1/* 2 * INET An implementation of the TCP/IP protocol suite for the LINUX 3 * operating system. INET is implemented using the BSD Socket 4 * interface as the means of communication with the user level. 5 * 6 * Pseudo-driver for the loopback interface. 7 * 8 * Version: @(#)loopback.c 1.0.4b 08/16/93 9 * 10 * Authors: Ross Biro 11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 12 * Donald Becker, <becker@scyld.com> 13 * 14 * Alan Cox : Fixed oddments for NET3.014 15 * Alan Cox : Rejig for NET3.029 snap #3 16 * Alan Cox : Fixed NET3.029 bugs and sped up 17 * Larry McVoy : Tiny tweak to double performance 18 * Alan Cox : Backed out LMV's tweak - the linux mm 19 * can't take it... 20 * Michael Griffith: Don't bother computing the checksums 21 * on packets received on the loopback 22 * interface. 23 * Alexey Kuznetsov: Potential hang under some extreme 24 * cases removed. 25 * 26 * This program is free software; you can redistribute it and/or 27 * modify it under the terms of the GNU General Public License 28 * as published by the Free Software Foundation; either version 29 * 2 of the License, or (at your option) any later version. 30 */ 31#include <linux/kernel.h> 32#include <linux/jiffies.h> 33#include <linux/module.h> 34#include <linux/interrupt.h> 35#include <linux/fs.h> 36#include <linux/types.h> 37#include <linux/string.h> 38#include <linux/socket.h> 39#include <linux/errno.h> 40#include <linux/fcntl.h> 41#include <linux/in.h> 42#include <linux/init.h> 43 44#include <asm/system.h> 45#include <asm/uaccess.h> 46#include <asm/io.h> 47 48#include <linux/inet.h> 49#include <linux/netdevice.h> 50#include <linux/etherdevice.h> 51#include <linux/skbuff.h> 52#include <linux/ethtool.h> 53#include <net/sock.h> 54#include <net/checksum.h> 55#include <linux/if_ether.h> /* For the statistics structure. */ 56#include <linux/if_arp.h> /* For ARPHRD_ETHER */ 57#include <linux/ip.h> 58#include <linux/tcp.h> 59#include <linux/percpu.h> 60 61struct pcpu_lstats { 62 unsigned long packets; 63 unsigned long bytes; 64}; 65static DEFINE_PER_CPU(struct pcpu_lstats, pcpu_lstats); 66 67#define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16) 68 69/* KISS: just allocate small chunks and copy bits. 70 * 71 * So, in fact, this is documentation, explaining what we expect 72 * of largesending device modulo TCP checksum, which is ignored for loopback. 73 */ 74 75#ifdef LOOPBACK_TSO 76static void emulate_large_send_offload(struct sk_buff *skb) 77{ 78 struct iphdr *iph = ip_hdr(skb); 79 struct tcphdr *th = (struct tcphdr *)(skb_network_header(skb) + 80 (iph->ihl * 4)); 81 unsigned int doffset = (iph->ihl + th->doff) * 4; 82 unsigned int mtu = skb_shinfo(skb)->gso_size + doffset; 83 unsigned int offset = 0; 84 u32 seq = ntohl(th->seq); 85 u16 id = ntohs(iph->id); 86 87 while (offset + doffset < skb->len) { 88 unsigned int frag_size = min(mtu, skb->len - offset) - doffset; 89 struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC); 90 91 if (!nskb) 92 break; 93 skb_reserve(nskb, 32); 94 skb_set_mac_header(nskb, -ETH_HLEN); 95 skb_reset_network_header(nskb); 96 iph = ip_hdr(nskb); 97 skb_copy_to_linear_data(nskb, skb_network_header(skb), 98 doffset); 99 if (skb_copy_bits(skb, 100 doffset + offset, 101 nskb->data + doffset, 102 frag_size)) 103 BUG(); 104 skb_put(nskb, doffset + frag_size); 105 nskb->ip_summed = CHECKSUM_UNNECESSARY; 106 nskb->dev = skb->dev; 107 nskb->priority = skb->priority; 108 