* [PATCH v4 bpf-next 0/5] Make BPF CGROUP_STORAGE map usable by different programs at once
@ 2020-07-20 19:54 YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 1/5] selftests/bpf: Add test for CGROUP_STORAGE map on multiple attaches YiFei Zhu
` (4 more replies)
0 siblings, 5 replies; 13+ messages in thread
From: YiFei Zhu @ 2020-07-20 19:54 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Daniel Borkmann, Stanislav Fomichev,
Mahesh Bandewar, Roman Gushchin, Andrii Nakryiko,
Martin KaFai Lau, YiFei Zhu
From: YiFei Zhu <zhuyifei@google.com>
To access the storage in a CGROUP_STORAGE map, one uses
bpf_get_local_storage helper, which is extremely fast due to its
use of per-CPU variables. However, its whole code is built on
the assumption that one map can only be used by one program at any
time, and this prohibits any sharing of data between multiple
programs using these maps, eliminating a lot of use cases, such
as some per-cgroup configuration storage, written to by a
setsockopt program and read by a cg_sock_addr program.
Why not use other map types? The great part of CGROUP_STORAGE map
is that it is isolated by different cgroups its attached to. When
one program uses bpf_get_local_storage, even on the same map, it
gets different storages if it were run as a result of attaching
to different cgroups. The kernel manages the storages, simplifying
BPF program or userspace. In theory, one could probably use other
maps like array or hash to do the same thing, but it would be a
major overhead / complexity. Userspace needs to know when a cgroup
is being freed in order to free up a space in the replacement map.
This patch set introduces a significant change to the semantics of
CGROUP_STORAGE map type. Instead of each storage being tied to one
single attachment, it is shared across different attachments to
the same cgroup, and persists until either the map or the cgroup
attached to is being freed.
The attach_type field of the map key struct bpf_cgroup_storage_key
is now unused. If userspace reads it it will always be zero. If
userspace sends us a non-zero value it will be ignored.
How could this break existing users?
* Users that uses detach & reattach / program replacement as a
shortcut to zeroing the storage. Since we need sharing between
programs, we cannot zero the storage. Users that expect this
behavior should either attach a program with a new map, or
explicitly zero the map with a syscall.
* Programs that expect isolation from different attach types. In
reality, attaching the same program to different attach types,
relying on that expected_attach_type not being enforced, should
rarely happen, if at all.
* Userspace that does memcmp on the storage key when fetching
map keys. In reality, if user wants to use a fixed key they
would use {delete,lookup,update}_elem, rather than get_next_key.
These cases are dependent on undocumented implementation details,
so the impact should be very minimal.
Patch 1 introduces a test on the old expected behavior of the map
type.
Patch 2 introduces a test showing how two programs cannot share
one such map.
Patch 3 implements the change of semantics to the map.
Patch 4 amends the new test such that it yields the behavior we
expect from the change.
Patch 5 documents the map type.
Changes since RFC:
* Clarify commit message in patch 3 such that it says the lifetime
of the storage is ended at the freeing of the cgroup_bpf, rather
than the cgroup itself.
* Restored an -ENOMEM check in __cgroup_bpf_attach.
* Update selftests for recent change in network_helpers API.
Changes since v1:
* s/CHECK_FAIL/CHECK/
* s/bpf_prog_attach/bpf_program__attach_cgroup/
* Moved test__start_subtest to test_cg_storage_multi.
* Removed some redundant CHECK_FAIL where they are already CHECK-ed.
Changes since v2:
* Lock cgroup_mutex during map_free.
* Publish new storages only if attach is successful, by tracking
exactly which storages are reused in an array of bools.
* Mention bpftool map dump showing a value of zero for attach_type
in patch 3 commit message.
Changes since v3:
* Use a much simpler lookup and allocate-if-not-exist from the fact
that cgroup_mutex is locked during attach.
* Removed an unnecessary spinlock hold.
YiFei Zhu (5):
selftests/bpf: Add test for CGROUP_STORAGE map on multiple attaches
selftests/bpf: Test CGROUP_STORAGE map can't be used by multiple progs
bpf: Make cgroup storages shared across attaches on the same cgroup
selftests/bpf: Test CGROUP_STORAGE behavior on shared egress + ingress
Documentation/bpf: Document CGROUP_STORAGE map type
Documentation/bpf/index.rst | 9 +
Documentation/bpf/map_cgroup_storage.rst | 95 +++++++
include/linux/bpf-cgroup.h | 15 +-
include/uapi/linux/bpf.h | 2 +-
kernel/bpf/cgroup.c | 69 +++--
kernel/bpf/core.c | 12 -
kernel/bpf/local_storage.c | 73 ++---
tools/include/uapi/linux/bpf.h | 2 +-
.../bpf/prog_tests/cg_storage_multi.c | 265 ++++++++++++++++++
.../selftests/bpf/progs/cg_storage_multi.h | 13 +
.../progs/cg_storage_multi_egress_ingress.c | 45 +++
.../bpf/progs/cg_storage_multi_egress_only.c | 33 +++
12 files changed, 536 insertions(+), 97 deletions(-)
create mode 100644 Documentation/bpf/map_cgroup_storage.rst
create mode 100644 tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
create mode 100644 tools/testing/selftests/bpf/progs/cg_storage_multi.h
create mode 100644 tools/testing/selftests/bpf/progs/cg_storage_multi_egress_ingress.c
create mode 100644 tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c
--
2.27.0
^ permalink raw reply [flat|nested] 13+ messages in thread
* [PATCH v4 bpf-next 1/5] selftests/bpf: Add test for CGROUP_STORAGE map on multiple attaches
2020-07-20 19:54 [PATCH v4 bpf-next 0/5] Make BPF CGROUP_STORAGE map usable by different programs at once YiFei Zhu
@ 2020-07-20 19:54 ` YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 2/5] selftests/bpf: Test CGROUP_STORAGE map can't be used by multiple progs YiFei Zhu
` (3 subsequent siblings)
4 siblings, 0 replies; 13+ messages in thread
From: YiFei Zhu @ 2020-07-20 19:54 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Daniel Borkmann, Stanislav Fomichev,
Mahesh Bandewar, Roman Gushchin, Andrii Nakryiko,
Martin KaFai Lau, YiFei Zhu
From: YiFei Zhu <zhuyifei@google.com>
This test creates a parent cgroup, and a child of that cgroup.
It attaches a cgroup_skb/egress program that simply counts packets,
to a global variable (ARRAY map), and to a CGROUP_STORAGE map.
The program is first attached to the parent cgroup only, then to
parent and child.
The test cases sends a message within the child cgroup, and because
the program is inherited across parent / child cgroups, it will
trigger the egress program for both the parent and child, if they
exist. The program, when looking up a CGROUP_STORAGE map, uses the
cgroup and attach type of the attachment parameters; therefore,
both attaches uses different cgroup storages.
We assert that all packet counts returns what we expects.
Signed-off-by: YiFei Zhu <zhuyifei@google.com>
---
.../bpf/prog_tests/cg_storage_multi.c | 163 ++++++++++++++++++
.../bpf/progs/cg_storage_multi_egress_only.c | 30 ++++
2 files changed, 193 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
create mode 100644 tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c
diff --git a/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c b/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
new file mode 100644
index 000000000000..6d5a2194e036
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright 2020 Google LLC.
+ */
+
+#include <test_progs.h>
+#include <cgroup_helpers.h>
+#include <network_helpers.h>
+
+#include "cg_storage_multi_egress_only.skel.h"
+
+#define PARENT_CGROUP "/cgroup_storage"
+#define CHILD_CGROUP "/cgroup_storage/child"
+
+static int duration;
+
+static bool assert_storage(struct bpf_map *map, const char *cgroup_path,
+ __u32 expected)
+{
+ struct bpf_cgroup_storage_key key = {0};
+ __u32 value;
+ int map_fd;
+
+ map_fd = bpf_map__fd(map);
+
+ key.cgroup_inode_id = get_cgroup_id(cgroup_path);
+ key.attach_type = BPF_CGROUP_INET_EGRESS;
+ if (CHECK(bpf_map_lookup_elem(map_fd, &key, &value) < 0,
+ "map-lookup", "errno %d", errno))
+ return true;
+ if (CHECK(value != expected,
+ "assert-storage", "got %u expected %u", value, expected))
+ return true;
+
+ return false;
+}
+
+static bool assert_storage_noexist(struct bpf_map *map, const char *cgroup_path)
+{
+ struct bpf_cgroup_storage_key key = {0};
+ __u32 value;
+ int map_fd;
+
+ map_fd = bpf_map__fd(map);
+
+ key.cgroup_inode_id = get_cgroup_id(cgroup_path);
+ key.attach_type = BPF_CGROUP_INET_EGRESS;
+ if (CHECK(bpf_map_lookup_elem(map_fd, &key, &value) == 0,
+ "map-lookup", "succeeded, expected ENOENT"))
+ return true;
+ if (CHECK(errno != ENOENT,
+ "map-lookup", "errno %d, expected ENOENT", errno))
+ return true;
+
+ return false;
+}
+
+static bool connect_send(const char *cgroup_path)
+{
+ bool res = true;
+ int server_fd = -1, client_fd = -1;
+
+ if (join_cgroup(cgroup_path))
+ goto out_clean;
+
+ server_fd = start_server(AF_INET, SOCK_DGRAM, NULL, 0, 0);
+ if (server_fd < 0)
+ goto out_clean;
+
+ client_fd = connect_to_fd(server_fd, 0);
+ if (client_fd < 0)
+ goto out_clean;
+
+ if (send(client_fd, "message", strlen("message"), 0) < 0)
+ goto out_clean;
+
+ res = false;
+
+out_clean:
+ close(client_fd);
+ close(server_fd);
+ return res;
+}
+
+static void test_egress_only(int parent_cgroup_fd, int child_cgroup_fd)
+{
+ struct cg_storage_multi_egress_only *obj;
+ struct bpf_link *parent_link = NULL, *child_link = NULL;
+ bool err;
+
+ obj = cg_storage_multi_egress_only__open_and_load();
+ if (CHECK(!obj, "skel-load", "errno %d", errno))
+ return;
+
+ /* Attach to parent cgroup, trigger packet from child.
