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

     /*
      * Copyright (C) 2011 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.
     * 
     *   3. Neither the name of the authors nor the names of their contributors
     *      may be used to endorse or promote products derived from this
     *      software without specific prior written permission.
     * 
     * THIS SOFTWARE IS PROVIDED BY MATTEO LANDI AND CONTRIBUTORS "AS 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 MATTEO LANDI 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: releng/9.1/sys/net/netmap.h 235549 2012-05-17 15:02:51Z luigi $
     * $Id: netmap.h 10601 2012-02-21 16:40:14Z luigi $
     *
     * 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/
     */
    
    #ifndef _NET_NETMAP_H_
    #define _NET_NETMAP_H_
    
    /*
     * --- Netmap data structures ---
     *
     * The data structures used by netmap are shown below. Those in
     * capital letters are in an mmapp()ed area shared with userspace,
     * while others are private to the kernel.
     * Shared structures do not contain pointers but only memory
     * offsets, so that addressing is portable between kernel and userspace.
    
    
     softc
    +----------------+
    | standard fields|
    | if_pspare[0] ----------+
    +----------------+       |
                             |
    +----------------+<------+
    |(netmap_adapter)|
    |                |                             netmap_kring
    | tx_rings *--------------------------------->+---------------+
    |                |       netmap_kring         | ring    *---------.
    | rx_rings *--------->+---------------+       | nr_hwcur      |   |
    +----------------+    | ring    *--------.    | nr_hwavail    |   V
                          | nr_hwcur      |  |    | selinfo       |   |
                          | nr_hwavail    |  |    +---------------+   .
                          | selinfo       |  |    |     ...       |   .
                          +---------------+  |    |(ntx+1 entries)|
                          |    ....       |  |    |               |
                          |(nrx+1 entries)|  |    +---------------+
                          |               |  |
       KERNEL             +---------------+  |
                                             |
      ====================================================================
                                             |
       USERSPACE                             |      NETMAP_RING
                                             +---->+-------------+
                                                 / | cur         |
       NETMAP_IF  (nifp, one per file desc.)    /  | avail       |
        +---------------+                      /   | buf_ofs     |
        | ni_tx_rings   |                     /    +=============+
        | ni_rx_rings   |                    /     | buf_idx     | slot[0]
        |               |                   /      | len, flags  |
        |               |                  /       +-------------+
        +===============+                 /        | buf_idx     | slot[1]
        | txring_ofs[0] | (rel.to nifp)--'         | len, flags  |
        | txring_ofs[1] |                          +-------------+
      (num_rings+1 entries)                     (nr_num_slots entries)
        | txring_ofs[n] |                          | buf_idx     | slot[n-1]
        +---------------+                          | len, flags  |
        | rxring_ofs[0] |                          +-------------+
        | rxring_ofs[1] |
      (num_rings+1 entries)
        | txring_ofs[n] |
       +---------------+
   
    * The private descriptor ('softc' or 'adapter') of each interface
    * is extended with a "struct netmap_adapter" containing netmap-related
    * info (see description in dev/netmap/netmap_kernel.h.
    * Among other things, tx_rings and rx_rings point to the arrays of
    * "struct netmap_kring" which in turn reache the various
    * "struct netmap_ring", shared with userspace.
   
    * The NETMAP_RING is the userspace-visible replica of the NIC ring.
    * Each slot has the index of a buffer, its length and some flags.
    * In user space, the buffer address is computed as
    *      (char *)ring + buf_ofs + index*NETMAP_BUF_SIZE
    * In the kernel, buffers do not necessarily need to be contiguous,
    * and the virtual and physical addresses are derived through
    * a lookup table.
    * To associate a different buffer to a slot, applications must
    * write the new index in buf_idx, and set NS_BUF_CHANGED flag to
    * make sure that the kernel updates the hardware ring as needed.
    *
    * Normally the driver is not requested to report the result of
    * transmissions (this can dramatically speed up operation).
    * However the user may request to report completion by setting
    * NS_REPORT.
    */
   struct netmap_slot {
           uint32_t buf_idx; /* buffer index */
           uint16_t len;   /* packet length, to be copied to/from the hw ring */
           uint16_t flags; /* buf changed, etc. */
   #define NS_BUF_CHANGED  0x0001  /* must resync the map, buffer changed */
   #define NS_REPORT       0x0002  /* ask the hardware to report results
                                    * e.g. by generating an interrupt
                                    */
   };
   
