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().
  ...

1 files changed, 539 insertions, 0 deletions

diff --git a/Documentation/networking/tls-offload.rst b/Documentation/networking/tls-offload.rst
new file mode 100644
index 000000000..5f0dea3d5
--- /dev/null
+++ b/Documentation/networking/tls-offload.rst
@@ -0,0 +1,539 @@
+.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+
+==================
+Kernel TLS offload
+==================
+
+Kernel TLS operation
+====================
+
+Linux kernel provides TLS connection offload infrastructure. Once a TCP
+connection is in ``ESTABLISHED`` state user space can enable the TLS Upper
+Layer Protocol (ULP) and install the cryptographic connection state.
+For details regarding the user-facing interface refer to the TLS
+documentation in :ref:`Documentation/networking/tls.rst <kernel_tls>`.
+
+``ktls`` can operate in three modes:
+
+ * Software crypto mode (``TLS_SW``) - CPU handles the cryptography.
+   In most basic cases only crypto operations synchronous with the CPU
+   can be used, but depending on calling context CPU may utilize
+   asynchronous crypto accelerators. The use of accelerators introduces extra
+   latency on socket reads (decryption only starts when a read syscall
+   is made) and additional I/O load on the system.
+ * Packet-based NIC offload mode (``TLS_HW``) - the NIC handles crypto
+   on a packet by packet basis, provided the packets arrive in order.
+   This mode integrates best with the kernel stack and is described in detail
+   in the remaining part of this document
+   (``ethtool`` flags ``tls-hw-tx-offload`` and ``tls-hw-rx-offload``).
+ * Full TCP NIC offload mode (``TLS_HW_RECORD``) - mode of operation where
+   NIC driver and firmware replace the kernel networking stack
+   with its own TCP handling, it is not usable in production environments
+   making use of the Linux networking stack for example any firewalling
+   abilities or QoS and packet scheduling (``ethtool`` flag ``tls-hw-record``).
+
+The operation mode is selected automatically based on device configuration,
+offload opt-in or opt-out on per-connection basis is not currently supported.
+
+TX
+--
+
+At a high level user write requests are turned into a scatter list, the TLS ULP
+intercepts them, inserts record framing, performs encryption (in ``TLS_SW``
+mode) and then hands the modified scatter list to the TCP layer. From this
+point on the TCP stack proceeds as normal.
+
+In ``TLS_HW`` mode the encryption is not performed in the TLS ULP.
+Instead packets reach a device driver, the driver will mark the packets
+for crypto offload based on the socket the packet is attached to,
+and send them to the device for encryption and transmission.
+
+RX
+--
+
+On the receive side if the device handled decryption and authentication
+successfully, the driver will set the decrypted bit in the associated
+:c:type:`struct sk_buff <sk_buff>`. The packets reach the TCP stack and
+are handled normally. ``ktls`` is informed when data is queued to the socket
+and the ``strparser`` mechanism is used to delineate the records. Upon read
+request, records are retrieved from the socket and passed to decryption routine.
+If device decrypted all the segments of the record the decryption is skipped,
+otherwise software path handles decryption.
+
+.. kernel-figure::  tls-offload-layers.svg
+   :alt:	TLS offload layers
+   :align:	center
+   :figwidth:	28em
+
+   Layers of Kernel TLS stack
+
+Device configuration
+====================
+
+During driver initialization device sets the ``NETIF_F_HW_TLS_RX`` and
+``NETIF_F_HW_TLS_TX`` features and installs its
+:c:type:`struct tlsdev_ops <tlsdev_ops>`
+pointer in the :c:member:`tlsdev_ops` member of the
+:c:type:`struct net_device <net_device>`.
+
+When TLS cryptographic connection state is installed on a ``ktls`` socket
+(note that it is done twice, once for RX and once for TX direction,
+and the two are completely independent), the kernel checks if the underlying
+network device is offload-capable and attempts the offload. In case offload
+fails the connection is handled entirely in software using the same mechanism
+as if the offload was never tried.
