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1 | /* dummy.c: a dummy net driver | |
2 | ||
3 | The purpose of this driver is to provide a device to point a | |
4 | route through, but not to actually transmit packets. | |
5 | ||
6 | Why? If you have a machine whose only connection is an occasional | |
7 | PPP/SLIP/PLIP link, you can only connect to your own hostname | |
8 | when the link is up. Otherwise you have to use localhost. | |
9 | This isn't very consistent. | |
10 | ||
11 | One solution is to set up a dummy link using PPP/SLIP/PLIP, | |
12 | but this seems (to me) too much overhead for too little gain. | |
13 | This driver provides a small alternative. Thus you can do | |
14 | ||
15 | [when not running slip] | |
16 | ifconfig dummy slip.addr.ess.here up | |
17 | [to go to slip] | |
18 | ifconfig dummy down | |
19 | dip whatever | |
20 | ||
21 | This was written by looking at Donald Becker's skeleton driver | |
22 | and the loopback driver. I then threw away anything that didn't | |
23 | apply! Thanks to Alan Cox for the key clue on what to do with | |
24 | misguided packets. | |
25 | ||
26 | Nick Holloway, 27th May 1994 | |
27 | [I tweaked this explanation a little but that's all] | |
28 | Alan Cox, 30th May 1994 | |
29 | */ | |
30 | ||
31 | #include <linux/module.h> | |
32 | #include <linux/kernel.h> | |
33 | #include <linux/netdevice.h> | |
34 | #include <linux/etherdevice.h> | |
35 | #include <linux/init.h> | |
36 | #include <linux/moduleparam.h> | |
37 | #include <linux/rtnetlink.h> | |
38 | #include <linux/net_tstamp.h> | |
39 | #include <net/rtnetlink.h> | |
40 | #include <linux/u64_stats_sync.h> | |
41 | ||
42 | #define DRV_NAME "dummy" | |
43 | #define DRV_VERSION "1.0" | |
44 | ||
45 | static int numdummies = 1; | |
46 | ||
47 | /* fake multicast ability */ | |
48 | static void set_multicast_list(struct net_device *dev) | |
49 | { | |
50 | } | |
51 | ||
52 | struct pcpu_dstats { | |
53 | u64 tx_packets; | |
54 | u64 tx_bytes; | |
55 | struct u64_stats_sync syncp; | |
56 | }; | |
57 | ||
58 | static void dummy_get_stats64(struct net_device *dev, | |
59 | struct rtnl_link_stats64 *stats) | |
60 | { | |
61 | int i; | |
62 | ||
63 | for_each_possible_cpu(i) { | |
64 | const struct pcpu_dstats *dstats; | |
65 | u64 tbytes, tpackets; | |
66 | unsigned int start; | |
67 | ||
68 | dstats = per_cpu_ptr(dev->dstats, i); | |
69 | do { | |
70 | start = u64_stats_fetch_begin_irq(&dstats->syncp); | |
71 | tbytes = dstats->tx_bytes; | |
72 | tpackets = dstats->tx_packets; | |
73 | } while (u64_stats_fetch_retry_irq(&dstats->syncp, start)); | |
74 | stats->tx_bytes += tbytes; | |
75 | stats->tx_packets += tpackets; | |
76 | } | |
77 | } | |
78 | ||
79 | static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev) | |
80 | { | |
81 | struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats); | |
82 | ||
83 | u64_stats_update_begin(&dstats->syncp); | |
84 | dstats->tx_packets++; | |
85 | dstats->tx_bytes += skb->len; | |
86 | u64_stats_update_end(&dstats->syncp); | |
87 | ||
88 | skb_tx_timestamp(skb); | |
89 | dev_kfree_skb(skb); | |
90 | return NETDEV_TX_OK; | |
91 | } | |
92 | ||
93 | static int dummy_dev_init(struct net_device *dev) | |
94 | { | |
95 | dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats); | |
96 | if (!dev->dstats) | |
97 | return -ENOMEM; | |
98 | ||
99 | return 0; | |
100 | } | |
101 | ||
102 | static void dummy_dev_uninit(struct net_device *dev) | |
103 | { | |
104 | free_percpu(dev->dstats); | |
105 | } | |
106 | ||
107 | static int dummy_change_carrier(struct net_device *dev, bool new_carrier) | |
108 | { | |
109 | if (new_carrier) | |
110 | netif_carrier_on(dev); | |
111 | else | |
112 | netif_carrier_off(dev); | |
113 | return 0; | |
114 | } | |
115 | ||
116 | static const struct net_device_ops dummy_netdev_ops = { | |
117 | .ndo_init = dummy_dev_init, | |
118 | .ndo_uninit = dummy_dev_uninit, | |
119 | .ndo_start_xmit = dummy_xmit, | |
120 | .ndo_validate_addr = eth_validate_addr, | |
121 | .ndo_set_rx_mode = set_multicast_list, | |
122 | .ndo_set_mac_address = eth_mac_addr, | |
