af_packet.c

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/*
 * INET     An implementation of the TCP/IP protocol suite for the LINUX
 *      operating system.  INET is implemented using the  BSD Socket
 *      interface as the means of communication with the user level.
 *
 *      PACKET - implements raw packet sockets.
 *
 * Authors: Ross Biro
 *      Fred N. van Kempen, <[email protected]>
 *      Alan Cox, <[email protected]>
 *
 * Fixes:
 *      Alan Cox    :   verify_area() now used correctly
 *      Alan Cox    :   new skbuff lists, look ma no backlogs!
 *      Alan Cox    :   tidied skbuff lists.
 *      Alan Cox    :   Now uses generic datagram routines I
 *                  added. Also fixed the peek/read crash
 *                  from all old Linux datagram code.
 *      Alan Cox    :   Uses the improved datagram code.
 *      Alan Cox    :   Added NULL's for socket options.
 *      Alan Cox    :   Re-commented the code.
 *      Alan Cox    :   Use new kernel side addressing
 *      Rob Janssen :   Correct MTU usage.
 *      Dave Platt  :   Counter leaks caused by incorrect
 *                  interrupt locking and some slightly
 *                  dubious gcc output. Can you read
 *                  compiler: it said _VOLATILE_
 *  Richard Kooijman    :   Timestamp fixes.
 *      Alan Cox    :   New buffers. Use sk->mac.raw.
 *      Alan Cox    :   sendmsg/recvmsg support.
 *      Alan Cox    :   Protocol setting support
 *  Alexey Kuznetsov    :   Untied from IPv4 stack.
 *  Cyrus Durgin        :   Fixed kerneld for kmod.
 *  Michal Ostrowski        :       Module initialization cleanup.
 *         Ulises Alonso        :       Frame number limit removal and
 *                                      packet_set_ring memory leak.
 *      Eric Biederman  :   Allow for > 8 byte hardware addresses.
 *                  The convention is that longer addresses
 *                  will simply extend the hardware address
 *                  byte arrays at the end of sockaddr_ll
 *                  and packet_mreq.
 *      Johann Baudy    :   Added TX RING.
 *      Chetan Loke :   Implemented TPACKET_V3 block abstraction
 *                  layer.
 *                  Copyright (C) 2011, <[email protected]>
 *
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 */

#include <linux/types.h>
#include <linux/mm.h>
#include <linux/capability.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_packet.h>
#include <linux/wireless.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <net/net_namespace.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <asm/uaccess.h>
#include <asm/ioctls.h>
#include <asm/page.h>
#include <asm/cacheflush.h>
#include <asm/io.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/poll.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/if_vlan.h>
#include <linux/virtio_net.h>
#include <linux/errqueue.h>
#include <linux/net_tstamp.h>

#ifdef CONFIG_INET
#include <net/inet_common.h>
#endif

#include "internal.h"

/*
   Assumptions:
   - if device has no dev->hard_header routine, it adds and removes ll header
     inside itself. In this case ll header is invisible outside of device,
     but higher levels still should reserve dev->hard_header_len.
     Some devices are enough clever to reallocate skb, when header
     will not fit to reserved space (tunnel), another ones are silly
     (PPP).
   - packet socket receives packets with pulled ll header,
     so that SOCK_RAW should push it back.

On receive:
-----------

Incoming, dev->hard_header!=NULL
   mac_header -> ll header
   data       -> data

Outgoing, dev->hard_header!=NULL
   mac_header -> ll header
   data       -> ll header

Incoming, dev->hard_header==NULL
   mac_header -> UNKNOWN position. It is very likely, that it points to ll
         header.  PPP makes it, that is wrong, because introduce
         assymetry between rx and tx paths.
   data       -> data

Outgoing, dev->hard_header==NULL
   mac_header -> data. ll header is still not built!
   data       -> data

Resume
  If dev->hard_header==NULL we are unlikely to restore sensible ll header.


On transmit:
------------

dev->hard_header != NULL
   mac_header -> ll header
   data       -> ll header

dev->hard_header == NULL (ll header is added by device, we cannot control it)
   mac_header -> data
   data       -> data

   We should set nh.raw on output to correct posistion,
   packet classifier depends on it.
 */

/* Private packet socket structures. */

/* identical to struct packet_mreq except it has
 * a longer address field.
 */
struct packet_mreq_max {
    int     mr_ifindex;
    unsigned short  mr_type;
    unsigned short  mr_alen;
    unsigned char   mr_address[MAX_ADDR_LEN];
};

static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
        int closing, int tx_ring);


#define V3_ALIGNMENT    (8)

#define BLK_HDR_LEN (ALIGN(sizeof(struct tpacket_block_desc), V3_ALIGNMENT))

#define BLK_PLUS_PRIV(sz_of_priv) \
    (BLK_HDR_LEN + ALIGN((sz_of_priv), V3_ALIGNMENT))

#define PGV_FROM_VMALLOC 1

#define BLOCK_STATUS(x) ((x)->hdr.bh1.block_status)
#define BLOCK_NUM_PKTS(x)   ((x)->hdr.bh1.num_pkts)
#define BLOCK_O2FP(x)       ((x)->hdr.bh1.offset_to_first_pkt)
#define BLOCK_LEN(x)        ((x)->hdr.bh1.blk_len)
#define BLOCK_SNUM(x)       ((x)->hdr.bh1.seq_num)
#define BLOCK_O2PRIV(x) ((x)->offset_to_priv)
#define BLOCK_PRIV(x)       ((void *)((char *)(x) + BLOCK_O2PRIV(x)))

struct packet_sock;
static int tpacket_snd(struct packet_sock *po, struct msghdr *msg);

static void *packet_previous_frame(struct packet_sock *po,
        struct packet_ring_buffer *rb,
        int status);
static void packet_increment_head(struct packet_ring_buffer *buff);
static int prb_curr_blk_in_use(struct tpacket_kbdq_core *,
            struct tpacket_block_desc *);
static void *prb_dispatch_next_block(struct tpacket_kbdq_core *,
            struct packet_sock *);
static void prb_retire_current_block(struct tpacket_kbdq_core *,
        struct packet_sock *, unsigned int status);
static int prb_queue_frozen(struct tpacket_kbdq_core *);
static void prb_open_block(struct tpacket_kbdq_core *,
        struct tpacket_block_desc *);
static void prb_retire_rx_blk_timer_expired(unsigned long);
static void _prb_refresh_rx_retire_blk_timer(struct tpacket_kbdq_core *);
static void prb_init_blk_timer(struct packet_sock *,
        struct tpacket_kbdq_core *,
        void (*func) (unsigned long));
static void prb_fill_rxhash(struct tpacket_kbdq_core *, struct tpacket3_hdr *);
static void prb_clear_rxhash(struct tpacket_kbdq_core *,
        struct tpacket3_hdr *);
static void prb_fill_vlan_info(struct tpacket_kbdq_core *,
        struct tpacket3_hdr *);
static void packet_flush_mclist(struct sock *sk);

struct packet_skb_cb {
    unsigned int origlen;
    union {
        struct sockaddr_pkt pkt;
        struct sockaddr_ll ll;
    } sa;
};

#define PACKET_SKB_CB(__skb)    ((struct packet_skb_cb *)((__skb)->cb))

#define GET_PBDQC_FROM_RB(x)    ((struct tpacket_kbdq_core *)(&(x)->prb_bdqc))
#define GET_PBLOCK_DESC(x, bid) \
    ((struct tpacket_block_desc *)((x)->pkbdq[(bid)].buffer))
#define GET_CURR_PBLOCK_DESC_FROM_CORE(x)   \
    ((struct tpacket_block_desc *)((x)->pkbdq[(x)->kactive_blk_num].buffer))
#define GET_NEXT_PRB_BLK_NUM(x) \
    (((x)->kactive_blk_num < ((x)->knum_blocks-1)) ? \
    ((x)->kactive_blk_num+1) : 0)

static void __fanout_unlink(struct sock *sk, struct packet_sock *po);
static void __fanout_link(struct sock *sk, struct packet_sock *po);

/* register_prot_hook must be invoked with the po->bind_lock held,
 * or from a context in which asynchronous accesses to the packet
 * socket is not possible (packet_create()).
 */
static void register_prot_hook(struct sock *sk)
{
    struct packet_sock *po = pkt_sk(sk);
    if (!po->running) {
        if (po->fanout)
            __fanout_link(sk, po);
        else
            dev_add_pack(&po->prot_hook);
        sock_hold(sk);
        po->running = 1;
    }
}

/* {,__}unregister_prot_hook() must be invoked with the po->bind_lock
 * held.   If the sync parameter is true, we will temporarily drop
 * the po->bind_lock and do a synchronize_net to make sure no
 * asynchronous packet processing paths still refer to the elements
 * of po->prot_hook.  If the sync parameter is false, it is the
 * callers responsibility to take care of this.
 */
static void __unregister_prot_hook(struct sock *sk, bool sync)
{
    struct packet_sock *po = pkt_sk(sk);

    po->running = 0;
    if (po->fanout)
        __fanout_unlink(sk, po);
    else
        __dev_remove_pack(&po->prot_hook);
    __sock_put(sk);

    if (sync) {
        spin_unlock(&po->bind_lock);
        synchronize_net();
        spin_lock(&po->bind_lock);
    }
}

static void unregister_prot_hook(struct sock *sk, bool sync)
{
    struct packet_sock *po = pkt_sk(sk);

    if (po->running)
        __unregister_prot_hook(sk, sync);
}

static inline __pure struct page *pgv_to_page(void *addr)
{
    if (is_vmalloc_addr(addr))
        return vmalloc_to_page(addr);
    return virt_to_page(addr);
}

static void __packet_set_status(struct packet_sock *po, void *frame, int status)
{
    union {
        struct tpacket_hdr *h1;
        struct tpacket2_hdr *h2;
        void *raw;
    } h;

    h.raw = frame;
    switch (po->tp_version) {
    case TPACKET_V1:
        h.h1->tp_status = status;
        flush_dcache_page(pgv_to_page(&h.h1->tp_status));
        break;
    case TPACKET_V2:
        h.h2->tp_status = status;
        flush_dcache_page(pgv_to_page(&h.h2->tp_status));
        break;
    case TPACKET_V3:
    default:
        WARN(1, "TPACKET version not supported.\n");
        BUG();
    }

    smp_wmb();
}

static int __packet_get_status(struct packet_sock *po, void *frame)
{
    union {
        struct tpacket_hdr *h1;
        struct tpacket2_hdr *h2;
        void *raw;
    } h;

    smp_rmb();

    h.raw = frame;
    switch (po->tp_version) {
    case TPACKET_V1:
        flush_dcache_page(pgv_to_page(&h.h1->tp_status));
        return h.h1->tp_status;
    case TPACKET_V2:
        flush_dcache_page(pgv_to_page(&h.h2->tp_status));
        return h.h2->tp_status;
    case TPACKET_V3:
    default:
        WARN(1, "TPACKET version not supported.\n");
        BUG();
        return 0;
    }
}

static void *packet_lookup_frame(struct packet_sock *po,
        struct packet_ring_buffer *rb,
        unsigned int position,
        int status)
{
    unsigned int pg_vec_pos, frame_offset;
    union {
        struct tpacket_hdr *h1;
        struct tpacket2_hdr *h2;
        void *raw;
    } h;

    pg_vec_pos = position / rb->frames_per_block;
    frame_offset = position % rb->frames_per_block;

    h.raw = rb->pg_vec[pg_vec_pos].buffer +
        (frame_offset * rb->frame_size);

    if (status != __packet_get_status(po, h.raw))
        return NULL;

    return h.raw;
}

static void *packet_current_frame(struct packet_sock *po,
        struct packet_ring_buffer *rb,
        int status)
{
    return packet_lookup_frame(po, rb, rb->head, status);
}

static void prb_del_retire_blk_timer(struct tpacket_kbdq_core *pkc)
{
    del_timer_sync(&pkc->retire_blk_timer);
}

static void prb_shutdown_retire_blk_timer(struct packet_sock *po,
        int tx_ring,
        struct sk_buff_head *rb_queue)
{
    struct tpacket_kbdq_core *pkc;

    pkc = tx_ring ? &po->tx_ring.prb_bdqc : &po->rx_ring.prb_bdqc;

    spin_lock(&rb_queue->lock);
    pkc->delete_blk_timer = 1;
    spin_unlock(&rb_queue->lock);

    prb_del_retire_blk_timer(pkc);
}

static void prb_init_blk_timer(struct packet_sock *po,
        struct tpacket_kbdq_core *pkc,
        void (*func) (unsigned long))
{
    init_timer(&pkc->retire_blk_timer);
    pkc->retire_blk_timer.data = (long)po;
    pkc->retire_blk_timer.function = func;
    pkc->retire_blk_timer.expires = jiffies;
}

static void prb_setup_retire_blk_timer(struct packet_sock *po, int tx_ring)
{
    struct tpacket_kbdq_core *pkc;

    if (tx_ring)
        BUG();

    pkc = tx_ring ? &po->tx_ring.prb_bdqc : &po->rx_ring.prb_bdqc;
    prb_init_blk_timer(po, pkc, prb_retire_rx_blk_timer_expired);
}

static int prb_calc_retire_blk_tmo(struct packet_sock *po,
                int blk_size_in_bytes)
{
    struct net_device *dev;
    unsigned int mbits = 0, msec = 0, div = 0, tmo = 0;
    struct ethtool_cmd ecmd;
    int err;
    u32 speed;

    rtnl_lock();
    dev = __dev_get_by_index(sock_net(&po->sk), po->ifindex);
    if (unlikely(!dev)) {
        rtnl_unlock();
        return DEFAULT_PRB_RETIRE_TOV;
    }
    err = __ethtool_get_settings(dev, &ecmd);
    speed = ethtool_cmd_speed(&ecmd);
    rtnl_unlock();
    if (!err) {
        /*
         * If the link speed is so slow you don't really
         * need to worry about perf anyways
         */
        if (speed < SPEED_1000 || speed == SPEED_UNKNOWN) {
            return DEFAULT_PRB_RETIRE_TOV;
        } else {
            msec = 1;
            div = speed / 1000;
        }
    }

    mbits = (blk_size_in_bytes * 8) / (1024 * 1024);

    if (div)
        mbits /= div;

    tmo = mbits * msec;

    if (div)
        return tmo+1;
    return tmo;
}

static void prb_init_ft_ops(struct tpacket_kbdq_core *p1,
            union tpacket_req_u *req_u)
{
    p1->feature_req_word = req_u->req3.tp_feature_req_word;
}

static void init_prb_bdqc(struct packet_sock *po,
            struct packet_ring_buffer *rb,
            struct pgv *pg_vec,
            union tpacket_req_u *req_u, int tx_ring)
{
    struct tpacket_kbdq_core *p1 = &rb->prb_bdqc;
    struct tpacket_block_desc *pbd;

    memset(p1, 0x0, sizeof(*p1));

    p1->knxt_seq_num = 1;
    p1->pkbdq = pg_vec;
    pbd = (struct tpacket_block_desc *)pg_vec[0].buffer;
    p1->pkblk_start = pg_vec[0].buffer;
    p1->kblk_size = req_u->req3.tp_block_size;
    p1->knum_blocks = req_u->req3.tp_block_nr;
    p1->hdrlen = po->tp_hdrlen;
    p1->version = po->tp_version;
    p1->last_kactive_blk_num = 0;
    po->stats_u.stats3.tp_freeze_q_cnt = 0;
    if (req_u->req3.tp_retire_blk_tov)
        p1->retire_blk_tov = req_u->req3.tp_retire_blk_tov;
    else
        p1->retire_blk_tov = prb_calc_retire_blk_tmo(po,
                        req_u->req3.tp_block_size);
    p1->tov_in_jiffies = msecs_to_jiffies(p1->retire_blk_tov);
    p1->blk_sizeof_priv = req_u->req3.tp_sizeof_priv;

    prb_init_ft_ops(p1, req_u);
    prb_setup_retire_blk_timer(po, tx_ring);
    prb_open_block(p1, pbd);
}

