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 /* KISS: just allocate small chunks and copy bits. 68 * 69 * So, in fact, this is documentation, explaining what we expect 70 * of largesending device modulo TCP checksum, which is ignored for loopback. 71 */ 72 73 #ifdef LOOPBACK_TSO 74 static void emulate_large_send_offload(struct sk_buff *skb) 75 { 76 struct iphdr *iph = ip_hdr(skb); 77 struct tcphdr *th = (struct tcphdr *)(skb_network_header(skb) + 78 (iph->ihl * 4)); 79 unsigned int doffset = (iph->ihl + th->doff) * 4; 80 unsigned int mtu = skb_shinfo(skb)->gso_size + doffset; 81 unsigned int offset = 0; 82 u32 seq = ntohl(th->seq); 83 u16 id = ntohs(iph->id); 84 85 while (offset + doffset < skb->len) { 86 unsigned int frag_size = min(mtu, skb->len - offset) - doffset; 87 struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC); 88 89 if (!nskb) 90 break; 91 skb_reserve(nskb, 32); 92 skb_set_mac_header(nskb, -ETH_HLEN); 93 skb_reset_network_header(nskb); 94 iph = ip_hdr(nskb); 95 skb_copy_to_linear_data(nskb, skb_network_header(skb), 96 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 *)(skb_network_header(nskb) + 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 *pcpu_lstats, *lb_stats; 136 137 skb_orphan(skb); 138 139 skb->protocol = eth_type_trans(skb,dev); 140 #ifndef LOOPBACK_MUST_CHECKSUM 141 skb->ip_summed = CHECKSUM_UNNECESSARY; 142 #endif 143 144 #ifdef LOOPBACK_TSO 145 if (skb_is_gso(skb)) { 146 BUG_ON(skb->protocol != htons(ETH_P_IP)); 147 BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP); 148 149 emulate_large_send_offload(skb); 150 return 0; 151 } 152 #endif 153 dev->last_rx = jiffies; 154 155 /* it's OK to use per_cpu_ptr() because BHs are off */ 156 pcpu_lstats = netdev_priv(dev); 157 lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id()); 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 *get_stats(struct net_device *dev) 167 { 168 const struct pcpu_lstats *pcpu_lstats; 169 struct net_device_stats *stats = &dev->stats; 170 unsigned long bytes = 0; 171 unsigned long packets = 0; 172 int i; 173 174 pcpu_lstats = netdev_priv(dev); 175 for_each_possible_cpu(i) { 176 const struct pcpu_lstats *lb_stats; 177 178 lb_stats = per_cpu_ptr(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 .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 static int loopback_dev_init(struct net_device *dev) 203 { 204 struct pcpu_lstats *lstats; 205 206 lstats = alloc_percpu(struct pcpu_lstats); 207 if (!lstats) 208 return -ENOMEM; 209 210 dev->priv = lstats; 211 return 0; 212 } 213 214 static void loopback_dev_free(struct net_device *dev) 215 { 216 struct pcpu_lstats *lstats = netdev_priv(dev); 217 218 free_percpu(lstats); 219 free_netdev(dev); 220 } 221 222 /* 223 * The loopback device is special. There is only one instance 224 * per network namespace. 225 */ 226 static void loopback_setup(struct net_device *dev) 227 { 228 dev->get_stats = &get_stats; 229 dev->mtu = (16 * 1024) + 20 + 20 + 12; 230 dev->hard_start_xmit = loopback_xmit; 231 dev->hard_header_len = ETH_HLEN; /* 14 */ 232 dev->addr_len = ETH_ALEN; /* 6 */ 233 dev->tx_queue_len = 0; 234 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 235 dev->flags = IFF_LOOPBACK; 236 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 237 #ifdef LOOPBACK_TSO 238 | NETIF_F_TSO 239 #endif 240 | NETIF_F_NO_CSUM 241 | NETIF_F_HIGHDMA 242 | NETIF_F_LLTX 243 | NETIF_F_NETNS_LOCAL; 244 dev->ethtool_ops = &loopback_ethtool_ops; 245 dev->header_ops = ð_header_ops; 246 dev->init = loopback_dev_init; 247 dev->destructor = loopback_dev_free; 248 } 249 250 /* Setup and register the loopback device. */ 251 static __net_init int loopback_net_init(struct net *net) 252 { 253 struct net_device *dev; 254 int err; 255 256 err = -ENOMEM; 257 dev = alloc_netdev(0, "lo", loopback_setup); 258 if (!dev) 259 goto out; 260 261 dev_net_set(dev, net); 262 err = register_netdev(dev); 263 if (err) 264 goto out_free_netdev; 265 266 net->loopback_dev = dev; 267 return 0; 268 269 270 out_free_netdev: 271 free_netdev(dev); 272 out: 273 if (net == &init_net) 274 panic("loopback: Failed to register netdevice: %d\n", err); 275 return err; 276 } 277 278 static __net_exit void loopback_net_exit(struct net *net) 279 { 280 struct net_device *dev = net->loopback_dev; 281 282 unregister_netdev(dev); 283 } 284 285 static struct pernet_operations __net_initdata loopback_net_ops = { 286 .init = loopback_net_init, 287 .exit = loopback_net_exit, 288 }; 289 290 static int __init loopback_init(void) 291 { 292 return register_pernet_device(&loopback_net_ops); 293 } 294 295 /* Loopback is special. It should be initialized before any other network 296 * device and network subsystem. 297 */ 298 fs_initcall(loopback_init); 299