/*
 * 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, <waltje@uWalt.NL.Mugnet.ORG>
 *              Alan Cox, <gw4pts@gw4pts.ampr.org>
 *
 * 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, <lokec@ccs.neu.edu>
 *
 *
 *              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>
#include <linux/percpu.h>
#ifdef CONFIG_INET
#include <net/inet_common.h>
#endif
#include <linux/bpf.h>

#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];
};

union tpacket_uhdr {
        struct tpacket_hdr  *h1;
        struct tpacket2_hdr *h2;
        struct tpacket3_hdr *h3;
        void *raw;
};

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 int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
                       struct packet_type *pt, struct net_device *orig_dev);

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 {
        union {
                struct sockaddr_pkt pkt;
                union {
                        /* Trick: alias skb original length with
                         * ll.sll_family and ll.protocol in order
                         * to save room.
                         */
                        unsigned int origlen;
                        struct sockaddr_ll ll;
                };
        } sa;
};

#define vio_le() virtio_legacy_is_little_endian()

#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);

static int packet_direct_xmit(struct sk_buff *skb)
{
        struct net_device *dev = skb->dev;
        netdev_features_t features;
        struct netdev_queue *txq;
        int ret = NETDEV_TX_BUSY;

        if (unlikely(!netif_running(dev) ||
                     !netif_carrier_ok(dev)))
                goto drop;

        features = netif_skb_features(skb);
        if (skb_needs_linearize(skb, features) &&
            __skb_linearize(skb))
                goto drop;

        txq = skb_get_tx_queue(dev, skb);

        local_bh_disable();

        HARD_TX_LOCK(dev, txq, smp_processor_id());
        if (!netif_xmit_frozen_or_drv_stopped(txq))
                ret = netdev_start_xmit(skb, dev, txq, false);
        HARD_TX_UNLOCK(dev, txq);

        local_bh_enable();

        if (!dev_xmit_complete(ret))
                kfree_skb(skb);

        return ret;
drop:
        atomic_long_inc(&dev->tx_dropped);
        kfree_skb(skb);
        return NET_XMIT_DROP;
}

static struct net_device *packet_cached_dev_get(struct packet_sock *po)
{
        struct net_device *dev;

        rcu_read_lock();
        dev = rcu_dereference(po->cached_dev);
        if (likely(dev))
                dev_hold(dev);
        rcu_read_unlock();

        return dev;
}

static void packet_cached_dev_assign(struct packet_sock *po,
                                     struct net_device *dev)
{
        rcu_assign_pointer(po->cached_dev, dev);
}

static void packet_cached_dev_reset(struct packet_sock *po)
{
        RCU_INIT_POINTER(po->cached_dev, NULL);
}

static bool packet_use_direct_xmit(const struct packet_sock *po)
{
        return po->xmit == packet_direct_xmit;
}

static u16 __packet_pick_tx_queue(struct net_device *dev, struct sk_buff *skb)
{
        return (u16) raw_smp_processor_id() % dev->real_num_tx_queues;
}

static void packet_pick_tx_queue(struct net_device *dev, struct sk_buff *skb)
{
        const struct net_device_ops *ops = dev->netdev_ops;
        u16 queue_index;

        if (ops->ndo_select_queue) {
                queue_index = ops->ndo_select_queue(dev, skb, NULL,
                                                    __packet_pick_tx_queue);
                queue_index = netdev_cap_txqueue(dev, queue_index);
        } else {
                queue_index = __packet_pick_tx_queue(dev, skb);
        }

        skb_set_queue_mapping(skb, queue_index);
}

/* 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 struct page * __pure 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 tpacket_uhdr 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 tpacket_uhdr 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 __u32 tpacket_get_timestamp(struct sk_buff *skb, struct timespec *ts,
                                   unsigned int flags)
{
        struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);

        if (shhwtstamps &&
            (flags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
            ktime_to_timespec_cond(shhwtstamps->hwtstamp, ts))
                return TP_STATUS_TS_RAW_HARDWARE;

        if (ktime_to_timespec_cond(skb->tstamp, ts))
                return TP_STATUS_TS_SOFTWARE;

        return 0;
}

static __u32 __packet_set_timestamp(struct packet_sock *po, void *frame,
                                    struct sk_buff *skb)
{
        union tpacket_uhdr h;
        struct timespec ts;
        __u32 ts_status;

        if (!(ts_status = tpacket_get_timestamp(skb, &ts, po->tp_tstamp)))
                return 0;

        h.raw = frame;
        switch (po->tp_version) {
        case TPACKET_V1:
                h.h1->tp_sec = ts.tv_sec;
                h.h1->tp_usec = ts.tv_nsec / NSEC_PER_USEC;
                break;
        case TPACKET_V2:
                h.h2->tp_sec = ts.tv_sec;
                h.h2->tp_nsec = ts.tv_nsec;
                break;
        case TPACKET_V3:
        default:
                WARN(1, "TPACKET version not supported.\n");
                BUG();
        }

