Avoid shadowing local variable names.

[ovs.git] / lib / netdev-linux.c

/*
 * Copyright (c) 2009, 2010 Nicira Networks.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <config.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <arpa/inet.h>
#include <inttypes.h>
#include <linux/gen_stats.h>
#include <linux/if_tun.h>
#include <linux/ip.h>
#include <linux/types.h>
#include <linux/ethtool.h>
#include <linux/pkt_sched.h>
#include <linux/rtnetlink.h>
#include <linux/sockios.h>
#include <linux/version.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <linux/if_tunnel.h>
#include <net/if_arp.h>
#include <net/if_packet.h>
#include <net/route.h>
#include <netinet/in.h>
#include <poll.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "coverage.h"
#include "dynamic-string.h"
#include "fatal-signal.h"
#include "netdev-provider.h"
#include "netdev-vport.h"
#include "netlink.h"
#include "ofpbuf.h"
#include "openflow/openflow.h"
#include "packets.h"
#include "poll-loop.h"
#include "port-array.h"
#include "rtnetlink.h"
#include "socket-util.h"
#include "shash.h"
#include "svec.h"
#include "vlog.h"

VLOG_DEFINE_THIS_MODULE(netdev_linux)
\f
/* These were introduced in Linux 2.6.14, so they might be missing if we have
 * old headers. */
#ifndef ADVERTISED_Pause
#define ADVERTISED_Pause                (1 << 13)
#endif
#ifndef ADVERTISED_Asym_Pause
#define ADVERTISED_Asym_Pause           (1 << 14)
#endif

/* This was introduced in Linux 2.6.25, so it might be missing if we have old
 * headers. */
#ifndef TC_RTAB_SIZE
#define TC_RTAB_SIZE 1024
#endif

static struct rtnetlink_notifier netdev_linux_cache_notifier;
static int cache_notifier_refcount;

enum {
    VALID_IFINDEX           = 1 << 0,
    VALID_ETHERADDR         = 1 << 1,
    VALID_IN4               = 1 << 2,
    VALID_IN6               = 1 << 3,
    VALID_MTU               = 1 << 4,
    VALID_CARRIER           = 1 << 5,
    VALID_IS_PSEUDO         = 1 << 6, /* Represents is_internal and is_tap. */
    VALID_POLICING          = 1 << 7,
    VALID_HAVE_VPORT_STATS  = 1 << 8
};

struct tap_state {
    int fd;
    bool opened;
};
\f
/* Traffic control. */

/* An instance of a traffic control class.  Always associated with a particular
 * network device. */
struct tc {
    const struct tc_ops *ops;

    /* Maps from queue ID to tc-specific data.
     *
     * The generic netdev TC layer uses this to the following extent: if an
     * entry is nonnull, then the queue whose ID is the index is assumed to
     * exist; if an entry is null, then that queue is assumed not to exist.
     * Implementations must adhere to this scheme, although they may store
     * whatever they like as data.
     */
    struct port_array queues;
};

/* A particular kind of traffic control.  Each implementation generally maps to
 * one particular Linux qdisc class.
 *
 * The functions below return 0 if successful or a positive errno value on
 * failure, except where otherwise noted.  All of them must be provided, except
 * where otherwise noted. */
struct tc_ops {
    /* Name used by kernel in the TCA_KIND attribute of tcmsg, e.g. "htb".
     * This is null for tc_ops_default and tc_ops_other, for which there are no
     * appropriate values. */
    const char *linux_name;

    /* Name used in OVS database, e.g. "linux-htb".  Must be nonnull. */
    const char *ovs_name;

    /* Number of supported OpenFlow queues, 0 for qdiscs that have no
     * queues.  The queues are numbered 0 through n_queues - 1. */
    unsigned int n_queues;

    /* Called to install this TC class on 'netdev'.  The implementation should
     * make the Netlink calls required to set up 'netdev' with the right qdisc
     * and configure it according to 'details'.  The implementation may assume
     * that the current qdisc is the default; that is, there is no need for it
     * to delete the current qdisc before installing itself.
     *
     * The contents of 'details' should be documented as valid for 'ovs_name'
     * in the "other_config" column in the "QoS" table in vswitchd/vswitch.xml
     * (which is built as ovs-vswitchd.conf.db(8)).
     *
     * This function must return 0 if and only if it sets 'netdev->tc' to an
     * initialized 'struct tc'.
     *
     * (This function is null for tc_ops_other, which cannot be installed.  For
     * other TC classes it should always be nonnull.) */
    int (*tc_install)(struct netdev *netdev, const struct shash *details);

    /* Called when the netdev code determines (through a Netlink query) that
     * this TC class's qdisc is installed on 'netdev', but we didn't install
     * it ourselves and so don't know any of the details.
     *
     * 'nlmsg' is the kernel reply to a RTM_GETQDISC Netlink message for
     * 'netdev'.  The TCA_KIND attribute of 'nlmsg' is 'linux_name'.  The
     * implementation should parse the other attributes of 'nlmsg' as
     * necessary to determine its configuration.  If necessary it should also
     * use Netlink queries to determine the configuration of queues on
     * 'netdev'.
     *
     * This function must return 0 if and only if it sets 'netdev->tc' to an
     * initialized 'struct tc'. */
    int (*tc_load)(struct netdev *netdev, struct ofpbuf *nlmsg);

    /* Destroys the data structures allocated by the implementation as part of
     * 'tc'.  (This includes destroying 'tc->queues' by calling
     * tc_destroy(tc).
     *
     * The implementation should not need to perform any Netlink calls.  If
     * desirable, the caller is responsible for deconfiguring the kernel qdisc.
     * (But it may not be desirable.)
     *
     * This function may be null if 'tc' is trivial. */
    void (*tc_destroy)(struct tc *tc);

    /* Retrieves details of 'netdev->tc' configuration into 'details'.
     *
     * The implementation should not need to perform any Netlink calls, because
     * the 'tc_install' or 'tc_load' that instantiated 'netdev->tc' should have
     * cached the configuration.
     *
     * The contents of 'details' should be documented as valid for 'ovs_name'
     * in the "other_config" column in the "QoS" table in vswitchd/vswitch.xml
     * (which is built as ovs-vswitchd.conf.db(8)).
     *
     * This function may be null if 'tc' is not configurable.
     */
    int (*qdisc_get)(const struct netdev *netdev, struct shash *details);

    /* Reconfigures 'netdev->tc' according to 'details', performing any
     * required Netlink calls to complete the reconfiguration.
     *
     * The contents of 'details' should be documented as valid for 'ovs_name'
     * in the "other_config" column in the "QoS" table in vswitchd/vswitch.xml
     * (which is built as ovs-vswitchd.conf.db(8)).
     *
     * This function may be null if 'tc' is not configurable.
     */
    int (*qdisc_set)(struct netdev *, const struct shash *details);

    /* Retrieves details of 'queue_id' on 'netdev->tc' into 'details'.  The
     * caller ensures that 'queues' has a nonnull value for index 'queue_id.
     *
     * The contents of 'details' should be documented as valid for 'ovs_name'
     * in the "other_config" column in the "Queue" table in
     * vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
     *
     * The implementation should not need to perform any Netlink calls, because
     * the 'tc_install' or 'tc_load' that instantiated 'netdev->tc' should have
     * cached the queue configuration.
     *
     * This function may be null if 'tc' does not have queues ('n_queues' is
     * 0). */
    int (*class_get)(const struct netdev *netdev, unsigned int queue_id,
                     struct shash *details);

    /* Configures or reconfigures 'queue_id' on 'netdev->tc' according to
     * 'details', perfoming any required Netlink calls to complete the
     * reconfiguration.  The caller ensures that 'queue_id' is less than
     * 'n_queues'.
     *
     * The contents of 'details' should be documented as valid for 'ovs_name'
     * in the "other_config" column in the "Queue" table in
     * vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
     *
     * This function may be null if 'tc' does not have queues or its queues are
     * not configurable. */
    int (*class_set)(struct netdev *, unsigned int queue_id,
                     const struct shash *details);

    /* Deletes 'queue_id' from 'netdev->tc'.  The caller ensures that 'queues'
     * has a nonnull value for index 'queue_id.
     *
     * This function may be null if 'tc' does not have queues or its queues
     * cannot be deleted. */
    int (*class_delete)(struct netdev *, unsigned int queue_id);

    /* Obtains stats for 'queue' from 'netdev->tc'.  The caller ensures that
     * 'queues' has a nonnull value for index 'queue_id.
     *
     * On success, initializes '*stats'.
     *
     * This function may be null if 'tc' does not have queues or if it cannot
     * report queue statistics. */
    int (*class_get_stats)(const struct netdev *netdev, unsigned int queue_id,
                           struct netdev_queue_stats *stats);

    /* Extracts queue stats from 'nlmsg', which is a response to a
     * RTM_GETTCLASS message, and passes them to 'cb' along with 'aux'.
     *
     * This function may be null if 'tc' does not have queues or if it cannot
     * report queue statistics. */
    int (*class_dump_stats)(const struct netdev *netdev,
                            const struct ofpbuf *nlmsg,
                            netdev_dump_queue_stats_cb *cb, void *aux);
};

static void
tc_init(struct tc *tc, const struct tc_ops *ops)
{
    tc->ops = ops;
    port_array_init(&tc->queues);
}

static void
tc_destroy(struct tc *tc)
{
    port_array_destroy(&tc->queues);
}

static const struct tc_ops tc_ops_htb;
static const struct tc_ops tc_ops_default;
static const struct tc_ops tc_ops_other;

static const struct tc_ops *tcs[] = {
    &tc_ops_htb,                /* Hierarchy token bucket (see tc-htb(8)). */
    &tc_ops_default,            /* Default qdisc (see tc-pfifo_fast(8)). */
    &tc_ops_other,              /* Some other qdisc. */
    NULL
};

static unsigned int tc_make_handle(unsigned int major, unsigned int minor);
static unsigned int tc_get_major(unsigned int handle);
static unsigned int tc_get_minor(unsigned int handle);

static unsigned int tc_ticks_to_bytes(unsigned int rate, unsigned int ticks);
static unsigned int tc_bytes_to_ticks(unsigned int rate, unsigned int size);
static unsigned int tc_buffer_per_jiffy(unsigned int rate);

static struct tcmsg *tc_make_request(const struct netdev *, int type,
                                     unsigned int flags, struct ofpbuf *);
static int tc_transact(struct ofpbuf *request, struct ofpbuf **replyp);

static int tc_parse_qdisc(const struct ofpbuf *, const char **kind,
                          struct nlattr **options);
static int tc_parse_class(const struct ofpbuf *, unsigned int *queue_id,
                          struct nlattr **options,
                          struct netdev_queue_stats *);
static int tc_query_class(const struct netdev *,
                          unsigned int handle, unsigned int parent,
                          struct ofpbuf **replyp);
static int tc_delete_class(const struct netdev *, unsigned int handle);

static int tc_del_qdisc(struct netdev *netdev);
static int tc_query_qdisc(const struct netdev *netdev);

static int tc_calc_cell_log(unsigned int mtu);
static void tc_fill_rate(struct tc_ratespec *rate, uint64_t bps, int mtu);
static void tc_put_rtab(struct ofpbuf *, uint16_t type,
                        const struct tc_ratespec *rate);
static int tc_calc_buffer(unsigned int Bps, int mtu, uint64_t burst_bytes);
\f
struct netdev_dev_linux {
    struct netdev_dev netdev_dev;

    struct shash_node *shash_node;
    unsigned int cache_valid;

    /* The following are figured out "on demand" only.  They are only valid
     * when the corresponding VALID_* bit in 'cache_valid' is set. */
    int ifindex;
    uint8_t etheraddr[ETH_ADDR_LEN];
    struct in_addr address, netmask;
    struct in6_addr in6;
    int mtu;
    int carrier;
    bool is_internal;           /* Is this an openvswitch internal device? */
    bool is_tap;                /* Is this a tuntap device? */
    uint32_t kbits_rate;        /* Policing data. */
    uint32_t kbits_burst;
    bool have_vport_stats;
    struct tc *tc;

    union {
        struct tap_state tap;
    } state;
};

struct netdev_linux {
    struct netdev netdev;
    int fd;
};

/* An AF_INET socket (used for ioctl operations). */
static int af_inet_sock = -1;

/* A Netlink routing socket that is not subscribed to any multicast groups. */
static struct nl_sock *rtnl_sock;

struct netdev_linux_notifier {
    struct netdev_notifier notifier;
    struct list node;
};

static struct shash netdev_linux_notifiers =
    SHASH_INITIALIZER(&netdev_linux_notifiers);
static struct rtnetlink_notifier netdev_linux_poll_notifier;

/* This is set pretty low because we probably won't learn anything from the
 * additional log messages. */
static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 20);

static int netdev_linux_init(void);

static int netdev_linux_do_ethtool(const char *name, struct ethtool_cmd *,
                                   int cmd, const char *cmd_name);
static int netdev_linux_do_ioctl(const char *name, struct ifreq *, int cmd,
                                 const char *cmd_name);
static int netdev_linux_get_ipv4(const struct netdev *, struct in_addr *,
                                 int cmd, const char *cmd_name);
static int get_flags(const struct netdev *, int *flagsp);
static int set_flags(struct netdev *, int flags);
static int do_get_ifindex(const char *netdev_name);
static int get_ifindex(const struct netdev *, int *ifindexp);
static int do_set_addr(struct netdev *netdev,
                       int ioctl_nr, const char *ioctl_name,
                       struct in_addr addr);
static int get_etheraddr(const char *netdev_name, uint8_t ea[ETH_ADDR_LEN]);
static int set_etheraddr(const char *netdev_name, int hwaddr_family,
                         const uint8_t[ETH_ADDR_LEN]);
static int get_stats_via_netlink(int ifindex, struct netdev_stats *stats);
static int get_stats_via_proc(const char *netdev_name, struct netdev_stats *stats);

static bool
is_netdev_linux_class(const struct netdev_class *netdev_class)
{
    return netdev_class->init == netdev_linux_init;
}

static struct netdev_dev_linux *
netdev_dev_linux_cast(const struct netdev_dev *netdev_dev)
{
    const struct netdev_class *netdev_class = netdev_dev_get_class(netdev_dev);
    assert(is_netdev_linux_class(netdev_class));

    return CONTAINER_OF(netdev_dev, struct netdev_dev_linux, netdev_dev);
}

static struct netdev_linux *
netdev_linux_cast(const struct netdev *netdev)
{
    struct netdev_dev *netdev_dev = netdev_get_dev(netdev);
    const struct netdev_class *netdev_class = netdev_dev_get_class(netdev_dev);
    assert(is_netdev_linux_class(netdev_class));

    return CONTAINER_OF(netdev, struct netdev_linux, netdev);
}
\f
static int
netdev_linux_init(void)
{
    static int status = -1;
    if (status < 0) {
        /* Create AF_INET socket. */
        af_inet_sock = socket(AF_INET, SOCK_DGRAM, 0);
        status = af_inet_sock >= 0 ? 0 : errno;
        if (status) {
            VLOG_ERR("failed to create inet socket: %s", strerror(status));
        }

