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/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* 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);
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