ata: libata-scsi: fix ata_dsm_trim_pages() kernel-docgrafted

make htmldocs fails with:

  Documentation/driver-api/libata:604: ./drivers/ata/libata-scsi.c:2301:
  ERROR: Unexpected indentation. [docutils]

The Return: section of ata_dsm_trim_pages() ends its first sentence with
a colon and continues with an indented bullet list. reStructuredText
requires a blank line before an indented block, so docutils chokes on
the list.

Simply adding the missing blank line does not work either: Return: is a
kernel-doc "special section", which is terminated by the first blank
line, so the bullet list would end up in the Description section,
detached from the sentence introducing it.

Spell the two bounds out as prose instead, so that the Return: section
stays self-contained. Documentation-only change.

Fixes: e64e6b5dc867 ("ata: libata-scsi: scale DSM TRIM payload by MAX PAGES PER DSM COMMAND")
Reported-by: Thomas Huth <thuth@redhat.com>
Closes: https://lore.kernel.org/linux-ide/b0a0b8e8-cc4f-4c7b-8bc5-fee0712d405a@redhat.com/
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Link: https://lore.kernel.org/r/20260916130031.29990-2-cassel@kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>

6 files changed, 816 insertions, 0 deletions

diff --git a/Documentation/networking/xfrm/index.rst b/Documentation/networking/xfrm/index.rst
new file mode 100644
index 000000000..90191848f
--- /dev/null
+++ b/Documentation/networking/xfrm/index.rst
@@ -0,0 +1,14 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============
+XFRM Framework
+==============
+
+.. toctree::
+   :maxdepth: 2
+
+   xfrm_device
+   xfrm_proc
+   xfrm_migrate_state
+   xfrm_sync
+   xfrm_sysctl
diff --git a/Documentation/networking/xfrm/xfrm_device.rst b/Documentation/networking/xfrm/xfrm_device.rst
new file mode 100644
index 000000000..b0d85a5f5
--- /dev/null
+++ b/Documentation/networking/xfrm/xfrm_device.rst
@@ -0,0 +1,206 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. _xfrm_device:
+
+===============================================
+XFRM device - offloading the IPsec computations
+===============================================
+
+Shannon Nelson <shannon.nelson@oracle.com>
+Leon Romanovsky <leonro@nvidia.com>
+
+
+Overview
+========
+
+IPsec is a useful feature for securing network traffic, but the
+computational cost is high: a 10Gbps link can easily be brought down
+to under 1Gbps, depending on the traffic and link configuration.
+Luckily, there are NICs that offer a hardware based IPsec offload which
+can radically increase throughput and decrease CPU utilization.  The XFRM
+Device interface allows NIC drivers to offer to the stack access to the
+hardware offload.
+
+Right now, there are two types of hardware offload that kernel supports:
+
+ * IPsec crypto offload:
+
+   * NIC performs encrypt/decrypt
+   * Kernel does everything else
+
+ * IPsec packet offload:
+
+   * NIC performs encrypt/decrypt
+   * NIC does encapsulation
+   * Kernel and NIC have SA and policy in-sync
+   * NIC handles the SA and policies states
+   * The Kernel talks to the keymanager
+
+Userland access to the offload is typically through a system such as
+libreswan or KAME/raccoon, but the iproute2 'ip xfrm' command set can
+be handy when experimenting.  An example command might look something
+like this for crypto offload::
+
+  ip x s add proto esp dst 14.0.0.70 src 14.0.0.52 spi 0x07 mode transport \
+     reqid 0x07 replay-window 32 \
+     aead 'rfc4106(gcm(aes))' 0x44434241343332312423222114131211f4f3f2f1 128 \
+     sel src 14.0.0.52/24 dst 14.0.0.70/24 proto tcp \
+     offload dev eth4 dir in
+
+and for packet offload::
+
+  ip x s add proto esp dst 14.0.0.70 src 14.0.0.52 spi 0x07 mode transport \
+     reqid 0x07 replay-window 32 \
+     aead 'rfc4106(gcm(aes))' 0x44434241343332312423222114131211f4f3f2f1 128 \
+     sel src 14.0.0.52/24 dst 14.0.0.70/24 proto tcp \
+     offload packet dev eth4 dir in
+
+  ip x p add src 14.0.0.70 dst 14.0.0.52 offload packet dev eth4 dir in
+  tmpl src 14.0.0.70 dst 14.0.0.52 proto esp reqid 10000 mode transport
+
+Yes, that's ugly, but that's what shell scripts and/or libreswan are for.
