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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 <net/rtnetlink.h>
39#include <linux/u64_stats_sync.h>
40
41static int numdummies = 1;
42
43/* fake multicast ability */
44static void set_multicast_list(struct net_device *dev)
45{
46}
47
48struct pcpu_dstats {
49 u64 tx_packets;
50 u64 tx_bytes;
51 struct u64_stats_sync syncp;
52};
53
54static struct rtnl_link_stats64 *dummy_get_stats64(struct net_device *dev,
55 struct rtnl_link_stats64 *stats)
56{
57 int i;
58
59 for_each_possible_cpu(i) {
60 const struct pcpu_dstats *dstats;
61 u64 tbytes, tpackets;
62 unsigned int start;
63
64 dstats = per_cpu_ptr(dev->dstats, i);
65 do {
66 start = u64_stats_fetch_begin_irq(&dstats->syncp);
67 tbytes = dstats->tx_bytes;
68 tpackets = dstats->tx_packets;
69 } while (u64_stats_fetch_retry_irq(&dstats->syncp, start));
70 stats->tx_bytes += tbytes;
71 stats->tx_packets += tpackets;
72 }
73 return stats;
74}
75
76static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
77{
78 struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
79
80 u64_stats_update_begin(&dstats->syncp);
81 dstats->tx_packets++;
82 dstats->tx_bytes += skb->len;
83 u64_stats_update_end(&dstats->syncp);
84
85 dev_kfree_skb(skb);
86 return NETDEV_TX_OK;
87}
88
89static int dummy_dev_init(struct net_device *dev)
90{
91 dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
92 if (!dev->dstats)
93 return -ENOMEM;
94
95 return 0;
96}
97
98static void dummy_dev_uninit(struct net_device *dev)
99{
100 free_percpu(dev->dstats);
101}
102
103static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
104{
105 if (new_carrier)
106 netif_carrier_on(dev);
107 else
108 netif_carrier_off(dev);
109 return 0;
110}
111
112static const struct net_device_ops dummy_netdev_ops = {
113 .ndo_init = dummy_dev_init,
114 .ndo_uninit = dummy_dev_uninit,
115 .ndo_start_xmit = dummy_xmit,
116 .ndo_validate_addr = eth_validate_addr,
117 .ndo_set_rx_mode = set_multicast_list,
118 .ndo_set_mac_address = eth_mac_addr,
119 .ndo_get_stats64 = dummy_get_stats64,
120 .ndo_change_carrier = dummy_change_carrier,
121};
122
123static void dummy_setup(struct net_device *dev)
124{
125 ether_setup(dev);
126
127 /* Initialize the device structure. */
128 dev->netdev_ops = &dummy_netdev_ops;
129 dev->destructor = free_netdev;
130
131 /* Fill in device structure with ethernet-generic values. */
132 dev->tx_queue_len = 0;
133 dev->flags |= IFF_NOARP;
134 dev->flags &= ~IFF_MULTICAST;
135 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
136 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO;
137 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
138 eth_hw_addr_random(dev);
139}
140
141static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
142{
143 if (tb[IFLA_ADDRESS]) {
144 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
145 return -EINVAL;
146 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
147 return -EADDRNOTAVAIL;
148 }
149 return 0;
150}
151
152static struct rtnl_link_ops dummy_link_ops __read_mostly = {
153 .kind = "dummy",
154 .setup = dummy_setup,
155 .validate = dummy_validate,
156};
157
158/* Number of dummy devices to be set up by this module. */
159module_param(numdummies, int, 0);
160MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
161
162static int __init dummy_init_one(void)
163{
164 struct net_device *dev_dummy;
165 int err;
166
167 dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
168 if (!dev_dummy)
169 return -ENOMEM;
170
171 dev_dummy->rtnl_link_ops = &dummy_link_ops;
172 err = register_netdevice(dev_dummy);
173 if (err < 0)
174 goto err;
175 return 0;
176
177err:
178 free_netdev(dev_dummy);
179 return err;
180}
181
182static int __init dummy_init_module(void)
183{
184 int i, err = 0;
185
186 rtnl_lock();
187 err = __rtnl_link_register(&dummy_link_ops);
188 if (err < 0)
189 goto out;
190
191 for (i = 0; i < numdummies && !err; i++) {
192 err = dummy_init_one();
193 cond_resched();
194 }
195 if (err < 0)
196 __rtnl_link_unregister(&dummy_link_ops);
197
198out:
199 rtnl_unlock();
200
201 return err;
202}
203
204static void __exit dummy_cleanup_module(void)
205{
206 rtnl_link_unregister(&dummy_link_ops);
207}
208
209module_init(dummy_init_module);
210module_exit(dummy_cleanup_module);
211MODULE_LICENSE("GPL");
212MODULE_ALIAS_RTNL_LINK("dummy");
1// SPDX-License-Identifier: GPL-2.0-only
2/* dummy.c: a dummy net driver
3
4 The purpose of this driver is to provide a device to point a
5 route through, but not to actually transmit packets.
6
7 Why? If you have a machine whose only connection is an occasional
8 PPP/SLIP/PLIP link, you can only connect to your own hostname
9 when the link is up. Otherwise you have to use localhost.
10 This isn't very consistent.
11
12 One solution is to set up a dummy link using PPP/SLIP/PLIP,
13 but this seems (to me) too much overhead for too little gain.
