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Date: Fri, 26 Apr 2019 21:16:19 +0000
From: Martin Lau <kafai@...com>
To: Stanislav Fomichev <sdf@...ichev.me>
CC: "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Alexei Starovoitov <ast@...com>,
Andrii Nakryiko <andriin@...com>,
Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>,
Kernel Team <Kernel-team@...com>, Yonghong Song <yhs@...com>
Subject: Re: [PATCH v3 bpf-next 1/6] bpf: Introduce bpf sk local storage
On Fri, Apr 26, 2019 at 10:52:20AM -0700, Stanislav Fomichev wrote:
> On 04/26, Martin KaFai Lau wrote:
> > After allowing a bpf prog to
> > - directly read the skb->sk ptr
> > - get the fullsock bpf_sock by "bpf_sk_fullsock()"
> > - get the bpf_tcp_sock by "bpf_tcp_sock()"
> > - get the listener sock by "bpf_get_listener_sock()"
> > - avoid duplicating the fields of "(bpf_)sock" and "(bpf_)tcp_sock"
> > into different bpf running context.
> >
> > this patch is another effort to make bpf's network programming
> > more intuitive to do (together with memory and performance benefit).
> >
> > When bpf prog needs to store data for a sk, the current practice is to
> > define a map with the usual 4-tuples (src/dst ip/port) as the key.
> > If multiple bpf progs require to store different sk data, multiple maps
> > have to be defined. Hence, wasting memory to store the duplicated
> > keys (i.e. 4 tuples here) in each of the bpf map.
> > [ The smallest key could be the sk pointer itself which requires
> > some enhancement in the verifier and it is a separate topic. ]
> >
> > Also, the bpf prog needs to clean up the elem when sk is freed.
> > Otherwise, the bpf map will become full and un-usable quickly.
> > The sk-free tracking currently could be done during sk state
> > transition (e.g. BPF_SOCK_OPS_STATE_CB).
> >
> > The size of the map needs to be predefined which then usually ended-up
> > with an over-provisioned map in production. Even the map was re-sizable,
> > while the sk naturally come and go away already, this potential re-size
> > operation is arguably redundant if the data can be directly connected
> > to the sk itself instead of proxy-ing through a bpf map.
> >
> > This patch introduces sk->sk_bpf_storage to provide local storage space
> > at sk for bpf prog to use. The space will be allocated when the first bpf
> > prog has created data for this particular sk.
> >
> > The design optimizes the bpf prog's lookup (and then optionally followed by
> > an inline update). bpf_spin_lock should be used if the inline update needs
> > to be protected.
> >
> > BPF_MAP_TYPE_SK_STORAGE:
> > -----------------------
> > To define a bpf "sk-local-storage", a BPF_MAP_TYPE_SK_STORAGE map (new in
> > this patch) needs to be created. Multiple BPF_MAP_TYPE_SK_STORAGE maps can
> > be created to fit different bpf progs' needs. The map enforces
> > BTF to allow printing the sk-local-storage during a system-wise
> > sk dump (e.g. "ss -ta") in the future.
> >
> > The purpose of a BPF_MAP_TYPE_SK_STORAGE map is not for lookup/update/delete
> > a "sk-local-storage" data from a particular sk.
> > Think of the map as a meta-data (or "type") of a "sk-local-storage". This
> > particular "type" of "sk-local-storage" data can then be stored in any sk.
> >
> > The main purposes of this map are mostly:
> > 1. Define the size of a "sk-local-storage" type.
> > 2. Provide a similar syscall userspace API as the map (e.g. lookup/update,
> > map-id, map-btf...etc.)
> > 3. Keep track of all sk's storages of this "type" and clean them up
> > when the map is freed.
> >
> > sk->sk_bpf_storage:
> > ------------------
> > The main lookup/update/delete is done on sk->sk_bpf_storage (which
> > is a "struct bpf_sk_storage"). When doing a lookup,
> > the "map" pointer is now used as the "key" to search on the
> > sk_storage->list. The "map" pointer is actually serving
> > as the "type" of the "sk-local-storage" that is being
> > requested.
> >
> > To allow very fast lookup, it should be as fast as looking up an
> > array at a stable-offset. At the same time, it is not ideal to
> > set a hard limit on the number of sk-local-storage "type" that the
> > system can have. Hence, this patch takes a cache approach.
> > The last search result from sk_storage->list is cached in
> > sk_storage->cache[] which is a stable sized array. Each
> > "sk-local-storage" type has a stable offset to the cache[] array.
> > In the future, a map's flag could be introduced to do cache
> > opt-out/enforcement if it became necessary.
> >
> > All data will be removed from sk->sk_bpf_storage during
> > sk destruction.
> >
> > bpf_sk_storage_get() and bpf_sk_storage_delete():
> > ------------------------------------------------
> > Instead of using bpf_map_(lookup|update|delete)_elem(),
> > the bpf prog needs to use the new helper bpf_sk_storage_get() and
> > bpf_sk_storage_delete(). The verifier can then enforce the
> > ARG_PTR_TO_SOCKET argument. The bpf_sk_storage_get() also allows to
> > "create" new elem if one does not exist in the sk. It is done by
> > the new BPF_SK_STORAGE_GET_F_CREATE flag. An optional value can also be
> > provided as the initial value during BPF_SK_STORAGE_GET_F_CREATE.
> > The BPF_MAP_TYPE_SK_STORAGE also supports bpf_spin_lock. Together,
> > it has eliminated the potential use cases for an equivalent
> > bpf_map_update_elem() API (for bpf_prog) in this patch.
> >
> > Misc notes:
> > ----------
> > 1. map_get_next_key is not supported. From the userspace syscall
> > perspective, the map has the socket fd as the key while the map
> > can be shared by pinned-file or map-id.
> >
> > Since btf is enforced, the existing "ss" could be enhanced to pretty
> > print the local-storage.
> >
> > Supporting a kernel defined btf with 4 tuples as the return key could
> > be explored later also.
> >
> > 2. The sk->sk_lock cannot be acquired. Atomic operations is used instead.
> > e.g. cmpxchg is done on the sk->sk_bpf_storage ptr.
> > Please refer to the source code comments for the details in
> > synchronization cases and considerations.
> >
> > 3. The mem is charged to the sk->sk_omem_alloc as the sk filter does.
> >
> > Benchmark:
> > ---------
> > Here is the benchmark data collected by turning on
> > the "kernel.bpf_stats_enabled" sysctl.
> > Two bpf progs are tested:
> >
> > One bpf prog with the usual bpf hashmap (max_entries = 8192) with the
> > sk ptr as the key. (verifier is modified to support sk ptr as the key
> > That should have shortened the key lookup time.)
> >
> > Another bpf prog is with the new BPF_MAP_TYPE_SK_STORAGE.
> >
> > Both are storing a "u32 cnt", do a lookup on "egress_skb/cgroup" for
> > each egress skb and then bump the cnt. netperf is used to drive
> > data with 4096 connected UDP sockets.
