FreeBSD/Linux Kernel Cross Reference
sys/net/netmap.h

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (C) 2011-2014 Matteo Landi, Luigi Rizzo. All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      *
     *   1. Redistributions of source code must retain the above copyright
     *      notice, this list of conditions and the following disclaimer.
     *   2. Redistributions in binary form must reproduce the above copyright
     *      notice, this list of conditions and the following disclaimer in the
     *      documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``S IS''AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    /*
     * $FreeBSD$
     *
     * Definitions of constants and the structures used by the netmap
     * framework, for the part visible to both kernel and userspace.
     * Detailed info on netmap is available with "man netmap" or at
     *
     *      http://info.iet.unipi.it/~luigi/netmap/
     *
     * This API is also used to communicate with the VALE software switch
     */
    
    #ifndef _NET_NETMAP_H_
    #define _NET_NETMAP_H_
    
    #define NETMAP_API      14              /* current API version */
    
    #define NETMAP_MIN_API  14              /* min and max versions accepted */
    #define NETMAP_MAX_API  15
    /*
     * Some fields should be cache-aligned to reduce contention.
     * The alignment is architecture and OS dependent, but rather than
     * digging into OS headers to find the exact value we use an estimate
     * that should cover most architectures.
     */
    #define NM_CACHE_ALIGN  128
    
    /*
     * --- Netmap data structures ---
     *
     * The userspace data structures used by netmap are shown below.
     * They are allocated by the kernel and mmap()ed by userspace threads.
     * Pointers are implemented as memory offsets or indexes,
     * so that they can be easily dereferenced in kernel and userspace.
    
       KERNEL (opaque, obviously)
    
      ====================================================================
                                              |
       USERSPACE                              |      struct netmap_ring
                                              +---->+---------------+
                                                  / | head,cur,tail |
       struct netmap_if (nifp, 1 per fd)         /  | buf_ofs       |
        +----------------+                      /   | other fields  |
        | ni_tx_rings    |                     /    +===============+
        | ni_rx_rings    |                    /     | buf_idx, len  | slot[0]
        |                |                   /      | flags, ptr    |
        |                |                  /       +---------------+
        +================+                 /        | buf_idx, len  | slot[1]
        | txring_ofs[0]  | (rel.to nifp)--'         | flags, ptr    |
        | txring_ofs[1]  |                          +---------------+
         (tx+htx entries)                           (num_slots entries)
        | txring_ofs[t]  |                          | buf_idx, len  | slot[n-1]
        +----------------+                          | flags, ptr    |
        | rxring_ofs[0]  |                          +---------------+
        | rxring_ofs[1]  |
         (rx+hrx entries)
        | rxring_ofs[r]  |
        +----------------+
    
     * For each "interface" (NIC, host stack, PIPE, VALE switch port) bound to
     * a file descriptor, the mmap()ed region contains a (logically readonly)
     * struct netmap_if pointing to struct netmap_ring's.
     *
     * There is one netmap_ring per physical NIC ring, plus at least one tx/rx ring
     * pair attached to the host stack (these pairs are unused for non-NIC ports).
     *
     * All physical/host stack ports share the same memory region,
     * so that zero-copy can be implemented between them.
     * VALE switch ports instead have separate memory regions.
     *
    * The netmap_ring is the userspace-visible replica of the NIC ring.
    * Each slot has the index of a buffer (MTU-sized and residing in the
    * mmapped region), its length and some flags. An extra 64-bit pointer
    * is provided for user-supplied buffers in the tx path.
    *
    * In user space, the buffer address is computed as
    *      (char *)ring + buf_ofs + index * NETMAP_BUF_SIZE
    *
    * Added in NETMAP_API 11:
    *
    * + NIOCREGIF can request the allocation of extra spare buffers from
    *   the same memory pool. The desired number of buffers must be in
    *   nr_arg3. The ioctl may return fewer buffers, depending on memory
    *   availability. nr_arg3 will return the actual value, and, once
    *   mapped, nifp->ni_bufs_head will be the index of the first buffer.
    *
    *   The buffers are linked to each other using the first uint32_t
    *   as the index. On close, ni_bufs_head must point to the list of
    *   buffers to be released.
    *
    * + NIOCREGIF can attach to PIPE rings sharing the same memory
    *   space with a parent device. The ifname indicates the parent device,
    *   which must already exist. Flags in nr_flags indicate if we want to
    *   bind the master or slave side, the index (from nr_ringid)
    *   is just a cookie and does not need to be sequential.
    *
    * + NIOCREGIF can also attach to 'monitor' rings that replicate
    *   the content of specific rings, also from the same memory space.
    *
    *   Extra flags in nr_flags support the above functions.
    *   Application libraries may use the following naming scheme:
    *      netmap:foo                      all NIC rings pairs
    *      netmap:foo^                     only host rings pairs
    *      netmap:foo^k                    the k-th host rings pair
    *      netmap:foo+                     all NIC rings + host rings pairs
    *      netmap:foo-k                    the k-th NIC rings pair
    *      netmap:foo{k                    PIPE rings pair k, master side
    *      netmap:foo}k                    PIPE rings pair k, slave side
    *
    * Some notes about host rings:
    *
    * + The RX host rings are used to store those packets that the host network
    *   stack is trying to transmit through a NIC queue, but only if that queue
    *   is currently in netmap mode. Netmap will not intercept host stack mbufs
    *   designated to NIC queues that are not in netmap mode. As a consequence,
    *   registering a netmap port with netmap:foo^ is not enough to intercept
    *   mbufs in the RX host rings; the netmap port should be registered with
    *   netmap:foo*, or another registration should be done to open at least a
    *   NIC TX queue in netmap mode.
    *
    * + Netmap is not currently able to deal with intercepted transmit mbufs which
    *   require offloadings like TSO, UFO, checksumming offloadings, etc. It is
    *   responsibility of the user to disable those offloadings (e.g. using
    *   ifconfig on FreeBSD or ethtool -K on Linux) for an interface that is being
    *   used in netmap mode. If the offloadings are not disabled, GSO and/or
    *   unchecksummed packets may be dropped immediately or end up in the host RX
    *   rings, and will be dropped as soon as the packet reaches another netmap
    *   adapter.
    */
   