/*  Do NOT update the last_blk_num first.
 *  Assumes sk_buff_head lock is held.
 */
static void _prb_refresh_rx_retire_blk_timer(struct tpacket_kbdq_core *pkc)
{
    mod_timer(&pkc->retire_blk_timer,
            jiffies + pkc->tov_in_jiffies);
    pkc->last_kactive_blk_num = pkc->kactive_blk_num;
}

/*
 * Timer logic:
 * 1) We refresh the timer only when we open a block.
 *    By doing this we don't waste cycles refreshing the timer
 *    on packet-by-packet basis.
 *
 * With a 1MB block-size, on a 1Gbps line, it will take
 * i) ~8 ms to fill a block + ii) memcpy etc.
 * In this cut we are not accounting for the memcpy time.
 *
 * So, if the user sets the 'tmo' to 10ms then the timer
 * will never fire while the block is still getting filled
 * (which is what we want). However, the user could choose
 * to close a block early and that's fine.
 *
 * But when the timer does fire, we check whether or not to refresh it.
 * Since the tmo granularity is in msecs, it is not too expensive
 * to refresh the timer, lets say every '8' msecs.
 * Either the user can set the 'tmo' or we can derive it based on
 * a) line-speed and b) block-size.
 * prb_calc_retire_blk_tmo() calculates the tmo.
 *
 */
static void prb_retire_rx_blk_timer_expired(unsigned long data)
{
    struct packet_sock *po = (struct packet_sock *)data;
    struct tpacket_kbdq_core *pkc = &po->rx_ring.prb_bdqc;
    unsigned int frozen;
    struct tpacket_block_desc *pbd;

    spin_lock(&po->sk.sk_receive_queue.lock);

    frozen = prb_queue_frozen(pkc);
    pbd = GET_CURR_PBLOCK_DESC_FROM_CORE(pkc);

    if (unlikely(pkc->delete_blk_timer))
        goto out;

    /* We only need to plug the race when the block is partially filled.
     * tpacket_rcv:
     *      lock(); increment BLOCK_NUM_PKTS; unlock()
     *      copy_bits() is in progress ...
     *      timer fires on other cpu:
     *      we can't retire the current block because copy_bits
     *      is in progress.
     *
     */
    if (BLOCK_NUM_PKTS(pbd)) {
        while (atomic_read(&pkc->blk_fill_in_prog)) {
            /* Waiting for skb_copy_bits to finish... */
            cpu_relax();
        }
    }

    if (pkc->last_kactive_blk_num == pkc->kactive_blk_num) {
        if (!frozen) {
            prb_retire_current_block(pkc, po, TP_STATUS_BLK_TMO);
            if (!prb_dispatch_next_block(pkc, po))
                goto refresh_timer;
            else
                goto out;
        } else {
            /* Case 1. Queue was frozen because user-space was
             *     lagging behind.
             */
            if (prb_curr_blk_in_use(pkc, pbd)) {
                /*
                 * Ok, user-space is still behind.
                 * So just refresh the timer.
                 */
                goto refresh_timer;
            } else {
                   /* Case 2. queue was frozen,user-space caught up,
                * now the link went idle && the timer fired.
                * We don't have a block to close.So we open this
                * block and restart the timer.
                * opening a block thaws the queue,restarts timer
                * Thawing/timer-refresh is a side effect.
                */
                prb_open_block(pkc, pbd);
                goto out;
            }
        }
    }

refresh_timer:
    _prb_refresh_rx_retire_blk_timer(pkc);

out:
    spin_unlock(&po->sk.sk_receive_queue.lock);
}

static void prb_flush_block(struct tpacket_kbdq_core *pkc1,
        struct tpacket_block_desc *pbd1, __u32 status)
{
    /* Flush everything minus the block header */

#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 1
    u8 *start, *end;

    start = (u8 *)pbd1;

    /* Skip the block header(we know header WILL fit in 4K) */
    start += PAGE_SIZE;

    end = (u8 *)PAGE_ALIGN((unsigned long)pkc1->pkblk_end);
    for (; start < end; start += PAGE_SIZE)
        flush_dcache_page(pgv_to_page(start));

    smp_wmb();
#endif

    /* Now update the block status. */

    BLOCK_STATUS(pbd1) = status;

    /* Flush the block header */

#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 1
    start = (u8 *)pbd1;
    flush_dcache_page(pgv_to_page(start));

    smp_wmb();
#endif
}

/*
 * Side effect:
 *
 * 1) flush the block
 * 2) Increment active_blk_num
 *
 * Note:We DONT refresh the timer on purpose.
 *  Because almost always the next block will be opened.
 */
static void prb_close_block(struct tpacket_kbdq_core *pkc1,
        struct tpacket_block_desc *pbd1,
        struct packet_sock *po, unsigned int stat)
{
    __u32 status = TP_STATUS_USER | stat;

    struct tpacket3_hdr *last_pkt;
    struct tpacket_hdr_v1 *h1 = &pbd1->hdr.bh1;

    if (po->stats.tp_drops)
        status |= TP_STATUS_LOSING;

    last_pkt = (struct tpacket3_hdr *)pkc1->prev;
    last_pkt->tp_next_offset = 0;

    /* Get the ts of the last pkt */
    if (BLOCK_NUM_PKTS(pbd1)) {
        h1->ts_last_pkt.ts_sec = last_pkt->tp_sec;
        h1->ts_last_pkt.ts_nsec = last_pkt->tp_nsec;
    } else {
        /* Ok, we tmo'd - so get the current time */
        struct timespec ts;
        getnstimeofday(&ts);
        h1->ts_last_pkt.ts_sec = ts.tv_sec;
        h1->ts_last_pkt.ts_nsec = ts.tv_nsec;
    }

    smp_wmb();

    /* Flush the block */
    prb_flush_block(pkc1, pbd1, status);

    pkc1->kactive_blk_num = GET_NEXT_PRB_BLK_NUM(pkc1);
}

static void prb_thaw_queue(struct tpacket_kbdq_core *pkc)
{
    pkc->reset_pending_on_curr_blk = 0;
}

/*
 * Side effect of opening a block:
 *
 * 1) prb_queue is thawed.
 * 2) retire_blk_timer is refreshed.
 *
 */
static void prb_open_block(struct tpacket_kbdq_core *pkc1,
    struct tpacket_block_desc *pbd1)
{
    struct timespec ts;
    struct tpacket_hdr_v1 *h1 = &pbd1->hdr.bh1;

    smp_rmb();

    if (likely(TP_STATUS_KERNEL == BLOCK_STATUS(pbd1))) {

        /* We could have just memset this but we will lose the
         * flexibility of making the priv area sticky
         */
        BLOCK_SNUM(pbd1) = pkc1->knxt_seq_num++;
        BLOCK_NUM_PKTS(pbd1) = 0;
        BLOCK_LEN(pbd1) = BLK_PLUS_PRIV(pkc1->blk_sizeof_priv);
        getnstimeofday(&ts);
        h1->ts_first_pkt.ts_sec = ts.tv_sec;
        h1->ts_first_pkt.ts_nsec = ts.tv_nsec;
        pkc1->pkblk_start = (char *)pbd1;
        pkc1->nxt_offset = pkc1->pkblk_start + BLK_PLUS_PRIV(pkc1->blk_sizeof_priv);
        BLOCK_O2FP(pbd1) = (__u32)BLK_PLUS_PRIV(pkc1->blk_sizeof_priv);
        BLOCK_O2PRIV(pbd1) = BLK_HDR_LEN;
        pbd1->version = pkc1->version;
        pkc1->prev = pkc1->nxt_offset;
        pkc1->pkblk_end = pkc1->pkblk_start + pkc1->kblk_size;
        prb_thaw_queue(pkc1);
        _prb_refresh_rx_retire_blk_timer(pkc1);

        smp_wmb();

        return;
    }

    WARN(1, "ERROR block:%p is NOT FREE status:%d kactive_blk_num:%d\n",
        pbd1, BLOCK_STATUS(pbd1), pkc1->kactive_blk_num);
    dump_stack();
    BUG();
}

/*
 * Queue freeze logic:
 * 1) Assume tp_block_nr = 8 blocks.
 * 2) At time 't0', user opens Rx ring.
 * 3) Some time past 't0', kernel starts filling blocks starting from 0 .. 7
 * 4) user-space is either sleeping or processing block '0'.
 * 5) tpacket_rcv is currently filling block '7', since there is no space left,
 *    it will close block-7,loop around and try to fill block '0'.
 *    call-flow:
 *    __packet_lookup_frame_in_block
 *      prb_retire_current_block()
 *      prb_dispatch_next_block()
 *        |->(BLOCK_STATUS == USER) evaluates to true
 *    5.1) Since block-0 is currently in-use, we just freeze the queue.
 * 6) Now there are two cases:
 *    6.1) Link goes idle right after the queue is frozen.
 *         But remember, the last open_block() refreshed the timer.
 *         When this timer expires,it will refresh itself so that we can
 *         re-open block-0 in near future.
 *    6.2) Link is busy and keeps on receiving packets. This is a simple
 *         case and __packet_lookup_frame_in_block will check if block-0
 *         is free and can now be re-used.
 */
static void prb_freeze_queue(struct tpacket_kbdq_core *pkc,
                  struct packet_sock *po)
{
    pkc->reset_pending_on_curr_blk = 1;
    po->stats_u.stats3.tp_freeze_q_cnt++;
}

#define TOTAL_PKT_LEN_INCL_ALIGN(length) (ALIGN((length), V3_ALIGNMENT))

/*
 * If the next block is free then we will dispatch it
 * and return a good offset.
 * Else, we will freeze the queue.
 * So, caller must check the return value.
 */
static void *prb_dispatch_next_block(struct tpacket_kbdq_core *pkc,
        struct packet_sock *po)
{
    struct tpacket_block_desc *pbd;

    smp_rmb();

    /* 1. Get current block num */
    pbd = GET_CURR_PBLOCK_DESC_FROM_CORE(pkc);

    /* 2. If this block is currently in_use then freeze the queue */
    if (TP_STATUS_USER & BLOCK_STATUS(pbd)) {
        prb_freeze_queue(pkc, po);
        return NULL;
    }

    /*
     * 3.
     * open this block and return the offset where the first packet
     * needs to get stored.
     */
    prb_open_block(pkc, pbd);
    return (void *)pkc->nxt_offset;
}

static void prb_retire_current_block(struct tpacket_kbdq_core *pkc,
        struct packet_sock *po, unsigned int status)
{
    struct tpacket_block_desc *pbd = GET_CURR_PBLOCK_DESC_FROM_CORE(pkc);

    /* retire/close the current block */
    if (likely(TP_STATUS_KERNEL == BLOCK_STATUS(pbd))) {
        /*
         * Plug the case where copy_bits() is in progress on
         * cpu-0 and tpacket_rcv() got invoked on cpu-1, didn't
         * have space to copy the pkt in the current block and
         * called prb_retire_current_block()
         *
         * We don't need to worry about the TMO case because
         * the timer-handler already handled this case.
         */
        if (!(status & TP_STATUS_BLK_TMO)) {
            while (atomic_read(&pkc->blk_fill_in_prog)) {
                /* Waiting for skb_copy_bits to finish... */
                cpu_relax();
            }
        }
        prb_close_block(pkc, pbd, po, status);
        return;
    }

    WARN(1, "ERROR-pbd[%d]:%p\n", pkc->kactive_blk_num, pbd);
    dump_stack();
    BUG();
}

static int prb_curr_blk_in_use(struct tpacket_kbdq_core *pkc,
                      struct tpacket_block_desc *pbd)
{
    return TP_STATUS_USER & BLOCK_STATUS(pbd);
}

static int prb_queue_frozen(struct tpacket_kbdq_core *pkc)
{
    return pkc->reset_pending_on_curr_blk;
}

static void prb_clear_blk_fill_status(struct packet_ring_buffer *rb)
{
    struct tpacket_kbdq_core *pkc  = GET_PBDQC_FROM_RB(rb);
    atomic_dec(&pkc->blk_fill_in_prog);
}

static void prb_fill_rxhash(struct tpacket_kbdq_core *pkc,
            struct tpacket3_hdr *ppd)
{
    ppd->hv1.tp_rxhash = skb_get_rxhash(pkc->skb);
}

static void prb_clear_rxhash(struct tpacket_kbdq_core *pkc,
            struct tpacket3_hdr *ppd)
{
    ppd->hv1.tp_rxhash = 0;
}

static void prb_fill_vlan_info(struct tpacket_kbdq_core *pkc,
            struct tpacket3_hdr *ppd)
{
    if (vlan_tx_tag_present(pkc->skb)) {
        ppd->hv1.tp_vlan_tci = vlan_tx_tag_get(pkc->skb);
        ppd->tp_status = TP_STATUS_VLAN_VALID;
    } else {
        ppd->hv1.tp_vlan_tci = 0;
        ppd->tp_status = TP_STATUS_AVAILABLE;
    }
}

static void prb_run_all_ft_ops(struct tpacket_kbdq_core *pkc,
            struct tpacket3_hdr *ppd)
{
    prb_fill_vlan_info(pkc, ppd);

    if (pkc->feature_req_word & TP_FT_REQ_FILL_RXHASH)
        prb_fill_rxhash(pkc, ppd);
    else
        prb_clear_rxhash(pkc, ppd);
}

static void prb_fill_curr_block(char *curr,
                struct tpacket_kbdq_core *pkc,
                struct tpacket_block_desc *pbd,
                unsigned int len)
{
    struct tpacket3_hdr *ppd;

    ppd  = (struct tpacket3_hdr *)curr;
    ppd->tp_next_offset = TOTAL_PKT_LEN_INCL_ALIGN(len);
    pkc->prev = curr;
    pkc->nxt_offset += TOTAL_PKT_LEN_INCL_ALIGN(len);
    BLOCK_LEN(pbd) += TOTAL_PKT_LEN_INCL_ALIGN(len);
    BLOCK_NUM_PKTS(pbd) += 1;
    atomic_inc(&pkc->blk_fill_in_prog);
    prb_run_all_ft_ops(pkc, ppd);
}

