From: Andrey Ignatov <rdna@fb.com>
Date: Tue, 7 Jan 2020 17:40:06 -0800
Subject: bpf: Document BPF_F_QUERY_EFFECTIVE flag
Patch-mainline: v5.6-rc1
Git-commit: f5bfcd953d811dbb8913de36b96b38da6bb62135
References: bsc#1177028
Document BPF_F_QUERY_EFFECTIVE flag, mostly to clarify how it affects
attach_flags what may not be obvious and what may lead to confision.
Specifically attach_flags is returned only for target_fd but if programs
are inherited from an ancestor cgroup then returned attach_flags for
current cgroup may be confusing. For example, two effective programs of
same attach_type can be returned but w/o BPF_F_ALLOW_MULTI in
attach_flags.
Simple repro:
# bpftool c s /sys/fs/cgroup/path/to/task
ID AttachType AttachFlags Name
# bpftool c s /sys/fs/cgroup/path/to/task effective
ID AttachType AttachFlags Name
95043 ingress tw_ipt_ingress
95048 ingress tw_ingress
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200108014006.938363-1-rdna@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
include/uapi/linux/bpf.h | 7 ++++++-
tools/include/uapi/linux/bpf.h | 7 ++++++-
2 files changed, 12 insertions(+), 2 deletions(-)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -359,7 +359,12 @@ enum bpf_attach_type {
/* Enable memory-mapping BPF map */
#define BPF_F_MMAPABLE (1U << 10)
-/* flags for BPF_PROG_QUERY */
+/* Flags for BPF_PROG_QUERY. */
+
+/* Query effective (directly attached + inherited from ancestor cgroups)
+ * programs that will be executed for events within a cgroup.
+ * attach_flags with this flag are returned only for directly attached programs.
+ */
#define BPF_F_QUERY_EFFECTIVE (1U << 0)
enum bpf_stack_build_id_status {
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -359,7 +359,12 @@ enum bpf_attach_type {
/* Enable memory-mapping BPF map */
#define BPF_F_MMAPABLE (1U << 10)
-/* flags for BPF_PROG_QUERY */
+/* Flags for BPF_PROG_QUERY. */
+
+/* Query effective (directly attached + inherited from ancestor cgroups)
+ * programs that will be executed for events within a cgroup.
+ * attach_flags with this flag are returned only for directly attached programs.
+ */
#define BPF_F_QUERY_EFFECTIVE (1U << 0)
enum bpf_stack_build_id_status {