diff options
author | 2023-02-21 18:24:12 -0800 | |
---|---|---|
committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/networking/mctp.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/networking/mctp.rst')
-rw-r--r-- | Documentation/networking/mctp.rst | 320 |
1 files changed, 320 insertions, 0 deletions
diff --git a/Documentation/networking/mctp.rst b/Documentation/networking/mctp.rst new file mode 100644 index 000000000..c628cb540 --- /dev/null +++ b/Documentation/networking/mctp.rst @@ -0,0 +1,320 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================================== +Management Component Transport Protocol (MCTP) +============================================== + +net/mctp/ contains protocol support for MCTP, as defined by DMTF standard +DSP0236. Physical interface drivers ("bindings" in the specification) are +provided in drivers/net/mctp/. + +The core code provides a socket-based interface to send and receive MCTP +messages, through an AF_MCTP, SOCK_DGRAM socket. + +Structure: interfaces & networks +================================ + +The kernel models the local MCTP topology through two items: interfaces and +networks. + +An interface (or "link") is an instance of an MCTP physical transport binding +(as defined by DSP0236, section 3.2.47), likely connected to a specific hardware +device. This is represented as a ``struct netdevice``. + +A network defines a unique address space for MCTP endpoints by endpoint-ID +(described by DSP0236, section 3.2.31). A network has a user-visible identifier +to allow references from userspace. Route definitions are specific to one +network. + +Interfaces are associated with one network. A network may be associated with one +or more interfaces. + +If multiple networks are present, each may contain endpoint IDs (EIDs) that are +also present on other networks. + +Sockets API +=========== + +Protocol definitions +-------------------- + +MCTP uses ``AF_MCTP`` / ``PF_MCTP`` for the address- and protocol- families. +Since MCTP is message-based, only ``SOCK_DGRAM`` sockets are supported. + +.. code-block:: C + + int sd = socket(AF_MCTP, SOCK_DGRAM, 0); + +The only (current) value for the ``protocol`` argument is 0. + +As with all socket address families, source and destination addresses are +specified with a ``sockaddr`` type, with a single-byte endpoint address: + +.. code-block:: C + + typedef __u8 mctp_eid_t; + + struct mctp_addr { + mctp_eid_t s_addr; + }; + + struct sockaddr_mctp { + __kernel_sa_family_t smctp_family; + unsigned int smctp_network; + struct mctp_addr smctp_addr; + __u8 smctp_type; + __u8 smctp_tag; + }; + + #define MCTP_NET_ANY 0x0 + #define MCTP_ADDR_ANY 0xff + + +Syscall behaviour +----------------- + +The following sections describe the MCTP-specific behaviours of the standard +socket system calls. These behaviours have been chosen to map closely to the +existing sockets APIs. + +``bind()`` : set local socket address +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Sockets that receive incoming request packets will bind to a local address, +using the ``bind()`` syscall. + +.. code-block:: C + + struct sockaddr_mctp addr; + + addr.smctp_family = AF_MCTP; + addr.smctp_network = MCTP_NET_ANY; + addr.smctp_addr.s_addr = MCTP_ADDR_ANY; + addr.smctp_type = MCTP_TYPE_PLDM; + addr.smctp_tag = MCTP_TAG_OWNER; + + int rc = bind(sd, (struct sockaddr *)&addr, sizeof(addr)); + +This establishes the local address of the socket. Incoming MCTP messages that +match the network, address, and message type will be received by this socket. +The reference to 'incoming' is important here; a bound socket will only receive +messages with the TO bit set, to indicate an incoming request message, rather +than a response. + +The ``smctp_tag`` value will configure the tags accepted from the remote side of +this socket. Given the above, the only valid value is ``MCTP_TAG_OWNER``, which +will result in remotely "owned" tags being routed to this socket. Since +``MCTP_TAG_OWNER`` is set, the 3 