Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-or-later
2 : /*
3 : * INET An implementation of the TCP/IP protocol suite for the LINUX
4 : * operating system. INET is implemented using the BSD Socket
5 : * interface as the means of communication with the user level.
6 : *
7 : * Pseudo-driver for the loopback interface.
8 : *
9 : * Version: @(#)loopback.c 1.0.4b 08/16/93
10 : *
11 : * Authors: Ross Biro
12 : * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
13 : * Donald Becker, <becker@scyld.com>
14 : *
15 : * Alan Cox : Fixed oddments for NET3.014
16 : * Alan Cox : Rejig for NET3.029 snap #3
17 : * Alan Cox : Fixed NET3.029 bugs and sped up
18 : * Larry McVoy : Tiny tweak to double performance
19 : * Alan Cox : Backed out LMV's tweak - the linux mm
20 : * can't take it...
21 : * Michael Griffith: Don't bother computing the checksums
22 : * on packets received on the loopback
23 : * interface.
24 : * Alexey Kuznetsov: Potential hang under some extreme
25 : * cases removed.
26 : */
27 : #include <linux/kernel.h>
28 : #include <linux/jiffies.h>
29 : #include <linux/module.h>
30 : #include <linux/interrupt.h>
31 : #include <linux/fs.h>
32 : #include <linux/types.h>
33 : #include <linux/string.h>
34 : #include <linux/socket.h>
35 : #include <linux/errno.h>
36 : #include <linux/fcntl.h>
37 : #include <linux/in.h>
38 :
39 : #include <linux/uaccess.h>
40 : #include <linux/io.h>
41 :
42 : #include <linux/inet.h>
43 : #include <linux/netdevice.h>
44 : #include <linux/etherdevice.h>
45 : #include <linux/skbuff.h>
46 : #include <linux/ethtool.h>
47 : #include <net/sock.h>
48 : #include <net/checksum.h>
49 : #include <linux/if_ether.h> /* For the statistics structure. */
50 : #include <linux/if_arp.h> /* For ARPHRD_ETHER */
51 : #include <linux/ip.h>
52 : #include <linux/tcp.h>
53 : #include <linux/percpu.h>
54 : #include <linux/net_tstamp.h>
55 : #include <net/net_namespace.h>
56 : #include <linux/u64_stats_sync.h>
57 :
58 : /* blackhole_netdev - a device used for dsts that are marked expired!
59 : * This is global device (instead of per-net-ns) since it's not needed
60 : * to be per-ns and gets initialized at boot time.
61 : */
62 : struct net_device *blackhole_netdev;
63 : EXPORT_SYMBOL(blackhole_netdev);
64 :
65 : /* The higher levels take care of making this non-reentrant (it's
66 : * called with bh's disabled).
67 : */
68 0 : static netdev_tx_t loopback_xmit(struct sk_buff *skb,
69 : struct net_device *dev)
70 : {
71 0 : int len;
72 :
73 0 : skb_tx_timestamp(skb);
74 :
75 : /* do not fool net_timestamp_check() with various clock bases */
76 0 : skb->tstamp = 0;
77 :
78 0 : skb_orphan(skb);
79 :
80 : /* Before queueing this packet to netif_rx(),
81 : * make sure dst is refcounted.
82 : */
83 0 : skb_dst_force(skb);
84 :
85 0 : skb->protocol = eth_type_trans(skb, dev);
86 :
87 0 : len = skb->len;
88 0 : if (likely(netif_rx(skb) == NET_RX_SUCCESS))
89 0 : dev_lstats_add(dev, len);
90 :
91 0 : return NETDEV_TX_OK;
92 : }
93 :
94 8 : void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes)
95 : {
96 8 : int i;
97 :
98 8 : *packets = 0;
99 8 : *bytes = 0;
100 :
101 40 : for_each_possible_cpu(i) {
102 32 : const struct pcpu_lstats *lb_stats;
103 32 : u64 tbytes, tpackets;
104 32 : unsigned int start;
105 :
106 32 : lb_stats = per_cpu_ptr(dev->lstats, i);
107 32 : do {
108 32 : start = u64_stats_fetch_begin_irq(&lb_stats->syncp);
109 32 : tpackets = u64_stats_read(&lb_stats->packets);
110 32 : tbytes = u64_stats_read(&lb_stats->bytes);
111 32 : } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
112 32 : *bytes += tbytes;
113 32 : *packets += tpackets;
114 : }
115 8 : }
116 : EXPORT_SYMBOL(dev_lstats_read);
117 :
118 8 : static void loopback_get_stats64(struct net_device *dev,
119 : struct rtnl_link_stats64 *stats)
120 : {
121 8 : u64 packets, bytes;
122 :
123 8 : dev_lstats_read(dev, &packets, &bytes);
124 :
125 8 : stats->rx_packets = packets;
126 8 : stats->tx_packets = packets;
127 8 : stats->rx_bytes = bytes;
128 8 : stats->tx_bytes = bytes;
129 8 : }
130 :
131 0 : static u32 always_on(struct net_device *dev)
132 : {
133 0 : return 1;
134 : }
135 :
136 : static const struct ethtool_ops loopback_ethtool_ops = {
137 : .get_link = always_on,
138 : .get_ts_info = ethtool_op_get_ts_info,
139 : };
140 :