+
+
+
+Callbacks to implement
+======================
+
+::
+
+  /* from include/linux/netdevice.h */
+  struct xfrmdev_ops {
+        /* Crypto and Packet offload callbacks */
+	int	(*xdo_dev_state_add)(struct net_device *dev,
+                                     struct xfrm_state *x,
+                                     struct netlink_ext_ack *extack);
+	void	(*xdo_dev_state_delete)(struct net_device *dev,
+                                        struct xfrm_state *x);
+	void	(*xdo_dev_state_free)(struct net_device *dev,
+                                      struct xfrm_state *x);
+	bool	(*xdo_dev_offload_ok) (struct sk_buff *skb,
+				       struct xfrm_state *x);
+	void    (*xdo_dev_state_advance_esn) (struct xfrm_state *x);
+	void    (*xdo_dev_state_update_stats) (struct xfrm_state *x);
+
+        /* Solely packet offload callbacks */
+	int	(*xdo_dev_policy_add) (struct xfrm_policy *x, struct netlink_ext_ack *extack);
+	void	(*xdo_dev_policy_delete) (struct xfrm_policy *x);
+	void	(*xdo_dev_policy_free) (struct xfrm_policy *x);
+  };
+
+The NIC driver offering ipsec offload will need to implement callbacks
+relevant to supported offload to make the offload available to the network
+stack's XFRM subsystem. Additionally, the feature bits NETIF_F_HW_ESP and
+NETIF_F_HW_ESP_TX_CSUM will signal the availability of the offload.
+
+
+
+Flow
+====
+
+At probe time and before the call to register_netdev(), the driver should
+set up local data structures and XFRM callbacks, and set the feature bits.
+The XFRM code's listener will finish the setup on NETDEV_REGISTER.
+
+::
+
+		adapter->netdev->xfrmdev_ops = &ixgbe_xfrmdev_ops;
+		adapter->netdev->features |= NETIF_F_HW_ESP;
+		adapter->netdev->hw_enc_features |= NETIF_F_HW_ESP;
+
+When new SAs are set up with a request for "offload" feature, the
+driver's xdo_dev_state_add() will be given the new SA to be offloaded
+and an indication of whether it is for Rx or Tx.  The driver should
+
+	- verify the algorithm is supported for offloads
+	- store the SA information (key, salt, target-ip, protocol, etc)
+	- enable the HW offload of the SA
+	- return status value:
+
+		===========   ===================================
+		0             success
+		-EOPNETSUPP   offload not supported, try SW IPsec,
+                              not applicable for packet offload mode
+		other         fail the request
+		===========   ===================================
+
+The driver can also set an offload_handle in the SA, an opaque void pointer
+that can be used to convey context into the fast-path offload requests::
+
+		xs->xso.offload_handle = context;
+
+
+When the network stack is preparing an IPsec packet for an SA that has
+been setup for offload, it first calls into xdo_dev_offload_ok() with
+the skb and the intended offload state to ask the driver if the offload
+will serviceable.  This can check the packet information to be sure the
+offload can be supported (e.g. IPv4 or IPv6, no IPv4 options, etc) and
+return true or false to signify its support. In case driver doesn't implement
+this callback, the stack provides reasonable defaults.
+
+Crypto offload mode:
+When ready to send, the driver needs to inspect the Tx packet for the
+offload information, including the opaque context, and set up the packet
+send accordingly::
+
+		xs = xfrm_input_state(skb);
+		context = xs->xso.offload_handle;
+		set up HW for send
+
+The stack has already inserted the appropriate IPsec headers in the
+packet data, the offload just needs to do the encryption and fix up the
+header values.
+
+
+When a packet is received and the HW has indicated that it offloaded a
+decryption, the driver needs to add a reference to the decoded SA into
+the packet's skb.  At this point the data should be decrypted but the
+IPsec headers are still in the packet data; they are removed later up
+the stack in xfrm_input().
