[deliverable/linux.git] / net / core / netpoll.c

/*
 * Common framework for low-level network console, dump, and debugger code
 *
 * Sep 8 2003  Matt Mackall <mpm@selenic.com>
 *
 * based on the netconsole code from:
 *
 * Copyright (C) 2001  Ingo Molnar <mingo@redhat.com>
 * Copyright (C) 2002  Red Hat, Inc.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/moduleparam.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/string.h>
#include <linux/if_arp.h>
#include <linux/inetdevice.h>
#include <linux/inet.h>
#include <linux/interrupt.h>
#include <linux/netpoll.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/if_vlan.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <asm/unaligned.h>
#include <trace/events/napi.h>

/*
 * We maintain a small pool of fully-sized skbs, to make sure the
 * message gets out even in extreme OOM situations.
 */

#define MAX_UDP_CHUNK 1460
#define MAX_SKBS 32

static struct sk_buff_head skb_pool;

static atomic_t trapped;

#define USEC_PER_POLL   50
#define NETPOLL_RX_ENABLED  1
#define NETPOLL_RX_DROP     2

#define MAX_SKB_SIZE                                                    \
        (sizeof(struct ethhdr) +                                        \
         sizeof(struct iphdr) +                                         \
         sizeof(struct udphdr) +                                        \
         MAX_UDP_CHUNK)

static void zap_completion_queue(void);
static void netpoll_arp_reply(struct sk_buff *skb, struct netpoll_info *npinfo);

static unsigned int carrier_timeout = 4;
module_param(carrier_timeout, uint, 0644);

#define np_info(np, fmt, ...)                           \
        pr_info("%s: " fmt, np->name, ##__VA_ARGS__)
#define np_err(np, fmt, ...)                            \
        pr_err("%s: " fmt, np->name, ##__VA_ARGS__)
#define np_notice(np, fmt, ...)                         \
        pr_notice("%s: " fmt, np->name, ##__VA_ARGS__)

static void queue_process(struct work_struct *work)
{
        struct netpoll_info *npinfo =
                container_of(work, struct netpoll_info, tx_work.work);
        struct sk_buff *skb;
        unsigned long flags;

        while ((skb = skb_dequeue(&npinfo->txq))) {
                struct net_device *dev = skb->dev;
                const struct net_device_ops *ops = dev->netdev_ops;
                struct netdev_queue *txq;

                if (!netif_device_present(dev) || !netif_running(dev)) {
                        __kfree_skb(skb);
                        continue;
                }

                txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));

                local_irq_save(flags);
                __netif_tx_lock(txq, smp_processor_id());
                if (netif_xmit_frozen_or_stopped(txq) ||
                    ops->ndo_start_xmit(skb, dev) != NETDEV_TX_OK) {
                        skb_queue_head(&npinfo->txq, skb);
                        __netif_tx_unlock(txq);
                        local_irq_restore(flags);

                        schedule_delayed_work(&npinfo->tx_work, HZ/10);
                        return;
                }
                __netif_tx_unlock(txq);
                local_irq_restore(flags);
        }
}

static __sum16 checksum_udp(struct sk_buff *skb, struct udphdr *uh,
                            unsigned short ulen, __be32 saddr, __be32 daddr)
{
        __wsum psum;

        if (uh->check == 0 || skb_csum_unnecessary(skb))
                return 0;

        psum = csum_tcpudp_nofold(saddr, daddr, ulen, IPPROTO_UDP, 0);

        if (skb->ip_summed == CHECKSUM_COMPLETE &&
            !csum_fold(csum_add(psum, skb->csum)))
                return 0;

        skb->csum = psum;

        return __skb_checksum_complete(skb);
}

/*
 * Check whether delayed processing was scheduled for our NIC. If so,
 * we attempt to grab the poll lock and use ->poll() to pump the card.
 * If this fails, either we've recursed in ->poll() or it's already
 * running on another CPU.
 *
 * Note: we don't mask interrupts with this lock because we're using
 * trylock here and interrupts are already disabled in the softirq
 * case. Further, we test the poll_owner to avoid recursion on UP
 * systems where the lock doesn't exist.
 *
 * In cases where there is bi-directional communications, reading only
 * one message at a time can lead to packets being dropped by the
 * network adapter, forcing superfluous retries and possibly timeouts.
 * Thus, we set our budget to greater than 1.
 */
static int poll_one_napi(struct netpoll_info *npinfo,
                         struct napi_struct *napi, int budget)
{
        int work;

