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Linux/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 
 43 #include <asm/uaccess.h>
 44 #include <asm/io.h>
 45 
 46 #include <linux/inet.h>
 47 #include <linux/netdevice.h>
 48 #include <linux/etherdevice.h>
 49 #include <linux/skbuff.h>
 50 #include <linux/ethtool.h>
 51 #include <net/sock.h>
 52 #include <net/checksum.h>
 53 #include <linux/if_ether.h>     /* For the statistics structure. */
 54 #include <linux/if_arp.h>       /* For ARPHRD_ETHER */
 55 #include <linux/ip.h>
 56 #include <linux/tcp.h>
 57 #include <linux/percpu.h>
 58 #include <net/net_namespace.h>
 59 #include <linux/u64_stats_sync.h>
 60 
 61 struct pcpu_lstats {
 62         u64                     packets;
 63         u64                     bytes;
 64         struct u64_stats_sync   syncp;
 65 };
 66 
 67 /*
 68  * The higher levels take care of making this non-reentrant (it's
 69  * called with bh's disabled).
 70  */
 71 static netdev_tx_t loopback_xmit(struct sk_buff *skb,
 72                                  struct net_device *dev)
 73 {
 74         struct pcpu_lstats *lb_stats;
 75         int len;
 76 
 77         skb_orphan(skb);
 78 
 79         /* Before queueing this packet to netif_rx(),
 80          * make sure dst is refcounted.
 81          */
 82         skb_dst_force(skb);
 83 
 84         skb->protocol = eth_type_trans(skb, dev);
 85 
 86         /* it's OK to use per_cpu_ptr() because BHs are off */
 87         lb_stats = this_cpu_ptr(dev->lstats);
 88 
 89         len = skb->len;
 90         if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
 91                 u64_stats_update_begin(&lb_stats->syncp);
 92                 lb_stats->bytes += len;
 93                 lb_stats->packets++;
 94                 u64_stats_update_end(&lb_stats->syncp);
 95         }
 96 
 97         return NETDEV_TX_OK;
 98 }
 99 
100 static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
101                                                       struct rtnl_link_stats64 *stats)
102 {
103         u64 bytes = 0;
104         u64 packets = 0;
105         int i;
106 
107         for_each_possible_cpu(i) {
108                 const struct pcpu_lstats *lb_stats;
109                 u64 tbytes, tpackets;
110                 unsigned int start;
111 
112                 lb_stats = per_cpu_ptr(dev->lstats, i);
113                 do {
114                         start = u64_stats_fetch_begin_irq(&lb_stats->syncp);
115                         tbytes = lb_stats->bytes;
116                         tpackets = lb_stats->packets;
117                 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
118                 bytes   += tbytes;
119                 packets += tpackets;
120         }
121         stats->rx_packets = packets;
122         stats->tx_packets = packets;
123         stats->rx_bytes   = bytes;
124         stats->tx_bytes   = bytes;
125         return stats;
126 }
127 
128 static u32 always_on(struct net_device *dev)
129 {
130         return 1;
131 }
132 
133 static const struct ethtool_ops loopback_ethtool_ops = {
134         .get_link               = always_on,
135 };
136 
137 static int loopback_dev_init(struct net_device *dev)
138 {
139         dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
140         if (!dev->lstats)
141                 return -ENOMEM;
142         return 0;
143 }
144 
145 static void loopback_dev_free(struct net_device *dev)
146 {
147         dev_net(dev)->loopback_dev = NULL;
148         free_percpu(dev->lstats);
149         free_netdev(dev);
150 }
151 
152 static const struct net_device_ops loopback_ops = {
153         .ndo_init      = loopback_dev_init,
154         .ndo_start_xmit= loopback_xmit,
155         .ndo_get_stats64 = loopback_get_stats64,
156         .ndo_set_mac_address = eth_mac_addr,
157 };
158 
159 /*
160  * The loopback device is special. There is only one instance
161  * per network namespace.
162  */
163 static void loopback_setup(struct net_device *dev)
164 {
165         dev->mtu                = 64 * 1024;
166         dev->hard_header_len    = ETH_HLEN;     /* 14   */
167         dev->addr_len           = ETH_ALEN;     /* 6    */
168         dev->tx_queue_len       = 0;
169         dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
170         dev->flags              = IFF_LOOPBACK;
171         dev->priv_flags         |= IFF_LIVE_ADDR_CHANGE;
172         dev->priv_flags        &= ~IFF_XMIT_DST_RELEASE;
173         dev->hw_features        = NETIF_F_ALL_TSO | NETIF_F_UFO;
174         dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
175                 | NETIF_F_ALL_TSO
176                 | NETIF_F_UFO
177                 | NETIF_F_HW_CSUM
178                 | NETIF_F_RXCSUM
179                 | NETIF_F_SCTP_CSUM
180                 | NETIF_F_HIGHDMA
181                 | NETIF_F_LLTX
182                 | NETIF_F_NETNS_LOCAL
183                 | NETIF_F_VLAN_CHALLENGED
184                 | NETIF_F_LOOPBACK;
185         dev->ethtool_ops        = &loopback_ethtool_ops;
186         dev->header_ops         = &eth_header_ops;
187         dev->netdev_ops         = &loopback_ops;
188         dev->destructor         = loopback_dev_free;
189 }
190 
191 /* Setup and register the loopback device. */
192 static __net_init int loopback_net_init(struct net *net)
193 {
194         struct net_device *dev;
195         int err;
196 
197         err = -ENOMEM;
198         dev = alloc_netdev(0, "lo", loopback_setup);
199         if (!dev)
200                 goto out;
201 
202         dev_net_set(dev, net);
203         err = register_netdev(dev);
204         if (err)
205                 goto out_free_netdev;
206 
207         BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
208         net->loopback_dev = dev;
209         return 0;
210 
211 
212 out_free_netdev:
213         free_netdev(dev);
214 out:
215         if (net_eq(net, &init_net))
216                 panic("loopback: Failed to register netdevice: %d\n", err);
217         return err;
218 }
219 
220 /* Registered in net/core/dev.c */
221 struct pernet_operations __net_initdata loopback_net_ops = {
222        .init = loopback_net_init,
223 };
224 

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