+
+1. Find and hold the SA that was used to the Rx skb::
+
+		/* get spi, protocol, and destination IP from packet headers */
+		xs = find xs from (spi, protocol, dest_IP)
+		xfrm_state_hold(xs);
+
+2. Store the state information into the skb::
+
+		sp = secpath_set(skb);
+		if (!sp) return;
+		sp->xvec[sp->len++] = xs;
+		sp->olen++;
+
+3. Indicate the success and/or error status of the offload::
+
+		xo = xfrm_offload(skb);
+		xo->flags = CRYPTO_DONE;
+		xo->status = crypto_status;
+
+4. Hand the packet to napi_gro_receive() as usual.
+
+In ESN mode, xdo_dev_state_advance_esn() is called from
+xfrm_replay_advance_esn() for RX, and xfrm_replay_overflow_offload_esn for TX.
+Driver will check packet seq number and update HW ESN state machine if needed.
+
+Packet offload mode:
+HW adds and deletes XFRM headers. So in RX path, XFRM stack is bypassed if HW
+reported success. In TX path, the packet lefts kernel without extra header
+and not encrypted, the HW is responsible to perform it.
+
+When the SA is removed by the user, the driver's xdo_dev_state_delete()
+and xdo_dev_policy_delete() are asked to disable the offload.  Later,
+xdo_dev_state_free() and xdo_dev_policy_free() are called from a garbage
+collection routine after all reference counts to the state and policy
+have been removed and any remaining resources can be cleared for the
+offload state.  How these are used by the driver will depend on specific
+hardware needs.
+
+As a netdev is set to DOWN the XFRM stack's netdev listener will call
+xdo_dev_state_delete(), xdo_dev_policy_delete(), xdo_dev_state_free() and
+xdo_dev_policy_free() on any remaining offloaded states.
+
+Outcome of HW handling packets, the XFRM core can't count hard, soft limits.
+The HW/driver are responsible to perform it and provide accurate data when
+xdo_dev_state_update_stats() is called. In case of one of these limits
+occuried, the driver needs to call to xfrm_state_check_expire() to make sure
+that XFRM performs rekeying sequence.
diff --git a/Documentation/networking/xfrm/xfrm_migrate_state.rst b/Documentation/networking/xfrm/xfrm_migrate_state.rst
new file mode 100644
index 000000000..9d53cb22b
--- /dev/null
+++ b/Documentation/networking/xfrm/xfrm_migrate_state.rst
@@ -0,0 +1,274 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================
+XFRM SA Migrate State
+=====================
+
+Overview
+========
+
+``XFRM_MSG_MIGRATE_STATE`` migrates a single SA, looked up using SPI and
+mark, without involving policies. Unlike ``XFRM_MSG_MIGRATE``, which couples
+SA and policy migration and allows migrating multiple SAs in one call, this
+interface identifies the SA unambiguously via SPI and supports changing
+the reqid, addresses, encapsulation, selector, and offload.
+
+Because IKE daemons can manage policies independently of
+the kernel, this interface allows precise per-SA migration without
+requiring policy involvement. Optional netlink attributes follow an
+omit-to-inherit model: omitting an attribute preserves the value from
+the old SA. The ``flags`` field controls two exceptions: hardware offload
+is inherited by default and can be suppressed with
+``XFRM_MIGRATE_STATE_CLEAR_OFFLOAD`` or overridden with ``XFRMA_OFFLOAD_DEV``;
+the new selector is taken from ``new_sel`` by default and can instead be
+derived from the new addresses with ``XFRM_MIGRATE_STATE_UPDATE_H2H_SEL``.
+
+SA Identification
+=================
+
+The struct is defined in ``include/uapi/linux/xfrm.h``. The SA is looked
+up using ``xfrm_state_lookup()`` with ``id.spi``,
+``id.daddr``, ``id.proto``, ``id.family``, and
+``old_mark.v & old_mark.m`` as the mark key::
+
+    struct xfrm_user_migrate_state {
+        struct xfrm_usersa_id  id;       /* spi, daddr, proto, family */
+        xfrm_address_t         new_daddr;
+        xfrm_address_t         new_saddr;
+        struct xfrm_mark       old_mark; /* SA lookup: key = v & m */
+        struct xfrm_selector   new_sel;  /* new selector (see Flags) */
+        __u32                  new_reqid;
+        __u32                  flags;    /* XFRM_MIGRATE_STATE_* */
+        __u16                  new_family;
+        __u16                  reserved;  /* must be zero */
+    };
+
+The ``reserved`` field must be set to zero; the kernel rejects any
+other value with ``-EINVAL``.