        /* one flush is safe, as both fields always lie on the same cacheline */
        flush_dcache_page(pgv_to_page(&h.h1->tp_sec));
        smp_wmb();

        return ts_status;
}

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 tpacket_uhdr 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,
                struct sk_buff_head *rb_queue)
{
        struct tpacket_kbdq_core *pkc;

        pkc = GET_PBDQC_FROM_RB(&po->rx_ring);

        spin_lock_bh(&rb_queue->lock);
        pkc->delete_blk_timer = 1;
        spin_unlock_bh(&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)
{
        struct tpacket_kbdq_core *pkc;

        pkc = GET_PBDQC_FROM_RB(&po->rx_ring);
        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)
{
        struct tpacket_kbdq_core *p1 = GET_PBDQC_FROM_RB(rb);
        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.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;

        p1->max_frame_len = p1->kblk_size - BLK_PLUS_PRIV(p1->blk_sizeof_priv);
        prb_init_ft_ops(p1, req_u);
        prb_setup_retire_blk_timer(po);
        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 = GET_PBDQC_FROM_RB(&po->rx_ring);
        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) {
                        if (!BLOCK_NUM_PKTS(pbd)) {
                                /* An empty block. Just refresh the timer. */
                                goto refresh_timer;
                        }
                        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;
        struct sock *sk = &po->sk;

        if (po->stats.stats3.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.
                 *
                 * It shouldn't really happen as we don't close empty
                 * blocks. See prb_retire_rx_blk_timer_expired().
                 */
                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);

        sk->sk_data_ready(sk);

        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();

        /* 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();
}

/*
 * 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.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;
        }
}

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_hash(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 (skb_vlan_tag_present(pkc->skb)) {

                ppd->hv1.tp_vlan_tci = skb_vlan_tag_get(pkc->skb);
                ppd->hv1.tp_vlan_tpid = ntohs(pkc->skb->vlan_proto);
                ppd->tp_status = TP_STATUS_VLAN_VALID | TP_STATUS_VLAN_TPID_VALID;
        } else {
                ppd->hv1.tp_vlan_tci = 0;
                ppd->hv1.tp_vlan_tpid = 0;
                ppd->tp_status = TP_STATUS_AVAILABLE;
        }
}

static void prb_run_all_ft_ops(struct tpacket_kbdq_core *pkc,
                        struct tpacket3_hdr *ppd)
{
        ppd->hv1.tp_padding = 0;
        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 idx,
                                     int status)
{
        struct tpacket_kbdq_core *pkc  = GET_PBDQC_FROM_RB(rb);
        struct tpacket_block_desc *pbd = GET_PBLOCK_DESC(pkc, idx);

        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_inc_pending(struct packet_ring_buffer *rb)
{
        this_cpu_inc(*rb->pending_refcnt);
}

static void packet_dec_pending(struct packet_ring_buffer *rb)
{
        this_cpu_dec(*rb->pending_refcnt);
}

static unsigned int packet_read_pending(const struct packet_ring_buffer *rb)
{
        unsigned int refcnt = 0;
        int cpu;

        /* We don't use pending refcount in rx_ring. */
        if (rb->pending_refcnt == NULL)
                return 0;

        for_each_possible_cpu(cpu)
                refcnt += *per_cpu_ptr(rb->pending_refcnt, cpu);

        return refcnt;
}

static int packet_alloc_pending(struct packet_sock *po)
{
        po->rx_ring.pending_refcnt = NULL;

        po->tx_ring.pending_refcnt = alloc_percpu(unsigned int);
        if (unlikely(po->tx_ring.pending_refcnt == NULL))
                return -ENOBUFS;

        return 0;
}

static void packet_free_pending(struct packet_sock *po)
{
        free_percpu(po->tx_ring.pending_refcnt);
}

