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 #include <net/net_namespace.h> 61 62 struct pcpu_lstats { 63 unsigned long packets; 64 unsigned long bytes; 65 }; 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 = 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 */ 135 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev) 136 { 137 struct pcpu_lstats *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 per_cpu_ptr() because BHs are off */ 158 pcpu_lstats = netdev_priv(dev); 159 lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id()); 160 lb_stats->bytes += skb->len; 161 lb_stats->packets++; 162 163 netif_rx(skb); 164 165 return 0; 166 } 167 168 static struct net_device_stats *get_stats(struct net_device *dev) 169 { 170 const struct pcpu_lstats *pcpu_lstats; 171 struct net_device_stats *stats = &dev->stats; 172 unsigned long bytes = 0; 173 unsigned long packets = 0; 174 int i; 175 176 pcpu_lstats = netdev_priv(dev); 177 for_each_possible_cpu(i) { 178 const struct pcpu_lstats *lb_stats; 179 180 lb_stats = per_cpu_ptr(pcpu_lstats, i); 181 bytes += lb_stats->bytes; 182 packets += lb_stats->packets; 183 } 184 stats->rx_packets = packets; 185 stats->tx_packets = packets; 186 stats->rx_bytes = bytes; 187 stats->tx_bytes = bytes; 188 return stats; 189 } 190 191 static u32 always_on(struct net_device *dev) 192 { 193 return 1; 194 } 195 196 static const struct ethtool_ops loopback_ethtool_ops = { 197 .get_link = always_on, 198 .set_tso = ethtool_op_set_tso, 199 .get_tx_csum = always_on, 200 .get_sg = always_on, 201 .get_rx_csum = always_on, 202 }; 203 204 static int loopback_dev_init(struct net_device *dev) 205 { 206 struct pcpu_lstats *lstats; 207 208 lstats = alloc_percpu(struct pcpu_lstats); 209 if (!lstats) 210 return -ENOMEM; 211 212 dev->priv = lstats; 213 return 0; 214 } 215 216 static void loopback_dev_free(struct net_device *dev) 217 { 218 struct pcpu_lstats *lstats = netdev_priv(dev); 219 220 free_percpu(lstats); 221 free_netdev(dev); 222 } 223 224 /* 225 * The loopback device is special. There is only one instance 226 * per network namespace. 227 */ 228 static void loopback_setup(struct net_device *dev) 229 { 230 dev->get_stats = &get_stats; 231 dev->mtu = (16 * 1024) + 20 + 20 + 12; 232 dev->hard_start_xmit = loopback_xmit; 233 dev->hard_header_len = ETH_HLEN; /* 14 */ 234 dev->addr_len = ETH_ALEN; /* 6 */ 235 dev->tx_queue_len = 0; 236 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 237 dev->flags = IFF_LOOPBACK; 238 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 239 #ifdef LOOPBACK_TSO 240 | NETIF_F_TSO 241 #endif 242 | NETIF_F_NO_CSUM 243 | NETIF_F_HIGHDMA 244 | NETIF_F_LLTX 245 | NETIF_F_NETNS_LOCAL, 246 dev->ethtool_ops = &loopback_ethtool_ops; 247 dev->header_ops = ð_header_ops; 248 dev->init = loopback_dev_init; 249 dev->destructor = loopback_dev_free; 250 } 251 252 /* Setup and register the loopback device. */ 253 static __net_init int loopback_net_init(struct net *net) 254 { 255 struct net_device *dev; 256 int err; 257 258 err = -ENOMEM; 259 dev = alloc_netdev(0, "lo", loopback_setup); 260 if (!dev) 261 goto out; 262 263 dev->nd_net = net; 264 err = register_netdev(dev); 265 if (err) 266 goto out_free_netdev; 267 268 net->loopback_dev = dev; 269 return 0; 270 271 272 out_free_netdev: 273 free_netdev(dev); 274 out: 275 if (net == &init_net) 276 panic("loopback: Failed to register netdevice: %d\n", err); 277 return err; 278 } 279 280 static __net_exit void loopback_net_exit(struct net *net) 281 { 282 struct net_device *dev = net->loopback_dev; 283 284 unregister_netdev(dev); 285 } 286 287 static struct pernet_operations __net_initdata loopback_net_ops = { 288 .init = loopback_net_init, 289 .exit = loopback_net_exit, 290 }; 291 292 static int __init loopback_init(void) 293 { 294 return register_pernet_device(&loopback_net_ops); 295 } 296 297 /* Loopback is special. It should be initialized before any other network 298 * device and network subsystem. 299 */ 300 fs_initcall(loopback_init); 301