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 61 static DEFINE_PER_CPU(struct net_device_stats, loopback_stats); 62 63 #define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16) 64 65 /* KISS: just allocate small chunks and copy bits. 66 * 67 * So, in fact, this is documentation, explaining what we expect 68 * of largesending device modulo TCP checksum, which is ignored for loopback. 69 */ 70 71 static void emulate_large_send_offload(struct sk_buff *skb) 72 { 73 struct iphdr *iph = skb->nh.iph; 74 struct tcphdr *th = (struct tcphdr*)(skb->nh.raw + (iph->ihl * 4)); 75 unsigned int doffset = (iph->ihl + th->doff) * 4; 76 unsigned int mtu = skb_shinfo(skb)->tso_size + doffset; 77 unsigned int offset = 0; 78 u32 seq = ntohl(th->seq); 79 u16 id = ntohs(iph->id); 80 81 while (offset + doffset < skb->len) { 82 unsigned int frag_size = min(mtu, skb->len - offset) - doffset; 83 struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC); 84 85 if (!nskb) 86 break; 87 skb_reserve(nskb, 32); 88 nskb->mac.raw = nskb->data - 14; 89 nskb->nh.raw = nskb->data; 90 iph = nskb->nh.iph; 91 memcpy(nskb->data, skb->nh.raw, doffset); 92 if (skb_copy_bits(skb, 93 doffset + offset, 94 nskb->data + doffset, 95 frag_size)) 96 BUG(); 97 skb_put(nskb, doffset + frag_size); 98 nskb->ip_summed = CHECKSUM_UNNECESSARY; 99 nskb->dev = skb->dev; 100 nskb->priority = skb->priority; 101 nskb->protocol = skb->protocol; 102 nskb->dst = dst_clone(skb->dst); 103 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 104 nskb->pkt_type = skb->pkt_type; 105 106 th = (struct tcphdr*)(nskb->nh.raw + iph->ihl*4); 107 iph->tot_len = htons(frag_size + doffset); 108 iph->id = htons(id); 109 iph->check = 0; 110 iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl); 111 th->seq = htonl(seq); 112 if (offset + doffset + frag_size < skb->len) 113 th->fin = th->psh = 0; 114 netif_rx(nskb); 115 offset += frag_size; 116 seq += frag_size; 117 id++; 118 } 119 120 dev_kfree_skb(skb); 121 } 122 123 /* 124 * The higher levels take care of making this non-reentrant (it's 125 * called with bh's disabled). 126 */ 127 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev) 128 { 129 struct net_device_stats *lb_stats; 130 131 skb_orphan(skb); 132 133 skb->protocol=eth_type_trans(skb,dev); 134 skb->dev=dev; 135 #ifndef LOOPBACK_MUST_CHECKSUM 136 skb->ip_summed = CHECKSUM_UNNECESSARY; 137 #endif 138 139 if (skb_shinfo(skb)->tso_size) { 140 BUG_ON(skb->protocol != htons(ETH_P_IP)); 141 BUG_ON(skb->nh.iph->protocol != IPPROTO_TCP); 142 143 emulate_large_send_offload(skb); 144 return 0; 145 } 146 147 dev->last_rx = jiffies; 148 149 lb_stats = &per_cpu(loopback_stats, get_cpu()); 150 lb_stats->rx_bytes += skb->len; 151 lb_stats->tx_bytes += skb->len; 152 lb_stats->rx_packets++; 153 lb_stats->tx_packets++; 154 put_cpu(); 155 156 netif_rx(skb); 157 158 return(0); 159 } 160 161 static struct net_device_stats *get_stats(struct net_device *dev) 162 { 163 struct net_device_stats *stats = dev->priv; 164 int i; 165 166 if (!stats) { 167 return NULL; 168 } 169 170 memset(stats, 0, sizeof(struct net_device_stats)); 171 172 for (i=0; i < NR_CPUS; i++) { 173 struct net_device_stats *lb_stats; 174 175 if (!cpu_possible(i)) 176 continue; 177 lb_stats = &per_cpu(loopback_stats, i); 178 stats->rx_bytes += lb_stats->rx_bytes; 179 stats->tx_bytes += lb_stats->tx_bytes; 180 stats->rx_packets += lb_stats->rx_packets; 181 stats->tx_packets += lb_stats->tx_packets; 182 } 183 184 return stats; 185 } 186 187 static u32 loopback_get_link(struct net_device *dev) 188 { 189 return 1; 190 } 191 192 static struct ethtool_ops loopback_ethtool_ops = { 193 .get_link = loopback_get_link, 194 .get_tso = ethtool_op_get_tso, 195 .set_tso = ethtool_op_set_tso, 196 }; 197 198 struct net_device loopback_dev = { 199 .name = "lo", 200 .mtu = (16 * 1024) + 20 + 20 + 12, 201 .hard_start_xmit = loopback_xmit, 202 .hard_header = eth_header, 203 .hard_header_cache = eth_header_cache, 204 .header_cache_update = eth_header_cache_update, 205 .hard_header_len = ETH_HLEN, /* 14 */ 206 .addr_len = ETH_ALEN, /* 6 */ 207 .tx_queue_len = 0, 208 .type = ARPHRD_LOOPBACK, /* 0x0001*/ 209 .rebuild_header = eth_rebuild_header, 210 .flags = IFF_LOOPBACK, 211 .features = NETIF_F_SG|NETIF_F_FRAGLIST 212 |NETIF_F_NO_CSUM|NETIF_F_HIGHDMA 213 |NETIF_F_LLTX, 214 .ethtool_ops = &loopback_ethtool_ops, 215 }; 216 217 /* Setup and register the loopback device. */ 218 int __init loopback_init(void) 219 { 220 struct net_device_stats *stats; 221 222 /* Can survive without statistics */ 223 stats = kmalloc(sizeof(struct net_device_stats), GFP_KERNEL); 224 if (stats) { 225 memset(stats, 0, sizeof(struct net_device_stats)); 226 loopback_dev.priv = stats; 227 loopback_dev.get_stats = &get_stats; 228 } 229 230 return register_netdev(&loopback_dev); 231 }; 232 233 EXPORT_SYMBOL(loopback_dev); 234