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/sch_generic.h> |
48 | #include <net/sock.h> |
49 | #include <net/checksum.h> |
50 | #include <linux/if_ether.h> /* For the statistics structure. */ |
51 | #include <linux/if_arp.h> /* For ARPHRD_ETHER */ |
52 | #include <linux/ip.h> |
53 | #include <linux/tcp.h> |
54 | #include <linux/percpu.h> |
55 | #include <linux/net_tstamp.h> |
56 | #include <net/net_namespace.h> |
57 | #include <linux/u64_stats_sync.h> |
58 | |
59 | /* blackhole_netdev - a device used for dsts that are marked expired! |
60 | * This is global device (instead of per-net-ns) since it's not needed |
61 | * to be per-ns and gets initialized at boot time. |
62 | */ |
63 | struct net_device *blackhole_netdev; |
64 | EXPORT_SYMBOL(blackhole_netdev); |
65 | |
66 | /* The higher levels take care of making this non-reentrant (it's |
67 | * called with bh's disabled). |
68 | */ |
69 | static netdev_tx_t loopback_xmit(struct sk_buff *skb, |
70 | struct net_device *dev) |
71 | { |
72 | int len; |
73 | |
74 | skb_tx_timestamp(skb); |
75 | |
76 | /* do not fool net_timestamp_check() with various clock bases */ |
77 | skb_clear_tstamp(skb); |
78 | |
79 | skb_orphan(skb); |
80 | |
81 | /* Before queueing this packet to __netif_rx(), |
82 | * make sure dst is refcounted. |
83 | */ |
84 | skb_dst_force(skb); |
85 | |
86 | skb->protocol = eth_type_trans(skb, dev); |
87 | |
88 | len = skb->len; |
89 | if (likely(__netif_rx(skb) == NET_RX_SUCCESS)) |
90 | dev_lstats_add(dev, len); |
91 | |
92 | return NETDEV_TX_OK; |
93 | } |
94 | |
95 | void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes) |
96 | { |
97 | int i; |
98 | |
99 | *packets = 0; |
100 | *bytes = 0; |
101 | |
102 | for_each_possible_cpu(i) { |
103 | const struct pcpu_lstats *lb_stats; |
104 | u64 tbytes, tpackets; |
105 | unsigned int start; |
106 | |
107 | lb_stats = per_cpu_ptr(dev->lstats, i); |
108 | do { |
109 | start = u64_stats_fetch_begin(syncp: &lb_stats->syncp); |
110 | tpackets = u64_stats_read(p: &lb_stats->packets); |
111 | tbytes = u64_stats_read(p: &lb_stats->bytes); |
112 | } while (u64_stats_fetch_retry(syncp: &lb_stats->syncp, start)); |
113 | *bytes += tbytes; |
114 | *packets += tpackets; |
115 | } |
116 | } |
117 | EXPORT_SYMBOL(dev_lstats_read); |
118 | |
119 | static void loopback_get_stats64(struct net_device *dev, |
120 | struct rtnl_link_stats64 *stats) |
121 | { |
122 | u64 packets, bytes; |
123 | |
124 | dev_lstats_read(dev, &packets, &bytes); |
125 | |
126 | stats->rx_packets = packets; |
127 | stats->tx_packets = packets; |
128 | stats->rx_bytes = bytes; |
129 | stats->tx_bytes = bytes; |
130 | } |
131 | |
132 | static u32 always_on(struct net_device *dev) |
133 | { |
134 | return 1; |
135 | } |
136 | |
137 | static const struct ethtool_ops loopback_ethtool_ops = { |
138 | .get_link = always_on, |
139 | .get_ts_info = ethtool_op_get_ts_info, |
140 | }; |
141 | |
142 | static int loopback_dev_init(struct net_device *dev) |
143 | { |
144 | dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats); |
145 | if (!dev->lstats) |
146 | return -ENOMEM; |
147 | return 0; |
148 | } |
149 | |
150 | static void loopback_dev_free(struct net_device *dev) |
151 | { |
152 | dev_net(dev)->loopback_dev = NULL; |
153 | free_percpu(pdata: dev->lstats); |
154 | } |
155 | |
156 | static const struct net_device_ops loopback_ops = { |
157 | .ndo_init = loopback_dev_init, |
158 | .ndo_start_xmit = loopback_xmit, |
159 | .ndo_get_stats64 = loopback_get_stats64, |
160 | .ndo_set_mac_address = eth_mac_addr, |
161 | }; |
162 | |
163 | static void gen_lo_setup(struct net_device *dev, |
164 | unsigned int mtu, |
165 | const struct ethtool_ops *eth_ops, |
166 | const struct header_ops *hdr_ops, |
167 | const struct net_device_ops *dev_ops, |