> >
> > BPF_MAP_TYPE_HASH with a modifier verifier (152ns per bpf run)
> > 27: cgroup_skb name egress_sk_map tag 74f56e832918070b run_time_ns 58280107540 run_cnt 381347633
> > loaded_at 2019-04-15T13:46:39-0700 uid 0
> > xlated 344B jited 258B memlock 4096B map_ids 16
> > btf_id 5
> >
> > BPF_MAP_TYPE_SK_STORAGE in this patch (66ns per bpf run)
> > 30: cgroup_skb name egress_sk_stora tag d4aa70984cc7bbf6 run_time_ns 25617093319 run_cnt 390989739
> > loaded_at 2019-04-15T13:47:54-0700 uid 0
> > xlated 168B jited 156B memlock 4096B map_ids 17
> > btf_id 6
> >
> > Here is a high-level picture on how are the objects organized:
> >
> > sk
> > ┌──────┐
> > │ │
> > │ │
> > │ │
> > │*sk_bpf_storage─────▶ bpf_sk_storage
> > └──────┘ ┌───────┐
> > ┌───────────┤ list │
> > │ │ │
> > │ │ │
> > │ │ │
> > │ └───────┘
> > │
> > │ elem
> > │ ┌────────┐
> > ├─▶│ snode │
> > │ ├────────┤
> > │ │ data │ bpf_map
> > │ ├────────┤ ┌─────────┐
> > │ │map_node│◀─┬─────┤ list │
> > │ └────────┘ │ │ │
> > │ │ │ │
> > │ elem │ │ │
> > │ ┌────────┐ │ └─────────┘
> > └─▶│ snode │ │
> > ├────────┤ │
> > bpf_map │ data │ │
> > ┌─────────┐ ├────────┤ │
> > │ list ├───────▶│map_node│ │
> > │ │ └────────┘ │
> > │ │ │
> > │ │ elem │
> > └─────────┘ ┌────────┐ │
> > ┌─▶│ snode │ │
> > │ ├────────┤ │
> > │ │ data │ │
> > │ ├────────┤ │
> > │ │map_node│◀─┘
> > │ └────────┘
> > │
> > │
> > │ ┌───────┐
> > sk └──────────│ list │
> > ┌──────┐ │ │
> > │ │ │ │
> > │ │ │ │
> > │ │ └───────┘
> > │*sk_bpf_storage───────▶bpf_sk_storage
> > └──────┘
> That graph looks awesome, how did you do that? :-)
I use an OSX app "monodraw".
>
> > Signed-off-by: Martin KaFai Lau <kafai@...com>
> > ---
> > include/linux/bpf.h | 2 +
> > include/linux/bpf_types.h | 1 +
> > include/net/bpf_sk_storage.h | 13 +
> > include/net/sock.h | 5 +
> > include/uapi/linux/bpf.h | 44 +-
> > kernel/bpf/syscall.c | 3 +-
> > kernel/bpf/verifier.c | 27 +-
> > net/bpf/test_run.c | 2 +
> > net/core/Makefile | 1 +
> > net/core/bpf_sk_storage.c | 796 +++++++++++++++++++++++++++++++++++
> > net/core/filter.c | 12 +
> > net/core/sock.c | 5 +
> > 12 files changed, 906 insertions(+), 5 deletions(-)
> > create mode 100644 include/net/bpf_sk_storage.h
> > create mode 100644 net/core/bpf_sk_storage.c
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index f15432d90728..0d2788beacd2 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -184,6 +184,7 @@ enum bpf_arg_type {
> > ARG_PTR_TO_MAP_KEY, /* pointer to stack used as map key */
> > ARG_PTR_TO_MAP_VALUE, /* pointer to stack used as map value */
> > ARG_PTR_TO_UNINIT_MAP_VALUE, /* pointer to valid memory used to store a map value */
> > + ARG_PTR_TO_MAP_VALUE_OR_NULL, /* pointer to stack used as map value or NULL */
> >
> > /* the following constraints used to prototype bpf_memcmp() and other
> > * functions that access data on eBPF program stack
> > @@ -204,6 +205,7 @@ enum bpf_arg_type {
> > ARG_PTR_TO_SOCK_COMMON, /* pointer to sock_common */
> > ARG_PTR_TO_INT, /* pointer to int */
> > ARG_PTR_TO_LONG, /* pointer to long */
> > + ARG_PTR_TO_SOCKET, /* pointer to bpf_sock (fullsock) */
> > };
> >
> > /* type of values returned from helper functions */
> > diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> > index d26991a16894..eb1e4f867a5e 100644
> > --- a/include/linux/bpf_types.h
> > +++ b/include/linux/bpf_types.h
> > @@ -60,6 +60,7 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY_OF_MAPS, array_of_maps_map_ops)
> > BPF_MAP_TYPE(BPF_MAP_TYPE_HASH_OF_MAPS, htab_of_maps_map_ops)
> > #ifdef CONFIG_NET
> > BPF_MAP_TYPE(BPF_MAP_TYPE_DEVMAP, dev_map_ops)
> > +BPF_MAP_TYPE(BPF_MAP_TYPE_SK_STORAGE, sk_storage_map_ops)
> > #if defined(CONFIG_BPF_STREAM_PARSER)
> > BPF_MAP_TYPE(BPF_MAP_TYPE_SOCKMAP, sock_map_ops)
> > BPF_MAP_TYPE(BPF_MAP_TYPE_SOCKHASH, sock_hash_ops)
> > diff --git a/include/net/bpf_sk_storage.h b/include/net/bpf_sk_storage.h
> > new file mode 100644
> > index 000000000000..b9dcb02e756b
> > --- /dev/null
> > +++ b/include/net/bpf_sk_storage.h
> > @@ -0,0 +1,13 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/* Copyright (c) 2019 Facebook */
> > +#ifndef _BPF_SK_STORAGE_H
> > +#define _BPF_SK_STORAGE_H
> > +
> > +struct sock;
> > +
> > +void bpf_sk_storage_free(struct sock *sk);
> > +
> > +extern const struct bpf_func_proto bpf_sk_storage_get_proto;
> > +extern const struct bpf_func_proto bpf_sk_storage_delete_proto;
> > +
> > +#endif /* _BPF_SK_STORAGE_H */
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index 784cd19d5ff7..4d208c0f9c14 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -236,6 +236,8 @@ struct sock_common {
> > /* public: */
> > };
> >
> > +struct bpf_sk_storage;
> > +
> > /**
> > * struct sock - network layer representation of sockets
> > * @__sk_common: shared layout with inet_timewait_sock
> > @@ -510,6 +512,9 @@ struct sock {
> > #endif
> > void (*sk_destruct)(struct sock *sk);
> > struct sock_reuseport __rcu *sk_reuseport_cb;
> > +#ifdef CONFIG_BPF_SYSCALL
> > + struct bpf_sk_storage __rcu *sk_bpf_storage;
> > +#endif
> > struct rcu_head sk_rcu;
> > };
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index eaf2d3284248..080ff8313ced 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -133,6 +133,7 @@ enum bpf_map_type {
> > BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE,
> > BPF_MAP_TYPE_QUEUE,
> > BPF_MAP_TYPE_STACK,
> > + BPF_MAP_TYPE_SK_STORAGE,
> > };
> >
> > /* Note that tracing related programs such as
> > @@ -2629,6 +2630,42 @@ union bpf_attr {
> > * was provided.
> > *
> > * **-ERANGE** if resulting value was out of range.