#define ROOM_POW_OFF    2
#define ROOM_NONE       0x0
#define ROOM_LOW        0x1
#define ROOM_NORMAL     0x2

static bool __tpacket_has_room(struct packet_sock *po, int pow_off)
{
        int idx, len;

        len = po->rx_ring.frame_max + 1;
        idx = po->rx_ring.head;
        if (pow_off)
                idx += len >> pow_off;
        if (idx >= len)
                idx -= len;
        return packet_lookup_frame(po, &po->rx_ring, idx, TP_STATUS_KERNEL);
}

static bool __tpacket_v3_has_room(struct packet_sock *po, int pow_off)
{
        int idx, len;

        len = po->rx_ring.prb_bdqc.knum_blocks;
        idx = po->rx_ring.prb_bdqc.kactive_blk_num;
        if (pow_off)
                idx += len >> pow_off;
        if (idx >= len)
                idx -= len;
        return prb_lookup_block(po, &po->rx_ring, idx, TP_STATUS_KERNEL);
}

static int __packet_rcv_has_room(struct packet_sock *po, struct sk_buff *skb)
{
        struct sock *sk = &po->sk;
        int ret = ROOM_NONE;

        if (po->prot_hook.func != tpacket_rcv) {
                int avail = sk->sk_rcvbuf - atomic_read(&sk->sk_rmem_alloc)
                                          - (skb ? skb->truesize : 0);
                if (avail > (sk->sk_rcvbuf >> ROOM_POW_OFF))
                        return ROOM_NORMAL;
                else if (avail > 0)
                        return ROOM_LOW;
                else
                        return ROOM_NONE;
        }

        if (po->tp_version == TPACKET_V3) {
                if (__tpacket_v3_has_room(po, ROOM_POW_OFF))
                        ret = ROOM_NORMAL;
                else if (__tpacket_v3_has_room(po, 0))
                        ret = ROOM_LOW;
        } else {
                if (__tpacket_has_room(po, ROOM_POW_OFF))
                        ret = ROOM_NORMAL;
                else if (__tpacket_has_room(po, 0))
                        ret = ROOM_LOW;
        }

        return ret;
}

static int packet_rcv_has_room(struct packet_sock *po, struct sk_buff *skb)
{
        int ret;
        bool has_room;

        spin_lock_bh(&po->sk.sk_receive_queue.lock);
        ret = __packet_rcv_has_room(po, skb);
        has_room = ret == ROOM_NORMAL;
        if (po->pressure == has_room)
                po->pressure = !has_room;
        spin_unlock_bh(&po->sk.sk_receive_queue.lock);

        return ret;
}

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 bool fanout_flow_is_huge(struct packet_sock *po, struct sk_buff *skb)
{
        u32 rxhash;
        int i, count = 0;

        rxhash = skb_get_hash(skb);
        for (i = 0; i < ROLLOVER_HLEN; i++)
                if (po->rollover->history[i] == rxhash)
                        count++;

        po->rollover->history[prandom_u32() % ROLLOVER_HLEN] = rxhash;
        return count > (ROLLOVER_HLEN >> 1);
}

static unsigned int fanout_demux_hash(struct packet_fanout *f,
                                      struct sk_buff *skb,
                                      unsigned int num)
{
        return reciprocal_scale(skb_get_hash(skb), num);
}

static unsigned int fanout_demux_lb(struct packet_fanout *f,
                                    struct sk_buff *skb,
                                    unsigned int num)
{
        unsigned int val = atomic_inc_return(&f->rr_cur);

        return val % num;
}

static unsigned int fanout_demux_cpu(struct packet_fanout *f,
                                     struct sk_buff *skb,
                                     unsigned int num)
{
        return smp_processor_id() % num;
}

static unsigned int fanout_demux_rnd(struct packet_fanout *f,
                                     struct sk_buff *skb,
                                     unsigned int num)
{
        return prandom_u32_max(num);
}

static unsigned int fanout_demux_rollover(struct packet_fanout *f,
                                          struct sk_buff *skb,
                                          unsigned int idx, bool try_self,
                                          unsigned int num)
{
        struct packet_sock *po, *po_next, *po_skip = NULL;
        unsigned int i, j, room = ROOM_NONE;

        po = pkt_sk(f->arr[idx]);

        if (try_self) {
                room = packet_rcv_has_room(po, skb);
                if (room == ROOM_NORMAL ||
                    (room == ROOM_LOW && !fanout_flow_is_huge(po, skb)))
                        return idx;
                po_skip = po;
        }