168 | void (*dev_destructor)(struct net_device *dev)) |
169 | { |
170 | dev->mtu = mtu; |
171 | dev->hard_header_len = ETH_HLEN; /* 14 */ |
172 | dev->min_header_len = ETH_HLEN; /* 14 */ |
173 | dev->addr_len = ETH_ALEN; /* 6 */ |
174 | dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ |
175 | dev->flags = IFF_LOOPBACK; |
176 | dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; |
177 | netif_keep_dst(dev); |
178 | dev->hw_features = NETIF_F_GSO_SOFTWARE; |
179 | dev->features = NETIF_F_SG | NETIF_F_FRAGLIST |
180 | | NETIF_F_GSO_SOFTWARE |
181 | | NETIF_F_HW_CSUM |
182 | | NETIF_F_RXCSUM |
183 | | NETIF_F_SCTP_CRC |
184 | | NETIF_F_HIGHDMA |
185 | | NETIF_F_LLTX |
186 | | NETIF_F_NETNS_LOCAL |
187 | | NETIF_F_VLAN_CHALLENGED |
188 | | NETIF_F_LOOPBACK; |
189 | dev->ethtool_ops = eth_ops; |
190 | dev->header_ops = hdr_ops; |
191 | dev->netdev_ops = dev_ops; |
192 | dev->needs_free_netdev = true; |
193 | dev->priv_destructor = dev_destructor; |
194 | |
195 | netif_set_tso_max_size(dev, GSO_MAX_SIZE); |
196 | } |
197 | |
198 | /* The loopback device is special. There is only one instance |
199 | * per network namespace. |
200 | */ |
201 | static void loopback_setup(struct net_device *dev) |
202 | { |
203 | gen_lo_setup(dev, mtu: (64 * 1024), eth_ops: &loopback_ethtool_ops, hdr_ops: ð_header_ops, |
204 | dev_ops: &loopback_ops, dev_destructor: loopback_dev_free); |
205 | } |
206 | |
207 | /* Setup and register the loopback device. */ |
208 | static __net_init int loopback_net_init(struct net *net) |
209 | { |
210 | struct net_device *dev; |
211 | int err; |
212 | |
213 | err = -ENOMEM; |
214 | dev = alloc_netdev(0, "lo" , NET_NAME_PREDICTABLE, loopback_setup); |
215 | if (!dev) |
216 | goto out; |
217 | |
218 | dev_net_set(dev, net); |
219 | err = register_netdev(dev); |
220 | if (err) |
221 | goto out_free_netdev; |
222 | |
223 | BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); |
224 | net->loopback_dev = dev; |
225 | return 0; |
226 | |
227 | out_free_netdev: |
228 | free_netdev(dev); |
229 | out: |
230 | if (net_eq(net1: net, net2: &init_net)) |
231 | panic(fmt: "loopback: Failed to register netdevice: %d\n" , err); |
232 | return err; |
233 | } |
234 | |
235 | /* Registered in net/core/dev.c */ |
236 | struct pernet_operations __net_initdata loopback_net_ops = { |
237 | .init = loopback_net_init, |
238 | }; |
239 | |
240 | /* blackhole netdevice */ |
241 | static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb, |
242 | struct net_device *dev) |
243 | { |
244 | kfree_skb(skb); |
245 | net_warn_ratelimited("%s(): Dropping skb.\n" , __func__); |
246 | return NETDEV_TX_OK; |
247 | } |
248 | |
249 | static const struct net_device_ops blackhole_netdev_ops = { |
250 | .ndo_start_xmit = blackhole_netdev_xmit, |
251 | }; |
252 | |
253 | /* This is a dst-dummy device used specifically for invalidated |
254 | * DSTs and unlike loopback, this is not per-ns. |
255 | */ |
256 | static void blackhole_netdev_setup(struct net_device *dev) |
257 | { |
258 | gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, dev_ops: &blackhole_netdev_ops, NULL); |
259 | } |
260 | |
261 | /* Setup and register the blackhole_netdev. */ |
262 | static int __init blackhole_netdev_init(void) |
263 | { |
264 | blackhole_netdev = alloc_netdev(0, "blackhole_dev" , NET_NAME_UNKNOWN, |
265 | blackhole_netdev_setup); |
266 | if (!blackhole_netdev) |
267 | return -ENOMEM; |
268 | |
269 | rtnl_lock(); |
270 | dev_init_scheduler(dev: blackhole_netdev); |
271 | dev_activate(dev: blackhole_netdev); |
272 | rtnl_unlock(); |
273 | |
274 | blackhole_netdev->flags |= IFF_UP | IFF_RUNNING; |
275 | dev_net_set(dev: blackhole_netdev, net: &init_net); |
276 | |
277 | return 0; |
278 | } |
279 | |
280 | device_initcall(blackhole_netdev_init); |
281 | |