+
+Supported Attributes
+====================
+
+The following fields in ``xfrm_user_migrate_state`` are always explicit
+and are not inherited from the existing SA. Passing zero is not equivalent
+to "keep unchanged" — zero is used as-is:
+
+- ``new_daddr`` - new destination address
+- ``new_saddr`` - new source address
+- ``new_family`` - new address family
+- ``new_reqid`` - new reqid (0 = no reqid)
+- ``new_sel`` - new selector; used when ``XFRM_MIGRATE_STATE_UPDATE_H2H_SEL`` is
+  not set (see `Flags`_ below)
+- ``flags`` - bitmask of ``XFRM_MIGRATE_STATE_*`` flags (see `Flags`_ below)
+
+The following netlink attributes are also accepted. Omitting an attribute
+inherits the value from the existing SA (omit-to-inherit).
+
+.. list-table::
+   :widths: 30 70
+   :header-rows: 1
+
+   * - Attribute
+     - Description
+   * - ``XFRMA_MARK``
+     - Mark on the migrated SA (``struct xfrm_mark``). Absent inherits
+       ``old_mark``. To use no mark on the new SA, send ``XFRMA_MARK``
+       with ``{0, 0}``.
+   * - ``XFRMA_ENCAP``
+     - UDP encapsulation template; only ``UDP_ENCAP_ESPINUDP`` is supported.
+       Set ``encap_type=0`` to remove encap.
+   * - ``XFRMA_OFFLOAD_DEV``
+     - Hardware offload configuration (``struct xfrm_user_offload``). Absent
+       copies offload from the existing SA. When
+       ``XFRM_MIGRATE_STATE_CLEAR_OFFLOAD`` is set in ``flags``, the new SA has
+       no offload; this flag is mutually exclusive with ``XFRMA_OFFLOAD_DEV``
+       and sending both returns ``-EINVAL``.
+   * - ``XFRMA_SET_MARK``
+     - Output mark on the migrated SA; pair with ``XFRMA_SET_MARK_MASK``.
+       Send 0 to clear.
+   * - ``XFRMA_NAT_KEEPALIVE_INTERVAL``
+     - NAT keepalive interval in seconds. Requires encap. Send 0 to clear.
+       Automatically cleared when encap is removed; setting a non-zero
+       value without encap returns ``-EINVAL``.
+   * - ``XFRMA_MTIMER_THRESH``
+     - Mapping maxage threshold. Only valid on input SAs; setting on an
+       output SA returns ``-EINVAL``. Requires encap. Send 0 to clear.
+       Automatically cleared when encap is removed; setting a non-zero
+       value without encap returns ``-EINVAL``.
+
+The following SA properties are immutable and cannot be changed via
+``XFRM_MSG_MIGRATE_STATE``: algorithms (``XFRMA_ALG_*``), replay state,
+direction (``XFRMA_SA_DIR``), and security context (``XFRMA_SEC_CTX``).
+
+Flags
+=====
+
+The ``flags`` field in ``xfrm_user_migrate_state`` controls optional
+migration behaviour. Unknown flag bits are rejected with ``-EINVAL``; the
+extended ACK message identifies the unrecognised bits (e.g. ``"Unknown flags:
+0x4"``). Userspace can use ``XFRM_MIGRATE_STATE_KNOWN_FLAGS`` (defined in
+``<linux/xfrm.h>``) to validate flags before sending; note that this constant
+reflects the flags known to the header version userspace was compiled against,
+which may differ from what the running kernel accepts.
+
+.. list-table::
+   :widths: 40 60
+   :header-rows: 1
+
+   * - Flag
+     - Description
+   * - ``XFRM_MIGRATE_STATE_CLEAR_OFFLOAD``
+     - When set, the new SA has no hardware offload even when
+       ``XFRMA_OFFLOAD_DEV`` is absent. Without this flag, omitting
+       ``XFRMA_OFFLOAD_DEV`` copies the existing offload to the new SA.
+       Mutually exclusive with ``XFRMA_OFFLOAD_DEV``; sending both
+       returns ``-EINVAL``.
