Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 940 insertions, 0 deletions

diff --git a/include/xen/interface/io/netif.h b/include/xen/interface/io/netif.h
new file mode 100644
index 000000000..cb0c1a25d
--- /dev/null
+++ b/include/xen/interface/io/netif.h
@@ -0,0 +1,940 @@
+/* SPDX-License-Identifier: MIT */
+/******************************************************************************
+ * xen_netif.h
+ *
+ * Unified network-device I/O interface for Xen guest OSes.
+ *
+ * Copyright (c) 2003-2004, Keir Fraser
+ */
+
+#ifndef __XEN_PUBLIC_IO_XEN_NETIF_H__
+#define __XEN_PUBLIC_IO_XEN_NETIF_H__
+
+#include "ring.h"
+#include "../grant_table.h"
+
+/*
+ * Older implementation of Xen network frontend / backend has an
+ * implicit dependency on the MAX_SKB_FRAGS as the maximum number of
+ * ring slots a skb can use. Netfront / netback may not work as
+ * expected when frontend and backend have different MAX_SKB_FRAGS.
+ *
+ * A better approach is to add mechanism for netfront / netback to
+ * negotiate this value. However we cannot fix all possible
+ * frontends, so we need to define a value which states the minimum
+ * slots backend must support.
+ *
+ * The minimum value derives from older Linux kernel's MAX_SKB_FRAGS
+ * (18), which is proved to work with most frontends. Any new backend
+ * which doesn't negotiate with frontend should expect frontend to
+ * send a valid packet using slots up to this value.
+ */
+#define XEN_NETIF_NR_SLOTS_MIN 18
+
+/*
+ * Notifications after enqueuing any type of message should be conditional on
+ * the appropriate req_event or rsp_event field in the shared ring.
+ * If the client sends notification for rx requests then it should specify
+ * feature 'feature-rx-notify' via xenbus. Otherwise the backend will assume
+ * that it cannot safely queue packets (as it may not be kicked to send them).
+ */
+
+/*
+ * "feature-split-event-channels" is introduced to separate guest TX
+ * and RX notification. Backend either doesn't support this feature or
+ * advertises it via xenstore as 0 (disabled) or 1 (enabled).
+ *
+ * To make use of this feature, frontend should allocate two event
+ * channels for TX and RX, advertise them to backend as
+ * "event-channel-tx" and "event-channel-rx" respectively. If frontend
+ * doesn't want to use this feature, it just writes "event-channel"
+ * node as before.
+ */
+
+/*
+ * Multiple transmit and receive queues:
+ * If supported, the backend will write the key "multi-queue-max-queues" to
+ * the directory for that vif, and set its value to the maximum supported
+ * number of queues.
+ * Frontends that are aware of this feature and wish to use it can write the
+ * key "multi-queue-num-queues", set to the number they wish to use, which
+ * must be greater than zero, and no more than the value reported by the backend
+ * in "multi-queue-max-queues".
+ *
+ * Queues replicate the shared rings and event channels.
+ * "feature-split-event-channels" may optionally be used when using
+ * multiple queues, but is not mandatory.
+ *
+ * Each queue consists of one shared ring pair, i.e. there must be the same
+ * number of tx and rx rings.
+ *
+ * For frontends requesting just one queue, the usual event-channel and
+ * ring-ref keys are written as before, simplifying the backend processing
+ * to avoid distinguishing between a frontend that doesn't understand the
+ * multi-queue feature, and one that does, but requested only one queue.
+ *
+ * Frontends requesting two or more queues must not write the toplevel
+ * event-channel (or event-channel-{tx,rx}) and {tx,rx}-ring-ref keys,
+ * instead writing those keys under sub-keys having the name "queue-N" where
+ * N is the integer ID of the queue for which those keys belong. Queues
+ * are indexed from zero. For example, a frontend with two queues and split
+ * event channels must write the following set of queue-related keys:
+ *
+ * /local/domain/1/device/vif/0/multi-queue-num-queues = "2"
+ * /local/domain/1/device/vif/0/queue-0 = ""
+ * /local/domain/1/device/vif/0/queue-0/tx-ring-ref = "<ring-ref-tx0>"
+ * /local/domain/1/device/vif/0/queue-0/rx-ring-ref = "<ring-ref-rx0>"
+ * /local/domain/1/device/vif/0/queue-0/event-channel-tx = "<evtchn-tx0>"
+ * /local/domain/1/device/vif/0/queue-0/event-channel-rx = "<evtchn-rx0>"
+ * /local/domain/1/device/vif/0/queue-1 = ""
+ * /local/domain/1/device/vif/0/queue-1/tx-ring-ref = "<ring-ref-tx1>"
+ * /local/domain/1/device/vif/0/queue-1/rx-ring-ref = "<ring-ref-rx1"
+ * /local/domain/1/device/vif/0/queue-1/event-channel-tx = "<evtchn-tx1>"
+ * /local/domain/1/device/vif/0/queue-1/event-channel-rx = "<evtchn-rx1>"
+ *
+ * If there is any inconsistency in the XenStore data, the backend may
+ * choose not to connect any queues, instead treating the request as an
+ * error. This includes scenarios where more (or fewer) queues were
+ * requested than the frontend provided details for.
