net/core/netpoll.c - kernel/msm-4.9 - Gitiles

 /*
  * 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.
  */

 #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 <net/tcp.h>
 #include <net/udp.h>
 #include <asm/unaligned.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
 #define MAX_QUEUE_DEPTH (MAX_SKBS / 2)

 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 \
 		(MAX_UDP_CHUNK + sizeof(struct udphdr) + \
 				sizeof(struct iphdr) + sizeof(struct ethhdr))

 static void zap_completion_queue(void);
 static void arp_reply(struct sk_buff *skb);

 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;

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

 		local_irq_save(flags);
 		netif_tx_lock(dev);
 		if ((netif_queue_stopped(dev) ||
 		     netif_subqueue_stopped(dev, skb)) ||
 		     dev->hard_start_xmit(skb, dev) != NETDEV_TX_OK) {
 			skb_queue_head(&npinfo->txq, skb);
 			netif_tx_unlock(dev);
 			local_irq_restore(flags);

 			schedule_delayed_work(&npinfo->tx_work, HZ/10);
 			return;
 		}
 		netif_tx_unlock(dev);
 		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);

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

 	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;

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

 			if (!budget)
 				break;
 		}
 	}
 }

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

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

 void netpoll_poll(struct netpoll *np)
 {
 	struct net_device *dev = np->dev;

 	if (!dev || !netif_running(dev) || !dev->poll_controller)
 		return;

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

 	poll_napi(dev);

 	service_arp_queue(dev->npinfo);

 	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)
 				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(np);
 			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;
 }

 static void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 {
 	int status = NETDEV_TX_BUSY;
 	unsigned long tries;
 	struct net_device *dev = np->dev;
 	struct netpoll_info *npinfo = 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)) {
 		unsigned long flags;

 		local_irq_save(flags);
 		/* try until next clock tick */
 		for (tries = jiffies_to_usecs(1)/USEC_PER_POLL;
 		     tries > 0; --tries) {
 			if (netif_tx_trylock(dev)) {
 				if (!netif_queue_stopped(dev) &&
 				    !netif_subqueue_stopped(dev, skb))
 					status = dev->hard_start_xmit(skb, dev);
 				netif_tx_unlock(dev);

 				if (status == NETDEV_TX_OK)
 					break;

 			}

 			/* tickle device maybe there is some cleanup */
 			netpoll_poll(np);

 			udelay(USEC_PER_POLL);
 		}
 		local_irq_restore(flags);
 	}

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

 void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
 {
 	int total_len, eth_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 = eth_len = udp_len + sizeof(*iph);
 	total_len = eth_len + ETH_HLEN + NET_IP_ALIGN;

 	skb = find_skb(np, total_len, total_len - len);
 	if (!skb)
 		return;

 	skb_copy_to_linear_data(skb, msg, len);
 	skb->len += 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(htonl(np->local_ip),
 					htonl(np->remote_ip),
 					udp_len, IPPROTO_UDP,
 					csum_partial((unsigned char *)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(htonl(np->local_ip), &(iph->saddr));
 	put_unaligned(htonl(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);
 }

 static void arp_reply(struct sk_buff *skb)
 {
 	struct netpoll_info *npinfo = skb->dev->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 = NULL;

 	if (npinfo->rx_np && npinfo->rx_np->dev == skb->dev)
 		np = npinfo->rx_np;
 	if (!np)
 		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 (tip != htonl(np->local_ip) ||
 	    ipv4_is_loopback(tip) || ipv4_is_multicast(tip))
 		return;

 	size = arp_hdr_len(skb->dev);
 	send_skb = find_skb(np, size + LL_RESERVED_SPACE(np->dev),
 			    LL_RESERVED_SPACE(np->dev));

 	if (!send_skb)
 		return;

 	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);
 		return;
 	}

 	/*
 	 * 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);
 }

 int __netpoll_rx(struct sk_buff *skb)
 {
 	int proto, len, ulen;
 	struct iphdr *iph;
 	struct udphdr *uh;
 	struct netpoll_info *npi = skb->dev->npinfo;
 	struct netpoll *np = npi->rx_np;

 	if (!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(&npi->arp_tx, skb);
 		return 1;
 	}

 	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;

