drivers/net/loopback.c - linux - Git at Google


            
            /*

            
             * 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.

            
             *

            
             *		Pseudo-driver for the loopback interface.

            
             *

            
             * Version:	@(#)loopback.c	1.0.4b	08/16/93

            
             *

            
             * Authors:	Ross Biro

            
             *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>

            
             *		Donald Becker, <becker@scyld.com>

            
             *

            
             *		Alan Cox	:	Fixed oddments for NET3.014

            
             *		Alan Cox	:	Rejig for NET3.029 snap #3

            
             *		Alan Cox	: 	Fixed NET3.029 bugs and sped up

            
             *		Larry McVoy	:	Tiny tweak to double performance

            
             *		Alan Cox	:	Backed out LMV's tweak - the linux mm

            
             *					can't take it...

            
             *              Michael Griffith:       Don't bother computing the checksums

            
             *                                      on packets received on the loopback

            
             *                                      interface.

            
             *		Alexey Kuznetsov:	Potential hang under some extreme

            
             *					cases removed.

            
             *

            
             *		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/kernel.h>

            
            #include <linux/jiffies.h>

            
            #include <linux/module.h>

            
            #include <linux/interrupt.h>

            
            #include <linux/fs.h>

            
            #include <linux/types.h>

            
            #include <linux/string.h>

            
            #include <linux/socket.h>

            
            #include <linux/errno.h>

            
            #include <linux/fcntl.h>

            
            #include <linux/in.h>

            
            #include <linux/init.h>


            #include <asm/system.h>

            
            #include <asm/uaccess.h>

            
            #include <asm/io.h>


            #include <linux/inet.h>

            
            #include <linux/netdevice.h>

            
            #include <linux/etherdevice.h>

            
            #include <linux/skbuff.h>

            
            #include <linux/ethtool.h>

            
            #include <net/sock.h>

            
            #include <net/checksum.h>

            
            #include <linux/if_ether.h>	/* For the statistics structure. */

            
            #include <linux/if_arp.h>	/* For ARPHRD_ETHER */

            
            #include <linux/ip.h>

            
            #include <linux/tcp.h>

            
            #include <linux/percpu.h>


            struct pcpu_lstats {

            
            	unsigned long packets;

            
            	unsigned long bytes;

            
            };

            
            static DEFINE_PER_CPU(struct pcpu_lstats, pcpu_lstats);


            #define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16)


            /* KISS: just allocate small chunks and copy bits.

            
             *

            
             * So, in fact, this is documentation, explaining what we expect

            
             * of largesending device modulo TCP checksum, which is ignored for loopback.

            
             */


            #ifdef LOOPBACK_TSO

            
            static void emulate_large_send_offload(struct sk_buff *skb)

            
            {

            
            	struct iphdr *iph = ip_hdr(skb);

            
            	struct tcphdr *th = (struct tcphdr *)(skb_network_header(skb) +

            
            					      (iph->ihl * 4));

            
            	unsigned int doffset = (iph->ihl + th->doff) * 4;

            
            	unsigned int mtu = skb_shinfo(skb)->gso_size + doffset;

            
            	unsigned int offset = 0;

            
            	u32 seq = ntohl(th->seq);

            
            	u16 id  = ntohs(iph->id);


            	while (offset + doffset < skb->len) {

            
            		unsigned int frag_size = min(mtu, skb->len - offset) - doffset;

            
            		struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC);


            		if (!nskb)

            
            			break;

            
            		skb_reserve(nskb, 32);

            
            		skb_set_mac_header(nskb, -ETH_HLEN);

            
            		skb_reset_network_header(nskb);

            
            		iph = ip_hdr(nskb);

            
            		skb_copy_to_linear_data(nskb, skb_network_header(skb),

            
            					doffset);

            
            		if (skb_copy_bits(skb,

            
            				  doffset + offset,

            
            				  nskb->data + doffset,

            
            				  frag_size))

            
            			BUG();

            
            		skb_put(nskb, doffset + frag_size);

            
            		nskb->ip_summed = CHECKSUM_UNNECESSARY;

            
            		nskb->dev = skb->dev;

            
            		nskb->priority = skb->priority;