        /* net_rx_action's ->poll() invocations and our's are
         * synchronized by this test which is only made while
         * holding the napi->poll_lock.
         */
        if (!test_bit(NAPI_STATE_SCHED, &napi->state))
                return budget;

        npinfo->rx_flags |= NETPOLL_RX_DROP;
        atomic_inc(&trapped);
        set_bit(NAPI_STATE_NPSVC, &napi->state);

        work = napi->poll(napi, budget);
        trace_napi_poll(napi);

        clear_bit(NAPI_STATE_NPSVC, &napi->state);
        atomic_dec(&trapped);
        npinfo->rx_flags &= ~NETPOLL_RX_DROP;

        return budget - work;
}

static void poll_napi(struct net_device *dev)
{
        struct napi_struct *napi;
        int budget = 16;

        WARN_ON_ONCE(!irqs_disabled());

        list_for_each_entry(napi, &dev->napi_list, dev_list) {
                local_irq_enable();
                if (napi->poll_owner != smp_processor_id() &&
                    spin_trylock(&napi->poll_lock)) {
                        rcu_read_lock_bh();
                        budget = poll_one_napi(rcu_dereference_bh(dev->npinfo),
                                               napi, budget);
                        rcu_read_unlock_bh();
                        spin_unlock(&napi->poll_lock);

                        if (!budget) {
                                local_irq_disable();
                                break;
                        }
                }
                local_irq_disable();
        }
}

static void service_arp_queue(struct netpoll_info *npi)
{
        if (npi) {
                struct sk_buff *skb;

                while ((skb = skb_dequeue(&npi->arp_tx)))
                        netpoll_arp_reply(skb, npi);
        }
}

static void netpoll_poll_dev(struct net_device *dev)
{
        const struct net_device_ops *ops;
        struct netpoll_info *ni = rcu_dereference_bh(dev->npinfo);

        if (!dev || !netif_running(dev))
                return;

        ops = dev->netdev_ops;
        if (!ops->ndo_poll_controller)
                return;

        /* Process pending work on NIC */
        ops->ndo_poll_controller(dev);

        poll_napi(dev);

        if (dev->flags & IFF_SLAVE) {
                if (ni) {
                        struct net_device *bond_dev = dev->master;
                        struct sk_buff *skb;
                        struct netpoll_info *bond_ni = rcu_dereference_bh(bond_dev->npinfo);
                        while ((skb = skb_dequeue(&ni->arp_tx))) {
                                skb->dev = bond_dev;
                                skb_queue_tail(&bond_ni->arp_tx, skb);
                        }
                }
        }

        service_arp_queue(ni);

        zap_completion_queue();
}

static void refill_skbs(void)
{
        struct sk_buff *skb;
        unsigned long flags;

        spin_lock_irqsave(&skb_pool.lock, flags);
        while (skb_pool.qlen < MAX_SKBS) {
                skb = alloc_skb(MAX_SKB_SIZE, GFP_ATOMIC);
                if (!skb)
                        break;

                __skb_queue_tail(&skb_pool, skb);
        }
        spin_unlock_irqrestore(&skb_pool.lock, flags);
}

static void zap_completion_queue(void)
{
        unsigned long flags;
        struct softnet_data *sd = &get_cpu_var(softnet_data);

        if (sd->completion_queue) {
                struct sk_buff *clist;

                local_irq_save(flags);
                clist = sd->completion_queue;
                sd->completion_queue = NULL;
                local_irq_restore(flags);

                while (clist != NULL) {
                        struct sk_buff *skb = clist;
                        clist = clist->next;
                        if (skb->destructor) {
                                atomic_inc(&skb->users);
                                dev_kfree_skb_any(skb); /* put this one back */
                        } else {
                                __kfree_skb(skb);
                        }
                }
        }

        put_cpu_var(softnet_data);
}

static struct sk_buff *find_skb(struct netpoll *np, int len, int reserve)
{
        int count = 0;
        struct sk_buff *skb;

        zap_completion_queue();
        refill_skbs();
repeat:

        skb = alloc_skb(len, GFP_ATOMIC);
        if (!skb)
                skb = skb_dequeue(&skb_pool);

        if (!skb) {
                if (++count < 10) {
                        netpoll_poll_dev(np->dev);
                        goto repeat;
                }
                return NULL;
        }

        atomic_set(&skb->users, 1);
        skb_reserve(skb, reserve);
        return skb;
}

static int netpoll_owner_active(struct net_device *dev)
{
        struct napi_struct *napi;

        list_for_each_entry(napi, &dev->napi_list, dev_list) {
                if (napi->poll_owner == smp_processor_id())
                        return 1;
        }
        return 0;
}

