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 <linux/uaccess.h>
44 #include <linux/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 <linux/net_tstamp.h>
59 #include <net/net_namespace.h>
60 #include <linux/u64_stats_sync.h>
61
62 struct pcpu_lstats {
63 u64 packets;
64 u64 bytes;
65 struct u64_stats_sync syncp;
66 };
67
68 /* The higher levels take care of making this non-reentrant (it's
69 * called with bh's disabled).
70 */
loopback_xmit(struct sk_buff * skb,struct net_device * dev)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_tx_timestamp(skb);
78
79 /* do not fool net_timestamp_check() with various clock bases */
80 skb->tstamp = 0;
81
82 skb_orphan(skb);
83
84 /* Before queueing this packet to netif_rx(),
85 * make sure dst is refcounted.
86 */
87 skb_dst_force(skb);
88
89 skb->protocol = eth_type_trans(skb, dev);
90
91 /* it's OK to use per_cpu_ptr() because BHs are off */
92 lb_stats = this_cpu_ptr(dev->lstats);
93
94 len = skb->len;
95 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
96 u64_stats_update_begin(&lb_stats->syncp);
97 lb_stats->bytes += len;
98 lb_stats->packets++;
99 u64_stats_update_end(&lb_stats->syncp);
100 }
101
102 return NETDEV_TX_OK;
103 }
104
loopback_get_stats64(struct net_device * dev,struct rtnl_link_stats64 * stats)105 static void loopback_get_stats64(struct net_device *dev,
106 struct rtnl_link_stats64 *stats)
107 {
108 u64 bytes = 0;
109 u64 packets = 0;
110 int i;
111
112 for_each_possible_cpu(i) {
113 const struct pcpu_lstats *lb_stats;
114 u64 tbytes, tpackets;
115 unsigned int start;
116
117 lb_stats = per_cpu_ptr(dev->lstats, i);
118 do {
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));
123 bytes += tbytes;
124 packets += tpackets;
125 }
126 stats->rx_packets = packets;
127 stats->tx_packets = packets;
128 stats->rx_bytes = bytes;
129 stats->tx_bytes = bytes;
130 }
131
always_on(struct net_device * dev)132 static u32 always_on(struct net_device *dev)
133 {
134 return 1;
135 }
136
loopback_get_ts_info(struct net_device * netdev,struct ethtool_ts_info * ts_info)137 static int loopback_get_ts_info(struct net_device *netdev,
138 struct ethtool_ts_info *ts_info)
139 {
140 ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE |
141 SOF_TIMESTAMPING_RX_SOFTWARE |
142 SOF_TIMESTAMPING_SOFTWARE;
143
144 ts_info->phc_index = -1;
145
146 return 0;
147 };
148
149 static const struct ethtool_ops loopback_ethtool_ops = {
150 .get_link = always_on,
151 .get_ts_info = loopback_get_ts_info,
152 };
153
loopback_dev_init(struct net_device * dev)154 static int loopback_dev_init(struct net_device *dev)
155 {
156 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
157 if (!dev->lstats)
158 return -ENOMEM;
159 return 0;
160 }
161
loopback_dev_free(struct net_device * dev)162 static void loopback_dev_free(struct net_device *dev)
163 {
164 dev_net(dev)->loopback_dev = NULL;
165 free_percpu(dev->lstats);
166 }
167
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,
173 };
174
175 /* The loopback device is special. There is only one instance
176 * per network namespace.
177 */
loopback_setup(struct net_device * dev)178 static void loopback_setup(struct net_device *dev)
179 {
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;
187 netif_keep_dst(dev);
188 dev->hw_features = NETIF_F_GSO_SOFTWARE;
189 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
190 | NETIF_F_GSO_SOFTWARE
191 | NETIF_F_HW_CSUM
192 | NETIF_F_RXCSUM
193 | NETIF_F_SCTP_CRC
194 | NETIF_F_HIGHDMA
195 | NETIF_F_LLTX
196 | NETIF_F_NETNS_LOCAL
197 | NETIF_F_VLAN_CHALLENGED
198 | NETIF_F_LOOPBACK;
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;
204 }
205
206 /* Setup and register the loopback device. */
loopback_net_init(struct net * net)207 static __net_init int loopback_net_init(struct net *net)
208 {
209 struct net_device *dev;
210 int err;
211
212 err = -ENOMEM;
213 dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
214 if (!dev)
215 goto out;
216
217 dev_net_set(dev, net);
218 err = register_netdev(dev);
219 if (err)
220 goto out_free_netdev;
221
222 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
223 net->loopback_dev = dev;
224 return 0;
225
226 out_free_netdev:
227 free_netdev(dev);
228 out:
229 if (net_eq(net, &init_net))
230 panic("loopback: Failed to register netdevice: %d\n", err);
231 return err;
232 }
233
234 /* Registered in net/core/dev.c */
235 struct pernet_operations __net_initdata loopback_net_ops = {
236 .init = loopback_net_init,
237 };
238