/* Assumes caller has the sk->rx_queue.lock */
static void *__packet_lookup_frame_in_block(struct packet_sock *po,
                        struct sk_buff *skb,
                        int status,
                        unsigned int len
                        )
{
    struct tpacket_kbdq_core *pkc;
    struct tpacket_block_desc *pbd;
    char *curr, *end;

    pkc = GET_PBDQC_FROM_RB(&po->rx_ring);
    pbd = GET_CURR_PBLOCK_DESC_FROM_CORE(pkc);

    /* Queue is frozen when user space is lagging behind */
    if (prb_queue_frozen(pkc)) {
        /*
         * Check if that last block which caused the queue to freeze,
         * is still in_use by user-space.
         */
        if (prb_curr_blk_in_use(pkc, pbd)) {
            /* Can't record this packet */
            return NULL;
        } else {
            /*
             * Ok, the block was released by user-space.
             * Now let's open that block.
             * opening a block also thaws the queue.
             * Thawing is a side effect.
             */
            prb_open_block(pkc, pbd);
        }
    }

    smp_mb();
    curr = pkc->nxt_offset;
    pkc->skb = skb;
    end = (char *)pbd + pkc->kblk_size;

    /* first try the current block */
    if (curr+TOTAL_PKT_LEN_INCL_ALIGN(len) < end) {
        prb_fill_curr_block(curr, pkc, pbd, len);
        return (void *)curr;
    }

    /* Ok, close the current block */
    prb_retire_current_block(pkc, po, 0);

    /* Now, try to dispatch the next block */
    curr = (char *)prb_dispatch_next_block(pkc, po);
    if (curr) {
        pbd = GET_CURR_PBLOCK_DESC_FROM_CORE(pkc);
        prb_fill_curr_block(curr, pkc, pbd, len);
        return (void *)curr;
    }

    /*
     * No free blocks are available.user_space hasn't caught up yet.
     * Queue was just frozen and now this packet will get dropped.
     */
    return NULL;
}

static void *packet_current_rx_frame(struct packet_sock *po,
                        struct sk_buff *skb,
                        int status, unsigned int len)
{
    char *curr = NULL;
    switch (po->tp_version) {
    case TPACKET_V1:
    case TPACKET_V2:
        curr = packet_lookup_frame(po, &po->rx_ring,
                    po->rx_ring.head, status);
        return curr;
    case TPACKET_V3:
        return __packet_lookup_frame_in_block(po, skb, status, len);
    default:
        WARN(1, "TPACKET version not supported\n");
        BUG();
        return NULL;
    }
}

static void *prb_lookup_block(struct packet_sock *po,
                     struct packet_ring_buffer *rb,
                     unsigned int previous,
                     int status)
{
    struct tpacket_kbdq_core *pkc  = GET_PBDQC_FROM_RB(rb);
    struct tpacket_block_desc *pbd = GET_PBLOCK_DESC(pkc, previous);

    if (status != BLOCK_STATUS(pbd))
        return NULL;
    return pbd;
}

static int prb_previous_blk_num(struct packet_ring_buffer *rb)
{
    unsigned int prev;
    if (rb->prb_bdqc.kactive_blk_num)
        prev = rb->prb_bdqc.kactive_blk_num-1;
    else
        prev = rb->prb_bdqc.knum_blocks-1;
    return prev;
}

/* Assumes caller has held the rx_queue.lock */
static void *__prb_previous_block(struct packet_sock *po,
                     struct packet_ring_buffer *rb,
                     int status)
{
    unsigned int previous = prb_previous_blk_num(rb);
    return prb_lookup_block(po, rb, previous, status);
}

static void *packet_previous_rx_frame(struct packet_sock *po,
                         struct packet_ring_buffer *rb,
                         int status)
{
    if (po->tp_version <= TPACKET_V2)
        return packet_previous_frame(po, rb, status);

    return __prb_previous_block(po, rb, status);
}

static void packet_increment_rx_head(struct packet_sock *po,
                        struct packet_ring_buffer *rb)
{
    switch (po->tp_version) {
    case TPACKET_V1:
    case TPACKET_V2:
        return packet_increment_head(rb);
    case TPACKET_V3:
    default:
        WARN(1, "TPACKET version not supported.\n");
        BUG();
        return;
    }
}

static void *packet_previous_frame(struct packet_sock *po,
        struct packet_ring_buffer *rb,
        int status)
{
    unsigned int previous = rb->head ? rb->head - 1 : rb->frame_max;
    return packet_lookup_frame(po, rb, previous, status);
}

static void packet_increment_head(struct packet_ring_buffer *buff)
{
    buff->head = buff->head != buff->frame_max ? buff->head+1 : 0;
}

static void packet_sock_destruct(struct sock *sk)
{
    skb_queue_purge(&sk->sk_error_queue);

    WARN_ON(atomic_read(&sk->sk_rmem_alloc));
    WARN_ON(atomic_read(&sk->sk_wmem_alloc));

    if (!sock_flag(sk, SOCK_DEAD)) {
        pr_err("Attempt to release alive packet socket: %p\n", sk);
        return;
    }

    sk_refcnt_debug_dec(sk);
}

static int fanout_rr_next(struct packet_fanout *f, unsigned int num)
{
    int x = atomic_read(&f->rr_cur) + 1;

    if (x >= num)
        x = 0;

    return x;
}

static struct sock *fanout_demux_hash(struct packet_fanout *f, struct sk_buff *skb, unsigned int num)
{
    u32 idx, hash = skb->rxhash;

    idx = ((u64)hash * num) >> 32;

    return f->arr[idx];
}

static struct sock *fanout_demux_lb(struct packet_fanout *f, struct sk_buff *skb, unsigned int num)
{
    int cur, old;

    cur = atomic_read(&f->rr_cur);
    while ((old = atomic_cmpxchg(&f->rr_cur, cur,
                     fanout_rr_next(f, num))) != cur)
        cur = old;
    return f->arr[cur];
}

static struct sock *fanout_demux_cpu(struct packet_fanout *f, struct sk_buff *skb, unsigned int num)
{
    unsigned int cpu = smp_processor_id();

    return f->arr[cpu % num];
}

static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
                 struct packet_type *pt, struct net_device *orig_dev)
{
    struct packet_fanout *f = pt->af_packet_priv;
    unsigned int num = f->num_members;
    struct packet_sock *po;
    struct sock *sk;

    if (!net_eq(dev_net(dev), read_pnet(&f->net)) ||
        !num) {
        kfree_skb(skb);
        return 0;
    }

    switch (f->type) {
    case PACKET_FANOUT_HASH:
    default:
        if (f->defrag) {
            skb = ip_check_defrag(skb, IP_DEFRAG_AF_PACKET);
            if (!skb)
                return 0;
        }
        skb_get_rxhash(skb);
        sk = fanout_demux_hash(f, skb, num);
        break;
    case PACKET_FANOUT_LB:
        sk = fanout_demux_lb(f, skb, num);
        break;
    case PACKET_FANOUT_CPU:
        sk = fanout_demux_cpu(f, skb, num);
        break;
    }

    po = pkt_sk(sk);

    return po->prot_hook.func(skb, dev, &po->prot_hook, orig_dev);
}

DEFINE_MUTEX(fanout_mutex);
EXPORT_SYMBOL_GPL(fanout_mutex);
static LIST_HEAD(fanout_list);

static void __fanout_link(struct sock *sk, struct packet_sock *po)
{
    struct packet_fanout *f = po->fanout;

    spin_lock(&f->lock);
    f->arr[f->num_members] = sk;
    smp_wmb();
    f->num_members++;
    spin_unlock(&f->lock);
}

static void __fanout_unlink(struct sock *sk, struct packet_sock *po)
{
    struct packet_fanout *f = po->fanout;
    int i;

    spin_lock(&f->lock);
    for (i = 0; i < f->num_members; i++) {
        if (f->arr[i] == sk)
            break;
    }
    BUG_ON(i >= f->num_members);
    f->arr[i] = f->arr[f->num_members - 1];
    f->num_members--;
    spin_unlock(&f->lock);
}

static bool match_fanout_group(struct packet_type *ptype, struct sock * sk)
{
    if (ptype->af_packet_priv == (void*)((struct packet_sock *)sk)->fanout)
        return true;

    return false;
}

static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
{
    struct packet_sock *po = pkt_sk(sk);
    struct packet_fanout *f, *match;
    u8 type = type_flags & 0xff;
    u8 defrag = (type_flags & PACKET_FANOUT_FLAG_DEFRAG) ? 1 : 0;
    int err;

    switch (type) {
    case PACKET_FANOUT_HASH:
    case PACKET_FANOUT_LB:
    case PACKET_FANOUT_CPU:
        break;
    default:
        return -EINVAL;
    }

    if (!po->running)
        return -EINVAL;

    if (po->fanout)
        return -EALREADY;

    mutex_lock(&fanout_mutex);
    match = NULL;
    list_for_each_entry(f, &fanout_list, list) {
        if (f->id == id &&
            read_pnet(&f->net) == sock_net(sk)) {
            match = f;
            break;
        }
    }
    err = -EINVAL;
    if (match && match->defrag != defrag)
        goto out;
    if (!match) {
        err = -ENOMEM;
        match = kzalloc(sizeof(*match), GFP_KERNEL);
        if (!match)
            goto out;
        write_pnet(&match->net, sock_net(sk));
        match->id = id;
        match->type = type;
        match->defrag = defrag;
        atomic_set(&match->rr_cur, 0);
        INIT_LIST_HEAD(&match->list);
        spin_lock_init(&match->lock);
        atomic_set(&match->sk_ref, 0);
        match->prot_hook.type = po->prot_hook.type;
        match->prot_hook.dev = po->prot_hook.dev;
        match->prot_hook.func = packet_rcv_fanout;
        match->prot_hook.af_packet_priv = match;
        match->prot_hook.id_match = match_fanout_group;
        dev_add_pack(&match->prot_hook);
        list_add(&match->list, &fanout_list);
    }
    err = -EINVAL;
    if (match->type == type &&
        match->prot_hook.type == po->prot_hook.type &&
        match->prot_hook.dev == po->prot_hook.dev) {
        err = -ENOSPC;
        if (atomic_read(&match->sk_ref) < PACKET_FANOUT_MAX) {
            __dev_remove_pack(&po->prot_hook);
            po->fanout = match;
            atomic_inc(&match->sk_ref);
            __fanout_link(sk, po);
            err = 0;
        }
    }
out:
    mutex_unlock(&fanout_mutex);
    return err;
}

static void fanout_release(struct sock *sk)
{
    struct packet_sock *po = pkt_sk(sk);
    struct packet_fanout *f;

    f = po->fanout;
    if (!f)
        return;

    mutex_lock(&fanout_mutex);
    po->fanout = NULL;

    if (atomic_dec_and_test(&f->sk_ref)) {
        list_del(&f->list);
        dev_remove_pack(&f->prot_hook);
        kfree(f);
    }
    mutex_unlock(&fanout_mutex);
}

static const struct proto_ops packet_ops;

static const struct proto_ops packet_ops_spkt;

static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev,
               struct packet_type *pt, struct net_device *orig_dev)
{
    struct sock *sk;
    struct sockaddr_pkt *spkt;

    /*
     *  When we registered the protocol we saved the socket in the data
     *  field for just this event.
     */

    sk = pt->af_packet_priv;

    /*
     *  Yank back the headers [hope the device set this
     *  right or kerboom...]
     *
     *  Incoming packets have ll header pulled,
     *  push it back.
     *
     *  For outgoing ones skb->data == skb_mac_header(skb)
     *  so that this procedure is noop.
     */

    if (skb->pkt_type == PACKET_LOOPBACK)
        goto out;

    if (!net_eq(dev_net(dev), sock_net(sk)))
        goto out;

    skb = skb_share_check(skb, GFP_ATOMIC);
    if (skb == NULL)
        goto oom;

    /* drop any routing info */
    skb_dst_drop(skb);

    /* drop conntrack reference */
    nf_reset(skb);

    spkt = &PACKET_SKB_CB(skb)->sa.pkt;

    skb_push(skb, skb->data - skb_mac_header(skb));

    /*
     *  The SOCK_PACKET socket receives _all_ frames.
     */

    spkt->spkt_family = dev->type;
    strlcpy(spkt->spkt_device, dev->name, sizeof(spkt->spkt_device));
    spkt->spkt_protocol = skb->protocol;

    /*
     *  Charge the memory to the socket. This is done specifically
     *  to prevent sockets using all the memory up.
     */

    if (sock_queue_rcv_skb(sk, skb) == 0)
        return 0;

out:
    kfree_skb(skb);
oom:
    return 0;
}


/*
 *  Output a raw packet to a device layer. This bypasses all the other
 *  protocol layers and you must therefore supply it with a complete frame
 */

static int packet_sendmsg_spkt(struct kiocb *iocb, struct socket *sock,
                   struct msghdr *msg, size_t len)
{
    struct sock *sk = sock->sk;
    struct sockaddr_pkt *saddr = (struct sockaddr_pkt *)msg->msg_name;
    struct sk_buff *skb = NULL;
    struct net_device *dev;
    __be16 proto = 0;
    int err;
    int extra_len = 0;

    /*
     *  Get and verify the address.
     */

    if (saddr) {
        if (msg->msg_namelen < sizeof(struct sockaddr))
            return -EINVAL;
        if (msg->msg_namelen == sizeof(struct sockaddr_pkt))
            proto = saddr->spkt_protocol;
    } else
        return -ENOTCONN;   /* SOCK_PACKET must be sent giving an address */