+   * - ``XFRM_MIGRATE_STATE_UPDATE_H2H_SEL``
+     - When set, the kernel validates that the existing SA selector is a
+       single-host entry matching the SA addresses (``prefixlen_s ==
+       prefixlen_d`` equal to 32 for IPv4 or 128 for IPv6, and addresses
+       matching ``id.daddr`` and ``props.saddr``). If the check passes,
+       the new selector is derived from ``new_daddr`` and ``new_saddr``
+       with the single-host mask for ``new_family``. A mismatch returns
+       ``-EINVAL``. When this flag is not set, ``new_sel`` is used as-is
+       for the migrated SA.
+
+Migration Steps
+===============
+
+Outgoing SA
+-----------
+
+To prevent cleartext traffic leaks, install a block policy before
+migrating:
+
+#. Install a block policy to drop traffic on the affected selector.
+#. Remove the old policy.
+#. Call ``XFRM_MSG_MIGRATE_STATE`` for each SA.
+#. Reinstall the policies.
+#. Remove the block policy.
+
+If AES-GCM is in use, the block policy also prevents IV reuse during
+the migration window. For other AEADs this step is not required for
+IV safety, but skipping it allows a brief cleartext window.
+
+Incoming SA
+-----------
+
+No block policy is needed. ``XFRM_MSG_MIGRATE_STATE`` atomically
+transfers the sequence number and replay window from the old SA to
+the new SA, so the new SA continues replay protection without a gap.
+Call ``XFRM_MSG_MIGRATE_STATE`` for each SA directly.
+
+When accepting incoming traffic, be liberal during the migration
+window: packets sent by the remote peer before it completed its own
+migration may arrive out of order or slightly late. Dropping them
+unnecessarily causes packet loss. A generous replay window reduces
+the impact of reordering during migration.
+
+Block Policy and IV Safety
+--------------------------
+
+AES-GCM IV uniqueness is critical: reusing a (key, IV) pair allows
+an attacker to recover the authentication subkey and forge
+authentication tags, breaking both confidentiality and integrity.
+This concern applies to outgoing SAs only — the remote peer controls
+IV generation on incoming traffic.
+
+``XFRM_MSG_MIGRATE_STATE`` atomically copies the sequence number and
+replay window from the old SA to the new SA and deletes the old SA.
+The block policy serves two purposes: it prevents cleartext traffic
+leaks during the migration window, and for AES-GCM it prevents IV
+reuse by ensuring no outgoing packets are sent under the same key.
+The atomic copy of the sequence number and replay window complements
+this — together they eliminate both risks during migration.
+The atomic copy also serves incoming SAs, ensuring replay protection
+continues without a gap across the migration.
+
+Feature Detection
+=================
+
+Userspace can probe for kernel support by sending a minimal
+``XFRM_MSG_MIGRATE_STATE`` message with a non-zero non-existent SPI:
+
+- ``-EINVAL``: kernel predates ``XFRM_MSG_MIGRATE_STATE``; message type
+  is out of range
+- ``-ENOPROTOOPT``: message type is known but ``CONFIG_XFRM_MIGRATE``
+  is not enabled
+- ``-ESRCH``: supported (SPI not found)
+
+Userspace Notification on Success
+=================================
+
+On successful migration the kernel multicasts an
+``XFRM_MSG_MIGRATE_STATE`` message to the ``XFRMNLGRP_MIGRATE`` group.
+The fixed header is ``struct xfrm_user_migrate_state`` copied from the
+request, followed by the same set of netlink attributes that are
+accepted as input, with the differences noted below.
+
+Differences from the request
+-----------------------------
+
+.. list-table::
+   :widths: 25 75
+   :header-rows: 1
+
+   * - Field / Attribute
+     - Difference
+   * - ``new_sel``
+     - Contains the actual selector of the newly installed SA, not the
+       ``new_sel`` from the request. When
+       ``XFRM_MIGRATE_STATE_UPDATE_H2H_SEL`` is set the kernel derives the
+       selector from ``new_daddr`` / ``new_saddr``; the caller's
+       ``new_sel`` field is ignored in that case. The notification
+       always carries the real selector of the new SA.
+   * - ``XFRMA_SA_DIR``
+     - Present in the notification (set from the direction of the new
+       SA) but **not accepted as input** — direction is immutable.
