Commit 87f92ac4 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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libbpf: Fix XDP program load regression for old kernels 



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.

Fixes: dc8698ca ("libbpf: Add support for BPF XDP link")
Reported-by: default avatarNikita Shirokov <tehnerd@tehnerd.com>
Reported-by: default avatarUdip Pant <udippant@fb.com>
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200924171705.3803628-1-andriin@fb.com
parent 12450081

tools/lib/bpf/libbpf.c

+1 −1
Original line number Diff line number Diff line
@@ -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),

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