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From: Andrii Nakryiko <andriin@fb.com>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
	<daniel@iogearbox.net>
Cc: <andrii.nakryiko@gmail.com>, <kernel-team@fb.com>,
	Andrii Nakryiko <andriin@fb.com>,
	Nikita Shirokov <tehnerd@tehnerd.com>,
	Udip Pant <udippant@fb.com>
Subject: [PATCH bpf] libbpf: fix XDP program load regression for old kernels
Date: Thu, 24 Sep 2020 10:17:05 -0700	[thread overview]
Message-ID: <20200924171705.3803628-1-andriin@fb.com> (raw)

Fix regression in libbpf, introduced by XDP link change, which causes XDP
programs to fail to be loaded into kernel due to specified BPF_XDP
expected_attach_type. While kernel doesn't enforce expected_attach_type for
BPF_PROG_TYPE_XDP, some old kernels already support XDP program, but they
don't yet recognize expected_attach_type field in bpf_attr, so setting it to
non-zero value causes program load to fail.

Luckily, libbpf already has a mechanism to deal with such cases, so just make
expected_attach_type optional for XDP programs.

Reported-by: Nikita Shirokov <tehnerd@tehnerd.com>
Reported-by: Udip Pant <udippant@fb.com>
Fixes: dc8698cac7aa ("libbpf: Add support for BPF XDP link")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/libbpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7253b833576c..e493d6048143 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6925,7 +6925,7 @@ static const struct bpf_sec_def section_defs[] = {
 						BPF_XDP_DEVMAP),
 	BPF_EAPROG_SEC("xdp_cpumap/",		BPF_PROG_TYPE_XDP,
 						BPF_XDP_CPUMAP),
-	BPF_EAPROG_SEC("xdp",			BPF_PROG_TYPE_XDP,
+	BPF_APROG_SEC("xdp",			BPF_PROG_TYPE_XDP,
 						BPF_XDP),
 	BPF_PROG_SEC("perf_event",		BPF_PROG_TYPE_PERF_EVENT),
 	BPF_PROG_SEC("lwt_in",			BPF_PROG_TYPE_LWT_IN),
-- 
2.24.1


             reply	other threads:[~2020-09-24 17:17 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-24 17:17 Andrii Nakryiko [this message]
2020-09-24 17:34 ` [PATCH bpf] libbpf: fix XDP program load regression for old kernels Alexei Starovoitov
2020-09-24 17:42   ` Andrii Nakryiko

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