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 struct pcpu_lstats { 62 unsigned long packets; 63 unsigned long bytes; 64 }; 65 static 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 76 static void emulate_large_send_offload(struct sk_buff *skb) 77 { 78 struct iphdr *iph = skb->nh.iph; 79 struct tcphdr *th = (struct tcphdr*)(skb->nh.raw + (iph->ihl * 4)); 80 unsigned int doffset = (iph->ihl + th->doff) * 4; 81 unsigned int mtu = skb_shinfo(skb)->gso_size + doffset; 82 unsigned int offset = 0; 83 u32 seq = ntohl(th->seq); 84 u16 id = ntohs(iph->id); 85 86 while (offset + doffset < skb->len) { 87 unsigned int frag_size = min(mtu, skb->len - offset) - doffset; 88 struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC); 89 90 if (!nskb) 91 break; 92 skb_reserve(nskb, 32); 93 nskb->mac.raw = nskb->data - 14; 94 nskb->nh.raw = nskb->data; 95 iph = nskb->nh.iph; 96 memcpy(nskb->data, skb->nh.raw, doffset); 97 if (skb_copy_bits(skb, 98 doffset + offset, 99 nskb->data + doffset, 100 frag_size)) 101 BUG(); 102 skb_put(nskb, doffset + frag_size); 103 nskb->ip_summed = CHECKSUM_UNNECESSARY; 104 nskb->dev = skb->dev; 105 nskb->priority = skb->priority; 106 nskb->protocol = skb->protocol; 107 nskb->dst = dst_clone(skb->dst); 108 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 109 nskb->pkt_type = skb->pkt_type; 110 111 th = (struct tcphdr*)(nskb->nh.raw + iph->ihl*4); 112 iph->tot_len = htons(frag_size + doffset); 113 iph->id = htons(id); 114 iph->check = 0; 115 iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl); 116 th->seq = htonl(seq); 117 if (offset + doffset + frag_size < skb->len) 118 th->fin = th->psh = 0; 119 netif_rx(nskb); 120 offset += frag_size; 121 seq += frag_size; 122 id++; 123 } 124 125 dev_kfree_skb(skb); 126 } 127 #endif /* LOOPBACK_TSO */ 128 129 /* 130 * The higher levels take care of making this non-reentrant (it's 131 * called with bh's disabled). 132 */ 133 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev) 134 { 135 struct pcpu_lstats *lb_stats; 136 137 skb_orphan(skb); 138 139 skb->protocol = eth_type_trans(skb,dev); 140 skb->dev = dev; 141 #ifndef LOOPBACK_MUST_CHECKSUM 142 skb->ip_summed = CHECKSUM_UNNECESSARY; 143 #endif 144 145 #ifdef LOOPBACK_TSO 146 if (skb_is_gso(skb)) { 147 BUG_ON(skb->protocol != htons(ETH_P_IP)); 148 BUG_ON(skb->nh.iph->protocol != IPPROTO_TCP); 149 150 emulate_large_send_offload(skb); 151 return 0; 152 } 153 #endif 154 dev->last_rx = jiffies; 155 156 /* it's OK to use __get_cpu_var() because BHs are off */ 157 lb_stats = &__get_cpu_var(pcpu_lstats); 158 lb_stats->bytes += skb->len; 159 lb_stats->packets++; 160 161 netif_rx(skb); 162 163 return 0; 164 } 165 166 static struct net_device_stats loopback_stats; 167 168 static struct net_device_stats *get_stats(struct net_device *dev) 169 { 170 struct net_device_stats *stats = &loopback_stats; 171 unsigned long bytes = 0; 172 unsigned long packets = 0; 173 int i; 174 175 for_each_possible_cpu(i) { 176 const struct pcpu_lstats *lb_stats; 177 178 lb_stats = &per_cpu(pcpu_lstats, i); 179 bytes += lb_stats->bytes; 180 packets += lb_stats->packets; 181 } 182 stats->rx_packets = packets; 183 stats->tx_packets = packets; 184 stats->rx_bytes = bytes; 185 stats->tx_bytes = bytes; 186 return stats; 187 } 188 189 static u32 always_on(struct net_device *dev) 190 { 191 return 1; 192 } 193 194 static const struct ethtool_ops loopback_ethtool_ops = { 195 .get_link = always_on, 196 .get_tso = ethtool_op_get_tso, 197 .set_tso = ethtool_op_set_tso, 198 .get_tx_csum = always_on, 199 .get_sg = always_on, 200 .get_rx_csum = always_on, 201 }; 202 203 /* 204 * The loopback device is special. There is only one instance and 205 * it is statically allocated. Don't do this for other devices. 206 */ 207 struct net_device loopback_dev = { 208 .name = "lo", 209 .get_stats = &get_stats, 210 .priv = &loopback_stats, 211 .mtu = (16 * 1024) + 20 + 20 + 12, 212 .hard_start_xmit = loopback_xmit, 213 .hard_header = eth_header, 214 .hard_header_cache = eth_header_cache, 215 .header_cache_update = eth_header_cache_update, 216 .hard_header_len = ETH_HLEN, /* 14 */ 217 .addr_len = ETH_ALEN, /* 6 */ 218 .tx_queue_len = 0, 219 .type = ARPHRD_LOOPBACK, /* 0x0001*/ 220 .rebuild_header = eth_rebuild_header, 221 .flags = IFF_LOOPBACK, 222 .features = NETIF_F_SG | NETIF_F_FRAGLIST 223 #ifdef LOOPBACK_TSO 224 | NETIF_F_TSO 225 #endif 226 | NETIF_F_NO_CSUM | NETIF_F_HIGHDMA 227 | NETIF_F_LLTX, 228 .ethtool_ops = &loopback_ethtool_ops, 229 }; 230 231 /* Setup and register the loopback device. */ 232 static int __init loopback_init(void) 233 { 234 return register_netdev(&loopback_dev); 235 }; 236 237 module_init(loopback_init); 238 239 EXPORT_SYMBOL(loopback_dev); 240