            
            		nskb->protocol = skb->protocol;

            
            		nskb->dst = dst_clone(skb->dst);

            
            		memcpy(nskb->cb, skb->cb, sizeof(skb->cb));

            
            		nskb->pkt_type = skb->pkt_type;


            		th = (struct tcphdr *)(skb_network_header(nskb) + iph->ihl * 4);

            
            		iph->tot_len = htons(frag_size + doffset);

            
            		iph->id = htons(id);

            
            		iph->check = 0;

            
            		iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl);

            
            		th->seq = htonl(seq);

            
            		if (offset + doffset + frag_size < skb->len)

            
            			th->fin = th->psh = 0;

            
            		netif_rx(nskb);

            
            		offset += frag_size;

            
            		seq += frag_size;

            
            		id++;

            
            	}


            	dev_kfree_skb(skb);

            
            }

            
            #endif /* LOOPBACK_TSO */


            /*

            
             * The higher levels take care of making this non-reentrant (it's

            
             * called with bh's disabled).

            
             */

            
            static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)

            
            {

            
            	struct pcpu_lstats *lb_stats;


            	skb_orphan(skb);


            	skb->protocol = eth_type_trans(skb,dev);

            
            #ifndef LOOPBACK_MUST_CHECKSUM

            
            	skb->ip_summed = CHECKSUM_UNNECESSARY;

            
            #endif


            #ifdef LOOPBACK_TSO

            
            	if (skb_is_gso(skb)) {

            
            		BUG_ON(skb->protocol != htons(ETH_P_IP));

            
            		BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP);


            		emulate_large_send_offload(skb);

            
            		return 0;

            
            	}

            
            #endif

            
            	dev->last_rx = jiffies;


            	/* it's OK to use __get_cpu_var() because BHs are off */

            
            	lb_stats = &__get_cpu_var(pcpu_lstats);

            
            	lb_stats->bytes += skb->len;

            
            	lb_stats->packets++;


            	netif_rx(skb);


            	return 0;

            
            }


            static struct net_device_stats *get_stats(struct net_device *dev)

            
            {

            
            	struct net_device_stats *stats = &dev->stats;

            
            	unsigned long bytes = 0;

            
            	unsigned long packets = 0;

            
            	int i;


            	for_each_possible_cpu(i) {

            
            		const struct pcpu_lstats *lb_stats;


            		lb_stats = &per_cpu(pcpu_lstats, i);

            
            		bytes   += lb_stats->bytes;

            
            		packets += lb_stats->packets;

            
            	}

            
            	stats->rx_packets = packets;

            
            	stats->tx_packets = packets;

            
            	stats->rx_bytes = bytes;

            
            	stats->tx_bytes = bytes;

            
            	return stats;

            
            }


            static u32 always_on(struct net_device *dev)

            
            {

            
            	return 1;

            
            }


            static const struct ethtool_ops loopback_ethtool_ops = {

            
            	.get_link		= always_on,

            
            	.get_tso		= ethtool_op_get_tso,

            
            	.set_tso		= ethtool_op_set_tso,

            
            	.get_tx_csum		= always_on,

            
            	.get_sg			= always_on,

            
            	.get_rx_csum		= always_on,

            
            };


            /*

            
             * The loopback device is special. There is only one instance and

            
             * it is statically allocated. Don't do this for other devices.

            
             */

            
            struct net_device loopback_dev = {

            
            	.name	 		= "lo",

            
            	.get_stats		= &get_stats,

            
            	.mtu			= (16 * 1024) + 20 + 20 + 12,

            
            	.hard_start_xmit	= loopback_xmit,

            
            	.hard_header		= eth_header,

            
            	.hard_header_cache	= eth_header_cache,

            
            	.header_cache_update	= eth_header_cache_update,

            
            	.hard_header_len	= ETH_HLEN,	/* 14	*/

            
            	.addr_len		= ETH_ALEN,	/* 6	*/

            
            	.tx_queue_len		= 0,

            
            	.type			= ARPHRD_LOOPBACK,	/* 0x0001*/

            
            	.rebuild_header		= eth_rebuild_header,

            
            	.flags			= IFF_LOOPBACK,

            
            	.features 		= NETIF_F_SG | NETIF_F_FRAGLIST

            
            #ifdef LOOPBACK_TSO

            
            				  | NETIF_F_TSO

            
            #endif

            
            				  | NETIF_F_NO_CSUM | NETIF_F_HIGHDMA

            
            				  | NETIF_F_LLTX,

            
            	.ethtool_ops		= &loopback_ethtool_ops,

            
            };