+ * Assert that there is only one run and in that run the storage is
+ * parent cgroup's storage.
+ * Also assert that child cgroup's storage does not exist
+ */
+ parent_link = bpf_program__attach_cgroup(obj->progs.egress,
+ parent_cgroup_fd);
+ if (CHECK(IS_ERR(parent_link), "parent-cg-attach",
+ "err %ld", PTR_ERR(parent_link)))
+ goto close_bpf_object;
+ err = connect_send(CHILD_CGROUP);
+ if (CHECK(err, "first-connect-send", "errno %d", errno))
+ goto close_bpf_object;
+ if (CHECK(obj->bss->invocations != 1,
+ "first-invoke", "invocations=%d", obj->bss->invocations))
+ goto close_bpf_object;
+ if (assert_storage(obj->maps.cgroup_storage, PARENT_CGROUP, 1))
+ goto close_bpf_object;
+ if (assert_storage_noexist(obj->maps.cgroup_storage, CHILD_CGROUP))
+ goto close_bpf_object;
+
+ /* Attach to parent and child cgroup, trigger packet from child.
+ * Assert that there are two additional runs, one that run with parent
+ * cgroup's storage and one with child cgroup's storage.
+ */
+ child_link = bpf_program__attach_cgroup(obj->progs.egress,
+ child_cgroup_fd);
+ if (CHECK(IS_ERR(child_link), "child-cg-attach",
+ "err %ld", PTR_ERR(child_link)))
+ goto close_bpf_object;
+ err = connect_send(CHILD_CGROUP);
+ if (CHECK(err, "second-connect-send", "errno %d", errno))
+ goto close_bpf_object;
+ if (CHECK(obj->bss->invocations != 3,
+ "second-invoke", "invocations=%d", obj->bss->invocations))
+ goto close_bpf_object;
+ if (assert_storage(obj->maps.cgroup_storage, PARENT_CGROUP, 2))
+ goto close_bpf_object;
+ if (assert_storage(obj->maps.cgroup_storage, CHILD_CGROUP, 1))
+ goto close_bpf_object;
+
+close_bpf_object:
+ if (parent_link)
+ bpf_link__destroy(parent_link);
+ if (child_link)
+ bpf_link__destroy(child_link);
+
+ cg_storage_multi_egress_only__destroy(obj);
+}
+
+void test_cg_storage_multi(void)
+{
+ int parent_cgroup_fd = -1, child_cgroup_fd = -1;
+
+ parent_cgroup_fd = test__join_cgroup(PARENT_CGROUP);
+ if (CHECK(parent_cgroup_fd < 0, "cg-create-parent", "errno %d", errno))
+ goto close_cgroup_fd;
+ child_cgroup_fd = create_and_get_cgroup(CHILD_CGROUP);
+ if (CHECK(child_cgroup_fd < 0, "cg-create-child", "errno %d", errno))
+ goto close_cgroup_fd;
+
+ if (test__start_subtest("egress_only"))
+ test_egress_only(parent_cgroup_fd, child_cgroup_fd);
+
+close_cgroup_fd:
+ close(child_cgroup_fd);
+ close(parent_cgroup_fd);
+}
diff --git a/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c b/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c
new file mode 100644
index 000000000000..ec0165d07105
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright 2020 Google LLC.
+ */
+
+#include <errno.h>
+#include <linux/bpf.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+#include <bpf/bpf_helpers.h>
+
+struct {
+ __uint(type, BPF_MAP_TYPE_CGROUP_STORAGE);
+ __type(key, struct bpf_cgroup_storage_key);
+ __type(value, __u32);
+} cgroup_storage SEC(".maps");
+
+__u32 invocations = 0;
+
+SEC("cgroup_skb/egress")
+int egress(struct __sk_buff *skb)
+{
+ __u32 *ptr_cg_storage = bpf_get_local_storage(&cgroup_storage, 0);
+
+ __sync_fetch_and_add(ptr_cg_storage, 1);
+ __sync_fetch_and_add(&invocations, 1);
+
+ return 1;
+}
--
2.27.0
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH v4 bpf-next 2/5] selftests/bpf: Test CGROUP_STORAGE map can't be used by multiple progs
2020-07-20 19:54 [PATCH v4 bpf-next 0/5] Make BPF CGROUP_STORAGE map usable by different programs at once YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 1/5] selftests/bpf: Add test for CGROUP_STORAGE map on multiple attaches YiFei Zhu
@ 2020-07-20 19:54 ` YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup YiFei Zhu
` (2 subsequent siblings)
4 siblings, 0 replies; 13+ messages in thread
From: YiFei Zhu @ 2020-07-20 19:54 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Daniel Borkmann, Stanislav Fomichev,
Mahesh Bandewar, Roman Gushchin, Andrii Nakryiko,
Martin KaFai Lau, YiFei Zhu
From: YiFei Zhu <zhuyifei@google.com>
The current assumption is that the lifetime of a cgroup storage
is tied to the program's attachment. The storage is created in
cgroup_bpf_attach, and released upon cgroup_bpf_detach and
cgroup_bpf_release.
Because the current semantics is that each attachment gets a
completely independent cgroup storage, and you can have multiple
programs attached to the same (cgroup, attach type) pair, the key
of the CGROUP_STORAGE map, looking up the map with this pair could
yield multiple storages, and that is not permitted. Therefore,
the kernel verifier checks that two programs cannot share the same
CGROUP_STORAGE map, even if they have different expected attach
types, considering that the actual attach type does not always
have to be equal to the expected attach type.
The test creates a CGROUP_STORAGE map and make it shared across
two different programs, one cgroup_skb/egress and one /ingress.
It asserts that the two programs cannot be both loaded, due to
verifier failure from the above reason.
Signed-off-by: YiFei Zhu <zhuyifei@google.com>
---
.../bpf/prog_tests/cg_storage_multi.c | 42 +++++++++++++----
.../selftests/bpf/progs/cg_storage_multi.h | 13 ++++++
.../progs/cg_storage_multi_egress_ingress.c | 45 +++++++++++++++++++
.../bpf/progs/cg_storage_multi_egress_only.c | 9 ++--
4 files changed, 98 insertions(+), 11 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/cg_storage_multi.h
create mode 100644 tools/testing/selftests/bpf/progs/cg_storage_multi_egress_ingress.c
diff --git a/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c b/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
index 6d5a2194e036..1f4ab437ddb9 100644
--- a/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
+++ b/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
@@ -8,7 +8,10 @@
#include <cgroup_helpers.h>
#include <network_helpers.h>
+#include "progs/cg_storage_multi.h"
+
#include "cg_storage_multi_egress_only.skel.h"
+#include "cg_storage_multi_egress_ingress.skel.h"
#define PARENT_CGROUP "/cgroup_storage"
#define CHILD_CGROUP "/cgroup_storage/child"
@@ -16,10 +19,10 @@
static int duration;
static bool assert_storage(struct bpf_map *map, const char *cgroup_path,
- __u32 expected)
+ struct cgroup_value *expected)
{
struct bpf_cgroup_storage_key key = {0};
- __u32 value;
+ struct cgroup_value value;
int map_fd;
map_fd = bpf_map__fd(map);
@@ -29,8 +32,8 @@ static bool assert_storage(struct bpf_map *map, const char *cgroup_path,
if (CHECK(bpf_map_lookup_elem(map_fd, &key, &value) < 0,
"map-lookup", "errno %d", errno))
return true;
- if (CHECK(value != expected,
- "assert-storage", "got %u expected %u", value, expected))
+ if (CHECK(memcmp(&value, expected, sizeof(struct cgroup_value)),
+ "assert-storage", "storages differ"))
return true;
return false;
@@ -39,7 +42,7 @@ static bool assert_storage(struct bpf_map *map, const char *cgroup_path,
static bool assert_storage_noexist(struct bpf_map *map, const char *cgroup_path)
{
struct bpf_cgroup_storage_key key = {0};
- __u32 value;
+ struct cgroup_value value;
int map_fd;
map_fd = bpf_map__fd(map);
@@ -86,6 +89,7 @@ static bool connect_send(const char *cgroup_path)
static void test_egress_only(int parent_cgroup_fd, int child_cgroup_fd)
{
struct cg_storage_multi_egress_only *obj;
+ struct cgroup_value expected_cgroup_value;
struct bpf_link *parent_link = NULL, *child_link = NULL;
bool err;
@@ -109,7 +113,9 @@ static void test_egress_only(int parent_cgroup_fd, int child_cgroup_fd)
if (CHECK(obj->bss->invocations != 1,
"first-invoke", "invocations=%d", obj->bss->invocations))
goto close_bpf_object;
- if (assert_storage(obj->maps.cgroup_storage, PARENT_CGROUP, 1))
+ expected_cgroup_value = (struct cgroup_value) { .egress_pkts = 1 };
+ if (assert_storage(obj->maps.cgroup_storage,
+ PARENT_CGROUP, &expected_cgroup_value))
goto close_bpf_object;
if (assert_storage_noexist(obj->maps.cgroup_storage, CHILD_CGROUP))
goto close_bpf_object;
@@ -129,9 +135,13 @@ static void test_egress_only(int parent_cgroup_fd, int child_cgroup_fd)
if (CHECK(obj->bss->invocations != 3,
"second-invoke", "invocations=%d", obj->bss->invocations))
goto close_bpf_object;
- if (assert_storage(obj->maps.cgroup_storage, PARENT_CGROUP, 2))
+ expected_cgroup_value = (struct cgroup_value) { .egress_pkts = 2 };
+ if (assert_storage(obj->maps.cgroup_storage,
+ PARENT_CGROUP, &expected_cgroup_value))
goto close_bpf_object;
- if (assert_storage(obj->maps.cgroup_storage, CHILD_CGROUP, 1))
+ expected_cgroup_value = (struct cgroup_value) { .egress_pkts = 1 };
+ if (assert_storage(obj->maps.cgroup_storage,
+ CHILD_CGROUP, &expected_cgroup_value))
goto close_bpf_object;
close_bpf_object:
@@ -143,6 +153,19 @@ static void test_egress_only(int parent_cgroup_fd, int child_cgroup_fd)
cg_storage_multi_egress_only__destroy(obj);
}
+static void test_egress_ingress(int parent_cgroup_fd, int child_cgroup_fd)
+{
+ struct cg_storage_multi_egress_ingress *obj;
+
+ /* Cannot load both programs due to verifier failure:
+ * "only one cgroup storage of each type is allowed"
+ */
+ obj = cg_storage_multi_egress_ingress__open_and_load();
+ if (CHECK(obj || errno != EBUSY,
+ "skel-load", "errno %d, expected EBUSY", errno))
+ return;
+}
+
void test_cg_storage_multi(void)
{
int parent_cgroup_fd = -1, child_cgroup_fd = -1;
@@ -157,6 +180,9 @@ void test_cg_storage_multi(void)
if (test__start_subtest("egress_only"))
test_egress_only(parent_cgroup_fd, child_cgroup_fd);
+ if (test__start_subtest("egress_ingress"))
+ test_egress_ingress(parent_cgroup_fd, child_cgroup_fd);
+
close_cgroup_fd:
close(child_cgroup_fd);
close(parent_cgroup_fd);
diff --git a/tools/testing/selftests/bpf/progs/cg_storage_multi.h b/tools/testing/selftests/bpf/progs/cg_storage_multi.h
new file mode 100644
index 000000000000..a0778fe7857a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/cg_storage_multi.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __PROGS_CG_STORAGE_MULTI_H
+#define __PROGS_CG_STORAGE_MULTI_H
+
+#include <asm/types.h>
+
+struct cgroup_value {
+ __u32 egress_pkts;
+ __u32 ingress_pkts;
+};
+
+#endif
diff --git a/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_ingress.c b/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_ingress.c
new file mode 100644
index 000000000000..9ce386899365
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_ingress.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright 2020 Google LLC.