+
+Offload request is performed via the :c:member:`tls_dev_add` callback of
+:c:type:`struct tlsdev_ops <tlsdev_ops>`:
+
+.. code-block:: c
+
+	int (*tls_dev_add)(struct net_device *netdev, struct sock *sk,
+			   enum tls_offload_ctx_dir direction,
+			   struct tls_crypto_info *crypto_info,
+			   u32 start_offload_tcp_sn);
+
+``direction`` indicates whether the cryptographic information is for
+the received or transmitted packets. Driver uses the ``sk`` parameter
+to retrieve the connection 5-tuple and socket family (IPv4 vs IPv6).
+Cryptographic information in ``crypto_info`` includes the key, iv, salt
+as well as TLS record sequence number. ``start_offload_tcp_sn`` indicates
+which TCP sequence number corresponds to the beginning of the record with
+sequence number from ``crypto_info``. The driver can add its state
+at the end of kernel structures (see :c:member:`driver_state` members
+in ``include/net/tls.h``) to avoid additional allocations and pointer
+dereferences.
+
+TX
+--
+
+After TX state is installed, the stack guarantees that the first segment
+of the stream will start exactly at the ``start_offload_tcp_sn`` sequence
+number, simplifying TCP sequence number matching.
+
+TX offload being fully initialized does not imply that all segments passing
+through the driver and which belong to the offloaded socket will be after
+the expected sequence number and will have kernel record information.
+In particular, already encrypted data may have been queued to the socket
+before installing the connection state in the kernel.
+
+RX
+--
+
+In RX direction local networking stack has little control over the segmentation,
+so the initial records' TCP sequence number may be anywhere inside the segment.
+
+Normal operation
+================
+
+At the minimum the device maintains the following state for each connection, in
+each direction:
+
+ * crypto secrets (key, iv, salt)
+ * crypto processing state (partial blocks, partial authentication tag, etc.)
+ * record metadata (sequence number, processing offset and length)
+ * expected TCP sequence number
+
+There are no guarantees on record length or record segmentation. In particular
+segments may start at any point of a record and contain any number of records.
+Assuming segments are received in order, the device should be able to perform
+crypto operations and authentication regardless of segmentation. For this
+to be possible device has to keep small amount of segment-to-segment state.
+This includes at least:
+
+ * partial headers (if a segment carried only a part of the TLS header)
+ * partial data block
+ * partial authentication tag (all data had been seen but part of the
+   authentication tag has to be written or read from the subsequent segment)
+
+Record reassembly is not necessary for TLS offload. If the packets arrive
+in order the device should be able to handle them separately and make
+forward progress.
+
+TX
+--
+
+The kernel stack performs record framing reserving space for the authentication
+tag and populating all other TLS header and tailer fields.
+
+Both the device and the driver maintain expected TCP sequence numbers
+due to the possibility of retransmissions and the lack of software fallback
+once the packet reaches the device.
+For segments passed in order, the driver marks the packets with
+a connection identifier (note that a 5-tuple lookup is insufficient to identify
+packets requiring HW offload, see the :ref:`5tuple_problems` section)
+and hands them to the device. The device identifies the packet as requiring
+TLS handling and confirms the sequence number matches its expectation.
+The device performs encryption and authentication of the record data.
+It replaces the authentication tag and TCP checksum with correct values.
+
+RX
+--
+
+Before a packet is DMAed to the host (but after NIC's embedded switching
+and packet transformation functions) the device validates the Layer 4
+checksum and performs a 5-tuple lookup to find any TLS connection the packet
+may belong to (technically a 4-tuple
+lookup is sufficient - IP addresses and TCP port numbers, as the protocol
+is always TCP). If connection is matched device confirms if the TCP sequence
+number is the expected one and proceeds to TLS handling (record delineation,
+decryption, authentication for each record in the packet). The device leaves
+the record framing unmodified, the stack takes care of record decapsulation.
+Device indicates successful handling of TLS offload in the per-packet context
+(descriptor) passed to the host.
+
+Upon reception of a TLS offloaded packet, the driver sets
+the :c:member:`decrypted` mark in :c:type:`struct sk_buff <sk_buff>`
+corresponding to the segment. Networking stack makes sure decrypted
+and non-decrypted segments do not get coalesced (e.g. by GRO or socket layer)
+and takes care of partial decryption.
+
+Resync handling
+===============
+
+In presence of packet drops or network packet reordering, the device may lose
+synchronization with the TLS stream, and require a resync with the kernel's
+TCP stack.
