[PATCH v2 3/7] tests: check decoding of netlink protocol

[Dmitry V. Levin]

On Wed, Jun 15, 2016 at 09:23:11AM +0000, Fabien Siron wrote:
> Quoting Dmitry V. Levin (2016-06-14 12:03:47)
> > On Mon, Jun 13, 2016 at 02:37:23PM +0000, Fabien Siron wrote:
> > [...]
> > > +static void
> > > +send_query(const int fd)
> > > +{
> > > +     struct {
> > > +             struct nlmsghdr nlh;
> > > +             char magic[4];
> > > +     } req = {
> > > +             .nlh = {
> > > +                     .nlmsg_len = sizeof(req),
> > > +                     .nlmsg_type = SOCK_DIAG_BY_FAMILY,
> > > +                     .nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST
> > > +             },
> > > +             .magic = "abcd"
> > > +     };
> > > +
> > > +     if (sendto(fd, &req, sizeof(req), MSG_DONTWAIT, NULL, 0) <= 0)
> > > +             perror_msg_and_skip("sendto");
> > 
> > Why <= 0?  The next statement assumes == (unsigned) sizeof(req).
> 
> Indeed.
> 
> > 
> > > +
> > > +     printf("sendto(%d, {{len=%u, type=20, flags=NLM_F_REQUEST|0x300, "
> > > +            "seq=0, pid=0}, \"abcd\"}, 20, MSG_DONTWAIT, NULL, 0) = %u\n",
> > > +            fd, (unsigned) sizeof(req), (unsigned) sizeof(req));
> > 
> > Please do not encode values of constants into output strings verbatim.
> 
> Well, the size of the magic must be aligned on 4 characters to avoid '\0' stuff.

I don't see any issues with initialization of req.magic.
Potentially problematic strings are "20" and "0x300".


-- 
ldv
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