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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);
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
43static int dummy_set_address(struct net_device *dev, void *p)
44{
45 struct sockaddr *sa = p;
46
47 if (!is_valid_ether_addr(sa->sa_data))
48 return -EADDRNOTAVAIL;
49
50 dev->addr_assign_type &= ~NET_ADDR_RANDOM;
51 memcpy(dev->dev_addr, sa->sa_data, ETH_ALEN);
52 return 0;
53}
54
55/* fake multicast ability */
56static void set_multicast_list(struct net_device *dev)
57{
58}
59
60struct pcpu_dstats {
61 u64 tx_packets;
62 u64 tx_bytes;
63 struct u64_stats_sync syncp;
64};
65
66static struct rtnl_link_stats64 *dummy_get_stats64(struct net_device *dev,
67 struct rtnl_link_stats64 *stats)
68{
69 int i;
70
71 for_each_possible_cpu(i) {
72 const struct pcpu_dstats *dstats;
73 u64 tbytes, tpackets;
74 unsigned int start;
75
76 dstats = per_cpu_ptr(dev->dstats, i);
77 do {
78 start = u64_stats_fetch_begin(&dstats->syncp);
79 tbytes = dstats->tx_bytes;
80 tpackets = dstats->tx_packets;
81 } while (u64_stats_fetch_retry(&dstats->syncp, start));
82 stats->tx_bytes += tbytes;
83 stats->tx_packets += tpackets;
84 }
85 return stats;
86}
87
88static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
89{
90 struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
91
92 u64_stats_update_begin(&dstats->syncp);
93 dstats->tx_packets++;
94 dstats->tx_bytes += skb->len;
95 u64_stats_update_end(&dstats->syncp);
96
97 dev_kfree_skb(skb);
98 return NETDEV_TX_OK;
99}
100
101static int dummy_dev_init(struct net_device *dev)
102{
103 dev->dstats = alloc_percpu(struct pcpu_dstats);
104 if (!dev->dstats)
105 return -ENOMEM;
106
107 return 0;
108}
109
110static void dummy_dev_uninit(struct net_device *dev)
111{
112 free_percpu(dev->dstats);
113}
114
115static const struct net_device_ops dummy_netdev_ops = {
116 .ndo_init = dummy_dev_init,
117 .ndo_uninit = dummy_dev_uninit,
118 .ndo_start_xmit = dummy_xmit,
119 .ndo_validate_addr = eth_validate_addr,
120 .ndo_set_rx_mode = set_multicast_list,
121 .ndo_set_mac_address = dummy_set_address,
122 .ndo_get_stats64 = dummy_get_stats64,
123};
124
125static void dummy_setup(struct net_device *dev)
126{
127 ether_setup(dev);
128
129 /* Initialize the device structure. */
130 dev->netdev_ops = &dummy_netdev_ops;
131 dev->destructor = free_netdev;
132
133 /* Fill in device structure with ethernet-generic values. */
134 dev->tx_queue_len = 0;
135 dev->flags |= IFF_NOARP;
136 dev->flags &= ~IFF_MULTICAST;
137 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO;
138 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
139 eth_hw_addr_random(dev);
140}
141
142static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
143{
144 if (tb[IFLA_ADDRESS]) {
145 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
146 return -EINVAL;
147 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
148 return -EADDRNOTAVAIL;
149 }
150 return 0;
151}
152
153static struct rtnl_link_ops dummy_link_ops __read_mostly = {
154 .kind = "dummy",
155 .setup = dummy_setup,
156 .validate = dummy_validate,
157};
158
159/* Number of dummy devices to be set up by this module. */
160module_param(numdummies, int, 0);
161MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
162
163static int __init dummy_init_one(void)
164{
165 struct net_device *dev_dummy;
166 int err;
167
168 dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
169 if (!dev_dummy)
170 return -ENOMEM;
171
172 dev_dummy->rtnl_link_ops = &dummy_link_ops;
173 err = register_netdevice(dev_dummy);
174 if (err < 0)
175 goto err;
176 return 0;
177
178err:
179 free_netdev(dev_dummy);
180 return err;
181}
182
183static int __init dummy_init_module(void)
184{
185 int i, err = 0;
186
187 rtnl_lock();
188 err = __rtnl_link_register(&dummy_link_ops);
189
190 for (i = 0; i < numdummies && !err; i++) {
191 err = dummy_init_one();
192 cond_resched();
193 }
194 if (err < 0)
195 __rtnl_link_unregister(&dummy_link_ops);
196 rtnl_unlock();
197
198 return err;
199}
200
201static void __exit dummy_cleanup_module(void)
202{
203 rtnl_link_unregister(&dummy_link_ops);
204}
205
206module_init(dummy_init_module);
207module_exit(dummy_cleanup_module);
208MODULE_LICENSE("GPL");
209MODULE_ALIAS_RTNL_LINK("dummy");