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 neither bpf_token_path nor bpf_token_fd
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@xxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 14 ++++++++++----
tools/lib/bpf/libbpf.h | 13 +++++++++++--
2 files changed, 21 insertions(+), 6 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index db94bbe163e3..4b5ff9508e18 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -7171,11 +7171,17 @@ static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf,
/* non-empty token path can't be combined with invalid token FD */
if (token_path && token_path[0] != '\0' && token_fd < 0)
return ERR_PTR(-EINVAL);
+ /* empty token path can't be combined with valid token FD */
+ if (token_path && token_path[0] == '\0' && token_fd > 0)
+ return ERR_PTR(-EINVAL);
+ /* if user didn't specify bpf_token_path/bpf_token_fd explicitly,
+ * check if LIBBPF_BPF_TOKEN_PATH envvar was set and treat it as
+ * bpf_token_path option
+ */
+ if (token_fd == 0 && !token_path)
+ token_path = getenv("LIBBPF_BPF_TOKEN_PATH");
+ /* empty token_path is equivalent to invalid token_fd */
if (token_path && token_path[0] == '\0') {
- /* empty token path can't be combined with valid token FD */
- if (token_fd > 0)
- return ERR_PTR(-EINVAL);
- /* empty token_path is equivalent to invalid token_fd */
token_path = NULL;
token_fd = -1;
}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index d3de39b537f3..916904bd2a7a 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -185,8 +185,16 @@ struct bpf_object_open_opts {
* attempt to create BPF token from default BPF FS mount point
* (/sys/fs/bpf), in case this default behavior is undesirable.
*
+ * If bpf_token_path and bpf_token_fd are 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 and bpf_token_fd are mutually exclusive and only one
- * of those options should be set.
+ * of those options should be set. Either of them overrides
+ * LIBBPF_BPF_TOKEN_PATH envvar.
*/
int bpf_token_fd;
/* Path to BPF FS mount point to derive BPF token from.
@@ -200,7 +208,8 @@ struct bpf_object_open_opts {
* point (/sys/fs/bpf), in case this default behavior is undesirable.
*
* bpf_token_path and bpf_token_fd are mutually exclusive and only one
- * of those options should be set.
+ * of those options should be set. Either of them overrides
+ * LIBBPF_BPF_TOKEN_PATH envvar.
*/
const char *bpf_token_path;
--
2.34.1