/* call with IRQ disabled */
void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
                             struct net_device *dev)
{
        int status = NETDEV_TX_BUSY;
        unsigned long tries;
        const struct net_device_ops *ops = dev->netdev_ops;
        /* It is up to the caller to keep npinfo alive. */
        struct netpoll_info *npinfo;

        WARN_ON_ONCE(!irqs_disabled());

        npinfo = rcu_dereference_bh(np->dev->npinfo);
        if (!npinfo || !netif_running(dev) || !netif_device_present(dev)) {
                __kfree_skb(skb);
                return;
        }

        /* don't get messages out of order, and no recursion */
        if (skb_queue_len(&npinfo->txq) == 0 && !netpoll_owner_active(dev)) {
                struct netdev_queue *txq;

                txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));

                /* try until next clock tick */
                for (tries = jiffies_to_usecs(1)/USEC_PER_POLL;
                     tries > 0; --tries) {
                        if (__netif_tx_trylock(txq)) {
                                if (!netif_xmit_stopped(txq)) {
                                        if (vlan_tx_tag_present(skb) &&
                                            !(netif_skb_features(skb) & NETIF_F_HW_VLAN_TX)) {
                                                skb = __vlan_put_tag(skb, vlan_tx_tag_get(skb));
                                                if (unlikely(!skb))
                                                        break;
                                                skb->vlan_tci = 0;
                                        }

                                        status = ops->ndo_start_xmit(skb, dev);
                                        if (status == NETDEV_TX_OK)
                                                txq_trans_update(txq);
                                }
                                __netif_tx_unlock(txq);

                                if (status == NETDEV_TX_OK)
                                        break;

                        }

                        /* tickle device maybe there is some cleanup */
                        netpoll_poll_dev(np->dev);

                        udelay(USEC_PER_POLL);
                }

                WARN_ONCE(!irqs_disabled(),
                        "netpoll_send_skb_on_dev(): %s enabled interrupts in poll (%pF)\n",
                        dev->name, ops->ndo_start_xmit);

        }

        if (status != NETDEV_TX_OK) {
                skb_queue_tail(&npinfo->txq, skb);
                schedule_delayed_work(&npinfo->tx_work,0);
        }
}
EXPORT_SYMBOL(netpoll_send_skb_on_dev);

void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
{
        int total_len, ip_len, udp_len;
        struct sk_buff *skb;
        struct udphdr *udph;
        struct iphdr *iph;
        struct ethhdr *eth;

        udp_len = len + sizeof(*udph);
        ip_len = udp_len + sizeof(*iph);
        total_len = ip_len + LL_RESERVED_SPACE(np->dev);

        skb = find_skb(np, total_len + np->dev->needed_tailroom,
                       total_len - len);
        if (!skb)
                return;

        skb_copy_to_linear_data(skb, msg, len);
        skb_put(skb, len);

        skb_push(skb, sizeof(*udph));
        skb_reset_transport_header(skb);
        udph = udp_hdr(skb);
        udph->source = htons(np->local_port);
        udph->dest = htons(np->remote_port);
        udph->len = htons(udp_len);
        udph->check = 0;
        udph->check = csum_tcpudp_magic(np->local_ip,
                                        np->remote_ip,
                                        udp_len, IPPROTO_UDP,
                                        csum_partial(udph, udp_len, 0));
        if (udph->check == 0)
                udph->check = CSUM_MANGLED_0;

        skb_push(skb, sizeof(*iph));
        skb_reset_network_header(skb);
        iph = ip_hdr(skb);