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

 	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;
 	if (np->local_ip && np->local_ip != ntohl(iph->daddr))
 		goto out;
 	if (np->remote_ip && np->remote_ip != ntohl(iph->saddr))
 		goto out;
 	if (np->local_port && np->local_port != ntohs(uh->dest))
 		goto out;

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

 	kfree_skb(skb);
 	return 1;

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

 	return 0;
 }

 void netpoll_print_options(struct netpoll *np)
 {
 	DECLARE_MAC_BUF(mac);
 	printk(KERN_INFO "%s: local port %d\n",
 			 np->name, np->local_port);
 	printk(KERN_INFO "%s: local IP %d.%d.%d.%d\n",
 			 np->name, HIPQUAD(np->local_ip));
 	printk(KERN_INFO "%s: interface %s\n",
 			 np->name, np->dev_name);
 	printk(KERN_INFO "%s: remote port %d\n",
 			 np->name, np->remote_port);
 	printk(KERN_INFO "%s: remote IP %d.%d.%d.%d\n",
 			 np->name, HIPQUAD(np->remote_ip));
 	printk(KERN_INFO "%s: remote ethernet address %s\n",
 	                 np->name, print_mac(mac, np->remote_mac));
 }

 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 = ntohl(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;
 		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 = ntohl(in_aton(cur));
 	cur = delim + 1;

 	if (*cur != 0) {
 		/* MAC address */
 		if ((delim = strchr(cur, ':')) == NULL)
 			goto parse_failed;
 		*delim = 0;
 		np->remote_mac[0] = simple_strtol(cur, NULL, 16);
 		cur = delim + 1;
 		if ((delim = strchr(cur, ':')) == NULL)
 			goto parse_failed;
 		*delim = 0;
 		np->remote_mac[1] = simple_strtol(cur, NULL, 16);
 		cur = delim + 1;
 		if ((delim = strchr(cur, ':')) == NULL)
 			goto parse_failed;
 		*delim = 0;
 		np->remote_mac[2] = simple_strtol(cur, NULL, 16);
 		cur = delim + 1;
 		if ((delim = strchr(cur, ':')) == NULL)
 			goto parse_failed;
 		*delim = 0;
 		np->remote_mac[3] = simple_strtol(cur, NULL, 16);
 		cur = delim + 1;
 		if ((delim = strchr(cur, ':')) == NULL)
 			goto parse_failed;
 		*delim = 0;
 		np->remote_mac[4] = simple_strtol(cur, NULL, 16);
 		cur = delim + 1;
 		np->remote_mac[5] = simple_strtol(cur, NULL, 16);
 	}

 	netpoll_print_options(np);

 	return 0;

  parse_failed:
 	printk(KERN_INFO "%s: couldn't parse config at %s!\n",
 	       np->name, cur);
 	return -1;
 }

 int netpoll_setup(struct netpoll *np)
 {
 	struct net_device *ndev = NULL;
 	struct in_device *in_dev;
 	struct netpoll_info *npinfo;
 	unsigned long flags;
 	int err;

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

 	np->dev = ndev;
 	if (!ndev->npinfo) {
 		npinfo = kmalloc(sizeof(*npinfo), GFP_KERNEL);
 		if (!npinfo) {
 			err = -ENOMEM;
 			goto release;
 		}

 		npinfo->rx_flags = 0;
 		npinfo->rx_np = NULL;

 		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);
 	} else {
 		npinfo = ndev->npinfo;
 		atomic_inc(&npinfo->refcnt);
 	}

 	if (!ndev->poll_controller) {
 		printk(KERN_ERR "%s: %s doesn't support polling, aborting.\n",
 		       np->name, np->dev_name);
 		err = -ENOTSUPP;
 		goto release;
 	}

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

 		printk(KERN_INFO "%s: device %s not up yet, forcing it\n",
 		       np->name, np->dev_name);

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

 		if (err) {
 			printk(KERN_ERR "%s: failed to open %s\n",
 			       np->name, ndev->name);
 			goto release;
 		}

 		atleast = jiffies + HZ/10;
 		atmost = jiffies + 4*HZ;
 		while (!netif_carrier_ok(ndev)) {
 			if (time_after(jiffies, atmost)) {
 				printk(KERN_NOTICE
 				       "%s: timeout waiting for carrier\n",
 				       np->name);
 				break;
 			}
 			cond_resched();
 		}

