0) {
__set_errno (EMSGSIZE);
return(-1);
}
if (dn + l >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
if ((n & NS_CMPRSFLGS) == NS_TYPE_ELT) {
int m;
if (n != DNS_LABELTYPE_BITSTRING) {
/* XXX: labellen should reject this case */
__set_errno (EINVAL);
return(-1);
}
if ((m = decode_bitstring(&cp, dn, eom)) < 0)
{
__set_errno (EMSGSIZE);
return(-1);
}
dn += m;
continue;
}
for ((void)NULL; l > 0; l--) {
c = *cp++;
if (special(c)) {
if (dn + 1 >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
*dn++ = '\\';
*dn++ = (char)c;
} else if (!printable(c)) {
if (dn + 3 >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
*dn++ = '\\';
*dn++ = digits[c / 100];
*dn++ = digits[(c % 100) / 10];
*dn++ = digits[c % 10];
} else {
if (dn >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
*dn++ = (char)c;
}
}
}
if (dn == dst) {
if (dn >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
*dn++ = '.';
}
if (dn >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
*dn++ = '\0';
return (dn - dst);
}
Code:
int
ns_name_unpack(const u_char *msg, const u_char *eom, const u_char *src,
u_char *dst, size_t dstsiz)
{
const u_char *srcp, *dstlim;
u_char *dstp;
int n, len, checked, l;
len = -1;
checked = 0;
dstp = dst;
srcp = src;
dstlim = dst + dstsiz;
if (srcp < msg || srcp >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
/* Fetch next label in domain name. */
while ((n = *srcp++) != 0) {
/* Check for indirection. */
switch (n & NS_CMPRSFLGS) {
case 0:
case NS_TYPE_ELT:
/* Limit checks. */
if ((l = labellen(srcp - 1)) < 0) {
__set_errno (EMSGSIZE);
return(-1);
}
if (dstp + l + 1 >= dstlim || srcp + l >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
checked += l + 1;
*dstp++ = n;
memcpy(dstp, srcp, l);
dstp += l;
srcp += l;
break;
case NS_CMPRSFLGS:
if (srcp >= eom) {
__set_errno (EMSGSIZE);
return (-1);
}
if (len < 0)
len = srcp - src + 1;
srcp = msg + (((n & 0x3f) << 8) | (*srcp & 0xff));
if (srcp < msg || srcp >= eom) { /*%< Out of range. */
__set_errno (EMSGSIZE);
return (-1);
}
checked += 2;
/*
* Check for loops in the compressed name;
* if we've looked at the whole message,
* there must be a loop.
*/
if (checked >= eom - msg) {
__set_errno (EMSGSIZE);
return (-1);
}
break;
default:
__set_errno (EMSGSIZE);
return (-1); /*%< flag error */
}
}
*dstp = '\0';
if (len < 0)
len = srcp - src;
return (len);
}
The code snippets above have a lot of
Code:
__set_errno (EMSGSIZE)
and putting a unique print statement just before each of them is trivial.
About my response - do you realize you are plain lazy and want others to do your job ? |