> > + *
> > + * void *bpf_sk_storage_get(struct bpf_map *map, struct bpf_sock *sk, void *value, u64 flags)
> > + * Description
> > + * Get a bpf-local-storage from a sk.
> > + *
> > + * Logically, it could be thought of getting the value from
> > + * a *map* with *sk* as the **key**. From this
> > + * perspective, the usage is not much different from
> > + * **bpf_map_lookup_elem(map, &sk)** except this
> > + * helper enforces the key must be a **bpf_fullsock()**
> > + * and the map must be a BPF_MAP_TYPE_SK_STORAGE also.
> > + *
> > + * Underneath, the value is stored locally at *sk* instead of
> > + * the map. The *map* is used as the bpf-local-storage **type**.
> > + * The bpf-local-storage **type** (i.e. the *map*) is searched
> > + * against all bpf-local-storages residing at sk.
> > + *
> > + * An optional *flags* (BPF_SK_STORAGE_GET_F_CREATE) can be
> > + * used such that a new bpf-local-storage will be
> > + * created if one does not exist. *value* can be used
> > + * together with BPF_SK_STORAGE_GET_F_CREATE to specify
> > + * the initial value of a bpf-local-storage. If *value* is
> > + * NULL, the new bpf-local-storage will be zero initialized.
> > + * Return
> > + * A bpf-local-storage pointer is returned on success.
> > + *
> > + * **NULL** if not found or there was an error in adding
> > + * a new bpf-local-storage.
> > + *
> > + * int bpf_sk_storage_delete(struct bpf_map *map, struct bpf_sock *sk)
> > + * Description
> > + * Delete a bpf-local-storage from a sk.
> > + * Return
> > + * 0 on success.
> > + *
> > + * **-ENOENT** if the bpf-local-storage cannot be found.
> > */
> > #define __BPF_FUNC_MAPPER(FN) \
> > FN(unspec), \
> > @@ -2737,7 +2774,9 @@ union bpf_attr {
> > FN(sysctl_get_new_value), \
> > FN(sysctl_set_new_value), \
> > FN(strtol), \
> > - FN(strtoul),
> > + FN(strtoul), \
> > + FN(sk_storage_get), \
> > + FN(sk_storage_delete),
> >
> > /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> > * function eBPF program intends to call
> > @@ -2813,6 +2852,9 @@ enum bpf_func_id {
> > /* BPF_FUNC_sysctl_get_name flags. */
> > #define BPF_F_SYSCTL_BASE_NAME (1ULL << 0)
> >
> > +/* BPF_FUNC_sk_storage_get flags */
> > +#define BPF_SK_STORAGE_GET_F_CREATE (1ULL << 0)
> > +
> > /* Mode for BPF_FUNC_skb_adjust_room helper. */
> > enum bpf_adj_room_mode {
> > BPF_ADJ_ROOM_NET,
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index 92c9b8a32b50..69c9cb7cf5f7 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -526,7 +526,8 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
> > return -EACCES;
> > if (map->map_type != BPF_MAP_TYPE_HASH &&
> > map->map_type != BPF_MAP_TYPE_ARRAY &&
> > - map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE)
> > + map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE &&
> > + map->map_type != BPF_MAP_TYPE_SK_STORAGE)
> > return -ENOTSUPP;
> > if (map->spin_lock_off + sizeof(struct bpf_spin_lock) >
> > map->value_size) {
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index dc01abd27849..6ed13a03cdec 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -2525,10 +2525,15 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
> >
> > if (arg_type == ARG_PTR_TO_MAP_KEY ||
> > arg_type == ARG_PTR_TO_MAP_VALUE ||
> > - arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
> > + arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE ||
> > + arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL) {
> > expected_type = PTR_TO_STACK;
> > - if (!type_is_pkt_pointer(type) && type != PTR_TO_MAP_VALUE &&
> > - type != expected_type)
> > + if (register_is_null(reg) &&
> > + arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL)
> > + /* final test in check_stack_boundary() */;
> > + else if (!type_is_pkt_pointer(type) &&
> > + type != PTR_TO_MAP_VALUE &&
> > + type != expected_type)
> > goto err_type;
> > } else if (arg_type == ARG_CONST_SIZE ||
> > arg_type == ARG_CONST_SIZE_OR_ZERO) {
> > @@ -2560,6 +2565,10 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
> > }
> > meta->ref_obj_id = reg->ref_obj_id;
> > }
> > + } else if (arg_type == ARG_PTR_TO_SOCKET) {
> > + expected_type = PTR_TO_SOCKET;
> > + if (type != expected_type)
> > + goto err_type;
> > } else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {
> > if (meta->func_id == BPF_FUNC_spin_lock) {
> > if (process_spin_lock(env, regno, true))
> > @@ -2617,6 +2626,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
> > meta->map_ptr->key_size, false,
> > NULL);
> > } else if (arg_type == ARG_PTR_TO_MAP_VALUE ||
> > + (arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL &&
> > + !register_is_null(reg)) ||
> > arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
> > /* bpf_map_xxx(..., map_ptr, ..., value) call:
> > * check [value, value + map->value_size) validity
> > @@ -2766,6 +2777,11 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
> > func_id != BPF_FUNC_map_push_elem)
> > goto error;
> > break;
> > + case BPF_MAP_TYPE_SK_STORAGE:
> > + if (func_id != BPF_FUNC_sk_storage_get &&
> > + func_id != BPF_FUNC_sk_storage_delete)
> > + goto error;
> > + break;
> > default:
> > break;
> > }
> > @@ -2829,6 +2845,11 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
> > map->map_type != BPF_MAP_TYPE_STACK)
> > goto error;
> > break;
> > + case BPF_FUNC_sk_storage_get:
> > + case BPF_FUNC_sk_storage_delete:
> > + if (map->map_type != BPF_MAP_TYPE_SK_STORAGE)
> > + goto error;
> > + break;
> > default:
> > break;
> > }
> > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> > index 8606e5aef0b6..8c9331913753 100644
> > --- a/net/bpf/test_run.c
> > +++ b/net/bpf/test_run.c
> > @@ -10,6 +10,7 @@
> > #include <linux/etherdevice.h>
> > #include <linux/filter.h>
> > #include <linux/sched/signal.h>
> > +#include <net/bpf_sk_storage.h>
> > #include <net/sock.h>
> > #include <net/tcp.h>
> >
> > @@ -331,6 +332,7 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
> > sizeof(struct __sk_buff));
> > out:
> > kfree_skb(skb);
> > + bpf_sk_storage_free(sk);
> > kfree(sk);
> > kfree(ctx);
> > return ret;
> > diff --git a/net/core/Makefile b/net/core/Makefile
> > index f97d6254e564..a104dc8faafc 100644
> > --- a/net/core/Makefile
> > +++ b/net/core/Makefile
> > @@ -34,3 +34,4 @@ obj-$(CONFIG_HWBM) += hwbm.o
> > obj-$(CONFIG_NET_DEVLINK) += devlink.o
> > obj-$(CONFIG_GRO_CELLS) += gro_cells.o
> > obj-$(CONFIG_FAILOVER) += failover.o
> > +obj-$(CONFIG_BPF_SYSCALL) += bpf_sk_storage.o
> > diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
> > new file mode 100644
> > index 000000000000..c01d4b9207e0
> > --- /dev/null
> > +++ b/net/core/bpf_sk_storage.c
> > @@ -0,0 +1,796 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2019 Facebook */
> > +#include <linux/rculist.h>
> > +#include <linux/list.h>
> > +#include <linux/hash.h>
> > +#include <linux/types.h>
> > +#include <linux/spinlock.h>
> > +#include <linux/bpf.h>
> > +#include <net/bpf_sk_storage.h>
> > +#include <net/sock.h>
> > +#include <uapi/linux/btf.h>
> > +
> > +static atomic_t cache_idx;
> Can this be made per-bpf_sk_storage? And be incremented in the slow path
> of __sk_storage_lookup?
