DragonFly submit List (threaded) for 2003-11
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Re: kern.file weirdness
Hello.
On Sat, Nov 22, 2003 at 11:53:30AM +0100, Eirik Nygaard wrote:
> I am working on removing perlism in userland and have come over a little
> problem when I am rewriting sockstat. I try to get all the open fd's from
> the kern.file sysctl with this code:
> void
> get_files(void)
> {
> size_t size;
>
> if (sysctlbyname("kern.file", NULL, &size, NULL, 0) < 0)
> err(1, "sysctlbyname()");
> if ((files = malloc(size)) == NULL)
> err(1, "malloc()");
> if (sysctlbyname("kern.file", files, &size, NULL, 0) < 0)
> err(1, "sysctlbyname()");
>
> nfiles = size / sizeof(struct file);
> {
> int i;
> for(i = 0; i < nfiles; i++)
> printf("Type: %d\n", files[i].f_type);
> }
>
> }
>
> but it only gives me bogus results for some reason.
>
> Output:
> Type: -16333
> Type: -14424
> [...]
> Type: -14424
>
> Would be grateful if someone knows what I am doing wrong here.
FreeBSD-current's version of sockstat has a block of code
which looks like this:
static void
getfiles(void)
{
size_t len;
if ((xfiles = malloc(len = sizeof *xfiles)) == NULL)
err(1, "malloc()");
while (sysctlbyname("kern.file", xfiles, &len, 0, 0) == -1) {
if (errno != ENOMEM)
err(1, "sysctlbyname()");
len *= 2;
if ((xfiles = realloc(xfiles, len)) == NULL)
err(1, "realloc()");
}
if (len > 0 && xfiles->xf_size != sizeof *xfiles)
errx(1, "struct xfile size mismatch");
nxfiles = len / sizeof *xfiles;
}
i.e., you must resize the buffer until sysctlbyname() fails with
ENOMEM.
Cheers.
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