+ */
+
+#include <errno.h>
+#include <linux/bpf.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+#include <bpf/bpf_helpers.h>
+
+#include "progs/cg_storage_multi.h"
+
+struct {
+ __uint(type, BPF_MAP_TYPE_CGROUP_STORAGE);
+ __type(key, struct bpf_cgroup_storage_key);
+ __type(value, struct cgroup_value);
+} cgroup_storage SEC(".maps");
+
+__u32 invocations = 0;
+
+SEC("cgroup_skb/egress")
+int egress(struct __sk_buff *skb)
+{
+ struct cgroup_value *ptr_cg_storage =
+ bpf_get_local_storage(&cgroup_storage, 0);
+
+ __sync_fetch_and_add(&ptr_cg_storage->egress_pkts, 1);
+ __sync_fetch_and_add(&invocations, 1);
+
+ return 1;
+}
+
+SEC("cgroup_skb/ingress")
+int ingress(struct __sk_buff *skb)
+{
+ struct cgroup_value *ptr_cg_storage =
+ bpf_get_local_storage(&cgroup_storage, 0);
+
+ __sync_fetch_and_add(&ptr_cg_storage->ingress_pkts, 1);
+ __sync_fetch_and_add(&invocations, 1);
+
+ return 1;
+}
diff --git a/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c b/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c
index ec0165d07105..44ad46b33539 100644
--- a/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c
+++ b/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c
@@ -10,10 +10,12 @@
#include <linux/udp.h>
#include <bpf/bpf_helpers.h>
+#include "progs/cg_storage_multi.h"
+
struct {
__uint(type, BPF_MAP_TYPE_CGROUP_STORAGE);
__type(key, struct bpf_cgroup_storage_key);
- __type(value, __u32);
+ __type(value, struct cgroup_value);
} cgroup_storage SEC(".maps");
__u32 invocations = 0;
@@ -21,9 +23,10 @@ __u32 invocations = 0;
SEC("cgroup_skb/egress")
int egress(struct __sk_buff *skb)
{
- __u32 *ptr_cg_storage = bpf_get_local_storage(&cgroup_storage, 0);
+ struct cgroup_value *ptr_cg_storage =
+ bpf_get_local_storage(&cgroup_storage, 0);
- __sync_fetch_and_add(ptr_cg_storage, 1);
+ __sync_fetch_and_add(&ptr_cg_storage->egress_pkts, 1);
__sync_fetch_and_add(&invocations, 1);
return 1;
--
2.27.0
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup
2020-07-20 19:54 [PATCH v4 bpf-next 0/5] Make BPF CGROUP_STORAGE map usable by different programs at once YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 1/5] selftests/bpf: Add test for CGROUP_STORAGE map on multiple attaches YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 2/5] selftests/bpf: Test CGROUP_STORAGE map can't be used by multiple progs YiFei Zhu
@ 2020-07-20 19:54 ` YiFei Zhu
2020-07-21 18:05 ` Martin KaFai Lau
2020-07-20 19:54 ` [PATCH v4 bpf-next 4/5] selftests/bpf: Test CGROUP_STORAGE behavior on shared egress + ingress YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 5/5] Documentation/bpf: Document CGROUP_STORAGE map type YiFei Zhu
4 siblings, 1 reply; 13+ messages in thread
From: YiFei Zhu @ 2020-07-20 19:54 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Daniel Borkmann, Stanislav Fomichev,
Mahesh Bandewar, Roman Gushchin, Andrii Nakryiko,
Martin KaFai Lau, YiFei Zhu
From: YiFei Zhu <zhuyifei@google.com>
This change comes in several parts:
One, the restriction that the CGROUP_STORAGE map can only be used
by one program is removed. This results in the removal of the field
'aux' in struct bpf_cgroup_storage_map, and removal of relevant
code associated with the field, and removal of now-noop functions
bpf_free_cgroup_storage and bpf_cgroup_storage_release.
Second, because there could be multiple attach types to the same
cgroup, the attach type is completely ignored on comparison in
the map key. Newly added keys have it zeroed. The only value in
the key that still matters is the cgroup inode. bpftool map dump
will also show an attach type of zero.
Third, because the storages are now shared, the storages cannot
be unconditionally freed on program detach. There could be two
ways to solve this issue:
* A. Reference count the usage of the storages, and free when the
last program is detached.
* B. Free only when the storage is impossible to be referred to
again, i.e. when either the cgroup_bpf it is attached to, or
the map itself, is freed.
Option A has the side effect that, when the user detach and
reattach a program, whether the program gets a fresh storage
depends on whether there is another program attached using that
storage. This could trigger races if the user is multi-threaded,
and since nondeterminism in data races is evil, go with option B.
The both the map and the cgroup_bpf now tracks their associated
storages, and the storage unlink and free are removed from
cgroup_bpf_detach and added to cgroup_bpf_release and
cgroup_storage_map_free. The latter also new holds the cgroup_mutex
to prevent any races with the former.
Fourth, on attach, we reuse the old storage if the key already
exists in the map, via cgroup_storage_lookup. If the storage
does not exist yet, we create a new one, and publish it at the
last step in the attach process. This does not create a race
condition because for the whole attach the cgroup_mutex is held.
We keep track of an array of new storages that was allocated
and if the process fails only the new storages would get freed.