Thanks for reviewing.
Note that, the bpf_sk_storage_map (smap) is the "type" of
a sk-local-storage, a smap is shared among multiple bpf_sk_storage.
Hence, it cannot.
What is the concern on incrementing it during map_alloc time?
>
> > +struct bucket {
> > + struct hlist_head list;
> > + raw_spinlock_t lock;
> > +};
> > +
> > +/* Thp map is not the primary owner of a bpf_sk_storage_elem.
> > + * Instead, the sk->sk_bpf_storage is.
> > + *
> > + * The map (bpf_sk_storage_map) is for two purposes
> > + * 1. Define the size of the "sk local storage". It is
> > + * the map's value_size.
> > + *
> > + * 2. Maintain a list to keep track of all elems such
> > + * that they can be cleaned up during the map destruction.
> > + *
> > + * When a bpf local storage is being looked up for a
> > + * particular sk, the "bpf_map" pointer is actually used
> > + * as the "key" to search in the list of elem in
> > + * sk->sk_bpf_storage.
> > + *
> > + * Hence, consider sk->sk_bpf_storage is the mini-map
> > + * with the "bpf_map" pointer as the searching key.
> > + */
> > +struct bpf_sk_storage_map {
> > + struct bpf_map map;
> > + /* Lookup elem does not require accessing the map.
> > + *
> > + * Updating/Deleting requires a bucket lock to
> > + * link/unlink the elem from the map. Having
> > + * multiple buckets to improve contention.
> > + */
> > + struct bucket *buckets;
> > + u32 bucket_log;
> > + u16 elem_size;
> > + u16 cache_idx;
> > +};
> > +
> > +struct bpf_sk_storage_data {
> > + /* smap is used as the searching key when looking up
> > + * from sk->sk_bpf_storage.
> > + *
> > + * Put it in the same cacheline as the data to minimize
> > + * the number of cachelines access during the cache hit case.
> > + */
> > + struct bpf_sk_storage_map __rcu *smap;
> > + u8 data[0] __aligned(8);
> > +};
> > +
> > +/* Linked to bpf_sk_storage and bpf_sk_storage_map */
> > +struct bpf_sk_storage_elem {
> > + struct hlist_node map_node; /* Linked to bpf_sk_storage_map */
> > + struct hlist_node snode; /* Linked to bpf_sk_storage */
> > + struct bpf_sk_storage __rcu *sk_storage;
> > + struct rcu_head rcu;
> > + /* 8 bytes hole */
> > + /* The data is stored in aother cacheline to minimize
> > + * the number of cachelines access during a cache hit.
> > + */
> > + struct bpf_sk_storage_data sdata ____cacheline_aligned;
> > +};
> > +
> > +#define SELEM(_SDATA) container_of((_SDATA), struct bpf_sk_storage_elem, sdata)
> > +#define SDATA(_SELEM) (&(_SELEM)->sdata)
> > +#define BPF_SK_STORAGE_CACHE_SIZE 16
> Is it a number of concurrent programs sk can "efficiently" access?
> Why 16? Maybe add a comment?
16 BPF_MAP_TYPE_SK_STORAGE maps instead of 16 programs. Programs can share
map.
On the program side, having a few bpf_progs running in the networking hotpath
is already a lot. The bpf_prog should have already consolidated the existing
sock-key-ed map usage to minimize the map lookup penalty.
16 has enough runway to grow. I will put some lines in the commit
message.
>
> > +struct bpf_sk_storage {
> > + struct bpf_sk_storage_data __rcu *cache[BPF_SK_STORAGE_CACHE_SIZE];
> > + struct hlist_head list; /* List of bpf_sk_storage_elem */
> > + struct sock *sk; /* The sk that owns the the above "list" of
> > + * bpf_sk_storage_elem.
> > + */
> > + struct rcu_head rcu;
> > + raw_spinlock_t lock; /* Protect adding/removing from the "list" */
> > +};
> > +
> > +static struct bucket *select_bucket(struct bpf_sk_storage_map *smap,
> > + struct bpf_sk_storage_elem *selem)
> > +{
> > + return &smap->buckets[hash_ptr(selem, smap->bucket_log)];
> > +}
> > +
> > +static int omem_charge(struct sock *sk, unsigned int size)
> > +{
> > + /* same check as in sock_kmalloc() */
> > + if (size <= sysctl_optmem_max &&
> > + atomic_read(&sk->sk_omem_alloc) + size < sysctl_optmem_max) {
> > + atomic_add(size, &sk->sk_omem_alloc);
> > + return 0;
> > + }
> > +
> > + return -ENOMEM;
> > +}
> > +
> > +static bool selem_linked_to_sk(const struct bpf_sk_storage_elem *selem)
> > +{
> > + return !hlist_unhashed(&selem->snode);
> > +}
> > +
> > +static bool selem_linked_to_map(const struct bpf_sk_storage_elem *selem)
> > +{
> > + return !hlist_unhashed(&selem->map_node);
> > +}
> > +
> > +static struct bpf_sk_storage_elem *selem_alloc(struct bpf_sk_storage_map *smap,
> > + struct sock *sk, void *value,
> > + bool charge_omem)
> > +{
> > + struct bpf_sk_storage_elem *selem;
> > +
> > + if (charge_omem && omem_charge(sk, smap->elem_size))
> > + return NULL;
> > +
> > + selem = kzalloc(smap->elem_size, GFP_ATOMIC | __GFP_NOWARN);
> > + if (selem) {
> > + if (value)
> > + memcpy(SDATA(selem)->data, value, smap->map.value_size);
> > + return selem;
> > + }
> > +
> > + if (charge_omem)
> > + atomic_sub(smap->elem_size, &sk->sk_omem_alloc);
> > +
> > + return NULL;
> > +}
> > +
> > +/* sk_storage->lock must be held and selem->sk_storage == sk_storage.
> > + * The caller must ensure selem->smap is still valid to be
> > + * dereferenced for its smap->elem_size and smap->cache_idx.
> > + */
> > +static bool __selem_unlink_sk(struct bpf_sk_storage *sk_storage,
> > + struct bpf_sk_storage_elem *selem,
> > + bool uncharge_omem)
> > +{
> > + struct bpf_sk_storage_map *smap;
> > + bool free_sk_storage;
> > + struct sock *sk;
> > +
> > + smap = rcu_dereference(SDATA(selem)->smap);
> > + sk = sk_storage->sk;
> > +
> > + /* All uncharging on sk->sk_omem_alloc must be done first.