nskb->protocol = skb->protocol; 109 nskb->dst = dst_clone(skb->dst); 110 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 111 nskb->pkt_type = skb->pkt_type; 112 113 th = (struct tcphdr *)(skb_network_header(nskb) + iph->ihl * 4); 114 iph->tot_len = htons(frag_size + doffset); 115 iph->id = htons(id); 116 iph->check = 0; 117 iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl); 118 th->seq = htonl(seq); 119 if (offset + doffset + frag_size < skb->len) 120 th->fin = th->psh = 0; 121 netif_rx(nskb); 122 offset += frag_size; 123 seq += frag_size; 124 id++; 125 } 126 127 dev_kfree_skb(skb); 128} 129#endif /* LOOPBACK_TSO */ 130 131/* 132 * The higher levels take care of making this non-reentrant (it's 133 * called with bh's disabled). 134 */ 135static int loopback_xmit(struct sk_buff *skb, struct net_device *dev) 136{ 137 struct pcpu_lstats *lb_stats; 138 139 skb_orphan(skb); 140 141 skb->protocol = eth_type_trans(skb,dev); 142#ifndef LOOPBACK_MUST_CHECKSUM 143 skb->ip_summed = CHECKSUM_UNNECESSARY; 144#endif 145 146#ifdef LOOPBACK_TSO 147 if (skb_is_gso(skb)) { 148 BUG_ON(skb->protocol != htons(ETH_P_IP)); 149 BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP); 150 151 emulate_large_send_offload(skb); 152 return 0; 153 } 154#endif 155 dev->last_rx = jiffies; 156 157 /* it's OK to use __get_cpu_var() because BHs are off */ 158 lb_stats = &__get_cpu_var(pcpu_lstats); 159 lb_stats->bytes += skb->len; 160 lb_stats->packets++; 161 162 netif_rx(skb); 163 164 return 0; 165} 166 167static struct net_device_stats *get_stats(struct net_device *dev) 168{ 169 struct net_device_stats *stats = &dev->stats; 170 unsigned long bytes = 0; 171 unsigned long packets = 0; 172 int i; 173 174 for_each_possible_cpu(i) { 175 const struct pcpu_lstats *lb_stats; 176 177 lb_stats = &per_cpu(pcpu_lstats, i); 178 bytes += lb_stats->bytes; 179 packets += lb_stats->packets; 180 } 181 stats->rx_packets = packets; 182 stats->tx_packets = packets; 183 stats->rx_bytes = bytes; 184 stats->tx_bytes = bytes; 185 return stats; 186} 187 188static u32 always_on(struct net_device *dev) 189{ 190 return 1; 191} 192 193static const struct ethtool_ops loopback_ethtool_ops = { 194 .get_link = always_on, 195 .get_tso = ethtool_op_get_tso, 196 .set_tso = ethtool_op_set_tso, 197 .get_tx_csum = always_on, 198 .get_sg = always_on, 199 .get_rx_csum = always_on, 200}; 201 202/* 203 * The loopback device is special. There is only one instance and 204 * it is statically allocated. Don't do this for other devices. 205 */ 206struct net_device loopback_dev = { 207 .name = "lo", 208 .get_stats = &get_stats, 209 .mtu = (16 * 1024) + 20 + 20 + 12, 210 .hard_start_xmit = loopback_xmit, 211 .hard_header = eth_header, 212 .hard_header_cache = eth_header_cache, 213 .header_cache_update = eth_header_cache_update, 214 .hard_header_len = ETH_HLEN, /* 14 */ 215 .addr_len = ETH_ALEN, /* 6 */ 216 .tx_queue_len = 0, 217 .type = ARPHRD_LOOPBACK, /* 0x0001*/ 218 .rebuild_header = eth_rebuild_header, 219 .flags = IFF_LOOPBACK, 220 .features = NETIF_F_SG | NETIF_F_FRAGLIST 221#ifdef LOOPBACK_TSO 222 | NETIF_F_TSO 223#endif 224 | NETIF_F_NO_CSUM | NETIF_F_HIGHDMA 225 | NETIF_F_LLTX, 226 .ethtool_ops = &loopback_ethtool_ops, 227}; 228 229/* Setup and register the loopback device. */ 230static int __init loopback_init(void) 231{ 232 return register_netdev(&loopback_dev); 233}; 234 235module_init(loopback_init); 236 237EXPORT_SYMBOL(loopback_dev); 238