netdev - [PATCH bpf-next v2 1/2] bpf: libbpf: retry program creation without the name

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Message-Id: <20181120231510.46332-1-sdf@google.com>
Date:   Tue, 20 Nov 2018 15:15:09 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     netdev@...r.kernel.org, ast@...nel.org
Cc:     daniel@...earbox.net, Stanislav Fomichev <sdf@...gle.com>
Subject: [PATCH bpf-next v2 1/2] 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
bpf_load_program_xattr without a program name to cover older kernels.

Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
---
 tools/lib/bpf/libbpf.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index cb6565d79603..2ea14dfa28fc 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1401,6 +1401,18 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
 
 	ret = bpf_load_program_xattr(&load_attr, log_buf, BPF_LOG_BUF_SIZE);
 
+	if (ret < 0 && errno == E2BIG && load_attr.name) {
+		/* Retry the same operation, but without the name.
+		 * Pre v4.14 kernels don't support prog names.
+		 */
+		cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
+		pr_warning("Error in bpf_load_program_xattr(%s):%s(%d). Retrying without name.\n",
+			   prog->name, cp, errno);
+		load_attr.name = NULL;
+		ret = bpf_load_program_xattr(&load_attr, log_buf,
+					     BPF_LOG_BUF_SIZE);
+	}
+
 	if (ret >= 0) {
 		*pfd = ret;
 		ret = 0;
-- 
2.19.1.1215.g8438c0b245-goog