+ *
+ * Mapping of packets to queues is considered to be a function of the
+ * transmitting system (backend or frontend) and is not negotiated
+ * between the two. Guests are free to transmit packets on any queue
+ * they choose, provided it has been set up correctly. Guests must be
+ * prepared to receive packets on any queue they have requested be set up.
+ */
+
+/*
+ * "feature-no-csum-offload" should be used to turn IPv4 TCP/UDP checksum
+ * offload off or on. If it is missing then the feature is assumed to be on.
+ * "feature-ipv6-csum-offload" should be used to turn IPv6 TCP/UDP checksum
+ * offload on or off. If it is missing then the feature is assumed to be off.
+ */
+
+/*
+ * "feature-gso-tcpv4" and "feature-gso-tcpv6" advertise the capability to
+ * handle large TCP packets (in IPv4 or IPv6 form respectively). Neither
+ * frontends nor backends are assumed to be capable unless the flags are
+ * present.
+ */
+
+/*
+ * "feature-multicast-control" and "feature-dynamic-multicast-control"
+ * advertise the capability to filter ethernet multicast packets in the
+ * backend. If the frontend wishes to take advantage of this feature then
+ * it may set "request-multicast-control". If the backend only advertises
+ * "feature-multicast-control" then "request-multicast-control" must be set
+ * before the frontend moves into the connected state. The backend will
+ * sample the value on this state transition and any subsequent change in
+ * value will have no effect. However, if the backend also advertises
+ * "feature-dynamic-multicast-control" then "request-multicast-control"
+ * may be set by the frontend at any time. In this case, the backend will
+ * watch the value and re-sample on watch events.
+ *
+ * If the sampled value of "request-multicast-control" is set then the
+ * backend transmit side should no longer flood multicast packets to the
+ * frontend, it should instead drop any multicast packet that does not
+ * match in a filter list.
+ * The list is amended by the frontend by sending dummy transmit requests
+ * containing XEN_NETIF_EXTRA_TYPE_MCAST_{ADD,DEL} extra-info fragments as
+ * specified below.
+ * Note that the filter list may be amended even if the sampled value of
+ * "request-multicast-control" is not set, however the filter should only
+ * be applied if it is set.
+ */
+
+/*
+ * "xdp-headroom" is used to request that extra space is added
+ * for XDP processing.  The value is measured in bytes and passed by
+ * the frontend to be consistent between both ends.
+ * If the value is greater than zero that means that
+ * an RX response is going to be passed to an XDP program for processing.
+ * XEN_NETIF_MAX_XDP_HEADROOM defines the maximum headroom offset in bytes
+ *
+ * "feature-xdp-headroom" is set to "1" by the netback side like other features
+ * so a guest can check if an XDP program can be processed.
+ */
+#define XEN_NETIF_MAX_XDP_HEADROOM 0x7FFF
+
+/*
+ * Control ring
+ * ============
+ *
+ * Some features, such as hashing (detailed below), require a
+ * significant amount of out-of-band data to be passed from frontend to
+ * backend. Use of xenstore is not suitable for large quantities of data
+ * because of quota limitations and so a dedicated 'control ring' is used.
+ * The ability of the backend to use a control ring is advertised by
+ * setting:
+ *
+ * /local/domain/X/backend/<domid>/<vif>/feature-ctrl-ring = "1"
+ *
+ * The frontend provides a control ring to the backend by setting:
+ *
+ * /local/domain/<domid>/device/vif/<vif>/ctrl-ring-ref = <gref>
+ * /local/domain/<domid>/device/vif/<vif>/event-channel-ctrl = <port>
+ *
+ * where <gref> is the grant reference of the shared page used to
+ * implement the control ring and <port> is an event channel to be used
+ * as a mailbox interrupt. These keys must be set before the frontend
+ * moves into the connected state.