Signed-off-by: YiFei Zhu <zhuyifei@google.com>
---
include/linux/bpf-cgroup.h | 15 ++++---
include/uapi/linux/bpf.h | 2 +-
kernel/bpf/cgroup.c | 69 ++++++++++++++++++--------------
kernel/bpf/core.c | 12 ------
kernel/bpf/local_storage.c | 73 ++++++++++++----------------------
tools/include/uapi/linux/bpf.h | 2 +-
6 files changed, 76 insertions(+), 97 deletions(-)
diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 2c6f26670acc..2d5a04c0f4be 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -46,7 +46,8 @@ struct bpf_cgroup_storage {
};
struct bpf_cgroup_storage_map *map;
struct bpf_cgroup_storage_key key;
- struct list_head list;
+ struct list_head list_map;
+ struct list_head list_cg;
struct rb_node node;
struct rcu_head rcu;
};
@@ -78,6 +79,9 @@ struct cgroup_bpf {
struct list_head progs[MAX_BPF_ATTACH_TYPE];
u32 flags[MAX_BPF_ATTACH_TYPE];
+ /* list of cgroup shared storages */
+ struct list_head storages;
+
/* temp storage for effective prog array used by prog_attach/detach */
struct bpf_prog_array *inactive;
@@ -161,15 +165,16 @@ static inline void bpf_cgroup_storage_set(struct bpf_cgroup_storage
this_cpu_write(bpf_cgroup_storage[stype], storage[stype]);
}
+struct bpf_cgroup_storage *
+cgroup_storage_lookup(struct bpf_cgroup_storage_map *map,
+ struct bpf_cgroup_storage_key *key, bool locked);
struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog,
enum bpf_cgroup_storage_type stype);
void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage);
void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
- struct cgroup *cgroup,
- enum bpf_attach_type type);
+ struct cgroup *cgroup);
void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage);
int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux, struct bpf_map *map);
-void bpf_cgroup_storage_release(struct bpf_prog_aux *aux, struct bpf_map *map);
int bpf_percpu_cgroup_storage_copy(struct bpf_map *map, void *key, void *value);
int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
@@ -383,8 +388,6 @@ static inline void bpf_cgroup_storage_set(
struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE]) {}
static inline int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux,
struct bpf_map *map) { return 0; }
-static inline void bpf_cgroup_storage_release(struct bpf_prog_aux *aux,
- struct bpf_map *map) {}
static inline struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(
struct bpf_prog *prog, enum bpf_cgroup_storage_type stype) { return NULL; }
static inline void bpf_cgroup_storage_free(
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 54d0c886e3ba..db93a211d2b1 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -78,7 +78,7 @@ struct bpf_lpm_trie_key {
struct bpf_cgroup_storage_key {
__u64 cgroup_inode_id; /* cgroup inode id */
- __u32 attach_type; /* program attach type */
+ __u32 attach_type; /* program attach type, unused */
};
/* BPF syscall commands, see bpf(2) man-page for details. */
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index ac53102e244a..f91c554d6be6 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -37,17 +37,33 @@ static void bpf_cgroup_storages_free(struct bpf_cgroup_storage *storages[])
}
static int bpf_cgroup_storages_alloc(struct bpf_cgroup_storage *storages[],
- struct bpf_prog *prog)
+ struct bpf_cgroup_storage *new_storages[],
+ struct bpf_prog *prog,
+ struct cgroup *cgrp)
{
enum bpf_cgroup_storage_type stype;
+ struct bpf_cgroup_storage_key key;
+ struct bpf_map *map;
+
+ key.cgroup_inode_id = cgroup_id(cgrp);
+ key.attach_type = 0;
for_each_cgroup_storage_type(stype) {
+ map = prog->aux->cgroup_storage[stype];
+ if (!map)
+ continue;
+
+ storages[stype] = cgroup_storage_lookup((void *)map, &key, false);
+ if (storages[stype])
+ continue;
+
storages[stype] = bpf_cgroup_storage_alloc(prog, stype);
if (IS_ERR(storages[stype])) {
- storages[stype] = NULL;
- bpf_cgroup_storages_free(storages);
+ bpf_cgroup_storages_free(new_storages);
return -ENOMEM;
}
+
+ new_storages[stype] = storages[stype];
}
return 0;
@@ -63,21 +79,12 @@ static void bpf_cgroup_storages_assign(struct bpf_cgroup_storage *dst[],
}
static void bpf_cgroup_storages_link(struct bpf_cgroup_storage *storages[],
- struct cgroup* cgrp,
- enum bpf_attach_type attach_type)
-{
- enum bpf_cgroup_storage_type stype;
-
- for_each_cgroup_storage_type(stype)
- bpf_cgroup_storage_link(storages[stype], cgrp, attach_type);
-}
-
-static void bpf_cgroup_storages_unlink(struct bpf_cgroup_storage *storages[])
+ struct cgroup *cgrp)
{
enum bpf_cgroup_storage_type stype;
for_each_cgroup_storage_type(stype)
- bpf_cgroup_storage_unlink(storages[stype]);
+ bpf_cgroup_storage_link(storages[stype], cgrp);
}
/* Called when bpf_cgroup_link is auto-detached from dying cgroup.
@@ -101,22 +108,23 @@ static void cgroup_bpf_release(struct work_struct *work)
struct cgroup *p, *cgrp = container_of(work, struct cgroup,
bpf.release_work);
struct bpf_prog_array *old_array;
+ struct list_head *storages = &cgrp->bpf.storages;
+ struct bpf_cgroup_storage *storage, *stmp;
+
unsigned int type;
mutex_lock(&cgroup_mutex);
for (type = 0; type < ARRAY_SIZE(cgrp->bpf.progs); type++) {
struct list_head *progs = &cgrp->bpf.progs[type];
- struct bpf_prog_list *pl, *tmp;
+ struct bpf_prog_list *pl, *pltmp;
- list_for_each_entry_safe(pl, tmp, progs, node) {
+ list_for_each_entry_safe(pl, pltmp, progs, node) {
list_del(&pl->node);
if (pl->prog)
bpf_prog_put(pl->prog);
if (pl->link)
bpf_cgroup_link_auto_detach(pl->link);
- bpf_cgroup_storages_unlink(pl->storage);
- bpf_cgroup_storages_free(pl->storage);
kfree(pl);
static_branch_dec(&cgroup_bpf_enabled_key);
}
@@ -126,6 +134,11 @@ static void cgroup_bpf_release(struct work_struct *work)
bpf_prog_array_free(old_array);
}
+ list_for_each_entry_safe(storage, stmp, storages, list_cg) {
+ bpf_cgroup_storage_unlink(storage);
+ bpf_cgroup_storage_free(storage);
+ }
+
mutex_unlock(&cgroup_mutex);
for (p = cgroup_parent(cgrp); p; p = cgroup_parent(p))
@@ -290,6 +303,8 @@ int cgroup_bpf_inherit(struct cgroup *cgrp)
for (i = 0; i < NR; i++)
INIT_LIST_HEAD(&cgrp->bpf.progs[i]);
+ INIT_LIST_HEAD(&cgrp->bpf.storages);
+
for (i = 0; i < NR; i++)
if (compute_effective_progs(cgrp, i, &arrays[i]))
goto cleanup;
@@ -422,7 +437,7 @@ int __cgroup_bpf_attach(struct cgroup *cgrp,
struct list_head *progs = &cgrp->bpf.progs[type];
struct bpf_prog *old_prog = NULL;
struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {};
- struct bpf_cgroup_storage *old_storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {};
+ struct bpf_cgroup_storage *new_storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {};
struct bpf_prog_list *pl;
int err;
@@ -455,17 +470,16 @@ int __cgroup_bpf_attach(struct cgroup *cgrp,
if (IS_ERR(pl))
return PTR_ERR(pl);
- if (bpf_cgroup_storages_alloc(storage, prog ? : link->link.prog))
+ if (bpf_cgroup_storages_alloc(storage, new_storage,
+ prog ? : link->link.prog, cgrp))
return -ENOMEM;
if (pl) {
old_prog = pl->prog;
- bpf_cgroup_storages_unlink(pl->storage);
- bpf_cgroup_storages_assign(old_storage, pl->storage);
} else {
pl = kmalloc(sizeof(*pl), GFP_KERNEL);
if (!pl) {
- bpf_cgroup_storages_free(storage);
+ bpf_cgroup_storages_free(new_storage);
return -ENOMEM;
}
list_add_tail(&pl->node, progs);
@@ -480,12 +494,11 @@ int __cgroup_bpf_attach(struct cgroup *cgrp,
if (err)
goto cleanup;
- bpf_cgroup_storages_free(old_storage);
if (old_prog)
bpf_prog_put(old_prog);
else
static_branch_inc(&cgroup_bpf_enabled_key);
- bpf_cgroup_storages_link(pl->storage, cgrp, type);
+ bpf_cgroup_storages_link(new_storage, cgrp);
return 0;
cleanup:
@@ -493,9 +506,7 @@ int __cgroup_bpf_attach(struct cgroup *cgrp,
pl->prog = old_prog;
pl->link = NULL;
}
- bpf_cgroup_storages_free(pl->storage);
- bpf_cgroup_storages_assign(pl->storage, old_storage);
- bpf_cgroup_storages_link(pl->storage, cgrp, type);
+ bpf_cgroup_storages_free(new_storage);
if (!old_prog) {
list_del(&pl->node);
kfree(pl);
@@ -679,8 +690,6 @@ int __cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
/* now can actually delete it from this cgroup list */
list_del(&pl->node);
- bpf_cgroup_storages_unlink(pl->storage);
- bpf_cgroup_storages_free(pl->storage);
kfree(pl);
if (list_empty(progs))
/* last program was detached, reset flags to zero */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 7be02e555ab9..bde93344164d 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2097,24 +2097,12 @@ int bpf_prog_array_copy_info(struct bpf_prog_array *array,
: 0;
}
-static void bpf_free_cgroup_storage(struct bpf_prog_aux *aux)
-{
- enum bpf_cgroup_storage_type stype;
-
- for_each_cgroup_storage_type(stype) {
- if (!aux->cgroup_storage[stype])
- continue;
- bpf_cgroup_storage_release(aux, aux->cgroup_storage[stype]);
- }
-}
-
void __bpf_free_used_maps(struct bpf_prog_aux *aux,
struct bpf_map **used_maps, u32 len)
{
struct bpf_map *map;
u32 i;
- bpf_free_cgroup_storage(aux);
for (i = 0; i < len; i++) {
map = used_maps[i];
if (map->ops->map_poke_untrack)
diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index 51bd5a8cb01b..0b94b4ba99ba 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -9,6 +9,8 @@
#include <linux/slab.h>
#include <uapi/linux/btf.h>
+#include "../cgroup/cgroup-internal.h"
+
DEFINE_PER_CPU(struct bpf_cgroup_storage*, bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
#ifdef CONFIG_CGROUP_BPF
@@ -20,7 +22,6 @@ struct bpf_cgroup_storage_map {