   /*
    * struct netmap_slot is a buffer descriptor
    */
   struct netmap_slot {
           uint32_t buf_idx;       /* buffer index */
           uint16_t len;           /* length for this slot */
           uint16_t flags;         /* buf changed, etc. */
           uint64_t ptr;           /* pointer for indirect buffers */
   };
   
   /*
    * The following flags control how the slot is used
    */
   
   #define NS_BUF_CHANGED  0x0001  /* buf_idx changed */
           /*
            * must be set whenever buf_idx is changed (as it might be
            * necessary to recompute the physical address and mapping)
            *
            * It is also set by the kernel whenever the buf_idx is
            * changed internally (e.g., by pipes). Applications may
            * use this information to know when they can reuse the
            * contents of previously prepared buffers.
            */
   
   #define NS_REPORT       0x0002  /* ask the hardware to report results */
           /*
            * Request notification when slot is used by the hardware.
            * Normally transmit completions are handled lazily and
            * may be unreported. This flag lets us know when a slot
            * has been sent (e.g. to terminate the sender).
            */
   
   #define NS_FORWARD      0x0004  /* pass packet 'forward' */
           /*
            * (Only for physical ports, rx rings with NR_FORWARD set).
            * Slot released to the kernel (i.e. before ring->head) with
            * this flag set are passed to the peer ring (host/NIC),
            * thus restoring the host-NIC connection for these slots.
            * This supports efficient traffic monitoring or firewalling.
            */
   
   #define NS_NO_LEARN     0x0008  /* disable bridge learning */
           /*
            * On a VALE switch, do not 'learn' the source port for
            * this buffer.
            */
   
   #define NS_INDIRECT     0x0010  /* userspace buffer */
           /*
            * (VALE tx rings only) data is in a userspace buffer,
            * whose address is in the 'ptr' field in the slot.
            */
   
   #define NS_MOREFRAG     0x0020  /* packet has more fragments */
           /*
            * (VALE ports, ptnetmap ports and some NIC ports, e.g.
            * ixgbe and i40e on Linux)
            * Set on all but the last slot of a multi-segment packet.
            * The 'len' field refers to the individual fragment.
            */
   
   #define NS_TXMON        0x0040
           /* (monitor ports only) the packet comes from the TX
            * ring of the monitored port
            */
   
   #define NS_PORT_SHIFT   8
   #define NS_PORT_MASK    (0xff << NS_PORT_SHIFT)
           /*
            * The high 8 bits of the flag, if not zero, indicate the
            * destination port for the VALE switch, overriding
            * the lookup table.
            */
   
   #define NS_RFRAGS(_slot)        ( ((_slot)->flags >> 8) & 0xff)
           /*
            * (VALE rx rings only) the high 8 bits
            *  are the number of fragments.
            */
   
