From: Andrii Nakryiko <andriin@fb.com>
Date: Thu, 24 Sep 2020 10:17:05 -0700
Subject: libbpf: Fix XDP program load regression for old kernels
Patch-mainline: v5.9
Git-commit: 87f92ac4c12758c4da3bbe4393f1d884b610b8a6
References: bsc#1177028

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: dc8698cac7aa ("libbpf: Add support for BPF XDP link")
Reported-by: Nikita Shirokov <tehnerd@tehnerd.com>
Reported-by: Udip Pant <udippant@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200924171705.3803628-1-andriin@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
 tools/lib/bpf/libbpf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6927,7 +6927,7 @@ static const struct bpf_sec_def section_
 						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),