zig

netmap.h (35558B) - Raw

---

 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
  * 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.
  */
 
 /*
  *
  * 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_ */