   #define NETMAP_MAX_FRAGS        64      /* max number of fragments */
   
   
   /*
    * struct netmap_ring
    *
    * Netmap representation of a TX or RX ring (also known as "queue").
    * This is a queue implemented as a fixed-size circular array.
    * At the software level the important fields are: head, cur, tail.
    *
    * In TX rings:
    *
    *      head    first slot available for transmission.
    *      cur     wakeup point. select() and poll() will unblock
    *              when 'tail' moves past 'cur'
    *      tail    (readonly) first slot reserved to the kernel
    *
    *      [head .. tail-1] can be used for new packets to send;
    *      'head' and 'cur' must be incremented as slots are filled
    *          with new packets to be sent;
    *      'cur' can be moved further ahead if we need more space
    *      for new transmissions. XXX todo (2014-03-12)
    *
    * In RX rings:
    *
    *      head    first valid received packet
    *      cur     wakeup point. select() and poll() will unblock
    *              when 'tail' moves past 'cur'
    *      tail    (readonly) first slot reserved to the kernel
    *
    *      [head .. tail-1] contain received packets;
    *      'head' and 'cur' must be incremented as slots are consumed
    *              and can be returned to the kernel;
    *      'cur' can be moved further ahead if we want to wait for
    *              new packets without returning the previous ones.
    *
    * DATA OWNERSHIP/LOCKING:
    *      The netmap_ring, and all slots and buffers in the range
    *      [head .. tail-1] are owned by the user program;
    *      the kernel only accesses them during a netmap system call
    *      and in the user thread context.
    *
    *      Other slots and buffers are reserved for use by the kernel
    */
   struct netmap_ring {
           /*
            * buf_ofs is meant to be used through macros.
            * It contains the offset of the buffer region from this
            * descriptor.
            */
           const int64_t   buf_ofs;
           const uint32_t  num_slots;      /* number of slots in the ring. */
           const uint32_t  nr_buf_size;
           const uint16_t  ringid;
           const uint16_t  dir;            /* 0: tx, 1: rx */
   
           uint32_t        head;           /* (u) first user slot */
           uint32_t        cur;            /* (u) wakeup point */
           uint32_t        tail;           /* (k) first kernel slot */
   
           uint32_t        flags;
   
           struct timeval  ts;             /* (k) time of last *sync() */
   
           /* offset_mask is used to isolate the part of the ptr field
            * in the slots used to contain an offset in the buffer.
            * It is zero if the ring has not be opened using the
            * NETMAP_REQ_OPT_OFFSETS option.
            */
           const uint64_t  offset_mask;
           /* the alignment requirement, in bytes, for the start
            * of the packets inside the buffers.
            * User programs should take this alignment into
            * account when specifying buffer-offsets in TX slots.
            */
           const uint64_t  buf_align;
   
           /* opaque room for a mutex or similar object */
   #if !defined(_WIN32) || defined(__CYGWIN__)
           uint8_t __attribute__((__aligned__(NM_CACHE_ALIGN))) sem[128];
   #else
           uint8_t __declspec(align(NM_CACHE_ALIGN)) sem[128];
   #endif
   
           /* the slots follow. This struct has variable size */
           struct netmap_slot slot[0];     /* array of slots. */
   };
   
   
   /*
    * RING FLAGS
    */
   #define NR_TIMESTAMP    0x0002          /* set timestamp on *sync() */
           /*
            * updates the 'ts' field on each netmap syscall. This saves
            * saves a separate gettimeofday(), and is not much worse than
            * software timestamps generated in the interrupt handler.
            */
   
   #define NR_FORWARD      0x0004          /* enable NS_FORWARD for ring */
           /*
            * Enables the NS_FORWARD slot flag for the ring.
            */
   
   /*
    * Helper functions for kernel and userspace
    */
   
   /*
    * Check if space is available in the ring. We use ring->head, which
    * points to the next netmap slot to be published to netmap. It is
    * possible that the applications moves ring->cur ahead of ring->tail
    * (e.g., by setting ring->cur <== ring->tail), if it wants more slots
    * than the ones currently available, and it wants to be notified when
    * more arrive. See netmap(4) for more details and examples.
    */
   static inline int
   nm_ring_empty(struct netmap_ring *ring)
   {
           return (ring->head == ring->tail);
   }
   
   /*
    * Netmap representation of an interface and its queue(s).
    * This is initialized by the kernel when binding a file
    * descriptor to a port, and should be considered as readonly
    * by user programs. The kernel never uses it.
    *
    * There is one netmap_if for each file descriptor on which we want
    * to select/poll.
    * select/poll operates on one or all pairs depending on the value of
    * nmr_queueid passed on the ioctl.
    */
   struct netmap_if {
           char            ni_name[IFNAMSIZ]; /* name of the interface. */
           const uint32_t  ni_version;     /* API version, currently unused */
           const uint32_t  ni_flags;       /* properties */
   #define NI_PRIV_MEM     0x1             /* private memory region */
   
           /*
            * The number of packet rings available in netmap mode.
            * Physical NICs can have different numbers of tx and rx rings.
            * Physical NICs also have at least a 'host' rings pair.
            * Additionally, clients can request additional ring pairs to
            * be used for internal communication.
            */
           const uint32_t  ni_tx_rings;    /* number of HW tx rings */
           const uint32_t  ni_rx_rings;    /* number of HW rx rings */
   
           uint32_t        ni_bufs_head;   /* head index for extra bufs */
           const uint32_t  ni_host_tx_rings; /* number of SW tx rings */
           const uint32_t  ni_host_rx_rings; /* number of SW rx rings */
           uint32_t        ni_spare1[3];
           /*
            * The following array contains the offset of each netmap ring
            * from this structure, in the following order:
            *     - NIC tx rings (ni_tx_rings);
            *     - host tx rings (ni_host_tx_rings);
            *     - NIC rx rings (ni_rx_rings);
            *     - host rx ring (ni_host_rx_rings);
            *
            * The area is filled up by the kernel on NETMAP_REQ_REGISTER,
            * and then only read by userspace code.
            */
           const ssize_t   ring_ofs[0];
   };
   