        /* Create rtnetlink socket. */
        if (!status) {
            status = nl_sock_create(NETLINK_ROUTE, 0, 0, 0, &rtnl_sock);
            if (status) {
                VLOG_ERR_RL(&rl, "failed to create rtnetlink socket: %s",
                            strerror(status));
            }
        }
    }
    return status;
}

static void
netdev_linux_run(void)
{
    rtnetlink_notifier_run();
}

static void
netdev_linux_wait(void)
{
    rtnetlink_notifier_wait();
}

static void
netdev_linux_cache_cb(const struct rtnetlink_change *change,
                      void *aux OVS_UNUSED)
{
    struct netdev_dev_linux *dev;
    if (change) {
        struct netdev_dev *base_dev = netdev_dev_from_name(change->ifname);
        if (base_dev) {
            const struct netdev_class *netdev_class =
                                                netdev_dev_get_class(base_dev);

            if (is_netdev_linux_class(netdev_class)) {
                dev = netdev_dev_linux_cast(base_dev);
                dev->cache_valid = 0;
            }
        }
    } else {
        struct shash device_shash;
        struct shash_node *node;

        shash_init(&device_shash);
        netdev_dev_get_devices(&netdev_linux_class, &device_shash);
        SHASH_FOR_EACH (node, &device_shash) {
            dev = node->data;
            dev->cache_valid = 0;
        }
        shash_destroy(&device_shash);
    }
}

/* Creates the netdev device of 'type' with 'name'. */
static int
netdev_linux_create_system(const char *name, const char *type OVS_UNUSED,
                    const struct shash *args, struct netdev_dev **netdev_devp)
{
    struct netdev_dev_linux *netdev_dev;
    int error;

    if (!shash_is_empty(args)) {
        VLOG_WARN("%s: arguments for system devices should be empty", name);
    }

    if (!cache_notifier_refcount) {
        error = rtnetlink_notifier_register(&netdev_linux_cache_notifier,
                                            netdev_linux_cache_cb, NULL);
        if (error) {
            return error;
        }
    }
    cache_notifier_refcount++;

    netdev_dev = xzalloc(sizeof *netdev_dev);
    netdev_dev_init(&netdev_dev->netdev_dev, name, &netdev_linux_class);

    *netdev_devp = &netdev_dev->netdev_dev;
    return 0;
}

/* For most types of netdevs we open the device for each call of
 * netdev_open().  However, this is not the case with tap devices,
 * since it is only possible to open the device once.  In this
 * situation we share a single file descriptor, and consequently
 * buffers, across all readers.  Therefore once data is read it will
 * be unavailable to other reads for tap devices. */
static int
netdev_linux_create_tap(const char *name, const char *type OVS_UNUSED,
                    const struct shash *args, struct netdev_dev **netdev_devp)
{
    struct netdev_dev_linux *netdev_dev;
    struct tap_state *state;
    static const char tap_dev[] = "/dev/net/tun";
    struct ifreq ifr;
    int error;

    if (!shash_is_empty(args)) {
        VLOG_WARN("%s: arguments for TAP devices should be empty", name);
    }

    netdev_dev = xzalloc(sizeof *netdev_dev);
    state = &netdev_dev->state.tap;

    /* Open tap device. */
    state->fd = open(tap_dev, O_RDWR);
    if (state->fd < 0) {
        error = errno;
        VLOG_WARN("opening \"%s\" failed: %s", tap_dev, strerror(error));
        goto error;
    }

    /* Create tap device. */
    ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
    strncpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
    if (ioctl(state->fd, TUNSETIFF, &ifr) == -1) {
        VLOG_WARN("%s: creating tap device failed: %s", name,
                  strerror(errno));
        error = errno;
        goto error;
    }

    /* Make non-blocking. */
    error = set_nonblocking(state->fd);
    if (error) {
        goto error;
    }

    netdev_dev_init(&netdev_dev->netdev_dev, name, &netdev_tap_class);
    *netdev_devp = &netdev_dev->netdev_dev;
    return 0;

error:
    free(netdev_dev);
    return error;
}

static void
destroy_tap(struct netdev_dev_linux *netdev_dev)
{
    struct tap_state *state = &netdev_dev->state.tap;

    if (state->fd >= 0) {
        close(state->fd);
    }
}

/* Destroys the netdev device 'netdev_dev_'. */
static void
netdev_linux_destroy(struct netdev_dev *netdev_dev_)
{
    struct netdev_dev_linux *netdev_dev = netdev_dev_linux_cast(netdev_dev_);
    const char *type = netdev_dev_get_type(netdev_dev_);

    if (netdev_dev->tc && netdev_dev->tc->ops->tc_destroy) {
        netdev_dev->tc->ops->tc_destroy(netdev_dev->tc);
    }

    if (!strcmp(type, "system")) {
        cache_notifier_refcount--;

        if (!cache_notifier_refcount) {
            rtnetlink_notifier_unregister(&netdev_linux_cache_notifier);
        }
    } else if (!strcmp(type, "tap")) {
        destroy_tap(netdev_dev);
    }

    free(netdev_dev);
}

static int
netdev_linux_open(struct netdev_dev *netdev_dev_, int ethertype,
                  struct netdev **netdevp)
{
    struct netdev_dev_linux *netdev_dev = netdev_dev_linux_cast(netdev_dev_);
    struct netdev_linux *netdev;
    enum netdev_flags flags;
    int error;

    /* Allocate network device. */
    netdev = xzalloc(sizeof *netdev);
    netdev->fd = -1;
    netdev_init(&netdev->netdev, netdev_dev_);

    error = netdev_get_flags(&netdev->netdev, &flags);
    if (error == ENODEV) {
        goto error;
    }

    if (!strcmp(netdev_dev_get_type(netdev_dev_), "tap") &&
        !netdev_dev->state.tap.opened) {

        /* We assume that the first user of the tap device is the primary user
         * and give them the tap FD.  Subsequent users probably just expect
         * this to be a system device so open it normally to avoid send/receive
         * directions appearing to be reversed. */
        netdev->fd = netdev_dev->state.tap.fd;
        netdev_dev->state.tap.opened = true;
    } else if (ethertype != NETDEV_ETH_TYPE_NONE) {
        struct sockaddr_ll sll;
        int protocol;
        int ifindex;

        /* Create file descriptor. */
        protocol = (ethertype == NETDEV_ETH_TYPE_ANY ? ETH_P_ALL
                    : ethertype == NETDEV_ETH_TYPE_802_2 ? ETH_P_802_2
                    : ethertype);
        netdev->fd = socket(PF_PACKET, SOCK_RAW, htons(protocol));
        if (netdev->fd < 0) {
            error = errno;
            goto error;
        }

        /* Set non-blocking mode. */
        error = set_nonblocking(netdev->fd);
        if (error) {
            goto error;
        }

        /* Get ethernet device index. */
        error = get_ifindex(&netdev->netdev, &ifindex);
        if (error) {
            goto error;
        }

        /* Bind to specific ethernet device. */
        memset(&sll, 0, sizeof sll);
        sll.sll_family = AF_PACKET;
        sll.sll_ifindex = ifindex;
        if (bind(netdev->fd,
                 (struct sockaddr *) &sll, sizeof sll) < 0) {
            error = errno;
            VLOG_ERR("bind to %s failed: %s", netdev_dev_get_name(netdev_dev_),
                     strerror(error));
            goto error;
        }

        /* Between the socket() and bind() calls above, the socket receives all
         * packets of the requested type on all system interfaces.  We do not
         * want to receive that data, but there is no way to avoid it.  So we
         * must now drain out the receive queue. */
        error = drain_rcvbuf(netdev->fd);
        if (error) {
            goto error;
        }
    }

    *netdevp = &netdev->netdev;
    return 0;

error:
    netdev_uninit(&netdev->netdev, true);
    return error;
}

/* Closes and destroys 'netdev'. */
static void
netdev_linux_close(struct netdev *netdev_)
{
    struct netdev_linux *netdev = netdev_linux_cast(netdev_);

    if (netdev->fd > 0 && strcmp(netdev_get_type(netdev_), "tap")) {
        close(netdev->fd);
    }
    free(netdev);
}

/* Initializes 'svec' with a list of the names of all known network devices. */
static int
netdev_linux_enumerate(struct svec *svec)
{
    struct if_nameindex *names;

    names = if_nameindex();
    if (names) {
        size_t i;

        for (i = 0; names[i].if_name != NULL; i++) {
            svec_add(svec, names[i].if_name);
        }
        if_freenameindex(names);
        return 0;
    } else {
        VLOG_WARN("could not obtain list of network device names: %s",
                  strerror(errno));
        return errno;
    }
}

static int
netdev_linux_recv(struct netdev *netdev_, void *data, size_t size)
{
    struct netdev_linux *netdev = netdev_linux_cast(netdev_);

    if (netdev->fd < 0) {
        /* Device was opened with NETDEV_ETH_TYPE_NONE. */
        return -EAGAIN;
    }

    for (;;) {
        ssize_t retval = read(netdev->fd, data, size);
        if (retval >= 0) {
            return retval;
        } else if (errno != EINTR) {
            if (errno != EAGAIN) {
                VLOG_WARN_RL(&rl, "error receiving Ethernet packet on %s: %s",
                             strerror(errno), netdev_get_name(netdev_));
            }
            return -errno;
        }
    }
}

/* Registers with the poll loop to wake up from the next call to poll_block()
 * when a packet is ready to be received with netdev_recv() on 'netdev'. */
static void
netdev_linux_recv_wait(struct netdev *netdev_)
{
    struct netdev_linux *netdev = netdev_linux_cast(netdev_);
    if (netdev->fd >= 0) {
        poll_fd_wait(netdev->fd, POLLIN);
    }
}

/* Discards all packets waiting to be received from 'netdev'. */
static int
netdev_linux_drain(struct netdev *netdev_)
{
    struct netdev_linux *netdev = netdev_linux_cast(netdev_);
    if (netdev->fd < 0) {
        return 0;
    } else if (!strcmp(netdev_get_type(netdev_), "tap")) {
        struct ifreq ifr;
        int error = netdev_linux_do_ioctl(netdev_get_name(netdev_), &ifr,
                                          SIOCGIFTXQLEN, "SIOCGIFTXQLEN");
        if (error) {
            return error;
        }
        drain_fd(netdev->fd, ifr.ifr_qlen);
        return 0;
    } else {
        return drain_rcvbuf(netdev->fd);
    }
}

/* Sends 'buffer' on 'netdev'.  Returns 0 if successful, otherwise a positive
 * errno value.  Returns EAGAIN without blocking if the packet cannot be queued
 * immediately.  Returns EMSGSIZE if a partial packet was transmitted or if
 * the packet is too big or too small to transmit on the device.
 *
 * The caller retains ownership of 'buffer' in all cases.
 *
 * The kernel maintains a packet transmission queue, so the caller is not
 * expected to do additional queuing of packets. */
static int
netdev_linux_send(struct netdev *netdev_, const void *data, size_t size)
{
    struct netdev_linux *netdev = netdev_linux_cast(netdev_);

    /* XXX should support sending even if 'ethertype' was NETDEV_ETH_TYPE_NONE.
     */
    if (netdev->fd < 0) {
        return EPIPE;
    }

    for (;;) {
        ssize_t retval = write(netdev->fd, data, size);
        if (retval < 0) {
            /* The Linux AF_PACKET implementation never blocks waiting for room
             * for packets, instead returning ENOBUFS.  Translate this into
             * EAGAIN for the caller. */
            if (errno == ENOBUFS) {
                return EAGAIN;
            } else if (errno == EINTR) {
                continue;
            } else if (errno != EAGAIN) {
                VLOG_WARN_RL(&rl, "error sending Ethernet packet on %s: %s",
                             netdev_get_name(netdev_), strerror(errno));
            }
            return errno;
        } else if (retval != size) {
            VLOG_WARN_RL(&rl, "sent partial Ethernet packet (%zd bytes of "
                         "%zu) on %s", retval, size, netdev_get_name(netdev_));
            return EMSGSIZE;
        } else {
            return 0;
        }
    }
}

/* Registers with the poll loop to wake up from the next call to poll_block()
 * when the packet transmission queue has sufficient room to transmit a packet
 * with netdev_send().
 *
 * The kernel maintains a packet transmission queue, so the client is not
 * expected to do additional queuing of packets.  Thus, this function is
 * unlikely to ever be used.  It is included for completeness. */
static void
netdev_linux_send_wait(struct netdev *netdev_)
{
    struct netdev_linux *netdev = netdev_linux_cast(netdev_);
    if (netdev->fd < 0) {
        /* Nothing to do. */
    } else if (strcmp(netdev_get_type(netdev_), "tap")) {
        poll_fd_wait(netdev->fd, POLLOUT);
    } else {
        /* TAP device always accepts packets.*/
        poll_immediate_wake();
    }
}

/* Attempts to set 'netdev''s MAC address to 'mac'.  Returns 0 if successful,
 * otherwise a positive errno value. */
static int
netdev_linux_set_etheraddr(struct netdev *netdev_,
                           const uint8_t mac[ETH_ADDR_LEN])
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev_));
    int error;

    if (!(netdev_dev->cache_valid & VALID_ETHERADDR)
        || !eth_addr_equals(netdev_dev->etheraddr, mac)) {
        error = set_etheraddr(netdev_get_name(netdev_), ARPHRD_ETHER, mac);
        if (!error) {
            netdev_dev->cache_valid |= VALID_ETHERADDR;
            memcpy(netdev_dev->etheraddr, mac, ETH_ADDR_LEN);
        }
    } else {
        error = 0;
    }
    return error;
}

/* Returns a pointer to 'netdev''s MAC address.  The caller must not modify or
 * free the returned buffer. */
static int
netdev_linux_get_etheraddr(const struct netdev *netdev_,
                           uint8_t mac[ETH_ADDR_LEN])
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev_));
    if (!(netdev_dev->cache_valid & VALID_ETHERADDR)) {
        int error = get_etheraddr(netdev_get_name(netdev_),
                                  netdev_dev->etheraddr);
        if (error) {
            return error;
        }
        netdev_dev->cache_valid |= VALID_ETHERADDR;
    }
    memcpy(mac, netdev_dev->etheraddr, ETH_ADDR_LEN);
    return 0;
}