> > + * sk may be freed once the last selem is unlinked from sk_storage.
> > + */
> > + if (uncharge_omem)
> > + atomic_sub(smap->elem_size, &sk->sk_omem_alloc);
> > +
> > + free_sk_storage = hlist_is_singular_node(&selem->snode,
> > + &sk_storage->list);
> > + if (free_sk_storage) {
> > + atomic_sub(sizeof(struct bpf_sk_storage), &sk->sk_omem_alloc);
> > + sk_storage->sk = NULL;
> > + /* After this RCU_INIT, sk may be freed and cannot be used */
> > + RCU_INIT_POINTER(sk->sk_bpf_storage, NULL);
> > +
> > + /* sk_storage is not freed now. sk_storage->lock is
> > + * still held and raw_spin_unlock_bh(&sk_storage->lock)
> > + * will be done by the caller.
> > + *
> > + * Although the unlock will be done under
> > + * rcu_read_lock(), it is more intutivie to
> > + * read if kfree_rcu(sk_storage, rcu) is done
> > + * after the raw_spin_unlock_bh(&sk_storage->lock).
> > + *
> > + * Hence, a "bool free_sk_storage" is returned
> > + * to the caller which then calls the kfree_rcu()
> > + * after unlock.
> > + */
> > + }
> > + hlist_del_init_rcu(&selem->snode);
> > + if (rcu_access_pointer(sk_storage->cache[smap->cache_idx]) ==
> > + SDATA(selem))
> > + RCU_INIT_POINTER(sk_storage->cache[smap->cache_idx], NULL);
> > +
> > + kfree_rcu(selem, rcu);
> > +
> > + return free_sk_storage;
> > +}
> > +
> > +static void selem_unlink_sk(struct bpf_sk_storage_elem *selem)
> > +{
> > + struct bpf_sk_storage *sk_storage;
> > + bool free_sk_storage = false;
> > +
> > + if (unlikely(!selem_linked_to_sk(selem)))
> > + /* selem has already been unlinked from sk */
> > + return;
> > +
> > + sk_storage = rcu_dereference(selem->sk_storage);
> > + raw_spin_lock_bh(&sk_storage->lock);
> > + if (likely(selem_linked_to_sk(selem)))
> > + free_sk_storage = __selem_unlink_sk(sk_storage, selem, true);
> > + raw_spin_unlock_bh(&sk_storage->lock);
> > +
> > + if (free_sk_storage)
> > + kfree_rcu(sk_storage, rcu);
> > +}
> > +
> > +/* sk_storage->lock must be held and sk_storage->list cannot be empty */
> > +static void __selem_link_sk(struct bpf_sk_storage *sk_storage,
> > + struct bpf_sk_storage_elem *selem)
> > +{
> > + RCU_INIT_POINTER(selem->sk_storage, sk_storage);
> > + hlist_add_head(&selem->snode, &sk_storage->list);
> > +}
> > +
> > +static void selem_unlink_map(struct bpf_sk_storage_elem *selem)
> > +{
> > + struct bpf_sk_storage_map *smap;
> > + struct bucket *b;
> > +
> > + if (unlikely(!selem_linked_to_map(selem)))
> > + /* selem has already be unlinked from smap */
> > + return;
> > +
> > + smap = rcu_dereference(SDATA(selem)->smap);
> > + b = select_bucket(smap, selem);
> > + raw_spin_lock_bh(&b->lock);
> > + if (likely(selem_linked_to_map(selem)))
> > + hlist_del_init_rcu(&selem->map_node);
> > + raw_spin_unlock_bh(&b->lock);
> > +}
> > +
> > +static void selem_link_map(struct bpf_sk_storage_map *smap,
> > + struct bpf_sk_storage_elem *selem)
> > +{
> > + struct bucket *b = select_bucket(smap, selem);
> > +
> > + raw_spin_lock_bh(&b->lock);
> > + RCU_INIT_POINTER(SDATA(selem)->smap, smap);
> > + hlist_add_head_rcu(&selem->map_node, &b->list);
> > + raw_spin_unlock_bh(&b->lock);
> > +}
> > +
> > +static void selem_unlink(struct bpf_sk_storage_elem *selem)
> > +{
> > + /* Always unlink from map before unlinking from sk_storage
> > + * because selem will be freed after successfully unlinked from
> > + * the sk_storage.
> > + */
> > + selem_unlink_map(selem);
> > + selem_unlink_sk(selem);
> > +}
> > +
> > +static struct bpf_sk_storage_data *
> > +__sk_storage_lookup(struct bpf_sk_storage *sk_storage,
> > + struct bpf_sk_storage_map *smap,
> > + bool cacheit_lockit)
> > +{
> > + struct bpf_sk_storage_data *sdata;
> > + struct bpf_sk_storage_elem *selem;
> > +
> > + /* Fast path (cache hit) */
> > + sdata = rcu_dereference(sk_storage->cache[smap->cache_idx]);
> > + if (sdata && rcu_access_pointer(sdata->smap) == smap)
> > + return sdata;
> > +
> > + /* Slow path (cache miss) */
> > + hlist_for_each_entry_rcu(selem, &sk_storage->list, snode)
> > + if (rcu_access_pointer(SDATA(selem)->smap) == smap)
> > + break;
> > +
> > + if (!selem)
> > + return NULL;
> > +
> > + sdata = SDATA(selem);
> > + if (cacheit_lockit) {
> > + /* spinlock is needed to avoid racing with the
> > + * parallel delete. Otherwise, publishing an already
> > + * deleted sdata to the cache will become a use-after-free
> > + * problem in the next __sk_storage_lookup().
> > + */
> > + raw_spin_lock_bh(&sk_storage->lock);
> > + if (selem_linked_to_sk(selem))
> > + rcu_assign_pointer(sk_storage->cache[smap->cache_idx],
> > + sdata);
> > + raw_spin_unlock_bh(&sk_storage->lock);
> > + }
> > +
> > + return sdata;
> > +}
> > +
> > +static struct bpf_sk_storage_data *
> > +sk_storage_lookup(struct sock *sk, struct bpf_map *map, bool cacheit_lockit)
> > +{
> > + struct bpf_sk_storage *sk_storage;
> > + struct bpf_sk_storage_map *smap;
> > +
> > + sk_storage = rcu_dereference(sk->sk_bpf_storage);
> > + if (!sk_storage)
> > + return NULL;
> > +
> > + smap = (struct bpf_sk_storage_map *)map;
> > + return __sk_storage_lookup(sk_storage, smap, cacheit_lockit);
> > +}
> > +
> > +static int check_flags(const struct bpf_sk_storage_data *old_sdata,
> > + u64 map_flags)
> > +{
> > + if (old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST)
> > + /* elem already exists */
> > + return -EEXIST;
> > +
> > + if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
> > + /* elem doesn't exist, cannot update it */
> > + return -ENOENT;
> > +
> > + return 0;
> > +}
> > +
> > +static int sk_storage_alloc(struct sock *sk,
> > + struct bpf_sk_storage_map *smap,
> > + struct bpf_sk_storage_elem *first_selem)
> > +{
> > + struct bpf_sk_storage *prev_sk_storage, *sk_storage;
> > + int err;
> > +
> > + err = omem_charge(sk, sizeof(*sk_storage));
> > + if (err)
> > + return err;
> > +
> > + sk_storage = kzalloc(sizeof(*sk_storage), GFP_ATOMIC | __GFP_NOWARN);
> > + if (!sk_storage) {
> > + err = -ENOMEM;
> > + goto uncharge;
> > + }
> > + INIT_HLIST_HEAD(&sk_storage->list);
> > + raw_spin_lock_init(&sk_storage->lock);
> > + sk_storage->sk = sk;
> > +
> > + __selem_link_sk(sk_storage, first_selem);
> > + selem_link_map(smap, first_selem);
> > + /* Publish sk_storage to sk. sk->sk_lock cannot be acquired.
