On Wed, Oct 26, 2016 at 08:52:56PM -0700, Stephen Hemminger wrote:
> On Wed, 26 Oct 2016 22:30:07 +0300
> Cyrill Gorcunov <gorcu...@gmail.com> wrote:
>
> >
> > if (h->nlmsg_type == NLMSG_DONE) {
> > + int len;
> > +
> > + /*
> > + * The kernel reports if there is
> > + * no inet-diag module present in
> > + * the system via negative length
> > + * as error code.
> > + */
> > + if (h->nlmsg_len <
> > NLMSG_LENGTH(sizeof(int))) {
> > + fprintf(stderr, "Truncated
> > length reply\n");
> > + return -1;
> > + }
> > + len = *(int *)NLMSG_DATA(h);
> > + if (len < 0) {
> > + errno = -len;
> > + if (errno == ENOENT ||
> > + errno == EOPNOTSUPP)
> > + return -1;
> > + perror("RTNETLINK answers");
> > + return len;
> > + }
> > found_done = 1;
> > break; /* process next filter */
> >
>
> This looks like a mistake in how you implemented the functionality in the
> kernel.
> Despite what it looks like, all netlink request/reply functionality reports
> errors in current implementation by returning error to the sendmsg request.
>
> What you added implies that the new kernel api is wrong, or many other usages
> are wrong. Please fix the kernel.
No. This is not my code. This code has been in kernel for the really long time.
I don't know why you've not been doing such test in libnetlink before.
Actually I've hit this problem accidentaly -- I made a patch 2 from this
set and run it on the machine where kernel was unpatched, ie without
raw-diag module, and I found that we can't figure out if kernel notified
us that some diag module simply not present in the system. And here is
the only way to find it out.
