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We rename the dummy in modprobe.conf like this: install dummy0 /sbin/modprobe -o dummy0 --ignore-install dummy install dummy1 /sbin/modprobe -o dummy1 --ignore-install dummy We got oops when we run the command: modprobe dummy0 modprobe dummy1 ------------[ cut here ]------------ [ 3302.187584] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 [ 3302.195411] IP: [<ffffffff813fe62a>] __rtnl_link_unregister+0x9a/0xd0 [ 3302.201844] PGD 85c94a067 PUD 8517bd067 PMD 0 [ 3302.206305] Oops: 0002 [#1] SMP [ 3302.299737] task: ffff88105ccea300 ti: ffff880eba4a0000 task.ti: ffff880eba4a0000 [ 3302.307186] RIP: 0010:[<ffffffff813fe62a>] [<ffffffff813fe62a>] __rtnl_link_unregister+0x9a/0xd0 [ 3302.316044] RSP: 0018:ffff880eba4a1dd8 EFLAGS: 00010246 [ 3302.321332] RAX: 0000000000000000 RBX: ffffffff81a9d738 RCX: 0000000000000002 [ 3302.328436] RDX: 0000000000000000 RSI: ffffffffa04d602c RDI: ffff880eba4a1dd8 [ 3302.335541] RBP: ffff880eba4a1e18 R08: dead000000200200 R09: dead000000100100 [ 3302.342644] R10: 0000000000000080 R11: 0000000000000003 R12: ffffffff81a9d788 [ 3302.349748] R13: ffffffffa04d7020 R14: ffffffff81a9d670 R15: ffff880eba4a1dd8 [ 3302.364910] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3302.370630] CR2: 0000000000000008 CR3: 000000085e15e000 CR4: 00000000000427e0 [ 3302.377734] DR0: 0000000000000003 DR1: 00000000000000b0 DR2: 0000000000000001 [ 3302.384838] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 3302.391940] Stack: [ 3302.393944] ffff880eba4a1dd8 ffff880eba4a1dd8 ffff880eba4a1e18 ffffffffa04d70c0 [ 3302.401350] 00000000ffffffef ffffffffa01a8000 0000000000000000 ffffffff816111c8 [ 3302.408758] ffff880eba4a1e48 ffffffffa01a80be ffff880eba4a1e48 ffffffffa04d70c0 [ 3302.416164] Call Trace: [ 3302.418605] [<ffffffffa01a8000>] ? 0xffffffffa01a7fff [ 3302.423727] [<ffffffffa01a80be>] dummy_init_module+0xbe/0x1000 [dummy0] [ 3302.430405] [<ffffffffa01a8000>] ? 0xffffffffa01a7fff [ 3302.435535] [<ffffffff81000322>] do_one_initcall+0x152/0x1b0 [ 3302.441263] [<ffffffff810ab24b>] do_init_module+0x7b/0x200 [ 3302.446824] [<ffffffff810ad3d2>] load_module+0x4e2/0x530 [ 3302.452215] [<ffffffff8127ae40>] ? ddebug_dyndbg_boot_param_cb+0x60/0x60 [ 3302.458979] [<ffffffff810ad5f1>] SyS_init_module+0xd1/0x130 [ 3302.464627] [<ffffffff814b9652>] system_call_fastpath+0x16/0x1b [ 3302.490090] RIP [<ffffffff813fe62a>] __rtnl_link_unregister+0x9a/0xd0 [ 3302.496607] RSP <ffff880eba4a1dd8> [ 3302.500084] CR2: 0000000000000008 [ 3302.503466] ---[ end trace 8342d49cd49f78ed ]--- The reason is that when loading dummy, if __rtnl_link_register() return failed, the init_module should return and avoid take the wrong path. Signed-off-by: Tan Xiaojun <tanxiaojun@huawei.com> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com> Signed-off-by: David S. Miller <davem@davemloft.net>
212 lines
4.9 KiB
C
212 lines
4.9 KiB
C
/* dummy.c: a dummy net driver
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The purpose of this driver is to provide a device to point a
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route through, but not to actually transmit packets.
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Why? If you have a machine whose only connection is an occasional
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PPP/SLIP/PLIP link, you can only connect to your own hostname
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when the link is up. Otherwise you have to use localhost.
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This isn't very consistent.