+ *
+ * The control ring uses a fixed request/response message size and is
+ * balanced (i.e. one request to one response), so operationally it is much
+ * the same as a transmit or receive ring.
+ * Note that there is no requirement that responses are issued in the same
+ * order as requests.
+ */
+
+/*
+ * Hash types
+ * ==========
+ *
+ * For the purposes of the definitions below, 'Packet[]' is an array of
+ * octets containing an IP packet without options, 'Array[X..Y]' means a
+ * sub-array of 'Array' containing bytes X thru Y inclusive, and '+' is
+ * used to indicate concatenation of arrays.
+ */
+
+/*
+ * A hash calculated over an IP version 4 header as follows:
+ *
+ * Buffer[0..8] = Packet[12..15] (source address) +
+ *                Packet[16..19] (destination address)
+ *
+ * Result = Hash(Buffer, 8)
+ */
+#define _XEN_NETIF_CTRL_HASH_TYPE_IPV4 0
+#define XEN_NETIF_CTRL_HASH_TYPE_IPV4 \
+	(1 << _XEN_NETIF_CTRL_HASH_TYPE_IPV4)
+
+/*
+ * A hash calculated over an IP version 4 header and TCP header as
+ * follows:
+ *
+ * Buffer[0..12] = Packet[12..15] (source address) +
+ *                 Packet[16..19] (destination address) +
+ *                 Packet[20..21] (source port) +
+ *                 Packet[22..23] (destination port)
+ *
+ * Result = Hash(Buffer, 12)
+ */
+#define _XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP 1
+#define XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP \
+	(1 << _XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP)
+
+/*
+ * A hash calculated over an IP version 6 header as follows:
+ *
+ * Buffer[0..32] = Packet[8..23]  (source address ) +
+ *                 Packet[24..39] (destination address)
+ *
+ * Result = Hash(Buffer, 32)
+ */
+#define _XEN_NETIF_CTRL_HASH_TYPE_IPV6 2
+#define XEN_NETIF_CTRL_HASH_TYPE_IPV6 \
+	(1 << _XEN_NETIF_CTRL_HASH_TYPE_IPV6)
+
+/*
+ * A hash calculated over an IP version 6 header and TCP header as
+ * follows:
+ *
+ * Buffer[0..36] = Packet[8..23]  (source address) +
+ *                 Packet[24..39] (destination address) +
+ *                 Packet[40..41] (source port) +
+ *                 Packet[42..43] (destination port)
+ *
+ * Result = Hash(Buffer, 36)
+ */
+#define _XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP 3
+#define XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP \
+	(1 << _XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP)
+
+/*
+ * Hash algorithms
+ * ===============
+ */
+
+#define XEN_NETIF_CTRL_HASH_ALGORITHM_NONE 0
+
+/*
+ * Toeplitz hash:
+ */
+
+#define XEN_NETIF_CTRL_HASH_ALGORITHM_TOEPLITZ 1
+
+/*
+ * This algorithm uses a 'key' as well as the data buffer itself.
+ * (Buffer[] and Key[] are treated as shift-registers where the MSB of
+ * Buffer/Key[0] is considered 'left-most' and the LSB of Buffer/Key[N-1]
+ * is the 'right-most').
+ *
+ * Value = 0
+ * For number of bits in Buffer[]
+ *    If (left-most bit of Buffer[] is 1)
+ *        Value ^= left-most 32 bits of Key[]
+ *    Key[] << 1
+ *    Buffer[] << 1
+ *
+ * The code below is provided for convenience where an operating system
+ * does not already provide an implementation.
+ */
+#ifdef XEN_NETIF_DEFINE_TOEPLITZ
+static uint32_t xen_netif_toeplitz_hash(const uint8_t *key,
+					unsigned int keylen,
+					const uint8_t *buf, unsigned int buflen)
+{
+	unsigned int keyi, bufi;
+	uint64_t prefix = 0;
+	uint64_t hash = 0;
+
+	/* Pre-load prefix with the first 8 bytes of the key */
+	for (keyi = 0; keyi < 8; keyi++) {
+		prefix <<= 8;
+		prefix |= (keyi < keylen) ? key[keyi] : 0;
+	}
+
+	for (bufi = 0; bufi < buflen; bufi++) {
+		uint8_t byte = buf[bufi];
+		unsigned int bit;
+
+		for (bit = 0; bit < 8; bit++) {
+			if (byte & 0x80)
+				hash ^= prefix;
+			prefix <<= 1;
+			byte <<= 1;
+		}
+
+		/*
+		 * 'prefix' has now been left-shifted by 8, so
+		 * OR in the next byte.