/* Returns the maximum size of transmitted (and received) packets on 'netdev',
 * in bytes, not including the hardware header; thus, this is typically 1500
 * bytes for Ethernet devices. */
static int
netdev_linux_get_mtu(const struct netdev *netdev_, int *mtup)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev_));
    if (!(netdev_dev->cache_valid & VALID_MTU)) {
        struct ifreq ifr;
        int error;

        error = netdev_linux_do_ioctl(netdev_get_name(netdev_), &ifr,
                                      SIOCGIFMTU, "SIOCGIFMTU");
        if (error) {
            return error;
        }
        netdev_dev->mtu = ifr.ifr_mtu;
        netdev_dev->cache_valid |= VALID_MTU;
    }
    *mtup = netdev_dev->mtu;
    return 0;
}

/* Returns the ifindex of 'netdev', if successful, as a positive number.
 * On failure, returns a negative errno value. */
static int
netdev_linux_get_ifindex(const struct netdev *netdev)
{
    int ifindex, error;

    error = get_ifindex(netdev, &ifindex);
    return error ? -error : ifindex;
}

static int
netdev_linux_get_carrier(const struct netdev *netdev_, bool *carrier)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev_));
    int error = 0;
    char *fn = NULL;
    int fd = -1;

    if (!(netdev_dev->cache_valid & VALID_CARRIER)) {
        char line[8];
        int retval;

        fn = xasprintf("/sys/class/net/%s/carrier",
                       netdev_get_name(netdev_));
        fd = open(fn, O_RDONLY);
        if (fd < 0) {
            error = errno;
            VLOG_WARN_RL(&rl, "%s: open failed: %s", fn, strerror(error));
            goto exit;
        }

        retval = read(fd, line, sizeof line);
        if (retval < 0) {
            error = errno;
            if (error == EINVAL) {
                /* This is the normal return value when we try to check carrier
                 * if the network device is not up. */
            } else {
                VLOG_WARN_RL(&rl, "%s: read failed: %s", fn, strerror(error));
            }
            goto exit;
        } else if (retval == 0) {
            error = EPROTO;
            VLOG_WARN_RL(&rl, "%s: unexpected end of file", fn);
            goto exit;
        }

        if (line[0] != '0' && line[0] != '1') {
            error = EPROTO;
            VLOG_WARN_RL(&rl, "%s: value is %c (expected 0 or 1)",
                         fn, line[0]);
            goto exit;
        }
        netdev_dev->carrier = line[0] != '0';
        netdev_dev->cache_valid |= VALID_CARRIER;
    }
    *carrier = netdev_dev->carrier;
    error = 0;

exit:
    if (fd >= 0) {
        close(fd);
    }
    free(fn);
    return error;
}

/* Check whether we can we use RTM_GETLINK to get network device statistics.
 * In pre-2.6.19 kernels, this was only available if wireless extensions were
 * enabled. */
static bool
check_for_working_netlink_stats(void)
{
    /* Decide on the netdev_get_stats() implementation to use.  Netlink is
     * preferable, so if that works, we'll use it. */
    int ifindex = do_get_ifindex("lo");
    if (ifindex < 0) {
        VLOG_WARN("failed to get ifindex for lo, "
                  "obtaining netdev stats from proc");
        return false;
    } else {
        struct netdev_stats stats;
        int error = get_stats_via_netlink(ifindex, &stats);
        if (!error) {
            VLOG_DBG("obtaining netdev stats via rtnetlink");
            return true;
        } else {
            VLOG_INFO("RTM_GETLINK failed (%s), obtaining netdev stats "
                      "via proc (you are probably running a pre-2.6.19 "
                      "kernel)", strerror(error));
            return false;
        }
    }
}

/* Brings the 'is_internal' and 'is_tap' members of 'netdev_dev' up-to-date. */
static void
netdev_linux_update_is_pseudo(struct netdev_dev_linux *netdev_dev)
{
    if (!(netdev_dev->cache_valid & VALID_IS_PSEUDO)) {
        const char *name = netdev_dev_get_name(&netdev_dev->netdev_dev);
        const char *type = netdev_dev_get_type(&netdev_dev->netdev_dev);

        netdev_dev->is_tap = !strcmp(type, "tap");
        netdev_dev->is_internal = false;
        if (!netdev_dev->is_tap) {
            struct ethtool_drvinfo drvinfo;
            int error;

            memset(&drvinfo, 0, sizeof drvinfo);
            error = netdev_linux_do_ethtool(name,
                                            (struct ethtool_cmd *)&drvinfo,
                                            ETHTOOL_GDRVINFO,
                                            "ETHTOOL_GDRVINFO");

            if (!error && !strcmp(drvinfo.driver, "openvswitch")) {
                netdev_dev->is_internal = true;
            }
        }

        netdev_dev->cache_valid |= VALID_IS_PSEUDO;
    }
}

static void
swap_uint64(uint64_t *a, uint64_t *b)
{
    *a ^= *b;
    *b ^= *a;
    *a ^= *b;
}

/* Retrieves current device stats for 'netdev'. */
static int
netdev_linux_get_stats(const struct netdev *netdev_,
                       struct netdev_stats *stats)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev_));
    static int use_netlink_stats = -1;
    int error;

    COVERAGE_INC(netdev_get_stats);

    if (netdev_dev->have_vport_stats ||
        !(netdev_dev->cache_valid & VALID_HAVE_VPORT_STATS)) {

        error = netdev_vport_get_stats(netdev_, stats);
        netdev_dev->have_vport_stats = !error;
        netdev_dev->cache_valid |= VALID_HAVE_VPORT_STATS;
    }

    if (!netdev_dev->have_vport_stats) {
        if (use_netlink_stats < 0) {
            use_netlink_stats = check_for_working_netlink_stats();
        }
        if (use_netlink_stats) {
            int ifindex;

            error = get_ifindex(netdev_, &ifindex);
            if (!error) {
                error = get_stats_via_netlink(ifindex, stats);
            }
        } else {
            error = get_stats_via_proc(netdev_get_name(netdev_), stats);
        }
    }

    /* If this port is an internal port then the transmit and receive stats
     * will appear to be swapped relative to the other ports since we are the
     * one sending the data, not a remote computer.  For consistency, we swap
     * them back here. This does not apply if we are getting stats from the
     * vport layer because it always tracks stats from the perspective of the
     * switch. */
    netdev_linux_update_is_pseudo(netdev_dev);
    if (!error && !netdev_dev->have_vport_stats &&
        (netdev_dev->is_internal || netdev_dev->is_tap)) {
        swap_uint64(&stats->rx_packets, &stats->tx_packets);
        swap_uint64(&stats->rx_bytes, &stats->tx_bytes);
        swap_uint64(&stats->rx_errors, &stats->tx_errors);
        swap_uint64(&stats->rx_dropped, &stats->tx_dropped);
        stats->rx_length_errors = 0;
        stats->rx_over_errors = 0;
        stats->rx_crc_errors = 0;
        stats->rx_frame_errors = 0;
        stats->rx_fifo_errors = 0;
        stats->rx_missed_errors = 0;
        stats->tx_aborted_errors = 0;
        stats->tx_carrier_errors = 0;
        stats->tx_fifo_errors = 0;
        stats->tx_heartbeat_errors = 0;
        stats->tx_window_errors = 0;
    }

    return error;
}

/* Stores the features supported by 'netdev' into each of '*current',
 * '*advertised', '*supported', and '*peer' that are non-null.  Each value is a
 * bitmap of "enum ofp_port_features" bits, in host byte order.  Returns 0 if
 * successful, otherwise a positive errno value. */
static int
netdev_linux_get_features(struct netdev *netdev,
                          uint32_t *current, uint32_t *advertised,
                          uint32_t *supported, uint32_t *peer)
{
    struct ethtool_cmd ecmd;
    int error;

    memset(&ecmd, 0, sizeof ecmd);
    error = netdev_linux_do_ethtool(netdev_get_name(netdev), &ecmd,
                                    ETHTOOL_GSET, "ETHTOOL_GSET");
    if (error) {
        return error;
    }

    /* Supported features. */
    *supported = 0;
    if (ecmd.supported & SUPPORTED_10baseT_Half) {
        *supported |= OFPPF_10MB_HD;
    }
    if (ecmd.supported & SUPPORTED_10baseT_Full) {
        *supported |= OFPPF_10MB_FD;
    }
    if (ecmd.supported & SUPPORTED_100baseT_Half)  {
        *supported |= OFPPF_100MB_HD;
    }
    if (ecmd.supported & SUPPORTED_100baseT_Full) {
        *supported |= OFPPF_100MB_FD;
    }
    if (ecmd.supported & SUPPORTED_1000baseT_Half) {
        *supported |= OFPPF_1GB_HD;
    }
    if (ecmd.supported & SUPPORTED_1000baseT_Full) {
        *supported |= OFPPF_1GB_FD;
    }
    if (ecmd.supported & SUPPORTED_10000baseT_Full) {
        *supported |= OFPPF_10GB_FD;
    }
    if (ecmd.supported & SUPPORTED_TP) {
        *supported |= OFPPF_COPPER;
    }
    if (ecmd.supported & SUPPORTED_FIBRE) {
        *supported |= OFPPF_FIBER;
    }
    if (ecmd.supported & SUPPORTED_Autoneg) {
        *supported |= OFPPF_AUTONEG;
    }
    if (ecmd.supported & SUPPORTED_Pause) {
        *supported |= OFPPF_PAUSE;
    }
    if (ecmd.supported & SUPPORTED_Asym_Pause) {
        *supported |= OFPPF_PAUSE_ASYM;
    }

    /* Advertised features. */
    *advertised = 0;
    if (ecmd.advertising & ADVERTISED_10baseT_Half) {
        *advertised |= OFPPF_10MB_HD;
    }
    if (ecmd.advertising & ADVERTISED_10baseT_Full) {
        *advertised |= OFPPF_10MB_FD;
    }
    if (ecmd.advertising & ADVERTISED_100baseT_Half) {
        *advertised |= OFPPF_100MB_HD;
    }
    if (ecmd.advertising & ADVERTISED_100baseT_Full) {
        *advertised |= OFPPF_100MB_FD;
    }
    if (ecmd.advertising & ADVERTISED_1000baseT_Half) {
        *advertised |= OFPPF_1GB_HD;
    }
    if (ecmd.advertising & ADVERTISED_1000baseT_Full) {
        *advertised |= OFPPF_1GB_FD;
    }
    if (ecmd.advertising & ADVERTISED_10000baseT_Full) {
        *advertised |= OFPPF_10GB_FD;
    }
    if (ecmd.advertising & ADVERTISED_TP) {
        *advertised |= OFPPF_COPPER;
    }
    if (ecmd.advertising & ADVERTISED_FIBRE) {
        *advertised |= OFPPF_FIBER;
    }
    if (ecmd.advertising & ADVERTISED_Autoneg) {
        *advertised |= OFPPF_AUTONEG;
    }
    if (ecmd.advertising & ADVERTISED_Pause) {
        *advertised |= OFPPF_PAUSE;
    }
    if (ecmd.advertising & ADVERTISED_Asym_Pause) {
        *advertised |= OFPPF_PAUSE_ASYM;
    }

    /* Current settings. */
    if (ecmd.speed == SPEED_10) {
        *current = ecmd.duplex ? OFPPF_10MB_FD : OFPPF_10MB_HD;
    } else if (ecmd.speed == SPEED_100) {
        *current = ecmd.duplex ? OFPPF_100MB_FD : OFPPF_100MB_HD;
    } else if (ecmd.speed == SPEED_1000) {
        *current = ecmd.duplex ? OFPPF_1GB_FD : OFPPF_1GB_HD;
    } else if (ecmd.speed == SPEED_10000) {
        *current = OFPPF_10GB_FD;
    } else {
        *current = 0;
    }

    if (ecmd.port == PORT_TP) {
        *current |= OFPPF_COPPER;
    } else if (ecmd.port == PORT_FIBRE) {
        *current |= OFPPF_FIBER;
    }

    if (ecmd.autoneg) {
        *current |= OFPPF_AUTONEG;
    }

    /* Peer advertisements. */
    *peer = 0;                  /* XXX */

    return 0;
}

/* Set the features advertised by 'netdev' to 'advertise'. */
static int
netdev_linux_set_advertisements(struct netdev *netdev, uint32_t advertise)
{
    struct ethtool_cmd ecmd;
    int error;

    memset(&ecmd, 0, sizeof ecmd);
    error = netdev_linux_do_ethtool(netdev_get_name(netdev), &ecmd,
                                    ETHTOOL_GSET, "ETHTOOL_GSET");
    if (error) {
        return error;
    }

    ecmd.advertising = 0;
    if (advertise & OFPPF_10MB_HD) {
        ecmd.advertising |= ADVERTISED_10baseT_Half;
    }
    if (advertise & OFPPF_10MB_FD) {
        ecmd.advertising |= ADVERTISED_10baseT_Full;
    }
    if (advertise & OFPPF_100MB_HD) {
        ecmd.advertising |= ADVERTISED_100baseT_Half;
    }
    if (advertise & OFPPF_100MB_FD) {
        ecmd.advertising |= ADVERTISED_100baseT_Full;
    }
    if (advertise & OFPPF_1GB_HD) {
        ecmd.advertising |= ADVERTISED_1000baseT_Half;
    }
    if (advertise & OFPPF_1GB_FD) {
        ecmd.advertising |= ADVERTISED_1000baseT_Full;
    }
    if (advertise & OFPPF_10GB_FD) {
        ecmd.advertising |= ADVERTISED_10000baseT_Full;
    }
    if (advertise & OFPPF_COPPER) {
        ecmd.advertising |= ADVERTISED_TP;
    }
    if (advertise & OFPPF_FIBER) {
        ecmd.advertising |= ADVERTISED_FIBRE;
    }
    if (advertise & OFPPF_AUTONEG) {
        ecmd.advertising |= ADVERTISED_Autoneg;
    }
    if (advertise & OFPPF_PAUSE) {
        ecmd.advertising |= ADVERTISED_Pause;
    }
    if (advertise & OFPPF_PAUSE_ASYM) {
        ecmd.advertising |= ADVERTISED_Asym_Pause;
    }
    return netdev_linux_do_ethtool(netdev_get_name(netdev), &ecmd,
                                   ETHTOOL_SSET, "ETHTOOL_SSET");
}

/* If 'netdev_name' is the name of a VLAN network device (e.g. one created with
 * vconfig(8)), sets '*vlan_vid' to the VLAN VID associated with that device
 * and returns 0.  Otherwise returns a errno value (specifically ENOENT if
 * 'netdev_name' is the name of a network device that is not a VLAN device) and
 * sets '*vlan_vid' to -1. */
static int
netdev_linux_get_vlan_vid(const struct netdev *netdev, int *vlan_vid)
{
    const char *netdev_name = netdev_get_name(netdev);
    struct ds line = DS_EMPTY_INITIALIZER;
    FILE *stream = NULL;
    int error;
    char *fn;

