drivers/net/loopback.c

   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 #ifdef LOOPBACK_TSO
  72 static void emulate_large_send_offload(struct sk_buff *skb)
  73 {
  74         struct iphdr *iph = skb->nh.iph;
  75         struct tcphdr *th = (struct tcphdr*)(skb->nh.raw + (iph->ihl * 4));
  76         unsigned int doffset = (iph->ihl + th->doff) * 4;
  77         unsigned int mtu = skb_shinfo(skb)->tso_size + doffset;
  78         unsigned int offset = 0;
  79         u32 seq = ntohl(th->seq);
  80         u16 id  = ntohs(iph->id);
  81
  82         while (offset + doffset < skb->len) {
  83                 unsigned int frag_size = min(mtu, skb->len - offset) - doffset;
  84                 struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC);
  85
  86                 if (!nskb)
  87                         break;
  88                 skb_reserve(nskb, 32);
  89                 nskb->mac.raw = nskb->data - 14;
  90                 nskb->nh.raw = nskb->data;
  91                 iph = nskb->nh.iph;
  92                 memcpy(nskb->data, skb->nh.raw, doffset);
  93                 if (skb_copy_bits(skb,
  94                                   doffset + offset,
  95                                   nskb->data + doffset,
  96                                   frag_size))
  97                         BUG();
  98                 skb_put(nskb, doffset + frag_size);
  99                 nskb->ip_summed = CHECKSUM_UNNECESSARY;
 100                 nskb->dev = skb->dev;
 101                 nskb->priority = skb->priority;
 102                 nskb->protocol = skb->protocol;
 103                 nskb->dst = dst_clone(skb->dst);
 104                 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
 105                 nskb->pkt_type = skb->pkt_type;
 106
 107                 th = (struct tcphdr*)(nskb->nh.raw + iph->ihl*4);
 108                 iph->tot_len = htons(frag_size + doffset);
 109                 iph->id = htons(id);
 110                 iph->check = 0;
 111                 iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl);
 112                 th->seq = htonl(seq);
 113                 if (offset + doffset + frag_size < skb->len)
 114                         th->fin = th->psh = 0;
 115                 netif_rx(nskb);
 116                 offset += frag_size;
 117                 seq += frag_size;
 118                 id++;
 119         }
 120
 121         dev_kfree_skb(skb);
 122 }
 123 #endif /* LOOPBACK_TSO */
 124
 125 /*
 126  * The higher levels take care of making this non-reentrant (it's
 127  * called with bh's disabled).
 128  */
 129 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)
 130 {
 131         struct net_device_stats *lb_stats;
 132
 133         skb_orphan(skb);
 134
 135         skb->protocol = eth_type_trans(skb,dev);
 136         skb->dev = dev;
 137 #ifndef LOOPBACK_MUST_CHECKSUM
 138         skb->ip_summed = CHECKSUM_UNNECESSARY;
 139 #endif
 140
 141 #ifdef LOOPBACK_TSO
 142         if (skb_shinfo(skb)->tso_size) {
 143                 BUG_ON(skb->protocol != htons(ETH_P_IP));
 144                 BUG_ON(skb->nh.iph->protocol != IPPROTO_TCP);
 145
 146                 emulate_large_send_offload(skb);
 147                 return 0;
 148         }
 149 #endif
 150         dev->last_rx = jiffies;
 151
 152         lb_stats = &per_cpu(loopback_stats, get_cpu());
 153         lb_stats->rx_bytes += skb->len;
 154         lb_stats->tx_bytes = lb_stats->rx_bytes;
 155         lb_stats->rx_packets++;
 156         lb_stats->tx_packets = lb_stats->rx_packets;
 157         put_cpu();
 158
 159         netif_rx(skb);
 160
 161         return(0);
 162 }
 163
 164 static struct net_device_stats *get_stats(struct net_device *dev)
 165 {
 166         struct net_device_stats *stats = dev->priv;
 167         int i;
 168
 169         if (!stats) {
 170                 return NULL;
 171         }
 172
 173         memset(stats, 0, sizeof(struct net_device_stats));
 174
 175         for_each_possible_cpu(i) {
 176                 struct net_device_stats *lb_stats;
 177
 178                 lb_stats = &per_cpu(loopback_stats, i);
 179                 stats->rx_bytes   += lb_stats->rx_bytes;
 180                 stats->tx_bytes   += lb_stats->tx_bytes;
 181                 stats->rx_packets += lb_stats->rx_packets;
 182                 stats->tx_packets += lb_stats->tx_packets;
 183         }
 184
 185         return stats;
 186 }
 187
 188 static u32 loopback_get_link(struct net_device *dev)
 189 {
 190         return 1;
 191 }
 192
 193 static struct ethtool_ops loopback_ethtool_ops = {
 194         .get_link               = loopback_get_link,
 195         .get_tso                = ethtool_op_get_tso,
 196         .set_tso                = ethtool_op_set_tso,
 197 };
 198
 199 struct net_device loopback_dev = {
 200         .name                   = "lo",
 201         .mtu                    = (16 * 1024) + 20 + 20 + 12,
 202         .hard_start_xmit        = loopback_xmit,
 203         .hard_header            = eth_header,
 204         .hard_header_cache      = eth_header_cache,
 205         .header_cache_update    = eth_header_cache_update,
 206         .hard_header_len        = ETH_HLEN,     /* 14   */
 207         .addr_len               = ETH_ALEN,     /* 6    */
 208         .tx_queue_len           = 0,
 209         .type                   = ARPHRD_LOOPBACK,      /* 0x0001*/
 210         .rebuild_header         = eth_rebuild_header,
 211         .flags                  = IFF_LOOPBACK,
 212         .features               = NETIF_F_SG | NETIF_F_FRAGLIST
 213 #ifdef LOOPBACK_TSO
 214                                   | NETIF_F_TSO
 215 #endif
 216                                   | NETIF_F_NO_CSUM | NETIF_F_HIGHDMA
 217                                   | NETIF_F_LLTX,
 218         .ethtool_ops            = &loopback_ethtool_ops,
 219 };
 220
 221 /* Setup and register the loopback device. */
 222 int __init loopback_init(void)
 223 {
 224         struct net_device_stats *stats;
 225
 226         /* Can survive without statistics */
 227         stats = kmalloc(sizeof(struct net_device_stats), GFP_KERNEL);
 228         if (stats) {
 229                 memset(stats, 0, sizeof(struct net_device_stats));
 230                 loopback_dev.priv = stats;
 231                 loopback_dev.get_stats = &get_stats;
 232         }
 233
 234         return register_netdev(&loopback_dev);
 235 };
 236
 237 EXPORT_SYMBOL(loopback_dev);