   /* Legacy interface to interact with a netmap control device.
    * Included for backward compatibility. The user should not include this
    * file directly. */
   #include "netmap_legacy.h"
   
   /*
    * New API to control netmap control devices. New applications should only use
    * nmreq_xyz structs with the NIOCCTRL ioctl() command.
    *
    * NIOCCTRL takes a nmreq_header struct, which contains the required
    * API version, the name of a netmap port, a command type, and pointers
    * to request body and options.
    *
    *      nr_name (in)
    *              The name of the port (em0, valeXXX:YYY, eth0{pn1 etc.)
    *
    *      nr_version (in/out)
    *              Must match NETMAP_API as used in the kernel, error otherwise.
    *              Always returns the desired value on output.
    *
    *      nr_reqtype (in)
    *              One of the NETMAP_REQ_* command types below
    *
    *      nr_body (in)
    *              Pointer to a command-specific struct, described by one
    *              of the struct nmreq_xyz below.
    *
    *      nr_options (in)
    *              Command specific options, if any.
    *
    * A NETMAP_REQ_REGISTER command activates netmap mode on the netmap
    * port (e.g. physical interface) specified by nmreq_header.nr_name.
    * The request body (struct nmreq_register) has several arguments to
    * specify how the port is to be registered.
    *
    *      nr_tx_slots, nr_tx_slots, nr_tx_rings, nr_rx_rings,
    *      nr_host_tx_rings, nr_host_rx_rings (in/out)
    *              On input, non-zero values may be used to reconfigure the port
    *              according to the requested values, but this is not guaranteed.
    *              On output the actual values in use are reported.
    *
    *      nr_mode (in)
    *              Indicate what set of rings must be bound to the netmap
    *              device (e.g. all NIC rings, host rings only, NIC and
    *              host rings, ...). Values are in NR_REG_*.
    *
    *      nr_ringid (in)
    *              If nr_mode == NR_REG_ONE_NIC (only a single couple of TX/RX
    *              rings), indicate which NIC TX and/or RX ring is to be bound
    *              (0..nr_*x_rings-1).
    *
    *      nr_flags (in)
    *              Indicate special options for how to open the port.
    *
    *              NR_NO_TX_POLL can be OR-ed to make select()/poll() push
    *                      packets on tx rings only if POLLOUT is set.
    *                      The default is to push any pending packet.
    *
    *              NR_DO_RX_POLL can be OR-ed to make select()/poll() release
    *                      packets on rx rings also when POLLIN is NOT set.
    *                      The default is to touch the rx ring only with POLLIN.
    *                      Note that this is the opposite of TX because it
    *                      reflects the common usage.
    *
    *              Other options are NR_MONITOR_TX, NR_MONITOR_RX, NR_ZCOPY_MON,
    *              NR_EXCLUSIVE, NR_RX_RINGS_ONLY, NR_TX_RINGS_ONLY and
    *              NR_ACCEPT_VNET_HDR.
    *
    *      nr_mem_id (in/out)
    *              The identity of the memory region used.
    *              On input, 0 means the system decides autonomously,
    *              other values may try to select a specific region.
    *              On return the actual value is reported.
    *              Region '1' is the global allocator, normally shared
    *              by all interfaces. Other values are private regions.
    *              If two ports the same region zero-copy is possible.
    *
    *      nr_extra_bufs (in/out)
    *              Number of extra buffers to be allocated.
    *
    * The other NETMAP_REQ_* commands are described below.
    *
    */
   
   /* maximum size of a request, including all options */
   #define NETMAP_REQ_MAXSIZE      4096
   
   /* Header common to all request options. */
   struct nmreq_option {
           /* Pointer to the next option. */
           uint64_t                nro_next;
           /* Option type. */
           uint32_t                nro_reqtype;
           /* (out) status of the option:
            * 0: recognized and processed
            * !=0: errno value
            */
           uint32_t                nro_status;
           /* Option size, used only for options that can have variable size
            * (e.g. because they contain arrays). For fixed-size options this
            * field should be set to zero. */
           uint64_t                nro_size;
   };
   
   /* Header common to all requests. Do not reorder these fields, as we need
    * the second one (nr_reqtype) to know how much to copy from/to userspace. */
   struct nmreq_header {
           uint16_t                nr_version;     /* API version */
           uint16_t                nr_reqtype;     /* nmreq type (NETMAP_REQ_*) */
           uint32_t                nr_reserved;    /* must be zero */
   #define NETMAP_REQ_IFNAMSIZ     64
           char                    nr_name[NETMAP_REQ_IFNAMSIZ]; /* port name */
           uint64_t                nr_options;     /* command-specific options */
           uint64_t                nr_body;        /* ptr to nmreq_xyz struct */
   };
   