        /* iph->version = 4; iph->ihl = 5; */
        put_unaligned(0x45, (unsigned char *)iph);
        iph->tos      = 0;
        put_unaligned(htons(ip_len), &(iph->tot_len));
        iph->id       = 0;
        iph->frag_off = 0;
        iph->ttl      = 64;
        iph->protocol = IPPROTO_UDP;
        iph->check    = 0;
        put_unaligned(np->local_ip, &(iph->saddr));
        put_unaligned(np->remote_ip, &(iph->daddr));
        iph->check    = ip_fast_csum((unsigned char *)iph, iph->ihl);

        eth = (struct ethhdr *) skb_push(skb, ETH_HLEN);
        skb_reset_mac_header(skb);
        skb->protocol = eth->h_proto = htons(ETH_P_IP);
        memcpy(eth->h_source, np->dev->dev_addr, ETH_ALEN);
        memcpy(eth->h_dest, np->remote_mac, ETH_ALEN);

        skb->dev = np->dev;

        netpoll_send_skb(np, skb);
}
EXPORT_SYMBOL(netpoll_send_udp);

static void netpoll_arp_reply(struct sk_buff *skb, struct netpoll_info *npinfo)
{
        struct arphdr *arp;
        unsigned char *arp_ptr;
        int size, type = ARPOP_REPLY, ptype = ETH_P_ARP;
        __be32 sip, tip;
        unsigned char *sha;
        struct sk_buff *send_skb;
        struct netpoll *np, *tmp;
        unsigned long flags;
        int hlen, tlen;
        int hits = 0;

        if (list_empty(&npinfo->rx_np))
                return;

        /* Before checking the packet, we do some early
           inspection whether this is interesting at all */
        spin_lock_irqsave(&npinfo->rx_lock, flags);
        list_for_each_entry_safe(np, tmp, &npinfo->rx_np, rx) {
                if (np->dev == skb->dev)
                        hits++;
        }
        spin_unlock_irqrestore(&npinfo->rx_lock, flags);

        /* No netpoll struct is using this dev */
        if (!hits)
                return;

        /* No arp on this interface */
        if (skb->dev->flags & IFF_NOARP)
                return;

        if (!pskb_may_pull(skb, arp_hdr_len(skb->dev)))
                return;

        skb_reset_network_header(skb);
        skb_reset_transport_header(skb);
        arp = arp_hdr(skb);

        if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
             arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
            arp->ar_pro != htons(ETH_P_IP) ||
            arp->ar_op != htons(ARPOP_REQUEST))
                return;

        arp_ptr = (unsigned char *)(arp+1);
        /* save the location of the src hw addr */
        sha = arp_ptr;
        arp_ptr += skb->dev->addr_len;
        memcpy(&sip, arp_ptr, 4);
        arp_ptr += 4;
        /* If we actually cared about dst hw addr,
           it would get copied here */
        arp_ptr += skb->dev->addr_len;
        memcpy(&tip, arp_ptr, 4);

        /* Should we ignore arp? */
        if (ipv4_is_loopback(tip) || ipv4_is_multicast(tip))
                return;

        size = arp_hdr_len(skb->dev);

        spin_lock_irqsave(&npinfo->rx_lock, flags);
        list_for_each_entry_safe(np, tmp, &npinfo->rx_np, rx) {
                if (tip != np->local_ip)
                        continue;

                hlen = LL_RESERVED_SPACE(np->dev);
                tlen = np->dev->needed_tailroom;
                send_skb = find_skb(np, size + hlen + tlen, hlen);
                if (!send_skb)
                        continue;

                skb_reset_network_header(send_skb);
                arp = (struct arphdr *) skb_put(send_skb, size);
                send_skb->dev = skb->dev;
                send_skb->protocol = htons(ETH_P_ARP);

                /* Fill the device header for the ARP frame */
                if (dev_hard_header(send_skb, skb->dev, ptype,
                                    sha, np->dev->dev_addr,
                                    send_skb->len) < 0) {
                        kfree_skb(send_skb);
                        continue;
                }

                /*
                 * Fill out the arp protocol part.
                 *
                 * we only support ethernet device type,
                 * which (according to RFC 1390) should
                 * always equal 1 (Ethernet).
                 */

                arp->ar_hrd = htons(np->dev->type);
                arp->ar_pro = htons(ETH_P_IP);
                arp->ar_hln = np->dev->addr_len;
                arp->ar_pln = 4;
                arp->ar_op = htons(type);

                arp_ptr = (unsigned char *)(arp + 1);
                memcpy(arp_ptr, np->dev->dev_addr, np->dev->addr_len);
                arp_ptr += np->dev->addr_len;
                memcpy(arp_ptr, &tip, 4);
                arp_ptr += 4;
                memcpy(arp_ptr, sha, np->dev->addr_len);
                arp_ptr += np->dev->addr_len;
                memcpy(arp_ptr, &sip, 4);

                netpoll_send_skb(np, send_skb);