            /* Setup and register the loopback device. */

            
            static int __init loopback_init(void)

            
            {

            
            	return register_netdev(&loopback_dev);

            
            };


            module_init(loopback_init);


            EXPORT_SYMBOL(loopback_dev);
	/*
	* 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.
	*
	* Pseudo-driver for the loopback interface.
	*
	* Version: @(#)loopback.c 1.0.4b 08/16/93
	*
	* Authors: Ross Biro
	* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
	* Donald Becker, <becker@scyld.com>
	*
	* Alan Cox : Fixed oddments for NET3.014
	* Alan Cox : Rejig for NET3.029 snap #3
	* Alan Cox : Fixed NET3.029 bugs and sped up
	* Larry McVoy : Tiny tweak to double performance
	* Alan Cox : Backed out LMV's tweak - the linux mm
	* can't take it...
	* Michael Griffith: Don't bother computing the checksums
	* on packets received on the loopback
	* interface.
	* Alexey Kuznetsov: Potential hang under some extreme
	* cases removed.
	*
	* 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/kernel.h>
	#include <linux/jiffies.h>
	#include <linux/module.h>
	#include <linux/interrupt.h>
	#include <linux/fs.h>
	#include <linux/types.h>
	#include <linux/string.h>
	#include <linux/socket.h>
	#include <linux/errno.h>
	#include <linux/fcntl.h>
	#include <linux/in.h>
	#include <linux/init.h>

	#include <asm/system.h>
	#include <asm/uaccess.h>
	#include <asm/io.h>

	#include <linux/inet.h>
	#include <linux/netdevice.h>
	#include <linux/etherdevice.h>
	#include <linux/skbuff.h>
	#include <linux/ethtool.h>
	#include <net/sock.h>
	#include <net/checksum.h>
	#include <linux/if_ether.h> /* For the statistics structure. */
	#include <linux/if_arp.h> /* For ARPHRD_ETHER */
	#include <linux/ip.h>
	#include <linux/tcp.h>
	#include <linux/percpu.h>

	struct pcpu_lstats {
	unsigned long packets;
	unsigned long bytes;
	};
	static DEFINE_PER_CPU(struct pcpu_lstats, pcpu_lstats);

	#define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16)

	/* KISS: just allocate small chunks and copy bits.
	*
	* So, in fact, this is documentation, explaining what we expect
	* of largesending device modulo TCP checksum, which is ignored for loopback.
	*/

	#ifdef LOOPBACK_TSO
	static void emulate_large_send_offload(struct sk_buff *skb)
	{
	struct iphdr *iph = ip_hdr(skb);
	struct tcphdr th = (struct tcphdr )(skb_network_header(skb) +
	(iph->ihl * 4));
	unsigned int doffset = (iph->ihl + th->doff) * 4;
	unsigned int mtu = skb_shinfo(skb)->gso_size + doffset;
	unsigned int offset = 0;
	u32 seq = ntohl(th->seq);
	u16 id = ntohs(iph->id);

	while (offset + doffset < skb->len) {
	unsigned int frag_size = min(mtu, skb->len - offset) - doffset;
	struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC);

	if (!nskb)
	break;
	skb_reserve(nskb, 32);
	skb_set_mac_header(nskb, -ETH_HLEN);
	skb_reset_network_header(nskb);
	iph = ip_hdr(nskb);
	skb_copy_to_linear_data(nskb, skb_network_header(skb),
	doffset);
	if (skb_copy_bits(skb,
	doffset + offset,
	nskb->data + doffset,
	frag_size))
	BUG();
	skb_put(nskb, doffset + frag_size);
	nskb->ip_summed = CHECKSUM_UNNECESSARY;
	nskb->dev = skb->dev;
	nskb->priority = skb->priority;
	nskb->protocol = skb->protocol;
	nskb->dst = dst_clone(skb->dst);
	memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
	nskb->pkt_type = skb->pkt_type;