    /*
     *  Find the device first to size check it
     */

    saddr->spkt_device[sizeof(saddr->spkt_device) - 1] = 0;
retry:
    rcu_read_lock();
    dev = dev_get_by_name_rcu(sock_net(sk), saddr->spkt_device);
    err = -ENODEV;
    if (dev == NULL)
        goto out_unlock;

    err = -ENETDOWN;
    if (!(dev->flags & IFF_UP))
        goto out_unlock;

    /*
     * You may not queue a frame bigger than the mtu. This is the lowest level
     * raw protocol and you must do your own fragmentation at this level.
     */

    if (unlikely(sock_flag(sk, SOCK_NOFCS))) {
        if (!netif_supports_nofcs(dev)) {
            err = -EPROTONOSUPPORT;
            goto out_unlock;
        }
        extra_len = 4; /* We're doing our own CRC */
    }

    err = -EMSGSIZE;
    if (len > dev->mtu + dev->hard_header_len + VLAN_HLEN + extra_len)
        goto out_unlock;

    if (!skb) {
        size_t reserved = LL_RESERVED_SPACE(dev);
        int tlen = dev->needed_tailroom;
        unsigned int hhlen = dev->header_ops ? dev->hard_header_len : 0;

        rcu_read_unlock();
        skb = sock_wmalloc(sk, len + reserved + tlen, 0, GFP_KERNEL);
        if (skb == NULL)
            return -ENOBUFS;
        /* FIXME: Save some space for broken drivers that write a hard
         * header at transmission time by themselves. PPP is the notable
         * one here. This should really be fixed at the driver level.
         */
        skb_reserve(skb, reserved);
        skb_reset_network_header(skb);

        /* Try to align data part correctly */
        if (hhlen) {
            skb->data -= hhlen;
            skb->tail -= hhlen;
            if (len < hhlen)
                skb_reset_network_header(skb);
        }
        err = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len);
        if (err)
            goto out_free;
        goto retry;
    }

    if (len > (dev->mtu + dev->hard_header_len + extra_len)) {
        /* Earlier code assumed this would be a VLAN pkt,
         * double-check this now that we have the actual
         * packet in hand.
         */
        struct ethhdr *ehdr;
        skb_reset_mac_header(skb);
        ehdr = eth_hdr(skb);
        if (ehdr->h_proto != htons(ETH_P_8021Q)) {
            err = -EMSGSIZE;
            goto out_unlock;
        }
    }

    skb->protocol = proto;
    skb->dev = dev;
    skb->priority = sk->sk_priority;
    skb->mark = sk->sk_mark;
    err = sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);
    if (err < 0)
        goto out_unlock;

    if (unlikely(extra_len == 4))
        skb->no_fcs = 1;

    dev_queue_xmit(skb);
    rcu_read_unlock();
    return len;

out_unlock:
    rcu_read_unlock();
out_free:
    kfree_skb(skb);
    return err;
}

static unsigned int run_filter(const struct sk_buff *skb,
                      const struct sock *sk,
                      unsigned int res)
{
    struct sk_filter *filter;

    rcu_read_lock();
    filter = rcu_dereference(sk->sk_filter);
    if (filter != NULL)
        res = SK_RUN_FILTER(filter, skb);
    rcu_read_unlock();

    return res;
}

/*
 * This function makes lazy skb cloning in hope that most of packets
 * are discarded by BPF.
 *
 * Note tricky part: we DO mangle shared skb! skb->data, skb->len
 * and skb->cb are mangled. It works because (and until) packets
 * falling here are owned by current CPU. Output packets are cloned
 * by dev_queue_xmit_nit(), input packets are processed by net_bh
 * sequencially, so that if we return skb to original state on exit,
 * we will not harm anyone.
 */

static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
              struct packet_type *pt, struct net_device *orig_dev)
{
    struct sock *sk;
    struct sockaddr_ll *sll;
    struct packet_sock *po;
    u8 *skb_head = skb->data;
    int skb_len = skb->len;
    unsigned int snaplen, res;

    if (skb->pkt_type == PACKET_LOOPBACK)
        goto drop;

    sk = pt->af_packet_priv;
    po = pkt_sk(sk);

    if (!net_eq(dev_net(dev), sock_net(sk)))
        goto drop;

    skb->dev = dev;

    if (dev->header_ops) {
        /* The device has an explicit notion of ll header,
         * exported to higher levels.
         *
         * Otherwise, the device hides details of its frame
         * structure, so that corresponding packet head is
         * never delivered to user.
         */
        if (sk->sk_type != SOCK_DGRAM)
            skb_push(skb, skb->data - skb_mac_header(skb));
        else if (skb->pkt_type == PACKET_OUTGOING) {
            /* Special case: outgoing packets have ll header at head */
            skb_pull(skb, skb_network_offset(skb));
        }
    }

    snaplen = skb->len;

    res = run_filter(skb, sk, snaplen);
    if (!res)
        goto drop_n_restore;
    if (snaplen > res)
        snaplen = res;

    if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
        goto drop_n_acct;

    if (skb_shared(skb)) {
        struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
        if (nskb == NULL)
            goto drop_n_acct;

        if (skb_head != skb->data) {
            skb->data = skb_head;
            skb->len = skb_len;
        }
        consume_skb(skb);
        skb = nskb;
    }

    BUILD_BUG_ON(sizeof(*PACKET_SKB_CB(skb)) + MAX_ADDR_LEN - 8 >
             sizeof(skb->cb));

    sll = &PACKET_SKB_CB(skb)->sa.ll;
    sll->sll_family = AF_PACKET;
    sll->sll_hatype = dev->type;
    sll->sll_protocol = skb->protocol;
    sll->sll_pkttype = skb->pkt_type;
    if (unlikely(po->origdev))
        sll->sll_ifindex = orig_dev->ifindex;
    else
        sll->sll_ifindex = dev->ifindex;

    sll->sll_halen = dev_parse_header(skb, sll->sll_addr);

    PACKET_SKB_CB(skb)->origlen = skb->len;

    if (pskb_trim(skb, snaplen))
        goto drop_n_acct;

    skb_set_owner_r(skb, sk);
    skb->dev = NULL;
    skb_dst_drop(skb);

    /* drop conntrack reference */
    nf_reset(skb);

    spin_lock(&sk->sk_receive_queue.lock);
    po->stats.tp_packets++;
    skb->dropcount = atomic_read(&sk->sk_drops);
    __skb_queue_tail(&sk->sk_receive_queue, skb);
    spin_unlock(&sk->sk_receive_queue.lock);
    sk->sk_data_ready(sk, skb->len);
    return 0;

drop_n_acct:
    spin_lock(&sk->sk_receive_queue.lock);
    po->stats.tp_drops++;
    atomic_inc(&sk->sk_drops);
    spin_unlock(&sk->sk_receive_queue.lock);

drop_n_restore:
    if (skb_head != skb->data && skb_shared(skb)) {
        skb->data = skb_head;
        skb->len = skb_len;
    }
drop:
    consume_skb(skb);
    return 0;
}

static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
               struct packet_type *pt, struct net_device *orig_dev)
{
    struct sock *sk;
    struct packet_sock *po;
    struct sockaddr_ll *sll;
    union {
        struct tpacket_hdr *h1;
        struct tpacket2_hdr *h2;
        struct tpacket3_hdr *h3;
        void *raw;
    } h;
    u8 *skb_head = skb->data;
    int skb_len = skb->len;
    unsigned int snaplen, res;
    unsigned long status = TP_STATUS_USER;
    unsigned short macoff, netoff, hdrlen;
    struct sk_buff *copy_skb = NULL;
    struct timeval tv;
    struct timespec ts;
    struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);

    if (skb->pkt_type == PACKET_LOOPBACK)
        goto drop;

    sk = pt->af_packet_priv;
    po = pkt_sk(sk);

    if (!net_eq(dev_net(dev), sock_net(sk)))
        goto drop;

    if (dev->header_ops) {
        if (sk->sk_type != SOCK_DGRAM)
            skb_push(skb, skb->data - skb_mac_header(skb));
        else if (skb->pkt_type == PACKET_OUTGOING) {
            /* Special case: outgoing packets have ll header at head */
            skb_pull(skb, skb_network_offset(skb));
        }
    }

    if (skb->ip_summed == CHECKSUM_PARTIAL)
        status |= TP_STATUS_CSUMNOTREADY;

    snaplen = skb->len;

    res = run_filter(skb, sk, snaplen);
    if (!res)
        goto drop_n_restore;
    if (snaplen > res)
        snaplen = res;

    if (sk->sk_type == SOCK_DGRAM) {
        macoff = netoff = TPACKET_ALIGN(po->tp_hdrlen) + 16 +
                  po->tp_reserve;
    } else {
        unsigned int maclen = skb_network_offset(skb);
        netoff = TPACKET_ALIGN(po->tp_hdrlen +
                       (maclen < 16 ? 16 : maclen)) +
            po->tp_reserve;
        macoff = netoff - maclen;
    }
    if (po->tp_version <= TPACKET_V2) {
        if (macoff + snaplen > po->rx_ring.frame_size) {
            if (po->copy_thresh &&
                atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf) {
                if (skb_shared(skb)) {
                    copy_skb = skb_clone(skb, GFP_ATOMIC);
                } else {
                    copy_skb = skb_get(skb);
                    skb_head = skb->data;
                }
                if (copy_skb)
                    skb_set_owner_r(copy_skb, sk);
            }
            snaplen = po->rx_ring.frame_size - macoff;
            if ((int)snaplen < 0)
                snaplen = 0;
        }
    }
    spin_lock(&sk->sk_receive_queue.lock);
    h.raw = packet_current_rx_frame(po, skb,
                    TP_STATUS_KERNEL, (macoff+snaplen));
    if (!h.raw)
        goto ring_is_full;
    if (po->tp_version <= TPACKET_V2) {
        packet_increment_rx_head(po, &po->rx_ring);
    /*
     * LOSING will be reported till you read the stats,
     * because it's COR - Clear On Read.
     * Anyways, moving it for V1/V2 only as V3 doesn't need this
     * at packet level.
     */
        if (po->stats.tp_drops)
            status |= TP_STATUS_LOSING;
    }
    po->stats.tp_packets++;
    if (copy_skb) {
        status |= TP_STATUS_COPY;
        __skb_queue_tail(&sk->sk_receive_queue, copy_skb);
    }
    spin_unlock(&sk->sk_receive_queue.lock);

    skb_copy_bits(skb, 0, h.raw + macoff, snaplen);

    switch (po->tp_version) {
    case TPACKET_V1:
        h.h1->tp_len = skb->len;
        h.h1->tp_snaplen = snaplen;
        h.h1->tp_mac = macoff;
        h.h1->tp_net = netoff;
        if ((po->tp_tstamp & SOF_TIMESTAMPING_SYS_HARDWARE)
                && shhwtstamps->syststamp.tv64)
            tv = ktime_to_timeval(shhwtstamps->syststamp);
        else if ((po->tp_tstamp & SOF_TIMESTAMPING_RAW_HARDWARE)
                && shhwtstamps->hwtstamp.tv64)
            tv = ktime_to_timeval(shhwtstamps->hwtstamp);
        else if (skb->tstamp.tv64)
            tv = ktime_to_timeval(skb->tstamp);
        else
            do_gettimeofday(&tv);
        h.h1->tp_sec = tv.tv_sec;
        h.h1->tp_usec = tv.tv_usec;
        hdrlen = sizeof(*h.h1);
        break;
    case TPACKET_V2:
        h.h2->tp_len = skb->len;
        h.h2->tp_snaplen = snaplen;
        h.h2->tp_mac = macoff;
        h.h2->tp_net = netoff;
        if ((po->tp_tstamp & SOF_TIMESTAMPING_SYS_HARDWARE)
                && shhwtstamps->syststamp.tv64)
            ts = ktime_to_timespec(shhwtstamps->syststamp);
        else if ((po->tp_tstamp & SOF_TIMESTAMPING_RAW_HARDWARE)
                && shhwtstamps->hwtstamp.tv64)
            ts = ktime_to_timespec(shhwtstamps->hwtstamp);
        else if (skb->tstamp.tv64)
            ts = ktime_to_timespec(skb->tstamp);
        else
            getnstimeofday(&ts);
        h.h2->tp_sec = ts.tv_sec;
        h.h2->tp_nsec = ts.tv_nsec;
        if (vlan_tx_tag_present(skb)) {
            h.h2->tp_vlan_tci = vlan_tx_tag_get(skb);
            status |= TP_STATUS_VLAN_VALID;
        } else {
            h.h2->tp_vlan_tci = 0;
        }
        h.h2->tp_padding = 0;
        hdrlen = sizeof(*h.h2);
        break;
    case TPACKET_V3:
        /* tp_nxt_offset,vlan are already populated above.
         * So DONT clear those fields here
         */
        h.h3->tp_status |= status;
        h.h3->tp_len = skb->len;
        h.h3->tp_snaplen = snaplen;
        h.h3->tp_mac = macoff;
        h.h3->tp_net = netoff;
        if ((po->tp_tstamp & SOF_TIMESTAMPING_SYS_HARDWARE)
                && shhwtstamps->syststamp.tv64)
            ts = ktime_to_timespec(shhwtstamps->syststamp);
        else if ((po->tp_tstamp & SOF_TIMESTAMPING_RAW_HARDWARE)
                && shhwtstamps->hwtstamp.tv64)
            ts = ktime_to_timespec(shhwtstamps->hwtstamp);
        else if (skb->tstamp.tv64)
            ts = ktime_to_timespec(skb->tstamp);
        else
            getnstimeofday(&ts);
        h.h3->tp_sec  = ts.tv_sec;
        h.h3->tp_nsec = ts.tv_nsec;
        hdrlen = sizeof(*h.h3);
        break;
    default:
        BUG();
    }

    sll = h.raw + TPACKET_ALIGN(hdrlen);
    sll->sll_halen = dev_parse_header(skb, sll->sll_addr);
    sll->sll_family = AF_PACKET;
    sll->sll_hatype = dev->type;
    sll->sll_protocol = skb->protocol;
    sll->sll_pkttype = skb->pkt_type;
    if (unlikely(po->origdev))
        sll->sll_ifindex = orig_dev->ifindex;
    else
        sll->sll_ifindex = dev->ifindex;

    smp_mb();
#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 1
    {
        u8 *start, *end;

