This patch adds a bpf self-test to cover BPF_LWT_ENCAP_IP mode
in bpf_lwt_push_encap.
Covered:
- encapping in LWT_IN and LWT_XMIT
- IPv4 and IPv6
A follow-up patch will add GSO and VRF-enabled tests.
Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Sub-register mode compilation was enabled only when there are eBPF "v3"
processor supports at both compilation time inside LLVM and runtime inside
kernel.
Given separation betwen build and test server could be often, this patch
removes the runtime support criteria.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
At the moment, all kernel bpf objects are listed under BPF_OBJ_FILES.
Listing them manually sometimes causing patch conflict when people are
adding new testcases simultaneously.
It is better to centre all the related source files under a subdir
"progs", then auto-generate the object file list.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
At the moment, we only do extra sub-register mode compilation on bpf object
files used by "test_progs". These object files are really loaded and
executed.
This patch further extends sub-register mode compilation to all bpf object
files, even those without corresponding runtime tests. Because this could
help testing LLVM sub-register code-gen, kernel bpf selftest has much more
C testcases with reasonable size and complexity compared with LLVM
testsuite which only contains unit tests.
There were some file duplication inside BPF_OBJ_FILES_DUAL_COMPILE which
is removed now.
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
"alu32" is a build dir and contains various files for BPF sub-register
code-gen testing.
This patch tells git to ignore it.
Suggested-by: Yonghong Song <yhs@fb.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This patch adds a C program to show the usage on
skb->sk and bpf_tcp_sock.
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This patch tests accessing the skb->sk and the new helpers,
bpf_sk_fullsock and bpf_tcp_sock.
The errstr of some existing "reference tracking" tests is changed
with s/bpf_sock/sock/ and s/socket/sock/ where "sock" is from the
verifier's reg_type_str[].
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Now that we have btf__get_raw_data() it's trivial for tests to iterate
over all strings for testing purposes, which eliminates the need for
btf__get_strings() API.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The kernel verifier has three levels of logs:
0: no logs
1: logs mostly useful
> 1: verbose
Current libbpf API functions bpf_load_program_xattr() and
bpf_load_program() cannot specify log_level.
The bcc, however, provides an interface for user to
specify log_level 2 for verbose output.
This patch added log_level into structure
bpf_load_program_attr, so users, including bcc, can use
bpf_load_program_xattr() to change log_level. The
supported log_level is 0, 1, and 2.
The bpf selftest test_sock.c is modified to enable log_level = 2.
If the "verbose" in test_sock.c is changed to true,
the test will output logs like below:
$ ./test_sock
func#0 @0
0: R1=ctx(id=0,off=0,imm=0) R10=fp0,call_-1
0: (bf) r6 = r1
1: R1=ctx(id=0,off=0,imm=0) R6_w=ctx(id=0,off=0,imm=0) R10=fp0,call_-1
1: (61) r7 = *(u32 *)(r6 +28)
invalid bpf_context access off=28 size=4
Test case: bind4 load with invalid access: src_ip6 .. [PASS]
...
Test case: bind6 allow all .. [PASS]
Summary: 16 PASSED, 0 FAILED
Some test_sock tests are negative tests and verbose verifier
log will be printed out as shown in the above.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Daniel Borkmann says:
====================
pull-request: bpf-next 2019-02-07
The following pull-request contains BPF updates for your *net-next* tree.
The main changes are:
1) Add a riscv64 JIT for BPF, from Björn.
2) Implement BTF deduplication algorithm for libbpf which takes BTF type
information containing duplicate per-compilation unit information and
reduces it to an equivalent set of BTF types with no duplication and
without loss of information, from Andrii.
3) Offloaded and native BPF XDP programs can coexist today, enable also
offloaded and generic ones as well, from Jakub.
4) Expose various BTF related helper functions in libbpf as API which
are in particular helpful for JITed programs, from Yonghong.
5) Fix the recently added JMP32 code emission in s390x JIT, from Heiko.
6) Fix BPF kselftests' tcp_{server,client}.py to be able to run inside
a network namespace, also add a fix for libbpf to get libbpf_print()
working, from Stanislav.
7) Fixes for bpftool documentation, from Prashant.
8) Type cleanup in BPF kselftests' test_maps.c to silence a gcc8 warning,
from Breno.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Use a simple topology consisting of two hosts directly connected to a
router. Make sure IPv4/IPv6 ping works and then add blackhole routes.