14 This driver provides a small alternative. Thus you can do
15
16 [when not running slip]
17 ifconfig dummy slip.addr.ess.here up
18 [to go to slip]
19 ifconfig dummy down
20 dip whatever
21
22 This was written by looking at Donald Becker's skeleton driver
23 and the loopback driver. I then threw away anything that didn't
24 apply! Thanks to Alan Cox for the key clue on what to do with
25 misguided packets.
26
27 Nick Holloway, 27th May 1994
28 [I tweaked this explanation a little but that's all]
29 Alan Cox, 30th May 1994
30*/
31
32#include <linux/module.h>
33#include <linux/kernel.h>
34#include <linux/netdevice.h>
35#include <linux/etherdevice.h>
36#include <linux/ethtool.h>
37#include <linux/init.h>
38#include <linux/moduleparam.h>
39#include <linux/rtnetlink.h>
40#include <linux/net_tstamp.h>
41#include <net/rtnetlink.h>
42#include <linux/u64_stats_sync.h>
43
44#define DRV_NAME "dummy"
45
46static int numdummies = 1;
47
48/* fake multicast ability */
49static void set_multicast_list(struct net_device *dev)
50{
51}
52
53static void dummy_get_stats64(struct net_device *dev,
54 struct rtnl_link_stats64 *stats)
55{
56 dev_lstats_read(dev, &stats->tx_packets, &stats->tx_bytes);
57}
58
59static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
60{
61 dev_lstats_add(dev, skb->len);
62
63 skb_tx_timestamp(skb);
64 dev_kfree_skb(skb);
65 return NETDEV_TX_OK;
66}
67
68static int dummy_dev_init(struct net_device *dev)
69{
70 dev->pcpu_stat_type = NETDEV_PCPU_STAT_LSTATS;
71
72 netdev_lockdep_set_classes(dev);
73 return 0;
74}
75
76static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
77{
78 if (new_carrier)
79 netif_carrier_on(dev);
80 else
81 netif_carrier_off(dev);
82 return 0;
83}
84
85static const struct net_device_ops dummy_netdev_ops = {
86 .ndo_init = dummy_dev_init,
87 .ndo_start_xmit = dummy_xmit,
88 .ndo_validate_addr = eth_validate_addr,
89 .ndo_set_rx_mode = set_multicast_list,
90 .ndo_set_mac_address = eth_mac_addr,
91 .ndo_get_stats64 = dummy_get_stats64,
92 .ndo_change_carrier = dummy_change_carrier,
93};
94
95static const struct ethtool_ops dummy_ethtool_ops = {
96 .get_ts_info = ethtool_op_get_ts_info,
97};
98
99static void dummy_setup(struct net_device *dev)
100{
101 ether_setup(dev);
102
103 /* Initialize the device structure. */
104 dev->netdev_ops = &dummy_netdev_ops;
105 dev->ethtool_ops = &dummy_ethtool_ops;
106 dev->needs_free_netdev = true;
107
108 /* Fill in device structure with ethernet-generic values. */
109 dev->flags |= IFF_NOARP;
110 dev->flags &= ~IFF_MULTICAST;
111 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
112 dev->lltx = true;
113 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST;
114 dev->features |= NETIF_F_GSO_SOFTWARE;
115 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA;
116 dev->features |= NETIF_F_GSO_ENCAP_ALL;
117 dev->hw_features |= dev->features;
118 dev->hw_enc_features |= dev->features;
119 eth_hw_addr_random(dev);
120
121 dev->min_mtu = 0;
122 dev->max_mtu = 0;
123}
124
125static int dummy_validate(struct nlattr *tb[], struct nlattr *data[],
126 struct netlink_ext_ack *extack)
127{
128 if (tb[IFLA_ADDRESS]) {
129 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
130 return -EINVAL;
131 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
132 return -EADDRNOTAVAIL;
133 }
134 return 0;
135}
136
137static struct rtnl_link_ops dummy_link_ops __read_mostly = {
138 .kind = DRV_NAME,
139 .setup = dummy_setup,
140 .validate = dummy_validate,
141};
142
143/* Number of dummy devices to be set up by this module. */
144module_param(numdummies, int, 0);
145MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
146
147static int __init dummy_init_one(void)
148{
149 struct net_device *dev_dummy;
150 int err;
151
152 dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup);
153 if (!dev_dummy)
154 return -ENOMEM;
155
156 dev_dummy->rtnl_link_ops = &dummy_link_ops;
157 err = register_netdevice(dev_dummy);
158 if (err < 0)
159 goto err;
160 return 0;
161
162err:
163 free_netdev(dev_dummy);
164 return err;
165}
166
167static int __init dummy_init_module(void)
168{
169 int i, err = 0;
170
171 err = rtnl_link_register(&dummy_link_ops);
172 if (err < 0)
173 return err;
174
175 rtnl_net_lock(&init_net);
176
177 for (i = 0; i < numdummies && !err; i++) {
178 err = dummy_init_one();
179 cond_resched();
180 }
181
182 rtnl_net_unlock(&init_net);
183
184 if (err < 0)
185 rtnl_link_unregister(&dummy_link_ops);
186
187 return err;
188}
189
190static void __exit dummy_cleanup_module(void)
191{
192 rtnl_link_unregister(&dummy_link_ops);
193}
194
195module_init(dummy_init_module);
196module_exit(dummy_cleanup_module);
197MODULE_LICENSE("GPL");
198MODULE_DESCRIPTION("Dummy netdevice driver which discards all packets sent to it");
199MODULE_ALIAS_RTNL_LINK(DRV_NAME);