        if (po->tp_version <= TPACKET_V2) {
            end = (u8 *)PAGE_ALIGN((unsigned long)h.raw
                + macoff + snaplen);
            for (start = h.raw; start < end; start += PAGE_SIZE)
                flush_dcache_page(pgv_to_page(start));
        }
        smp_wmb();
    }
#endif
    if (po->tp_version <= TPACKET_V2)
        __packet_set_status(po, h.raw, status);
    else
        prb_clear_blk_fill_status(&po->rx_ring);

    sk->sk_data_ready(sk, 0);

drop_n_restore:
    if (skb_head != skb->data && skb_shared(skb)) {
        skb->data = skb_head;
        skb->len = skb_len;
    }
drop:
    kfree_skb(skb);
    return 0;

ring_is_full:
    po->stats.tp_drops++;
    spin_unlock(&sk->sk_receive_queue.lock);

    sk->sk_data_ready(sk, 0);
    kfree_skb(copy_skb);
    goto drop_n_restore;
}

static void tpacket_destruct_skb(struct sk_buff *skb)
{
    struct packet_sock *po = pkt_sk(skb->sk);
    void *ph;

    if (likely(po->tx_ring.pg_vec)) {
        ph = skb_shinfo(skb)->destructor_arg;
        BUG_ON(atomic_read(&po->tx_ring.pending) == 0);
        atomic_dec(&po->tx_ring.pending);
        __packet_set_status(po, ph, TP_STATUS_AVAILABLE);
    }

    sock_wfree(skb);
}

static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
        void *frame, struct net_device *dev, int size_max,
        __be16 proto, unsigned char *addr, int hlen)
{
    union {
        struct tpacket_hdr *h1;
        struct tpacket2_hdr *h2;
        void *raw;
    } ph;
    int to_write, offset, len, tp_len, nr_frags, len_max;
    struct socket *sock = po->sk.sk_socket;
    struct page *page;
    void *data;
    int err;

    ph.raw = frame;

    skb->protocol = proto;
    skb->dev = dev;
    skb->priority = po->sk.sk_priority;
    skb->mark = po->sk.sk_mark;
    skb_shinfo(skb)->destructor_arg = ph.raw;

    switch (po->tp_version) {
    case TPACKET_V2:
        tp_len = ph.h2->tp_len;
        break;
    default:
        tp_len = ph.h1->tp_len;
        break;
    }
    if (unlikely(tp_len > size_max)) {
        pr_err("packet size is too long (%d > %d)\n", tp_len, size_max);
        return -EMSGSIZE;
    }

    skb_reserve(skb, hlen);
    skb_reset_network_header(skb);

    data = ph.raw + po->tp_hdrlen - sizeof(struct sockaddr_ll);
    to_write = tp_len;

    if (sock->type == SOCK_DGRAM) {
        err = dev_hard_header(skb, dev, ntohs(proto), addr,
                NULL, tp_len);
        if (unlikely(err < 0))
            return -EINVAL;
    } else if (dev->hard_header_len) {
        /* net device doesn't like empty head */
        if (unlikely(tp_len <= dev->hard_header_len)) {
            pr_err("packet size is too short (%d < %d)\n",
                   tp_len, dev->hard_header_len);
            return -EINVAL;
        }

        skb_push(skb, dev->hard_header_len);
        err = skb_store_bits(skb, 0, data,
                dev->hard_header_len);
        if (unlikely(err))
            return err;

        data += dev->hard_header_len;
        to_write -= dev->hard_header_len;
    }

    err = -EFAULT;
    offset = offset_in_page(data);
    len_max = PAGE_SIZE - offset;
    len = ((to_write > len_max) ? len_max : to_write);

    skb->data_len = to_write;
    skb->len += to_write;
    skb->truesize += to_write;
    atomic_add(to_write, &po->sk.sk_wmem_alloc);

    while (likely(to_write)) {
        nr_frags = skb_shinfo(skb)->nr_frags;

        if (unlikely(nr_frags >= MAX_SKB_FRAGS)) {
            pr_err("Packet exceed the number of skb frags(%lu)\n",
                   MAX_SKB_FRAGS);
            return -EFAULT;
        }

        page = pgv_to_page(data);
        data += len;
        flush_dcache_page(page);
        get_page(page);
        skb_fill_page_desc(skb, nr_frags, page, offset, len);
        to_write -= len;
        offset = 0;
        len_max = PAGE_SIZE;
        len = ((to_write > len_max) ? len_max : to_write);
    }

    return tp_len;
}

static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
{
    struct sk_buff *skb;
    struct net_device *dev;
    __be16 proto;
    bool need_rls_dev = false;
    int err, reserve = 0;
    void *ph;
    struct sockaddr_ll *saddr = (struct sockaddr_ll *)msg->msg_name;
    int tp_len, size_max;
    unsigned char *addr;
    int len_sum = 0;
    int status = TP_STATUS_AVAILABLE;
    int hlen, tlen;

    mutex_lock(&po->pg_vec_lock);

    err = -EBUSY;
    if (saddr == NULL) {
        dev = po->prot_hook.dev;
        proto   = po->num;
        addr    = NULL;
    } else {
        err = -EINVAL;
        if (msg->msg_namelen < sizeof(struct sockaddr_ll))
            goto out;
        if (msg->msg_namelen < (saddr->sll_halen
                    + offsetof(struct sockaddr_ll,
                        sll_addr)))
            goto out;
        proto   = saddr->sll_protocol;
        addr    = saddr->sll_addr;
        dev = dev_get_by_index(sock_net(&po->sk), saddr->sll_ifindex);
        need_rls_dev = true;
    }

    err = -ENXIO;
    if (unlikely(dev == NULL))
        goto out;

    reserve = dev->hard_header_len;

    err = -ENETDOWN;
    if (unlikely(!(dev->flags & IFF_UP)))
        goto out_put;

    size_max = po->tx_ring.frame_size
        - (po->tp_hdrlen - sizeof(struct sockaddr_ll));

    if (size_max > dev->mtu + reserve)
        size_max = dev->mtu + reserve;

    do {
        ph = packet_current_frame(po, &po->tx_ring,
                TP_STATUS_SEND_REQUEST);

        if (unlikely(ph == NULL)) {
            schedule();
            continue;
        }

        status = TP_STATUS_SEND_REQUEST;
        hlen = LL_RESERVED_SPACE(dev);
        tlen = dev->needed_tailroom;
        skb = sock_alloc_send_skb(&po->sk,
                hlen + tlen + sizeof(struct sockaddr_ll),
                0, &err);

        if (unlikely(skb == NULL))
            goto out_status;

        tp_len = tpacket_fill_skb(po, skb, ph, dev, size_max, proto,
                addr, hlen);

        if (unlikely(tp_len < 0)) {
            if (po->tp_loss) {
                __packet_set_status(po, ph,
                        TP_STATUS_AVAILABLE);
                packet_increment_head(&po->tx_ring);
                kfree_skb(skb);
                continue;
            } else {
                status = TP_STATUS_WRONG_FORMAT;
                err = tp_len;
                goto out_status;
            }
        }

        skb->destructor = tpacket_destruct_skb;
        __packet_set_status(po, ph, TP_STATUS_SENDING);
        atomic_inc(&po->tx_ring.pending);

        status = TP_STATUS_SEND_REQUEST;
        err = dev_queue_xmit(skb);
        if (unlikely(err > 0)) {
            err = net_xmit_errno(err);
            if (err && __packet_get_status(po, ph) ==
                   TP_STATUS_AVAILABLE) {
                /* skb was destructed already */
                skb = NULL;
                goto out_status;
            }
            /*
             * skb was dropped but not destructed yet;
             * let's treat it like congestion or err < 0
             */
            err = 0;
        }
        packet_increment_head(&po->tx_ring);
        len_sum += tp_len;
    } while (likely((ph != NULL) ||
            ((!(msg->msg_flags & MSG_DONTWAIT)) &&
             (atomic_read(&po->tx_ring.pending))))
        );

    err = len_sum;
    goto out_put;

out_status:
    __packet_set_status(po, ph, status);
    kfree_skb(skb);
out_put:
    if (need_rls_dev)
        dev_put(dev);
out:
    mutex_unlock(&po->pg_vec_lock);
    return err;
}

static struct sk_buff *packet_alloc_skb(struct sock *sk, size_t prepad,
                        size_t reserve, size_t len,
                        size_t linear, int noblock,
                        int *err)
{
    struct sk_buff *skb;

    /* Under a page?  Don't bother with paged skb. */
    if (prepad + len < PAGE_SIZE || !linear)
        linear = len;

    skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
                   err);
    if (!skb)
        return NULL;

    skb_reserve(skb, reserve);
    skb_put(skb, linear);
    skb->data_len = len - linear;
    skb->len += len - linear;

    return skb;
}

static int packet_snd(struct socket *sock,
              struct msghdr *msg, size_t len)
{
    struct sock *sk = sock->sk;
    struct sockaddr_ll *saddr = (struct sockaddr_ll *)msg->msg_name;
    struct sk_buff *skb;
    struct net_device *dev;
    __be16 proto;
    bool need_rls_dev = false;
    unsigned char *addr;
    int err, reserve = 0;
    struct virtio_net_hdr vnet_hdr = { 0 };
    int offset = 0;
    int vnet_hdr_len;
    struct packet_sock *po = pkt_sk(sk);
    unsigned short gso_type = 0;
    int hlen, tlen;
    int extra_len = 0;

    /*
     *  Get and verify the address.
     */

    if (saddr == NULL) {
        dev = po->prot_hook.dev;
        proto   = po->num;
        addr    = NULL;
    } else {
        err = -EINVAL;
        if (msg->msg_namelen < sizeof(struct sockaddr_ll))
            goto out;
        if (msg->msg_namelen < (saddr->sll_halen + offsetof(struct sockaddr_ll, sll_addr)))
            goto out;
        proto   = saddr->sll_protocol;
        addr    = saddr->sll_addr;
        dev = dev_get_by_index(sock_net(sk), saddr->sll_ifindex);
        need_rls_dev = true;
    }

    err = -ENXIO;
    if (dev == NULL)
        goto out_unlock;
    if (sock->type == SOCK_RAW)
        reserve = dev->hard_header_len;

    err = -ENETDOWN;
    if (!(dev->flags & IFF_UP))
        goto out_unlock;

    if (po->has_vnet_hdr) {
        vnet_hdr_len = sizeof(vnet_hdr);

        err = -EINVAL;
        if (len < vnet_hdr_len)
            goto out_unlock;

        len -= vnet_hdr_len;

        err = memcpy_fromiovec((void *)&vnet_hdr, msg->msg_iov,
                       vnet_hdr_len);
        if (err < 0)
            goto out_unlock;

        if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
            (vnet_hdr.csum_start + vnet_hdr.csum_offset + 2 >
              vnet_hdr.hdr_len))
            vnet_hdr.hdr_len = vnet_hdr.csum_start +
                         vnet_hdr.csum_offset + 2;

        err = -EINVAL;
        if (vnet_hdr.hdr_len > len)
            goto out_unlock;

        if (vnet_hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
            switch (vnet_hdr.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
            case VIRTIO_NET_HDR_GSO_TCPV4:
                gso_type = SKB_GSO_TCPV4;
                break;
            case VIRTIO_NET_HDR_GSO_TCPV6:
                gso_type = SKB_GSO_TCPV6;
                break;
            case VIRTIO_NET_HDR_GSO_UDP:
                gso_type = SKB_GSO_UDP;
                break;
            default:
                goto out_unlock;
            }

            if (vnet_hdr.gso_type & VIRTIO_NET_HDR_GSO_ECN)
                gso_type |= SKB_GSO_TCP_ECN;

            if (vnet_hdr.gso_size == 0)
                goto out_unlock;

        }
    }

    if (unlikely(sock_flag(sk, SOCK_NOFCS))) {
        if (!netif_supports_nofcs(dev)) {
            err = -EPROTONOSUPPORT;
            goto out_unlock;
        }
        extra_len = 4; /* We're doing our own CRC */
    }

    err = -EMSGSIZE;
    if (!gso_type && (len > dev->mtu + reserve + VLAN_HLEN + extra_len))
        goto out_unlock;

    err = -ENOBUFS;
    hlen = LL_RESERVED_SPACE(dev);
    tlen = dev->needed_tailroom;
    skb = packet_alloc_skb(sk, hlen + tlen, hlen, len, vnet_hdr.hdr_len,
                   msg->msg_flags & MSG_DONTWAIT, &err);
    if (skb == NULL)
        goto out_unlock;

    skb_set_network_header(skb, reserve);

    err = -EINVAL;
    if (sock->type == SOCK_DGRAM &&
        (offset = dev_hard_header(skb, dev, ntohs(proto), addr, NULL, len)) < 0)
        goto out_free;

    /* Returns -EFAULT on error */
    err = skb_copy_datagram_from_iovec(skb, offset, msg->msg_iov, 0, len);
    if (err)
        goto out_free;
    err = sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);
    if (err < 0)
        goto out_free;

    if (!gso_type && (len > dev->mtu + reserve + extra_len)) {
        /* Earlier code assumed this would be a VLAN pkt,
         * double-check this now that we have the actual
         * packet in hand.
         */
        struct ethhdr *ehdr;
        skb_reset_mac_header(skb);
        ehdr = eth_hdr(skb);
        if (ehdr->h_proto != htons(ETH_P_8021Q)) {
            err = -EMSGSIZE;
            goto out_free;
        }
    }

    skb->protocol = proto;
    skb->dev = dev;
    skb->priority = sk->sk_priority;
    skb->mark = sk->sk_mark;

    if (po->has_vnet_hdr) {
        if (vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
            if (!skb_partial_csum_set(skb, vnet_hdr.csum_start,
                          vnet_hdr.csum_offset)) {
                err = -EINVAL;
                goto out_free;
            }
        }

        skb_shinfo(skb)->gso_size = vnet_hdr.gso_size;
        skb_shinfo(skb)->gso_type = gso_type;

        /* Header must be checked, and gso_segs computed. */
        skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
        skb_shinfo(skb)->gso_segs = 0;

        len += vnet_hdr_len;
    }

    if (unlikely(extra_len == 4))
        skb->no_fcs = 1;

    /*
     *  Now send it
     */

    err = dev_queue_xmit(skb);
    if (err > 0 && (err = net_xmit_errno(err)) != 0)
        goto out_unlock;

    if (need_rls_dev)
        dev_put(dev);

    return len;

out_free:
    kfree_skb(skb);
out_unlock:
    if (dev && need_rls_dev)
        dev_put(dev);
out:
    return err;
}

static int packet_sendmsg(struct kiocb *iocb, struct socket *sock,
        struct msghdr *msg, size_t len)
{
    struct sock *sk = sock->sk;
    struct packet_sock *po = pkt_sk(sk);
    if (po->tx_ring.pg_vec)
        return tpacket_snd(po, msg);
    else
        return packet_snd(sock, msg, len);
}