+   * - ``flags``
+     - Echoed back as-is. ``XFRM_MIGRATE_STATE_CLEAR_OFFLOAD`` and
+       ``XFRM_MIGRATE_STATE_UPDATE_H2H_SEL`` describe the request that was
+       made, not a property of the resulting SA.
+
+Attributes in the notification
+-------------------------------
+
+.. list-table::
+   :widths: 30 70
+   :header-rows: 1
+
+   * - Attribute
+     - Description
+   * - ``XFRMA_ENCAP``
+     - UDP encapsulation template, if configured on the new SA.
+   * - ``XFRMA_OFFLOAD_DEV``
+     - Hardware offload configuration, if active on the new SA.
+   * - ``XFRMA_MARK``
+     - Mark on the new SA, if set.
+   * - ``XFRMA_SET_MARK``
+     - Output mark on the new SA, if set.
+   * - ``XFRMA_SET_MARK_MASK``
+     - Output mark mask, present together with ``XFRMA_SET_MARK``.
+   * - ``XFRMA_MTIMER_THRESH``
+     - Mapping maxage threshold, if non-zero.
+   * - ``XFRMA_NAT_KEEPALIVE_INTERVAL``
+     - NAT keepalive interval, if non-zero.
+   * - ``XFRMA_SA_DIR``
+     - Direction of the new SA.
+
+Error Handling
+==============
+
+If the target SA tuple (new daddr, SPI, proto, new family) is already
+occupied, the operation returns ``-EEXIST`` before the migration begins.
+The old SA remains intact and the operation is safe to retry after
+resolving the conflict.
+
+If the target SA is deleted before the migration completes, the operation
+returns ``-ESRCH``. No new SA is installed. Userspace should verify the
+current SA state before retrying.
+
+If the multicast notification (``XFRMNLGRP_MIGRATE``) fails to send,
+the migration itself has already completed successfully and the new SA
+is installed. The operation returns success, 0, with an extack warning,
+but listeners will not receive the migration event.
diff --git a/Documentation/networking/xfrm/xfrm_proc.rst b/Documentation/networking/xfrm/xfrm_proc.rst
new file mode 100644
index 000000000..973d1571a
--- /dev/null
+++ b/Documentation/networking/xfrm/xfrm_proc.rst
@@ -0,0 +1,119 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================================
+XFRM proc - /proc/net/xfrm_* files
+==================================
+
+Masahide NAKAMURA <nakam@linux-ipv6.org>
+
+
+Transformation Statistics
+-------------------------
+
+The xfrm_proc code is a set of statistics showing numbers of packets
+dropped by the transformation code and why.  These counters are defined
+as part of the linux private MIB.  These counters can be viewed in
+/proc/net/xfrm_stat.
+
+
+Inbound errors
+~~~~~~~~~~~~~~
+
+XfrmInError:
+	All errors which is not matched others
+
+XfrmInBufferError:
+	No buffer is left
+
+XfrmInHdrError:
+	Header error
+
+XfrmInNoStates:
+	No state is found
+	i.e. Either inbound SPI, address, or IPsec protocol at SA is wrong
+
+XfrmInStateProtoError:
+	Transformation protocol specific error
+	e.g. SA key is wrong
+
+XfrmInStateModeError:
+	Transformation mode specific error
+
+XfrmInStateSeqError:
+	Sequence error
+	i.e. Sequence number is out of window
+
+XfrmInStateExpired:
+	State is expired
+
+XfrmInStateMismatch:
+	State has mismatch option
+	e.g. UDP encapsulation type is mismatch
+
+XfrmInStateInvalid:
+	State is invalid
+
+XfrmInTmplMismatch:
+	No matching template for states
+	e.g. Inbound SAs are correct but SP rule is wrong
+
+XfrmInNoPols:
+	No policy is found for states
+	e.g. Inbound SAs are correct but no SP is found
+
+XfrmInPolBlock:
+	Policy discards
+
+XfrmInPolError:
+	Policy error
+
+XfrmAcquireError:
+	State hasn't been fully acquired before use
+
+XfrmFwdHdrError:
+	Forward routing of a packet is not allowed
+
+XfrmInStateDirError:
+        State direction mismatch (lookup found an output state on the input path, expected input or no direction)
+
+Outbound errors
+~~~~~~~~~~~~~~~
+XfrmOutError:
+	All errors which is not matched others
+
+XfrmOutBundleGenError:
+	Bundle generation error
+
+XfrmOutBundleCheckError:
+	Bundle check error
