1 /* dummy.c: a dummy net driver
3 The purpose of this driver is to provide a device to point a
4 route through, but not to actually transmit packets.
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.
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
15 [when not running slip]
16 ifconfig dummy slip.addr.ess.here up
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
26 Nick Holloway, 27th May 1994
27 [I tweaked this explanation a little but that's all]
28 Alan Cox, 30th May 1994
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>
41 static int numdummies
= 1;
43 static int dummy_set_address(struct net_device
*dev
, void *p
)
45 struct sockaddr
*sa
= p
;
47 if (!is_valid_ether_addr(sa
->sa_data
))
48 return -EADDRNOTAVAIL
;
50 memcpy(dev
->dev_addr
, sa
->sa_data
, ETH_ALEN
);
54 /* fake multicast ability */
55 static void set_multicast_list(struct net_device
*dev
)
62 struct u64_stats_sync syncp
;
65 static struct rtnl_link_stats64
*dummy_get_stats64(struct net_device
*dev
,
66 struct rtnl_link_stats64
*stats
)
70 for_each_possible_cpu(i
) {
71 const struct pcpu_dstats
*dstats
;
75 dstats
= per_cpu_ptr(dev
->dstats
, i
);
77 start
= u64_stats_fetch_begin(&dstats
->syncp
);
78 tbytes
= dstats
->tx_bytes
;
79 tpackets
= dstats
->tx_packets
;
80 } while (u64_stats_fetch_retry(&dstats
->syncp
, start
));
81 stats
->tx_bytes
+= tbytes
;
82 stats
->tx_packets
+= tpackets
;
87 static netdev_tx_t
dummy_xmit(struct sk_buff
*skb
, struct net_device
*dev
)
89 struct pcpu_dstats
*dstats
= this_cpu_ptr(dev
->dstats
);
91 u64_stats_update_begin(&dstats
->syncp
);
93 dstats
->tx_bytes
+= skb
->len
;
94 u64_stats_update_end(&dstats
->syncp
);
100 static int dummy_dev_init(struct net_device
*dev
)
102 dev
->dstats
= alloc_percpu(struct pcpu_dstats
);
109 static void dummy_dev_uninit(struct net_device
*dev
)
111 free_percpu(dev
->dstats
);
114 static const struct net_device_ops dummy_netdev_ops
= {
115 .ndo_init
= dummy_dev_init
,
116 .ndo_uninit
= dummy_dev_uninit
,
117 .ndo_start_xmit
= dummy_xmit
,
118 .ndo_validate_addr
= eth_validate_addr
,
119 .ndo_set_rx_mode
= set_multicast_list
,
120 .ndo_set_mac_address
= dummy_set_address
,
121 .ndo_get_stats64
= dummy_get_stats64
,
124 static void dummy_setup(struct net_device
*dev
)
128 /* Initialize the device structure. */
129 dev
->netdev_ops
= &dummy_netdev_ops
;
130 dev
->destructor
= free_netdev
;
132 /* Fill in device structure with ethernet-generic values. */
133 dev
->tx_queue_len
= 0;
134 dev
->flags
|= IFF_NOARP
;
135 dev
->flags
&= ~IFF_MULTICAST
;
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 random_ether_addr(dev
->dev_addr
);
141 static int dummy_validate(struct nlattr
*tb
[], struct nlattr
*data
[])
143 if (tb
[IFLA_ADDRESS
]) {
144 if (nla_len(tb
[IFLA_ADDRESS
]) != ETH_ALEN
)
146 if (!is_valid_ether_addr(nla_data(tb
[IFLA_ADDRESS
])))
147 return -EADDRNOTAVAIL
;
152 static struct rtnl_link_ops dummy_link_ops __read_mostly
= {
154 .setup
= dummy_setup
,
155 .validate
= dummy_validate
,
158 /* Number of dummy devices to be set up by this module. */
159 module_param(numdummies
, int, 0);
160 MODULE_PARM_DESC(numdummies
, "Number of dummy pseudo devices");
162 static int __init
dummy_init_one(void)
164 struct net_device
*dev_dummy
;
167 dev_dummy
= alloc_netdev(0, "dummy%d", dummy_setup
);
171 dev_dummy
->rtnl_link_ops
= &dummy_link_ops
;
172 err
= register_netdevice(dev_dummy
);
178 free_netdev(dev_dummy
);
182 static int __init
dummy_init_module(void)
187 err
= __rtnl_link_register(&dummy_link_ops
);
189 for (i
= 0; i
< numdummies
&& !err
; i
++)
190 err
= dummy_init_one();
192 __rtnl_link_unregister(&dummy_link_ops
);
198 static void __exit
dummy_cleanup_module(void)
200 rtnl_link_unregister(&dummy_link_ops
);
203 module_init(dummy_init_module
);
204 module_exit(dummy_cleanup_module
);
205 MODULE_LICENSE("GPL");
206 MODULE_ALIAS_RTNL_LINK("dummy");