+
+Note that resync is only attempted for connections which were successfully
+added to the device table and are in TLS_HW mode. For example,
+if the table was full when cryptographic state was installed in the kernel,
+such connection will never get offloaded. Therefore the resync request
+does not carry any cryptographic connection state.
+
+TX
+--
+
+Segments transmitted from an offloaded socket can get out of sync
+in similar ways to the receive side-retransmissions - local drops
+are possible, though network reorders are not. There are currently
+two mechanisms for dealing with out of order segments.
+
+Crypto state rebuilding
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Whenever an out of order segment is transmitted the driver provides
+the device with enough information to perform cryptographic operations.
+This means most likely that the part of the record preceding the current
+segment has to be passed to the device as part of the packet context,
+together with its TCP sequence number and TLS record number. The device
+can then initialize its crypto state, process and discard the preceding
+data (to be able to insert the authentication tag) and move onto handling
+the actual packet.
+
+In this mode depending on the implementation the driver can either ask
+for a continuation with the crypto state and the new sequence number
+(next expected segment is the one after the out of order one), or continue
+with the previous stream state - assuming that the out of order segment
+was just a retransmission. The former is simpler, and does not require
+retransmission detection therefore it is the recommended method until
+such time it is proven inefficient.
+
+Next record sync
+~~~~~~~~~~~~~~~~
+
+Whenever an out of order segment is detected the driver requests
+that the ``ktls`` software fallback code encrypt it. If the segment's
+sequence number is lower than expected the driver assumes retransmission
+and doesn't change device state. If the segment is in the future, it
+may imply a local drop, the driver asks the stack to sync the device
+to the next record state and falls back to software.
+
+Resync request is indicated with:
+
+.. code-block:: c
+
+  void tls_offload_tx_resync_request(struct sock *sk, u32 got_seq, u32 exp_seq)
+
+Until resync is complete driver should not access its expected TCP
+sequence number (as it will be updated from a different context).
+Following helper should be used to test if resync is complete:
+
+.. code-block:: c
+
+  bool tls_offload_tx_resync_pending(struct sock *sk)
+
+Next time ``ktls`` pushes a record it will first send its TCP sequence number
+and TLS record number to the driver. Stack will also make sure that
+the new record will start on a segment boundary (like it does when
+the connection is initially added).
+
+RX
+--
+
+A small amount of RX reorder events may not require a full resynchronization.
+In particular the device should not lose synchronization
+when record boundary can be recovered:
+
+.. kernel-figure::  tls-offload-reorder-good.svg
+   :alt:	reorder of non-header segment
+   :align:	center
+
+   Reorder of non-header segment
+
+Green segments are successfully decrypted, blue ones are passed
+as received on wire, red stripes mark start of new records.
+
+In above case segment 1 is received and decrypted successfully.
+Segment 2 was dropped so 3 arrives out of order. The device knows
+the next record starts inside 3, based on record length in segment 1.
+Segment 3 is passed untouched, because due to lack of data from segment 2
+the remainder of the previous record inside segment 3 cannot be handled.
+The device can, however, collect the authentication algorithm's state
+and partial block from the new record in segment 3 and when 4 and 5
+arrive continue decryption. Finally when 2 arrives it's completely outside
+of expected window of the device so it's passed as is without special
+handling. ``ktls`` software fallback handles the decryption of record
+spanning segments 1, 2 and 3. The device did not get out of sync,
+even though two segments did not get decrypted.
+
+Kernel synchronization may be necessary if the lost segment contained
+a record header and arrived after the next record header has already passed:
+
+.. kernel-figure::  tls-offload-reorder-bad.svg
+   :alt:	reorder of header segment
+   :align:	center
+
+   Reorder of segment with a TLS header
+
+In this example segment 2 gets dropped, and it contains a record header.
+Device can only detect that segment 4 also contains a TLS header
+if it knows the length of the previous record from segment 2. In this case
+the device will lose synchronization with the stream.
+
+Stream scan resynchronization
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When the device gets out of sync and the stream reaches TCP sequence
+numbers more than a max size record past the expected TCP sequence number,
+the device starts scanning for a known header pattern. For example
+for TLS 1.2 and TLS 1.3 subsequent bytes of value ``0x03 0x03`` occur
+in the SSL/TLS version field of the header. Once pattern is matched
+the device continues attempting parsing headers at expected locations
+(based on the length fields at guessed locations).