141 1 : static int loopback_dev_init(struct net_device *dev)
142 : {
143 5 : dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
144 1 : if (!dev->lstats)
145 0 : return -ENOMEM;
146 : return 0;
147 : }
148 :
149 0 : static void loopback_dev_free(struct net_device *dev)
150 : {
151 0 : dev_net(dev)->loopback_dev = NULL;
152 0 : free_percpu(dev->lstats);
153 0 : }
154 :
155 : static const struct net_device_ops loopback_ops = {
156 : .ndo_init = loopback_dev_init,
157 : .ndo_start_xmit = loopback_xmit,
158 : .ndo_get_stats64 = loopback_get_stats64,
159 : .ndo_set_mac_address = eth_mac_addr,
160 : };
161 :
162 2 : static void gen_lo_setup(struct net_device *dev,
163 : unsigned int mtu,
164 : const struct ethtool_ops *eth_ops,
165 : const struct header_ops *hdr_ops,
166 : const struct net_device_ops *dev_ops,
167 : void (*dev_destructor)(struct net_device *dev))
168 : {
169 2 : dev->mtu = mtu;
170 2 : dev->hard_header_len = ETH_HLEN; /* 14 */
171 2 : dev->min_header_len = ETH_HLEN; /* 14 */
172 2 : dev->addr_len = ETH_ALEN; /* 6 */
173 2 : dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
174 2 : dev->flags = IFF_LOOPBACK;
175 2 : dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
176 2 : netif_keep_dst(dev);
177 2 : dev->hw_features = NETIF_F_GSO_SOFTWARE;
178 2 : dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
179 : | NETIF_F_GSO_SOFTWARE
180 : | NETIF_F_HW_CSUM
181 : | NETIF_F_RXCSUM
182 : | NETIF_F_SCTP_CRC
183 : | NETIF_F_HIGHDMA
184 : | NETIF_F_LLTX
185 : | NETIF_F_NETNS_LOCAL
186 : | NETIF_F_VLAN_CHALLENGED
187 : | NETIF_F_LOOPBACK;
188 2 : dev->ethtool_ops = eth_ops;
189 2 : dev->header_ops = hdr_ops;
190 2 : dev->netdev_ops = dev_ops;
191 2 : dev->needs_free_netdev = true;
192 2 : dev->priv_destructor = dev_destructor;
193 : }
194 :
195 : /* The loopback device is special. There is only one instance
196 : * per network namespace.
197 : */
198 1 : static void loopback_setup(struct net_device *dev)
199 : {
200 1 : gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, ð_header_ops,
201 : &loopback_ops, loopback_dev_free);
202 1 : }
203 :
204 : /* Setup and register the loopback device. */
205 1 : static __net_init int loopback_net_init(struct net *net)
206 : {
207 1 : struct net_device *dev;
208 1 : int err;
209 :
210 1 : err = -ENOMEM;
211 1 : dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
212 1 : if (!dev)
213 0 : goto out;
214 :
215 1 : dev_net_set(dev, net);
216 1 : err = register_netdev(dev);
217 1 : if (err)
218 0 : goto out_free_netdev;
219 :
220 1 : BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
221 1 : net->loopback_dev = dev;
222 1 : return 0;
223 :
224 0 : out_free_netdev:
225 0 : free_netdev(dev);
226 0 : out:
227 0 : if (net_eq(net, &init_net))
228 0 : panic("loopback: Failed to register netdevice: %d\n", err);
229 : return err;
230 : }
231 :
232 : /* Registered in net/core/dev.c */
233 : struct pernet_operations __net_initdata loopback_net_ops = {
234 : .init = loopback_net_init,
235 : };
236 :
237 : /* blackhole netdevice */
238 0 : static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb,
239 : struct net_device *dev)
240 : {
241 0 : kfree_skb(skb);
242 0 : net_warn_ratelimited("%s(): Dropping skb.\n", __func__);
243 0 : return NETDEV_TX_OK;
244 : }
245 :
246 : static const struct net_device_ops blackhole_netdev_ops = {
247 : .ndo_start_xmit = blackhole_netdev_xmit,
248 : };
249 :
250 : /* This is a dst-dummy device used specifically for invalidated
251 : * DSTs and unlike loopback, this is not per-ns.
252 : */
253 1 : static void blackhole_netdev_setup(struct net_device *dev)
254 : {
255 1 : gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL);
256 1 : }
257 :
258 : /* Setup and register the blackhole_netdev. */
259 1 : static int __init blackhole_netdev_init(void)
260 : {
261 1 : blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN,
262 : blackhole_netdev_setup);
263 1 : if (!blackhole_netdev)
264 : return -ENOMEM;
265 :
266 1 : rtnl_lock();
267 1 : dev_init_scheduler(blackhole_netdev);
268 1 : dev_activate(blackhole_netdev);
269 1 : rtnl_unlock();
270 :
271 1 : blackhole_netdev->flags |= IFF_UP | IFF_RUNNING;
272 1 : dev_net_set(blackhole_netdev, &init_net);
273 :
274 1 : return 0;
275 : }
276 :
277 : device_initcall(blackhole_netdev_init);
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