[PATCH v4 4/4] tests: add check for decoding of netfilter subsystem

[Dmitry V. Levin]

On Sun, Mar 11, 2018 at 03:06:23AM +0300, Dmitry V. Levin wrote:
> On Thu, Mar 08, 2018 at 10:53:47PM +0800, Chen Jingpiao wrote:
> > * tests/netlink_netfilter.c(test_nfgenmsg): Add check for decoding
> > of netfilter subsystem.
> > ---
> >  tests/netlink_netfilter.c | 34 ++++++++++++++++++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> > 
> > diff --git a/tests/netlink_netfilter.c b/tests/netlink_netfilter.c
> > index 2826017d1..149da5ac1 100644
> > --- a/tests/netlink_netfilter.c
> > +++ b/tests/netlink_netfilter.c
> > @@ -149,9 +149,22 @@ test_nfgenmsg(const int fd)
> >  		     printf("{nfgen_family=AF_UNIX");
> >  		     printf(", version=NFNETLINK_V0");
> >  		     printf(", res_id=htons(%d)", NFNL_SUBSYS_NFTABLES));
> > +# endif /* NFNL_MSG_BATCH_BEGIN */
> >  
> >  	char str_buf[NLMSG_ALIGN(sizeof(msg)) + 4];
> > +	msg.res_id = htons(0xefab);
> > +	memcpy(str_buf, &msg, sizeof(msg));
> > +	memcpy(str_buf + NLMSG_ALIGN(sizeof(msg)), "1234", 4);
> > +	TEST_NETLINK_(fd, nlh0,
> > +		      0xffff, "0xff /* NFNL_SUBSYS_??? */<<8|0xff",
> > +		      NLM_F_REQUEST, "NLM_F_REQUEST",
> > +		      sizeof(str_buf), str_buf, sizeof(str_buf),
> > +		      printf("{nfgen_family=AF_UNIX");
> > +		      printf(", version=NFNETLINK_V0");
> > +		      printf(", res_id=htons(%d)"
> > +			     ", \"\\x31\\x32\\x33\\x34\"", 0xefab));
> >  
> > +# ifdef NFNL_MSG_BATCH_BEGIN
> >  	msg.res_id = htons(0xabcd);
> >  	memcpy(str_buf, &msg, sizeof(msg));
> >  	memcpy(str_buf + NLMSG_ALIGN(sizeof(msg)), "1234", 4);
> > @@ -164,6 +177,27 @@ test_nfgenmsg(const int fd)
> >  		     printf(", res_id=htons(%d)"
> >  			    ", \"\\x31\\x32\\x33\\x34\"", 0xabcd));
> >  # endif /* NFNL_MSG_BATCH_BEGIN */
> > +
> > +	static const struct nlattr nla = {
> > +		.nla_len = sizeof(nla),
> > +		.nla_type = 0x0bcd
> > +	};
> > +	char nla_buf[NLMSG_ALIGN(sizeof(msg)) + sizeof(nla)];
> > +
> > +	msg.res_id = htons(NFNL_SUBSYS_NFTABLES);
> > +	memcpy(nla_buf, &msg, sizeof(msg));
> > +	memcpy(nla_buf + NLMSG_ALIGN(sizeof(msg)), &nla, sizeof(nla));
> > +
> > +	TEST_NETLINK_(fd, nlh0,
> > +		      NFNL_SUBSYS_NFTABLES << 8 | 0xff,
> > +		      "NFNL_SUBSYS_NFTABLES<<8|0xff /* NFT_MSG_??? */",
> > +		      NLM_F_REQUEST, "NLM_F_REQUEST",
> > +		      sizeof(nla_buf), nla_buf, sizeof(nla_buf),
> > +		      printf("{nfgen_family=AF_UNIX");
> > +		      printf(", version=NFNETLINK_V0");
> > +		      printf(", res_id=htons(NFNL_SUBSYS_NFTABLES)"
> > +			     ", {nla_len=%d, nla_type=%#x}",
> > +			     nla.nla_len, nla.nla_type));
> 
> The last part of this test fails on one of systems where
> I test changes before merging them into master:
> 
> -sendto(3, {{len=24, type=NFNL_SUBSYS_NFTABLES<<8|0xff /* NFT_MSG_??? */, flags=NLM_F_REQUEST, seq=0, pid=0}, {nfgen_family=AF_UNIX, version=NFNETLINK_V0, res_id=htons(NFNL_SUBSYS_NFTABLES), {nla_len=4, nla_type=0xbcd}}, 24, MSG_DONTWAIT, NULL, 0) = 24
> +sendto(3, {{len=24, type=NFNL_SUBSYS_NFTABLES<<8|0xff /* NFT_MSG_??? */, flags=NLM_F_REQUEST, seq=0, pid=0}, {nfgen_family=AF_UNIX, version=NFNETLINK_V0, res_id=htons(NFNL_SUBSYS_NFTABLES), "\x04\x00\xcd\x0b"}, 24, MSG_DONTWAIT, NULL, 0) = 24
> 
> Looks like an alignment issue, but I haven't had a chance to look into this yet.

No, the reason is completely different: the kernel headers installed on
that system are old enough to have NFNL_SUBSYS_COUNT defined to older
value than our fallback definition of NFNL_SUBSYS_NFTABLES provided by
xlat/nl_netfilter_subsys_ids.in file.

In other words, NFNL_SUBSYS_COUNT provided by kernel headers is unreliable
and shouldn't be used, I think it has to be removed from
xlat/nl_netfilter_subsys_ids.in as well.

For netlink_netfilter.c purposes I'd recommend to use something like
(subsys_id > nl_netfilter_subsys_ids[ARRAY_SIZE(nl_netfilter_subsys_ids) - 1].val)
instead of subsys_id >= NFNL_SUBSYS_COUNT).


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