+Whenever the expected location does not contain a valid header the scan
+is restarted.
+
+When the header is matched the device sends a confirmation request
+to the kernel, asking if the guessed location is correct (if a TLS record
+really starts there), and which record sequence number the given header had.
+The kernel confirms the guessed location was correct and tells the device
+the record sequence number. Meanwhile, the device had been parsing
+and counting all records since the just-confirmed one, it adds the number
+of records it had seen to the record number provided by the kernel.
+At this point the device is in sync and can resume decryption at next
+segment boundary.
+
+In a pathological case the device may latch onto a sequence of matching
+headers and never hear back from the kernel (there is no negative
+confirmation from the kernel). The implementation may choose to periodically
+restart scan. Given how unlikely falsely-matching stream is, however,
+periodic restart is not deemed necessary.
+
+Special care has to be taken if the confirmation request is passed
+asynchronously to the packet stream and record may get processed
+by the kernel before the confirmation request.
+
+Stack-driven resynchronization
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The driver may also request the stack to perform resynchronization
+whenever it sees the records are no longer getting decrypted.
+If the connection is configured in this mode the stack automatically
+schedules resynchronization after it has received two completely encrypted
+records.
+
+The stack waits for the socket to drain and informs the device about
+the next expected record number and its TCP sequence number. If the
+records continue to be received fully encrypted stack retries the
+synchronization with an exponential back off (first after 2 encrypted
+records, then after 4 records, after 8, after 16... up until every
+128 records).
+
+Error handling
+==============
+
+TX
+--
+
+Packets may be redirected or rerouted by the stack to a different
+device than the selected TLS offload device. The stack will handle
+such condition using the :c:func:`sk_validate_xmit_skb` helper
+(TLS offload code installs :c:func:`tls_validate_xmit_skb` at this hook).
+Offload maintains information about all records until the data is
+fully acknowledged, so if skbs reach the wrong device they can be handled
+by software fallback.
+
+Any device TLS offload handling error on the transmission side must result
+in the packet being dropped. For example if a packet got out of order
+due to a bug in the stack or the device, reached the device and can't
+be encrypted such packet must be dropped.
+
+RX
+--
+
+If the device encounters any problems with TLS offload on the receive
+side it should pass the packet to the host's networking stack as it was
+received on the wire.
+
+For example authentication failure for any record in the segment should
+result in passing the unmodified packet to the software fallback. This means
+packets should not be modified "in place". Splitting segments to handle partial
+decryption is not advised. In other words either all records in the packet
+had been handled successfully and authenticated or the packet has to be passed
+to the host's stack as it was on the wire (recovering original packet in the
+driver if device provides precise error is sufficient).
+
+The Linux networking stack does not provide a way of reporting per-packet
+decryption and authentication errors, packets with errors must simply not
+have the :c:member:`decrypted` mark set.
+
+A packet should also not be handled by the TLS offload if it contains
+incorrect checksums.
+
+Performance metrics
+===================
+
+TLS offload can be characterized by the following basic metrics:
+
+ * max connection count
+ * connection installation rate
+ * connection installation latency
+ * total cryptographic performance
+
+Note that each TCP connection requires a TLS session in both directions,
+the performance may be reported treating each direction separately.
+
+Max connection count
+--------------------
+
+The number of connections device can support can be exposed via
+``devlink resource`` API.
+
+Total cryptographic performance
+-------------------------------
+
+Offload performance may depend on segment and record size.
+
+Overload of the cryptographic subsystem of the device should not have
+significant performance impact on non-offloaded streams.
+
+Statistics
+==========
+
+Following minimum set of TLS-related statistics should be reported
+by the driver:
+
+ * ``rx_tls_decrypted_packets`` - number of successfully decrypted RX packets
+   which were part of a TLS stream.
+ * ``rx_tls_decrypted_bytes`` - number of TLS payload bytes in RX packets
+   which were successfully decrypted.
+ * ``rx_tls_ctx`` - number of TLS RX HW offload contexts added to device for
+   decryption.
+ * ``rx_tls_del`` - number of TLS RX HW offload contexts deleted from device
+   (connection has finished).
+ * ``rx_tls_resync_req_pkt`` - number of received TLS packets with a resync
+    request.
