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author | Linus Torvalds <torvalds@linux-foundation.org> | 2022-12-14 02:47:48 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-12-14 02:47:48 +0300 |
commit | 7e68dd7d07a28faa2e6574dd6b9dbd90cdeaae91 (patch) | |
tree | ae0427c5a3b905f24b3a44b510a9bcf35d9b67a3 /Documentation/bpf/map_array.rst | |
parent | 1ca06f1c1acecbe02124f14a37cce347b8c1a90c (diff) | |
parent | 7c4a6309e27f411743817fe74a832ec2d2798a4b (diff) | |
download | linux-7e68dd7d07a28faa2e6574dd6b9dbd90cdeaae91.tar.xz |
Merge tag 'net-next-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
Pull networking updates from Paolo Abeni:
"Core:
- Allow live renaming when an interface is up
- Add retpoline wrappers for tc, improving considerably the
performances of complex queue discipline configurations
- Add inet drop monitor support
- A few GRO performance improvements
- Add infrastructure for atomic dev stats, addressing long standing
data races
- De-duplicate common code between OVS and conntrack offloading
infrastructure
- A bunch of UBSAN_BOUNDS/FORTIFY_SOURCE improvements
- Netfilter: introduce packet parser for tunneled packets
- Replace IPVS timer-based estimators with kthreads to scale up the
workload with the number of available CPUs
- Add the helper support for connection-tracking OVS offload
BPF:
- Support for user defined BPF objects: the use case is to allocate
own objects, build own object hierarchies and use the building
blocks to build own data structures flexibly, for example, linked
lists in BPF
- Make cgroup local storage available to non-cgroup attached BPF
programs
- Avoid unnecessary deadlock detection and failures wrt BPF task
storage helpers
- A relevant bunch of BPF verifier fixes and improvements
- Veristat tool improvements to support custom filtering, sorting,
and replay of results
- Add LLVM disassembler as default library for dumping JITed code
- Lots of new BPF documentation for various BPF maps
- Add bpf_rcu_read_{,un}lock() support for sleepable programs
- Add RCU grace period chaining to BPF to wait for the completion of
access from both sleepable and non-sleepable BPF programs
- Add support storing struct task_struct objects as kptrs in maps
- Improve helper UAPI by explicitly defining BPF_FUNC_xxx integer
values
- Add libbpf *_opts API-variants for bpf_*_get_fd_by_id() functions
Protocols:
- TCP: implement Protective Load Balancing across switch links
- TCP: allow dynamically disabling TCP-MD5 static key, reverting back
to fast[er]-path
- UDP: Introduce optional per-netns hash lookup table
- IPv6: simplify and cleanup sockets disposal
- Netlink: support different type policies for each generic netlink
operation
- MPTCP: add MSG_FASTOPEN and FastOpen listener side support
- MPTCP: add netlink notification support for listener sockets events
- SCTP: add VRF support, allowing sctp sockets binding to VRF devices
- Add bridging MAC Authentication Bypass (MAB) support
- Extensions for Ethernet VPN bridging implementation to better
support multicast scenarios
- More work for Wi-Fi 7 support, comprising conversion of all the
existing drivers to internal TX queue usage
- IPSec: introduce a new offload type (packet offload) allowing
complete header processing and crypto offloading
- IPSec: extended ack support for more descriptive XFRM error
reporting
- RXRPC: increase SACK table size and move processing into a
per-local endpoint kernel thread, reducing considerably the
required locking
- IEEE 802154: synchronous send frame and extended filtering support,
initial support for scanning available 15.4 networks
- Tun: bump the link speed from 10Mbps to 10Gbps
- Tun/VirtioNet: implement UDP segmentation offload support
Driver API:
- PHY/SFP: improve power level switching between standard level 1 and
the higher power levels
- New API for netdev <-> devlink_port linkage
- PTP: convert existing drivers to new frequency adjustment
implementation
- DSA: add support for rx offloading
- Autoload DSA tagging driver when dynamically changing protocol
- Add new PCP and APPTRUST attributes to Data Center Bridging
- Add configuration support for 800Gbps link speed
- Add devlink port function attribute to enable/disable RoCE and
migratable
- Extend devlink-rate to support strict prioriry and weighted fair
queuing