+		 */
+		prefix |= (keyi < keylen) ? key[keyi] : 0;
+		keyi++;
+	}
+
+	/* The valid part of the hash is in the upper 32 bits. */
+	return hash >> 32;
+}
+#endif				/* XEN_NETIF_DEFINE_TOEPLITZ */
+
+/*
+ * Control requests (struct xen_netif_ctrl_request)
+ * ================================================
+ *
+ * All requests have the following format:
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |    id     |   type    |         data[0]       |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |         data[1]       |         data[2]       |
+ * +-----+-----+-----+-----+-----------------------+
+ *
+ * id: the request identifier, echoed in response.
+ * type: the type of request (see below)
+ * data[]: any data associated with the request (determined by type)
+ */
+
+struct xen_netif_ctrl_request {
+	uint16_t id;
+	uint16_t type;
+
+#define XEN_NETIF_CTRL_TYPE_INVALID               0
+#define XEN_NETIF_CTRL_TYPE_GET_HASH_FLAGS        1
+#define XEN_NETIF_CTRL_TYPE_SET_HASH_FLAGS        2
+#define XEN_NETIF_CTRL_TYPE_SET_HASH_KEY          3
+#define XEN_NETIF_CTRL_TYPE_GET_HASH_MAPPING_SIZE 4
+#define XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING_SIZE 5
+#define XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING      6
+#define XEN_NETIF_CTRL_TYPE_SET_HASH_ALGORITHM    7
+
+	uint32_t data[3];
+};
+
+/*
+ * Control responses (struct xen_netif_ctrl_response)
+ * ==================================================
+ *
+ * All responses have the following format:
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |    id     |   type    |         status        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |         data          |
+ * +-----+-----+-----+-----+
+ *
+ * id: the corresponding request identifier
+ * type: the type of the corresponding request
+ * status: the status of request processing
+ * data: any data associated with the response (determined by type and
+ *       status)
+ */
+
+struct xen_netif_ctrl_response {
+	uint16_t id;
+	uint16_t type;
+	uint32_t status;
+
+#define XEN_NETIF_CTRL_STATUS_SUCCESS           0
+#define XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     1
+#define XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER 2
+#define XEN_NETIF_CTRL_STATUS_BUFFER_OVERFLOW   3
+
+	uint32_t data;
+};
+
+/*
+ * Control messages
+ * ================
+ *
+ * XEN_NETIF_CTRL_TYPE_SET_HASH_ALGORITHM
+ * --------------------------------------
+ *
+ * This is sent by the frontend to set the desired hash algorithm.
+ *
+ * Request:
+ *
+ *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_ALGORITHM
+ *  data[0] = a XEN_NETIF_CTRL_HASH_ALGORITHM_* value
+ *  data[1] = 0
+ *  data[2] = 0
+ *
+ * Response:
+ *
+ *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
+ *                                                     supported
+ *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - The algorithm is not
+ *                                                     supported
+ *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
+ *
+ * NOTE: Setting data[0] to XEN_NETIF_CTRL_HASH_ALGORITHM_NONE disables
+ *       hashing and the backend is free to choose how it steers packets
+ *       to queues (which is the default behaviour).
+ *
+ * XEN_NETIF_CTRL_TYPE_GET_HASH_FLAGS
+ * ----------------------------------
+ *
+ * This is sent by the frontend to query the types of hash supported by
+ * the backend.
+ *
+ * Request:
+ *
+ *  type    = XEN_NETIF_CTRL_TYPE_GET_HASH_FLAGS
+ *  data[0] = 0
+ *  data[1] = 0
+ *  data[2] = 0
+ *
+ * Response:
+ *
+ *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED - Operation not supported
+ *           XEN_NETIF_CTRL_STATUS_SUCCESS       - Operation successful
+ *  data   = supported hash types (if operation was successful)
+ *
+ * NOTE: A valid hash algorithm must be selected before this operation can
+ *       succeed.
+ *
+ * XEN_NETIF_CTRL_TYPE_SET_HASH_FLAGS
+ * ----------------------------------
+ *
+ * This is sent by the frontend to set the types of hash that the backend
+ * should calculate. (See above for hash type definitions).
+ * Note that the 'maximal' type of hash should always be chosen. For
+ * example, if the frontend sets both IPV4 and IPV4_TCP hash types then
+ * the latter hash type should be calculated for any TCP packet and the
+ * former only calculated for non-TCP packets.