123 | .ndo_get_stats64 = dummy_get_stats64, | |
124 | .ndo_change_carrier = dummy_change_carrier, | |
125 | }; | |
126 | ||
127 | static void dummy_get_drvinfo(struct net_device *dev, | |
128 | struct ethtool_drvinfo *info) | |
129 | { | |
130 | strlcpy(info->driver, DRV_NAME, sizeof(info->driver)); | |
131 | strlcpy(info->version, DRV_VERSION, sizeof(info->version)); | |
132 | } | |
133 | ||
134 | static int dummy_get_ts_info(struct net_device *dev, | |
135 | struct ethtool_ts_info *ts_info) | |
136 | { | |
137 | ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE | | |
138 | SOF_TIMESTAMPING_RX_SOFTWARE | | |
139 | SOF_TIMESTAMPING_SOFTWARE; | |
140 | ||
141 | ts_info->phc_index = -1; | |
142 | ||
143 | return 0; | |
144 | }; | |
145 | ||
146 | static const struct ethtool_ops dummy_ethtool_ops = { | |
147 | .get_drvinfo = dummy_get_drvinfo, | |
148 | .get_ts_info = dummy_get_ts_info, | |
149 | }; | |
150 | ||
151 | static void dummy_setup(struct net_device *dev) | |
152 | { | |
153 | ether_setup(dev); | |
154 | ||
155 | /* Initialize the device structure. */ | |
156 | dev->netdev_ops = &dummy_netdev_ops; | |
157 | dev->ethtool_ops = &dummy_ethtool_ops; | |
158 | dev->needs_free_netdev = true; | |
159 | ||
160 | /* Fill in device structure with ethernet-generic values. */ | |
161 | dev->flags |= IFF_NOARP; | |
162 | dev->flags &= ~IFF_MULTICAST; | |
163 | dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; | |
164 | dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST; | |
165 | dev->features |= NETIF_F_ALL_TSO; | |
166 | dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX; | |
167 | dev->features |= NETIF_F_GSO_ENCAP_ALL; | |
168 | dev->hw_features |= dev->features; | |
169 | dev->hw_enc_features |= dev->features; | |
170 | eth_hw_addr_random(dev); | |
171 | ||
172 | dev->min_mtu = 0; | |
173 | dev->max_mtu = 0; | |
174 | } | |
175 | ||
176 | static int dummy_validate(struct nlattr *tb[], struct nlattr *data[], | |
177 | struct netlink_ext_ack *extack) | |
178 | { | |
179 | if (tb[IFLA_ADDRESS]) { | |
180 | if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN) | |
181 | return -EINVAL; | |
182 | if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS]))) | |
183 | return -EADDRNOTAVAIL; | |
184 | } | |
185 | return 0; | |
186 | } | |
187 | ||
188 | static struct rtnl_link_ops dummy_link_ops __read_mostly = { | |
189 | .kind = DRV_NAME, | |
190 | .setup = dummy_setup, | |
191 | .validate = dummy_validate, | |
192 | }; | |
193 | ||
194 | /* Number of dummy devices to be set up by this module. */ | |
195 | module_param(numdummies, int, 0); | |
196 | MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices"); | |
197 | ||
198 | static int __init dummy_init_one(void) | |
199 | { | |
200 | struct net_device *dev_dummy; | |
201 | int err; | |
202 | ||
203 | dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup); | |
204 | if (!dev_dummy) | |
205 | return -ENOMEM; | |
206 | ||
207 | dev_dummy->rtnl_link_ops = &dummy_link_ops; | |
208 | err = register_netdevice(dev_dummy); | |
209 | if (err < 0) | |
210 | goto err; | |
211 | return 0; | |
212 | ||
213 | err: | |
214 | free_netdev(dev_dummy); | |
215 | return err; | |
216 | } | |
217 | ||
218 | static int __init dummy_init_module(void) | |
219 | { | |
220 | int i, err = 0; | |
221 | ||
222 | rtnl_lock(); | |
223 | err = __rtnl_link_register(&dummy_link_ops); | |
224 | if (err < 0) | |
225 | goto out; | |
226 | ||
227 | for (i = 0; i < numdummies && !err; i++) { | |
228 | err = dummy_init_one(); | |
229 | cond_resched(); | |
230 | } | |
231 | if (err < 0) | |
232 | __rtnl_link_unregister(&dummy_link_ops); | |
233 | ||
234 | out: | |
235 | rtnl_unlock(); | |
236 | ||
237 | return err; | |
238 | } | |
239 | ||
240 | static void __exit dummy_cleanup_module(void) | |
241 | { | |
242 | rtnl_link_unregister(&dummy_link_ops); | |
243 | } | |
244 | ||
245 | module_init(dummy_init_module); | |
246 | module_exit(dummy_cleanup_module); | |
247 | MODULE_LICENSE("GPL"); | |
248 | MODULE_ALIAS_RTNL_LINK(DRV_NAME); | |
249 | MODULE_VERSION(DRV_VERSION); |