least-significant bits of ``smctp_tag`` are not +used; callers must set them to zero. + +A ``smctp_network`` value of ``MCTP_NET_ANY`` will configure the socket to +receive incoming packets from any locally-connected network. A specific network +value will cause the socket to only receive incoming messages from that network. + +The ``smctp_addr`` field specifies a local address to bind to. A value of +``MCTP_ADDR_ANY`` configures the socket to receive messages addressed to any +local destination EID. + +The ``smctp_type`` field specifies which message types to receive. Only the +lower 7 bits of the type is matched on incoming messages (ie., the +most-significant IC bit is not part of the match). This results in the socket +receiving packets with and without a message integrity check footer. + +``sendto()``, ``sendmsg()``, ``send()`` : transmit an MCTP message +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +An MCTP message is transmitted using one of the ``sendto()``, ``sendmsg()`` or +``send()`` syscalls. Using ``sendto()`` as the primary example: + +.. code-block:: C + + struct sockaddr_mctp addr; + char buf[14]; + ssize_t len; + + /* set message destination */ + addr.smctp_family = AF_MCTP; + addr.smctp_network = 0; + addr.smctp_addr.s_addr = 8; + addr.smctp_tag = MCTP_TAG_OWNER; + addr.smctp_type = MCTP_TYPE_ECHO; + + /* arbitrary message to send, with message-type header */ + buf[0] = MCTP_TYPE_ECHO; + memcpy(buf + 1, "hello, world!", sizeof(buf) - 1); + + len = sendto(sd, buf, sizeof(buf), 0, + (struct sockaddr_mctp *)&addr, sizeof(addr)); + +The network and address fields of ``addr`` define the remote address to send to. +If ``smctp_tag`` has the ``MCTP_TAG_OWNER``, the kernel will ignore any bits set +in ``MCTP_TAG_VALUE``, and generate a tag value suitable for the destination +EID. If ``MCTP_TAG_OWNER`` is not set, the message will be sent with the tag +value as specified. If a tag value cannot be allocated, the system call will +report an errno of ``EAGAIN``. + +The application must provide the message type byte as the first byte of the +message buffer passed to ``sendto()``. If a message integrity check is to be +included in the transmitted message, it must also be provided in the message +buffer, and the most-significant bit of the message type byte must be 1. + +The ``sendmsg()`` system call allows a more compact argument interface, and the +message buffer to be specified as a scatter-gather list. At present no ancillary +message types (used for the ``msg_control`` data passed to ``sendmsg()``) are +defined. + +Transmitting a message on an unconnected socket with ``MCTP_TAG_OWNER`` +specified will cause an allocation of a tag, if no valid tag is already +allocated for that destination. The (destination-eid,tag) tuple acts as an +implicit local socket address, to allow the socket to receive responses to this +outgoing message. If any previous allocation has been performed (to for a +different remote EID), that allocation is lost. + +Sockets will only receive responses to requests they have sent (with TO=1) and +may only respond (with TO=0) to requests they have received. + +``recvfrom()``, ``recvmsg()``, ``recv()`` : receive an MCTP message +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +An MCTP message can be received by an application using one of the +``recvfrom()``, ``recvmsg()``, or ``recv()`` system calls. Using ``recvfrom()`` +as the primary example: + +.. code-block:: C + + struct sockaddr_mctp addr; + socklen_t addrlen; + char buf[14]; + ssize_t len; + + addrlen = sizeof(addr); + + len = recvfrom(sd, buf, sizeof(buf), 0, + (struct sockaddr_mctp *)&addr, &addrlen); + + /* We can expect addr to describe an MCTP address */ + assert(addrlen >= sizeof(buf)); + assert(addr.smctp_family == AF_MCTP); + + printf("received %zd bytes from remote EID %d\n", rc, addr.smctp_addr); + +The address argument to ``recvfrom`` and ``recvmsg`` is populated with the +remote address of the incoming message, including tag value (this will be needed +in