    COVERAGE_INC(netdev_get_vlan_vid);
    fn = xasprintf("/proc/net/vlan/%s", netdev_name);
    stream = fopen(fn, "r");
    if (!stream) {
        error = errno;
        goto done;
    }

    if (ds_get_line(&line, stream)) {
        if (ferror(stream)) {
            error = errno;
            VLOG_ERR_RL(&rl, "error reading \"%s\": %s", fn, strerror(errno));
        } else {
            error = EPROTO;
            VLOG_ERR_RL(&rl, "unexpected end of file reading \"%s\"", fn);
        }
        goto done;
    }

    if (!sscanf(ds_cstr(&line), "%*s VID: %d", vlan_vid)) {
        error = EPROTO;
        VLOG_ERR_RL(&rl, "parse error reading \"%s\" line 1: \"%s\"",
                    fn, ds_cstr(&line));
        goto done;
    }

    error = 0;

done:
    free(fn);
    if (stream) {
        fclose(stream);
    }
    ds_destroy(&line);
    if (error) {
        *vlan_vid = -1;
    }
    return error;
}

#define POLICE_ADD_CMD "/sbin/tc qdisc add dev %s handle ffff: ingress"
#define POLICE_CONFIG_CMD "/sbin/tc filter add dev %s parent ffff: protocol ip prio 50 u32 match ip src 0.0.0.0/0 police rate %dkbit burst %dk mtu 65535 drop flowid :1"

/* Remove ingress policing from 'netdev'.  Returns 0 if successful, otherwise a
 * positive errno value.
 *
 * This function is equivalent to running
 *     /sbin/tc qdisc del dev %s handle ffff: ingress
 * but it is much, much faster.
 */
static int
netdev_linux_remove_policing(struct netdev *netdev)
{
    struct netdev_dev_linux *netdev_dev =
        netdev_dev_linux_cast(netdev_get_dev(netdev));
    const char *netdev_name = netdev_get_name(netdev);

    struct ofpbuf request;
    struct tcmsg *tcmsg;
    int error;

    tcmsg = tc_make_request(netdev, RTM_DELQDISC, 0, &request);
    tcmsg->tcm_handle = tc_make_handle(0xffff, 0);
    tcmsg->tcm_parent = TC_H_INGRESS;
    nl_msg_put_string(&request, TCA_KIND, "ingress");
    nl_msg_put_unspec(&request, TCA_OPTIONS, NULL, 0);

    error = tc_transact(&request, NULL);
    if (error && error != ENOENT && error != EINVAL) {
        VLOG_WARN_RL(&rl, "%s: removing policing failed: %s",
                     netdev_name, strerror(error));
        return error;
    }

    netdev_dev->kbits_rate = 0;
    netdev_dev->kbits_burst = 0;
    netdev_dev->cache_valid |= VALID_POLICING;
    return 0;
}

/* Attempts to set input rate limiting (policing) policy. */
static int
netdev_linux_set_policing(struct netdev *netdev,
                          uint32_t kbits_rate, uint32_t kbits_burst)
{
    struct netdev_dev_linux *netdev_dev =
        netdev_dev_linux_cast(netdev_get_dev(netdev));
    const char *netdev_name = netdev_get_name(netdev);
    char command[1024];

    COVERAGE_INC(netdev_set_policing);

    kbits_burst = (!kbits_rate ? 0       /* Force to 0 if no rate specified. */
                   : !kbits_burst ? 1000 /* Default to 1000 kbits if 0. */
                   : kbits_burst);       /* Stick with user-specified value. */

    if (netdev_dev->cache_valid & VALID_POLICING
        && netdev_dev->kbits_rate == kbits_rate
        && netdev_dev->kbits_burst == kbits_burst) {
        /* Assume that settings haven't changed since we last set them. */
        return 0;
    }

    netdev_linux_remove_policing(netdev);
    if (kbits_rate) {
        snprintf(command, sizeof(command), POLICE_ADD_CMD, netdev_name);
        if (system(command) != 0) {
            VLOG_WARN_RL(&rl, "%s: problem adding policing", netdev_name);
            return -1;
        }

        snprintf(command, sizeof(command), POLICE_CONFIG_CMD, netdev_name,
                kbits_rate, kbits_burst);
        if (system(command) != 0) {
            VLOG_WARN_RL(&rl, "%s: problem configuring policing",
                    netdev_name);
            return -1;
        }

        netdev_dev->kbits_rate = kbits_rate;
        netdev_dev->kbits_burst = kbits_burst;
        netdev_dev->cache_valid |= VALID_POLICING;
    }

    return 0;
}

static int
netdev_linux_get_qos_types(const struct netdev *netdev OVS_UNUSED,
                           struct svec *types)
{
    const struct tc_ops **opsp;

    for (opsp = tcs; *opsp != NULL; opsp++) {
        const struct tc_ops *ops = *opsp;
        if (ops->tc_install && ops->ovs_name[0] != '\0') {
            svec_add(types, ops->ovs_name);
        }
    }
    return 0;
}

static const struct tc_ops *
tc_lookup_ovs_name(const char *name)
{
    const struct tc_ops **opsp;

    for (opsp = tcs; *opsp != NULL; opsp++) {
        const struct tc_ops *ops = *opsp;
        if (!strcmp(name, ops->ovs_name)) {
            return ops;
        }
    }
    return NULL;
}

static const struct tc_ops *
tc_lookup_linux_name(const char *name)
{
    const struct tc_ops **opsp;

    for (opsp = tcs; *opsp != NULL; opsp++) {
        const struct tc_ops *ops = *opsp;
        if (ops->linux_name && !strcmp(name, ops->linux_name)) {
            return ops;
        }
    }
    return NULL;
}

static int
netdev_linux_get_qos_capabilities(const struct netdev *netdev OVS_UNUSED,
                                  const char *type,
                                  struct netdev_qos_capabilities *caps)
{
    const struct tc_ops *ops = tc_lookup_ovs_name(type);
    if (!ops) {
        return EOPNOTSUPP;
    }
    caps->n_queues = ops->n_queues;
    return 0;
}

static int
netdev_linux_get_qos(const struct netdev *netdev,
                     const char **typep, struct shash *details)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    int error;

    error = tc_query_qdisc(netdev);
    if (error) {
        return error;
    }

    *typep = netdev_dev->tc->ops->ovs_name;
    return (netdev_dev->tc->ops->qdisc_get
            ? netdev_dev->tc->ops->qdisc_get(netdev, details)
            : 0);
}

static int
netdev_linux_set_qos(struct netdev *netdev,
                     const char *type, const struct shash *details)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    const struct tc_ops *new_ops;
    int error;

    new_ops = tc_lookup_ovs_name(type);
    if (!new_ops || !new_ops->tc_install) {
        return EOPNOTSUPP;
    }

    error = tc_query_qdisc(netdev);
    if (error) {
        return error;
    }

    if (new_ops == netdev_dev->tc->ops) {
        return new_ops->qdisc_set ? new_ops->qdisc_set(netdev, details) : 0;
    } else {
        /* Delete existing qdisc. */
        error = tc_del_qdisc(netdev);
        if (error) {
            return error;
        }
        assert(netdev_dev->tc == NULL);

        /* Install new qdisc. */
        error = new_ops->tc_install(netdev, details);
        assert((error == 0) == (netdev_dev->tc != NULL));

        return error;
    }
}

static int
netdev_linux_get_queue(const struct netdev *netdev,
                       unsigned int queue_id, struct shash *details)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    int error;

    error = tc_query_qdisc(netdev);
    if (error) {
        return error;
    } else if (queue_id > UINT16_MAX
               || !port_array_get(&netdev_dev->tc->queues, queue_id)) {
        return ENOENT;
    }

    return netdev_dev->tc->ops->class_get(netdev, queue_id, details);
}

static int
netdev_linux_set_queue(struct netdev *netdev,
                       unsigned int queue_id, const struct shash *details)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    int error;

    error = tc_query_qdisc(netdev);
    if (error) {
        return error;
    } else if (queue_id >= netdev_dev->tc->ops->n_queues
               || !netdev_dev->tc->ops->class_set) {
        return EINVAL;
    }

    return netdev_dev->tc->ops->class_set(netdev, queue_id, details);
}

static int
netdev_linux_delete_queue(struct netdev *netdev, unsigned int queue_id)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    int error;

    error = tc_query_qdisc(netdev);
    if (error) {
        return error;
    } else if (!netdev_dev->tc->ops->class_delete) {
        return EINVAL;
    } else if (queue_id > UINT16_MAX
               || !port_array_get(&netdev_dev->tc->queues, queue_id)) {
        return ENOENT;
    }

    return netdev_dev->tc->ops->class_delete(netdev, queue_id);
}

static int
netdev_linux_get_queue_stats(const struct netdev *netdev,
                             unsigned int queue_id,
                             struct netdev_queue_stats *stats)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    int error;

    error = tc_query_qdisc(netdev);
    if (error) {
        return error;
    } else if (queue_id > UINT16_MAX
               || !port_array_get(&netdev_dev->tc->queues, queue_id)) {
        return ENOENT;
    } else if (!netdev_dev->tc->ops->class_get_stats) {
        return EOPNOTSUPP;
    }

    return netdev_dev->tc->ops->class_get_stats(netdev, queue_id, stats);
}

static void
start_queue_dump(const struct netdev *netdev, struct nl_dump *dump)
{
    struct ofpbuf request;
    struct tcmsg *tcmsg;

    tcmsg = tc_make_request(netdev, RTM_GETTCLASS, 0, &request);
    tcmsg->tcm_parent = 0;
    nl_dump_start(dump, rtnl_sock, &request);
    ofpbuf_uninit(&request);
}

static int
netdev_linux_dump_queues(const struct netdev *netdev,
                         netdev_dump_queues_cb *cb, void *aux)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    unsigned int queue_id;
    struct shash details;
    int last_error;
    void *queue;
    int error;

    error = tc_query_qdisc(netdev);
    if (error) {
        return error;
    } else if (!netdev_dev->tc->ops->class_get) {
        return EOPNOTSUPP;
    }

    last_error = 0;
    shash_init(&details);
    PORT_ARRAY_FOR_EACH (queue, &netdev_dev->tc->queues, queue_id) {
        shash_clear(&details);

        error = netdev_dev->tc->ops->class_get(netdev, queue_id, &details);
        if (!error) {
            (*cb)(queue_id, &details, aux);
        } else {
            last_error = error;
        }
    }
    shash_destroy(&details);

    return last_error;
}

static int
netdev_linux_dump_queue_stats(const struct netdev *netdev,
                              netdev_dump_queue_stats_cb *cb, void *aux)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    struct nl_dump dump;
    struct ofpbuf msg;
    int last_error;
    int error;

    error = tc_query_qdisc(netdev);
    if (error) {
        return error;
    } else if (!netdev_dev->tc->ops->class_dump_stats) {
        return EOPNOTSUPP;
    }

    last_error = 0;
    start_queue_dump(netdev, &dump);
    while (nl_dump_next(&dump, &msg)) {
        error = netdev_dev->tc->ops->class_dump_stats(netdev, &msg, cb, aux);
        if (error) {
            last_error = error;
        }
    }

    error = nl_dump_done(&dump);
    return error ? error : last_error;
}

static int
netdev_linux_get_in4(const struct netdev *netdev_,
                     struct in_addr *address, struct in_addr *netmask)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev_));

    if (!(netdev_dev->cache_valid & VALID_IN4)) {
        int error;

        error = netdev_linux_get_ipv4(netdev_, &netdev_dev->address,
                                      SIOCGIFADDR, "SIOCGIFADDR");
        if (error) {
            return error;
        }

        error = netdev_linux_get_ipv4(netdev_, &netdev_dev->netmask,
                                      SIOCGIFNETMASK, "SIOCGIFNETMASK");
        if (error) {
            return error;
        }

        netdev_dev->cache_valid |= VALID_IN4;
    }
    *address = netdev_dev->address;
    *netmask = netdev_dev->netmask;
    return address->s_addr == INADDR_ANY ? EADDRNOTAVAIL : 0;
}

static int
netdev_linux_set_in4(struct netdev *netdev_, struct in_addr address,
                     struct in_addr netmask)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev_));
    int error;

    error = do_set_addr(netdev_, SIOCSIFADDR, "SIOCSIFADDR", address);
    if (!error) {
        netdev_dev->cache_valid |= VALID_IN4;
        netdev_dev->address = address;
        netdev_dev->netmask = netmask;
        if (address.s_addr != INADDR_ANY) {
            error = do_set_addr(netdev_, SIOCSIFNETMASK,
                                "SIOCSIFNETMASK", netmask);
        }
    }
    return error;
}

static bool
parse_if_inet6_line(const char *line,
                    struct in6_addr *in6, char ifname[16 + 1])
{
    uint8_t *s6 = in6->s6_addr;
#define X8 "%2"SCNx8
    return sscanf(line,
                  " "X8 X8 X8 X8 X8 X8 X8 X8 X8 X8 X8 X8 X8 X8 X8 X8
                  "%*x %*x %*x %*x %16s\n",
                  &s6[0], &s6[1], &s6[2], &s6[3],
                  &s6[4], &s6[5], &s6[6], &s6[7],
                  &s6[8], &s6[9], &s6[10], &s6[11],
                  &s6[12], &s6[13], &s6[14], &s6[15],
                  ifname) == 17;
}

/* If 'netdev' has an assigned IPv6 address, sets '*in6' to that address (if
 * 'in6' is non-null) and returns true.  Otherwise, returns false. */
static int
netdev_linux_get_in6(const struct netdev *netdev_, struct in6_addr *in6)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev_));
    if (!(netdev_dev->cache_valid & VALID_IN6)) {
        FILE *file;
        char line[128];

        netdev_dev->in6 = in6addr_any;

        file = fopen("/proc/net/if_inet6", "r");
        if (file != NULL) {
            const char *name = netdev_get_name(netdev_);
            while (fgets(line, sizeof line, file)) {
                struct in6_addr in6_tmp;
                char ifname[16 + 1];
                if (parse_if_inet6_line(line, &in6_tmp, ifname)
                    && !strcmp(name, ifname))
                {
                    netdev_dev->in6 = in6_tmp;
                    break;
                }
            }
            fclose(file);
        }
        netdev_dev->cache_valid |= VALID_IN6;
    }
    *in6 = netdev_dev->in6;
    return 0;
}

static void
make_in4_sockaddr(struct sockaddr *sa, struct in_addr addr)
{
    struct sockaddr_in sin;
    memset(&sin, 0, sizeof sin);
    sin.sin_family = AF_INET;
    sin.sin_addr = addr;
    sin.sin_port = 0;

    memset(sa, 0, sizeof *sa);
    memcpy(sa, &sin, sizeof sin);
}

static int
do_set_addr(struct netdev *netdev,
            int ioctl_nr, const char *ioctl_name, struct in_addr addr)
{
    struct ifreq ifr;
    strncpy(ifr.ifr_name, netdev_get_name(netdev), sizeof ifr.ifr_name);
    make_in4_sockaddr(&ifr.ifr_addr, addr);

    return netdev_linux_do_ioctl(netdev_get_name(netdev), &ifr, ioctl_nr,
                                 ioctl_name);
}