        i = j = min_t(int, po->rollover->sock, num - 1);
        do {
                po_next = pkt_sk(f->arr[i]);
                if (po_next != po_skip && !po_next->pressure &&
                    packet_rcv_has_room(po_next, skb) == ROOM_NORMAL) {
                        if (i != j)
                                po->rollover->sock = i;
                        atomic_long_inc(&po->rollover->num);
                        if (room == ROOM_LOW)
                                atomic_long_inc(&po->rollover->num_huge);
                        return i;
                }

                if (++i == num)
                        i = 0;
        } while (i != j);

        atomic_long_inc(&po->rollover->num_failed);
        return idx;
}

static unsigned int fanout_demux_qm(struct packet_fanout *f,
                                    struct sk_buff *skb,
                                    unsigned int num)
{
        return skb_get_queue_mapping(skb) % num;
}

static unsigned int fanout_demux_bpf(struct packet_fanout *f,
                                     struct sk_buff *skb,
                                     unsigned int num)
{
        struct bpf_prog *prog;
        unsigned int ret = 0;

        rcu_read_lock();
        prog = rcu_dereference(f->bpf_prog);
        if (prog)
                ret = bpf_prog_run_clear_cb(prog, skb) % num;
        rcu_read_unlock();

        return ret;
}

static bool fanout_has_flag(struct packet_fanout *f, u16 flag)
{
        return f->flags & (flag >> 8);
}

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 = READ_ONCE(f->num_members);
        struct net *net = read_pnet(&f->net);
        struct packet_sock *po;
        unsigned int idx;

        if (!net_eq(dev_net(dev), net) || !num) {
                kfree_skb(skb);
                return 0;
        }

        if (fanout_has_flag(f, PACKET_FANOUT_FLAG_DEFRAG)) {
                skb = ip_check_defrag(net, skb, IP_DEFRAG_AF_PACKET);
                if (!skb)
                        return 0;
        }
        switch (f->type) {
        case PACKET_FANOUT_HASH:
        default:
                idx = fanout_demux_hash(f, skb, num);
                break;
        case PACKET_FANOUT_LB:
                idx = fanout_demux_lb(f, skb, num);
                break;
        case PACKET_FANOUT_CPU:
                idx = fanout_demux_cpu(f, skb, num);
                break;
        case PACKET_FANOUT_RND:
                idx = fanout_demux_rnd(f, skb, num);
                break;
        case PACKET_FANOUT_QM:
                idx = fanout_demux_qm(f, skb, num);
                break;
        case PACKET_FANOUT_ROLLOVER:
                idx = fanout_demux_rollover(f, skb, 0, false, num);
                break;
        case PACKET_FANOUT_CBPF:
        case PACKET_FANOUT_EBPF:
                idx = fanout_demux_bpf(f, skb, num);
                break;
        }

        if (fanout_has_flag(f, PACKET_FANOUT_FLAG_ROLLOVER))
                idx = fanout_demux_rollover(f, skb, idx, true, num);

        po = pkt_sk(f->arr[idx]);
        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 (sk->sk_family != PF_PACKET)
                return false;

        return ptype->af_packet_priv == pkt_sk(sk)->fanout;
}

static void fanout_init_data(struct packet_fanout *f)
{
        switch (f->type) {
        case PACKET_FANOUT_LB:
                atomic_set(&f->rr_cur, 0);
                break;
        case PACKET_FANOUT_CBPF:
        case PACKET_FANOUT_EBPF:
                RCU_INIT_POINTER(f->bpf_prog, NULL);
                break;
        }
}

static void __fanout_set_data_bpf(struct packet_fanout *f, struct bpf_prog *new)
{
        struct bpf_prog *old;

        spin_lock(&f->lock);
        old = rcu_dereference_protected(f->bpf_prog, lockdep_is_held(&f->lock));
        rcu_assign_pointer(f->bpf_prog, new);
        spin_unlock(&f->lock);

        if (old) {
                synchronize_net();
                bpf_prog_destroy(old);
        }
}

static int fanout_set_data_cbpf(struct packet_sock *po, char __user *data,
                                unsigned int len)
{
        struct bpf_prog *new;
        struct sock_fprog fprog;
        int ret;

        if (sock_flag(&po->sk, SOCK_FILTER_LOCKED))
                return -EPERM;
        if (len != sizeof(fprog))
                return -EINVAL;
        if (copy_from_user(&fprog, data, len))
                return -EFAULT;

        ret = bpf_prog_create_from_user(&new, &fprog, NULL, false);
        if (ret)
                return ret;

