linux/drivers/net/dummy.c
Vincent Mailhol f20a0a0519 ethtool: doc: clarify what drivers can implement in their get_drvinfo()
Many of the drivers which implement ethtool_ops::get_drvinfo() will
prints the .driver, .version or .bus_info of struct ethtool_drvinfo.
To have a glance of current state, do:

  $ git grep -W "get_drvinfo(struct"

Printing in those three fields is useless because:

  - since [1], the driver version should be the kernel version (at
    least for upstream drivers). Arguably, out of tree drivers might
    still want to set a custom version, but out of tree is not our
    focus.

  - since [2], the core is able to provide default values for .driver
    and .bus_info.

In summary, drivers may provide .fw_version and .erom_version, the
rest is expected to be done by the core.

In struct ethtool_ops doc from linux/ethtool: rephrase field
get_drvinfo() doc to discourage developers from implementing this
callback.

In struct ethtool_drvinfo doc from uapi/linux/ethtool.h: remove the
paragraph mentioning what drivers should do. Rationale: no need to
repeat what is already written in struct ethtool_ops doc. But add a
note that .fw_version and .erom_version are driver defined.

Also update the dummy driver and simply remove the callback in order
not to confuse the newcomers: most of the drivers will not need this
callback function any more.

[1] commit 6a7e25c7fb ("net/core: Replace driver version to be
    kernel version")
Link: https://git.kernel.org/torvalds/linux/c/6a7e25c7fb48

[2] commit edaf5df22c ("ethtool: ethtool_get_drvinfo: populate
    drvinfo fields even if callback exits")
Link: https://git.kernel.org/netdev/net-next/c/edaf5df22cb8

Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/r/20221116171828.4093-1-mailhol.vincent@wanadoo.fr
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2022-11-17 19:26:02 -08:00

206 lines
4.9 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/* dummy.c: a dummy net driver
The purpose of this driver is to provide a device to point a
route through, but not to actually transmit packets.
Why? If you have a machine whose only connection is an occasional
PPP/SLIP/PLIP link, you can only connect to your own hostname
when the link is up. Otherwise you have to use localhost.
This isn't very consistent.
One solution is to set up a dummy link using PPP/SLIP/PLIP,
but this seems (to me) too much overhead for too little gain.
This driver provides a small alternative. Thus you can do
[when not running slip]
ifconfig dummy slip.addr.ess.here up
[to go to slip]
ifconfig dummy down
dip whatever
This was written by looking at Donald Becker's skeleton driver
and the loopback driver. I then threw away anything that didn't
apply! Thanks to Alan Cox for the key clue on what to do with
misguided packets.
Nick Holloway, 27th May 1994
[I tweaked this explanation a little but that's all]
Alan Cox, 30th May 1994
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/rtnetlink.h>
#include <linux/net_tstamp.h>
#include <net/rtnetlink.h>
#include <linux/u64_stats_sync.h>
#define DRV_NAME "dummy"
static int numdummies = 1;
/* fake multicast ability */
static void set_multicast_list(struct net_device *dev)
{
}
static void dummy_get_stats64(struct net_device *dev,
struct rtnl_link_stats64 *stats)
{
dev_lstats_read(dev, &stats->tx_packets, &stats->tx_bytes);
}
static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
{
dev_lstats_add(dev, skb->len);
skb_tx_timestamp(skb);
dev_kfree_skb(skb);
return NETDEV_TX_OK;
}
static int dummy_dev_init(struct net_device *dev)
{
dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
if (!dev->lstats)
return -ENOMEM;
return 0;
}
static void dummy_dev_uninit(struct net_device *dev)
{
free_percpu(dev->lstats);
}
static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
{
if (new_carrier)
netif_carrier_on(dev);
else
netif_carrier_off(dev);
return 0;
}
static const struct net_device_ops dummy_netdev_ops = {
.ndo_init = dummy_dev_init,
.ndo_uninit = dummy_dev_uninit,
.ndo_start_xmit = dummy_xmit,
.ndo_validate_addr = eth_validate_addr,
.ndo_set_rx_mode = set_multicast_list,
.ndo_set_mac_address = eth_mac_addr,
.ndo_get_stats64 = dummy_get_stats64,
.ndo_change_carrier = dummy_change_carrier,
};
static const struct ethtool_ops dummy_ethtool_ops = {
.get_ts_info = ethtool_op_get_ts_info,
};
static void dummy_setup(struct net_device *dev)
{
ether_setup(dev);
/* Initialize the device structure. */
dev->netdev_ops = &dummy_netdev_ops;
dev->ethtool_ops = &dummy_ethtool_ops;
dev->needs_free_netdev = true;
/* Fill in device structure with ethernet-generic values. */
dev->flags |= IFF_NOARP;
dev->flags &= ~IFF_MULTICAST;
dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST;
dev->features |= NETIF_F_GSO_SOFTWARE;
dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
dev->features |= NETIF_F_GSO_ENCAP_ALL;
dev->hw_features |= dev->features;
dev->hw_enc_features |= dev->features;
eth_hw_addr_random(dev);
dev->min_mtu = 0;
dev->max_mtu = 0;
}
static int dummy_validate(struct nlattr *tb[], struct nlattr *data[],
struct netlink_ext_ack *extack)
{
if (tb[IFLA_ADDRESS]) {
if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
return -EINVAL;
if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
return -EADDRNOTAVAIL;
}
return 0;
}
static struct rtnl_link_ops dummy_link_ops __read_mostly = {
.kind = DRV_NAME,
.setup = dummy_setup,
.validate = dummy_validate,
};
/* Number of dummy devices to be set up by this module. */
module_param(numdummies, int, 0);
MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
static int __init dummy_init_one(void)
{
struct net_device *dev_dummy;
int err;
dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup);
if (!dev_dummy)
return -ENOMEM;
dev_dummy->rtnl_link_ops = &dummy_link_ops;
err = register_netdevice(dev_dummy);
if (err < 0)
goto err;
return 0;
err:
free_netdev(dev_dummy);
return err;
}
static int __init dummy_init_module(void)
{
int i, err = 0;
down_write(&pernet_ops_rwsem);
rtnl_lock();
err = __rtnl_link_register(&dummy_link_ops);
if (err < 0)
goto out;
for (i = 0; i < numdummies && !err; i++) {
err = dummy_init_one();
cond_resched();
}
if (err < 0)
__rtnl_link_unregister(&dummy_link_ops);
out:
rtnl_unlock();
up_write(&pernet_ops_rwsem);
return err;
}
static void __exit dummy_cleanup_module(void)
{
rtnl_link_unregister(&dummy_link_ops);
}
module_init(dummy_init_module);
module_exit(dummy_cleanup_module);
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK(DRV_NAME);