struct bpf_map map;
spinlock_t lock;
- struct bpf_prog_aux *aux;
struct rb_root root;
struct list_head list;
};
@@ -38,16 +39,12 @@ static int bpf_cgroup_storage_key_cmp(
return -1;
else if (key1->cgroup_inode_id > key2->cgroup_inode_id)
return 1;
- else if (key1->attach_type < key2->attach_type)
- return -1;
- else if (key1->attach_type > key2->attach_type)
- return 1;
return 0;
}
-static struct bpf_cgroup_storage *cgroup_storage_lookup(
- struct bpf_cgroup_storage_map *map, struct bpf_cgroup_storage_key *key,
- bool locked)
+struct bpf_cgroup_storage *
+cgroup_storage_lookup(struct bpf_cgroup_storage_map *map,
+ struct bpf_cgroup_storage_key *key, bool locked)
{
struct rb_root *root = &map->root;
struct rb_node *node;
@@ -131,10 +128,7 @@ static int cgroup_storage_update_elem(struct bpf_map *map, void *_key,
struct bpf_cgroup_storage *storage;
struct bpf_storage_buffer *new;
- if (unlikely(flags & ~(BPF_F_LOCK | BPF_EXIST | BPF_NOEXIST)))
- return -EINVAL;
-
- if (unlikely(flags & BPF_NOEXIST))
+ if (unlikely(flags & ~(BPF_F_LOCK | BPF_EXIST)))
return -EINVAL;
if (unlikely((flags & BPF_F_LOCK) &&
@@ -250,16 +244,15 @@ static int cgroup_storage_get_next_key(struct bpf_map *_map, void *_key,
if (!storage)
goto enoent;
- storage = list_next_entry(storage, list);
+ storage = list_next_entry(storage, list_map);
if (!storage)
goto enoent;
} else {
storage = list_first_entry(&map->list,
- struct bpf_cgroup_storage, list);
+ struct bpf_cgroup_storage, list_map);
}
spin_unlock_bh(&map->lock);
- next->attach_type = storage->key.attach_type;
next->cgroup_inode_id = storage->key.cgroup_inode_id;
return 0;
@@ -318,6 +311,17 @@ static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
static void cgroup_storage_map_free(struct bpf_map *_map)
{
struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+ struct list_head *storages = &map->list;
+ struct bpf_cgroup_storage *storage, *stmp;
+
+ mutex_lock(&cgroup_mutex);
+
+ list_for_each_entry_safe(storage, stmp, storages, list_map) {
+ bpf_cgroup_storage_unlink(storage);
+ bpf_cgroup_storage_free(storage);
+ }
+
+ mutex_unlock(&cgroup_mutex);
WARN_ON(!RB_EMPTY_ROOT(&map->root));
WARN_ON(!list_empty(&map->list));
@@ -426,38 +430,13 @@ const struct bpf_map_ops cgroup_storage_map_ops = {
int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux, struct bpf_map *_map)
{
enum bpf_cgroup_storage_type stype = cgroup_storage_type(_map);
- struct bpf_cgroup_storage_map *map = map_to_storage(_map);
- int ret = -EBUSY;
-
- spin_lock_bh(&map->lock);
- if (map->aux && map->aux != aux)
- goto unlock;
if (aux->cgroup_storage[stype] &&
aux->cgroup_storage[stype] != _map)
- goto unlock;
+ return -EBUSY;
- map->aux = aux;
aux->cgroup_storage[stype] = _map;
- ret = 0;
-unlock:
- spin_unlock_bh(&map->lock);
-
- return ret;
-}
-
-void bpf_cgroup_storage_release(struct bpf_prog_aux *aux, struct bpf_map *_map)
-{
- enum bpf_cgroup_storage_type stype = cgroup_storage_type(_map);
- struct bpf_cgroup_storage_map *map = map_to_storage(_map);
-
- spin_lock_bh(&map->lock);
- if (map->aux == aux) {
- WARN_ON(aux->cgroup_storage[stype] != _map);
- map->aux = NULL;
- aux->cgroup_storage[stype] = NULL;
- }
- spin_unlock_bh(&map->lock);
+ return 0;
}
static size_t bpf_cgroup_storage_calculate_size(struct bpf_map *map, u32 *pages)
@@ -563,22 +542,21 @@ void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage)
}
void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
- struct cgroup *cgroup,
- enum bpf_attach_type type)
+ struct cgroup *cgroup)
{
struct bpf_cgroup_storage_map *map;
if (!storage)
return;
- storage->key.attach_type = type;
storage->key.cgroup_inode_id = cgroup_id(cgroup);
map = storage->map;
spin_lock_bh(&map->lock);
WARN_ON(cgroup_storage_insert(map, storage));
- list_add(&storage->list, &map->list);
+ list_add(&storage->list_map, &map->list);
+ list_add(&storage->list_cg, &cgroup->bpf.storages);
spin_unlock_bh(&map->lock);
}
@@ -596,7 +574,8 @@ void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage)
root = &map->root;
rb_erase(&storage->node, root);
- list_del(&storage->list);
+ list_del(&storage->list_map);
+ list_del(&storage->list_cg);
spin_unlock_bh(&map->lock);
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 54d0c886e3ba..db93a211d2b1 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -78,7 +78,7 @@ struct bpf_lpm_trie_key {
struct bpf_cgroup_storage_key {
__u64 cgroup_inode_id; /* cgroup inode id */
- __u32 attach_type; /* program attach type */
+ __u32 attach_type; /* program attach type, unused */
};
/* BPF syscall commands, see bpf(2) man-page for details. */
--
2.27.0
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH v4 bpf-next 4/5] selftests/bpf: Test CGROUP_STORAGE behavior on shared egress + ingress
2020-07-20 19:54 [PATCH v4 bpf-next 0/5] Make BPF CGROUP_STORAGE map usable by different programs at once YiFei Zhu
` (2 preceding siblings ...)
2020-07-20 19:54 ` [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup YiFei Zhu
@ 2020-07-20 19:54 ` YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 5/5] Documentation/bpf: Document CGROUP_STORAGE map type YiFei Zhu
4 siblings, 0 replies; 13+ messages in thread
From: YiFei Zhu @ 2020-07-20 19:54 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Daniel Borkmann, Stanislav Fomichev,
Mahesh Bandewar, Roman Gushchin, Andrii Nakryiko,
Martin KaFai Lau, YiFei Zhu
From: YiFei Zhu <zhuyifei@google.com>
This mirrors the original egress-only test. The cgroup_storage is
now extended to have two packet counters, one for egress and one
for ingress. The behavior of the counters are exactly the same as
the original egress-only test, only that the total number of
invocations doubles from having both egress and ingress being
counted.
The field attach_type in the map key is ignored in the kernel;
however, keeping it is pointless here and we are demonstrating the
expected usage of the map, so it is removed. That said, keeping the
field will not fail the test, for backwards compatibility reasons.
In other words, the original egress-only test is not affected by
the change in CGROUP_STORAGE behavior and will pass in both cases.
Signed-off-by: YiFei Zhu <zhuyifei@google.com>
---
.../bpf/prog_tests/cg_storage_multi.c | 90 +++++++++++++++++--
1 file changed, 83 insertions(+), 7 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c b/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
index 1f4ab437ddb9..aa2b448c4214 100644
--- a/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
+++ b/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c
@@ -28,7 +28,6 @@ static bool assert_storage(struct bpf_map *map, const char *cgroup_path,
map_fd = bpf_map__fd(map);
key.cgroup_inode_id = get_cgroup_id(cgroup_path);
- key.attach_type = BPF_CGROUP_INET_EGRESS;
if (CHECK(bpf_map_lookup_elem(map_fd, &key, &value) < 0,
"map-lookup", "errno %d", errno))
return true;
@@ -48,7 +47,6 @@ static bool assert_storage_noexist(struct bpf_map *map, const char *cgroup_path)
map_fd = bpf_map__fd(map);
key.cgroup_inode_id = get_cgroup_id(cgroup_path);
- key.attach_type = BPF_CGROUP_INET_EGRESS;
if (CHECK(bpf_map_lookup_elem(map_fd, &key, &value) == 0,
"map-lookup", "succeeded, expected ENOENT"))
return true;
@@ -156,14 +154,92 @@ static void test_egress_only(int parent_cgroup_fd, int child_cgroup_fd)
static void test_egress_ingress(int parent_cgroup_fd, int child_cgroup_fd)
{
struct cg_storage_multi_egress_ingress *obj;
+ struct cgroup_value expected_cgroup_value;
+ struct bpf_link *parent_egress_link = NULL, *parent_ingress_link = NULL;
+ struct bpf_link *child_egress_link = NULL, *child_ingress_link = NULL;
+ bool err;
- /* Cannot load both programs due to verifier failure:
- * "only one cgroup storage of each type is allowed"
- */
obj = cg_storage_multi_egress_ingress__open_and_load();
- if (CHECK(obj || errno != EBUSY,
- "skel-load", "errno %d, expected EBUSY", errno))
+ if (CHECK(!obj, "skel-load", "errno %d", errno))
return;
+
+ /* Attach to parent cgroup, trigger packet from child.
+ * Assert that there is two runs, one with parent cgroup egress and
+ * one with parent cgroup ingress.
+ * Also assert that child cgroup's storage does not exist
+ */
+ parent_egress_link = bpf_program__attach_cgroup(obj->progs.egress,
+ parent_cgroup_fd);
+ if (CHECK(IS_ERR(parent_egress_link), "parent-egress-cg-attach",
+ "err %ld", PTR_ERR(parent_egress_link)))
+ goto close_bpf_object;
+ parent_ingress_link = bpf_program__attach_cgroup(obj->progs.ingress,
+ parent_cgroup_fd);
+ if (CHECK(IS_ERR(parent_ingress_link), "parent-ingress-cg-attach",
+ "err %ld", PTR_ERR(parent_ingress_link)))
+ goto close_bpf_object;
+ err = connect_send(CHILD_CGROUP);
+ if (CHECK(err, "first-connect-send", "errno %d", errno))
+ goto close_bpf_object;
+ if (CHECK(obj->bss->invocations != 2,
+ "first-invoke", "invocations=%d", obj->bss->invocations))
+ goto close_bpf_object;
+ expected_cgroup_value = (struct cgroup_value) {
+ .egress_pkts = 1,
+ .ingress_pkts = 1,
+ };
+ if (assert_storage(obj->maps.cgroup_storage,
+ PARENT_CGROUP, &expected_cgroup_value))
+ goto close_bpf_object;
+ if (assert_storage_noexist(obj->maps.cgroup_storage, CHILD_CGROUP))
+ goto close_bpf_object;
+
+ /* Attach to parent and child cgroup, trigger packet from child.
+ * Assert that there is four additional runs, parent cgroup egress and
+ * ingress, child cgroup egress and ingress.