 		/* 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)) {
 			printk(KERN_NOTICE "%s: carrier detect appears"
 			       " untrustworthy, waiting 4 seconds\n",
 			       np->name);
 			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();
 			printk(KERN_ERR "%s: no IP address for %s, aborting\n",
 			       np->name, np->dev_name);
 			err = -EDESTADDRREQ;
 			goto release;
 		}

 		np->local_ip = ntohl(in_dev->ifa_list->ifa_local);
 		rcu_read_unlock();
 		printk(KERN_INFO "%s: local IP %d.%d.%d.%d\n",
 		       np->name, HIPQUAD(np->local_ip));
 	}

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

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

 	/* last thing to do is link it to the net device structure */
 	ndev->npinfo = npinfo;

 	/* avoid racing with NAPI reading npinfo */
 	synchronize_rcu();

 	return 0;

  release:
 	if (!ndev->npinfo)
 		kfree(npinfo);
 	np->dev = NULL;
 	dev_put(ndev);
 	return err;
 }

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

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

 	if (np->dev) {
 		npinfo = np->dev->npinfo;
 		if (npinfo) {
 			if (npinfo->rx_np == np) {
 				spin_lock_irqsave(&npinfo->rx_lock, flags);
 				npinfo->rx_np = NULL;
 				npinfo->rx_flags &= ~NETPOLL_RX_ENABLED;
 				spin_unlock_irqrestore(&npinfo->rx_lock, flags);
 			}

 			if (atomic_dec_and_test(&npinfo->refcnt)) {
 				skb_queue_purge(&npinfo->arp_tx);
 				skb_queue_purge(&npinfo->txq);
 				cancel_rearming_delayed_work(&npinfo->tx_work);

 				/* clean after last, unfinished work */
 				__skb_queue_purge(&npinfo->txq);
 				kfree(npinfo);
 				np->dev->npinfo = NULL;
 			}
 		}

 		dev_put(np->dev);
 	}

 	np->dev = NULL;
 }

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

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

 EXPORT_SYMBOL(netpoll_set_trap);
 EXPORT_SYMBOL(netpoll_trap);
 EXPORT_SYMBOL(netpoll_print_options);
 EXPORT_SYMBOL(netpoll_parse_options);
 EXPORT_SYMBOL(netpoll_setup);
 EXPORT_SYMBOL(netpoll_cleanup);
 EXPORT_SYMBOL(netpoll_send_udp);
 EXPORT_SYMBOL(netpoll_poll);
	/*
	* 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.
	*/

	#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 <net/tcp.h>
	#include <net/udp.h>
	#include <asm/unaligned.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
	#define MAX_QUEUE_DEPTH (MAX_SKBS / 2)

	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 \
	(MAX_UDP_CHUNK + sizeof(struct udphdr) + \
	sizeof(struct iphdr) + sizeof(struct ethhdr))

	static void zap_completion_queue(void);
	static void arp_reply(struct sk_buff *skb);

	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;

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

	local_irq_save(flags);
	netif_tx_lock(dev);
	if ((netif_queue_stopped(dev) \|\|
	netif_subqueue_stopped(dev, skb)) \|\|
	dev->hard_start_xmit(skb, dev) != NETDEV_TX_OK) {
	skb_queue_head(&npinfo->txq, skb);
	netif_tx_unlock(dev);
	local_irq_restore(flags);

	schedule_delayed_work(&npinfo->tx_work, HZ/10);
	return;
	}
	netif_tx_unlock(dev);
	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);

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

	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;

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

	if (!budget)
	break;
	}
	}
	}

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

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

	void netpoll_poll(struct netpoll *np)
	{
	struct net_device *dev = np->dev;

	if (!dev \|\| !netif_running(dev) \|\| !dev->poll_controller)
	return;

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

	poll_napi(dev);

	service_arp_queue(dev->npinfo);

	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)
	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(np);
	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;
	}

	static void netpoll_send_skb(struct netpoll np, struct sk_buff skb)
	{
	int status = NETDEV_TX_BUSY;
	unsigned long tries;
	struct net_device *dev = np->dev;
	struct netpoll_info *npinfo = 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)) {
	unsigned long flags;

	local_irq_save(flags);
	/* try until next clock tick */
	for (tries = jiffies_to_usecs(1)/USEC_PER_POLL;
	tries > 0; --tries) {
	if (netif_tx_trylock(dev)) {
	if (!netif_queue_stopped(dev) &&
	!netif_subqueue_stopped(dev, skb))
	status = dev->hard_start_xmit(skb, dev);
	netif_tx_unlock(dev);

	if (status == NETDEV_TX_OK)
	break;