   enum {
           /* Register a netmap port with the device. */
           NETMAP_REQ_REGISTER = 1,
           /* Get information from a netmap port. */
           NETMAP_REQ_PORT_INFO_GET,
           /* Attach a netmap port to a VALE switch. */
           NETMAP_REQ_VALE_ATTACH,
           /* Detach a netmap port from a VALE switch. */
           NETMAP_REQ_VALE_DETACH,
           /* List the ports attached to a VALE switch. */
           NETMAP_REQ_VALE_LIST,
           /* Set the port header length (was virtio-net header length). */
           NETMAP_REQ_PORT_HDR_SET,
           /* Get the port header length (was virtio-net header length). */
           NETMAP_REQ_PORT_HDR_GET,
           /* Create a new persistent VALE port. */
           NETMAP_REQ_VALE_NEWIF,
           /* Delete a persistent VALE port. */
           NETMAP_REQ_VALE_DELIF,
           /* Enable polling kernel thread(s) on an attached VALE port. */
           NETMAP_REQ_VALE_POLLING_ENABLE,
           /* Disable polling kernel thread(s) on an attached VALE port. */
           NETMAP_REQ_VALE_POLLING_DISABLE,
           /* Get info about the pools of a memory allocator. */
           NETMAP_REQ_POOLS_INFO_GET,
           /* Start an in-kernel loop that syncs the rings periodically or
            * on notifications. The loop runs in the context of the ioctl
            * syscall, and only stops on NETMAP_REQ_SYNC_KLOOP_STOP. */
           NETMAP_REQ_SYNC_KLOOP_START,
           /* Stops the thread executing the in-kernel loop. The thread
            * returns from the ioctl syscall. */
           NETMAP_REQ_SYNC_KLOOP_STOP,
           /* Enable CSB mode on a registered netmap control device. */
           NETMAP_REQ_CSB_ENABLE,
   };
   
   enum {
           /* On NETMAP_REQ_REGISTER, ask netmap to use memory allocated
            * from user-space allocated memory pools (e.g. hugepages).
            */
           NETMAP_REQ_OPT_EXTMEM = 1,
   
           /* ON NETMAP_REQ_SYNC_KLOOP_START, ask netmap to use eventfd-based
            * notifications to synchronize the kernel loop with the application.
            */
           NETMAP_REQ_OPT_SYNC_KLOOP_EVENTFDS,
   
           /* On NETMAP_REQ_REGISTER, ask netmap to work in CSB mode, where
            * head, cur and tail pointers are not exchanged through the
            * struct netmap_ring header, but rather using an user-provided
            * memory area (see struct nm_csb_atok and struct nm_csb_ktoa).
            */
           NETMAP_REQ_OPT_CSB,
   
           /* An extension to NETMAP_REQ_OPT_SYNC_KLOOP_EVENTFDS, which specifies
            * if the TX and/or RX rings are synced in the context of the VM exit.
            * This requires the 'ioeventfd' fields to be valid (cannot be < 0).
            */
           NETMAP_REQ_OPT_SYNC_KLOOP_MODE,
   
           /* On NETMAP_REQ_REGISTER, ask for (part of) the ptr field in the
            * slots of the registered rings to be used as an offset field
            * for the start of the packets inside the netmap buffer.
            */
           NETMAP_REQ_OPT_OFFSETS,
   
           /* This is a marker to count the number of available options.
            * New options must be added above it. */
           NETMAP_REQ_OPT_MAX,
   };
   
   /*
    * nr_reqtype: NETMAP_REQ_REGISTER
    * Bind (register) a netmap port to this control device.
    */
   struct nmreq_register {
           uint64_t        nr_offset;      /* nifp offset in the shared region */
           uint64_t        nr_memsize;     /* size of the shared region */
           uint32_t        nr_tx_slots;    /* slots in tx rings */
           uint32_t        nr_rx_slots;    /* slots in rx rings */
           uint16_t        nr_tx_rings;    /* number of tx rings */
           uint16_t        nr_rx_rings;    /* number of rx rings */
           uint16_t        nr_host_tx_rings; /* number of host tx rings */
           uint16_t        nr_host_rx_rings; /* number of host rx rings */
   
           uint16_t        nr_mem_id;      /* id of the memory allocator */
           uint16_t        nr_ringid;      /* ring(s) we care about */
           uint32_t        nr_mode;        /* specify NR_REG_* modes */
           uint32_t        nr_extra_bufs;  /* number of requested extra buffers */
   
           uint64_t        nr_flags;       /* additional flags (see below) */
   /* monitors use nr_ringid and nr_mode to select the rings to monitor */
   #define NR_MONITOR_TX   0x100
   #define NR_MONITOR_RX   0x200
   #define NR_ZCOPY_MON    0x400
   /* request exclusive access to the selected rings */
   #define NR_EXCLUSIVE    0x800
   /* 0x1000 unused */
   #define NR_RX_RINGS_ONLY        0x2000
   #define NR_TX_RINGS_ONLY        0x4000
   /* Applications set this flag if they are able to deal with virtio-net headers,
    * that is send/receive frames that start with a virtio-net header.
    * If not set, NETMAP_REQ_REGISTER will fail with netmap ports that require
    * applications to use those headers. If the flag is set, the application can
    * use the NETMAP_VNET_HDR_GET command to figure out the header length. */
   #define NR_ACCEPT_VNET_HDR      0x8000
   /* The following two have the same meaning of NETMAP_NO_TX_POLL and
    * NETMAP_DO_RX_POLL. */
   #define NR_DO_RX_POLL           0x10000
   #define NR_NO_TX_POLL           0x20000
   };
   
