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libbpf: Support BPF token path setting through LIBBPF_BPF_TOKEN_PATH envvar

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To allow external admin authority to override default BPF FS location
(/sys/fs/bpf) for implicit BPF token creation, teach libbpf to recognize
LIBBPF_BPF_TOKEN_PATH envvar. If it is specified and user application
didn't explicitly specify bpf_token_path option, it will be treated
exactly like bpf_token_path option, overriding default /sys/fs/bpf
location and making BPF token mandatory.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-29-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2024-01-23 18:21:25 -08:00 • committed by Alexei Starovoitov
parent b73d08d131
commit cac270ad79
2 changed files with 14 additions and 0 deletions
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6
tools/lib/bpf/libbpf.c
View file

@ -7604,6 +7604,12 @@ static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf,
return ERR_PTR(-EINVAL);
token_path = OPTS_GET(opts, bpf_token_path, NULL);
/* if user didn't specify bpf_token_path explicitly, check if
* LIBBPF_BPF_TOKEN_PATH envvar was set and treat it as bpf_token_path
* option
*/
if (!token_path)
token_path = getenv("LIBBPF_BPF_TOKEN_PATH");
if (token_path && strlen(token_path) >= PATH_MAX)
return ERR_PTR(-ENAMETOOLONG);

8
tools/lib/bpf/libbpf.h
View file

@ -183,6 +183,14 @@ struct bpf_object_open_opts {
* that accept BPF token (e.g., map creation, BTF and program loads,
* etc) automatically within instantiated BPF object.
*
* If bpf_token_path is not specified, libbpf will consult
* LIBBPF_BPF_TOKEN_PATH environment variable. If set, it will be
* taken as a value of bpf_token_path option and will force libbpf to
* either create BPF token from provided custom BPF FS path, or will
* disable implicit BPF token creation, if envvar value is an empty
* string. bpf_token_path overrides LIBBPF_BPF_TOKEN_PATH, if both are
* set at the same time.
*
* Setting bpf_token_path option to empty string disables libbpf's
* automatic attempt to create BPF token from default BPF FS mount
* point (/sys/fs/bpf), in case this default behavior is undesirable.