        __fanout_set_data_bpf(po->fanout, new);
        return 0;
}

static int fanout_set_data_ebpf(struct packet_sock *po, char __user *data,
                                unsigned int len)
{
        struct bpf_prog *new;
        u32 fd;

        if (sock_flag(&po->sk, SOCK_FILTER_LOCKED))
                return -EPERM;
        if (len != sizeof(fd))
                return -EINVAL;
        if (copy_from_user(&fd, data, len))
                return -EFAULT;

        new = bpf_prog_get(fd);
        if (IS_ERR(new))
                return PTR_ERR(new);
        if (new->type != BPF_PROG_TYPE_SOCKET_FILTER) {
                bpf_prog_put(new);
                return -EINVAL;
        }

        __fanout_set_data_bpf(po->fanout, new);
        return 0;
}

static int fanout_set_data(struct packet_sock *po, char __user *data,
                           unsigned int len)
{
        switch (po->fanout->type) {
        case PACKET_FANOUT_CBPF:
                return fanout_set_data_cbpf(po, data, len);
        case PACKET_FANOUT_EBPF:
                return fanout_set_data_ebpf(po, data, len);
        default:
                return -EINVAL;
        };
}

static void fanout_release_data(struct packet_fanout *f)
{
        switch (f->type) {
        case PACKET_FANOUT_CBPF:
        case PACKET_FANOUT_EBPF:
                __fanout_set_data_bpf(f, NULL);
        };
}

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 flags = type_flags >> 8;
        int err;

        switch (type) {
        case PACKET_FANOUT_ROLLOVER:
                if (type_flags & PACKET_FANOUT_FLAG_ROLLOVER)
                        return -EINVAL;
        case PACKET_FANOUT_HASH:
        case PACKET_FANOUT_LB:
        case PACKET_FANOUT_CPU:
        case PACKET_FANOUT_RND:
        case PACKET_FANOUT_QM:
        case PACKET_FANOUT_CBPF:
        case PACKET_FANOUT_EBPF:
                break;
        default:
                return -EINVAL;
        }

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

        if (po->fanout)
                return -EALREADY;

        if (type == PACKET_FANOUT_ROLLOVER ||
            (type_flags & PACKET_FANOUT_FLAG_ROLLOVER)) {
                po->rollover = kzalloc(sizeof(*po->rollover), GFP_KERNEL);
                if (!po->rollover)
                        return -ENOMEM;
                atomic_long_set(&po->rollover->num, 0);
                atomic_long_set(&po->rollover->num_huge, 0);
                atomic_long_set(&po->rollover->num_failed, 0);
        }

        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->flags != flags)
                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->flags = flags;
                INIT_LIST_HEAD(&match->list);
                spin_lock_init(&match->lock);
                atomic_set(&match->sk_ref, 0);
                fanout_init_data(match);
                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);
        if (err) {
                kfree(po->rollover);
                po->rollover = NULL;
        }
        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);
                fanout_release_data(f);
                kfree(f);
        }
        mutex_unlock(&fanout_mutex);

        if (po->rollover)
                kfree_rcu(po->rollover, rcu);
}

static bool packet_extra_vlan_len_allowed(const struct net_device *dev,
                                          struct sk_buff *skb)
{
        /* Earlier code assumed this would be a VLAN pkt, double-check
         * this now that we have the actual packet in hand. We can only
         * do this check on Ethernet devices.
         */
        if (unlikely(dev->type != ARPHRD_ETHER))
                return false;

        skb_reset_mac_header(skb);
        return likely(eth_hdr(skb)->h_proto == htons(ETH_P_8021Q));
}

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 socket *sock, struct msghdr *msg,
                               size_t len)
{
        struct sock *sk = sock->sk;
        DECLARE_SOCKADDR(struct sockaddr_pkt *, saddr, 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_from_msg(skb_put(skb, len), msg, len);
                if (err)
                        goto out_free;
                goto retry;
        }

        if (len > (dev->mtu + dev->hard_header_len + extra_len) &&
            !packet_extra_vlan_len_allowed(dev, skb)) {
                err = -EMSGSIZE;
                goto out_unlock;
        }

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

        sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);

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

        skb_probe_transport_header(skb, 0);

        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(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 = bpf_prog_run_clear_cb(filter->prog, 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;
        }

        sock_skb_cb_check_size(sizeof(*PACKET_SKB_CB(skb)) + MAX_ADDR_LEN - 8);

        sll = &PACKET_SKB_CB(skb)->sa.ll;
        sll->sll_hatype = dev->type;
        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);

