include/xen/interface/io/netif.h

   1 /******************************************************************************
   2  * netif.h
   3  *
   4  * Unified network-device I/O interface for Xen guest OSes.
   5  *
   6  * Copyright (c) 2003-2004, Keir Fraser
   7  */
   8
   9 #ifndef __XEN_PUBLIC_IO_NETIF_H__
  10 #define __XEN_PUBLIC_IO_NETIF_H__
  11
  12 #include <xen/interface/io/ring.h>
  13 #include <xen/interface/grant_table.h>
  14
  15 /*
  16  * Older implementation of Xen network frontend / backend has an
  17  * implicit dependency on the MAX_SKB_FRAGS as the maximum number of
  18  * ring slots a skb can use. Netfront / netback may not work as
  19  * expected when frontend and backend have different MAX_SKB_FRAGS.
  20  *
  21  * A better approach is to add mechanism for netfront / netback to
  22  * negotiate this value. However we cannot fix all possible
  23  * frontends, so we need to define a value which states the minimum
  24  * slots backend must support.
  25  *
  26  * The minimum value derives from older Linux kernel's MAX_SKB_FRAGS
  27  * (18), which is proved to work with most frontends. Any new backend
  28  * which doesn't negotiate with frontend should expect frontend to
  29  * send a valid packet using slots up to this value.
  30  */
  31 #define XEN_NETIF_NR_SLOTS_MIN 18
  32
  33 /*
  34  * Notifications after enqueuing any type of message should be conditional on
  35  * the appropriate req_event or rsp_event field in the shared ring.
  36  * If the client sends notification for rx requests then it should specify
  37  * feature 'feature-rx-notify' via xenbus. Otherwise the backend will assume
  38  * that it cannot safely queue packets (as it may not be kicked to send them).
  39  */
  40
  41  /*
  42  * "feature-split-event-channels" is introduced to separate guest TX
  43  * and RX notificaion. Backend either doesn't support this feature or
  44  * advertise it via xenstore as 0 (disabled) or 1 (enabled).
  45  *
  46  * To make use of this feature, frontend should allocate two event
  47  * channels for TX and RX, advertise them to backend as
  48  * "event-channel-tx" and "event-channel-rx" respectively. If frontend
  49  * doesn't want to use this feature, it just writes "event-channel"
  50  * node as before.
  51  */
  52
  53 /*
  54  * Multiple transmit and receive queues:
  55  * If supported, the backend will write the key "multi-queue-max-queues" to
  56  * the directory for that vif, and set its value to the maximum supported
  57  * number of queues.
  58  * Frontends that are aware of this feature and wish to use it can write the
  59  * key "multi-queue-num-queues", set to the number they wish to use, which
  60  * must be greater than zero, and no more than the value reported by the backend
  61  * in "multi-queue-max-queues".
  62  *
  63  * Queues replicate the shared rings and event channels.
  64  * "feature-split-event-channels" may optionally be used when using
  65  * multiple queues, but is not mandatory.
  66  *
  67  * Each queue consists of one shared ring pair, i.e. there must be the same
  68  * number of tx and rx rings.
  69  *
  70  * For frontends requesting just one queue, the usual event-channel and
  71  * ring-ref keys are written as before, simplifying the backend processing
  72  * to avoid distinguishing between a frontend that doesn't understand the
  73  * multi-queue feature, and one that does, but requested only one queue.
  74  *
  75  * Frontends requesting two or more queues must not write the toplevel
  76  * event-channel (or event-channel-{tx,rx}) and {tx,rx}-ring-ref keys,
  77  * instead writing those keys under sub-keys having the name "queue-N" where
  78  * N is the integer ID of the queue for which those keys belong. Queues
  79  * are indexed from zero. For example, a frontend with two queues and split
  80  * event channels must write the following set of queue-related keys:
  81  *
  82  * /local/domain/1/device/vif/0/multi-queue-num-queues = "2"
  83  * /local/domain/1/device/vif/0/queue-0 = ""
  84  * /local/domain/1/device/vif/0/queue-0/tx-ring-ref = "<ring-ref-tx0>"
  85  * /local/domain/1/device/vif/0/queue-0/rx-ring-ref = "<ring-ref-rx0>"
  86  * /local/domain/1/device/vif/0/queue-0/event-channel-tx = "<evtchn-tx0>"
  87  * /local/domain/1/device/vif/0/queue-0/event-channel-rx = "<evtchn-rx0>"
  88  * /local/domain/1/device/vif/0/queue-1 = ""
  89  * /local/domain/1/device/vif/0/queue-1/tx-ring-ref = "<ring-ref-tx1>"
  90  * /local/domain/1/device/vif/0/queue-1/rx-ring-ref = "<ring-ref-rx1"
  91  * /local/domain/1/device/vif/0/queue-1/event-channel-tx = "<evtchn-tx1>"
  92  * /local/domain/1/device/vif/0/queue-1/event-channel-rx = "<evtchn-rx1>"
  93  *
  94  * If there is any inconsistency in the XenStore data, the backend may
  95  * choose not to connect any queues, instead treating the request as an
  96  * error. This includes scenarios where more (or fewer) queues were
  97  * requested than the frontend provided details for.