	th = (struct tcphdr )(skb_network_header(nskb) + iph->ihl 4);
	iph->tot_len = htons(frag_size + doffset);
	iph->id = htons(id);
	iph->check = 0;
	iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl);
	th->seq = htonl(seq);
	if (offset + doffset + frag_size < skb->len)
	th->fin = th->psh = 0;
	netif_rx(nskb);
	offset += frag_size;
	seq += frag_size;
	id++;
	}

	dev_kfree_skb(skb);
	}
	#endif /* LOOPBACK_TSO */

	/*
	* The higher levels take care of making this non-reentrant (it's
	* called with bh's disabled).
	*/
	static int loopback_xmit(struct sk_buff skb, struct net_device dev)
	{
	struct pcpu_lstats *lb_stats;

	skb_orphan(skb);

	skb->protocol = eth_type_trans(skb,dev);
	#ifndef LOOPBACK_MUST_CHECKSUM
	skb->ip_summed = CHECKSUM_UNNECESSARY;
	#endif

	#ifdef LOOPBACK_TSO
	if (skb_is_gso(skb)) {
	BUG_ON(skb->protocol != htons(ETH_P_IP));
	BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP);

	emulate_large_send_offload(skb);
	return 0;
	}
	#endif
	dev->last_rx = jiffies;

	/* it's OK to use __get_cpu_var() because BHs are off */
	lb_stats = &__get_cpu_var(pcpu_lstats);
	lb_stats->bytes += skb->len;
	lb_stats->packets++;

	netif_rx(skb);

	return 0;
	}

	static struct net_device_stats get_stats(struct net_device dev)
	{
	struct net_device_stats *stats = &dev->stats;
	unsigned long bytes = 0;
	unsigned long packets = 0;
	int i;

	for_each_possible_cpu(i) {
	const struct pcpu_lstats *lb_stats;

	lb_stats = &per_cpu(pcpu_lstats, i);
	bytes += lb_stats->bytes;
	packets += lb_stats->packets;
	}
	stats->rx_packets = packets;
	stats->tx_packets = packets;
	stats->rx_bytes = bytes;
	stats->tx_bytes = bytes;
	return stats;
	}

	static u32 always_on(struct net_device *dev)
	{
	return 1;
	}

	static const struct ethtool_ops loopback_ethtool_ops = {
	.get_link = always_on,
	.get_tso = ethtool_op_get_tso,
	.set_tso = ethtool_op_set_tso,
	.get_tx_csum = always_on,
	.get_sg = always_on,
	.get_rx_csum = always_on,
	};

	/*
	* The loopback device is special. There is only one instance and
	* it is statically allocated. Don't do this for other devices.
	*/
	struct net_device loopback_dev = {
	.name = "lo",
	.get_stats = &get_stats,
	.mtu = (16 * 1024) + 20 + 20 + 12,
	.hard_start_xmit = loopback_xmit,
	.hard_header = eth_header,
	.hard_header_cache = eth_header_cache,
	.header_cache_update = eth_header_cache_update,
	.hard_header_len = ETH_HLEN, /* 14 */
	.addr_len = ETH_ALEN, /* 6 */
	.tx_queue_len = 0,
	.type = ARPHRD_LOOPBACK, /* 0x0001*/
	.rebuild_header = eth_rebuild_header,
	.flags = IFF_LOOPBACK,
	.features = NETIF_F_SG \| NETIF_F_FRAGLIST
	#ifdef LOOPBACK_TSO
	\| NETIF_F_TSO
	#endif
	\| NETIF_F_NO_CSUM \| NETIF_F_HIGHDMA
	\| NETIF_F_LLTX,
	.ethtool_ops = &loopback_ethtool_ops,
	};

	/* Setup and register the loopback device. */
	static int __init loopback_init(void)
	{
	return register_netdev(&loopback_dev);
	};

	module_init(loopback_init);

	EXPORT_SYMBOL(loopback_dev);