+ */
+ child_egress_link = bpf_program__attach_cgroup(obj->progs.egress,
+ child_cgroup_fd);
+ if (CHECK(IS_ERR(child_egress_link), "child-egress-cg-attach",
+ "err %ld", PTR_ERR(child_egress_link)))
+ goto close_bpf_object;
+ child_ingress_link = bpf_program__attach_cgroup(obj->progs.ingress,
+ child_cgroup_fd);
+ if (CHECK(IS_ERR(child_ingress_link), "child-ingress-cg-attach",
+ "err %ld", PTR_ERR(child_ingress_link)))
+ goto close_bpf_object;
+ err = connect_send(CHILD_CGROUP);
+ if (CHECK(err, "second-connect-send", "errno %d", errno))
+ goto close_bpf_object;
+ if (CHECK(obj->bss->invocations != 6,
+ "second-invoke", "invocations=%d", obj->bss->invocations))
+ goto close_bpf_object;
+ expected_cgroup_value = (struct cgroup_value) {
+ .egress_pkts = 2,
+ .ingress_pkts = 2,
+ };
+ if (assert_storage(obj->maps.cgroup_storage,
+ PARENT_CGROUP, &expected_cgroup_value))
+ goto close_bpf_object;
+ expected_cgroup_value = (struct cgroup_value) {
+ .egress_pkts = 1,
+ .ingress_pkts = 1,
+ };
+ if (assert_storage(obj->maps.cgroup_storage,
+ CHILD_CGROUP, &expected_cgroup_value))
+ goto close_bpf_object;
+
+close_bpf_object:
+ if (parent_egress_link)
+ bpf_link__destroy(parent_egress_link);
+ if (parent_ingress_link)
+ bpf_link__destroy(parent_ingress_link);
+ if (child_egress_link)
+ bpf_link__destroy(child_egress_link);
+ if (child_ingress_link)
+ bpf_link__destroy(child_ingress_link);
+
+ cg_storage_multi_egress_ingress__destroy(obj);
}
void test_cg_storage_multi(void)
--
2.27.0
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH v4 bpf-next 5/5] Documentation/bpf: Document CGROUP_STORAGE map type
2020-07-20 19:54 [PATCH v4 bpf-next 0/5] Make BPF CGROUP_STORAGE map usable by different programs at once YiFei Zhu
` (3 preceding siblings ...)
2020-07-20 19:54 ` [PATCH v4 bpf-next 4/5] selftests/bpf: Test CGROUP_STORAGE behavior on shared egress + ingress YiFei Zhu
@ 2020-07-20 19:54 ` YiFei Zhu
4 siblings, 0 replies; 13+ messages in thread
From: YiFei Zhu @ 2020-07-20 19:54 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Daniel Borkmann, Stanislav Fomichev,
Mahesh Bandewar, Roman Gushchin, Andrii Nakryiko,
Martin KaFai Lau, YiFei Zhu
From: YiFei Zhu <zhuyifei@google.com>
The machanics and usage are not very straightforward. Given the
changes it's better to document how it works and how to use it,
rather than having to rely on the examples and implementation to
infer what is going on.
Signed-off-by: YiFei Zhu <zhuyifei@google.com>
---
Documentation/bpf/index.rst | 9 +++
Documentation/bpf/map_cgroup_storage.rst | 95 ++++++++++++++++++++++++
2 files changed, 104 insertions(+)
create mode 100644 Documentation/bpf/map_cgroup_storage.rst
diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index 38b4db8be7a2..26f4bb3107fc 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst
@@ -48,6 +48,15 @@ Program types
bpf_lsm
+Map types
+=========
+
+.. toctree::
+ :maxdepth: 1
+
+ map_cgroup_storage
+
+
Testing and debugging BPF
=========================
diff --git a/Documentation/bpf/map_cgroup_storage.rst b/Documentation/bpf/map_cgroup_storage.rst
new file mode 100644
index 000000000000..b7210cb3f294
--- /dev/null
+++ b/Documentation/bpf/map_cgroup_storage.rst
@@ -0,0 +1,95 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+.. Copyright (C) 2020 Google LLC.
+
+===========================
+BPF_MAP_TYPE_CGROUP_STORAGE
+===========================
+
+The ``BPF_MAP_TYPE_CGROUP_STORAGE`` map type represents a local fix-sized
+storage. It is only available with ``CONFIG_CGROUP_BPF``, and to programs that
+attach to cgroups; the programs are made available by the same config. The
+storage is identified by the cgroup the program is attached to.
+
+This document describes the usage and semantics of the
+``BPF_MAP_TYPE_CGROUP_STORAGE`` map type. Some of its behaviors was changed in
+Linux 5.9 and this document will describe the differences.
+
+Usage
+=====
+
+The map uses key of type ``struct bpf_cgroup_storage_key``, declared in
+``linux/bpf.h``::
+
+ struct bpf_cgroup_storage_key {
+ __u64 cgroup_inode_id;
+ __u32 attach_type;
+ };
+
+``cgroup_inode_id`` is the inode id of the cgroup directory.
+``attach_type`` was the the program's attach type prior to Linux 5.9, since 5.9
+it is ignored and kept for backwards compatibility.
+
+To access the storage in a program, use ``bpf_get_local_storage``::
+
+ void *bpf_get_local_storage(void *map, u64 flags)
+
+``flags`` is reserved for future use and must be 0.
+
+There is no implicit synchronization. Storages of ``BPF_MAP_TYPE_CGROUP_STORAGE``
+can be accessed by multiple programs across different CPUs, and user should
+take care of synchronization by themselves.
+
+Example usage::
+
+ #include <linux/bpf.h>
+
+ struct {
+ __uint(type, BPF_MAP_TYPE_CGROUP_STORAGE);
+ __type(key, struct bpf_cgroup_storage_key);
+ __type(value, __u32);
+ } cgroup_storage SEC(".maps");
+
+ int program(struct __sk_buff *skb)
+ {
+ __u32 *ptr = bpf_get_local_storage(&cgroup_storage, 0);
+ __sync_fetch_and_add(ptr_cg_storage-, 1);
+
+ return 0;
+ }
+
+Semantics
+=========
+
+``BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE`` is a variant of this map type. This
+per-CPU variant will have different memory regions for each CPU for each
+storage. The non-per-CPU will have the same memory region for each storage.
+
+Prior to Linux 5.9, the lifetime of a storage is precisely per-attachment, and
+for a single ``CGROUP_STORAGE`` map, there can be at most one program loaded
+that uses the map. A program may be attached to multiple cgroups or have
+multiple attach types, and each attach creates a fresh zeroed storage. The
+storage is freed upon detach.
+
+Userspace may use the the attach parameters of cgroup and attach type pair
+in ``struct bpf_cgroup_storage_key`` as the key to the BPF map APIs to read or
+update the storage for a given attachment.
+
+Since Linux 5.9, storage can be shared by multiple programs, and attach type
+is ignored. When a program is attached to a cgroup, the kernel would create a
+new storage only if the map does not already contain an entry for the cgroup,
+or else the old storage is reused for the new attachment. Storage is freed
+only when either the map or the cgroup attached to is being freed. Detaching
+will not directly free the storage, but it may cause the reference to the map
+to reach zero and indirectly freeing all storage in the map.
+
+Userspace may use the the attach parameters of cgroup only in
+``struct bpf_cgroup_storage_key`` as the key to the BPF map APIs to read or
+update the storage for a given attachment. The struct also contains an
+``attach_type`` field; this field is ignored.
+
+In all versions, the storage is bound at attach time. Even if the program is
+attached to parent and triggers in child, the storage still belongs to the
+parent.
+
+Userspace cannot create a new entry in the map or delete an existing entry.
+Program test runs always use a temporary storage.
--
2.27.0
^ permalink raw reply related [flat|nested] 13+ messages in thread
* Re: [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup
2020-07-20 19:54 ` [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup YiFei Zhu
@ 2020-07-21 18:05 ` Martin KaFai Lau
2020-07-21 21:20 ` YiFei Zhu
0 siblings, 1 reply; 13+ messages in thread
From: Martin KaFai Lau @ 2020-07-21 18:05 UTC (permalink / raw)
To: YiFei Zhu
Cc: bpf, Alexei Starovoitov, Daniel Borkmann, Stanislav Fomichev,
Mahesh Bandewar, Roman Gushchin, Andrii Nakryiko, YiFei Zhu
On Mon, Jul 20, 2020 at 02:54:53PM -0500, YiFei Zhu wrote:
> From: YiFei Zhu <zhuyifei@google.com>
>
> This change comes in several parts:
>
> One, the restriction that the CGROUP_STORAGE map can only be used
> by one program is removed. This results in the removal of the field
> 'aux' in struct bpf_cgroup_storage_map, and removal of relevant
> code associated with the field, and removal of now-noop functions
> bpf_free_cgroup_storage and bpf_cgroup_storage_release.
>
> Second, because there could be multiple attach types to the same
> cgroup, the attach type is completely ignored on comparison in
> the map key. Newly added keys have it zeroed. The only value in
> the key that still matters is the cgroup inode. bpftool map dump
> will also show an attach type of zero.
I quickly checked zero is actually BPF_CGROUP_INET_INGRESS instead
of UNSPEC for attach_type. It will be confusing on the syscall
side. e.g. map dumping with key.attach_type == BPF_CGROUP_INET_INGRESS
while the only cgroup program is actually attaching to BPF_CGROUP_INET_EGRESS.
I don't have a clean way out for this. Adding a non-zero UNSPEC
to "enum bpf_attach_type" seems wrong also.
One possible way out is to allow the bpf_cgroup_storage_map
to have a smaller key size (i.e. allow both sizeof(cgroup_inode_id)
and the existing sizeof(struct bpf_cgroup_storage_key). That
will completely remove attach_type from the picture if the user
specified to use sizeof(cgroup_inode_id) as the key_size.
If sizeof(struct bpf_cgroup_storage_key) is specified, the attach_type
is still used in cmp().
The bpf_cgroup_storage_key_cmp() need to do cmp accordingly.
Same changes is needed to lookup_elem, delete_elem, check_btf, map_alloc...etc.
[ ... ]
> diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
> index 51bd5a8cb01b..0b94b4ba99ba 100644
> --- a/kernel/bpf/local_storage.c
> +++ b/kernel/bpf/local_storage.c
> @@ -9,6 +9,8 @@
> #include <linux/slab.h>
> #include <uapi/linux/btf.h>
>
> +#include "../cgroup/cgroup-internal.h"
Why?
