Re: [PATCH bpf-next] selftests/bpf: Fix undeclared identifier build errors of test_bpf_nf.c

From: Yonghong Song
Date: Tue Jan 17 2023 - 14:30:18 EST

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On 1/17/23 1:52 AM, Tiezhu Yang wrote:

On 01/17/2023 02:48 PM, Yonghong Song wrote:

On 1/16/23 5:54 AM, Alan Maguire wrote:

On 16/01/2023 12:30, Eduard Zingerman wrote:

On Mon, 2023-01-16 at 12:55 +0800, Tiezhu Yang wrote:

$ make -C tools/testing/selftests/bpf/

   CLNG-BPF [test_maps] test_bpf_nf.bpf.o
progs/test_bpf_nf.c:160:42: error: use of undeclared identifier
'NF_NAT_MANIP_SRC'
                 bpf_ct_set_nat_info(ct, &saddr, sport,
NF_NAT_MANIP_SRC);
                                                        ^
progs/test_bpf_nf.c:163:42: error: use of undeclared identifier
'NF_NAT_MANIP_DST'
                 bpf_ct_set_nat_info(ct, &daddr, dport,
NF_NAT_MANIP_DST);
                                                        ^
2 errors generated.

Copy the definitions in include/net/netfilter/nf_nat.h to test_bpf_nf.c
to fix the above build errors.

Fixes: b06b45e82b59 ("selftests/bpf: add tests for
bpf_ct_set_nat_info kfunc")
Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
tools/testing/selftests/bpf/progs/test_bpf_nf.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/test_bpf_nf.c
b/tools/testing/selftests/bpf/progs/test_bpf_nf.c
index 227e85e..114f961 100644
--- a/tools/testing/selftests/bpf/progs/test_bpf_nf.c
+++ b/tools/testing/selftests/bpf/progs/test_bpf_nf.c
@@ -34,6 +34,11 @@ __be16 dport = 0;
int test_exist_lookup = -ENOENT;
u32 test_exist_lookup_mark = 0;
+enum nf_nat_manip_type {
+    NF_NAT_MANIP_SRC,
+    NF_NAT_MANIP_DST
+};
+

This is confusing, when I build the kernel/tests I get the declaration
the "enum nf_nat_manip_type" from the vmlinux.h (which is included
from test_bpf_nf.c).
Which means that this patch results in compilation error with my
configuration.
Is there a chance that your kernel is configured without some
necessary netfilter
configuration options? Have you tried this patch with BPF CI?

Yep; I suspect if CONFIG_NF_NAT=m , the required definitions won't
make it
into vmlinux.h. The reference tools/testing/seftests/bpf/config has
CONFIG_NF_NAT=y so it is at least documented in the referenced config.

I'd suggest going the route of

commit aa67961f3243dfff26c47769f87b4d94b07ec71f
Author: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
Date:   Tue Dec 6 11:35:54 2022 -0800

     selftests/bpf: Allow building bpf tests with
CONFIG_XFRM_INTERFACE=[m|n]
     ...and adding/using local definitons like:

enum nf_nat_manip_type_local {
    NF_NAT_MANIP_SRC_LOCAL,
    NF_NAT_MANIP_DST_LOCAL
};

The above won't support core, and since preserve_access_index attribute
does not support enum for now. We need to use bpf_core_enum_value to
retrieve the proper value through CORE.

could you try the following?

enum nf_nat_manip_type___local {
    NF_NAT_MANIP_SRC___LOCAL,
    NF_NAT_MANIP_DST___LOCAL,
};

This is OK, it is similar with commit 1058b6a78db2 ("selftests/bpf: Do not fail build if CONFIG_NF_CONNTRACK=m/n").

...
bpf_ct_set_nat_info(ct, &saddr, sport, bpf_core_enum_value(enum
nf_nat_manip_type___local, NF_NAT_MANIP_SRC___LOCAL));
...

bpf_ct_set_nat_info(ct, &daddr, dport, bpf_core_enum_value(enum
nf_nat_manip_type___local, NF_NAT_MANIP_DST___LOCAL));

whether it works or not? Could you also try if the
enumerator sequence in enum nf_nat_manip_type___local changed?

...to avoid the name clash.