  98  *
  99  * Mapping of packets to queues is considered to be a function of the
 100  * transmitting system (backend or frontend) and is not negotiated
 101  * between the two. Guests are free to transmit packets on any queue
 102  * they choose, provided it has been set up correctly. Guests must be
 103  * prepared to receive packets on any queue they have requested be set up.
 104  */
 105
 106 /*
 107  * "feature-no-csum-offload" should be used to turn IPv4 TCP/UDP checksum
 108  * offload off or on. If it is missing then the feature is assumed to be on.
 109  * "feature-ipv6-csum-offload" should be used to turn IPv6 TCP/UDP checksum
 110  * offload on or off. If it is missing then the feature is assumed to be off.
 111  */
 112
 113 /*
 114  * "feature-gso-tcpv4" and "feature-gso-tcpv6" advertise the capability to
 115  * handle large TCP packets (in IPv4 or IPv6 form respectively). Neither
 116  * frontends nor backends are assumed to be capable unless the flags are
 117  * present.
 118  */
 119
 120 /*
 121  * This is the 'wire' format for packets:
 122  *  Request 1: xen_netif_tx_request  -- XEN_NETTXF_* (any flags)
 123  * [Request 2: xen_netif_extra_info]    (only if request 1 has XEN_NETTXF_extra_info)
 124  * [Request 3: xen_netif_extra_info]    (only if request 2 has XEN_NETIF_EXTRA_MORE)
 125  *  Request 4: xen_netif_tx_request  -- XEN_NETTXF_more_data
 126  *  Request 5: xen_netif_tx_request  -- XEN_NETTXF_more_data
 127  *  ...
 128  *  Request N: xen_netif_tx_request  -- 0
 129  */
 130
 131 /* Protocol checksum field is blank in the packet (hardware offload)? */
 132 #define _XEN_NETTXF_csum_blank          (0)
 133 #define  XEN_NETTXF_csum_blank          (1U<<_XEN_NETTXF_csum_blank)
 134
 135 /* Packet data has been validated against protocol checksum. */
 136 #define _XEN_NETTXF_data_validated      (1)
 137 #define  XEN_NETTXF_data_validated      (1U<<_XEN_NETTXF_data_validated)
 138
 139 /* Packet continues in the next request descriptor. */
 140 #define _XEN_NETTXF_more_data           (2)
 141 #define  XEN_NETTXF_more_data           (1U<<_XEN_NETTXF_more_data)
 142
 143 /* Packet to be followed by extra descriptor(s). */
 144 #define _XEN_NETTXF_extra_info          (3)
 145 #define  XEN_NETTXF_extra_info          (1U<<_XEN_NETTXF_extra_info)
 146
 147 #define XEN_NETIF_MAX_TX_SIZE 0xFFFF
 148 struct xen_netif_tx_request {
 149     grant_ref_t gref;      /* Reference to buffer page */
 150     uint16_t offset;       /* Offset within buffer page */
 151     uint16_t flags;        /* XEN_NETTXF_* */
 152     uint16_t id;           /* Echoed in response message. */
 153     uint16_t size;         /* Packet size in bytes.       */
 154 };
 155
 156 /* Types of xen_netif_extra_info descriptors. */
 157 #define XEN_NETIF_EXTRA_TYPE_NONE       (0)  /* Never used - invalid */
 158 #define XEN_NETIF_EXTRA_TYPE_GSO        (1)  /* u.gso */
 159 #define XEN_NETIF_EXTRA_TYPE_MAX        (2)
 160
 161 /* xen_netif_extra_info flags. */
 162 #define _XEN_NETIF_EXTRA_FLAG_MORE      (0)
 163 #define  XEN_NETIF_EXTRA_FLAG_MORE      (1U<<_XEN_NETIF_EXTRA_FLAG_MORE)
 164
 165 /* GSO types */
 166 #define XEN_NETIF_GSO_TYPE_NONE         (0)
 167 #define XEN_NETIF_GSO_TYPE_TCPV4        (1)
 168 #define XEN_NETIF_GSO_TYPE_TCPV6        (2)
 169
 170 /*
 171  * This structure needs to fit within both netif_tx_request and
 172  * netif_rx_response for compatibility.
