netdev - [PATCH bpf-next] bpf: libbpf: retry program creation without the name

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Message-Id: <20181120004625.243494-1-sdf@google.com>
Date:   Mon, 19 Nov 2018 16:46:25 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     netdev@...r.kernel.org, daniel@...earbox.net
Cc:     ast@...nel.org, vladum@...gle.com,
        Stanislav Fomichev <sdf@...gle.com>
Subject: [PATCH bpf-next] bpf: libbpf: retry program creation without the name

[Recent commit 23499442c319 ("bpf: libbpf: retry map creation without
the name") fixed this issue for maps, let's do the same for programs.]

Since commit 88cda1c9da02 ("bpf: libbpf: Provide basic API support
to specify BPF obj name"), libbpf unconditionally sets bpf_attr->name
for programs. Pre v4.14 kernels don't know about programs names and
return an error about unexpected non-zero data. Retry sys_bpf without
a program name to cover older kernels.

Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
---
 tools/lib/bpf/bpf.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 961e1b9fc592..cbe9d757c646 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -212,6 +212,16 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
 	if (fd >= 0 || !log_buf || !log_buf_sz)
 		return fd;
 
+	if (fd < 0 && errno == E2BIG && load_attr->name) {
+		/* Retry the same syscall, but without the name.
+		 * Pre v4.14 kernels don't support prog names.
+		 */
+		memset(attr.prog_name, 0, sizeof(attr.prog_name));
+		fd = sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
+		if (fd >= 0 || !log_buf || !log_buf_sz)
+			return fd;
+	}
+
 	/* Try again with log */
 	attr.log_buf = ptr_to_u64(log_buf);
 	attr.log_size = log_buf_sz;
-- 
2.19.1.1215.g8438c0b245-goog