+
+XfrmOutNoStates:
+	No state is found
+
+XfrmOutStateProtoError:
+	Transformation protocol specific error
+
+XfrmOutStateModeError:
+	Transformation mode specific error
+
+XfrmOutStateSeqError:
+	Sequence error
+	i.e. Sequence number overflow
+
+XfrmOutStateExpired:
+	State is expired
+
+XfrmOutPolBlock:
+	Policy discards
+
+XfrmOutPolDead:
+	Policy is dead
+
+XfrmOutPolError:
+	Policy error
+
+XfrmOutStateInvalid:
+	State is invalid, perhaps expired
+
+XfrmOutStateDirError:
+        State direction mismatch (lookup found an input state on the output path, expected output or no direction)
diff --git a/Documentation/networking/xfrm/xfrm_sync.rst b/Documentation/networking/xfrm/xfrm_sync.rst
new file mode 100644
index 000000000..dfc2ec0df
--- /dev/null
+++ b/Documentation/networking/xfrm/xfrm_sync.rst
@@ -0,0 +1,192 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========
+XFRM sync
+=========
+
+The sync patches work is based on initial patches from
+Krisztian <hidden@balabit.hu> and others and additional patches
+from Jamal <hadi@cyberus.ca>.
+
+The end goal for syncing is to be able to insert attributes + generate
+events so that the SA can be safely moved from one machine to another
+for HA purposes.
+The idea is to synchronize the SA so that the takeover machine can do
+the processing of the SA as accurate as possible if it has access to it.
+
+We already have the ability to generate SA add/del/upd events.
+These patches add ability to sync and have accurate lifetime byte (to
+ensure proper decay of SAs) and replay counters to avoid replay attacks
+with as minimal loss at failover time.
+This way a backup stays as closely up-to-date as an active member.
+
+Because the above items change for every packet the SA receives,
+it is possible for a lot of the events to be generated.
+For this reason, we also add a nagle-like algorithm to restrict
+the events. i.e we are going to set thresholds to say "let me
+know if the replay sequence threshold is reached or 10 secs have passed"
+These thresholds are set system-wide via sysctls or can be updated
+per SA.
+
+The identified items that need to be synchronized are:
+- the lifetime byte counter
+note that: lifetime time limit is not important if you assume the failover
+machine is known ahead of time since the decay of the time countdown
+is not driven by packet arrival.
+- the replay sequence for both inbound and outbound
+
+1) Message Structure
+--------------------
+
+nlmsghdr:aevent_id:optional-TLVs.
+
+The netlink message types are:
+
+XFRM_MSG_NEWAE and XFRM_MSG_GETAE.
+
+A XFRM_MSG_GETAE does not have TLVs.
+
+A XFRM_MSG_NEWAE will have at least two TLVs (as is
+discussed further below).
+
+aevent_id structure looks like::
+
+   struct xfrm_aevent_id {
+	     struct xfrm_usersa_id           sa_id;
+	     xfrm_address_t                  saddr;
+	     __u32                           flags;
+	     __u32                           reqid;
+   };
+
+The unique SA is identified by the combination of xfrm_usersa_id,
+reqid and saddr.
+
+flags are used to indicate different things. The possible
+flags are::
+
+	XFRM_AE_RTHR=1, /* replay threshold*/
+	XFRM_AE_RVAL=2, /* replay value */
+	XFRM_AE_LVAL=4, /* lifetime value */
+	XFRM_AE_ETHR=8, /* expiry timer threshold */
+	XFRM_AE_CR=16, /* Event cause is replay update */
+	XFRM_AE_CE=32, /* Event cause is timer expiry */
+	XFRM_AE_CU=64, /* Event cause is policy update */
+
+How these flags are used is dependent on the direction of the
+message (kernel<->user) as well the cause (config, query or event).
+This is described below in the different messages.
+
+The pid will be set appropriately in netlink to recognize direction
+(0 to the kernel and pid = processid that created the event
+when going from kernel to user space)
+
+A program needs to subscribe to multicast group XFRMNLGRP_AEVENTS
+to get notified of these events.
