[PATCH bpf-next] selftests/bpf: support building selftests when CONFIG_NF_CONNTRACK=m

* [PATCH bpf-next] selftests/bpf: support building selftests when CONFIG_NF_CONNTRACK=m
@ 2022-06-23 11:10 Alan Maguire
  2022-06-23 17:56 ` Andrii Nakryiko
  0 siblings, 1 reply; 4+ messages in thread
From: Alan Maguire @ 2022-06-23 11:10 UTC (permalink / raw)
  To: ast, daniel, andrii
  Cc: kafai, songliubraving, yhs, john.fastabend, kpsingh, davem, kuba,
	hawk, bpf, Alan Maguire

when CONFIG_NF_CONNTRACK=m, vmlinux BTF does not contain
BPF_F_CURRENT_NETNS or bpf_ct_opts; they are both found in nf_conntrack
BTF; for example:

bpftool btf dump file /sys/kernel/btf/nf_conntrack|grep ct_opts
[114754] STRUCT 'bpf_ct_opts' size=12 vlen=5

This causes compilation errors as follows:

  CLNG-BPF [test_maps] xdp_synproxy_kern.o
progs/xdp_synproxy_kern.c:83:14: error: declaration of 'struct bpf_ct_opts' will not be visible outside of this function [-Werror,-Wvisibility]
                                         struct bpf_ct_opts *opts,
                                                ^
progs/xdp_synproxy_kern.c:89:14: error: declaration of 'struct bpf_ct_opts' will not be visible outside of this function [-Werror,-Wvisibility]
                                         struct bpf_ct_opts *opts,
                                                ^
progs/xdp_synproxy_kern.c:397:15: error: use of undeclared identifier 'BPF_F_CURRENT_NETNS'; did you mean 'BPF_F_CURRENT_CPU'?
                .netns_id = BPF_F_CURRENT_NETNS,
                            ^~~~~~~~~~~~~~~~~~~
                            BPF_F_CURRENT_CPU
tools/testing/selftests/bpf/tools/include/vmlinux.h:43115:2: note: 'BPF_F_CURRENT_CPU' declared here
        BPF_F_CURRENT_CPU = 4294967295,

While tools/testing/selftests/bpf/config does specify
CONFIG_NF_CONNTRACK=y, it would be good to use this case to show
how we can generate a module header file via split BTF.

In the selftests Makefile, we define NF_CONNTRACK BTF via VMLINUX_BTF
(thus gaining the path determination logic it uses).  If the nf_conntrack
BTF file exists (which means it is built as a module), we run
"bpftool btf dump" to generate module BTF, and if not we simply copy
vmlinux.h to nf_conntrack.h; this allows us to avoid having to pass
a #define or deal with CONFIG variables in the program.

With these changes the test builds and passes:

Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
---
 tools/testing/selftests/bpf/Makefile                  | 11 +++++++++++
 tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c |  2 +-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index cb8e552..a5fa636 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -141,6 +141,8 @@ VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
 ifeq ($(VMLINUX_BTF),)
 $(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)")
 endif
+# If nf_conntrack is a module, need BTF for it also
+NF_CONNTRACK_BTF ?= $(shell dirname $(VMLINUX_BTF))/nf_conntrack
 
 # Define simple and short `make test_progs`, `make test_sysctl`, etc targets
 # to build individual tests.
@@ -280,6 +282,14 @@ else
 	$(Q)cp "$(VMLINUX_H)" $@
 endif
 
+$(INCLUDE_DIR)/nf_conntrack.h: $(INCLUDE_DIR)/vmlinux.h
+ifneq ("$(wildcard $(NF_CONNTRACK_BTF))","")
+	$(call msg,GEN,,$@)
+	$(BPFTOOL) btf dump file $(NF_CONNTRACK_BTF) format c > $@
+else
+	$(Q)cp $(INCLUDE_DIR)/vmlinux.h $@
+endif
+
 $(RESOLVE_BTFIDS): $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/resolve_btfids	\
 		       $(TOOLSDIR)/bpf/resolve_btfids/main.c	\
 		       $(TOOLSDIR)/lib/rbtree.c			\
@@ -417,6 +427,7 @@ $(TRUNNER_BPF_OBJS): $(TRUNNER_OUTPUT)/%.o:				\
 		     $(TRUNNER_BPF_PROGS_DIR)/%.c			\
 		     $(TRUNNER_BPF_PROGS_DIR)/*.h			\
 		     $$(INCLUDE_DIR)/vmlinux.h				\
+		     $$(INCLUDE_DIR)/nf_conntrack.h			\
 		     $(wildcard $(BPFDIR)/bpf_*.h)			\
 		     $(wildcard $(BPFDIR)/*.bpf.h)			\
 		     | $(TRUNNER_OUTPUT) $$(BPFOBJ)
diff --git a/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c b/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
index 9fd62e9..8c5f46e 100644
--- a/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
+++ b/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: LGPL-2.1 OR BSD-2-Clause
 /* Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES. All rights reserved. */
 
-#include "vmlinux.h"
+#include "nf_conntrack.h"
 
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_endian.h>
-- 
1.8.3.1


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