Others LGTM.
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup
2020-07-21 18:05 ` Martin KaFai Lau
@ 2020-07-21 21:20 ` YiFei Zhu
2020-07-21 22:41 ` Martin KaFai Lau
0 siblings, 1 reply; 13+ messages in thread
From: YiFei Zhu @ 2020-07-21 21:20 UTC (permalink / raw)
To: Martin KaFai Lau
Cc: YiFei Zhu, bpf, Alexei Starovoitov, Daniel Borkmann,
Stanislav Fomichev, Mahesh Bandewar, Roman Gushchin,
Andrii Nakryiko
On Tue, Jul 21, 2020 at 1:05 PM Martin KaFai Lau <kafai@fb.com> wrote:
> I quickly checked zero is actually BPF_CGROUP_INET_INGRESS instead
> of UNSPEC for attach_type. It will be confusing on the syscall
> side. e.g. map dumping with key.attach_type == BPF_CGROUP_INET_INGRESS
> while the only cgroup program is actually attaching to BPF_CGROUP_INET_EGRESS.
>
> I don't have a clean way out for this. Adding a non-zero UNSPEC
> to "enum bpf_attach_type" seems wrong also.
> One possible way out is to allow the bpf_cgroup_storage_map
> to have a smaller key size (i.e. allow both sizeof(cgroup_inode_id)
> and the existing sizeof(struct bpf_cgroup_storage_key). That
> will completely remove attach_type from the picture if the user
> specified to use sizeof(cgroup_inode_id) as the key_size.
> If sizeof(struct bpf_cgroup_storage_key) is specified, the attach_type
> is still used in cmp().
>
> The bpf_cgroup_storage_key_cmp() need to do cmp accordingly.
> Same changes is needed to lookup_elem, delete_elem, check_btf, map_alloc...etc.
ACK. Considering that the cgroup_inode_id is the first field of struct
bpf_cgroup_storage_key, I can probably just use this fact and directly
use the user-provided map key (after it's copied to kernel space) and
cast the pointer to a __u64 - or are there any architectures where the
first field is not at offset zero? If this is done then we can change
all the kernel internal APIs to use __u64 cgroup_inode_id, ignoring
the existence of the struct aside from the map creation (size checking
and BTF checking).
> > +#include "../cgroup/cgroup-internal.h"
> Why?
cgroup_mutex is declared in this header.
YiFei Zhu
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup
2020-07-21 21:20 ` YiFei Zhu
@ 2020-07-21 22:41 ` Martin KaFai Lau
2020-07-21 22:56 ` sdf
0 siblings, 1 reply; 13+ messages in thread
From: Martin KaFai Lau @ 2020-07-21 22:41 UTC (permalink / raw)
To: YiFei Zhu
Cc: YiFei Zhu, bpf, Alexei Starovoitov, Daniel Borkmann,
Stanislav Fomichev, Mahesh Bandewar, Roman Gushchin,
Andrii Nakryiko
On Tue, Jul 21, 2020 at 04:20:00PM -0500, YiFei Zhu wrote:
> On Tue, Jul 21, 2020 at 1:05 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > I quickly checked zero is actually BPF_CGROUP_INET_INGRESS instead
> > of UNSPEC for attach_type. It will be confusing on the syscall
> > side. e.g. map dumping with key.attach_type == BPF_CGROUP_INET_INGRESS
> > while the only cgroup program is actually attaching to BPF_CGROUP_INET_EGRESS.
> >
> > I don't have a clean way out for this. Adding a non-zero UNSPEC
> > to "enum bpf_attach_type" seems wrong also.
> > One possible way out is to allow the bpf_cgroup_storage_map
> > to have a smaller key size (i.e. allow both sizeof(cgroup_inode_id)
> > and the existing sizeof(struct bpf_cgroup_storage_key). That
> > will completely remove attach_type from the picture if the user
> > specified to use sizeof(cgroup_inode_id) as the key_size.
> > If sizeof(struct bpf_cgroup_storage_key) is specified, the attach_type
> > is still used in cmp().
> >
> > The bpf_cgroup_storage_key_cmp() need to do cmp accordingly.
> > Same changes is needed to lookup_elem, delete_elem, check_btf, map_alloc...etc.
>
> ACK. Considering that the cgroup_inode_id is the first field of struct
> bpf_cgroup_storage_key, I can probably just use this fact and directly
> use the user-provided map key (after it's copied to kernel space) and
> cast the pointer to a __u64 - or are there any architectures where the
> first field is not at offset zero? If this is done then we can change
> all the kernel internal APIs to use __u64 cgroup_inode_id, ignoring
> the existence of the struct aside from the map creation (size checking
> and BTF checking).
Just to be clear. The problem is the userspace is expecting
the whole key (cgroup_id, attach_type) to be meaningful and
we cannot stop supporting this existing key type now.
This patch essentially sets all attach_type to 0 to mean unused/UNSPEC/dont_care
but 0 is actually BPF_CGROUP_INET_INGRESS in bpf's uapi. "map dump" will be an
issue as mentioned earlier. Also, as a key of a map,
it is logical for the user to assume that different attach_type will have
different storage. e.g. If user lookup by (cgroup_id, 1), what does it mean
to quietly return the storage created by (cgroup_id, 0/2/3/4/5)?
I think from the map's perspective, it makes more sense to
have different "key-cmp" operation for different key type. When the map
is created with key_size == (cgroup_id, attach_type), the "cmp"
will stay as is to compare the attach_type also. Then the
storage will be sharable among the same cgroup and the
same attach_type.
Then add support for the new key_size == (cgroup_id) which the "cmp" will
only compare the "cgroup_id" as this patch does so that the storage can be
shared among all attach_types of the same cgroup.
Does it make sense?
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup
2020-07-21 22:41 ` Martin KaFai Lau
@ 2020-07-21 22:56 ` sdf
2020-07-22 0:09 ` Martin KaFai Lau
0 siblings, 1 reply; 13+ messages in thread
From: sdf @ 2020-07-21 22:56 UTC (permalink / raw)
To: Martin KaFai Lau
Cc: YiFei Zhu, YiFei Zhu, bpf, Alexei Starovoitov, Daniel Borkmann,
Mahesh Bandewar, Roman Gushchin, Andrii Nakryiko
On 07/21, Martin KaFai Lau wrote:
> On Tue, Jul 21, 2020 at 04:20:00PM -0500, YiFei Zhu wrote:
> > On Tue, Jul 21, 2020 at 1:05 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > I quickly checked zero is actually BPF_CGROUP_INET_INGRESS instead
> > > of UNSPEC for attach_type. It will be confusing on the syscall
> > > side. e.g. map dumping with key.attach_type == BPF_CGROUP_INET_INGRESS
> > > while the only cgroup program is actually attaching to
> BPF_CGROUP_INET_EGRESS.
> > >
> > > I don't have a clean way out for this. Adding a non-zero UNSPEC
> > > to "enum bpf_attach_type" seems wrong also.
> > > One possible way out is to allow the bpf_cgroup_storage_map
> > > to have a smaller key size (i.e. allow both sizeof(cgroup_inode_id)
> > > and the existing sizeof(struct bpf_cgroup_storage_key). That
> > > will completely remove attach_type from the picture if the user
> > > specified to use sizeof(cgroup_inode_id) as the key_size.
> > > If sizeof(struct bpf_cgroup_storage_key) is specified, the attach_type
> > > is still used in cmp().
> > >
> > > The bpf_cgroup_storage_key_cmp() need to do cmp accordingly.
> > > Same changes is needed to lookup_elem, delete_elem, check_btf,
> map_alloc...etc.
> >
> > ACK. Considering that the cgroup_inode_id is the first field of struct
> > bpf_cgroup_storage_key, I can probably just use this fact and directly
> > use the user-provided map key (after it's copied to kernel space) and
> > cast the pointer to a __u64 - or are there any architectures where the
> > first field is not at offset zero? If this is done then we can change
> > all the kernel internal APIs to use __u64 cgroup_inode_id, ignoring
> > the existence of the struct aside from the map creation (size checking
> > and BTF checking).
> Just to be clear. The problem is the userspace is expecting
> the whole key (cgroup_id, attach_type) to be meaningful and
> we cannot stop supporting this existing key type now.
To step back a bit. I think in the commit message we mentioned that
attach_type is essentially (mostly) meaningless right now.
If I want to share cgroup storage between BPF_CGROUP_INET_INGRESS and
BPF_CGROUP_INET_EGRESS, the verifier will refuse to load those programs.
So doing lookup with different attach_type for the same storage
shouldn't really happen.
Except. There is one use-case where it does make sense. If you take
the same loaded program and attach it to both ingress and egress, each
one will get a separate storage copy. And only in this case
attach_type really has any meaning.
But since more and more attach types started to require
expected_attach_type, it seems that the case where the same
prog is attached to two different hooks should be almost
non-existent. That's why we've decided to go with
the idea of completely ignoring it.
So the question is: is it really worth it trying to preserve
that obscure use-case (and have more complex implementation) or we can
safely assume that nobody is doing that sort of thing in the wild (and
can simplify the internal logic a bit)?
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup
2020-07-21 22:56 ` sdf
@ 2020-07-22 0:09 ` Martin KaFai Lau
2020-07-22 0:19 ` YiFei Zhu
0 siblings, 1 reply; 13+ messages in thread
From: Martin KaFai Lau @ 2020-07-22 0:09 UTC (permalink / raw)
To: sdf
Cc: YiFei Zhu, YiFei Zhu, bpf, Alexei Starovoitov, Daniel Borkmann,
Mahesh Bandewar, Roman Gushchin, Andrii Nakryiko
On Tue, Jul 21, 2020 at 03:56:36PM -0700, sdf@google.com wrote:
> On 07/21, Martin KaFai Lau wrote:
> > On Tue, Jul 21, 2020 at 04:20:00PM -0500, YiFei Zhu wrote:
> > > On Tue, Jul 21, 2020 at 1:05 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > I quickly checked zero is actually BPF_CGROUP_INET_INGRESS instead
> > > > of UNSPEC for attach_type. It will be confusing on the syscall
> > > > side. e.g. map dumping with key.attach_type == BPF_CGROUP_INET_INGRESS
> > > > while the only cgroup program is actually attaching to
> > BPF_CGROUP_INET_EGRESS.