                /* If there are several rx_hooks for the same address,
                   we're fine by sending a single reply */
                break;
        }
        spin_unlock_irqrestore(&npinfo->rx_lock, flags);
}

int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo)
{
        int proto, len, ulen;
        int hits = 0;
        const struct iphdr *iph;
        struct udphdr *uh;
        struct netpoll *np, *tmp;

        if (list_empty(&npinfo->rx_np))
                goto out;

        if (skb->dev->type != ARPHRD_ETHER)
                goto out;

        /* check if netpoll clients need ARP */
        if (skb->protocol == htons(ETH_P_ARP) &&
            atomic_read(&trapped)) {
                skb_queue_tail(&npinfo->arp_tx, skb);
                return 1;
        }

        if (skb->protocol == cpu_to_be16(ETH_P_8021Q)) {
                skb = vlan_untag(skb);
                if (unlikely(!skb))
                        goto out;
        }

        proto = ntohs(eth_hdr(skb)->h_proto);
        if (proto != ETH_P_IP)
                goto out;
        if (skb->pkt_type == PACKET_OTHERHOST)
                goto out;
        if (skb_shared(skb))
                goto out;

        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
                goto out;
        iph = (struct iphdr *)skb->data;
        if (iph->ihl < 5 || iph->version != 4)
                goto out;
        if (!pskb_may_pull(skb, iph->ihl*4))
                goto out;
        iph = (struct iphdr *)skb->data;
        if (ip_fast_csum((u8 *)iph, iph->ihl) != 0)
                goto out;

        len = ntohs(iph->tot_len);
        if (skb->len < len || len < iph->ihl*4)
                goto out;

        /*
         * Our transport medium may have padded the buffer out.
         * Now We trim to the true length of the frame.
         */
        if (pskb_trim_rcsum(skb, len))
                goto out;

        iph = (struct iphdr *)skb->data;
        if (iph->protocol != IPPROTO_UDP)
                goto out;

        len -= iph->ihl*4;
        uh = (struct udphdr *)(((char *)iph) + iph->ihl*4);
        ulen = ntohs(uh->len);

        if (ulen != len)
                goto out;
        if (checksum_udp(skb, uh, ulen, iph->saddr, iph->daddr))
                goto out;

        list_for_each_entry_safe(np, tmp, &npinfo->rx_np, rx) {
                if (np->local_ip && np->local_ip != iph->daddr)
                        continue;
                if (np->remote_ip && np->remote_ip != iph->saddr)
                        continue;
                if (np->local_port && np->local_port != ntohs(uh->dest))
                        continue;

                np->rx_hook(np, ntohs(uh->source),
                               (char *)(uh+1),
                               ulen - sizeof(struct udphdr));
                hits++;
        }

        if (!hits)
                goto out;

        kfree_skb(skb);
        return 1;

out:
        if (atomic_read(&trapped)) {
                kfree_skb(skb);
                return 1;
        }

        return 0;
}

void netpoll_print_options(struct netpoll *np)
{
        np_info(np, "local port %d\n", np->local_port);
        np_info(np, "local IP %pI4\n", &np->local_ip);
        np_info(np, "interface '%s'\n", np->dev_name);
        np_info(np, "remote port %d\n", np->remote_port);
        np_info(np, "remote IP %pI4\n", &np->remote_ip);
        np_info(np, "remote ethernet address %pM\n", np->remote_mac);
}
EXPORT_SYMBOL(netpoll_print_options);

int netpoll_parse_options(struct netpoll *np, char *opt)
{
        char *cur=opt, *delim;

        if (*cur != '@') {
                if ((delim = strchr(cur, '@')) == NULL)
                        goto parse_failed;
                *delim = 0;
                np->local_port = simple_strtol(cur, NULL, 10);
                cur = delim;
        }
        cur++;

        if (*cur != '/') {
                if ((delim = strchr(cur, '/')) == NULL)
                        goto parse_failed;
                *delim = 0;
                np->local_ip = in_aton(cur);
                cur = delim;
        }
        cur++;

        if (*cur != ',') {
                /* parse out dev name */
                if ((delim = strchr(cur, ',')) == NULL)
                        goto parse_failed;
                *delim = 0;
                strlcpy(np->dev_name, cur, sizeof(np->dev_name));
                cur = delim;
        }
        cur++;

        if (*cur != '@') {
                /* dst port */
                if ((delim = strchr(cur, '@')) == NULL)
                        goto parse_failed;
                *delim = 0;
                if (*cur == ' ' || *cur == '\t')
                        np_info(np, "warning: whitespace is not allowed\n");
                np->remote_port = simple_strtol(cur, NULL, 10);
                cur = delim;
        }
        cur++;