Alan

I tested this on x86_64 fedora 36, using config-5.17.5-300.fc36.x86_64
to generate .config, CONFIG_NF_CONNTRACK=m, CONFIG_NF_NAT=m, there are
no definitions of NF_NAT_MANIP_SRC and NF_NAT_MANIP_DST in vmlinux.h,
build test_bpf_nf.c failed.

Thanks for trying. Yes, I tried in my environment and it failed because
I didn't change the enum nf_nat_manip_type type for kfunc:
int bpf_ct_set_nat_info(struct nf_conn *, union nf_inet_addr *,
int port, enum nf_nat_manip_type) __ksym;

But when I changed 'enum nf_nat_manip_type' to
'enum nf_nat_manip_type___local', kernel complains kfunc argument
mismatch. The reason most likely is 'enum nf_nat_manip_type___local'
is not converted to 'enum nf_nat_manip_type' by libbpf.

This might be expected as preserve_access_index attribute only
supports record (struct/union) type and libbpf might just do that.
Could you double check whether this is the case or not?

Maybe it is time to implement preserve_access_index support
for enum type in clang now.

But we need to resolve the issue, even temporarily for now.
See below.

$ grep -w CONFIG_NF_CONNTRACK /boot/config-5.17.5-300.fc36.x86_64
CONFIG_NF_CONNTRACK=m
$ grep -w CONFIG_NF_NAT /boot/config-5.17.5-300.fc36.x86_64
CONFIG_NF_NAT=m

I tested with various configs, the definitions of NF_NAT_MANIP_SRC and
NF_NAT_MANIP_DST in vmlinux.h only depend on CONFIG_NF_CONNTRACK=y.

(1) CONFIG_NF_CONNTRACK=m, CONFIG_NF_NAT=m, no definitions
$ grep -w CONFIG_NF_CONNTRACK .config
CONFIG_NF_CONNTRACK=m
$ grep -w CONFIG_NF_NAT .config
CONFIG_NF_NAT=m
$ grep NF_NAT_MANIP_SRC tools/testing/selftests/bpf/tools/include/vmlinux.h
$ grep NF_NAT_MANIP_DST tools/testing/selftests/bpf/tools/include/vmlinux.h
$

(2) CONFIG_NF_CONNTRACK=m, CONFIG_NF_NAT=y, no definitions
This case is unable, because CONFIG_NF_NAT depends on CONFIG_NF_CONNTRACK.

(3) CONFIG_NF_CONNTRACK=m, CONFIG_NF_NAT=n, no definitions
$ grep -w CONFIG_NF_CONNTRACK .config
CONFIG_NF_CONNTRACK=m
$ grep -w CONFIG_NF_NAT .config
# CONFIG_NF_NAT is not set
$ grep NF_NAT_MANIP_SRC tools/testing/selftests/bpf/tools/include/vmlinux.h
$ grep NF_NAT_MANIP_DST tools/testing/selftests/bpf/tools/include/vmlinux.h
$

(4) CONFIG_NF_CONNTRACK=y, CONFIG_NF_NAT=m, have definitions
$ grep -w CONFIG_NF_CONNTRACK .config
CONFIG_NF_CONNTRACK=y
$ grep -w CONFIG_NF_NAT .config
CONFIG_NF_NAT=m
$ grep NF_NAT_MANIP_SRC tools/testing/selftests/bpf/tools/include/vmlinux.h
    NF_NAT_MANIP_SRC = 0,
$ grep NF_NAT_MANIP_DST tools/testing/selftests/bpf/tools/include/vmlinux.h
    NF_NAT_MANIP_DST = 1,

(5) CONFIG_NF_CONNTRACK=y, CONFIG_NF_NAT=y, have definitions
$ grep -w CONFIG_NF_CONNTRACK .config
CONFIG_NF_CONNTRACK=y
$ grep -w CONFIG_NF_NAT .config
CONFIG_NF_NAT=y
$ grep NF_NAT_MANIP_SRC tools/testing/selftests/bpf/tools/include/vmlinux.h
    NF_NAT_MANIP_SRC = 0,
$ grep NF_NAT_MANIP_DST tools/testing/selftests/bpf/tools/include/vmlinux.h
    NF_NAT_MANIP_DST = 1,