> > > >
> > > > I don't have a clean way out for this. Adding a non-zero UNSPEC
> > > > to "enum bpf_attach_type" seems wrong also.
> > > > One possible way out is to allow the bpf_cgroup_storage_map
> > > > to have a smaller key size (i.e. allow both sizeof(cgroup_inode_id)
> > > > and the existing sizeof(struct bpf_cgroup_storage_key). That
> > > > will completely remove attach_type from the picture if the user
> > > > specified to use sizeof(cgroup_inode_id) as the key_size.
> > > > If sizeof(struct bpf_cgroup_storage_key) is specified, the attach_type
> > > > is still used in cmp().
> > > >
> > > > The bpf_cgroup_storage_key_cmp() need to do cmp accordingly.
> > > > Same changes is needed to lookup_elem, delete_elem, check_btf,
> > map_alloc...etc.
> > >
> > > ACK. Considering that the cgroup_inode_id is the first field of struct
> > > bpf_cgroup_storage_key, I can probably just use this fact and directly
> > > use the user-provided map key (after it's copied to kernel space) and
> > > cast the pointer to a __u64 - or are there any architectures where the
> > > first field is not at offset zero? If this is done then we can change
> > > all the kernel internal APIs to use __u64 cgroup_inode_id, ignoring
> > > the existence of the struct aside from the map creation (size checking
> > > and BTF checking).
> > Just to be clear. The problem is the userspace is expecting
> > the whole key (cgroup_id, attach_type) to be meaningful and
> > we cannot stop supporting this existing key type now.
> To step back a bit. I think in the commit message we mentioned that
> attach_type is essentially (mostly) meaningless right now.
> If I want to share cgroup storage between BPF_CGROUP_INET_INGRESS and
> BPF_CGROUP_INET_EGRESS, the verifier will refuse to load those programs.
> So doing lookup with different attach_type for the same storage
> shouldn't really happen.
I think we are talking about the existing map->aux check in
bpf_cgroup_storage_assign()? Right, the map is dedicated for
only one bpf prog which usually has only one expected_attach_type.
Thus, the attach_type of the key is not really useful since it will
always be the same. However, it does not mean the exposed
attach_type (of the key) is meaningless or the value is invalid.
The exposed value is valid.
I am trying to say attach_type is still part of the key
and exposed to userspace (e.g. in map dump) but it is sort of
invalid after this change because I am not sure what that "0"
means now.
Also, as part of the key, it is intuitive for user to think the storage is
unique per (cgroup, attach_type). This uniqueness is always true now because
of the map->aux logic and guaranteed by the verifier. With this patch, this
"key" intuition is gone where the kernel quietly ignore the attach_type.
>
> Except. There is one use-case where it does make sense. If you take
> the same loaded program and attach it to both ingress and egress, each
> one will get a separate storage copy. And only in this case
> attach_type really has any meaning.
>
> But since more and more attach types started to require
> expected_attach_type, it seems that the case where the same
> prog is attached to two different hooks should be almost
> non-existent. That's why we've decided to go with
> the idea of completely ignoring it.
>
> So the question is: is it really worth it trying to preserve
> that obscure use-case (and have more complex implementation) or we can
> safely assume that nobody is doing that sort of thing in the wild (and
> can simplify the internal logic a bit)?
I think it is a reasonable expectation for map-dump to show a
meaningful attach_type if it is indeed part of the key.
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup
2020-07-22 0:09 ` Martin KaFai Lau
@ 2020-07-22 0:19 ` YiFei Zhu
2020-07-22 0:49 ` Martin KaFai Lau
0 siblings, 1 reply; 13+ messages in thread
From: YiFei Zhu @ 2020-07-22 0:19 UTC (permalink / raw)
To: Martin KaFai Lau
Cc: Stanislav Fomichev, YiFei Zhu, bpf, Alexei Starovoitov,
Daniel Borkmann, Mahesh Bandewar, Roman Gushchin,
Andrii Nakryiko
On Tue, Jul 21, 2020 at 7:09 PM Martin KaFai Lau <kafai@fb.com> wrote:
> I think we are talking about the existing map->aux check in
> bpf_cgroup_storage_assign()? Right, the map is dedicated for
> only one bpf prog which usually has only one expected_attach_type.
> Thus, the attach_type of the key is not really useful since it will
> always be the same. However, it does not mean the exposed
> attach_type (of the key) is meaningless or the value is invalid.
> The exposed value is valid.
>
> I am trying to say attach_type is still part of the key
> and exposed to userspace (e.g. in map dump) but it is sort of
> invalid after this change because I am not sure what that "0"
> means now.
>
> Also, as part of the key, it is intuitive for user to think the storage is
> unique per (cgroup, attach_type). This uniqueness is always true now because
> of the map->aux logic and guaranteed by the verifier. With this patch, this
> "key" intuition is gone where the kernel quietly ignore the attach_type.
Right. It is indeed non-intuitive for part of the "key" to be
completely ignored in cmp. However, what would a sane solution be
instead? I could at attach time, use the attach type to also perform
the lookup, and store the attach type as the key, if and only if the
size of the key == sizeof(struct cgroup_storage_key). This storage
will not be shared across different attach types, only across
different programs of the same attach type. The lifetime will still
bound to the (map, cgroup_bpf) pair, rather than the program, as the
implementation prior to this patch did.
YiFei Zhu
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup
2020-07-22 0:19 ` YiFei Zhu
@ 2020-07-22 0:49 ` Martin KaFai Lau
0 siblings, 0 replies; 13+ messages in thread
From: Martin KaFai Lau @ 2020-07-22 0:49 UTC (permalink / raw)
To: YiFei Zhu
Cc: Stanislav Fomichev, YiFei Zhu, bpf, Alexei Starovoitov,
Daniel Borkmann, Mahesh Bandewar, Roman Gushchin,
Andrii Nakryiko
On Tue, Jul 21, 2020 at 07:19:31PM -0500, YiFei Zhu wrote:
> On Tue, Jul 21, 2020 at 7:09 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > I think we are talking about the existing map->aux check in
> > bpf_cgroup_storage_assign()? Right, the map is dedicated for
> > only one bpf prog which usually has only one expected_attach_type.
> > Thus, the attach_type of the key is not really useful since it will
> > always be the same. However, it does not mean the exposed
> > attach_type (of the key) is meaningless or the value is invalid.
> > The exposed value is valid.
> >
> > I am trying to say attach_type is still part of the key
> > and exposed to userspace (e.g. in map dump) but it is sort of
> > invalid after this change because I am not sure what that "0"
> > means now.
> >
> > Also, as part of the key, it is intuitive for user to think the storage is
> > unique per (cgroup, attach_type). This uniqueness is always true now because
> > of the map->aux logic and guaranteed by the verifier. With this patch, this
> > "key" intuition is gone where the kernel quietly ignore the attach_type.
>
> Right. It is indeed non-intuitive for part of the "key" to be
> completely ignored in cmp. However, what would a sane solution be
> instead? I could at attach time, use the attach type to also perform
> the lookup, and store the attach type as the key, if and only if the
> size of the key == sizeof(struct cgroup_storage_key).
Yes, that makes sense. cgroup_storage_lookup() has the map which
has the key_size, so it can decide which part of the key to use
for lookup. bpf_cgroup_storages_alloc() does not need to know
the details and it just populates everything in bpf_cgroup_storage_key
and let cgroup_storage_lookup() to decide.
Thus, it should not be a big change on this patch.
> This storage
> will not be shared across different attach types, only across
> different programs of the same attach type. The lifetime will still
> bound to the (map, cgroup_bpf) pair, rather than the program, as the
> implementation prior to this patch did.
Right, the lifetime of the storage should be the same regardless of the key.
The major idea of this patch is to make storage sharable across
different bpf-progs and this part does not change.
How sharable is defined by the map's key.
The key of the map should behave like a normal map's key.
sharable among (cgroup_id, attach_type) or
sharable among (cgroup_id)
Then all lookup/update/map-dump will behave like a normal
map without an invalid value "0" (BPF_CGROUP_INET_INGRESS) in the attach_type.
Thus, I don't expect a big change in this patch.
May be restoring the original bpf_cgroup_storage_key_cmp() behavior
and a few key_size check in the map_ops's lookup/update/check_btf...etc.
^ permalink raw reply [flat|nested] 13+ messages in thread
end of thread, other threads:[~2020-07-22 0:49 UTC | newest]
Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-20 19:54 [PATCH v4 bpf-next 0/5] Make BPF CGROUP_STORAGE map usable by different programs at once YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 1/5] selftests/bpf: Add test for CGROUP_STORAGE map on multiple attaches YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 2/5] selftests/bpf: Test CGROUP_STORAGE map can't be used by multiple progs YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 3/5] bpf: Make cgroup storages shared across attaches on the same cgroup YiFei Zhu
2020-07-21 18:05 ` Martin KaFai Lau
2020-07-21 21:20 ` YiFei Zhu
2020-07-21 22:41 ` Martin KaFai Lau
2020-07-21 22:56 ` sdf
2020-07-22 0:09 ` Martin KaFai Lau
2020-07-22 0:19 ` YiFei Zhu
2020-07-22 0:49 ` Martin KaFai Lau
2020-07-20 19:54 ` [PATCH v4 bpf-next 4/5] selftests/bpf: Test CGROUP_STORAGE behavior on shared egress + ingress YiFei Zhu
2020-07-20 19:54 ` [PATCH v4 bpf-next 5/5] Documentation/bpf: Document CGROUP_STORAGE map type YiFei Zhu
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