/*
 *  Close a PACKET socket. This is fairly simple. We immediately go
 *  to 'closed' state and remove our protocol entry in the device list.
 */

static int packet_release(struct socket *sock)
{
    struct sock *sk = sock->sk;
    struct packet_sock *po;
    struct net *net;
    union tpacket_req_u req_u;

    if (!sk)
        return 0;

    net = sock_net(sk);
    po = pkt_sk(sk);

    mutex_lock(&net->packet.sklist_lock);
    sk_del_node_init_rcu(sk);
    mutex_unlock(&net->packet.sklist_lock);

    preempt_disable();
    sock_prot_inuse_add(net, sk->sk_prot, -1);
    preempt_enable();

    spin_lock(&po->bind_lock);
    unregister_prot_hook(sk, false);
    if (po->prot_hook.dev) {
        dev_put(po->prot_hook.dev);
        po->prot_hook.dev = NULL;
    }
    spin_unlock(&po->bind_lock);

    packet_flush_mclist(sk);

    memset(&req_u, 0, sizeof(req_u));

    if (po->rx_ring.pg_vec)
        packet_set_ring(sk, &req_u, 1, 0);

    if (po->tx_ring.pg_vec)
        packet_set_ring(sk, &req_u, 1, 1);

    fanout_release(sk);

    synchronize_net();
    /*
     *  Now the socket is dead. No more input will appear.
     */
    sock_orphan(sk);
    sock->sk = NULL;

    /* Purge queues */

    skb_queue_purge(&sk->sk_receive_queue);
    sk_refcnt_debug_release(sk);

    sock_put(sk);
    return 0;
}

/*
 *  Attach a packet hook.
 */

static int packet_do_bind(struct sock *sk, struct net_device *dev, __be16 protocol)
{
    struct packet_sock *po = pkt_sk(sk);

    if (po->fanout) {
        if (dev)
            dev_put(dev);

        return -EINVAL;
    }

    lock_sock(sk);

    spin_lock(&po->bind_lock);
    unregister_prot_hook(sk, true);
    po->num = protocol;
    po->prot_hook.type = protocol;
    if (po->prot_hook.dev)
        dev_put(po->prot_hook.dev);
    po->prot_hook.dev = dev;

    po->ifindex = dev ? dev->ifindex : 0;

    if (protocol == 0)
        goto out_unlock;

    if (!dev || (dev->flags & IFF_UP)) {
        register_prot_hook(sk);
    } else {
        sk->sk_err = ENETDOWN;
        if (!sock_flag(sk, SOCK_DEAD))
            sk->sk_error_report(sk);
    }

out_unlock:
    spin_unlock(&po->bind_lock);
    release_sock(sk);
    return 0;
}

/*
 *  Bind a packet socket to a device
 */

static int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr,
                int addr_len)
{
    struct sock *sk = sock->sk;
    char name[15];
    struct net_device *dev;
    int err = -ENODEV;

    /*
     *  Check legality
     */

    if (addr_len != sizeof(struct sockaddr))
        return -EINVAL;
    strlcpy(name, uaddr->sa_data, sizeof(name));

    dev = dev_get_by_name(sock_net(sk), name);
    if (dev)
        err = packet_do_bind(sk, dev, pkt_sk(sk)->num);
    return err;
}

static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
    struct sockaddr_ll *sll = (struct sockaddr_ll *)uaddr;
    struct sock *sk = sock->sk;
    struct net_device *dev = NULL;
    int err;


    /*
     *  Check legality
     */

    if (addr_len < sizeof(struct sockaddr_ll))
        return -EINVAL;
    if (sll->sll_family != AF_PACKET)
        return -EINVAL;

    if (sll->sll_ifindex) {
        err = -ENODEV;
        dev = dev_get_by_index(sock_net(sk), sll->sll_ifindex);
        if (dev == NULL)
            goto out;
    }
    err = packet_do_bind(sk, dev, sll->sll_protocol ? : pkt_sk(sk)->num);

out:
    return err;
}

static struct proto packet_proto = {
    .name     = "PACKET",
    .owner    = THIS_MODULE,
    .obj_size = sizeof(struct packet_sock),
};

/*
 *  Create a packet of type SOCK_PACKET.
 */

static int packet_create(struct net *net, struct socket *sock, int protocol,
             int kern)
{
    struct sock *sk;
    struct packet_sock *po;
    __be16 proto = (__force __be16)protocol; /* weird, but documented */
    int err;

    if (!capable(CAP_NET_RAW))
        return -EPERM;
    if (sock->type != SOCK_DGRAM && sock->type != SOCK_RAW &&
        sock->type != SOCK_PACKET)
        return -ESOCKTNOSUPPORT;

    sock->state = SS_UNCONNECTED;

    err = -ENOBUFS;
    sk = sk_alloc(net, PF_PACKET, GFP_KERNEL, &packet_proto);
    if (sk == NULL)
        goto out;

    sock->ops = &packet_ops;
    if (sock->type == SOCK_PACKET)
        sock->ops = &packet_ops_spkt;

    sock_init_data(sock, sk);

    po = pkt_sk(sk);
    sk->sk_family = PF_PACKET;
    po->num = proto;

    sk->sk_destruct = packet_sock_destruct;
    sk_refcnt_debug_inc(sk);

    /*
     *  Attach a protocol block
     */

    spin_lock_init(&po->bind_lock);
    mutex_init(&po->pg_vec_lock);
    po->prot_hook.func = packet_rcv;

    if (sock->type == SOCK_PACKET)
        po->prot_hook.func = packet_rcv_spkt;

    po->prot_hook.af_packet_priv = sk;

    if (proto) {
        po->prot_hook.type = proto;
        register_prot_hook(sk);
    }

    mutex_lock(&net->packet.sklist_lock);
    sk_add_node_rcu(sk, &net->packet.sklist);
    mutex_unlock(&net->packet.sklist_lock);

    preempt_disable();
    sock_prot_inuse_add(net, &packet_proto, 1);
    preempt_enable();

    return 0;
out:
    return err;
}

static int packet_recv_error(struct sock *sk, struct msghdr *msg, int len)
{
    struct sock_exterr_skb *serr;
    struct sk_buff *skb, *skb2;
    int copied, err;

    err = -EAGAIN;
    skb = skb_dequeue(&sk->sk_error_queue);
    if (skb == NULL)
        goto out;

    copied = skb->len;
    if (copied > len) {
        msg->msg_flags |= MSG_TRUNC;
        copied = len;
    }
    err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
    if (err)
        goto out_free_skb;

    sock_recv_timestamp(msg, sk, skb);

    serr = SKB_EXT_ERR(skb);
    put_cmsg(msg, SOL_PACKET, PACKET_TX_TIMESTAMP,
         sizeof(serr->ee), &serr->ee);

    msg->msg_flags |= MSG_ERRQUEUE;
    err = copied;

    /* Reset and regenerate socket error */
    spin_lock_bh(&sk->sk_error_queue.lock);
    sk->sk_err = 0;
    if ((skb2 = skb_peek(&sk->sk_error_queue)) != NULL) {
        sk->sk_err = SKB_EXT_ERR(skb2)->ee.ee_errno;
        spin_unlock_bh(&sk->sk_error_queue.lock);
        sk->sk_error_report(sk);
    } else
        spin_unlock_bh(&sk->sk_error_queue.lock);

out_free_skb:
    kfree_skb(skb);
out:
    return err;
}

/*
 *  Pull a packet from our receive queue and hand it to the user.
 *  If necessary we block.
 */

static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
              struct msghdr *msg, size_t len, int flags)
{
    struct sock *sk = sock->sk;
    struct sk_buff *skb;
    int copied, err;
    struct sockaddr_ll *sll;
    int vnet_hdr_len = 0;

    err = -EINVAL;
    if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT|MSG_ERRQUEUE))
        goto out;

#if 0
    /* What error should we return now? EUNATTACH? */
    if (pkt_sk(sk)->ifindex < 0)
        return -ENODEV;
#endif

    if (flags & MSG_ERRQUEUE) {
        err = packet_recv_error(sk, msg, len);
        goto out;
    }

    /*
     *  Call the generic datagram receiver. This handles all sorts
     *  of horrible races and re-entrancy so we can forget about it
     *  in the protocol layers.
     *
     *  Now it will return ENETDOWN, if device have just gone down,
     *  but then it will block.
     */

    skb = skb_recv_datagram(sk, flags, flags & MSG_DONTWAIT, &err);

    /*
     *  An error occurred so return it. Because skb_recv_datagram()
     *  handles the blocking we don't see and worry about blocking
     *  retries.
     */

    if (skb == NULL)
        goto out;

    if (pkt_sk(sk)->has_vnet_hdr) {
        struct virtio_net_hdr vnet_hdr = { 0 };

        err = -EINVAL;
        vnet_hdr_len = sizeof(vnet_hdr);
        if (len < vnet_hdr_len)
            goto out_free;

        len -= vnet_hdr_len;

        if (skb_is_gso(skb)) {
            struct skb_shared_info *sinfo = skb_shinfo(skb);

            /* This is a hint as to how much should be linear. */
            vnet_hdr.hdr_len = skb_headlen(skb);
            vnet_hdr.gso_size = sinfo->gso_size;
            if (sinfo->gso_type & SKB_GSO_TCPV4)
                vnet_hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
            else if (sinfo->gso_type & SKB_GSO_TCPV6)
                vnet_hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
            else if (sinfo->gso_type & SKB_GSO_UDP)
                vnet_hdr.gso_type = VIRTIO_NET_HDR_GSO_UDP;
            else if (sinfo->gso_type & SKB_GSO_FCOE)
                goto out_free;
            else
                BUG();
            if (sinfo->gso_type & SKB_GSO_TCP_ECN)
                vnet_hdr.gso_type |= VIRTIO_NET_HDR_GSO_ECN;
        } else
            vnet_hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE;

        if (skb->ip_summed == CHECKSUM_PARTIAL) {
            vnet_hdr.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
            vnet_hdr.csum_start = skb_checksum_start_offset(skb);
            vnet_hdr.csum_offset = skb->csum_offset;
        } else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
            vnet_hdr.flags = VIRTIO_NET_HDR_F_DATA_VALID;
        } /* else everything is zero */

        err = memcpy_toiovec(msg->msg_iov, (void *)&vnet_hdr,
                     vnet_hdr_len);
        if (err < 0)
            goto out_free;
    }

    /*
     *  If the address length field is there to be filled in, we fill
     *  it in now.
     */

    sll = &PACKET_SKB_CB(skb)->sa.ll;
    if (sock->type == SOCK_PACKET)
        msg->msg_namelen = sizeof(struct sockaddr_pkt);
    else
        msg->msg_namelen = sll->sll_halen + offsetof(struct sockaddr_ll, sll_addr);

    /*
     *  You lose any data beyond the buffer you gave. If it worries a
     *  user program they can ask the device for its MTU anyway.
     */

    copied = skb->len;
    if (copied > len) {
        copied = len;
        msg->msg_flags |= MSG_TRUNC;
    }

    err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
    if (err)
        goto out_free;

    sock_recv_ts_and_drops(msg, sk, skb);

    if (msg->msg_name)
        memcpy(msg->msg_name, &PACKET_SKB_CB(skb)->sa,
               msg->msg_namelen);

    if (pkt_sk(sk)->auxdata) {
        struct tpacket_auxdata aux;

        aux.tp_status = TP_STATUS_USER;
        if (skb->ip_summed == CHECKSUM_PARTIAL)
            aux.tp_status |= TP_STATUS_CSUMNOTREADY;
        aux.tp_len = PACKET_SKB_CB(skb)->origlen;
        aux.tp_snaplen = skb->len;
        aux.tp_mac = 0;
        aux.tp_net = skb_network_offset(skb);
        if (vlan_tx_tag_present(skb)) {
            aux.tp_vlan_tci = vlan_tx_tag_get(skb);
            aux.tp_status |= TP_STATUS_VLAN_VALID;
        } else {
            aux.tp_vlan_tci = 0;
        }
        aux.tp_padding = 0;
        put_cmsg(msg, SOL_PACKET, PACKET_AUXDATA, sizeof(aux), &aux);
    }

    /*
     *  Free or return the buffer as appropriate. Again this
     *  hides all the races and re-entrancy issues from us.
     */
    err = vnet_hdr_len + ((flags&MSG_TRUNC) ? skb->len : copied);

out_free:
    skb_free_datagram(sk, skb);
out:
    return err;
}

static int packet_getname_spkt(struct socket *sock, struct sockaddr *uaddr,
                   int *uaddr_len, int peer)
{
    struct net_device *dev;
    struct sock *sk = sock->sk;

    if (peer)
        return -EOPNOTSUPP;

    uaddr->sa_family = AF_PACKET;
    rcu_read_lock();
    dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex);
    if (dev)
        strncpy(uaddr->sa_data, dev->name, 14);
    else
        memset(uaddr->sa_data, 0, 14);
    rcu_read_unlock();
    *uaddr_len = sizeof(*uaddr);

    return 0;
}

static int packet_getname(struct socket *sock, struct sockaddr *uaddr,
              int *uaddr_len, int peer)
{
    struct net_device *dev;
    struct sock *sk = sock->sk;
    struct packet_sock *po = pkt_sk(sk);
    DECLARE_SOCKADDR(struct sockaddr_ll *, sll, uaddr);

    if (peer)
        return -EOPNOTSUPP;

    sll->sll_family = AF_PACKET;
    sll->sll_ifindex = po->ifindex;
    sll->sll_protocol = po->num;
    sll->sll_pkttype = 0;
    rcu_read_lock();
    dev = dev_get_by_index_rcu(sock_net(sk), po->ifindex);
    if (dev) {
        sll->sll_hatype = dev->type;
        sll->sll_halen = dev->addr_len;
        memcpy(sll->sll_addr, dev->dev_addr, dev->addr_len);
    } else {
        sll->sll_hatype = 0;    /* Bad: we have no ARPHRD_UNSPEC */
        sll->sll_halen = 0;
    }
    rcu_read_unlock();
    *uaddr_len = offsetof(struct sockaddr_ll, sll_addr) + sll->sll_halen;