        /* dst ip */
        if ((delim = strchr(cur, '/')) == NULL)
                goto parse_failed;
        *delim = 0;
        np->remote_ip = in_aton(cur);
        cur = delim + 1;

        if (*cur != 0) {
                /* MAC address */
                if (!mac_pton(cur, np->remote_mac))
                        goto parse_failed;
        }

        netpoll_print_options(np);

        return 0;

 parse_failed:
        np_info(np, "couldn't parse config at '%s'!\n", cur);
        return -1;
}
EXPORT_SYMBOL(netpoll_parse_options);

int __netpoll_setup(struct netpoll *np, struct net_device *ndev, gfp_t gfp)
{
        struct netpoll_info *npinfo;
        const struct net_device_ops *ops;
        unsigned long flags;
        int err;

        np->dev = ndev;
        strlcpy(np->dev_name, ndev->name, IFNAMSIZ);

        if ((ndev->priv_flags & IFF_DISABLE_NETPOLL) ||
            !ndev->netdev_ops->ndo_poll_controller) {
                np_err(np, "%s doesn't support polling, aborting\n",
                       np->dev_name);
                err = -ENOTSUPP;
                goto out;
        }

        if (!ndev->npinfo) {
                npinfo = kmalloc(sizeof(*npinfo), gfp);
                if (!npinfo) {
                        err = -ENOMEM;
                        goto out;
                }

                npinfo->rx_flags = 0;
                INIT_LIST_HEAD(&npinfo->rx_np);

                spin_lock_init(&npinfo->rx_lock);
                skb_queue_head_init(&npinfo->arp_tx);
                skb_queue_head_init(&npinfo->txq);
                INIT_DELAYED_WORK(&npinfo->tx_work, queue_process);

                atomic_set(&npinfo->refcnt, 1);

                ops = np->dev->netdev_ops;
                if (ops->ndo_netpoll_setup) {
                        err = ops->ndo_netpoll_setup(ndev, npinfo, gfp);
                        if (err)
                                goto free_npinfo;
                }
        } else {
                npinfo = ndev->npinfo;
                atomic_inc(&npinfo->refcnt);
        }

        npinfo->netpoll = np;

        if (np->rx_hook) {
                spin_lock_irqsave(&npinfo->rx_lock, flags);
                npinfo->rx_flags |= NETPOLL_RX_ENABLED;
                list_add_tail(&np->rx, &npinfo->rx_np);
                spin_unlock_irqrestore(&npinfo->rx_lock, flags);
        }

        /* last thing to do is link it to the net device structure */
        rcu_assign_pointer(ndev->npinfo, npinfo);

        return 0;

free_npinfo:
        kfree(npinfo);
out:
        return err;
}
EXPORT_SYMBOL_GPL(__netpoll_setup);

int netpoll_setup(struct netpoll *np)
{
        struct net_device *ndev = NULL;
        struct in_device *in_dev;
        int err;

        if (np->dev_name)
                ndev = dev_get_by_name(&init_net, np->dev_name);
        if (!ndev) {
                np_err(np, "%s doesn't exist, aborting\n", np->dev_name);
                return -ENODEV;
        }

        if (ndev->master) {
                np_err(np, "%s is a slave device, aborting\n", np->dev_name);
                err = -EBUSY;
                goto put;
        }

        if (!netif_running(ndev)) {
                unsigned long atmost, atleast;

                np_info(np, "device %s not up yet, forcing it\n", np->dev_name);

                rtnl_lock();
                err = dev_open(ndev);
                rtnl_unlock();

                if (err) {
                        np_err(np, "failed to open %s\n", ndev->name);
                        goto put;
                }

                atleast = jiffies + HZ/10;
                atmost = jiffies + carrier_timeout * HZ;
                while (!netif_carrier_ok(ndev)) {
                        if (time_after(jiffies, atmost)) {
                                np_notice(np, "timeout waiting for carrier\n");
                                break;
                        }
                        msleep(1);
                }