   /* Valid values for nmreq_register.nr_mode (see above). */
   enum {  NR_REG_DEFAULT  = 0,    /* backward compat, should not be used. */
           NR_REG_ALL_NIC  = 1,
           NR_REG_SW       = 2,
           NR_REG_NIC_SW   = 3,
           NR_REG_ONE_NIC  = 4,
           NR_REG_PIPE_MASTER = 5, /* deprecated, use "x{y" port name syntax */
           NR_REG_PIPE_SLAVE = 6,  /* deprecated, use "x}y" port name syntax */
           NR_REG_NULL     = 7,
           NR_REG_ONE_SW   = 8,
   };
   
   /* A single ioctl number is shared by all the new API command.
    * Demultiplexing is done using the hdr.nr_reqtype field.
    * FreeBSD uses the size value embedded in the _IOWR to determine
    * how much to copy in/out, so we define the ioctl() command
    * specifying only nmreq_header, and copyin/copyout the rest. */
   #define NIOCCTRL        _IOWR('i', 151, struct nmreq_header)
   
   /* The ioctl commands to sync TX/RX netmap rings.
    * NIOCTXSYNC, NIOCRXSYNC synchronize tx or rx queues,
    *      whose identity is set in NETMAP_REQ_REGISTER through nr_ringid.
    *      These are non blocking and take no argument. */
   #define NIOCTXSYNC      _IO('i', 148) /* sync tx queues */
   #define NIOCRXSYNC      _IO('i', 149) /* sync rx queues */
   
   /*
    * nr_reqtype: NETMAP_REQ_PORT_INFO_GET
    * Get information about a netmap port, including number of rings.
    * slots per ring, id of the memory allocator, etc. The netmap
    * control device used for this operation does not need to be bound
    * to a netmap port.
    */
   struct nmreq_port_info_get {
           uint64_t        nr_memsize;     /* size of the shared region */
           uint32_t        nr_tx_slots;    /* slots in tx rings */
           uint32_t        nr_rx_slots;    /* slots in rx rings */
           uint16_t        nr_tx_rings;    /* number of tx rings */
           uint16_t        nr_rx_rings;    /* number of rx rings */
           uint16_t        nr_host_tx_rings; /* number of host tx rings */
           uint16_t        nr_host_rx_rings; /* number of host rx rings */
           uint16_t        nr_mem_id;      /* memory allocator id (in/out) */
           uint16_t        pad[3];
   };
   
   #define NM_BDG_NAME             "vale"  /* prefix for bridge port name */
   
   /*
    * nr_reqtype: NETMAP_REQ_VALE_ATTACH
    * Attach a netmap port to a VALE switch. Both the name of the netmap
    * port and the VALE switch are specified through the nr_name argument.
    * The attach operation could need to register a port, so at least
    * the same arguments are available.
    * port_index will contain the index where the port has been attached.
    */
   struct nmreq_vale_attach {
           struct nmreq_register reg;
           uint32_t port_index;
           uint32_t pad1;
   };
   
   /*
    * nr_reqtype: NETMAP_REQ_VALE_DETACH
    * Detach a netmap port from a VALE switch. Both the name of the netmap
    * port and the VALE switch are specified through the nr_name argument.
    * port_index will contain the index where the port was attached.
    */
   struct nmreq_vale_detach {
           uint32_t port_index;
           uint32_t pad1;
   };
   
   /*
    * nr_reqtype: NETMAP_REQ_VALE_LIST
    * List the ports of a VALE switch.
    */
   struct nmreq_vale_list {
           /* Name of the VALE port (valeXXX:YYY) or empty. */
           uint16_t        nr_bridge_idx;
           uint16_t        pad1;
           uint32_t        nr_port_idx;
   };
   
   /*
    * nr_reqtype: NETMAP_REQ_PORT_HDR_SET or NETMAP_REQ_PORT_HDR_GET
    * Set or get the port header length of the port identified by hdr.nr_name.
    * The control device does not need to be bound to a netmap port.
    */
   struct nmreq_port_hdr {
           uint32_t        nr_hdr_len;
           uint32_t        pad1;
   };
   
   /*
    * nr_reqtype: NETMAP_REQ_VALE_NEWIF
    * Create a new persistent VALE port.
    */
   struct nmreq_vale_newif {
           uint32_t        nr_tx_slots;    /* slots in tx rings */
           uint32_t        nr_rx_slots;    /* slots in rx rings */
           uint16_t        nr_tx_rings;    /* number of tx rings */
           uint16_t        nr_rx_rings;    /* number of rx rings */
           uint16_t        nr_mem_id;      /* id of the memory allocator */
           uint16_t        pad1;
   };
   