+
+2) TLVS reflect the different parameters
+----------------------------------------
+
+a) byte value (XFRMA_LTIME_VAL)
+
+   This TLV carries the running/current counter for byte lifetime since
+   last event.
+
+b) replay value (XFRMA_REPLAY_VAL)
+
+   This TLV carries the running/current counter for replay sequence since
+   last event.
+
+c) replay threshold (XFRMA_REPLAY_THRESH)
+
+   This TLV carries the threshold being used by the kernel to trigger events
+   when the replay sequence is exceeded.
+
+d) expiry timer (XFRMA_ETIMER_THRESH)
+
+   This is a timer value in milliseconds which is used as the nagle
+   value to rate limit the events.
+
+3) Default configurations for the parameters
+--------------------------------------------
+
+By default these events should be turned off unless there is
+at least one listener registered to listen to the multicast
+group XFRMNLGRP_AEVENTS.
+
+Programs installing SAs will need to specify the two thresholds, however,
+in order to not change existing applications such as racoon
+we also provide default threshold values for these different parameters
+in case they are not specified.
+
+the two sysctls/proc entries are:
+
+a) /proc/sys/net/core/sysctl_xfrm_aevent_etime
+
+   Used to provide default values for the XFRMA_ETIMER_THRESH in incremental
+   units of time of 100ms. The default is 10 (1 second)
+
+b) /proc/sys/net/core/sysctl_xfrm_aevent_rseqth
+
+   Used to provide default values for XFRMA_REPLAY_THRESH parameter
+   in incremental packet count. The default is two packets.
+
+4) Message types
+----------------
+
+a) XFRM_MSG_GETAE issued by user-->kernel.
+   XFRM_MSG_GETAE does not carry any TLVs.
+
+   The response is a XFRM_MSG_NEWAE which is formatted based on what
+   XFRM_MSG_GETAE queried for.
+
+   The response will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs.
+
+     * if XFRM_AE_RTHR flag is set, then XFRMA_REPLAY_THRESH is also retrieved
+     * if XFRM_AE_ETHR flag is set, then XFRMA_ETIMER_THRESH is also retrieved
+
+b) XFRM_MSG_NEWAE is issued by either user space to configure
+   or kernel to announce events or respond to a XFRM_MSG_GETAE.
+
+   i) user --> kernel to configure a specific SA.
+
+      any of the values or threshold parameters can be updated by passing the
+      appropriate TLV.
+
+      A response is issued back to the sender in user space to indicate success
+      or failure.
+
+      In the case of success, additionally an event with
+      XFRM_MSG_NEWAE is also issued to any listeners as described in iii).
+
+   ii) kernel->user direction as a response to XFRM_MSG_GETAE
+
+       The response will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs.
+
+       The threshold TLVs will be included if explicitly requested in
+       the XFRM_MSG_GETAE message.
+
+   iii) kernel->user to report as event if someone sets any values or
+        thresholds for an SA using XFRM_MSG_NEWAE (as described in #i above).
+        In such a case XFRM_AE_CU flag is set to inform the user that
+        the change happened as a result of an update.
+        The message will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs.
+
+   iv) kernel->user to report event when replay threshold or a timeout
+       is exceeded.
+
+In such a case either XFRM_AE_CR (replay exceeded) or XFRM_AE_CE (timeout
+happened) is set to inform the user what happened.
+Note the two flags are mutually exclusive.
+The message will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs.
+
+5) Exceptions to threshold settings
+-----------------------------------
+
+If you have an SA that is getting hit by traffic in bursts such that
+there is a period where the timer threshold expires with no packets
+seen, then an odd behavior is seen as follows:
+The first packet arrival after a timer expiry will trigger a timeout
+event; i.e we don't wait for a timeout period or a packet threshold
+to be reached. This is done for simplicity and efficiency reasons.
+
+-JHS
diff --git a/Documentation/networking/xfrm/xfrm_sysctl.rst b/Documentation/networking/xfrm/xfrm_sysctl.rst
new file mode 100644
index 000000000..7d0c4b17c
--- /dev/null
+++ b/Documentation/networking/xfrm/xfrm_sysctl.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============
+XFRM Syscall
+============
+
+/proc/sys/net/core/xfrm_* Variables
+===================================
+
+xfrm_acq_expires - INTEGER
+	default 30 - hard timeout in seconds for acquire requests