[PATCH] tests: check decoding of NETLINK_SOCK_DIAG AF_UNIX messages

[Dmitry V. Levin]

On Tue, Jun 13, 2017 at 07:10:13PM +0300, Dmitry V. Levin wrote:
> On Tue, Jun 13, 2017 at 07:04:21PM +0800, JingPiao Chen wrote:
> > +static void
> > +test_unix_diag_req(const int fd)
> > +{
> > ...
> > + /* short read of unix_diag_req */
> > + nlh = nlh0 - (sizeof(*req) - 1);
> > + memmove(nlh, nlh0 - sizeof(*req), NLMSG_HDRLEN + sizeof(*req) - 1);
> > +
> > + rc = sendto(fd, nlh, NLMSG_HDRLEN + sizeof(*req), MSG_DONTWAIT,
> > +    NULL, 0);
> > +
> > + printf("sendto(%d, {{len=%u, type=SOCK_DIAG_BY_FAMILY"
> > +       ", flags=NLM_F_REQUEST, seq=0, pid=0}, {family=AF_UNIX, %p}}"
> > +       ", %u, MSG_DONTWAIT, NULL, 0) = %s\n",
> > +       fd, NLMSG_HDRLEN + (unsigned int) sizeof(*req),
> > +       NLMSG_DATA(nlh) + 1,
> > +       NLMSG_HDRLEN + (unsigned int) sizeof(*req),
> > +       sprintrc(rc));
> > +}
> > 
> > When (sizeof(*req) - 1 - sizeof(*family) > DEFAULT_STRLEN), the test will
> > fail.
> 
> Why?  In this part of the test strace is expected to print a pointer,
> not a string, so it shouldn't be affected by DEFAULT_STRLEN.
> 
> > I replace sizeof(*req) - 1 with sizeof(*family).
> > 
> > nlh = nlh0 - sizeof(*family);
> > memmove(nlh, nlh0 - sizeof(*req), NLMSG_HDRLEN + sizeof(*family));

My idea is to specify a memory area that is exactly 1 byte less than
necessary, this way we can test corner cases better.


-- 
ldv
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