   /*
    * nr_reqtype: NETMAP_REQ_VALE_POLLING_ENABLE or NETMAP_REQ_VALE_POLLING_DISABLE
    * Enable or disable polling kthreads on a VALE port.
    */
   struct nmreq_vale_polling {
           uint32_t        nr_mode;
   #define NETMAP_POLLING_MODE_SINGLE_CPU 1
   #define NETMAP_POLLING_MODE_MULTI_CPU 2
           uint32_t        nr_first_cpu_id;
           uint32_t        nr_num_polling_cpus;
           uint32_t        pad1;
   };
   
   /*
    * nr_reqtype: NETMAP_REQ_POOLS_INFO_GET
    * Get info about the pools of the memory allocator of the netmap
    * port specified by hdr.nr_name and nr_mem_id. The netmap control
    * device used for this operation does not need to be bound to a netmap
    * port.
    */
   struct nmreq_pools_info {
           uint64_t        nr_memsize;
           uint16_t        nr_mem_id; /* in/out argument */
           uint16_t        pad1[3];
           uint64_t        nr_if_pool_offset;
           uint32_t        nr_if_pool_objtotal;
           uint32_t        nr_if_pool_objsize;
           uint64_t        nr_ring_pool_offset;
           uint32_t        nr_ring_pool_objtotal;
           uint32_t        nr_ring_pool_objsize;
           uint64_t        nr_buf_pool_offset;
           uint32_t        nr_buf_pool_objtotal;
           uint32_t        nr_buf_pool_objsize;
   };
   
   /*
    * nr_reqtype: NETMAP_REQ_SYNC_KLOOP_START
    * Start an in-kernel loop that syncs the rings periodically or on
    * notifications. The loop runs in the context of the ioctl syscall,
    * and only stops on NETMAP_REQ_SYNC_KLOOP_STOP.
    * The registered netmap port must be open in CSB mode.
    */
   struct nmreq_sync_kloop_start {
           /* Sleeping is the default synchronization method for the kloop.
            * The 'sleep_us' field specifies how many microseconds to sleep for
            * when there is no work to do, before doing another kloop iteration.
            */
           uint32_t        sleep_us;
           uint32_t        pad1;
   };
   
   /* A CSB entry for the application --> kernel direction. */
   struct nm_csb_atok {
           uint32_t head;            /* AW+ KR+ the head of the appl netmap_ring */
           uint32_t cur;             /* AW+ KR+ the cur of the appl netmap_ring */
           uint32_t appl_need_kick;  /* AW+ KR+ kern --> appl notification enable */
           uint32_t sync_flags;      /* AW+ KR+ the flags of the appl [tx|rx]sync() */
           uint32_t pad[12];         /* pad to a 64 bytes cacheline */
   };
   
   /* A CSB entry for the application <-- kernel direction. */
   struct nm_csb_ktoa {
           uint32_t hwcur;           /* AR+ KW+ the hwcur of the kern netmap_kring */
           uint32_t hwtail;          /* AR+ KW+ the hwtail of the kern netmap_kring */
           uint32_t kern_need_kick;  /* AR+ KW+ appl-->kern notification enable */
           uint32_t pad[13];
   };
   
   #ifdef __linux__
   
   #ifdef __KERNEL__
   #define nm_stst_barrier smp_wmb
   #define nm_ldld_barrier smp_rmb
   #define nm_stld_barrier smp_mb
   #else  /* !__KERNEL__ */
   static inline void nm_stst_barrier(void)
   {
           /* A memory barrier with release semantic has the combined
            * effect of a store-store barrier and a load-store barrier,
            * which is fine for us. */
           __atomic_thread_fence(__ATOMIC_RELEASE);
   }
   static inline void nm_ldld_barrier(void)
   {
           /* A memory barrier with acquire semantic has the combined
            * effect of a load-load barrier and a store-load barrier,
            * which is fine for us. */
           __atomic_thread_fence(__ATOMIC_ACQUIRE);
   }
   #endif /* !__KERNEL__ */
   
   #elif defined(__FreeBSD__)
   
   #ifdef _KERNEL
   #define nm_stst_barrier atomic_thread_fence_rel
   #define nm_ldld_barrier atomic_thread_fence_acq
   #define nm_stld_barrier atomic_thread_fence_seq_cst
   #else  /* !_KERNEL */
   
   #ifdef __cplusplus
   #include <atomic>
   using std::memory_order_release;
   using std::memory_order_acquire;
   
   #else /* __cplusplus */
   #include <stdatomic.h>
   #endif /* __cplusplus */
   
   static inline void nm_stst_barrier(void)
   {
           atomic_thread_fence(memory_order_release);
   }
   static inline void nm_ldld_barrier(void)
   {
           atomic_thread_fence(memory_order_acquire);
   }
   #endif /* !_KERNEL */
   
   #else  /* !__linux__ && !__FreeBSD__ */
   #error "OS not supported"
   #endif /* !__linux__ && !__FreeBSD__ */
   