    return 0;
}

static int packet_dev_mc(struct net_device *dev, struct packet_mclist *i,
             int what)
{
    switch (i->type) {
    case PACKET_MR_MULTICAST:
        if (i->alen != dev->addr_len)
            return -EINVAL;
        if (what > 0)
            return dev_mc_add(dev, i->addr);
        else
            return dev_mc_del(dev, i->addr);
        break;
    case PACKET_MR_PROMISC:
        return dev_set_promiscuity(dev, what);
        break;
    case PACKET_MR_ALLMULTI:
        return dev_set_allmulti(dev, what);
        break;
    case PACKET_MR_UNICAST:
        if (i->alen != dev->addr_len)
            return -EINVAL;
        if (what > 0)
            return dev_uc_add(dev, i->addr);
        else
            return dev_uc_del(dev, i->addr);
        break;
    default:
        break;
    }
    return 0;
}

static void packet_dev_mclist(struct net_device *dev, struct packet_mclist *i, int what)
{
    for ( ; i; i = i->next) {
        if (i->ifindex == dev->ifindex)
            packet_dev_mc(dev, i, what);
    }
}

static int packet_mc_add(struct sock *sk, struct packet_mreq_max *mreq)
{
    struct packet_sock *po = pkt_sk(sk);
    struct packet_mclist *ml, *i;
    struct net_device *dev;
    int err;

    rtnl_lock();

    err = -ENODEV;
    dev = __dev_get_by_index(sock_net(sk), mreq->mr_ifindex);
    if (!dev)
        goto done;

    err = -EINVAL;
    if (mreq->mr_alen > dev->addr_len)
        goto done;

    err = -ENOBUFS;
    i = kmalloc(sizeof(*i), GFP_KERNEL);
    if (i == NULL)
        goto done;

    err = 0;
    for (ml = po->mclist; ml; ml = ml->next) {
        if (ml->ifindex == mreq->mr_ifindex &&
            ml->type == mreq->mr_type &&
            ml->alen == mreq->mr_alen &&
            memcmp(ml->addr, mreq->mr_address, ml->alen) == 0) {
            ml->count++;
            /* Free the new element ... */
            kfree(i);
            goto done;
        }
    }

    i->type = mreq->mr_type;
    i->ifindex = mreq->mr_ifindex;
    i->alen = mreq->mr_alen;
    memcpy(i->addr, mreq->mr_address, i->alen);
    i->count = 1;
    i->next = po->mclist;
    po->mclist = i;
    err = packet_dev_mc(dev, i, 1);
    if (err) {
        po->mclist = i->next;
        kfree(i);
    }

done:
    rtnl_unlock();
    return err;
}

static int packet_mc_drop(struct sock *sk, struct packet_mreq_max *mreq)
{
    struct packet_mclist *ml, **mlp;

    rtnl_lock();

    for (mlp = &pkt_sk(sk)->mclist; (ml = *mlp) != NULL; mlp = &ml->next) {
        if (ml->ifindex == mreq->mr_ifindex &&
            ml->type == mreq->mr_type &&
            ml->alen == mreq->mr_alen &&
            memcmp(ml->addr, mreq->mr_address, ml->alen) == 0) {
            if (--ml->count == 0) {
                struct net_device *dev;
                *mlp = ml->next;
                dev = __dev_get_by_index(sock_net(sk), ml->ifindex);
                if (dev)
                    packet_dev_mc(dev, ml, -1);
                kfree(ml);
            }
            rtnl_unlock();
            return 0;
        }
    }
    rtnl_unlock();
    return -EADDRNOTAVAIL;
}

static void packet_flush_mclist(struct sock *sk)
{
    struct packet_sock *po = pkt_sk(sk);
    struct packet_mclist *ml;

    if (!po->mclist)
        return;

    rtnl_lock();
    while ((ml = po->mclist) != NULL) {
        struct net_device *dev;

        po->mclist = ml->next;
        dev = __dev_get_by_index(sock_net(sk), ml->ifindex);
        if (dev != NULL)
            packet_dev_mc(dev, ml, -1);
        kfree(ml);
    }
    rtnl_unlock();
}

static int
packet_setsockopt(struct socket *sock, int level, int optname, char __user *optval, unsigned int optlen)
{
    struct sock *sk = sock->sk;
    struct packet_sock *po = pkt_sk(sk);
    int ret;

    if (level != SOL_PACKET)
        return -ENOPROTOOPT;

    switch (optname) {
    case PACKET_ADD_MEMBERSHIP:
    case PACKET_DROP_MEMBERSHIP:
    {
        struct packet_mreq_max mreq;
        int len = optlen;
        memset(&mreq, 0, sizeof(mreq));
        if (len < sizeof(struct packet_mreq))
            return -EINVAL;
        if (len > sizeof(mreq))
            len = sizeof(mreq);
        if (copy_from_user(&mreq, optval, len))
            return -EFAULT;
        if (len < (mreq.mr_alen + offsetof(struct packet_mreq, mr_address)))
            return -EINVAL;
        if (optname == PACKET_ADD_MEMBERSHIP)
            ret = packet_mc_add(sk, &mreq);
        else
            ret = packet_mc_drop(sk, &mreq);
        return ret;
    }

    case PACKET_RX_RING:
    case PACKET_TX_RING:
    {
        union tpacket_req_u req_u;
        int len;

        switch (po->tp_version) {
        case TPACKET_V1:
        case TPACKET_V2:
            len = sizeof(req_u.req);
            break;
        case TPACKET_V3:
        default:
            len = sizeof(req_u.req3);
            break;
        }
        if (optlen < len)
            return -EINVAL;
        if (pkt_sk(sk)->has_vnet_hdr)
            return -EINVAL;
        if (copy_from_user(&req_u.req, optval, len))
            return -EFAULT;
        return packet_set_ring(sk, &req_u, 0,
            optname == PACKET_TX_RING);
    }
    case PACKET_COPY_THRESH:
    {
        int val;

        if (optlen != sizeof(val))
            return -EINVAL;
        if (copy_from_user(&val, optval, sizeof(val)))
            return -EFAULT;

        pkt_sk(sk)->copy_thresh = val;
        return 0;
    }
    case PACKET_VERSION:
    {
        int val;

        if (optlen != sizeof(val))
            return -EINVAL;
        if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
            return -EBUSY;
        if (copy_from_user(&val, optval, sizeof(val)))
            return -EFAULT;
        switch (val) {
        case TPACKET_V1:
        case TPACKET_V2:
        case TPACKET_V3:
            po->tp_version = val;
            return 0;
        default:
            return -EINVAL;
        }
    }
    case PACKET_RESERVE:
    {
        unsigned int val;

        if (optlen != sizeof(val))
            return -EINVAL;
        if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
            return -EBUSY;
        if (copy_from_user(&val, optval, sizeof(val)))
            return -EFAULT;
        po->tp_reserve = val;
        return 0;
    }
    case PACKET_LOSS:
    {
        unsigned int val;

        if (optlen != sizeof(val))
            return -EINVAL;
        if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
            return -EBUSY;
        if (copy_from_user(&val, optval, sizeof(val)))
            return -EFAULT;
        po->tp_loss = !!val;
        return 0;
    }
    case PACKET_AUXDATA:
    {
        int val;

        if (optlen < sizeof(val))
            return -EINVAL;
        if (copy_from_user(&val, optval, sizeof(val)))
            return -EFAULT;

        po->auxdata = !!val;
        return 0;
    }
    case PACKET_ORIGDEV:
    {
        int val;

        if (optlen < sizeof(val))
            return -EINVAL;
        if (copy_from_user(&val, optval, sizeof(val)))
            return -EFAULT;

        po->origdev = !!val;
        return 0;
    }
    case PACKET_VNET_HDR:
    {
        int val;

        if (sock->type != SOCK_RAW)
            return -EINVAL;
        if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
            return -EBUSY;
        if (optlen < sizeof(val))
            return -EINVAL;
        if (copy_from_user(&val, optval, sizeof(val)))
            return -EFAULT;

        po->has_vnet_hdr = !!val;
        return 0;
    }
    case PACKET_TIMESTAMP:
    {
        int val;

        if (optlen != sizeof(val))
            return -EINVAL;
        if (copy_from_user(&val, optval, sizeof(val)))
            return -EFAULT;

        po->tp_tstamp = val;
        return 0;
    }
    case PACKET_FANOUT:
    {
        int val;

        if (optlen != sizeof(val))
            return -EINVAL;
        if (copy_from_user(&val, optval, sizeof(val)))
            return -EFAULT;

        return fanout_add(sk, val & 0xffff, val >> 16);
    }
    default:
        return -ENOPROTOOPT;
    }
}

static int packet_getsockopt(struct socket *sock, int level, int optname,
                 char __user *optval, int __user *optlen)
{
    int len;
    int val, lv = sizeof(val);
    struct sock *sk = sock->sk;
    struct packet_sock *po = pkt_sk(sk);
    void *data = &val;
    struct tpacket_stats st;
    union tpacket_stats_u st_u;

    if (level != SOL_PACKET)
        return -ENOPROTOOPT;

    if (get_user(len, optlen))
        return -EFAULT;

    if (len < 0)
        return -EINVAL;

    switch (optname) {
    case PACKET_STATISTICS:
        spin_lock_bh(&sk->sk_receive_queue.lock);
        if (po->tp_version == TPACKET_V3) {
            lv = sizeof(struct tpacket_stats_v3);
            memcpy(&st_u.stats3, &po->stats,
                   sizeof(struct tpacket_stats));
            st_u.stats3.tp_freeze_q_cnt =
                    po->stats_u.stats3.tp_freeze_q_cnt;
            st_u.stats3.tp_packets += po->stats.tp_drops;
            data = &st_u.stats3;
        } else {
            lv = sizeof(struct tpacket_stats);
            st = po->stats;
            st.tp_packets += st.tp_drops;
            data = &st;
        }
        memset(&po->stats, 0, sizeof(st));
        spin_unlock_bh(&sk->sk_receive_queue.lock);
        break;
    case PACKET_AUXDATA:
        val = po->auxdata;
        break;
    case PACKET_ORIGDEV:
        val = po->origdev;
        break;
    case PACKET_VNET_HDR:
        val = po->has_vnet_hdr;
        break;
    case PACKET_VERSION:
        val = po->tp_version;
        break;
    case PACKET_HDRLEN:
        if (len > sizeof(int))
            len = sizeof(int);
        if (copy_from_user(&val, optval, len))
            return -EFAULT;
        switch (val) {
        case TPACKET_V1:
            val = sizeof(struct tpacket_hdr);
            break;
        case TPACKET_V2:
            val = sizeof(struct tpacket2_hdr);
            break;
        case TPACKET_V3:
            val = sizeof(struct tpacket3_hdr);
            break;
        default:
            return -EINVAL;
        }
        break;
    case PACKET_RESERVE:
        val = po->tp_reserve;
        break;
    case PACKET_LOSS:
        val = po->tp_loss;
        break;
    case PACKET_TIMESTAMP:
        val = po->tp_tstamp;
        break;
    case PACKET_FANOUT:
        val = (po->fanout ?
               ((u32)po->fanout->id |
            ((u32)po->fanout->type << 16)) :
               0);
        break;
    default:
        return -ENOPROTOOPT;
    }

    if (len > lv)
        len = lv;
    if (put_user(len, optlen))
        return -EFAULT;
    if (copy_to_user(optval, data, len))
        return -EFAULT;
    return 0;
}


static int packet_notifier(struct notifier_block *this, unsigned long msg, void *data)
{
    struct sock *sk;
    struct hlist_node *node;
    struct net_device *dev = data;
    struct net *net = dev_net(dev);

    rcu_read_lock();
    sk_for_each_rcu(sk, node, &net->packet.sklist) {
        struct packet_sock *po = pkt_sk(sk);

        switch (msg) {
        case NETDEV_UNREGISTER:
            if (po->mclist)
                packet_dev_mclist(dev, po->mclist, -1);
            /* fallthrough */

        case NETDEV_DOWN:
            if (dev->ifindex == po->ifindex) {
                spin_lock(&po->bind_lock);
                if (po->running) {
                    __unregister_prot_hook(sk, false);
                    sk->sk_err = ENETDOWN;
                    if (!sock_flag(sk, SOCK_DEAD))
                        sk->sk_error_report(sk);
                }
                if (msg == NETDEV_UNREGISTER) {
                    po->ifindex = -1;
                    if (po->prot_hook.dev)
                        dev_put(po->prot_hook.dev);
                    po->prot_hook.dev = NULL;
                }
                spin_unlock(&po->bind_lock);
            }
            break;
        case NETDEV_UP:
            if (dev->ifindex == po->ifindex) {
                spin_lock(&po->bind_lock);
                if (po->num)
                    register_prot_hook(sk);
                spin_unlock(&po->bind_lock);
            }
            break;
        }
    }
    rcu_read_unlock();
    return NOTIFY_DONE;
}


static int packet_ioctl(struct socket *sock, unsigned int cmd,
            unsigned long arg)
{
    struct sock *sk = sock->sk;

    switch (cmd) {
    case SIOCOUTQ:
    {
        int amount = sk_wmem_alloc_get(sk);

        return put_user(amount, (int __user *)arg);
    }
    case SIOCINQ:
    {
        struct sk_buff *skb;
        int amount = 0;

        spin_lock_bh(&sk->sk_receive_queue.lock);
        skb = skb_peek(&sk->sk_receive_queue);
        if (skb)
            amount = skb->len;
        spin_unlock_bh(&sk->sk_receive_queue.lock);
        return put_user(amount, (int __user *)arg);
    }
    case SIOCGSTAMP:
        return sock_get_timestamp(sk, (struct timeval __user *)arg);
    case SIOCGSTAMPNS:
        return sock_get_timestampns(sk, (struct timespec __user *)arg);

#ifdef CONFIG_INET
    case SIOCADDRT:
    case SIOCDELRT:
    case SIOCDARP:
    case SIOCGARP:
    case SIOCSARP:
    case SIOCGIFADDR:
    case SIOCSIFADDR:
    case SIOCGIFBRDADDR:
    case SIOCSIFBRDADDR:
    case SIOCGIFNETMASK:
    case SIOCSIFNETMASK:
    case SIOCGIFDSTADDR:
    case SIOCSIFDSTADDR:
    case SIOCSIFFLAGS:
        return inet_dgram_ops.ioctl(sock, cmd, arg);
#endif

    default:
        return -ENOIOCTLCMD;
    }
    return 0;
}

static unsigned int packet_poll(struct file *file, struct socket *sock,
                poll_table *wait)
{
    struct sock *sk = sock->sk;
    struct packet_sock *po = pkt_sk(sk);
    unsigned int mask = datagram_poll(file, sock, wait);

    spin_lock_bh(&sk->sk_receive_queue.lock);
    if (po->rx_ring.pg_vec) {
        if (!packet_previous_rx_frame(po, &po->rx_ring,
            TP_STATUS_KERNEL))
            mask |= POLLIN | POLLRDNORM;
    }
    spin_unlock_bh(&sk->sk_receive_queue.lock);
    spin_lock_bh(&sk->sk_write_queue.lock);
    if (po->tx_ring.pg_vec) {
        if (packet_current_frame(po, &po->tx_ring, TP_STATUS_AVAILABLE))
            mask |= POLLOUT | POLLWRNORM;
    }
    spin_unlock_bh(&sk->sk_write_queue.lock);
    return mask;
}


