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.
6 * Pseudo-driver for the loopback interface.
8 * Version: @(#)loopback.c 1.0.4b 08/16/93
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Donald Becker, <becker@scyld.com>
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
20 * Michael Griffith: Don't bother computing the checksums
21 * on packets received on the loopback
23 * Alexey Kuznetsov: Potential hang under some extreme
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.
31 #include <linux/kernel.h>
32 #include <linux/jiffies.h>
33 #include <linux/module.h>
34 #include <linux/interrupt.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>
43 #include <linux/uaccess.h>
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>
52 #include <net/checksum.h>
53 #include <linux/if_ether.h> /* For the statistics structure. */
54 #include <linux/if_arp.h> /* For ARPHRD_ETHER */
56 #include <linux/tcp.h>
57 #include <linux/percpu.h>
58 #include <linux/net_tstamp.h>
59 #include <net/net_namespace.h>
60 #include <linux/u64_stats_sync.h>
65 struct u64_stats_sync syncp;
68 /* The higher levels take care of making this non-reentrant (it's
69 * called with bh's disabled).
71 static netdev_tx_t loopback_xmit(struct sk_buff *skb,
72 struct net_device *dev)
74 struct pcpu_lstats *lb_stats;
77 skb_tx_timestamp(skb);
79 /* do not fool net_timestamp_check() with various clock bases */
84 /* Before queueing this packet to netif_rx(),
85 * make sure dst is refcounted.
89 skb->protocol = eth_type_trans(skb, dev);
91 /* it's OK to use per_cpu_ptr() because BHs are off */
92 lb_stats = this_cpu_ptr(dev->lstats);
95 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
96 u64_stats_update_begin(&lb_stats->syncp);
97 lb_stats->bytes += len;
99 u64_stats_update_end(&lb_stats->syncp);
105 static void loopback_get_stats64(struct net_device *dev,
106 struct rtnl_link_stats64 *stats)
112 for_each_possible_cpu(i) {
113 const struct pcpu_lstats *lb_stats;
114 u64 tbytes, tpackets;
117 lb_stats = per_cpu_ptr(dev->lstats, i);
119 start = u64_stats_fetch_begin_irq(&lb_stats->syncp);
120 tbytes = lb_stats->bytes;
121 tpackets = lb_stats->packets;
122 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
126 stats->rx_packets = packets;
127 stats->tx_packets = packets;
128 stats->rx_bytes = bytes;
129 stats->tx_bytes = bytes;
132 static u32 always_on(struct net_device *dev)
137 static int loopback_get_ts_info(struct net_device *netdev,
138 struct ethtool_ts_info *ts_info)
140 ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE |
141 SOF_TIMESTAMPING_RX_SOFTWARE |
142 SOF_TIMESTAMPING_SOFTWARE;
144 ts_info->phc_index = -1;
149 static const struct ethtool_ops loopback_ethtool_ops = {
150 .get_link = always_on,
151 .get_ts_info = loopback_get_ts_info,
154 static int loopback_dev_init(struct net_device *dev)
156 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
162 static void loopback_dev_free(struct net_device *dev)
164 dev_net(dev)->loopback_dev = NULL;
165 free_percpu(dev->lstats);
168 static const struct net_device_ops loopback_ops = {
169 .ndo_init = loopback_dev_init,
170 .ndo_start_xmit = loopback_xmit,
171 .ndo_get_stats64 = loopback_get_stats64,
172 .ndo_set_mac_address = eth_mac_addr,
175 /* The loopback device is special. There is only one instance
176 * per network namespace.
178 static void loopback_setup(struct net_device *dev)
180 dev->mtu = 64 * 1024;
181 dev->hard_header_len = ETH_HLEN; /* 14 */
182 dev->min_header_len = ETH_HLEN; /* 14 */
183 dev->addr_len = ETH_ALEN; /* 6 */
184 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
185 dev->flags = IFF_LOOPBACK;
186 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
188 dev->hw_features = NETIF_F_GSO_SOFTWARE;
189 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
190 | NETIF_F_GSO_SOFTWARE
196 | NETIF_F_NETNS_LOCAL
197 | NETIF_F_VLAN_CHALLENGED
199 dev->ethtool_ops = &loopback_ethtool_ops;
200 dev->header_ops = ð_header_ops;
201 dev->netdev_ops = &loopback_ops;
202 dev->needs_free_netdev = true;
203 dev->priv_destructor = loopback_dev_free;
206 /* Setup and register the loopback device. */
207 static __net_init int loopback_net_init(struct net *net)
209 struct net_device *dev;
213 dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
217 dev_net_set(dev, net);
218 err = register_netdev(dev);
220 goto out_free_netdev;
222 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
223 net->loopback_dev = dev;
229 if (net_eq(net, &init_net))
230 panic("loopback: Failed to register netdevice: %d\n", err);
234 /* Registered in net/core/dev.c */
235 struct pernet_operations __net_initdata loopback_net_ops = {
236 .init = loopback_net_init,