 173  */
 174 struct xen_netif_extra_info {
 175         uint8_t type;  /* XEN_NETIF_EXTRA_TYPE_* */
 176         uint8_t flags; /* XEN_NETIF_EXTRA_FLAG_* */
 177
 178         union {
 179                 struct {
 180                         /*
 181                          * Maximum payload size of each segment. For
 182                          * example, for TCP this is just the path MSS.
 183                          */
 184                         uint16_t size;
 185
 186                         /*
 187                          * GSO type. This determines the protocol of
 188                          * the packet and any extra features required
 189                          * to segment the packet properly.
 190                          */
 191                         uint8_t type; /* XEN_NETIF_GSO_TYPE_* */
 192
 193                         /* Future expansion. */
 194                         uint8_t pad;
 195
 196                         /*
 197                          * GSO features. This specifies any extra GSO
 198                          * features required to process this packet,
 199                          * such as ECN support for TCPv4.
 200                          */
 201                         uint16_t features; /* XEN_NETIF_GSO_FEAT_* */
 202                 } gso;
 203
 204                 uint16_t pad[3];
 205         } u;
 206 };
 207
 208 struct xen_netif_tx_response {
 209         uint16_t id;
 210         int16_t  status;       /* XEN_NETIF_RSP_* */
 211 };
 212
 213 struct xen_netif_rx_request {
 214         uint16_t    id;        /* Echoed in response message.        */
 215         grant_ref_t gref;      /* Reference to incoming granted frame */
 216 };
 217
 218 /* Packet data has been validated against protocol checksum. */
 219 #define _XEN_NETRXF_data_validated      (0)
 220 #define  XEN_NETRXF_data_validated      (1U<<_XEN_NETRXF_data_validated)
 221
 222 /* Protocol checksum field is blank in the packet (hardware offload)? */
 223 #define _XEN_NETRXF_csum_blank          (1)
 224 #define  XEN_NETRXF_csum_blank          (1U<<_XEN_NETRXF_csum_blank)
 225
 226 /* Packet continues in the next request descriptor. */
 227 #define _XEN_NETRXF_more_data           (2)
 228 #define  XEN_NETRXF_more_data           (1U<<_XEN_NETRXF_more_data)
 229
 230 /* Packet to be followed by extra descriptor(s). */
 231 #define _XEN_NETRXF_extra_info          (3)
 232 #define  XEN_NETRXF_extra_info          (1U<<_XEN_NETRXF_extra_info)
 233
 234 /* GSO Prefix descriptor. */
 235 #define _XEN_NETRXF_gso_prefix          (4)
 236 #define  XEN_NETRXF_gso_prefix          (1U<<_XEN_NETRXF_gso_prefix)
 237
 238 struct xen_netif_rx_response {
 239     uint16_t id;
 240     uint16_t offset;       /* Offset in page of start of received packet  */
 241     uint16_t flags;        /* XEN_NETRXF_* */
 242     int16_t  status;       /* -ve: BLKIF_RSP_* ; +ve: Rx'ed pkt size. */
 243 };
 244
 245 /*
 246  * Generate netif ring structures and types.
 247  */
 248
 249 DEFINE_RING_TYPES(xen_netif_tx,
 250                   struct xen_netif_tx_request,
 251                   struct xen_netif_tx_response);
 252 DEFINE_RING_TYPES(xen_netif_rx,
 253                   struct xen_netif_rx_request,
 254                   struct xen_netif_rx_response);
 255
 256 #define XEN_NETIF_RSP_DROPPED   -2
 257 #define XEN_NETIF_RSP_ERROR     -1
 258 #define XEN_NETIF_RSP_OKAY       0
 259 /* No response: used for auxiliary requests (e.g., xen_netif_extra_info). */
 260 #define XEN_NETIF_RSP_NULL       1
 261
 262 #endif