        /* sll->sll_family and sll->sll_protocol are set in packet_recvmsg().
         * Use their space for storing the original skb length.
         */
        PACKET_SKB_CB(skb)->sa.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.stats1.tp_packets++;
        sock_skb_set_dropcount(sk, skb);
        __skb_queue_tail(&sk->sk_receive_queue, skb);
        spin_unlock(&sk->sk_receive_queue.lock);
        sk->sk_data_ready(sk);
        return 0;

drop_n_acct:
        spin_lock(&sk->sk_receive_queue.lock);
        po->stats.stats1.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 tpacket_uhdr 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 timespec ts;
        __u32 ts_status;

        /* struct tpacket{2,3}_hdr is aligned to a multiple of TPACKET_ALIGNMENT.
         * We may add members to them until current aligned size without forcing
         * userspace to call getsockopt(..., PACKET_HDRLEN, ...).
         */
        BUILD_BUG_ON(TPACKET_ALIGN(sizeof(*h.h2)) != 32);
        BUILD_BUG_ON(TPACKET_ALIGN(sizeof(*h.h3)) != 48);

        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));
                }
        }

        snaplen = skb->len;

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

        if (skb->ip_summed == CHECKSUM_PARTIAL)
                status |= TP_STATUS_CSUMNOTREADY;
        else if (skb->pkt_type != PACKET_OUTGOING &&
                 (skb->ip_summed == CHECKSUM_COMPLETE ||
                  skb_csum_unnecessary(skb)))
                status |= TP_STATUS_CSUM_VALID;

        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;
                }
        } else if (unlikely(macoff + snaplen >
                            GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len)) {
                u32 nval;

                nval = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len - macoff;
                pr_err_once("tpacket_rcv: packet too big, clamped from %u to %u. macoff=%u\n",
                            snaplen, nval, macoff);
                snaplen = nval;
                if (unlikely((int)snaplen < 0)) {
                        snaplen = 0;
                        macoff = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len;
                }
        }
        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.stats1.tp_drops)
                        status |= TP_STATUS_LOSING;
        }
        po->stats.stats1.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);

        if (!(ts_status = tpacket_get_timestamp(skb, &ts, po->tp_tstamp)))
                getnstimeofday(&ts);

        status |= ts_status;

        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;
                h.h1->tp_sec = ts.tv_sec;
                h.h1->tp_usec = ts.tv_nsec / NSEC_PER_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;
                h.h2->tp_sec = ts.tv_sec;
                h.h2->tp_nsec = ts.tv_nsec;
                if (skb_vlan_tag_present(skb)) {
                        h.h2->tp_vlan_tci = skb_vlan_tag_get(skb);
                        h.h2->tp_vlan_tpid = ntohs(skb->vlan_proto);
                        status |= TP_STATUS_VLAN_VALID | TP_STATUS_VLAN_TPID_VALID;
                } else {
                        h.h2->tp_vlan_tci = 0;
                        h.h2->tp_vlan_tpid = 0;
                }
                memset(h.h2->tp_padding, 0, sizeof(h.h2->tp_padding));
                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;
                h.h3->tp_sec  = ts.tv_sec;
                h.h3->tp_nsec = ts.tv_nsec;
                memset(h.h3->tp_padding, 0, sizeof(h.h3->tp_padding));
                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
        if (po->tp_version <= TPACKET_V2) {
                u8 *start, *end;

                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);
                sk->sk_data_ready(sk);
        } else {
                prb_clear_blk_fill_status(&po->rx_ring);
        }

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.stats1.tp_drops++;
        spin_unlock(&sk->sk_receive_queue.lock);

        sk->sk_data_ready(sk);
        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);

        if (likely(po->tx_ring.pg_vec)) {
                void *ph;
                __u32 ts;

                ph = skb_shinfo(skb)->destructor_arg;
                packet_dec_pending(&po->tx_ring);

                ts = __packet_set_timestamp(po, ph, skb);
                __packet_set_status(po, ph, TP_STATUS_AVAILABLE | ts);
        }

        sock_wfree(skb);
}

static bool ll_header_truncated(const struct net_device *dev, int len)
{
        /* net device doesn't like empty head */
        if (unlikely(len < dev->hard_header_len)) {
                net_warn_ratelimited("%s: packet size is too short (%d < %d)\n",
                                     current->comm, len, dev->hard_header_len);
                return true;
        }

        return false;
}

static void tpacket_set_protocol(const struct net_device *dev,
                                 struct sk_buff *skb)
{
        if (dev->type == ARPHRD_ETHER) {
                skb_reset_mac_header(skb);
                skb->protocol = eth_hdr(skb)->h_proto;
        }
}

