--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+===============================================
+XFRM device - offloading the IPsec computations
+===============================================
+
+Shannon Nelson <shannon.nelson@oracle.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.
+
+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::
+
+ 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
+
+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 {
+ int (*xdo_dev_state_add) (struct xfrm_state *x);
+ void (*xdo_dev_state_delete) (struct xfrm_state *x);
+ void (*xdo_dev_state_free) (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);
+ };
+
+The NIC driver offering ipsec offload will need to implement these
+callbacks to make the offload available to the network stack's
+XFRM subsytem. 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
+ 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 of false to signify its support.
+
+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().
+
+ 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);
+
+ store the state information into the skb::
+
+ sp = secpath_set(skb);
+ if (!sp) return;
+ sp->xvec[sp->len++] = xs;
+ sp->olen++;
+
+ indicate the success and/or error status of the offload::
+
+ xo = xfrm_offload(skb);
+ xo->flags = CRYPTO_DONE;
+ xo->status = crypto_status;
+
+ hand the packet to napi_gro_receive() as usual
+
+In ESN mode, xdo_dev_state_advance_esn() is called from xfrm_replay_advance_esn().
+Driver will check packet seq number and update HW ESN state machine if needed.
+
+When the SA is removed by the user, the driver's xdo_dev_state_delete()
+is asked to disable the offload. Later, xdo_dev_state_free() is called
+from a garbage collection routine after all reference counts to the state
+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() and xdo_dev_state_free() on any remaining offloaded
+states.
+++ /dev/null
-
-===============================================
-XFRM device - offloading the IPsec computations
-===============================================
-Shannon Nelson <shannon.nelson@oracle.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.
-
-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:
-
- 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
-
-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 {
- int (*xdo_dev_state_add) (struct xfrm_state *x);
- void (*xdo_dev_state_delete) (struct xfrm_state *x);
- void (*xdo_dev_state_free) (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);
-};
-
-The NIC driver offering ipsec offload will need to implement these
-callbacks to make the offload available to the network stack's
-XFRM subsytem. 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
- 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 of false to signify its support.
-
-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().
-
- 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);
-
- store the state information into the skb
- sp = secpath_set(skb);
- if (!sp) return;
- sp->xvec[sp->len++] = xs;
- sp->olen++;
-
- indicate the success and/or error status of the offload
- xo = xfrm_offload(skb);
- xo->flags = CRYPTO_DONE;
- xo->status = crypto_status;
-
- hand the packet to napi_gro_receive() as usual
-
-In ESN mode, xdo_dev_state_advance_esn() is called from xfrm_replay_advance_esn().
-Driver will check packet seq number and update HW ESN state machine if needed.
-
-When the SA is removed by the user, the driver's xdo_dev_state_delete()
-is asked to disable the offload. Later, xdo_dev_state_free() is called
-from a garbage collection routine after all reference counts to the state
-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() and xdo_dev_state_free() on any remaining offloaded
-states.
-
-
projects / platform / kernel / linux-rpi.git / commitdiff