+ *
+ * Request:
+ *
+ *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_FLAGS
+ *  data[0] = bitwise OR of XEN_NETIF_CTRL_HASH_TYPE_* values
+ *  data[1] = 0
+ *  data[2] = 0
+ *
+ * Response:
+ *
+ *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
+ *                                                     supported
+ *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - One or more flag
+ *                                                     value is invalid or
+ *                                                     unsupported
+ *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
+ *  data   = 0
+ *
+ * NOTE: A valid hash algorithm must be selected before this operation can
+ *       succeed.
+ *       Also, setting data[0] to zero disables hashing and the backend
+ *       is free to choose how it steers packets to queues.
+ *
+ * XEN_NETIF_CTRL_TYPE_SET_HASH_KEY
+ * --------------------------------
+ *
+ * This is sent by the frontend to set the key of the hash if the algorithm
+ * requires it. (See hash algorithms above).
+ *
+ * Request:
+ *
+ *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_KEY
+ *  data[0] = grant reference of page containing the key (assumed to
+ *            start at beginning of grant)
+ *  data[1] = size of key in octets
+ *  data[2] = 0
+ *
+ * Response:
+ *
+ *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
+ *                                                     supported
+ *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - Key size is invalid
+ *           XEN_NETIF_CTRL_STATUS_BUFFER_OVERFLOW   - Key size is larger
+ *                                                     than the backend
+ *                                                     supports
+ *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
+ *  data   = 0
+ *
+ * NOTE: Any key octets not specified are assumed to be zero (the key
+ *       is assumed to be empty by default) and specifying a new key
+ *       invalidates any previous key, hence specifying a key size of
+ *       zero will clear the key (which ensures that the calculated hash
+ *       will always be zero).
+ *       The maximum size of key is algorithm and backend specific, but
+ *       is also limited by the single grant reference.
+ *       The grant reference may be read-only and must remain valid until
+ *       the response has been processed.
+ *
+ * XEN_NETIF_CTRL_TYPE_GET_HASH_MAPPING_SIZE
+ * -----------------------------------------
+ *
+ * This is sent by the frontend to query the maximum size of mapping
+ * table supported by the backend. The size is specified in terms of
+ * table entries.
+ *
+ * Request:
+ *
+ *  type    = XEN_NETIF_CTRL_TYPE_GET_HASH_MAPPING_SIZE
+ *  data[0] = 0
+ *  data[1] = 0
+ *  data[2] = 0
+ *
+ * Response:
+ *
+ *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED - Operation not supported
+ *           XEN_NETIF_CTRL_STATUS_SUCCESS       - Operation successful
+ *  data   = maximum number of entries allowed in the mapping table
+ *           (if operation was successful) or zero if a mapping table is
+ *           not supported (i.e. hash mapping is done only by modular
+ *           arithmetic).
+ *
+ * XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING_SIZE
+ * -------------------------------------
+ *
+ * This is sent by the frontend to set the actual size of the mapping
+ * table to be used by the backend. The size is specified in terms of
+ * table entries.
+ * Any previous table is invalidated by this message and any new table
+ * is assumed to be zero filled.
+ *
+ * Request:
+ *
+ *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING_SIZE
+ *  data[0] = number of entries in mapping table
+ *  data[1] = 0
+ *  data[2] = 0
+ *
+ * Response:
+ *
+ *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
+ *                                                     supported
+ *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - Table size is invalid
+ *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
+ *  data   = 0
+ *
+ * NOTE: Setting data[0] to 0 means that hash mapping should be done
+ *       using modular arithmetic.
+ *
+ * XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING
+ * ------------------------------------
+ *
+ * This is sent by the frontend to set the content of the table mapping
+ * hash value to queue number. The backend should calculate the hash from
+ * the packet header, use it as an index into the table (modulo the size
+ * of the table) and then steer the packet to the queue number found at
+ * that index.
+ *
+ * Request:
+ *
+ *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING
+ *  data[0] = grant reference of page containing the mapping (sub-)table
+ *            (assumed to start at beginning of grant)
+ *  data[1] = size of (sub-)table in entries
+ *  data[2] = offset, in entries, of sub-table within overall table
+ *
+ * Response:
+ *
+ *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
+ *                                                     supported
+ *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - Table size or content
+ *                                                     is invalid
+ *           XEN_NETIF_CTRL_STATUS_BUFFER_OVERFLOW   - Table size is larger
+ *                                                     than the backend
+ *                                                     supports
+ *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
+ *  data   = 0
+ *
+ * NOTE: The overall table has the following format:
+ *
+ *          0     1     2     3     4     5     6     7  octet
+ *       +-----+-----+-----+-----+-----+-----+-----+-----+
+ *       |       mapping[0]      |       mapping[1]      |
+ *       +-----+-----+-----+-----+-----+-----+-----+-----+
+ *       |                       .                       |
+ *       |                       .                       |
+ *       |                       .                       |
+ *       +-----+-----+-----+-----+-----+-----+-----+-----+
+ *       |      mapping[N-2]     |      mapping[N-1]     |
+ *       +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ *       where N is specified by a XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING_SIZE
+ *       message and each  mapping must specifies a queue between 0 and
+ *       "multi-queue-num-queues" (see above).