/* Adds 'router' as a default IP gateway. */
static int
netdev_linux_add_router(struct netdev *netdev OVS_UNUSED, struct in_addr router)
{
    struct in_addr any = { INADDR_ANY };
    struct rtentry rt;
    int error;

    memset(&rt, 0, sizeof rt);
    make_in4_sockaddr(&rt.rt_dst, any);
    make_in4_sockaddr(&rt.rt_gateway, router);
    make_in4_sockaddr(&rt.rt_genmask, any);
    rt.rt_flags = RTF_UP | RTF_GATEWAY;
    COVERAGE_INC(netdev_add_router);
    error = ioctl(af_inet_sock, SIOCADDRT, &rt) < 0 ? errno : 0;
    if (error) {
        VLOG_WARN("ioctl(SIOCADDRT): %s", strerror(error));
    }
    return error;
}

static int
netdev_linux_get_next_hop(const struct in_addr *host, struct in_addr *next_hop,
                          char **netdev_name)
{
    static const char fn[] = "/proc/net/route";
    FILE *stream;
    char line[256];
    int ln;

    *netdev_name = NULL;
    stream = fopen(fn, "r");
    if (stream == NULL) {
        VLOG_WARN_RL(&rl, "%s: open failed: %s", fn, strerror(errno));
        return errno;
    }

    ln = 0;
    while (fgets(line, sizeof line, stream)) {
        if (++ln >= 2) {
            char iface[17];
            uint32_t dest, gateway, mask;
            int refcnt, metric, mtu;
            unsigned int flags, use, window, irtt;

            if (sscanf(line,
                       "%16s %"SCNx32" %"SCNx32" %04X %d %u %d %"SCNx32
                       " %d %u %u\n",
                       iface, &dest, &gateway, &flags, &refcnt,
                       &use, &metric, &mask, &mtu, &window, &irtt) != 11) {

                VLOG_WARN_RL(&rl, "%s: could not parse line %d: %s",
                        fn, ln, line);
                continue;
            }
            if (!(flags & RTF_UP)) {
                /* Skip routes that aren't up. */
                continue;
            }

            /* The output of 'dest', 'mask', and 'gateway' were given in
             * network byte order, so we don't need need any endian
             * conversions here. */
            if ((dest & mask) == (host->s_addr & mask)) {
                if (!gateway) {
                    /* The host is directly reachable. */
                    next_hop->s_addr = 0;
                } else {
                    /* To reach the host, we must go through a gateway. */
                    next_hop->s_addr = gateway;
                }
                *netdev_name = xstrdup(iface);
                fclose(stream);
                return 0;
            }
        }
    }

    fclose(stream);
    return ENXIO;
}

/* Looks up the ARP table entry for 'ip' on 'netdev'.  If one exists and can be
 * successfully retrieved, it stores the corresponding MAC address in 'mac' and
 * returns 0.  Otherwise, it returns a positive errno value; in particular,
 * ENXIO indicates that there is not ARP table entry for 'ip' on 'netdev'. */
static int
netdev_linux_arp_lookup(const struct netdev *netdev,
                        uint32_t ip, uint8_t mac[ETH_ADDR_LEN])
{
    struct arpreq r;
    struct sockaddr_in sin;
    int retval;

    memset(&r, 0, sizeof r);
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = ip;
    sin.sin_port = 0;
    memcpy(&r.arp_pa, &sin, sizeof sin);
    r.arp_ha.sa_family = ARPHRD_ETHER;
    r.arp_flags = 0;
    strncpy(r.arp_dev, netdev_get_name(netdev), sizeof r.arp_dev);
    COVERAGE_INC(netdev_arp_lookup);
    retval = ioctl(af_inet_sock, SIOCGARP, &r) < 0 ? errno : 0;
    if (!retval) {
        memcpy(mac, r.arp_ha.sa_data, ETH_ADDR_LEN);
    } else if (retval != ENXIO) {
        VLOG_WARN_RL(&rl, "%s: could not look up ARP entry for "IP_FMT": %s",
                     netdev_get_name(netdev), IP_ARGS(&ip), strerror(retval));
    }
    return retval;
}

static int
nd_to_iff_flags(enum netdev_flags nd)
{
    int iff = 0;
    if (nd & NETDEV_UP) {
        iff |= IFF_UP;
    }
    if (nd & NETDEV_PROMISC) {
        iff |= IFF_PROMISC;
    }
    return iff;
}

static int
iff_to_nd_flags(int iff)
{
    enum netdev_flags nd = 0;
    if (iff & IFF_UP) {
        nd |= NETDEV_UP;
    }
    if (iff & IFF_PROMISC) {
        nd |= NETDEV_PROMISC;
    }
    return nd;
}

static int
netdev_linux_update_flags(struct netdev *netdev, enum netdev_flags off,
                          enum netdev_flags on, enum netdev_flags *old_flagsp)
{
    int old_flags, new_flags;
    int error;

    error = get_flags(netdev, &old_flags);
    if (!error) {
        *old_flagsp = iff_to_nd_flags(old_flags);
        new_flags = (old_flags & ~nd_to_iff_flags(off)) | nd_to_iff_flags(on);
        if (new_flags != old_flags) {
            error = set_flags(netdev, new_flags);
        }
    }
    return error;
}

static void
poll_notify(struct list *list)
{
    struct netdev_linux_notifier *notifier;
    LIST_FOR_EACH (notifier, struct netdev_linux_notifier, node, list) {
        struct netdev_notifier *n = &notifier->notifier;
        n->cb(n);
    }
}

static void
netdev_linux_poll_cb(const struct rtnetlink_change *change,
                     void *aux OVS_UNUSED)
{
    if (change) {
        struct list *list = shash_find_data(&netdev_linux_notifiers,
                                            change->ifname);
        if (list) {
            poll_notify(list);
        }
    } else {
        struct shash_node *node;
        SHASH_FOR_EACH (node, &netdev_linux_notifiers) {
            poll_notify(node->data);
        }
    }
}

static int
netdev_linux_poll_add(struct netdev *netdev,
                      void (*cb)(struct netdev_notifier *), void *aux,
                      struct netdev_notifier **notifierp)
{
    const char *netdev_name = netdev_get_name(netdev);
    struct netdev_linux_notifier *notifier;
    struct list *list;

    if (shash_is_empty(&netdev_linux_notifiers)) {
        int error = rtnetlink_notifier_register(&netdev_linux_poll_notifier,
                                                   netdev_linux_poll_cb, NULL);
        if (error) {
            return error;
        }
    }

    list = shash_find_data(&netdev_linux_notifiers, netdev_name);
    if (!list) {
        list = xmalloc(sizeof *list);
        list_init(list);
        shash_add(&netdev_linux_notifiers, netdev_name, list);
    }

    notifier = xmalloc(sizeof *notifier);
    netdev_notifier_init(&notifier->notifier, netdev, cb, aux);
    list_push_back(list, &notifier->node);
    *notifierp = &notifier->notifier;
    return 0;
}

static void
netdev_linux_poll_remove(struct netdev_notifier *notifier_)
{
    struct netdev_linux_notifier *notifier =
        CONTAINER_OF(notifier_, struct netdev_linux_notifier, notifier);
    struct list *list;

    /* Remove 'notifier' from its list. */
    list = list_remove(&notifier->node);
    if (list_is_empty(list)) {
        /* The list is now empty.  Remove it from the hash and free it. */
        const char *netdev_name = netdev_get_name(notifier->notifier.netdev);
        shash_delete(&netdev_linux_notifiers,
                     shash_find(&netdev_linux_notifiers, netdev_name));
        free(list);
    }
    free(notifier);

    /* If that was the last notifier, unregister. */
    if (shash_is_empty(&netdev_linux_notifiers)) {
        rtnetlink_notifier_unregister(&netdev_linux_poll_notifier);
    }
}

const struct netdev_class netdev_linux_class = {
    "system",

    netdev_linux_init,
    netdev_linux_run,
    netdev_linux_wait,

    netdev_linux_create_system,
    netdev_linux_destroy,
    NULL,                       /* reconfigure */

    netdev_linux_open,
    netdev_linux_close,

    netdev_linux_enumerate,

    netdev_linux_recv,
    netdev_linux_recv_wait,
    netdev_linux_drain,

    netdev_linux_send,
    netdev_linux_send_wait,

    netdev_linux_set_etheraddr,
    netdev_linux_get_etheraddr,
    netdev_linux_get_mtu,
    netdev_linux_get_ifindex,
    netdev_linux_get_carrier,
    netdev_linux_get_stats,
    netdev_vport_set_stats,

    netdev_linux_get_features,
    netdev_linux_set_advertisements,
    netdev_linux_get_vlan_vid,

    netdev_linux_set_policing,
    netdev_linux_get_qos_types,
    netdev_linux_get_qos_capabilities,
    netdev_linux_get_qos,
    netdev_linux_set_qos,
    netdev_linux_get_queue,
    netdev_linux_set_queue,
    netdev_linux_delete_queue,
    netdev_linux_get_queue_stats,
    netdev_linux_dump_queues,
    netdev_linux_dump_queue_stats,

    netdev_linux_get_in4,
    netdev_linux_set_in4,
    netdev_linux_get_in6,
    netdev_linux_add_router,
    netdev_linux_get_next_hop,
    netdev_linux_arp_lookup,

    netdev_linux_update_flags,

    netdev_linux_poll_add,
    netdev_linux_poll_remove,
};

const struct netdev_class netdev_tap_class = {
    "tap",

    netdev_linux_init,
    netdev_linux_run,
    netdev_linux_wait,

    netdev_linux_create_tap,
    netdev_linux_destroy,
    NULL,                       /* reconfigure */

    netdev_linux_open,
    netdev_linux_close,

    NULL,                       /* enumerate */

    netdev_linux_recv,
    netdev_linux_recv_wait,
    netdev_linux_drain,

    netdev_linux_send,
    netdev_linux_send_wait,

    netdev_linux_set_etheraddr,
    netdev_linux_get_etheraddr,
    netdev_linux_get_mtu,
    netdev_linux_get_ifindex,
    netdev_linux_get_carrier,
    netdev_linux_get_stats,
    NULL,                       /* set_stats */

    netdev_linux_get_features,
    netdev_linux_set_advertisements,
    netdev_linux_get_vlan_vid,

    netdev_linux_set_policing,
    netdev_linux_get_qos_types,
    netdev_linux_get_qos_capabilities,
    netdev_linux_get_qos,
    netdev_linux_set_qos,
    netdev_linux_get_queue,
    netdev_linux_set_queue,
    netdev_linux_delete_queue,
    netdev_linux_get_queue_stats,
    netdev_linux_dump_queues,
    netdev_linux_dump_queue_stats,

    netdev_linux_get_in4,
    netdev_linux_set_in4,
    netdev_linux_get_in6,
    netdev_linux_add_router,
    netdev_linux_get_next_hop,
    netdev_linux_arp_lookup,

    netdev_linux_update_flags,

    netdev_linux_poll_add,
    netdev_linux_poll_remove,
};
\f
/* HTB traffic control class. */

#define HTB_N_QUEUES 0xf000

struct htb {
    struct tc tc;
    unsigned int max_rate;      /* In bytes/s. */
};

struct htb_class {
    unsigned int min_rate;      /* In bytes/s. */
    unsigned int max_rate;      /* In bytes/s. */
    unsigned int burst;         /* In bytes. */
    unsigned int priority;      /* Lower values are higher priorities. */
};

static struct htb *
htb_get__(const struct netdev *netdev)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    return CONTAINER_OF(netdev_dev->tc, struct htb, tc);
}

static struct htb *
htb_install__(struct netdev *netdev, uint64_t max_rate)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    struct htb *htb;

    htb = xmalloc(sizeof *htb);
    tc_init(&htb->tc, &tc_ops_htb);
    htb->max_rate = max_rate;

    netdev_dev->tc = &htb->tc;

    return htb;
}

/* Create an HTB qdisc.
 *
 * Equivalent to "tc qdisc add dev <dev> root handle 1: htb default
 * 0". */
static int
htb_setup_qdisc__(struct netdev *netdev)
{
    size_t opt_offset;
    struct tc_htb_glob opt;
    struct ofpbuf request;
    struct tcmsg *tcmsg;

    tc_del_qdisc(netdev);

    tcmsg = tc_make_request(netdev, RTM_NEWQDISC,
                            NLM_F_EXCL | NLM_F_CREATE, &request);
    tcmsg->tcm_handle = tc_make_handle(1, 0);
    tcmsg->tcm_parent = TC_H_ROOT;

    nl_msg_put_string(&request, TCA_KIND, "htb");

    memset(&opt, 0, sizeof opt);
    opt.rate2quantum = 10;
    opt.version = 3;
    opt.defcls = 0;

    opt_offset = nl_msg_start_nested(&request, TCA_OPTIONS);
    nl_msg_put_unspec(&request, TCA_HTB_INIT, &opt, sizeof opt);
    nl_msg_end_nested(&request, opt_offset);

    return tc_transact(&request, NULL);
}

/* Equivalent to "tc class replace <dev> classid <handle> parent <parent> htb
 * rate <min_rate>bps ceil <max_rate>bps burst <burst>b prio <priority>". */
static int
htb_setup_class__(struct netdev *netdev, unsigned int handle,
                  unsigned int parent, struct htb_class *class)
{
    size_t opt_offset;
    struct tc_htb_opt opt;
    struct ofpbuf request;
    struct tcmsg *tcmsg;
    int error;
    int mtu;

    netdev_get_mtu(netdev, &mtu);

    memset(&opt, 0, sizeof opt);
    tc_fill_rate(&opt.rate, class->min_rate, mtu);
    tc_fill_rate(&opt.ceil, class->max_rate, mtu);
    opt.buffer = tc_calc_buffer(opt.rate.rate, mtu, class->burst);
    opt.cbuffer = tc_calc_buffer(opt.ceil.rate, mtu, class->burst);
    opt.prio = class->priority;

    tcmsg = tc_make_request(netdev, RTM_NEWTCLASS, NLM_F_CREATE, &request);
    tcmsg->tcm_handle = handle;
    tcmsg->tcm_parent = parent;

    nl_msg_put_string(&request, TCA_KIND, "htb");
    opt_offset = nl_msg_start_nested(&request, TCA_OPTIONS);
    nl_msg_put_unspec(&request, TCA_HTB_PARMS, &opt, sizeof opt);
    tc_put_rtab(&request, TCA_HTB_RTAB, &opt.rate);
    tc_put_rtab(&request, TCA_HTB_CTAB, &opt.ceil);
    nl_msg_end_nested(&request, opt_offset);

    error = tc_transact(&request, NULL);
    if (error) {
        VLOG_WARN_RL(&rl, "failed to replace %s class %u:%u, parent %u:%u, "
                     "min_rate=%u max_rate=%u burst=%u prio=%u (%s)",
                     netdev_get_name(netdev),
                     tc_get_major(handle), tc_get_minor(handle),
                     tc_get_major(parent), tc_get_minor(parent),
                     class->min_rate, class->max_rate,
                     class->burst, class->priority, strerror(error));
    }
    return error;
}

