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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/bpf/map_array.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to 'Documentation/bpf/map_array.rst')
-rw-r--r-- | Documentation/bpf/map_array.rst | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/Documentation/bpf/map_array.rst b/Documentation/bpf/map_array.rst new file mode 100644 index 000000000..f2f51a53e --- /dev/null +++ b/Documentation/bpf/map_array.rst @@ -0,0 +1,262 @@ +.. SPDX-License-Identifier: GPL-2.0-only +.. Copyright (C) 2022 Red Hat, Inc. + +================================================ +BPF_MAP_TYPE_ARRAY and BPF_MAP_TYPE_PERCPU_ARRAY +================================================ + +.. note:: + - ``BPF_MAP_TYPE_ARRAY`` was introduced in kernel version 3.19 + - ``BPF_MAP_TYPE_PERCPU_ARRAY`` was introduced in version 4.6 + +``BPF_MAP_TYPE_ARRAY`` and ``BPF_MAP_TYPE_PERCPU_ARRAY`` provide generic array +storage. The key type is an unsigned 32-bit integer (4 bytes) and the map is +of constant size. The size of the array is defined in ``max_entries`` at +creation time. All array elements are pre-allocated and zero initialized when +created. ``BPF_MAP_TYPE_PERCPU_ARRAY`` uses a different memory region for each +CPU whereas ``BPF_MAP_TYPE_ARRAY`` uses the same memory region. The value +stored can be of any size, however, all array elements are aligned to 8 +bytes. + +Since kernel 5.5, memory mapping may be enabled for ``BPF_MAP_TYPE_ARRAY`` by +setting the flag ``BPF_F_MMAPABLE``. The map definition is page-aligned and +starts on the first page. Sufficient page-sized and page-aligned blocks of +memory are allocated to store all array values, starting on the second page, +which in some cases will result in over-allocation of memory. The benefit of +using this is increased performance and ease of use since userspace programs +would not be required to use helper functions to access and mutate data. + +Usage +===== + +Kernel BPF +---------- + +bpf_map_lookup_elem() +~~~~~~~~~~~~~~~~~~~~~ + +.. code-block:: c + + void *bpf_map_lookup_elem(struct bpf_map *map, const void *key) + +Array elements can be retrieved using the ``bpf_map_lookup_elem()`` helper. +This helper returns a pointer into the array element, so to avoid data races +with userspace reading the value, the user must use primitives like +``__sync_fetch_and_add()`` when updating the value in-place. + +bpf_map_update_elem() +~~~~~~~~~~~~~~~~~~~~~ + +.. code-block:: c + + long bpf_map_update_elem(struct bpf_map *map, const void *key, const void *value, u64 flags) + +Array elements can be updated using the ``bpf_map_update_elem()`` helper. + +``bpf_map_update_elem()`` returns 0 on success, or negative error in case of +failure. + +Since the array is of constant size, ``bpf_map_delete_elem()`` is not supported. +To clear an array element, you may use ``bpf_map_update_elem()`` to insert a +zero value to that index. + +Per CPU Array +------------- + +Values stored in ``BPF_MAP_TYPE_ARRAY`` can be accessed by multiple programs +across different CPUs. To restrict storage to a single CPU, you may use a +``BPF_MAP_TYPE_PERCPU_ARRAY``. + +When using a ``BPF_MAP_TYPE_PERCPU_ARRAY`` the ``bpf_map_update_elem()`` and +``bpf_map_lookup_elem()`` helpers automatically access the slot for the current +CPU. + +bpf_map_lookup_percpu_elem() +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. code-block:: c + + void *bpf_map_lookup_percpu_elem(struct bpf_map *map, const void *key, u32 cpu) + +The ``bpf_map_lookup_percpu_elem()`` helper can be used to lookup the array +value for a specific CPU. Returns value on success , or ``NULL`` if no entry was +found or ``cpu`` is invalid. + +Concurrency +----------- + +Since kernel version 5.1, the BPF infrastructure provides ``struct bpf_spin_lock`` +to synchronize access. + +Userspace +--------- + +Access from userspace uses libbpf APIs with the same names as above, with +the map identified by its ``fd``. + +Examples +======== + +Please see the ``tools/testing/selftests/bpf`` directory for functional +examples. The code samples below demonstrate API usage. + +Kernel BPF +---------- + +This snippet shows how to declare an array in a BPF program. + +.. code-block:: c + + struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __type(key, u32); + __type(value, long); + __uint(max_entries, 256); + } my_map SEC(".maps"); + + +This example BPF program shows how to access an array element. + +.. code-block:: c + + int bpf_prog(struct __sk_buff *skb) + { + struct iphdr ip; + int index; + long *value; + + if (bpf_skb_load_bytes(skb, ETH_HLEN, &ip, sizeof(ip)) < 0) + return 0; + + index = ip.protocol; + value = bpf_map_lookup_elem(&my_map, &index); + if (value) + __sync_fetch_and_add(value, skb->len); + + return 0; + } + +Userspace +--------- + +BPF_MAP_TYPE_ARRAY +~~~~~~~~~~~~~~~~~~ + +This snippet shows how to create an array, using ``bpf_map_create_opts`` to +set flags. + +.. code-block:: c + + #include <bpf/libbpf.h> + #include <bpf/bpf.h> + + int create_array() + { + int fd; + LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE); + + fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, + "example_array", /* name */ + sizeof(__u32), /* key size */ + sizeof(long), /* value size */ + 256, /* max entries */ + &opts); /* create opts */ + return fd; + } + +This snippet shows how to initialize the elements of an array. + +.. code-block:: c + + int initialize_array(int fd) + { + __u32 i; + long value; + int ret; + + for (i = 0; i < 256; i++) { + value = i; + ret = bpf_map_update_elem(fd, &i, &value, BPF_ANY); + if (ret < 0) + return ret; + } + + return ret; + } + +This snippet shows how to retrieve an element value from an array. + +.. code-block:: c + + int lookup(int fd) + { + __u32 index = 42; + long value; + int ret; + + ret = bpf_map_lookup_elem(fd, &index, &value); + if (ret < 0) + return ret; + + /* use value here */ + assert(value == 42); + + return ret; + } + +BPF_MAP_TYPE_PERCPU_ARRAY +~~~~~~~~~~~~~~~~~~~~~~~~~ + +This snippet shows how to initialize the elements of a per CPU array. + +.. code-block:: c + + int initialize_array(int fd) + { + int ncpus = libbpf_num_possible_cpus(); + long values[ncpus]; + __u32 i, j; + int ret; + + for (i = 0; i < 256 ; i++) { + for (j = 0; j < ncpus; j++) + values[j] = i; + ret = bpf_map_update_elem(fd, &i, &values, BPF_ANY); + if (ret < 0) + return ret; + } + + return ret; + } + +This snippet shows how to access the per CPU elements of an array value. + +.. code-block:: c + + int lookup(int fd) + { + int ncpus = libbpf_num_possible_cpus(); + __u32 index = 42, j; + long values[ncpus]; + int ret; + + ret = bpf_map_lookup_elem(fd, &index, &values); + if (ret < 0) + return ret; + + for (j = 0; j < ncpus; j++) { + /* Use per CPU value here */ + assert(values[j] == 42); + } + + return ret; + } + +Semantics +========= + +As shown in the example above, when accessing a ``BPF_MAP_TYPE_PERCPU_ARRAY`` +in userspace, each value is an array with ``ncpus`` elements. + +When calling ``bpf_map_update_elem()`` the flag ``BPF_NOEXIST`` can not be used +for these maps. |