Test that ping fails and that the routes are marked as offloaded. Use a
simple tc filter to test that packets were dropped by the ASIC and not
trapped to the CPU.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When compiling test_maps selftest with GCC-8, it warns that an array
might be indexed with a negative value, which could cause a negative
out of bound access, depending on parameters of the function. This
is the GCC-8 warning:
gcc -Wall -O2 -I../../../include/uapi -I../../../lib -I../../../lib/bpf -I../../../../include/generated -DHAVE_GENHDR -I../../../include test_maps.c /home/breno/Devel/linux/tools/testing/selftests/bpf/libbpf.a -lcap -lelf -lrt -lpthread -o /home/breno/Devel/linux/tools/testing/selftests/bpf/test_maps
In file included from test_maps.c:16:
test_maps.c: In function ‘run_all_tests’:
test_maps.c:1079:10: warning: array subscript -1 is below array bounds of ‘pid_t[<Ube20> + 1]’ [-Warray-bounds]
assert(waitpid(pid[i], &status, 0) == pid[i]);
^~~~~~~~~~~~~~~~~~~~~~~~~~~
test_maps.c:1059:6: warning: array subscript -1 is below array bounds of ‘pid_t[<Ube20> + 1]’ [-Warray-bounds]
pid[i] = fork();
~~~^~~
This patch simply guarantees that the task(s) variables are unsigned,
thus, they could never be a negative number (which they are not in
current code anyway), hence avoiding an out of bound access warning.
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Test adding the offloaded program after the other program
is already installed.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Add simple sanity check for enabling generic and offload
XDP, simply reuse the native and offload checks.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Figuring out which exact check in test_offload.py takes more
time than it should. Print the traceback (to the screen and
the logs).
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Recent changes added extack to program replacement path,
expect extack instead of generic messages.
Fixes: 01dde20ce0 ("xdp: Provide extack messages when prog attachment failed")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Commit 9c65112744 ("selftests/btf: add initial BTF dedup tests")
added dedup tests in test_btf.c.
It broke the raw test:
BTF raw test[71] (func proto (Bad arg name_off)):
btf_raw_create:2905:FAIL Error getting string #65535, strs_cnt:1
The test itself encodes invalid func_proto parameter name
offset 0xffffFFFF as a negative test for the kernel.
The above commit changed the meaning of that offset and
resulted in a user space error.
#define NAME_NTH(N) (0xffff0000 | N)
#define IS_NAME_NTH(X) ((X & 0xffff0000) == 0xffff0000)
#define GET_NAME_NTH_IDX(X) (X & 0x0000ffff)
Currently, the kernel permits maximum name offset 0xffff.
Set the test name off as 0x0fffFFFF to trigger the kernel
verification failure.
Cc: Andrii Nakryiko <andriin@fb.com>
Fixes: 9c65112744 ("selftests/btf: add initial BTF dedup tests")
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
RISC-V does, in-general, not have "efficient unaligned access". When
testing the RISC-V BPF JIT, some selftests failed in the verification
due to misaligned access. Annotate these tests with the
F_NEEDS_EFFICIENT_UNALIGNED_ACCESS flag.
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This patch sets up a new kind of tests (BTF dedup tests) and tests few aspects of
BTF dedup algorithm. More complete set of tests will come in follow up patches.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
With the recent print rework we now have the following problem:
pr_{warning,info,debug} expand to __pr which calls libbpf_print.
libbpf_print does va_start and calls __libbpf_pr with va_list argument.
In __base_pr we again do va_start. Because the next argument is a
va_list, we don't get correct pointer to the argument (and print noting
in my case, I don't know why it doesn't crash tbh).
Fix this by changing libbpf_print_fn_t signature to accept va_list and
remove unneeded calls to va_start in the existing users.
Alternatively, this can we solved by exporting __libbpf_pr and
changing __pr macro to (and killing libbpf_print):
{
if (__libbpf_pr)
__libbpf_pr(level, "libbpf: " fmt, ##__VA_ARGS__)
}
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Bind and connect to localhost. There is no reason for this test to
use non-localhost interface. This lets us run this test in a network
namespace.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Currently, the libbpf API function libbpf_set_print()
takes three function pointer parameters for warning, info
and debug printout respectively.
This patch changes the API to have just one function pointer
parameter and the function pointer has one additional
parameter "debugging level". So if in the future, if
the debug level is increased, the function signature
won't change.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Compiling rxtimestamp.c generates error messages due to
non-existing declaration for write() library call.