/* Parses Netlink attributes in 'options' for HTB parameters and stores a
 * description of them into 'details'.  The description complies with the
 * specification given in the vswitch database documentation for linux-htb
 * queue details. */
static int
htb_parse_tca_options__(struct nlattr *nl_options, struct htb_class *class)
{
    static const struct nl_policy tca_htb_policy[] = {
        [TCA_HTB_PARMS] = { .type = NL_A_UNSPEC, .optional = false,
                            .min_len = sizeof(struct tc_htb_opt) },
    };

    struct nlattr *attrs[ARRAY_SIZE(tca_htb_policy)];
    const struct tc_htb_opt *htb;

    if (!nl_parse_nested(nl_options, tca_htb_policy,
                         attrs, ARRAY_SIZE(tca_htb_policy))) {
        VLOG_WARN_RL(&rl, "failed to parse HTB class options");
        return EPROTO;
    }

    htb = nl_attr_get(attrs[TCA_HTB_PARMS]);
    class->min_rate = htb->rate.rate;
    class->max_rate = htb->ceil.rate;
    class->burst = tc_ticks_to_bytes(htb->rate.rate, htb->buffer);
    class->priority = htb->prio;
    return 0;
}

static int
htb_parse_tcmsg__(struct ofpbuf *tcmsg, unsigned int *queue_id,
                  struct htb_class *options,
                  struct netdev_queue_stats *stats)
{
    struct nlattr *nl_options;
    unsigned int handle;
    int error;

    error = tc_parse_class(tcmsg, &handle, &nl_options, stats);
    if (!error && queue_id) {
        unsigned int major = tc_get_major(handle);
        unsigned int minor = tc_get_minor(handle);
        if (major == 1 && minor > 0 && minor <= HTB_N_QUEUES) {
            *queue_id = minor - 1;
        } else {
            error = EPROTO;
        }
    }
    if (!error && options) {
        error = htb_parse_tca_options__(nl_options, options);
    }
    return error;
}

static void
htb_parse_qdisc_details__(struct netdev *netdev,
                          const struct shash *details, struct htb_class *hc)
{
    const char *max_rate_s;

    max_rate_s = shash_find_data(details, "max-rate");
    hc->max_rate = max_rate_s ? strtoull(max_rate_s, NULL, 10) / 8 : 0;
    if (!hc->max_rate) {
        uint32_t current;

        netdev_get_features(netdev, &current, NULL, NULL, NULL);
        hc->max_rate = netdev_features_to_bps(current) / 8;
    }
    hc->min_rate = hc->max_rate;
    hc->burst = 0;
    hc->priority = 0;
}

static int
htb_parse_class_details__(struct netdev *netdev,
                          const struct shash *details, struct htb_class *hc)
{
    const struct htb *htb = htb_get__(netdev);
    const char *min_rate_s = shash_find_data(details, "min-rate");
    const char *max_rate_s = shash_find_data(details, "max-rate");
    const char *burst_s = shash_find_data(details, "burst");
    const char *priority_s = shash_find_data(details, "priority");
    int mtu;

    /* min-rate */
    if (!min_rate_s) {
        /* min-rate is required. */
        return EINVAL;
    }
    hc->min_rate = strtoull(min_rate_s, NULL, 10) / 8;
    hc->min_rate = MAX(hc->min_rate, 0);
    hc->min_rate = MIN(hc->min_rate, htb->max_rate);

    /* max-rate */
    hc->max_rate = (max_rate_s
                    ? strtoull(max_rate_s, NULL, 10) / 8
                    : htb->max_rate);
    hc->max_rate = MAX(hc->max_rate, hc->min_rate);
    hc->max_rate = MIN(hc->max_rate, htb->max_rate);

    /* burst
     *
     * According to hints in the documentation that I've read, it is important
     * that 'burst' be at least as big as the largest frame that might be
     * transmitted.  Also, making 'burst' a bit bigger than necessary is OK,
     * but having it a bit too small is a problem.  Since netdev_get_mtu()
     * doesn't include the Ethernet header, we need to add at least 14 (18?) to
     * the MTU.  We actually add 64, instead of 14, as a guard against
     * additional headers get tacked on somewhere that we're not aware of. */
    netdev_get_mtu(netdev, &mtu);
    hc->burst = burst_s ? strtoull(burst_s, NULL, 10) / 8 : 0;
    hc->burst = MAX(hc->burst, mtu + 64);

    /* priority */
    hc->priority = priority_s ? strtoul(priority_s, NULL, 10) : 0;

    return 0;
}

static int
htb_query_class__(const struct netdev *netdev, unsigned int handle,
                  unsigned int parent, struct htb_class *options,
                  struct netdev_queue_stats *stats)
{
    struct ofpbuf *reply;
    int error;

    error = tc_query_class(netdev, handle, parent, &reply);
    if (!error) {
        error = htb_parse_tcmsg__(reply, NULL, options, stats);
        ofpbuf_delete(reply);
    }
    return error;
}

static int
htb_tc_install(struct netdev *netdev, const struct shash *details)
{
    int error;

    error = htb_setup_qdisc__(netdev);
    if (!error) {
        struct htb_class hc;

        htb_parse_qdisc_details__(netdev, details, &hc);
        error = htb_setup_class__(netdev, tc_make_handle(1, 0xfffe),
                                  tc_make_handle(1, 0), &hc);
        if (!error) {
            htb_install__(netdev, hc.max_rate);
        }
    }
    return error;
}

static void
htb_update_queue__(struct netdev *netdev, unsigned int queue_id,
                   const struct htb_class *hc)
{
    struct htb *htb = htb_get__(netdev);
    struct htb_class *hcp;

    hcp = port_array_get(&htb->tc.queues, queue_id);
    if (!hcp) {
        hcp = xmalloc(sizeof *hcp);
        port_array_set(&htb->tc.queues, queue_id, hcp);
    }
    *hcp = *hc;
}

static int
htb_tc_load(struct netdev *netdev, struct ofpbuf *nlmsg OVS_UNUSED)
{
    struct shash details = SHASH_INITIALIZER(&details);
    struct ofpbuf msg;
    struct nl_dump dump;
    struct htb_class hc;
    struct htb *htb;

    /* Get qdisc options. */
    hc.max_rate = 0;
    htb_query_class__(netdev, tc_make_handle(1, 0xfffe), 0, &hc, NULL);
    htb = htb_install__(netdev, hc.max_rate);

    /* Get queues. */
    start_queue_dump(netdev, &dump);
    shash_init(&details);
    while (nl_dump_next(&dump, &msg)) {
        unsigned int queue_id;

        if (!htb_parse_tcmsg__(&msg, &queue_id, &hc, NULL)) {
            htb_update_queue__(netdev, queue_id, &hc);
        }
    }
    nl_dump_done(&dump);

    return 0;
}

static void
htb_tc_destroy(struct tc *tc)
{
    struct htb *htb = CONTAINER_OF(tc, struct htb, tc);
    unsigned int queue_id;
    struct htb_class *hc;

    PORT_ARRAY_FOR_EACH (hc, &htb->tc.queues, queue_id) {
        free(hc);
    }
    tc_destroy(tc);
    free(htb);
}

static int
htb_qdisc_get(const struct netdev *netdev, struct shash *details)
{
    const struct htb *htb = htb_get__(netdev);
    shash_add(details, "max-rate", xasprintf("%llu", 8ULL * htb->max_rate));
    return 0;
}

static int
htb_qdisc_set(struct netdev *netdev, const struct shash *details)
{
    struct htb_class hc;
    int error;

    htb_parse_qdisc_details__(netdev, details, &hc);
    error = htb_setup_class__(netdev, tc_make_handle(1, 0xfffe),
                              tc_make_handle(1, 0), &hc);
    if (!error) {
        htb_get__(netdev)->max_rate = hc.max_rate;
    }
    return error;
}

static int
htb_class_get(const struct netdev *netdev, unsigned int queue_id,
              struct shash *details)
{
    const struct htb *htb = htb_get__(netdev);
    const struct htb_class *hc;

    hc = port_array_get(&htb->tc.queues, queue_id);
    assert(hc != NULL);

    shash_add(details, "min-rate", xasprintf("%llu", 8ULL * hc->min_rate));
    if (hc->min_rate != hc->max_rate) {
        shash_add(details, "max-rate", xasprintf("%llu", 8ULL * hc->max_rate));
    }
    shash_add(details, "burst", xasprintf("%llu", 8ULL * hc->burst));
    if (hc->priority) {
        shash_add(details, "priority", xasprintf("%u", hc->priority));
    }
    return 0;
}

static int
htb_class_set(struct netdev *netdev, unsigned int queue_id,
              const struct shash *details)
{
    struct htb_class hc;
    int error;

    error = htb_parse_class_details__(netdev, details, &hc);
    if (error) {
        return error;
    }

    error = htb_setup_class__(netdev, tc_make_handle(1, queue_id + 1),
                              tc_make_handle(1, 0xfffe), &hc);
    if (error) {
        return error;
    }

    htb_update_queue__(netdev, queue_id, &hc);
    return 0;
}

static int
htb_class_delete(struct netdev *netdev, unsigned int queue_id)
{
    struct htb *htb = htb_get__(netdev);
    struct htb_class *hc;
    int error;

    hc = port_array_get(&htb->tc.queues, queue_id);
    assert(hc != NULL);

    error = tc_delete_class(netdev, tc_make_handle(1, queue_id + 1));
    if (!error) {
        free(hc);
        port_array_delete(&htb->tc.queues, queue_id);
    }
    return error;
}

static int
htb_class_get_stats(const struct netdev *netdev, unsigned int queue_id,
                    struct netdev_queue_stats *stats)
{
    return htb_query_class__(netdev, tc_make_handle(1, queue_id + 1),
                             tc_make_handle(1, 0xfffe), NULL, stats);
}

static int
htb_class_dump_stats(const struct netdev *netdev OVS_UNUSED,
                     const struct ofpbuf *nlmsg,
                     netdev_dump_queue_stats_cb *cb, void *aux)
{
    struct netdev_queue_stats stats;
    unsigned int handle, major, minor;
    int error;

    error = tc_parse_class(nlmsg, &handle, NULL, &stats);
    if (error) {
        return error;
    }

    major = tc_get_major(handle);
    minor = tc_get_minor(handle);
    if (major == 1 && minor > 0 && minor <= HTB_N_QUEUES) {
        (*cb)(tc_get_minor(handle), &stats, aux);
    }
    return 0;
}

static const struct tc_ops tc_ops_htb = {
    "htb",                      /* linux_name */
    "linux-htb",                /* ovs_name */
    HTB_N_QUEUES,               /* n_queues */
    htb_tc_install,
    htb_tc_load,
    htb_tc_destroy,
    htb_qdisc_get,
    htb_qdisc_set,
    htb_class_get,
    htb_class_set,
    htb_class_delete,
    htb_class_get_stats,
    htb_class_dump_stats
};
\f
/* "linux-default" traffic control class.
 *
 * This class represents the default, unnamed Linux qdisc.  It corresponds to
 * the "" (empty string) QoS type in the OVS database. */

static void
default_install__(struct netdev *netdev)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    static struct tc *tc;

    if (!tc) {
        tc = xmalloc(sizeof *tc);
        tc_init(tc, &tc_ops_default);
    }
    netdev_dev->tc = tc;
}

static int
default_tc_install(struct netdev *netdev,
                   const struct shash *details OVS_UNUSED)
{
    default_install__(netdev);
    return 0;
}

static int
default_tc_load(struct netdev *netdev, struct ofpbuf *nlmsg OVS_UNUSED)
{
    default_install__(netdev);
    return 0;
}

static const struct tc_ops tc_ops_default = {
    NULL,                       /* linux_name */
    "",                         /* ovs_name */
    0,                          /* n_queues */
    default_tc_install,
    default_tc_load,
    NULL,                       /* tc_destroy */
    NULL,                       /* qdisc_get */
    NULL,                       /* qdisc_set */
    NULL,                       /* class_get */
    NULL,                       /* class_set */
    NULL,                       /* class_delete */
    NULL,                       /* class_get_stats */
    NULL                        /* class_dump_stats */
};
\f
/* "linux-other" traffic control class.
 *
 * */

static int
other_tc_load(struct netdev *netdev, struct ofpbuf *nlmsg OVS_UNUSED)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    static struct tc *tc;

    if (!tc) {
        tc = xmalloc(sizeof *tc);
        tc_init(tc, &tc_ops_other);
    }
    netdev_dev->tc = tc;
    return 0;
}

static const struct tc_ops tc_ops_other = {
    NULL,                       /* linux_name */
    "linux-other",              /* ovs_name */
    0,                          /* n_queues */
    NULL,                       /* tc_install */
    other_tc_load,
    NULL,                       /* tc_destroy */
    NULL,                       /* qdisc_get */
    NULL,                       /* qdisc_set */
    NULL,                       /* class_get */
    NULL,                       /* class_set */
    NULL,                       /* class_delete */
    NULL,                       /* class_get_stats */
    NULL                        /* class_dump_stats */
};
\f
/* Traffic control. */

/* Number of kernel "tc" ticks per second. */
static double ticks_per_s;