   /*
    * 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, two fields are important: avail and cur.
    *
    * In TX rings:
    *      avail   indicates the number of slots available for transmission.
    *              It is updated by the kernel after every netmap system call.
    *              It MUST BE decremented by the application when it appends a
    *              packet.
    *      cur     indicates the slot to use for the next packet
    *              to send (i.e. the "tail" of the queue).
    *              It MUST BE incremented by the application before
    *              netmap system calls to reflect the number of newly
    *              sent packets.
    *              It is checked by the kernel on netmap system calls
    *              (normally unmodified by the kernel unless invalid).
    *
    *   The kernel side of netmap uses two additional fields in its own
    *   private ring structure, netmap_kring:
    *      nr_hwcur is a copy of nr_cur on an NIOCTXSYNC.
    *      nr_hwavail is the number of slots known as available by the
    *              hardware. It is updated on an INTR (inc by the
    *              number of packets sent) and on a NIOCTXSYNC
    *              (decrease by nr_cur - nr_hwcur)
    *              A special case, nr_hwavail is -1 if the transmit
    *              side is idle (no pending transmits).
    *
    * In RX rings:
    *      avail   is the number of packets available (possibly 0).
    *              It MUST BE decremented by the application when it consumes
    *              a packet, and it is updated to nr_hwavail on a NIOCRXSYNC
    *      cur     indicates the first slot that contains a packet not
    *              processed yet (the "head" of the queue).
    *              It MUST BE incremented by the software when it consumes
    *              a packet.
    *      reserved        indicates the number of buffers before 'cur'
    *              that the application has still in use. Normally 0,
    *              it MUST BE incremented by the application when it
    *              does not return the buffer immediately, and decremented
    *              when the buffer is finally freed.
    *
    *   The kernel side of netmap uses two additional fields in the kring:
    *      nr_hwcur is a copy of nr_cur on an NIOCRXSYNC
    *      nr_hwavail is the number of packets available. It is updated
    *              on INTR (inc by the number of new packets arrived)
    *              and on NIOCRXSYNC (decreased by nr_cur - nr_hwcur).
    *
    * DATA OWNERSHIP/LOCKING:
    *      The netmap_ring is owned by the user program and it is only
    *      accessed or modified in the upper half of the kernel during
    *      a system call.
    *
    *      The netmap_kring is only modified by the upper half of the kernel.
    */
   struct netmap_ring {
           /*
            * nr_buf_base_ofs is meant to be used through macros.
            * It contains the offset of the buffer region from this
            * descriptor.
            */
           const ssize_t   buf_ofs;
           const uint32_t  num_slots;      /* number of slots in the ring. */
           uint32_t        avail;          /* number of usable slots */
           uint32_t        cur;            /* 'current' r/w position */
           uint32_t        reserved;       /* not refilled before current */
   
           const uint16_t  nr_buf_size;
           uint16_t        flags;
   #define NR_TIMESTAMP    0x0002          /* set timestamp on *sync() */
   
           struct timeval  ts;             /* time of last *sync() */
   
           /* the slots follow. This struct has variable size */
           struct netmap_slot slot[0];     /* array of slots. */
   };
   
   
   /*
    * Netmap representation of an interface and its queue(s).
    * There is one netmap_if for each file descriptor on which we want
    * to select/poll.  We assume that on each interface has the same number
    * of receive and transmit queues.
    * 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 u_int     ni_version;     /* API version, currently unused */
           const u_int     ni_rx_rings;    /* number of rx rings */
           const u_int     ni_tx_rings;    /* if zero, same as ni_rx_rings */
           /*
            * The following array contains the offset of each netmap ring
            * from this structure. The first ni_tx_queues+1 entries refer
            * to the tx rings, the next ni_rx_queues+1 refer to the rx rings
            * (the last entry in each block refers to the host stack rings).
            * The area is filled up by the kernel on NIOCREG,
            * and then only read by userspace code.
            */
           const ssize_t   ring_ofs[0];
   };
   
   #ifndef NIOCREGIF       
   /*
    * ioctl names and related fields
    *
    * NIOCGINFO takes a struct ifreq, the interface name is the input,
    *      the outputs are number of queues and number of descriptor
    *      for each queue (useful to set number of threads etc.).
    *
    * NIOCREGIF takes an interface name within a struct ifreq,
    *      and activates netmap mode on the interface (if possible).
    *
    * NIOCUNREGIF unregisters the interface associated to the fd.
    *
    * NIOCTXSYNC, NIOCRXSYNC synchronize tx or rx queues,
    *      whose identity is set in NIOCREGIF through nr_ringid
    */
   
   /*
    * struct nmreq overlays a struct ifreq
    */
   struct nmreq {
           char            nr_name[IFNAMSIZ];
           uint32_t        nr_version;     /* API version */
   #define NETMAP_API      3               /* current version */
           uint32_t        nr_offset;      /* nifp offset in the shared region */
           uint32_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_ringid;      /* ring(s) we care about */
   #define NETMAP_HW_RING  0x4000          /* low bits indicate one hw ring */
   #define NETMAP_SW_RING  0x2000          /* process the sw ring */
   #define NETMAP_NO_TX_POLL       0x1000  /* no automatic txsync on poll */
   #define NETMAP_RING_MASK 0xfff          /* the ring number */
           uint16_t        spare1;
           uint32_t        spare2[4];
   };
   
   /*
    * FreeBSD uses the size value embedded in the _IOWR to determine
    * how much to copy in/out. So we need it to match the actual
    * data structure we pass. We put some spares in the structure
    * to ease compatibility with other versions
    */
   #define NIOCGINFO       _IOWR('i', 145, struct nmreq) /* return IF info */
   #define NIOCREGIF       _IOWR('i', 146, struct nmreq) /* interface register */
   #define NIOCUNREGIF     _IO('i', 147) /* interface unregister */
   #define NIOCTXSYNC      _IO('i', 148) /* sync tx queues */
   #define NIOCRXSYNC      _IO('i', 149) /* sync rx queues */
   #endif /* !NIOCREGIF */
   
   #endif /* _NET_NETMAP_H_ */

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