order to reply to the message). + +The first byte of the message buffer will contain the message type byte. If an +integrity check follows the message, it will be included in the received buffer. + +The ``recv()`` system call behaves in a similar way, but does not provide a +remote address to the application. Therefore, these are only useful if the +remote address is already known, or the message does not require a reply. + +Like the send calls, sockets will only receive responses to requests they have +sent (TO=1) and may only respond (TO=0) to requests they have received. + +``ioctl(SIOCMCTPALLOCTAG)`` and ``ioctl(SIOCMCTPDROPTAG)`` +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +These tags give applications more control over MCTP message tags, by allocating +(and dropping) tag values explicitly, rather than the kernel automatically +allocating a per-message tag at ``sendmsg()`` time. + +In general, you will only need to use these ioctls if your MCTP protocol does +not fit the usual request/response model. For example, if you need to persist +tags across multiple requests, or a request may generate more than one response. +In these cases, the ioctls allow you to decouple the tag allocation (and +release) from individual message send and receive operations. + +Both ioctls are passed a pointer to a ``struct mctp_ioc_tag_ctl``: + +.. code-block:: C + + struct mctp_ioc_tag_ctl { + mctp_eid_t peer_addr; + __u8 tag; + __u16 flags; + }; + +``SIOCMCTPALLOCTAG`` allocates a tag for a specific peer, which an application +can use in future ``sendmsg()`` calls. The application populates the +``peer_addr`` member with the remote EID. Other fields must be zero. + +On return, the ``tag`` member will be populated with the allocated tag value. +The allocated tag will have the following tag bits set: + + - ``MCTP_TAG_OWNER``: it only makes sense to allocate tags if you're the tag + owner + + - ``MCTP_TAG_PREALLOC``: to indicate to ``sendmsg()`` that this is a + preallocated tag. + + - ... and the actual tag value, within the least-significant three bits + (``MCTP_TAG_MASK``). Note that zero is a valid tag value. + +The tag value should be used as-is for the ``smctp_tag`` member of ``struct +sockaddr_mctp``. + +``SIOCMCTPDROPTAG`` releases a tag that has been previously allocated by a +``SIOCMCTPALLOCTAG`` ioctl. The ``peer_addr`` must be the same as used for the +allocation, and the ``tag`` value must match exactly the tag returned from the +allocation (including the ``MCTP_TAG_OWNER`` and ``MCTP_TAG_PREALLOC`` bits). +The ``flags`` field must be zero. + +Kernel internals +================ + +There are a few possible packet flows in the MCTP stack: + +1. local TX to remote endpoint, message <= MTU:: + + sendmsg() + -> mctp_local_output() + : route lookup + -> rt->output() (== mctp_route_output) + -> dev_queue_xmit() + +2. local TX to remote endpoint, message > MTU:: + + sendmsg() + -> mctp_local_output() + -> mctp_do_fragment_route() + : creates packet-sized skbs. For each new skb: + -> rt->output() (== mctp_route_output) + -> dev_queue_xmit() + +3. remote TX to local endpoint, single-packet message:: + + mctp_pkttype_receive() + : route lookup + -> rt->output() (== mctp_route_input) + : sk_key lookup + -> sock_queue_rcv_skb() + +4. remote TX to local endpoint, multiple-packet message:: + + mctp_pkttype_receive() + : route lookup + -> rt->output() (== mctp_route_input) + : sk_key lookup + : stores skb in struct sk_key->reasm_head + + mctp_pkttype_receive() + : route lookup + -> rt->output() (== mctp_route_input) + : sk_key lookup + : finds existing reassembly in sk_key->reasm_head + : appends new fragment + -> sock_queue_rcv_skb() + +Key refcounts +------------- + + * keys are refed by: + + - a skb: during route output, stored in ``skb->cb``. + + - netns and sock lists. + + * keys can be associated with a device, in which case they hold a + reference to the dev (set through ``key->dev``, counted through + ``dev->key_count``). Multiple keys can reference the device. |