> > + * Hence, atomic ops is used to set sk->sk_bpf_storage
> > + * from NULL to the newly allocated sk_storage ptr.
> > + *
> > + * From now on, the sk->sk_bpf_storage pointer is protected
> > + * by the sk_storage->lock. Hence, when freeing
> > + * the sk->sk_bpf_storage, the sk_storage->lock must
> > + * be held before setting sk->sk_bpf_storage to NULL.
> > + */
> > + prev_sk_storage = cmpxchg((struct bpf_sk_storage **)&sk->sk_bpf_storage,
> > + NULL, sk_storage);
> > + if (unlikely(prev_sk_storage)) {
> > + selem_unlink_map(first_selem);
> > + err = -EAGAIN;
> > + goto uncharge;
> > +
> > + /* Note that even first_selem was linked to smap's
> > + * bucket->list, first_selem can be freed immediately
> > + * (instead of kfree_rcu) because
> > + * bpf_sk_storage_map_free() does a
> > + * synchronize_rcu() before walking the bucket->list.
> > + * Hence, no one is accessing selem from the
> > + * bucket->list under rcu_read_lock().
> > + */
> > + }
> > +
> > + return 0;
> > +
> > +uncharge:
> > + kfree(sk_storage);
> > + atomic_sub(sizeof(*sk_storage), &sk->sk_omem_alloc);
> > + return err;
> > +}
> > +
> > +/* sk cannot be going away because it is linking new elem
> > + * to sk->sk_bpf_storage. (i.e. sk->sk_refcnt cannot be 0).
> > + * Otherwise, it will become a leak (and other memory issues
> > + * during map destruction).
> > + */
> > +static struct bpf_sk_storage_data *sk_storage_update(struct sock *sk,
> > + struct bpf_map *map,
> > + void *value,
> > + u64 map_flags)
> > +{
> > + struct bpf_sk_storage_data *old_sdata = NULL;
> > + struct bpf_sk_storage_elem *selem;
> > + struct bpf_sk_storage *sk_storage;
> > + struct bpf_sk_storage_map *smap;
> > + int err;
> > +
> > + /* BPF_EXIST and BPF_NOEXIST cannot be both set */
> > + if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
> > + /* BPF_F_LOCK can only be used in a value with spin_lock */
> > + unlikely((map_flags & BPF_F_LOCK) && !map_value_has_spin_lock(map)))
> > + return ERR_PTR(-EINVAL);
> > +
> > + smap = (struct bpf_sk_storage_map *)map;
> > + sk_storage = rcu_dereference(sk->sk_bpf_storage);
> > + if (!sk_storage || hlist_empty(&sk_storage->list)) {
> > + /* Very first elem for this sk */
> > + err = check_flags(NULL, map_flags);
> > + if (err)
> > + return ERR_PTR(err);
> > +
> > + selem = selem_alloc(smap, sk, value, true);
> > + if (!selem)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + err = sk_storage_alloc(sk, smap, selem);
> > + if (err) {
> > + kfree(selem);
> > + atomic_sub(smap->elem_size, &sk->sk_omem_alloc);
> > + return ERR_PTR(err);
> > + }
> > +
> > + return SDATA(selem);
> > + }
> > +
> > + if ((map_flags & BPF_F_LOCK) && !(map_flags & BPF_NOEXIST)) {
> > + /* Hoping to find an old_sdata to do inline update
> > + * such that it can avoid taking the sk_storage->lock
> > + * and changing the lists.
> > + */
> > + old_sdata = __sk_storage_lookup(sk_storage, smap, false);
> > + err = check_flags(old_sdata, map_flags);
> > + if (err)
> > + return ERR_PTR(err);
> > + if (old_sdata && selem_linked_to_sk(SELEM(old_sdata))) {
> > + copy_map_value_locked(map, old_sdata->data,
> > + value, false);
> > + return old_sdata;
> > + }
> > + }
> > +
> > + raw_spin_lock_bh(&sk_storage->lock);
> > +
> > + /* Recheck sk_storage->list under sk_storage->lock */
> > + if (unlikely(hlist_empty(&sk_storage->list))) {
> > + /* A parallel del is happening and sk_storage is going
> > + * away. It has just been checked before, so very
> > + * unlikely. Return instead of retry to keep things
> > + * simple.
> > + */
> > + err = -EAGAIN;
> > + goto unlock_err;
> > + }
> > +
> > + old_sdata = __sk_storage_lookup(sk_storage, smap, false);
> > + err = check_flags(old_sdata, map_flags);
> > + if (err)
> > + goto unlock_err;
> > +
> > + if (old_sdata && (map_flags & BPF_F_LOCK)) {
> > + copy_map_value_locked(map, old_sdata->data, value, false);
> > + selem = SELEM(old_sdata);
> > + goto unlock;
> > + }
> > +
> > + /* sk_storage->lock is held. Hence, we are sure
> > + * we can unlink and uncharge the old_sdata successfully
> > + * later. Hence, instead of charging the new selem now
> > + * and then uncharge the old selem later (which may cause
> > + * a potential but unnecessary charge failure), avoid taking
> > + * a charge at all here (the "!old_sdata" check) and the
> > + * old_sdata will not be uncharged later during __selem_unlink_sk().
> > + */
> > + selem = selem_alloc(smap, sk, value, !old_sdata);
> > + if (!selem) {
> > + err = -ENOMEM;
> > + goto unlock_err;
> > + }
> > +
> > + /* First, link the new selem to the map */
> > + selem_link_map(smap, selem);
> > +
> > + /* Second, link (and publish) the new selem to sk_storage */
> > + __selem_link_sk(sk_storage, selem);
> > +
> > + /* Third, remove old selem, SELEM(old_sdata) */
> > + if (old_sdata) {
> > + selem_unlink_map(SELEM(old_sdata));
> > + __selem_unlink_sk(sk_storage, SELEM(old_sdata), false);
> > + }
> > +
> > +unlock:
> > + raw_spin_unlock_bh(&sk_storage->lock);
> > + return SDATA(selem);
> > +
> > +unlock_err:
> > + raw_spin_unlock_bh(&sk_storage->lock);
> > + return ERR_PTR(err);
> > +}
> > +
> > +static int sk_storage_delete(struct sock *sk, struct bpf_map *map)
> > +{
> > + struct bpf_sk_storage_data *sdata;
> > +
> > + sdata = sk_storage_lookup(sk, map, false);
> > + if (!sdata)
> > + return -ENOENT;
> > +
> > + selem_unlink(SELEM(sdata));
> Where is sdata (or I guess bpf_sk_storage_elem) kfree'd?