+ *       The backend may support a mapping table larger than can be
+ *       mapped by a single grant reference. Thus sub-tables within a
+ *       larger table can be individually set by sending multiple messages
+ *       with differing offset values. Specifying a new sub-table does not
+ *       invalidate any table data outside that range.
+ *       The grant reference may be read-only and must remain valid until
+ *       the response has been processed.
+ */
+
+DEFINE_RING_TYPES(xen_netif_ctrl,
+		  struct xen_netif_ctrl_request,
+		  struct xen_netif_ctrl_response);
+
+/*
+ * Guest transmit
+ * ==============
+ *
+ * This is the 'wire' format for transmit (frontend -> backend) packets:
+ *
+ *  Fragment 1: xen_netif_tx_request_t  - flags = XEN_NETTXF_*
+ *                                    size = total packet size
+ * [Extra 1: xen_netif_extra_info_t]    - (only if fragment 1 flags include
+ *                                     XEN_NETTXF_extra_info)
+ *  ...
+ * [Extra N: xen_netif_extra_info_t]    - (only if extra N-1 flags include
+ *                                     XEN_NETIF_EXTRA_MORE)
+ *  ...
+ *  Fragment N: xen_netif_tx_request_t  - (only if fragment N-1 flags include
+ *                                     XEN_NETTXF_more_data - flags on preceding
+ *                                     extras are not relevant here)
+ *                                    flags = 0
+ *                                    size = fragment size
+ *
+ * NOTE:
+ *
+ * This format slightly is different from that used for receive
+ * (backend -> frontend) packets. Specifically, in a multi-fragment
+ * packet the actual size of fragment 1 can only be determined by
+ * subtracting the sizes of fragments 2..N from the total packet size.
+ *
+ * Ring slot size is 12 octets, however not all request/response
+ * structs use the full size.
+ *
+ * tx request data (xen_netif_tx_request_t)
+ * ------------------------------------
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * | grant ref             | offset    | flags     |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * | id        | size      |
+ * +-----+-----+-----+-----+
+ *
+ * grant ref: Reference to buffer page.
+ * offset: Offset within buffer page.
+ * flags: XEN_NETTXF_*.
+ * id: request identifier, echoed in response.
+ * size: packet size in bytes.
+ *
+ * tx response (xen_netif_tx_response_t)
+ * ---------------------------------
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * | id        | status    | unused                |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * | unused                |
+ * +-----+-----+-----+-----+
+ *
+ * id: reflects id in transmit request
+ * status: XEN_NETIF_RSP_*
+ *
+ * Guest receive
+ * =============
+ *
+ * This is the 'wire' format for receive (backend -> frontend) packets:
+ *
+ *  Fragment 1: xen_netif_rx_request_t  - flags = XEN_NETRXF_*
+ *                                    size = fragment size
+ * [Extra 1: xen_netif_extra_info_t]    - (only if fragment 1 flags include
+ *                                     XEN_NETRXF_extra_info)
+ *  ...
+ * [Extra N: xen_netif_extra_info_t]    - (only if extra N-1 flags include
+ *                                     XEN_NETIF_EXTRA_MORE)
+ *  ...
+ *  Fragment N: xen_netif_rx_request_t  - (only if fragment N-1 flags include
+ *                                     XEN_NETRXF_more_data - flags on preceding
+ *                                     extras are not relevant here)
+ *                                    flags = 0
+ *                                    size = fragment size
+ *
+ * NOTE:
+ *
+ * This format slightly is different from that used for transmit
+ * (frontend -> backend) packets. Specifically, in a multi-fragment
+ * packet the size of the packet can only be determined by summing the
+ * sizes of fragments 1..N.
+ *
+ * Ring slot size is 8 octets.
+ *
+ * rx request (xen_netif_rx_request_t)
+ * -------------------------------
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * | id        | pad       | gref                  |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * id: request identifier, echoed in response.
+ * gref: reference to incoming granted frame.