Add missing unistd.h include to provide the declaration and
silence the error.
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Alexei Starovoitov says:
====================
pull-request: bpf-next 2019-02-01
The following pull-request contains BPF updates for your *net-next* tree.
The main changes are:
1) introduce bpf_spin_lock, from Alexei.
2) convert xdp samples to libbpf, from Maciej.
3) skip verifier tests for unsupported program/map types, from Stanislav.
4) powerpc64 JIT support for BTF line info, from Sandipan.
5) assorted fixed, from Valdis, Jesper, Jiong.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
'make clean' is supposed to remove generated files.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The global variable RET needs to be initialized before each call to
log_test. This test case sets it once before running the tests, but then
calls log_tests for every individual test. Thus a failure in one of the
tests causes spurious failures in follow-up tests as well.
Fix by moving the initialization of RET from test_all() to
full_test_span_gre_dir_acl(), a function that implements the test.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This test sets up mirroring such that it mirrors all overlay traffic.
That includes ARP, which causes occasional miscounts and spurious
failures. Ignore ARP explicitly to avoid these problems.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This test relies on routing in the primary traffic path, but neglects to
enable forwarding. Do so.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
After one LAG slave is downed and another upped, it takes a while for
the neighbor on a bridge to time out and get renegotiated. The test does
prompt update of FDB entries by arpinging. But because the neighbor
still references another address, offloading is not possible, and some
packets may end up not being mirrored.
To force the neighbor renegotiation, simply flush the neighbor table at
the bridge.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
ARP or ND traffic can cause spurious migration of FDB back to $swp3.
Mirroring is then updated in accordance with the change, and mirrored
packets are seen at h3, causing a failure.
Detect the case of this spurious roaming, and retry the test.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The untagged egress test sets up mirroring to {,ip6}gretap such that the
underlay goes through a bridge. Then VLAN flags are manipulated to test
that the traffic leaves the bridge 802.1q-tagged or not, as appropriate.
However, when a neighbor expires at the time that the bridge VLAN is
configured as PVID and egress untagged, the following discovery process
can't finish, because the IP address on H3 is still at the VLAN-tagged
netdevice. This manifests by occasional failures where only several of
the 10 required packets get through.
Therefore, when reconfiguring the VLAN flags, move the IP address to the
appropriate device in the H3 VRF.
In addition to that, take this opportunity to embed an ASCII art diagram
to make the topology move obvious.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When running in an environment with poor performance (such as a
simulator), processing mirrored packets can take a while. Evaluating the
condition too soon leads to spurious "seen 9, expected 10" failures as
the last packet doesn't have enough time to get mirrored and the mirror
to arrive and bump the observed counters.
Wait for one ping interval before evaluating the test.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When running in a simulator, the TTL change takes a while to settle and
during this time the performance of the packet processing is lowered.
The resulting instability leads to ping sending more packets as it
assumes some have been dropped. This then leads to regular spurious
failures as more packets than expected are observed.
Sleep a bit to give the system time to stabilize.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The current ping intervals are too short for running mirroring tests in
simulator. This leads to ping sending a follow-up ping before the reply
arrives, thus sending more than the requested 10 ICMP requests. This
traffic is seen at the counters, and causes spurious failures.
Bump interval and timeout numbers 5x in mirroring tests to address the
spurious failures.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The current ping intervals are too short for running mirroring tests in
simulator. This leads to ping sending a follow-up ping before the reply
arrives, thus sending more than the requested 10 ICMP requests. Those
are mirrored, and over a certain threshold the test case run is
considered a failure, because too much traffic is observed.
Bump interval and timeout numbers 5x in mirroring tests to address the
spurious failures.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The current timeout (2 seconds) proved to be too low for some (emulated)
systems where we run the tests.
Make the timeout configurable and default to 5 seconds.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Change most tests to TLS 1.3, while adding tests for previous TLS 1.2
behavior.
Signed-off-by: Dave Watson <davejwatson@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Wire up support for 256 bit keys from the setsockopt to the crypto
framework
Signed-off-by: Dave Watson <davejwatson@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add C based test that runs 4 bpf programs in parallel
that update the same hash and array maps.
