Re: KPI, mbuf, strange mbuf and mbuf_len strange definition
Re: KPI, mbuf, strange mbuf and mbuf_len strange definition
- Subject: Re: KPI, mbuf, strange mbuf and mbuf_len strange definition
- From: Josh Graessley <email@hidden>
- Date: Thu, 8 Dec 2005 11:38:20 -0800
The mismatch could lead to problems, however, an mbuf length of less
than zero is invalid. The length is an absolute length. It makes no
sense for it to be less than 0. The internal implementation hasn't
switched over to an unsigned type yet. It is conceivable that there
are bugs with the conversion between the two. In the long run, the
length should be unsigned so the KPI is correct.
-josh
On Dec 8, 2005, at 11:25 AM, Stephane Sudre wrote:
Could there be a problem with the declaration of mbuf_len?
size_t mbuf_len(mbuf_t mbuf);
size_t is said to be a __darwin_size_t
__darwin_size_t is said to be __SIZE_TYPE__
__SIZE_TYPE__ is said to be long unsigned int (from what I've found
with google).
My problem is that the m_hdr struct is stating (in the xnu source
code):
struct m_hdr {
struct mbuf *mh_next; /* next buffer in chain */
struct mbuf *mh_nextpkt; /* next chain in queue/record */
long mh_len; /* amount of data in this mbuf */
so mh_len is signed if I'm not mistaken.
This is a bit "funny" when you're trying to deal with this kind of
weird mbuf chain :
p *((struct mbuf *) 0x3d1fd100)
$3 = {
m_hdr = {
mh_next = 0x3d221700,
mh_nextpkt = 0x0,
mh_len = 0,
mh_data = 0x3d1fd13b "@\002\001?\b>\006l!E",
mh_type = 0,
mh_flags = 0
},
....
p *((struct mbuf *) 0x3d221700)
$5 = {
m_hdr = {
mh_next = 0x3d221600,
mh_nextpkt = 0xfffffff7,
mh_len = -1,
mh_data = 0xffffffff <Address 0xffffffff out of bounds>,
mh_type = 0,
mh_flags = -1
},
and you're testing if (mbuf_len( ) < 0) ...
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