problems encountered when read vsftpd code

thinke365 · 06-08-2010, 02:35 PM

the version of vsftpd i read is 1.2.1， i find the following code in main.c:

struct vsf_sysutil_statbuf* p_statbuf = 0;

but i cannot find the definition of this structure.
then anybody here can tell me what is the definition of vsf_sysutil_statbuf struct?
thank you

paulsm4 · 06-08-2010, 04:12 PM

It's part of the vsftpd source.

Either you didn't get the complete source package, or you're not looking in the right place:

1. Search for all the #include files in your .c program

2. Search for all of the corresponding .h files in your source tree and/or filesystem.

3. Failing all else, download a different copy of the vsftpd source package.

thinke365 · 06-08-2010, 04:18 PM

i find its forward declaration now, in sysstr.h,
but there is no concrete definiton for this structure, i am confused about this ...

struct vsf_sysutil_statbuf;

paulsm4 · 06-08-2010, 11:12 PM

So you marked the post "not helpful" just because YOU can't find the definition?

I'm confused about THAT

Good luck .. PSM

thinke365 · 06-09-2010, 12:25 AM

Quote:

Originally Posted by paulsm4

So you marked the post "not helpful" just because YOU can't find the definition?

I'm confused about THAT

Good luck .. PSM

since i have tried that before you told me, so that is not so helpful, i am sorry if you mind that, this is the first time i use recommand function this forum provides

i have tried google codesearch, still not find that definition, maybe this is an confusing "forward definition" trick, i don't know, why there is no concrete definition?

paulsm4 · 06-09-2010, 10:50 AM

Hi -

1. I downloaded and examined the VSFTP source:

Code:

wget ftp://vsftpd.beasts.org/users/cevans/vsftpd-2.3.0pre2.tar.gz

tar xvzf vsftpd-2.3.0pre2.tar.gz

cd vs*pre2

grep vsf_sysutil_statbuf *|less =>
  sysutil.h
  sysutil.c
  <= these are the VSFTP modules that "define" vsf_sysutil_statbuf

2. I found exactly the same "definition" as you've been seeing:

Code:

less sysutil.h =>
struct vsf_sysutil_statbuf;
  <= Nothing but a forward definition...

3. So I looked at how it's being used:

Code:

less sysutil.c =>
int
vsf_sysutil_stat(const char* p_name, struct vsf_sysutil_statbuf** p_ptr)
{
  vsf_sysutil_alloc_statbuf(p_ptr);
  return stat(p_name, (struct stat*) (*p_ptr));
}
...
static void
vsf_sysutil_alloc_statbuf(struct vsf_sysutil_statbuf** p_ptr)
{
  if (*p_ptr == NULL)
  {
    *p_ptr = vsf_sysutil_malloc(sizeof(struct stat));
  }
}
...

Soooooooo.......

1. vsf_sysutil_statbuf is nothing more than a wrapper around the OS's "stat" struct.

2. vsf_sysutil_alloc_statbuf() only allocates memory once (and re-uses the memory if it's already been allocated)

3. The whole scheme "insulates" the rest of the VSFTP code from "stat" being different on different OS's. All of the "details" are encapsulated entirely within sysutil.c

'Hope that helps.. PSM