- Add devlink support to directly reading from region memory
- New device tree helper to fetch MAC address from nvmem
- New big TCP helper to simplify temporary header stripping
New hardware / drivers:
- Ethernet:
- Marvel Octeon CNF95N and CN10KB Ethernet Switches
- Marvel Prestera AC5X Ethernet Switch
- WangXun 10 Gigabit NIC
- Motorcomm yt8521 Gigabit Ethernet
- Microchip ksz9563 Gigabit Ethernet Switch
- Microsoft Azure Network Adapter
- Linux Automation 10Base-T1L adapter
- PHY:
- Aquantia AQR112 and AQR412
- Motorcomm YT8531S
- PTP:
- Orolia ART-CARD
- WiFi:
- MediaTek Wi-Fi 7 (802.11be) devices
- RealTek rtw8821cu, rtw8822bu, rtw8822cu and rtw8723du USB
devices
- Bluetooth:
- Broadcom BCM4377/4378/4387 Bluetooth chipsets
- Realtek RTL8852BE and RTL8723DS
- Cypress.CYW4373A0 WiFi + Bluetooth combo device
Drivers:
- CAN:
- gs_usb: bus error reporting support
- kvaser_usb: listen only and bus error reporting support
- Ethernet NICs:
- Intel (100G):
- extend action skbedit to RX queue mapping
- implement devlink-rate support
- support direct read from memory
- nVidia/Mellanox (mlx5):
- SW steering improvements, increasing rules update rate
- Support for enhanced events compression
- extend H/W offload packet manipulation capabilities
- implement IPSec packet offload mode
- nVidia/Mellanox (mlx4):
- better big TCP support
- Netronome Ethernet NICs (nfp):
- IPsec offload support
- add support for multicast filter
- Broadcom:
- RSS and PTP support improvements
- AMD/SolarFlare:
- netlink extened ack improvements
- add basic flower matches to offload, and related stats
- Virtual NICs:
- ibmvnic: introduce affinity hint support
- small / embedded:
- FreeScale fec: add initial XDP support
- Marvel mv643xx_eth: support MII/GMII/RGMII modes for Kirkwood
- TI am65-cpsw: add suspend/resume support
- Mediatek MT7986: add RX wireless wthernet dispatch support
- Realtek 8169: enable GRO software interrupt coalescing per
default
- Ethernet high-speed switches:
- Microchip (sparx5):
- add support for Sparx5 TC/flower H/W offload via VCAP
- Mellanox mlxsw:
- add 802.1X and MAC Authentication Bypass offload support
- add ip6gre support
- Embedded Ethernet switches:
- Mediatek (mtk_eth_soc):
- improve PCS implementation, add DSA untag support
- enable flow offload support
- Renesas:
- add rswitch R-Car Gen4 gPTP support
- Microchip (lan966x):
- add full XDP support
- add TC H/W offload via VCAP
- enable PTP on bridge interfaces
- Microchip (ksz8):
- add MTU support for KSZ8 series
- Qualcomm 802.11ax WiFi (ath11k):
- support configuring channel dwell time during scan
- MediaTek WiFi (mt76):
- enable Wireless Ethernet Dispatch (WED) offload support
- add ack signal support
- enable coredump support
- remain_on_channel support
- Intel WiFi (iwlwifi):
- enable Wi-Fi 7 Extremely High Throughput (EHT) PHY capabilities
- 320 MHz channels support
- RealTek WiFi (rtw89):
- new dynamic header firmware format support
- wake-over-WLAN support"
* tag 'net-next-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2002 commits)
ipvs: fix type warning in do_div() on 32 bit
net: lan966x: Remove a useless test in lan966x_ptp_add_trap()
net: ipa: add IPA v4.7 support
dt-bindings: net: qcom,ipa: Add SM6350 compatible
bnxt: Use generic HBH removal helper in tx path
IPv6/GRO: generic helper to remove temporary HBH/jumbo header in driver
selftests: forwarding: Add bridge MDB test
selftests: forwarding: Rename bridge_mdb test
bridge: mcast: Support replacement of MDB port group entries
bridge: mcast: Allow user space to specify MDB entry routing protocol
bridge: mcast: Allow user space to add (*, G) with a source list and filter mode
bridge: mcast: Add support for (*, G) with a source list and filter mode
bridge: mcast: Avoid arming group timer when (S, G) corresponds to a source
bridge: mcast: Add a flag for user installed source entries
bridge: mcast: Expose __br_multicast_del_group_src()
bridge: mcast: Expose br_multicast_new_group_src()
bridge: mcast: Add a centralized error path
bridge: mcast: Place netlink policy before validation functions
bridge: mcast: Split (*, G) and (S, G) addition into different functions
bridge: mcast: Do not derive entry type from its filter mode
...
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 000000000000..f2f51a53e8ae --- /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. |