/* Dirty? Well, I still did not learn better way to account
 * for user mmaps.
 */

static void packet_mm_open(struct vm_area_struct *vma)
{
    struct file *file = vma->vm_file;
    struct socket *sock = file->private_data;
    struct sock *sk = sock->sk;

    if (sk)
        atomic_inc(&pkt_sk(sk)->mapped);
}

static void packet_mm_close(struct vm_area_struct *vma)
{
    struct file *file = vma->vm_file;
    struct socket *sock = file->private_data;
    struct sock *sk = sock->sk;

    if (sk)
        atomic_dec(&pkt_sk(sk)->mapped);
}

static const struct vm_operations_struct packet_mmap_ops = {
    .open   =   packet_mm_open,
    .close  =   packet_mm_close,
};

static void free_pg_vec(struct pgv *pg_vec, unsigned int order,
            unsigned int len)
{
    int i;

    for (i = 0; i < len; i++) {
        if (likely(pg_vec[i].buffer)) {
            if (is_vmalloc_addr(pg_vec[i].buffer))
                vfree(pg_vec[i].buffer);
            else
                free_pages((unsigned long)pg_vec[i].buffer,
                       order);
            pg_vec[i].buffer = NULL;
        }
    }
    kfree(pg_vec);
}

static char *alloc_one_pg_vec_page(unsigned long order)
{
    char *buffer = NULL;
    gfp_t gfp_flags = GFP_KERNEL | __GFP_COMP |
              __GFP_ZERO | __GFP_NOWARN | __GFP_NORETRY;

    buffer = (char *) __get_free_pages(gfp_flags, order);

    if (buffer)
        return buffer;

    /*
     * __get_free_pages failed, fall back to vmalloc
     */
    buffer = vzalloc((1 << order) * PAGE_SIZE);

    if (buffer)
        return buffer;

    /*
     * vmalloc failed, lets dig into swap here
     */
    gfp_flags &= ~__GFP_NORETRY;
    buffer = (char *)__get_free_pages(gfp_flags, order);
    if (buffer)
        return buffer;

    /*
     * complete and utter failure
     */
    return NULL;
}

static struct pgv *alloc_pg_vec(struct tpacket_req *req, int order)
{
    unsigned int block_nr = req->tp_block_nr;
    struct pgv *pg_vec;
    int i;

    pg_vec = kcalloc(block_nr, sizeof(struct pgv), GFP_KERNEL);
    if (unlikely(!pg_vec))
        goto out;

    for (i = 0; i < block_nr; i++) {
        pg_vec[i].buffer = alloc_one_pg_vec_page(order);
        if (unlikely(!pg_vec[i].buffer))
            goto out_free_pgvec;
    }

out:
    return pg_vec;

out_free_pgvec:
    free_pg_vec(pg_vec, order, block_nr);
    pg_vec = NULL;
    goto out;
}

static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
        int closing, int tx_ring)
{
    struct pgv *pg_vec = NULL;
    struct packet_sock *po = pkt_sk(sk);
    int was_running, order = 0;
    struct packet_ring_buffer *rb;
    struct sk_buff_head *rb_queue;
    __be16 num;
    int err = -EINVAL;
    /* Added to avoid minimal code churn */
    struct tpacket_req *req = &req_u->req;

    /* Opening a Tx-ring is NOT supported in TPACKET_V3 */
    if (!closing && tx_ring && (po->tp_version > TPACKET_V2)) {
        WARN(1, "Tx-ring is not supported.\n");
        goto out;
    }

    rb = tx_ring ? &po->tx_ring : &po->rx_ring;
    rb_queue = tx_ring ? &sk->sk_write_queue : &sk->sk_receive_queue;

    err = -EBUSY;
    if (!closing) {
        if (atomic_read(&po->mapped))
            goto out;
        if (atomic_read(&rb->pending))
            goto out;
    }

    if (req->tp_block_nr) {
        /* Sanity tests and some calculations */
        err = -EBUSY;
        if (unlikely(rb->pg_vec))
            goto out;

        switch (po->tp_version) {
        case TPACKET_V1:
            po->tp_hdrlen = TPACKET_HDRLEN;
            break;
        case TPACKET_V2:
            po->tp_hdrlen = TPACKET2_HDRLEN;
            break;
        case TPACKET_V3:
            po->tp_hdrlen = TPACKET3_HDRLEN;
            break;
        }

        err = -EINVAL;
        if (unlikely((int)req->tp_block_size <= 0))
            goto out;
        if (unlikely(req->tp_block_size & (PAGE_SIZE - 1)))
            goto out;
        if (unlikely(req->tp_frame_size < po->tp_hdrlen +
                    po->tp_reserve))
            goto out;
        if (unlikely(req->tp_frame_size & (TPACKET_ALIGNMENT - 1)))
            goto out;

        rb->frames_per_block = req->tp_block_size/req->tp_frame_size;
        if (unlikely(rb->frames_per_block <= 0))
            goto out;
        if (unlikely((rb->frames_per_block * req->tp_block_nr) !=
                    req->tp_frame_nr))
            goto out;

        err = -ENOMEM;
        order = get_order(req->tp_block_size);
        pg_vec = alloc_pg_vec(req, order);
        if (unlikely(!pg_vec))
            goto out;
        switch (po->tp_version) {
        case TPACKET_V3:
        /* Transmit path is not supported. We checked
         * it above but just being paranoid
         */
            if (!tx_ring)
                init_prb_bdqc(po, rb, pg_vec, req_u, tx_ring);
                break;
        default:
            break;
        }
    }
    /* Done */
    else {
        err = -EINVAL;
        if (unlikely(req->tp_frame_nr))
            goto out;
    }

    lock_sock(sk);

    /* Detach socket from network */
    spin_lock(&po->bind_lock);
    was_running = po->running;
    num = po->num;
    if (was_running) {
        po->num = 0;
        __unregister_prot_hook(sk, false);
    }
    spin_unlock(&po->bind_lock);

    synchronize_net();

    err = -EBUSY;
    mutex_lock(&po->pg_vec_lock);
    if (closing || atomic_read(&po->mapped) == 0) {
        err = 0;
        spin_lock_bh(&rb_queue->lock);
        swap(rb->pg_vec, pg_vec);
        rb->frame_max = (req->tp_frame_nr - 1);
        rb->head = 0;
        rb->frame_size = req->tp_frame_size;
        spin_unlock_bh(&rb_queue->lock);

        swap(rb->pg_vec_order, order);
        swap(rb->pg_vec_len, req->tp_block_nr);

        rb->pg_vec_pages = req->tp_block_size/PAGE_SIZE;
        po->prot_hook.func = (po->rx_ring.pg_vec) ?
                        tpacket_rcv : packet_rcv;
        skb_queue_purge(rb_queue);
        if (atomic_read(&po->mapped))
            pr_err("packet_mmap: vma is busy: %d\n",
                   atomic_read(&po->mapped));
    }
    mutex_unlock(&po->pg_vec_lock);

    spin_lock(&po->bind_lock);
    if (was_running) {
        po->num = num;
        register_prot_hook(sk);
    }
    spin_unlock(&po->bind_lock);
    if (closing && (po->tp_version > TPACKET_V2)) {
        /* Because we don't support block-based V3 on tx-ring */
        if (!tx_ring)
            prb_shutdown_retire_blk_timer(po, tx_ring, rb_queue);
    }
    release_sock(sk);

    if (pg_vec)
        free_pg_vec(pg_vec, order, req->tp_block_nr);
out:
    return err;
}

static int packet_mmap(struct file *file, struct socket *sock,
        struct vm_area_struct *vma)
{
    struct sock *sk = sock->sk;
    struct packet_sock *po = pkt_sk(sk);
    unsigned long size, expected_size;
    struct packet_ring_buffer *rb;
    unsigned long start;
    int err = -EINVAL;
    int i;

    if (vma->vm_pgoff)
        return -EINVAL;

    mutex_lock(&po->pg_vec_lock);

    expected_size = 0;
    for (rb = &po->rx_ring; rb <= &po->tx_ring; rb++) {
        if (rb->pg_vec) {
            expected_size += rb->pg_vec_len
                        * rb->pg_vec_pages
                        * PAGE_SIZE;
        }
    }

    if (expected_size == 0)
        goto out;

    size = vma->vm_end - vma->vm_start;
    if (size != expected_size)
        goto out;

    start = vma->vm_start;
    for (rb = &po->rx_ring; rb <= &po->tx_ring; rb++) {
        if (rb->pg_vec == NULL)
            continue;

        for (i = 0; i < rb->pg_vec_len; i++) {
            struct page *page;
            void *kaddr = rb->pg_vec[i].buffer;
            int pg_num;

            for (pg_num = 0; pg_num < rb->pg_vec_pages; pg_num++) {
                page = pgv_to_page(kaddr);
                err = vm_insert_page(vma, start, page);
                if (unlikely(err))
                    goto out;
                start += PAGE_SIZE;
                kaddr += PAGE_SIZE;
            }
        }
    }

    atomic_inc(&po->mapped);
    vma->vm_ops = &packet_mmap_ops;
    err = 0;

out:
    mutex_unlock(&po->pg_vec_lock);
    return err;
}

static const struct proto_ops packet_ops_spkt = {
    .family =   PF_PACKET,
    .owner =    THIS_MODULE,
    .release =  packet_release,
    .bind =     packet_bind_spkt,
    .connect =  sock_no_connect,
    .socketpair =   sock_no_socketpair,
    .accept =   sock_no_accept,
    .getname =  packet_getname_spkt,
    .poll =     datagram_poll,
    .ioctl =    packet_ioctl,
    .listen =   sock_no_listen,
    .shutdown = sock_no_shutdown,
    .setsockopt =   sock_no_setsockopt,
    .getsockopt =   sock_no_getsockopt,
    .sendmsg =  packet_sendmsg_spkt,
    .recvmsg =  packet_recvmsg,
    .mmap =     sock_no_mmap,
    .sendpage = sock_no_sendpage,
};

static const struct proto_ops packet_ops = {
    .family =   PF_PACKET,
    .owner =    THIS_MODULE,
    .release =  packet_release,
    .bind =     packet_bind,
    .connect =  sock_no_connect,
    .socketpair =   sock_no_socketpair,
    .accept =   sock_no_accept,
    .getname =  packet_getname,
    .poll =     packet_poll,
    .ioctl =    packet_ioctl,
    .listen =   sock_no_listen,
    .shutdown = sock_no_shutdown,
    .setsockopt =   packet_setsockopt,
    .getsockopt =   packet_getsockopt,
    .sendmsg =  packet_sendmsg,
    .recvmsg =  packet_recvmsg,
    .mmap =     packet_mmap,
    .sendpage = sock_no_sendpage,
};

static const struct net_proto_family packet_family_ops = {
    .family =   PF_PACKET,
    .create =   packet_create,
    .owner  =   THIS_MODULE,
};

static struct notifier_block packet_netdev_notifier = {
    .notifier_call =    packet_notifier,
};

#ifdef CONFIG_PROC_FS

static void *packet_seq_start(struct seq_file *seq, loff_t *pos)
    __acquires(RCU)
{
    struct net *net = seq_file_net(seq);

    rcu_read_lock();
    return seq_hlist_start_head_rcu(&net->packet.sklist, *pos);
}

static void *packet_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    struct net *net = seq_file_net(seq);
    return seq_hlist_next_rcu(v, &net->packet.sklist, pos);
}

static void packet_seq_stop(struct seq_file *seq, void *v)
    __releases(RCU)
{
    rcu_read_unlock();
}

static int packet_seq_show(struct seq_file *seq, void *v)
{
    if (v == SEQ_START_TOKEN)
        seq_puts(seq, "sk       RefCnt Type Proto  Iface R Rmem   User   Inode\n");
    else {
        struct sock *s = sk_entry(v);
        const struct packet_sock *po = pkt_sk(s);

        seq_printf(seq,
               "%pK %-6d %-4d %04x   %-5d %1d %-6u %-6u %-6lu\n",
               s,
               atomic_read(&s->sk_refcnt),
               s->sk_type,
               ntohs(po->num),
               po->ifindex,
               po->running,
               atomic_read(&s->sk_rmem_alloc),
               from_kuid_munged(seq_user_ns(seq), sock_i_uid(s)),
               sock_i_ino(s));
    }

    return 0;
}

static const struct seq_operations packet_seq_ops = {
    .start  = packet_seq_start,
    .next   = packet_seq_next,
    .stop   = packet_seq_stop,
    .show   = packet_seq_show,
};

static int packet_seq_open(struct inode *inode, struct file *file)
{
    return seq_open_net(inode, file, &packet_seq_ops,
                sizeof(struct seq_net_private));
}

static const struct file_operations packet_seq_fops = {
    .owner      = THIS_MODULE,
    .open       = packet_seq_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release_net,
};

#endif

static int __net_init packet_net_init(struct net *net)
{
    mutex_init(&net->packet.sklist_lock);
    INIT_HLIST_HEAD(&net->packet.sklist);

    if (!proc_net_fops_create(net, "packet", 0, &packet_seq_fops))
        return -ENOMEM;

    return 0;
}

static void __net_exit packet_net_exit(struct net *net)
{
    proc_net_remove(net, "packet");
}

static struct pernet_operations packet_net_ops = {
    .init = packet_net_init,
    .exit = packet_net_exit,
};


static void __exit packet_exit(void)
{
    unregister_netdevice_notifier(&packet_netdev_notifier);
    unregister_pernet_subsys(&packet_net_ops);
    sock_unregister(PF_PACKET);
    proto_unregister(&packet_proto);
}

static int __init packet_init(void)
{
    int rc = proto_register(&packet_proto, 0);

    if (rc != 0)
        goto out;

    sock_register(&packet_family_ops);
    register_pernet_subsys(&packet_net_ops);
    register_netdevice_notifier(&packet_netdev_notifier);
out:
    return rc;
}

module_init(packet_init);
module_exit(packet_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS_NETPROTO(PF_PACKET);