                /* If carrier appears to come up instantly, we don't
                 * trust it and pause so that we don't pump all our
                 * queued console messages into the bitbucket.
                 */

                if (time_before(jiffies, atleast)) {
                        np_notice(np, "carrier detect appears untrustworthy, waiting 4 seconds\n");
                        msleep(4000);
                }
        }

        if (!np->local_ip) {
                rcu_read_lock();
                in_dev = __in_dev_get_rcu(ndev);

                if (!in_dev || !in_dev->ifa_list) {
                        rcu_read_unlock();
                        np_err(np, "no IP address for %s, aborting\n",
                               np->dev_name);
                        err = -EDESTADDRREQ;
                        goto put;
                }

                np->local_ip = in_dev->ifa_list->ifa_local;
                rcu_read_unlock();
                np_info(np, "local IP %pI4\n", &np->local_ip);
        }

        /* fill up the skb queue */
        refill_skbs();

        rtnl_lock();
        err = __netpoll_setup(np, ndev, GFP_KERNEL);
        rtnl_unlock();

        if (err)
                goto put;

        return 0;

put:
        dev_put(ndev);
        return err;
}
EXPORT_SYMBOL(netpoll_setup);

static int __init netpoll_init(void)
{
        skb_queue_head_init(&skb_pool);
        return 0;
}
core_initcall(netpoll_init);

static void rcu_cleanup_netpoll_info(struct rcu_head *rcu_head)
{
        struct netpoll_info *npinfo =
                        container_of(rcu_head, struct netpoll_info, rcu);

        skb_queue_purge(&npinfo->arp_tx);
        skb_queue_purge(&npinfo->txq);

        /* we can't call cancel_delayed_work_sync here, as we are in softirq */
        cancel_delayed_work(&npinfo->tx_work);

        /* clean after last, unfinished work */
        __skb_queue_purge(&npinfo->txq);
        /* now cancel it again */
        cancel_delayed_work(&npinfo->tx_work);
        kfree(npinfo);
}

void __netpoll_cleanup(struct netpoll *np)
{
        struct netpoll_info *npinfo;
        unsigned long flags;

        npinfo = np->dev->npinfo;
        if (!npinfo)
                return;

        if (!list_empty(&npinfo->rx_np)) {
                spin_lock_irqsave(&npinfo->rx_lock, flags);
                list_del(&np->rx);
                if (list_empty(&npinfo->rx_np))
                        npinfo->rx_flags &= ~NETPOLL_RX_ENABLED;
                spin_unlock_irqrestore(&npinfo->rx_lock, flags);
        }

        if (atomic_dec_and_test(&npinfo->refcnt)) {
                const struct net_device_ops *ops;

                ops = np->dev->netdev_ops;
                if (ops->ndo_netpoll_cleanup)
                        ops->ndo_netpoll_cleanup(np->dev);

                RCU_INIT_POINTER(np->dev->npinfo, NULL);
                call_rcu_bh(&npinfo->rcu, rcu_cleanup_netpoll_info);
        }
}
EXPORT_SYMBOL_GPL(__netpoll_cleanup);

static void rcu_cleanup_netpoll(struct rcu_head *rcu_head)
{
        struct netpoll *np = container_of(rcu_head, struct netpoll, rcu);

        __netpoll_cleanup(np);
        kfree(np);
}

void __netpoll_free_rcu(struct netpoll *np)
{
        call_rcu_bh(&np->rcu, rcu_cleanup_netpoll);
}
EXPORT_SYMBOL_GPL(__netpoll_free_rcu);

void netpoll_cleanup(struct netpoll *np)
{
        if (!np->dev)
                return;

        rtnl_lock();
        __netpoll_cleanup(np);
        rtnl_unlock();

        dev_put(np->dev);
        np->dev = NULL;
}
EXPORT_SYMBOL(netpoll_cleanup);

int netpoll_trap(void)
{
        return atomic_read(&trapped);
}
EXPORT_SYMBOL(netpoll_trap);

void netpoll_set_trap(int trap)
{
        if (trap)
                atomic_inc(&trapped);
        else
                atomic_dec(&trapped);
}
EXPORT_SYMBOL(netpoll_set_trap);