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 tpacket_uhdr 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;
        sock_tx_timestamp(&po->sk, &skb_shinfo(skb)->tx_flags);
        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);

        if (unlikely(po->tp_tx_has_off)) {
                int off_min, off_max, off;
                off_min = po->tp_hdrlen - sizeof(struct sockaddr_ll);
                off_max = po->tx_ring.frame_size - tp_len;
                if (sock->type == SOCK_DGRAM) {
                        switch (po->tp_version) {
                        case TPACKET_V2:
                                off = ph.h2->tp_net;
                                break;
                        default:
                                off = ph.h1->tp_net;
                                break;
                        }
                } else {
                        switch (po->tp_version) {
                        case TPACKET_V2:
                                off = ph.h2->tp_mac;
                                break;
                        default:
                                off = ph.h1->tp_mac;
                                break;
                        }
                }
                if (unlikely((off < off_min) || (off_max < off)))
                        return -EINVAL;
                data = ph.raw + off;
        } else {
                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) {
                if (ll_header_truncated(dev, tp_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;
                if (!skb->protocol)
                        tpacket_set_protocol(dev, skb);

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

        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);
        }

        skb_probe_transport_header(skb, 0);

        return tp_len;
}

static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
{
        struct sk_buff *skb;
        struct net_device *dev;
        __be16 proto;
        int err, reserve = 0;
        void *ph;
        DECLARE_SOCKADDR(struct sockaddr_ll *, saddr, msg->msg_name);
        bool need_wait = !(msg->msg_flags & MSG_DONTWAIT);
        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);

        if (likely(saddr == NULL)) {
                dev     = packet_cached_dev_get(po);
                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);
        }

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

        if (po->sk.sk_socket->type == SOCK_RAW)
                reserve = dev->hard_header_len;
        size_max = po->tx_ring.frame_size
                - (po->tp_hdrlen - sizeof(struct sockaddr_ll));

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

        do {
                ph = packet_current_frame(po, &po->tx_ring,
                                          TP_STATUS_SEND_REQUEST);
                if (unlikely(ph == NULL)) {
                        if (need_wait && need_resched())
                                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),
                                !need_wait, &err);

                if (unlikely(skb == NULL)) {
                        /* we assume the socket was initially writeable ... */
                        if (likely(len_sum > 0))
                                err = len_sum;
                        goto out_status;
                }
                tp_len = tpacket_fill_skb(po, skb, ph, dev, size_max, proto,
                                          addr, hlen);
                if (likely(tp_len >= 0) &&
                    tp_len > dev->mtu + reserve &&
                    !packet_extra_vlan_len_allowed(dev, skb))
                        tp_len = -EMSGSIZE;

                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;
                        }
                }

                packet_pick_tx_queue(dev, skb);

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

                status = TP_STATUS_SEND_REQUEST;
                err = po->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) ||
                /* Note: packet_read_pending() might be slow if we have
                 * to call it as it's per_cpu variable, but in fast-path
                 * we already short-circuit the loop with the first
                 * condition, and luckily don't have to go that path
                 * anyway.
                 */
                 (need_wait && packet_read_pending(&po->tx_ring))));

        err = len_sum;
        goto out_put;

out_status:
        __packet_set_status(po, ph, status);
        kfree_skb(skb);
out_put:
        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, 0);
        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;
        DECLARE_SOCKADDR(struct sockaddr_ll *, saddr, msg->msg_name);
        struct sk_buff *skb;
        struct net_device *dev;
        __be16 proto;
        unsigned char *addr;
        int err, reserve = 0;
        struct sockcm_cookie sockc;
        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;
        ssize_t n;

        /*
         *      Get and verify the address.
         */

        if (likely(saddr == NULL)) {
                dev     = packet_cached_dev_get(po);
                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);
        }