__selem_unlink_sk()
>
> > + return 0;
> > +}
> > +
> > +/* Called by __sk_destruct() */
> > +void bpf_sk_storage_free(struct sock *sk)
> > +{
> > + struct bpf_sk_storage_elem *selem;
> > + struct bpf_sk_storage *sk_storage;
> > + bool free_sk_storage = false;
> > + struct hlist_node *n;
> > +
> > + rcu_read_lock();
> > + sk_storage = rcu_dereference(sk->sk_bpf_storage);
> > + if (!sk_storage) {
> > + rcu_read_unlock();
> > + return;
> > + }
> > +
> > + /* Netiher the bpf_prog nor the bpf-map's syscall
> > + * could be modifying the sk_storage->list now.
> > + * Thus, no elem can be added-to or deleted-from the
> > + * sk_storage->list by the bpf_prog or by the bpf-map's syscall.
> > + *
> > + * It is racing with bpf_sk_storage_map_free() alone
> > + * when unlinking elem from the sk_storage->list and
> > + * the map's bucket->list.
> > + */
> > + raw_spin_lock_bh(&sk_storage->lock);
> > + hlist_for_each_entry_safe(selem, n, &sk_storage->list, snode) {
> > + /* Always unlink from map before unlinking from
> > + * sk_storage.
> > + */
> > + selem_unlink_map(selem);
> > + free_sk_storage = __selem_unlink_sk(sk_storage, selem, true);
> > + }
> > + raw_spin_unlock_bh(&sk_storage->lock);
> > + rcu_read_unlock();
> > +
> > + if (free_sk_storage)
> > + kfree_rcu(sk_storage, rcu);
> > +}
> > +
> > +static void bpf_sk_storage_map_free(struct bpf_map *map)
> > +{
> > + struct bpf_sk_storage_elem *selem;
> > + struct bpf_sk_storage_map *smap;
> > + struct bucket *b;
> > + unsigned int i;
> > +
> > + smap = (struct bpf_sk_storage_map *)map;
> > +
> > + synchronize_rcu();
> > +
> > + /* bpf prog and the userspace can no longer access this map
> > + * now. No new selem (of this map) can be added
> > + * to the sk->sk_bpf_storage or to the map bucket's list.
> > + *
> > + * The elem of this map can be cleaned up here
> > + * or
> > + * by bpf_sk_storage_free() during __sk_destruct().
> > + */
> > + for (i = 0; i < (1U << smap->bucket_log); i++) {
> > + b = &smap->buckets[i];
> > +
> > + rcu_read_lock();
> > + /* No one is adding to b->list now */
> > + while ((selem = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(&b->list)),
> > + struct bpf_sk_storage_elem,
> > + map_node))) {
> > + selem_unlink(selem);
> > + cond_resched_rcu();
> > + }
> > + rcu_read_unlock();
> > + }
> > +
> > + /* bpf_sk_storage_free() may still need to access the map.
> > + * e.g. bpf_sk_storage_free() has unlinked selem from the map
> > + * which then made the above while((selem = ...)) loop
> > + * exited immediately.
> > + *
> > + * However, the bpf_sk_storage_free() still needs to access
> > + * the smap->elem_size to do the uncharging in
> > + * __selem_unlink_sk().
> > + *
> > + * Hence, wait another rcu grace period for the
> > + * bpf_sk_storage_free() to finish.
> > + */
> > + synchronize_rcu();
> > +
> > + kvfree(smap->buckets);
> > + kfree(map);
> > +}
> > +
> > +static struct bpf_map *bpf_sk_storage_map_alloc(union bpf_attr *attr)
> > +{
> > + struct bpf_sk_storage_map *smap;
> > + unsigned int i;
> > + u32 nbuckets;
> > + u64 cost;
> > +
> > + if (attr->map_flags != BPF_F_NO_PREALLOC || attr->max_entries ||
> > + attr->key_size != sizeof(int) || !attr->value_size ||
> > + /* Enforce BTF for userspace sk dumping */
> > + !attr->btf_key_type_id || !attr->btf_value_type_id)
> > + return ERR_PTR(-EINVAL);
> > +
> > + if (!capable(CAP_SYS_ADMIN))
> > + return ERR_PTR(-EPERM);
> Any specific reason for CAP_SYS_ADMIN?
Like other new bpf features. It is first limited to CAP_SYS_ADMIN at
the beginning.
>
> > + if (attr->value_size >= KMALLOC_MAX_SIZE -
> > + MAX_BPF_STACK - sizeof(struct bpf_sk_storage_elem) ||
> > + /* selem->elem_size is a u16 */
> > + attr->value_size > U16_MAX - sizeof(struct bpf_sk_storage_elem))
> > + return ERR_PTR(-E2BIG);
> What's the rationale here for E2BIG? Same as htab_map_alloc_check?
Yes
> Why not use .map_alloc_check btw?
Will move.
>
> > + smap = kzalloc(sizeof(*smap), GFP_USER | __GFP_NOWARN);
> > + if (!smap)
> > + return ERR_PTR(-ENOMEM);
> > + bpf_map_init_from_attr(&smap->map, attr);
> > +
> > + smap->bucket_log = ilog2(roundup_pow_of_two(num_possible_cpus()));
> > + nbuckets = 1U << smap->bucket_log;
> > + smap->buckets = kvcalloc(sizeof(*smap->buckets), nbuckets,
> > + GFP_USER | __GFP_NOWARN);
> > + if (!smap->buckets) {
> > + kfree(smap);
> > + return ERR_PTR(-ENOMEM);
> > + }
> > + cost = sizeof(*smap->buckets) * nbuckets + sizeof(*smap);
> > +
> > + for (i = 0; i < nbuckets; i++) {
> > + INIT_HLIST_HEAD(&smap->buckets[i].list);
> > + raw_spin_lock_init(&smap->buckets[i].lock);
> > + }
> > +
> > + smap->elem_size = sizeof(struct bpf_sk_storage_elem) + attr->value_size;
> > + smap->cache_idx = (unsigned int)atomic_inc_return(&cache_idx) %
> > + BPF_SK_STORAGE_CACHE_SIZE;
> > + smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
> > +
> > + return &smap->map;
> > +}
> > +
> > +static int notsupp_get_next_key(struct bpf_map *map, void *key,
> > + void *next_key)
> > +{
> > + return -ENOTSUPP;
> > +}
> > +
> > +static int bpf_sk_storage_map_check_btf(const struct bpf_map *map,
> > + const struct btf *btf,
> > + const struct btf_type *key_type,
> > + const struct btf_type *value_type)
> > +{
> > + u32 int_data;
> > +
> > + if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
> > + return -EINVAL;
> > +
> > + int_data = *(u32 *)(key_type + 1);
> > + if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))
> > + return -EINVAL;
> > +
> > + return 0;
> > +}
> > +
> > +static void *bpf_fd_sk_storage_lookup_elem(struct bpf_map *map, void *key)
> > +{
> > + struct bpf_sk_storage_data *sdata;
> > + struct socket *sock;
> > + int fd, err;
> > +
> > + fd = *(int *)key;
> > + sock = sockfd_lookup(fd, &err);
> > + if (sock) {
> > + sdata = sk_storage_lookup(sock->sk, map, true);
> > + sockfd_put(sock);
> > + return sdata ? sdata->data : NULL;
> > + }
> > +
> > + return ERR_PTR(err);
> > +}
> > +
> > +static int bpf_fd_sk_storage_update_elem(struct bpf_map *map, void *key,
> > + void *value, u64 map_flags)
> > +{
> > + struct bpf_sk_storage_data *sdata;
> > + struct socket *sock;
> > + int fd, err;
> > +
> > + fd = *(int *)key;
> > + sock = sockfd_lookup(fd, &err);
> > + if (sock) {
> > + sdata = sk_storage_update(sock->sk, map, value, map_flags);
> > + sockfd_put(sock);
> > + return IS_ERR(sdata) ? PTR_ERR(sdata) : 0;
> > + }
> > +
> > + return err;
> > +}
> > +
> > +static int bpf_fd_sk_storage_delete_elem(struct bpf_map *map, void *key)
> > +{
> > + struct socket *sock;
> > + int fd, err;
> > +
> > + fd = *(int *)key;
> > + sock = sockfd_lookup(fd, &err);
> > + if (sock) {
> > + err = sk_storage_delete(sock->sk, map);
> > + sockfd_put(sock);
> > + return err;
> > + }
> > +
> > + return err;
> > +}
> > +
> > +BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk,
> > + void *, value, u64, flags)
> > +{
> > + struct bpf_sk_storage_data *sdata;
> > +
> > + if (flags > BPF_SK_STORAGE_GET_F_CREATE)
> > + return (unsigned long)NULL;
> > +
> > + sdata = sk_storage_lookup(sk, map, true);
> > + if (sdata)
> > + return (unsigned long)sdata->data;
> > +
> > + if (flags == BPF_SK_STORAGE_GET_F_CREATE &&
> > + /* Cannot add new elem to a going away sk.