+ *
+ * rx response (xen_netif_rx_response_t)
+ * ---------------------------------
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * | id        | offset    | flags     | status    |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * id: reflects id in receive request
+ * offset: offset in page of start of received packet
+ * flags: XEN_NETRXF_*
+ * status: -ve: XEN_NETIF_RSP_*; +ve: Rx'ed pkt size.
+ *
+ * NOTE: Historically, to support GSO on the frontend receive side, Linux
+ *       netfront does not make use of the rx response id (because, as
+ *       described below, extra info structures overlay the id field).
+ *       Instead it assumes that responses always appear in the same ring
+ *       slot as their corresponding request. Thus, to maintain
+ *       compatibility, backends must make sure this is the case.
+ *
+ * Extra Info
+ * ==========
+ *
+ * Can be present if initial request or response has NET{T,R}XF_extra_info,
+ * or previous extra request has XEN_NETIF_EXTRA_MORE.
+ *
+ * The struct therefore needs to fit into either a tx or rx slot and
+ * is therefore limited to 8 octets.
+ *
+ * NOTE: Because extra info data overlays the usual request/response
+ *       structures, there is no id information in the opposite direction.
+ *       So, if an extra info overlays an rx response the frontend can
+ *       assume that it is in the same ring slot as the request that was
+ *       consumed to make the slot available, and the backend must ensure
+ *       this assumption is true.
+ *
+ * extra info (xen_netif_extra_info_t)
+ * -------------------------------
+ *
+ * General format:
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |type |flags| type specific data                |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * | padding for tx        |
+ * +-----+-----+-----+-----+
+ *
+ * type: XEN_NETIF_EXTRA_TYPE_*
+ * flags: XEN_NETIF_EXTRA_FLAG_*
+ * padding for tx: present only in the tx case due to 8 octet limit
+ *                 from rx case. Not shown in type specific entries
+ *                 below.
+ *
+ * XEN_NETIF_EXTRA_TYPE_GSO:
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |type |flags| size      |type | pad | features  |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * type: Must be XEN_NETIF_EXTRA_TYPE_GSO
+ * flags: XEN_NETIF_EXTRA_FLAG_*
+ * size: Maximum payload size of each segment. For example,
+ *       for TCP this is just the path MSS.
+ * type: XEN_NETIF_GSO_TYPE_*: This determines the protocol of
+ *       the packet and any extra features required to segment the
+ *       packet properly.
+ * features: EN_XEN_NETIF_GSO_FEAT_*: This specifies any extra GSO
+ *           features required to process this packet, such as ECN
+ *           support for TCPv4.
+ *
+ * XEN_NETIF_EXTRA_TYPE_MCAST_{ADD,DEL}:
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |type |flags| addr                              |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * type: Must be XEN_NETIF_EXTRA_TYPE_MCAST_{ADD,DEL}
+ * flags: XEN_NETIF_EXTRA_FLAG_*
+ * addr: address to add/remove
+ *
+ * XEN_NETIF_EXTRA_TYPE_HASH:
+ *
+ * A backend that supports teoplitz hashing is assumed to accept
+ * this type of extra info in transmit packets.
+ * A frontend that enables hashing is assumed to accept
+ * this type of extra info in receive packets.
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |type |flags|htype| alg |LSB ---- value ---- MSB|
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * type: Must be XEN_NETIF_EXTRA_TYPE_HASH
+ * flags: XEN_NETIF_EXTRA_FLAG_*
+ * htype: Hash type (one of _XEN_NETIF_CTRL_HASH_TYPE_* - see above)
+ * alg: The algorithm used to calculate the hash (one of
+ *      XEN_NETIF_CTRL_HASH_TYPE_ALGORITHM_* - see above)
+ * value: Hash value
+ */
+