/* Number of kernel "jiffies" per second.  This is used for the purpose of
 * computing buffer sizes.  Generally kernel qdiscs need to be able to buffer
 * one jiffy's worth of data.
 *
 * There are two possibilities here:
 *
 *    - 'buffer_hz' is the kernel's real timer tick rate, a small number in the
 *      approximate range of 100 to 1024.  That means that we really need to
 *      make sure that the qdisc can buffer that much data.
 *
 *    - 'buffer_hz' is an absurdly large number.  That means that the kernel
 *      has finely granular timers and there's no need to fudge additional room
 *      for buffers.  (There's no extra effort needed to implement that: the
 *      large 'buffer_hz' is used as a divisor, so practically any number will
 *      come out as 0 in the division.  Small integer results in the case of
 *      really high dividends won't have any real effect anyhow.)
 */
static unsigned int buffer_hz;

/* Returns tc handle 'major':'minor'. */
static unsigned int
tc_make_handle(unsigned int major, unsigned int minor)
{
    return TC_H_MAKE(major << 16, minor);
}

/* Returns the major number from 'handle'. */
static unsigned int
tc_get_major(unsigned int handle)
{
    return TC_H_MAJ(handle) >> 16;
}

/* Returns the minor number from 'handle'. */
static unsigned int
tc_get_minor(unsigned int handle)
{
    return TC_H_MIN(handle);
}

static struct tcmsg *
tc_make_request(const struct netdev *netdev, int type, unsigned int flags,
                struct ofpbuf *request)
{
    struct tcmsg *tcmsg;
    int ifindex;
    int error;

    error = get_ifindex(netdev, &ifindex);
    if (error) {
        return NULL;
    }

    ofpbuf_init(request, 512);
    nl_msg_put_nlmsghdr(request, sizeof *tcmsg, type, NLM_F_REQUEST | flags);
    tcmsg = ofpbuf_put_zeros(request, sizeof *tcmsg);
    tcmsg->tcm_family = AF_UNSPEC;
    tcmsg->tcm_ifindex = ifindex;
    /* Caller should fill in tcmsg->tcm_handle. */
    /* Caller should fill in tcmsg->tcm_parent. */

    return tcmsg;
}

static int
tc_transact(struct ofpbuf *request, struct ofpbuf **replyp)
{
    int error = nl_sock_transact(rtnl_sock, request, replyp);
    ofpbuf_uninit(request);
    return error;
}

static void
read_psched(void)
{
    /* The values in psched are not individually very meaningful, but they are
     * important.  The tables below show some values seen in the wild.
     *
     * Some notes:
     *
     *   - "c" has always been a constant 1000000 since at least Linux 2.4.14.
     *     (Before that, there are hints that it was 1000000000.)
     *
     *   - "d" can be unrealistically large, see the comment on 'buffer_hz'
     *     above.
     *
     *                        /proc/net/psched
     *     -----------------------------------
     * [1] 000c8000 000f4240 000f4240 00000064
     * [2] 000003e8 00000400 000f4240 3b9aca00
     * [3] 000003e8 00000400 000f4240 3b9aca00
     * [4] 000003e8 00000400 000f4240 00000064
     * [5] 000003e8 00000040 000f4240 3b9aca00
     * [6] 000003e8 00000040 000f4240 000000f9
     *
     *           a         b          c             d ticks_per_s     buffer_hz
     *     ------- --------- ---------- ------------- ----------- -------------
     * [1] 819,200 1,000,000  1,000,000           100     819,200           100
     * [2]   1,000     1,024  1,000,000 1,000,000,000     976,562 1,000,000,000
     * [3]   1,000     1,024  1,000,000 1,000,000,000     976,562 1,000,000,000
     * [4]   1,000     1,024  1,000,000           100     976,562           100
     * [5]   1,000        64  1,000,000 1,000,000,000  15,625,000 1,000,000,000
     * [6]   1,000        64  1,000,000           249  15,625,000           249
     *
     * [1] 2.6.18-128.1.6.el5.xs5.5.0.505.1024xen from XenServer 5.5.0-24648p
     * [2] 2.6.26-1-686-bigmem from Debian lenny
     * [3] 2.6.26-2-sparc64 from Debian lenny
     * [4] 2.6.27.42-0.1.1.xs5.6.810.44.111163xen from XenServer 5.6.810-31078p
     * [5] 2.6.32.21.22 (approx.) from Ubuntu 10.04 on VMware Fusion
     * [6] 2.6.34 from kernel.org on KVM
     */
    static const char fn[] = "/proc/net/psched";
    unsigned int a, b, c, d;
    FILE *stream;

    ticks_per_s = 1.0;
    buffer_hz = 100;

    stream = fopen(fn, "r");
    if (!stream) {
        VLOG_WARN("%s: open failed: %s", fn, strerror(errno));
        return;
    }

    if (fscanf(stream, "%x %x %x %x", &a, &b, &c, &d) != 4) {
        VLOG_WARN("%s: read failed", fn);
        fclose(stream);
        return;
    }
    VLOG_DBG("%s: psched parameters are: %u %u %u %u", fn, a, b, c, d);
    fclose(stream);

    if (!a || !c) {
        VLOG_WARN("%s: invalid scheduler parameters", fn);
        return;
    }

    ticks_per_s = (double) a * c / b;
    if (c == 1000000) {
        buffer_hz = d;
    } else {
        VLOG_WARN("%s: unexpected psched parameters: %u %u %u %u",
                  fn, a, b, c, d);
    }
    VLOG_DBG("%s: ticks_per_s=%f buffer_hz=%u", fn, ticks_per_s, buffer_hz);
}

/* Returns the number of bytes that can be transmitted in 'ticks' ticks at a
 * rate of 'rate' bytes per second. */
static unsigned int
tc_ticks_to_bytes(unsigned int rate, unsigned int ticks)
{
    if (!buffer_hz) {
        read_psched();
    }
    return (rate * ticks) / ticks_per_s;
}

/* Returns the number of ticks that it would take to transmit 'size' bytes at a
 * rate of 'rate' bytes per second. */
static unsigned int
tc_bytes_to_ticks(unsigned int rate, unsigned int size)
{
    if (!buffer_hz) {
        read_psched();
    }
    return ((unsigned long long int) ticks_per_s * size) / rate;
}

/* Returns the number of bytes that need to be reserved for qdisc buffering at
 * a transmission rate of 'rate' bytes per second. */
static unsigned int
tc_buffer_per_jiffy(unsigned int rate)
{
    if (!buffer_hz) {
        read_psched();
    }
    return rate / buffer_hz;
}

/* Given Netlink 'msg' that describes a qdisc, extracts the name of the qdisc,
 * e.g. "htb", into '*kind' (if it is nonnull).  If 'options' is nonnull,
 * extracts 'msg''s TCA_OPTIONS attributes into '*options' if it is present or
 * stores NULL into it if it is absent.
 *
 * '*kind' and '*options' point into 'msg', so they are owned by whoever owns
 * 'msg'.
 *
 * Returns 0 if successful, otherwise a positive errno value. */
static int
tc_parse_qdisc(const struct ofpbuf *msg, const char **kind,
               struct nlattr **options)
{
    static const struct nl_policy tca_policy[] = {
        [TCA_KIND] = { .type = NL_A_STRING, .optional = false },
        [TCA_OPTIONS] = { .type = NL_A_NESTED, .optional = true },
    };
    struct nlattr *ta[ARRAY_SIZE(tca_policy)];

    if (!nl_policy_parse(msg, NLMSG_HDRLEN + sizeof(struct tcmsg),
                         tca_policy, ta, ARRAY_SIZE(ta))) {
        VLOG_WARN_RL(&rl, "failed to parse qdisc message");
        goto error;
    }

    if (kind) {
        *kind = nl_attr_get_string(ta[TCA_KIND]);
    }

    if (options) {
        *options = ta[TCA_OPTIONS];
    }

    return 0;

error:
    if (kind) {
        *kind = NULL;
    }
    if (options) {
        *options = NULL;
    }
    return EPROTO;
}

/* Given Netlink 'msg' that describes a class, extracts the queue ID (e.g. the
 * minor number of its class ID) into '*queue_id', its TCA_OPTIONS attribute
 * into '*options', and its queue statistics into '*stats'.  Any of the output
 * arguments may be null.
 *
 * Returns 0 if successful, otherwise a positive errno value. */
static int
tc_parse_class(const struct ofpbuf *msg, unsigned int *handlep,
               struct nlattr **options, struct netdev_queue_stats *stats)
{
    static const struct nl_policy tca_policy[] = {
        [TCA_OPTIONS] = { .type = NL_A_NESTED, .optional = false },
        [TCA_STATS2] = { .type = NL_A_NESTED, .optional = false },
    };
    struct nlattr *ta[ARRAY_SIZE(tca_policy)];

    if (!nl_policy_parse(msg, NLMSG_HDRLEN + sizeof(struct tcmsg),
                         tca_policy, ta, ARRAY_SIZE(ta))) {
        VLOG_WARN_RL(&rl, "failed to parse class message");
        goto error;
    }

    if (handlep) {
        struct tcmsg *tc = ofpbuf_at_assert(msg, NLMSG_HDRLEN, sizeof *tc);
        *handlep = tc->tcm_handle;
    }

    if (options) {
        *options = ta[TCA_OPTIONS];
    }

    if (stats) {
        const struct gnet_stats_queue *gsq;
        struct gnet_stats_basic gsb;

        static const struct nl_policy stats_policy[] = {
            [TCA_STATS_BASIC] = { .type = NL_A_UNSPEC, .optional = false,
                                  .min_len = sizeof gsb },
            [TCA_STATS_QUEUE] = { .type = NL_A_UNSPEC, .optional = false,
                                  .min_len = sizeof *gsq },
        };
        struct nlattr *sa[ARRAY_SIZE(stats_policy)];

        if (!nl_parse_nested(ta[TCA_STATS2], stats_policy,
                             sa, ARRAY_SIZE(sa))) {
            VLOG_WARN_RL(&rl, "failed to parse class stats");
            goto error;
        }

        /* Alignment issues screw up the length of struct gnet_stats_basic on
         * some arch/bitsize combinations.  Newer versions of Linux have a
         * struct gnet_stats_basic_packed, but we can't depend on that.  The
         * easiest thing to do is just to make a copy. */
        memset(&gsb, 0, sizeof gsb);
        memcpy(&gsb, nl_attr_get(sa[TCA_STATS_BASIC]),
               MIN(nl_attr_get_size(sa[TCA_STATS_BASIC]), sizeof gsb));
        stats->tx_bytes = gsb.bytes;
        stats->tx_packets = gsb.packets;

        gsq = nl_attr_get(sa[TCA_STATS_QUEUE]);
        stats->tx_errors = gsq->drops;
    }

    return 0;

error:
    if (options) {
        *options = NULL;
    }
    if (stats) {
        memset(stats, 0, sizeof *stats);
    }
    return EPROTO;
}

/* Queries the kernel for class with identifier 'handle' and parent 'parent'
 * on 'netdev'. */
static int
tc_query_class(const struct netdev *netdev,
               unsigned int handle, unsigned int parent,
               struct ofpbuf **replyp)
{
    struct ofpbuf request;
    struct tcmsg *tcmsg;
    int error;

    tcmsg = tc_make_request(netdev, RTM_GETTCLASS, NLM_F_ECHO, &request);
    tcmsg->tcm_handle = handle;
    tcmsg->tcm_parent = parent;

    error = tc_transact(&request, replyp);
    if (error) {
        VLOG_WARN_RL(&rl, "query %s class %u:%u (parent %u:%u) failed (%s)",
                     netdev_get_name(netdev),
                     tc_get_major(handle), tc_get_minor(handle),
                     tc_get_major(parent), tc_get_minor(parent),
                     strerror(error));
    }
    return error;
}

/* Equivalent to "tc class del dev <name> handle <handle>". */
static int
tc_delete_class(const struct netdev *netdev, unsigned int handle)
{
    struct ofpbuf request;
    struct tcmsg *tcmsg;
    int error;

    tcmsg = tc_make_request(netdev, RTM_DELTCLASS, 0, &request);
    tcmsg->tcm_handle = handle;
    tcmsg->tcm_parent = 0;

    error = tc_transact(&request, NULL);
    if (error) {
        VLOG_WARN_RL(&rl, "delete %s class %u:%u failed (%s)",
                     netdev_get_name(netdev),
                     tc_get_major(handle), tc_get_minor(handle),
                     strerror(error));
    }
    return error;
}

/* Equivalent to "tc qdisc del dev <name> root". */
static int
tc_del_qdisc(struct netdev *netdev)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    struct ofpbuf request;
    struct tcmsg *tcmsg;
    int error;

    tcmsg = tc_make_request(netdev, RTM_DELQDISC, 0, &request);
    tcmsg->tcm_handle = tc_make_handle(1, 0);
    tcmsg->tcm_parent = TC_H_ROOT;

    error = tc_transact(&request, NULL);
    if (error == EINVAL) {
        /* EINVAL probably means that the default qdisc was in use, in which
         * case we've accomplished our purpose. */
        error = 0;
    }
    if (!error && netdev_dev->tc) {
        if (netdev_dev->tc->ops->tc_destroy) {
            netdev_dev->tc->ops->tc_destroy(netdev_dev->tc);
        }
        netdev_dev->tc = NULL;
    }
    return error;
}

/* If 'netdev''s qdisc type and parameters are not yet known, queries the
 * kernel to determine what they are.  Returns 0 if successful, otherwise a
 * positive errno value. */
static int
tc_query_qdisc(const struct netdev *netdev)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev));
    struct ofpbuf request, *qdisc;
    const struct tc_ops *ops;
    struct tcmsg *tcmsg;
    int load_error;
    int error;

    if (netdev_dev->tc) {
        return 0;
    }

    /* This RTM_GETQDISC is crafted to avoid OOPSing kernels that do not have
     * commit 53b0f08 "net_sched: Fix qdisc_notify()", which is anything before
     * 2.6.35 without that fix backported to it.
     *
     * To avoid the OOPS, we must not make a request that would attempt to dump
     * a "built-in" qdisc, that is, the default pfifo_fast qdisc or one of a
     * few others.  There are a few ways that I can see to do this, but most of
     * them seem to be racy (and if you lose the race the kernel OOPSes).  The
     * technique chosen here is to assume that any non-default qdisc that we
     * create will have a class with handle 1:0.  The built-in qdiscs only have
     * a class with handle 0:0.
     *
     * We could check for Linux 2.6.35+ and use a more straightforward method
     * there. */
    tcmsg = tc_make_request(netdev, RTM_GETQDISC, NLM_F_ECHO, &request);
    tcmsg->tcm_handle = tc_make_handle(1, 0);
    tcmsg->tcm_parent = 0;

    /* Figure out what tc class to instantiate. */
    error = tc_transact(&request, &qdisc);
    if (!error) {
        const char *kind;

        error = tc_parse_qdisc(qdisc, &kind, NULL);
        if (error) {
            ops = &tc_ops_other;
        } else {
            ops = tc_lookup_linux_name(kind);
            if (!ops) {
                static struct vlog_rate_limit rl2 = VLOG_RATE_LIMIT_INIT(1, 1);
                VLOG_INFO_RL(&rl2, "unknown qdisc \"%s\"", kind);

                ops = &tc_ops_other;
            }
        }
    } else if (error == ENOENT) {
        /* Either it's a built-in qdisc, or it's a qdisc set up by some
         * other entity that doesn't have a handle 1:0.  We will assume
         * that it's the system default qdisc. */
        ops = &tc_ops_default;
        error = 0;
    } else {
        /* Who knows?  Maybe the device got deleted. */
        VLOG_WARN_RL(&rl, "query %s qdisc failed (%s)",
                     netdev_get_name(netdev), strerror(error));
        ops = &tc_ops_other;
    }

    /* Instantiate it. */
    load_error = ops->tc_load((struct netdev *) netdev, qdisc);
    assert((load_error == 0) == (netdev_dev->tc != NULL));
    ofpbuf_delete(qdisc);

    return error ? error : load_error;
}

/* Linux traffic control uses tables with 256 entries ("rtab" tables) to
   approximate the time to transmit packets of various lengths.  For an MTU of
   256 or less, each entry is exact; for an MTU of 257 through 512, each entry
   represents two possible packet lengths; for a MTU of 513 through 1024, four
   possible lengths; and so on.

