1 // SPDX-License-Identifier: GPL-2.0-only
2 /* dummy.c: a dummy net driver
4 The purpose of this driver is to provide a device to point a
5 route through, but not to actually transmit packets.
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.
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
16 [when not running slip]
17 ifconfig dummy slip.addr.ess.here up
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
27 Nick Holloway, 27th May 1994
28 [I tweaked this explanation a little but that's all]
29 Alan Cox, 30th May 1994
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>
44 #define DRV_NAME "dummy"
46 static int numdummies
= 1;
48 /* fake multicast ability */
49 static void set_multicast_list(struct net_device
*dev
)
53 static void dummy_get_stats64(struct net_device
*dev
,
54 struct rtnl_link_stats64
*stats
)
56 dev_lstats_read(dev
, &stats
->tx_packets
, &stats
->tx_bytes
);
59 static netdev_tx_t
dummy_xmit(struct sk_buff
*skb
, struct net_device
*dev
)
61 dev_lstats_add(dev
, skb
->len
);
63 skb_tx_timestamp(skb
);
68 static int dummy_dev_init(struct net_device
*dev
)
70 dev
->lstats
= netdev_alloc_pcpu_stats(struct pcpu_lstats
);
77 static void dummy_dev_uninit(struct net_device
*dev
)
79 free_percpu(dev
->lstats
);
82 static int dummy_change_carrier(struct net_device
*dev
, bool new_carrier
)
85 netif_carrier_on(dev
);
87 netif_carrier_off(dev
);
91 static const struct net_device_ops dummy_netdev_ops
= {
92 .ndo_init
= dummy_dev_init
,
93 .ndo_uninit
= dummy_dev_uninit
,
94 .ndo_start_xmit
= dummy_xmit
,
95 .ndo_validate_addr
= eth_validate_addr
,
96 .ndo_set_rx_mode
= set_multicast_list
,
97 .ndo_set_mac_address
= eth_mac_addr
,
98 .ndo_get_stats64
= dummy_get_stats64
,
99 .ndo_change_carrier
= dummy_change_carrier
,
102 static void dummy_get_drvinfo(struct net_device
*dev
,
103 struct ethtool_drvinfo
*info
)
105 strlcpy(info
->driver
, DRV_NAME
, sizeof(info
->driver
));
108 static const struct ethtool_ops dummy_ethtool_ops
= {
109 .get_drvinfo
= dummy_get_drvinfo
,
110 .get_ts_info
= ethtool_op_get_ts_info
,
113 static void dummy_setup(struct net_device
*dev
)
117 /* Initialize the device structure. */
118 dev
->netdev_ops
= &dummy_netdev_ops
;
119 dev
->ethtool_ops
= &dummy_ethtool_ops
;
120 dev
->needs_free_netdev
= true;
122 /* Fill in device structure with ethernet-generic values. */
123 dev
->flags
|= IFF_NOARP
;
124 dev
->flags
&= ~IFF_MULTICAST
;
125 dev
->priv_flags
|= IFF_LIVE_ADDR_CHANGE
| IFF_NO_QUEUE
;
126 dev
->features
|= NETIF_F_SG
| NETIF_F_FRAGLIST
;
127 dev
->features
|= NETIF_F_ALL_TSO
;
128 dev
->features
|= NETIF_F_HW_CSUM
| NETIF_F_HIGHDMA
| NETIF_F_LLTX
;
129 dev
->features
|= NETIF_F_GSO_ENCAP_ALL
;
130 dev
->hw_features
|= dev
->features
;
131 dev
->hw_enc_features
|= dev
->features
;
132 eth_hw_addr_random(dev
);
138 static int dummy_validate(struct nlattr
*tb
[], struct nlattr
*data
[],
139 struct netlink_ext_ack
*extack
)
141 if (tb
[IFLA_ADDRESS
]) {
142 if (nla_len(tb
[IFLA_ADDRESS
]) != ETH_ALEN
)
144 if (!is_valid_ether_addr(nla_data(tb
[IFLA_ADDRESS
])))
145 return -EADDRNOTAVAIL
;
150 static struct rtnl_link_ops dummy_link_ops __read_mostly
= {
152 .setup
= dummy_setup
,
153 .validate
= dummy_validate
,
156 /* Number of dummy devices to be set up by this module. */
157 module_param(numdummies
, int, 0);
158 MODULE_PARM_DESC(numdummies
, "Number of dummy pseudo devices");
160 static int __init
dummy_init_one(void)
162 struct net_device
*dev_dummy
;
165 dev_dummy
= alloc_netdev(0, "dummy%d", NET_NAME_ENUM
, dummy_setup
);
169 dev_dummy
->rtnl_link_ops
= &dummy_link_ops
;
170 err
= register_netdevice(dev_dummy
);
176 free_netdev(dev_dummy
);
180 static int __init
dummy_init_module(void)
184 down_write(&pernet_ops_rwsem
);
186 err
= __rtnl_link_register(&dummy_link_ops
);
190 for (i
= 0; i
< numdummies
&& !err
; i
++) {
191 err
= dummy_init_one();
195 __rtnl_link_unregister(&dummy_link_ops
);
199 up_write(&pernet_ops_rwsem
);
204 static void __exit
dummy_cleanup_module(void)
206 rtnl_link_unregister(&dummy_link_ops
);
209 module_init(dummy_init_module
);
210 module_exit(dummy_cleanup_module
);
211 MODULE_LICENSE("GPL");
212 MODULE_ALIAS_RTNL_LINK(DRV_NAME
);