	}

	/* tickle device maybe there is some cleanup */
	netpoll_poll(np);

	udelay(USEC_PER_POLL);
	}
	local_irq_restore(flags);
	}

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

	void netpoll_send_udp(struct netpoll np, const char msg, int len)
	{
	int total_len, eth_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 = eth_len = udp_len + sizeof(*iph);
	total_len = eth_len + ETH_HLEN + NET_IP_ALIGN;

	skb = find_skb(np, total_len, total_len - len);
	if (!skb)
	return;

	skb_copy_to_linear_data(skb, msg, len);
	skb->len += 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(htonl(np->local_ip),
	htonl(np->remote_ip),
	udp_len, IPPROTO_UDP,
	csum_partial((unsigned char *)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(htonl(np->local_ip), &(iph->saddr));
	put_unaligned(htonl(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);
	}

	static void arp_reply(struct sk_buff *skb)
	{
	struct netpoll_info *npinfo = skb->dev->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 = NULL;

	if (npinfo->rx_np && npinfo->rx_np->dev == skb->dev)
	np = npinfo->rx_np;
	if (!np)
	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 (tip != htonl(np->local_ip) \|\|
	ipv4_is_loopback(tip) \|\| ipv4_is_multicast(tip))
	return;

	size = arp_hdr_len(skb->dev);
	send_skb = find_skb(np, size + LL_RESERVED_SPACE(np->dev),
	LL_RESERVED_SPACE(np->dev));

	if (!send_skb)
	return;

	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);
	return;
	}

	/*
	* 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);
	}

	int __netpoll_rx(struct sk_buff *skb)
	{
	int proto, len, ulen;
	struct iphdr *iph;
	struct udphdr *uh;
	struct netpoll_info *npi = skb->dev->npinfo;
	struct netpoll *np = npi->rx_np;

	if (!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(&npi->arp_tx, skb);
	return 1;
	}

	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;

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

	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;
	if (np->local_ip && np->local_ip != ntohl(iph->daddr))
	goto out;
	if (np->remote_ip && np->remote_ip != ntohl(iph->saddr))
	goto out;
	if (np->local_port && np->local_port != ntohs(uh->dest))
	goto out;

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

	kfree_skb(skb);
	return 1;

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

	return 0;
	}

	void netpoll_print_options(struct netpoll *np)
	{
	DECLARE_MAC_BUF(mac);
	printk(KERN_INFO "%s: local port %d\n",
	np->name, np->local_port);
	printk(KERN_INFO "%s: local IP %d.%d.%d.%d\n",
	np->name, HIPQUAD(np->local_ip));
	printk(KERN_INFO "%s: interface %s\n",
	np->name, np->dev_name);
	printk(KERN_INFO "%s: remote port %d\n",
	np->name, np->remote_port);
	printk(KERN_INFO "%s: remote IP %d.%d.%d.%d\n",
	np->name, HIPQUAD(np->remote_ip));
	printk(KERN_INFO "%s: remote ethernet address %s\n",
	np->name, print_mac(mac, np->remote_mac));
	}

	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 = ntohl(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;
	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 = ntohl(in_aton(cur));
	cur = delim + 1;

	if (*cur != 0) {
	/* MAC address */
	if ((delim = strchr(cur, ':')) == NULL)
	goto parse_failed;
	*delim = 0;
	np->remote_mac[0] = simple_strtol(cur, NULL, 16);
	cur = delim + 1;
	if ((delim = strchr(cur, ':')) == NULL)
	goto parse_failed;
	*delim = 0;
	np->remote_mac[1] = simple_strtol(cur, NULL, 16);
	cur = delim + 1;
	if ((delim = strchr(cur, ':')) == NULL)
	goto parse_failed;
	*delim = 0;
	np->remote_mac[2] = simple_strtol(cur, NULL, 16);
	cur = delim + 1;
	if ((delim = strchr(cur, ':')) == NULL)
	goto parse_failed;
	*delim = 0;
	np->remote_mac[3] = simple_strtol(cur, NULL, 16);
	cur = delim + 1;
	if ((delim = strchr(cur, ':')) == NULL)
	goto parse_failed;
	*delim = 0;
	np->remote_mac[4] = simple_strtol(cur, NULL, 16);
	cur = delim + 1;
	np->remote_mac[5] = simple_strtol(cur, NULL, 16);
	}