> > + * Otherwise, the new elem may become a leak
> > + * (and also other memory issues during map
> > + * destruction).
> > + */
> > + refcount_inc_not_zero(&sk->sk_refcnt)) {
> > + sdata = sk_storage_update(sk, map, value, BPF_NOEXIST);
> > + /* sk must be a fullsock (guaranteed by verifier),
> > + * so sock_gen_put() is unnecessary.
> > + */
> > + sock_put(sk);
> > + return IS_ERR(sdata) ?
> > + (unsigned long)NULL : (unsigned long)sdata->data;
> > + }
> > +
> > + return (unsigned long)NULL;
> > +}
> > +
> > +BPF_CALL_2(bpf_sk_storage_delete, struct bpf_map *, map, struct sock *, sk)
> > +{
> > + if (refcount_inc_not_zero(&sk->sk_refcnt)) {
> > + int err;
> > +
> > + err = sk_storage_delete(sk, map);
> > + sock_put(sk);
> > + return err;
> > + }
> > +
> > + return -ENOENT;
> > +}
> > +
> > +const struct bpf_map_ops sk_storage_map_ops = {
> > + .map_alloc = bpf_sk_storage_map_alloc,
> > + .map_free = bpf_sk_storage_map_free,
> > + .map_get_next_key = notsupp_get_next_key,
> > + .map_lookup_elem = bpf_fd_sk_storage_lookup_elem,
> > + .map_update_elem = bpf_fd_sk_storage_update_elem,
> > + .map_delete_elem = bpf_fd_sk_storage_delete_elem,
> > + .map_check_btf = bpf_sk_storage_map_check_btf,
> > +};
> > +
> > +const struct bpf_func_proto bpf_sk_storage_get_proto = {
> > + .func = bpf_sk_storage_get,
> > + .gpl_only = false,
> > + .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
> > + .arg1_type = ARG_CONST_MAP_PTR,
> > + .arg2_type = ARG_PTR_TO_SOCKET,
> > + .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
> > + .arg4_type = ARG_ANYTHING,
> > +};
> > +
> > +const struct bpf_func_proto bpf_sk_storage_delete_proto = {
> > + .func = bpf_sk_storage_delete,
> > + .gpl_only = false,
> > + .ret_type = RET_INTEGER,
> > + .arg1_type = ARG_CONST_MAP_PTR,
> > + .arg2_type = ARG_PTR_TO_SOCKET,
> > +};
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index 2f88baf39cc2..27b0dc01dc3f 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -75,6 +75,7 @@
> > #include <net/seg6_local.h>
> > #include <net/lwtunnel.h>
> > #include <net/ipv6_stubs.h>
> > +#include <net/bpf_sk_storage.h>
> >
> > /**
> > * sk_filter_trim_cap - run a packet through a socket filter
> > @@ -5903,6 +5904,9 @@ sk_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > }
> > }
> >
> > +const struct bpf_func_proto bpf_sk_storage_get_proto __weak;
> > +const struct bpf_func_proto bpf_sk_storage_delete_proto __weak;
> > +
> > static const struct bpf_func_proto *
> > cg_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > {
> > @@ -5911,6 +5915,10 @@ cg_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > return &bpf_get_local_storage_proto;
> > case BPF_FUNC_sk_fullsock:
> > return &bpf_sk_fullsock_proto;
> > + case BPF_FUNC_sk_storage_get:
> > + return &bpf_sk_storage_get_proto;
> > + case BPF_FUNC_sk_storage_delete:
> > + return &bpf_sk_storage_delete_proto;
> > #ifdef CONFIG_INET
> > case BPF_FUNC_tcp_sock:
> > return &bpf_tcp_sock_proto;
> > @@ -5992,6 +6000,10 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > return &bpf_skb_fib_lookup_proto;
> > case BPF_FUNC_sk_fullsock:
> > return &bpf_sk_fullsock_proto;
> > + case BPF_FUNC_sk_storage_get:
> > + return &bpf_sk_storage_get_proto;
> > + case BPF_FUNC_sk_storage_delete:
> > + return &bpf_sk_storage_delete_proto;
> > #ifdef CONFIG_XFRM
> > case BPF_FUNC_skb_get_xfrm_state:
> > return &bpf_skb_get_xfrm_state_proto;
> > diff --git a/net/core/sock.c b/net/core/sock.c
> > index 443b98d05f1e..9773be724aa9 100644
> > --- a/net/core/sock.c
> > +++ b/net/core/sock.c
> > @@ -137,6 +137,7 @@
> >
> > #include <linux/filter.h>
> > #include <net/sock_reuseport.h>
> > +#include <net/bpf_sk_storage.h>
> >
> > #include <trace/events/sock.h>
> >
> > @@ -1709,6 +1710,10 @@ static void __sk_destruct(struct rcu_head *head)
> >
> > sock_disable_timestamp(sk, SK_FLAGS_TIMESTAMP);
> >
> > +#ifdef CONFIG_BPF_SYSCALL
> > + bpf_sk_storage_free(sk);
> > +#endif
> > +
> > if (atomic_read(&sk->sk_omem_alloc))
> > pr_debug("%s: optmem leakage (%d bytes) detected\n",
> > __func__, atomic_read(&sk->sk_omem_alloc));
> > --
> > 2.17.1
> >
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