(6) CONFIG_NF_CONNTRACK=y, CONFIG_NF_NAT=n, have definitions
$ grep -w CONFIG_NF_CONNTRACK .config
CONFIG_NF_CONNTRACK=y
$ grep -w CONFIG_NF_NAT .config
# CONFIG_NF_NAT is not set
$ grep NF_NAT_MANIP_SRC tools/testing/selftests/bpf/tools/include/vmlinux.h
    NF_NAT_MANIP_SRC = 0,
$ grep NF_NAT_MANIP_DST tools/testing/selftests/bpf/tools/include/vmlinux.h
    NF_NAT_MANIP_DST = 1,

(7) CONFIG_NF_CONNTRACK=n, CONFIG_NF_NAT=n, no definitions
$ grep -w CONFIG_NF_CONNTRACK .config
# CONFIG_NF_CONNTRACK is not set
$ grep -w CONFIG_NF_NAT .config
$ grep NF_NAT_MANIP_SRC tools/testing/selftests/bpf/tools/include/vmlinux.h
$ grep NF_NAT_MANIP_DST tools/testing/selftests/bpf/tools/include/vmlinux.h
$

(8) CONFIG_NF_CONNTRACK=n, CONFIG_NF_NAT=y, no definitions
This case is unable, because CONFIG_NF_NAT depends on CONFIG_NF_CONNTRACK.

Here is an alternative change to check whether CONFIG_NF_CONNTRACK
is m, enum nf_nat_manip_type___local is simple, which one is better?

$ git diff tools/testing/selftests/bpf/
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 22533a18705e..f3cf02046c20 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -325,7 +325,7 @@ endif

CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
BPF_CFLAGS = -g -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN)          \
-            -I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR)                   \
+            -I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR) -I$(TOOLSINCDIR) \
             -I$(abspath $(OUTPUT)/../usr/include)

CLANG_CFLAGS = $(CLANG_SYS_INCLUDES) \
diff --git a/tools/testing/selftests/bpf/progs/test_bpf_nf.c b/tools/testing/selftests/bpf/progs/test_bpf_nf.c
index 227e85e85dda..f2101807072f 100644
--- a/tools/testing/selftests/bpf/progs/test_bpf_nf.c
+++ b/tools/testing/selftests/bpf/progs/test_bpf_nf.c
@@ -2,6 +2,7 @@
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
+#include <linux/kconfig.h>

#define EAFNOSUPPORT 97
#define EPROTO 71
@@ -34,6 +35,13 @@ __be16 dport = 0;
int test_exist_lookup = -ENOENT;
u32 test_exist_lookup_mark = 0;

+#if IS_MODULE(CONFIG_NF_CONNTRACK)
+enum nf_nat_manip_type {
+       NF_NAT_MANIP_SRC,
+       NF_NAT_MANIP_DST
+};
+#endif
+

The above change does not work for me. The complication failed with

CLNG-BPF [test_maps] btf__core_reloc_nesting___err_missing_container.bpf.o
CLNG-BPF [test_maps] test_sysctl_loop2.bpf.o
progs/test_bpf_nf.c:168:42: error: use of undeclared identifier 'NF_NAT_MANIP_SRC'
bpf_ct_set_nat_info(ct, &saddr, sport, NF_NAT_MANIP_SRC);
^
progs/test_bpf_nf.c:171:42: error: use of undeclared identifier 'NF_NAT_MANIP_DST'
bpf_ct_set_nat_info(ct, &daddr, dport, NF_NAT_MANIP_DST);
^
2 errors generated.

Apparently, IS_MODULE(...) is recognized but it returns 0.
I do have CONFIG_NF_CONNTRACK=m in my config.
Note that I build the kernel with KBUILD_OUTPUT=<another dir>
(make -j LLVM=1) so vmlinux is in a different place.
While I build selftest
with 'make -C tools/testing/selftests/bpf -j LLVM=1' which
is in-tree.

struct nf_conn;

struct bpf_ct_opts___local {

Note that when unset CONFIG_NF_CONNTRACK, there are much more
build errors, I do not know whether it is necessary to fix it
and how to fix it properly. Here, I only consider the failed
case CONFIG_NF_CONNTRACK=m.

Thanks,
Tiezhu

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