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

        sockc.mark = sk->sk_mark;
        if (msg->msg_controllen) {
                err = sock_cmsg_send(sk, msg, &sockc);
                if (unlikely(err))
                        goto out_unlock;
        }

        if (sock->type == SOCK_RAW)
                reserve = dev->hard_header_len;
        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 = -EFAULT;
                n = copy_from_iter(&vnet_hdr, vnet_hdr_len, &msg->msg_iter);
                if (n != vnet_hdr_len)
                        goto out_unlock;

                if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
                    (__virtio16_to_cpu(vio_le(), vnet_hdr.csum_start) +
                     __virtio16_to_cpu(vio_le(), vnet_hdr.csum_offset) + 2 >
                      __virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len)))
                        vnet_hdr.hdr_len = __cpu_to_virtio16(vio_le(),
                                 __virtio16_to_cpu(vio_le(), vnet_hdr.csum_start) +
                                __virtio16_to_cpu(vio_le(), vnet_hdr.csum_offset) + 2);

                err = -EINVAL;
                if (__virtio16_to_cpu(vio_le(), 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,
                               __virtio16_to_cpu(vio_le(), 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);
                if (unlikely(offset < 0))
                        goto out_free;
        } else {
                if (ll_header_truncated(dev, len))
                        goto out_free;
        }

        /* Returns -EFAULT on error */
        err = skb_copy_datagram_from_iter(skb, offset, &msg->msg_iter, len);
        if (err)
                goto out_free;

        sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);

        if (!gso_type && (len > dev->mtu + reserve + extra_len) &&
            !packet_extra_vlan_len_allowed(dev, skb)) {
                err = -EMSGSIZE;
                goto out_free;
        }

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

        packet_pick_tx_queue(dev, skb);

        if (po->has_vnet_hdr) {
                if (vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
                        u16 s = __virtio16_to_cpu(vio_le(), vnet_hdr.csum_start);
                        u16 o = __virtio16_to_cpu(vio_le(), vnet_hdr.csum_offset);
                        if (!skb_partial_csum_set(skb, s, o)) {
                                err = -EINVAL;
                                goto out_free;
                        }
                }

                skb_shinfo(skb)->gso_size =
                        __virtio16_to_cpu(vio_le(), 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;
        }

        skb_probe_transport_header(skb, reserve);

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

        err = po->xmit(skb);
        if (err > 0 && (err = net_xmit_errno(err)) != 0)
                goto out_unlock;

        dev_put(dev);

        return len;

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

static int packet_sendmsg(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);
        packet_cached_dev_reset(po);

        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);

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

        if (po->tx_ring.pg_vec) {
                memset(&req_u, 0, sizeof(req_u));
                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);
        packet_free_pending(po);
        sk_refcnt_debug_release(sk);

        sock_put(sk);
        return 0;
}

/*
 *      Attach a packet hook.
 */

static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
                          __be16 proto)
{
        struct packet_sock *po = pkt_sk(sk);
        struct net_device *dev_curr;
        __be16 proto_curr;
        bool need_rehook;
        struct net_device *dev = NULL;
        int ret = 0;
        bool unlisted = false;

        if (po->fanout)
                return -EINVAL;

        lock_sock(sk);
        spin_lock(&po->bind_lock);
        rcu_read_lock();

        if (name) {
                dev = dev_get_by_name_rcu(sock_net(sk), name);
                if (!dev) {
                        ret = -ENODEV;
                        goto out_unlock;
                }
        } else if (ifindex) {
                dev = dev_get_by_index_rcu(sock_net(sk), ifindex);
                if (!dev) {
                        ret = -ENODEV;
                        goto out_unlock;
                }
        }

        if (dev)
                dev_hold(dev);

        proto_curr = po->prot_hook.type;
        dev_curr = po->prot_hook.dev;

        need_rehook = proto_curr != proto || dev_curr != dev;

        if (need_rehook) {
                if (po->running) {
                        rcu_read_unlock();
                        __unregister_prot_hook(sk, true);
                        rcu_read_lock();
                        dev_curr = po->prot_hook.dev;
                        if (dev)
                                unlisted = !dev_get_by_index_rcu(sock_net(sk),
                                                                 dev->ifindex);
                }

                po->num = proto;
                po->prot_hook.type = proto;

                if (unlikely(unlisted)) {
                        dev_put(dev);
                        po->prot_hook.dev = NULL;
                        po->ifindex = -1;
                        packet_cached_dev_reset(po);
                } else {
                        po->prot_hook.dev = dev;
                        po->ifindex = dev ? dev->ifindex : 0;
                        packet_cached_dev_assign(po, dev);
                }
        }
        if (dev_curr)
                dev_put(dev_curr);

        if (proto == 0 || !need_rehook)
                goto out_unlock;

        if (!unlisted && (!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:
        rcu_read_unlock();
        spin_unlock(&po->bind_lock);
        release_sock(sk);
        return ret;
}