   /* Application side of sync-kloop: Write ring pointers (cur, head) to the CSB.
    * This routine is coupled with sync_kloop_kernel_read(). */
   static inline void
   nm_sync_kloop_appl_write(struct nm_csb_atok *atok, uint32_t cur,
                            uint32_t head)
   {
           /* Issue a first store-store barrier to make sure writes to the
            * netmap ring do not overcome updates on atok->cur and atok->head. */
           nm_stst_barrier();
   
           /*
            * We need to write cur and head to the CSB but we cannot do it atomically.
            * There is no way we can prevent the host from reading the updated value
            * of one of the two and the old value of the other. However, if we make
            * sure that the host never reads a value of head more recent than the
            * value of cur we are safe. We can allow the host to read a value of cur
            * more recent than the value of head, since in the netmap ring cur can be
            * ahead of head and cur cannot wrap around head because it must be behind
            * tail. Inverting the order of writes below could instead result into the
            * host to think head went ahead of cur, which would cause the sync
            * prologue to fail.
            *
            * The following memory barrier scheme is used to make this happen:
            *
            *          Guest                Host
            *
            *          STORE(cur)           LOAD(head)
            *          wmb() <----------->  rmb()
            *          STORE(head)          LOAD(cur)
            *
            */
           atok->cur = cur;
           nm_stst_barrier();
           atok->head = head;
   }
   
   /* Application side of sync-kloop: Read kring pointers (hwcur, hwtail) from
    * the CSB. This routine is coupled with sync_kloop_kernel_write(). */
   static inline void
   nm_sync_kloop_appl_read(struct nm_csb_ktoa *ktoa, uint32_t *hwtail,
                           uint32_t *hwcur)
   {
           /*
            * We place a memory barrier to make sure that the update of hwtail never
            * overtakes the update of hwcur.
            * (see explanation in sync_kloop_kernel_write).
            */
           *hwtail = ktoa->hwtail;
           nm_ldld_barrier();
           *hwcur = ktoa->hwcur;
   
           /* Make sure that loads from ktoa->hwtail and ktoa->hwcur are not delayed
            * after the loads from the netmap ring. */
           nm_ldld_barrier();
   }
   
   /*
    * data for NETMAP_REQ_OPT_* options
    */
   
   struct nmreq_opt_sync_kloop_eventfds {
           struct nmreq_option     nro_opt;        /* common header */
           /* An array of N entries for bidirectional notifications between
            * the kernel loop and the application. The number of entries and
            * their order must agree with the CSB arrays passed in the
            * NETMAP_REQ_OPT_CSB option. Each entry contains a file descriptor
            * backed by an eventfd.
            *
            * If any of the 'ioeventfd' entries is < 0, the event loop uses
            * the sleeping synchronization strategy (according to sleep_us),
            * and keeps kern_need_kick always disabled.
            * Each 'irqfd' can be < 0, and in that case the corresponding queue
            * is never notified.
            */
           struct {
                   /* Notifier for the application --> kernel loop direction. */
                   int32_t ioeventfd;
                   /* Notifier for the kernel loop --> application direction. */
                   int32_t irqfd;
           } eventfds[0];
   };
   
   struct nmreq_opt_sync_kloop_mode {
           struct nmreq_option     nro_opt;        /* common header */
   #define NM_OPT_SYNC_KLOOP_DIRECT_TX (1 << 0)
   #define NM_OPT_SYNC_KLOOP_DIRECT_RX (1 << 1)
           uint32_t mode;
   };
   
   struct nmreq_opt_extmem {
           struct nmreq_option     nro_opt;        /* common header */
           uint64_t                nro_usrptr;     /* (in) ptr to usr memory */
           struct nmreq_pools_info nro_info;       /* (in/out) */
   };
   
   struct nmreq_opt_csb {
           struct nmreq_option     nro_opt;
   
           /* Array of CSB entries for application --> kernel communication
            * (N entries). */
           uint64_t                csb_atok;
   
           /* Array of CSB entries for kernel --> application communication
            * (N entries). */
           uint64_t                csb_ktoa;
   };
   
   /* option NETMAP_REQ_OPT_OFFSETS */
   struct nmreq_opt_offsets {
           struct nmreq_option     nro_opt;
           /* the user must declare the maximum offset value that she is
            * going to put into the offset slot-fields. Any larger value
            * found at runtime will be cropped. On output the (possibly
            * higher) effective max value is returned.
            */
           uint64_t                nro_max_offset;
           /* optional initial offset value, to be set in all slots. */
           uint64_t                nro_initial_offset;
           /* number of bits in the lower part of the 'ptr' field to be
            * used as the offset field. On output the (possibly larger)
            * effective number of bits is returned.
            * 0 means: use the whole ptr field.
            */
           uint32_t                nro_offset_bits;
           /* required alignment for the beginning of the packets
            * (base of the buffer plus offset) in the TX slots.
            */
           uint32_t                nro_tx_align;
           /* Reserved: set to zero. */
           uint64_t                nro_min_gap;
   };
   
   #endif /* _NET_NETMAP_H_ */

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