And another 2 threads that read from these two maps
via lookup(key, value, BPF_F_LOCK) api
to make sure the user space sees consistent value in both
hash and array elements while user space races with kernel bpf progs.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
add bpf_spin_lock C based test that requires latest llvm with BTF support
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
add bpf_spin_lock tests to test_verifier.c that don't require
latest llvm with BTF support
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
We don't have this helper if the kernel was compiled without
CONFIG_BPF_EVENTS. Setting prog_type to BPF_PROG_TYPE_TRACEPOINT
let's verifier correctly skip this test based on the missing
prog_type support in the kernel.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Use recently introduced bpf_probe_map_type() to skip tests in the
test_verifier if map creation (create_map) fails. It's handled
explicitly for each fixup, i.e. if bpf_create_map returns negative fd,
we probe the kernel for the appropriate map support and skip the
test is map type is not supported.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Use recently introduced bpf_probe_prog_type() to skip tests in the
test_verifier() if bpf_verify_program() fails. The skipped test is
indicated in the output.
Example:
...
679/p bpf_get_stack return R0 within range SKIP (unsupported program
type 5)
680/p ld_abs: invalid op 1 OK
...
Summary: 863 PASSED, 165 SKIPPED, 3 FAILED
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Use recently introduced bpf_probe_map_type() to skip test_sockmap()
if map creation fails. The skipped test is indicated in the output.
Example:
test_sockmap SKIP (unsupported map type BPF_MAP_TYPE_SOCKMAP)
Fork 1024 tasks to 'test_update_delete'
...
test_sockmap SKIP (unsupported map type BPF_MAP_TYPE_SOCKMAP)
Fork 1024 tasks to 'test_update_delete'
...
test_maps: OK, 2 SKIPPED
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Ensure that the bug is fixed and we no longer have C-TCAM spill for two
keys that differ only in delta.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
With recent fix in C-TCAM spillage for delta masks, the test stops to be
falsely positive. So fix it not to use delta by adding src_ip bits to the
masks. Alongside with that, use C-TCAM spill trace to see when the
spillage actually happens.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Allow to specify number of trace hits and move helpers
to the beginning of the file.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull networking fixes from David Miller:
1) Need to save away the IV across tls async operations, from Dave
Watson.
2) Upon successful packet processing, we should liberate the SKB with
dev_consume_skb{_irq}(). From Yang Wei.
3) Only apply RX hang workaround on effected macb chips, from Harini
Katakam.
4) Dummy netdev need a proper namespace assigned to them, from Josh
Elsasser.
5) Some paths of nft_compat run lockless now, and thus we need to use a
proper refcnt_t. From Florian Westphal.
6) Avoid deadlock in mlx5 by doing IRQ locking, from Moni Shoua.
7) netrom does not refcount sockets properly wrt. timers, fix that by
using the sock timer API. From Cong Wang.
8) Fix locking of inexact inserts of xfrm policies, from Florian
Westphal.
9) Missing xfrm hash generation bump, also from Florian.
10) Missing of_node_put() in hns driver, from Yonglong Liu.
11) Fix DN_IFREQ_SIZE, from Johannes Berg.
12) ip6mr notifier is invoked during traversal of wrong table, from Nir
Dotan.
13) TX promisc settings not performed correctly in qed, from Manish
Chopra.
14) Fix OOB access in vhost, from Jason Wang.
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (52 commits)
MAINTAINERS: Add entry for XDP (eXpress Data Path)
net: set default network namespace in init_dummy_netdev()
net: b44: replace dev_kfree_skb_xxx by dev_consume_skb_xxx for drop profiles
net: caif: call dev_consume_skb_any when skb xmit done
net: 8139cp: replace dev_kfree_skb_irq by dev_consume_skb_irq for drop profiles
net: macb: Apply RXUBR workaround only to versions with errata
net: ti: replace dev_kfree_skb_irq by dev_consume_skb_irq for drop profiles
net: apple: replace dev_kfree_skb_irq by dev_consume_skb_irq for drop profiles
net: amd8111e: replace dev_kfree_skb_irq by dev_consume_skb_irq
net: alteon: replace dev_kfree_skb_irq by dev_consume_skb_irq
net: tls: Fix deadlock in free_resources tx
net: tls: Save iv in tls_rec for async crypto requests
vhost: fix OOB in get_rx_bufs()
qed: Fix stack out of bounds bug
qed: Fix system crash in ll2 xmit
qed: Fix VF probe failure while FLR
qed: Fix LACP pdu drops for VFs
qed: Fix bug in tx promiscuous mode settings
net: i825xx: replace dev_kfree_skb_irq by dev_consume_skb_irq for drop profiles
netfilter: ipt_CLUSTERIP: fix warning unused variable cn
...