+ * ``rx_tls_resync_req_start`` - number of times the TLS async resync request
+    was started.
+ * ``rx_tls_resync_req_end`` - number of times the TLS async resync request
+    properly ended with providing the HW tracked tcp-seq.
+ * ``rx_tls_resync_req_skip`` - number of times the TLS async resync request
+    procedure was started by not properly ended.
+ * ``rx_tls_resync_res_ok`` - number of times the TLS resync response call to
+    the driver was successfully handled.
+ * ``rx_tls_resync_res_skip`` - number of times the TLS resync response call to
+    the driver was terminated unsuccessfully.
+ * ``rx_tls_err`` - number of RX packets which were part of a TLS stream
+   but were not decrypted due to unexpected error in the state machine.
+ * ``tx_tls_encrypted_packets`` - number of TX packets passed to the device
+   for encryption of their TLS payload.
+ * ``tx_tls_encrypted_bytes`` - number of TLS payload bytes in TX packets
+   passed to the device for encryption.
+ * ``tx_tls_ctx`` - number of TLS TX HW offload contexts added to device for
+   encryption.
+ * ``tx_tls_ooo`` - number of TX packets which were part of a TLS stream
+   but did not arrive in the expected order.
+ * ``tx_tls_skip_no_sync_data`` - number of TX packets which were part of
+   a TLS stream and arrived out-of-order, but skipped the HW offload routine
+   and went to the regular transmit flow as they were retransmissions of the
+   connection handshake.
+ * ``tx_tls_drop_no_sync_data`` - number of TX packets which were part of
+   a TLS stream dropped, because they arrived out of order and associated
+   record could not be found.
+ * ``tx_tls_drop_bypass_req`` - number of TX packets which were part of a TLS
+   stream dropped, because they contain both data that has been encrypted by
+   software and data that expects hardware crypto offload.
+
+Notable corner cases, exceptions and additional requirements
+============================================================
+
+.. _5tuple_problems:
+
+5-tuple matching limitations
+----------------------------
+
+The device can only recognize received packets based on the 5-tuple
+of the socket. Current ``ktls`` implementation will not offload sockets
+routed through software interfaces such as those used for tunneling
+or virtual networking. However, many packet transformations performed
+by the networking stack (most notably any BPF logic) do not require
+any intermediate software device, therefore a 5-tuple match may
+consistently miss at the device level. In such cases the device
+should still be able to perform TX offload (encryption) and should
+fallback cleanly to software decryption (RX).
+
+Out of order
+------------
+
+Introducing extra processing in NICs should not cause packets to be
+transmitted or received out of order, for example pure ACK packets
+should not be reordered with respect to data segments.
+
+Ingress reorder
+---------------
+
+A device is permitted to perform packet reordering for consecutive
+TCP segments (i.e. placing packets in the correct order) but any form
+of additional buffering is disallowed.
+
+Coexistence with standard networking offload features
+-----------------------------------------------------
+
+Offloaded ``ktls`` sockets should support standard TCP stack features
+transparently. Enabling device TLS offload should not cause any difference
+in packets as seen on the wire.
+
+Transport layer transparency
+----------------------------
+
+The device should not modify any packet headers for the purpose
+of the simplifying TLS offload.
+
+The device should not depend on any packet headers beyond what is strictly
+necessary for TLS offload.
+
+Segment drops
+-------------
+
+Dropping packets is acceptable only in the event of catastrophic
+system errors and should never be used as an error handling mechanism
+in cases arising from normal operation. In other words, reliance
+on TCP retransmissions to handle corner cases is not acceptable.
+
+TLS device features
+-------------------
+
+Drivers should ignore the changes to the TLS device feature flags.
+These flags will be acted upon accordingly by the core ``ktls`` code.
+TLS device feature flags only control adding of new TLS connection
+offloads, old connections will remain active after flags are cleared.
+
+TLS encryption cannot be offloaded to devices without checksum calculation
+offload. Hence, TLS TX device feature flag requires TX csum offload being set.
+Disabling the latter implies clearing the former. Disabling TX checksum offload
+should not affect old connections, and drivers should make sure checksum
+calculation does not break for them.
+Similarly, device-offloaded TLS decryption implies doing RXCSUM. If the user
+does not want to enable RX csum offload, TLS RX device feature is disabled
+as well.