	netpoll_print_options(np);

	return 0;

	parse_failed:
	printk(KERN_INFO "%s: couldn't parse config at %s!\n",
	np->name, cur);
	return -1;
	}

	int netpoll_setup(struct netpoll *np)
	{
	struct net_device *ndev = NULL;
	struct in_device *in_dev;
	struct netpoll_info *npinfo;
	unsigned long flags;
	int err;

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

	np->dev = ndev;
	if (!ndev->npinfo) {
	npinfo = kmalloc(sizeof(*npinfo), GFP_KERNEL);
	if (!npinfo) {
	err = -ENOMEM;
	goto release;
	}

	npinfo->rx_flags = 0;
	npinfo->rx_np = NULL;

	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);
	} else {
	npinfo = ndev->npinfo;
	atomic_inc(&npinfo->refcnt);
	}

	if (!ndev->poll_controller) {
	printk(KERN_ERR "%s: %s doesn't support polling, aborting.\n",
	np->name, np->dev_name);
	err = -ENOTSUPP;
	goto release;
	}

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

	printk(KERN_INFO "%s: device %s not up yet, forcing it\n",
	np->name, np->dev_name);

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

	if (err) {
	printk(KERN_ERR "%s: failed to open %s\n",
	np->name, ndev->name);
	goto release;
	}

	atleast = jiffies + HZ/10;
	atmost = jiffies + 4*HZ;
	while (!netif_carrier_ok(ndev)) {
	if (time_after(jiffies, atmost)) {
	printk(KERN_NOTICE
	"%s: timeout waiting for carrier\n",
	np->name);
	break;
	}
	cond_resched();
	}

	/* 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)) {
	printk(KERN_NOTICE "%s: carrier detect appears"
	" untrustworthy, waiting 4 seconds\n",
	np->name);
	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();
	printk(KERN_ERR "%s: no IP address for %s, aborting\n",
	np->name, np->dev_name);
	err = -EDESTADDRREQ;
	goto release;
	}

	np->local_ip = ntohl(in_dev->ifa_list->ifa_local);
	rcu_read_unlock();
	printk(KERN_INFO "%s: local IP %d.%d.%d.%d\n",
	np->name, HIPQUAD(np->local_ip));
	}

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

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

	/* last thing to do is link it to the net device structure */
	ndev->npinfo = npinfo;

	/* avoid racing with NAPI reading npinfo */
	synchronize_rcu();

	return 0;

	release:
	if (!ndev->npinfo)
	kfree(npinfo);
	np->dev = NULL;
	dev_put(ndev);
	return err;
	}

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

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

	if (np->dev) {
	npinfo = np->dev->npinfo;
	if (npinfo) {
	if (npinfo->rx_np == np) {
	spin_lock_irqsave(&npinfo->rx_lock, flags);
	npinfo->rx_np = NULL;
	npinfo->rx_flags &= ~NETPOLL_RX_ENABLED;
	spin_unlock_irqrestore(&npinfo->rx_lock, flags);
	}

	if (atomic_dec_and_test(&npinfo->refcnt)) {
	skb_queue_purge(&npinfo->arp_tx);
	skb_queue_purge(&npinfo->txq);
	cancel_rearming_delayed_work(&npinfo->tx_work);

	/* clean after last, unfinished work */
	__skb_queue_purge(&npinfo->txq);
	kfree(npinfo);
	np->dev->npinfo = NULL;
	}
	}

	dev_put(np->dev);
	}

	np->dev = NULL;
	}

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

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

	EXPORT_SYMBOL(netpoll_set_trap);
	EXPORT_SYMBOL(netpoll_trap);
	EXPORT_SYMBOL(netpoll_print_options);
	EXPORT_SYMBOL(netpoll_parse_options);
	EXPORT_SYMBOL(netpoll_setup);
	EXPORT_SYMBOL(netpoll_cleanup);
	EXPORT_SYMBOL(netpoll_send_udp);
	EXPORT_SYMBOL(netpoll_poll);