+/* Protocol checksum field is blank in the packet (hardware offload)? */
+#define _XEN_NETTXF_csum_blank     (0)
+#define  XEN_NETTXF_csum_blank     (1U<<_XEN_NETTXF_csum_blank)
+
+/* Packet data has been validated against protocol checksum. */
+#define _XEN_NETTXF_data_validated (1)
+#define  XEN_NETTXF_data_validated (1U<<_XEN_NETTXF_data_validated)
+
+/* Packet continues in the next request descriptor. */
+#define _XEN_NETTXF_more_data      (2)
+#define  XEN_NETTXF_more_data      (1U<<_XEN_NETTXF_more_data)
+
+/* Packet to be followed by extra descriptor(s). */
+#define _XEN_NETTXF_extra_info     (3)
+#define  XEN_NETTXF_extra_info     (1U<<_XEN_NETTXF_extra_info)
+
+#define XEN_NETIF_MAX_TX_SIZE 0xFFFF
+struct xen_netif_tx_request {
+	grant_ref_t gref;
+	uint16_t offset;
+	uint16_t flags;
+	uint16_t id;
+	uint16_t size;
+};
+
+/* Types of xen_netif_extra_info descriptors. */
+#define XEN_NETIF_EXTRA_TYPE_NONE      (0)	/* Never used - invalid */
+#define XEN_NETIF_EXTRA_TYPE_GSO       (1)	/* u.gso */
+#define XEN_NETIF_EXTRA_TYPE_MCAST_ADD (2)	/* u.mcast */
+#define XEN_NETIF_EXTRA_TYPE_MCAST_DEL (3)	/* u.mcast */
+#define XEN_NETIF_EXTRA_TYPE_HASH      (4)	/* u.hash */
+#define XEN_NETIF_EXTRA_TYPE_XDP       (5)	/* u.xdp */
+#define XEN_NETIF_EXTRA_TYPE_MAX       (6)
+
+/* xen_netif_extra_info_t flags. */
+#define _XEN_NETIF_EXTRA_FLAG_MORE (0)
+#define XEN_NETIF_EXTRA_FLAG_MORE  (1U<<_XEN_NETIF_EXTRA_FLAG_MORE)
+
+/* GSO types */
+#define XEN_NETIF_GSO_TYPE_NONE         (0)
+#define XEN_NETIF_GSO_TYPE_TCPV4        (1)
+#define XEN_NETIF_GSO_TYPE_TCPV6        (2)
+
+/*
+ * This structure needs to fit within both xen_netif_tx_request_t and
+ * xen_netif_rx_response_t for compatibility.
+ */
+struct xen_netif_extra_info {
+	uint8_t type;
+	uint8_t flags;
+	union {
+		struct {
+			uint16_t size;
+			uint8_t type;
+			uint8_t pad;
+			uint16_t features;
+		} gso;
+		struct {
+			uint8_t addr[6];
+		} mcast;
+		struct {
+			uint8_t type;
+			uint8_t algorithm;
+			uint8_t value[4];
+		} hash;
+		struct {
+			uint16_t headroom;
+			uint16_t pad[2];
+		} xdp;
+		uint16_t pad[3];
+	} u;
+};
+
+struct xen_netif_tx_response {
+	uint16_t id;
+	int16_t status;
+};
+
+struct xen_netif_rx_request {
+	uint16_t id;		/* Echoed in response message.        */
+	uint16_t pad;
+	grant_ref_t gref;
+};
+
+/* Packet data has been validated against protocol checksum. */
+#define _XEN_NETRXF_data_validated (0)
+#define  XEN_NETRXF_data_validated (1U<<_XEN_NETRXF_data_validated)
+
+/* Protocol checksum field is blank in the packet (hardware offload)? */
+#define _XEN_NETRXF_csum_blank     (1)
+#define  XEN_NETRXF_csum_blank     (1U<<_XEN_NETRXF_csum_blank)
+
+/* Packet continues in the next request descriptor. */
+#define _XEN_NETRXF_more_data      (2)
+#define  XEN_NETRXF_more_data      (1U<<_XEN_NETRXF_more_data)
+
+/* Packet to be followed by extra descriptor(s). */
+#define _XEN_NETRXF_extra_info     (3)
+#define  XEN_NETRXF_extra_info     (1U<<_XEN_NETRXF_extra_info)
+
+/* Packet has GSO prefix. Deprecated but included for compatibility */
+#define _XEN_NETRXF_gso_prefix     (4)
+#define  XEN_NETRXF_gso_prefix     (1U<<_XEN_NETRXF_gso_prefix)
+
+struct xen_netif_rx_response {
+	uint16_t id;
+	uint16_t offset;
+	uint16_t flags;
+	int16_t status;
+};
+
+/*
+ * Generate xen_netif ring structures and types.
+ */
+
+DEFINE_RING_TYPES(xen_netif_tx, struct xen_netif_tx_request,
+		  struct xen_netif_tx_response);
+DEFINE_RING_TYPES(xen_netif_rx, struct xen_netif_rx_request,
+		  struct xen_netif_rx_response);
+
+#define XEN_NETIF_RSP_DROPPED         -2
+#define XEN_NETIF_RSP_ERROR           -1
+#define XEN_NETIF_RSP_OKAY             0
+/* No response: used for auxiliary requests (e.g., xen_netif_extra_info_t). */
+#define XEN_NETIF_RSP_NULL             1
+
+#endif