   Returns, for the specified 'mtu', the number of bits that packet lengths
   need to be shifted right to fit within such a 256-entry table. */
static int
tc_calc_cell_log(unsigned int mtu)
{
    int cell_log;

    if (!mtu) {
        mtu = ETH_PAYLOAD_MAX;
    }
    mtu += ETH_HEADER_LEN + VLAN_HEADER_LEN;

    for (cell_log = 0; mtu >= 256; cell_log++) {
        mtu >>= 1;
    }

    return cell_log;
}

/* Initializes 'rate' properly for a rate of 'Bps' bytes per second with an MTU
 * of 'mtu'. */
static void
tc_fill_rate(struct tc_ratespec *rate, uint64_t Bps, int mtu)
{
    memset(rate, 0, sizeof *rate);
    rate->cell_log = tc_calc_cell_log(mtu);
    /* rate->overhead = 0; */           /* New in 2.6.24, not yet in some */
    /* rate->cell_align = 0; */         /* distro headers. */
    rate->mpu = ETH_TOTAL_MIN;
    rate->rate = Bps;
}

/* Appends to 'msg' an "rtab" table for the specified 'rate' as a Netlink
 * attribute of the specified "type".
 *
 * See tc_calc_cell_log() above for a description of "rtab"s. */
static void
tc_put_rtab(struct ofpbuf *msg, uint16_t type, const struct tc_ratespec *rate)
{
    uint32_t *rtab;
    unsigned int i;

    rtab = nl_msg_put_unspec_uninit(msg, type, TC_RTAB_SIZE);
    for (i = 0; i < TC_RTAB_SIZE / sizeof *rtab; i++) {
        unsigned packet_size = (i + 1) << rate->cell_log;
        if (packet_size < rate->mpu) {
            packet_size = rate->mpu;
        }
        rtab[i] = tc_bytes_to_ticks(rate->rate, packet_size);
    }
}

/* Calculates the proper value of 'buffer' or 'cbuffer' in HTB options given a
 * rate of 'Bps' bytes per second, the specified 'mtu', and a user-requested
 * burst size of 'burst_bytes'.  (If no value was requested, a 'burst_bytes' of
 * 0 is fine.)
 *
 * This */
static int
tc_calc_buffer(unsigned int Bps, int mtu, uint64_t burst_bytes)
{
    unsigned int min_burst = tc_buffer_per_jiffy(Bps) + mtu;
    return tc_bytes_to_ticks(Bps, MAX(burst_bytes, min_burst));
}

\f
/* Utility functions. */

static int
get_stats_via_netlink(int ifindex, struct netdev_stats *stats)
{
    /* Policy for RTNLGRP_LINK messages.
     *
     * There are *many* more fields in these messages, but currently we only
     * care about these fields. */
    static const struct nl_policy rtnlgrp_link_policy[] = {
        [IFLA_IFNAME] = { .type = NL_A_STRING, .optional = false },
        [IFLA_STATS] = { .type = NL_A_UNSPEC, .optional = true,
                         .min_len = sizeof(struct rtnl_link_stats) },
    };

    struct ofpbuf request;
    struct ofpbuf *reply;
    struct ifinfomsg *ifi;
    const struct rtnl_link_stats *rtnl_stats;
    struct nlattr *attrs[ARRAY_SIZE(rtnlgrp_link_policy)];
    int error;

    ofpbuf_init(&request, 0);
    nl_msg_put_nlmsghdr(&request, sizeof *ifi, RTM_GETLINK, NLM_F_REQUEST);
    ifi = ofpbuf_put_zeros(&request, sizeof *ifi);
    ifi->ifi_family = PF_UNSPEC;
    ifi->ifi_index = ifindex;
    error = nl_sock_transact(rtnl_sock, &request, &reply);
    ofpbuf_uninit(&request);
    if (error) {
        return error;
    }

    if (!nl_policy_parse(reply, NLMSG_HDRLEN + sizeof(struct ifinfomsg),
                         rtnlgrp_link_policy,
                         attrs, ARRAY_SIZE(rtnlgrp_link_policy))) {
        ofpbuf_delete(reply);
        return EPROTO;
    }

    if (!attrs[IFLA_STATS]) {
        VLOG_WARN_RL(&rl, "RTM_GETLINK reply lacks stats");
        ofpbuf_delete(reply);
        return EPROTO;
    }

    rtnl_stats = nl_attr_get(attrs[IFLA_STATS]);
    stats->rx_packets = rtnl_stats->rx_packets;
    stats->tx_packets = rtnl_stats->tx_packets;
    stats->rx_bytes = rtnl_stats->rx_bytes;
    stats->tx_bytes = rtnl_stats->tx_bytes;
    stats->rx_errors = rtnl_stats->rx_errors;
    stats->tx_errors = rtnl_stats->tx_errors;
    stats->rx_dropped = rtnl_stats->rx_dropped;
    stats->tx_dropped = rtnl_stats->tx_dropped;
    stats->multicast = rtnl_stats->multicast;
    stats->collisions = rtnl_stats->collisions;
    stats->rx_length_errors = rtnl_stats->rx_length_errors;
    stats->rx_over_errors = rtnl_stats->rx_over_errors;
    stats->rx_crc_errors = rtnl_stats->rx_crc_errors;
    stats->rx_frame_errors = rtnl_stats->rx_frame_errors;
    stats->rx_fifo_errors = rtnl_stats->rx_fifo_errors;
    stats->rx_missed_errors = rtnl_stats->rx_missed_errors;
    stats->tx_aborted_errors = rtnl_stats->tx_aborted_errors;
    stats->tx_carrier_errors = rtnl_stats->tx_carrier_errors;
    stats->tx_fifo_errors = rtnl_stats->tx_fifo_errors;
    stats->tx_heartbeat_errors = rtnl_stats->tx_heartbeat_errors;
    stats->tx_window_errors = rtnl_stats->tx_window_errors;

    ofpbuf_delete(reply);

    return 0;
}

static int
get_stats_via_proc(const char *netdev_name, struct netdev_stats *stats)
{
    static const char fn[] = "/proc/net/dev";
    char line[1024];
    FILE *stream;
    int ln;

    stream = fopen(fn, "r");
    if (!stream) {
        VLOG_WARN_RL(&rl, "%s: open failed: %s", fn, strerror(errno));
        return errno;
    }

    ln = 0;
    while (fgets(line, sizeof line, stream)) {
        if (++ln >= 3) {
            char devname[16];
#define X64 "%"SCNu64
            if (sscanf(line,
                       " %15[^:]:"
                       X64 X64 X64 X64 X64 X64 X64 "%*u"
                       X64 X64 X64 X64 X64 X64 X64 "%*u",
                       devname,
                       &stats->rx_bytes,
                       &stats->rx_packets,
                       &stats->rx_errors,
                       &stats->rx_dropped,
                       &stats->rx_fifo_errors,
                       &stats->rx_frame_errors,
                       &stats->multicast,
                       &stats->tx_bytes,
                       &stats->tx_packets,
                       &stats->tx_errors,
                       &stats->tx_dropped,
                       &stats->tx_fifo_errors,
                       &stats->collisions,
                       &stats->tx_carrier_errors) != 15) {
                VLOG_WARN_RL(&rl, "%s:%d: parse error", fn, ln);
            } else if (!strcmp(devname, netdev_name)) {
                stats->rx_length_errors = UINT64_MAX;
                stats->rx_over_errors = UINT64_MAX;
                stats->rx_crc_errors = UINT64_MAX;
                stats->rx_missed_errors = UINT64_MAX;
                stats->tx_aborted_errors = UINT64_MAX;
                stats->tx_heartbeat_errors = UINT64_MAX;
                stats->tx_window_errors = UINT64_MAX;
                fclose(stream);
                return 0;
            }
        }
    }
    VLOG_WARN_RL(&rl, "%s: no stats for %s", fn, netdev_name);
    fclose(stream);
    return ENODEV;
}

static int
get_flags(const struct netdev *netdev, int *flags)
{
    struct ifreq ifr;
    int error;

    error = netdev_linux_do_ioctl(netdev_get_name(netdev), &ifr, SIOCGIFFLAGS,
                                  "SIOCGIFFLAGS");
    *flags = ifr.ifr_flags;
    return error;
}

static int
set_flags(struct netdev *netdev, int flags)
{
    struct ifreq ifr;

    ifr.ifr_flags = flags;
    return netdev_linux_do_ioctl(netdev_get_name(netdev), &ifr, SIOCSIFFLAGS,
                                 "SIOCSIFFLAGS");
}

static int
do_get_ifindex(const char *netdev_name)
{
    struct ifreq ifr;

    strncpy(ifr.ifr_name, netdev_name, sizeof ifr.ifr_name);
    COVERAGE_INC(netdev_get_ifindex);
    if (ioctl(af_inet_sock, SIOCGIFINDEX, &ifr) < 0) {
        VLOG_WARN_RL(&rl, "ioctl(SIOCGIFINDEX) on %s device failed: %s",
                     netdev_name, strerror(errno));
        return -errno;
    }
    return ifr.ifr_ifindex;
}

static int
get_ifindex(const struct netdev *netdev_, int *ifindexp)
{
    struct netdev_dev_linux *netdev_dev =
                                netdev_dev_linux_cast(netdev_get_dev(netdev_));
    *ifindexp = 0;
    if (!(netdev_dev->cache_valid & VALID_IFINDEX)) {
        int ifindex = do_get_ifindex(netdev_get_name(netdev_));
        if (ifindex < 0) {
            return -ifindex;
        }
        netdev_dev->cache_valid |= VALID_IFINDEX;
        netdev_dev->ifindex = ifindex;
    }
    *ifindexp = netdev_dev->ifindex;
    return 0;
}

static int
get_etheraddr(const char *netdev_name, uint8_t ea[ETH_ADDR_LEN])
{
    struct ifreq ifr;
    int hwaddr_family;

    memset(&ifr, 0, sizeof ifr);
    strncpy(ifr.ifr_name, netdev_name, sizeof ifr.ifr_name);
    COVERAGE_INC(netdev_get_hwaddr);
    if (ioctl(af_inet_sock, SIOCGIFHWADDR, &ifr) < 0) {
        VLOG_ERR("ioctl(SIOCGIFHWADDR) on %s device failed: %s",
                 netdev_name, strerror(errno));
        return errno;
    }
    hwaddr_family = ifr.ifr_hwaddr.sa_family;
    if (hwaddr_family != AF_UNSPEC && hwaddr_family != ARPHRD_ETHER) {
        VLOG_WARN("%s device has unknown hardware address family %d",
                  netdev_name, hwaddr_family);
    }
    memcpy(ea, ifr.ifr_hwaddr.sa_data, ETH_ADDR_LEN);
    return 0;
}

static int
set_etheraddr(const char *netdev_name, int hwaddr_family,
              const uint8_t mac[ETH_ADDR_LEN])
{
    struct ifreq ifr;

    memset(&ifr, 0, sizeof ifr);
    strncpy(ifr.ifr_name, netdev_name, sizeof ifr.ifr_name);
    ifr.ifr_hwaddr.sa_family = hwaddr_family;
    memcpy(ifr.ifr_hwaddr.sa_data, mac, ETH_ADDR_LEN);
    COVERAGE_INC(netdev_set_hwaddr);
    if (ioctl(af_inet_sock, SIOCSIFHWADDR, &ifr) < 0) {
        VLOG_ERR("ioctl(SIOCSIFHWADDR) on %s device failed: %s",
                 netdev_name, strerror(errno));
        return errno;
    }
    return 0;
}

static int
netdev_linux_do_ethtool(const char *name, struct ethtool_cmd *ecmd,
                        int cmd, const char *cmd_name)
{
    struct ifreq ifr;

    memset(&ifr, 0, sizeof ifr);
    strncpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
    ifr.ifr_data = (caddr_t) ecmd;

    ecmd->cmd = cmd;
    COVERAGE_INC(netdev_ethtool);
    if (ioctl(af_inet_sock, SIOCETHTOOL, &ifr) == 0) {
        return 0;
    } else {
        if (errno != EOPNOTSUPP) {
            VLOG_WARN_RL(&rl, "ethtool command %s on network device %s "
                         "failed: %s", cmd_name, name, strerror(errno));
        } else {
            /* The device doesn't support this operation.  That's pretty
             * common, so there's no point in logging anything. */
        }
        return errno;
    }
}

static int
netdev_linux_do_ioctl(const char *name, struct ifreq *ifr, int cmd,
                      const char *cmd_name)
{
    strncpy(ifr->ifr_name, name, sizeof ifr->ifr_name);
    if (ioctl(af_inet_sock, cmd, ifr) == -1) {
        VLOG_DBG_RL(&rl, "%s: ioctl(%s) failed: %s", name, cmd_name,
                     strerror(errno));
        return errno;
    }
    return 0;
}

static int
netdev_linux_get_ipv4(const struct netdev *netdev, struct in_addr *ip,
                      int cmd, const char *cmd_name)
{
    struct ifreq ifr;
    int error;

    ifr.ifr_addr.sa_family = AF_INET;
    error = netdev_linux_do_ioctl(netdev_get_name(netdev), &ifr, cmd, cmd_name);
    if (!error) {
        const struct sockaddr_in *sin = (struct sockaddr_in *) &ifr.ifr_addr;
        *ip = sin->sin_addr;
    }
    return error;
}