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One solution is to set up a dummy link using PPP/SLIP/PLIP,
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but this seems (to me) too much overhead for too little gain.
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This driver provides a small alternative. Thus you can do
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[when not running slip]
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ifconfig dummy slip.addr.ess.here up
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[to go to slip]
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ifconfig dummy down
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dip whatever
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This was written by looking at Donald Becker's skeleton driver
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and the loopback driver. I then threw away anything that didn't
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apply! Thanks to Alan Cox for the key clue on what to do with
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misguided packets.
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Nick Holloway, 27th May 1994
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[I tweaked this explanation a little but that's all]
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Alan Cox, 30th May 1994
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/netdevice.h>
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#include <linux/etherdevice.h>
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#include <linux/init.h>
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#include <linux/moduleparam.h>
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#include <linux/rtnetlink.h>
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#include <net/rtnetlink.h>
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#include <linux/u64_stats_sync.h>
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static int numdummies = 1;
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/* fake multicast ability */
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static void set_multicast_list(struct net_device *dev)
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{
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}
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struct pcpu_dstats {
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u64 tx_packets;
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u64 tx_bytes;
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struct u64_stats_sync syncp;
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};
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static struct rtnl_link_stats64 *dummy_get_stats64(struct net_device *dev,
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struct rtnl_link_stats64 *stats)
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{
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int i;
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for_each_possible_cpu(i) {
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const struct pcpu_dstats *dstats;
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u64 tbytes, tpackets;
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unsigned int start;
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dstats = per_cpu_ptr(dev->dstats, i);
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do {
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start = u64_stats_fetch_begin_bh(&dstats->syncp);
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tbytes = dstats->tx_bytes;
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tpackets = dstats->tx_packets;
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} while (u64_stats_fetch_retry_bh(&dstats->syncp, start));
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stats->tx_bytes += tbytes;
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stats->tx_packets += tpackets;
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}
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return stats;
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}
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static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
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{
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struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
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u64_stats_update_begin(&dstats->syncp);
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dstats->tx_packets++;
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dstats->tx_bytes += skb->len;
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u64_stats_update_end(&dstats->syncp);
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dev_kfree_skb(skb);
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return NETDEV_TX_OK;
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}
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static int dummy_dev_init(struct net_device *dev)
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{
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dev->dstats = alloc_percpu(struct pcpu_dstats);
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if (!dev->dstats)
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return -ENOMEM;
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return 0;
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}
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static void dummy_dev_uninit(struct net_device *dev)
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{
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free_percpu(dev->dstats);
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}
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static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
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{
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if (new_carrier)
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netif_carrier_on(dev);
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else
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netif_carrier_off(dev);
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return 0;
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}
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static const struct net_device_ops dummy_netdev_ops = {
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.ndo_init = dummy_dev_init,
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.ndo_uninit = dummy_dev_uninit,
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.ndo_start_xmit = dummy_xmit,
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.ndo_validate_addr = eth_validate_addr,
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.ndo_set_rx_mode = set_multicast_list,
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.ndo_set_mac_address = eth_mac_addr,
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.ndo_get_stats64 = dummy_get_stats64,
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.ndo_change_carrier = dummy_change_carrier,
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};
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static void dummy_setup(struct net_device *dev)
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{
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ether_setup(dev);
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/* Initialize the device structure. */
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dev->netdev_ops = &dummy_netdev_ops;
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dev->destructor = free_netdev;
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/* Fill in device structure with ethernet-generic values. */
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dev->tx_queue_len = 0;
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dev->flags |= IFF_NOARP;
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dev->flags &= ~IFF_MULTICAST;
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dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
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dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO;
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dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
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eth_hw_addr_random(dev);
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}
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static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
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{
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if (tb[IFLA_ADDRESS]) {
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if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
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return -EINVAL;
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if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
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return -EADDRNOTAVAIL;
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}
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return 0;
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}
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static struct rtnl_link_ops dummy_link_ops __read_mostly = {
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.kind = "dummy",
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.setup = dummy_setup,
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.validate = dummy_validate,
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};
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/* Number of dummy devices to be set up by this module. */
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module_param(numdummies, int, 0);
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MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
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static int __init dummy_init_one(void)
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{
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struct net_device *dev_dummy;
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int err;
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dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
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if (!dev_dummy)
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return -ENOMEM;
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dev_dummy->rtnl_link_ops = &dummy_link_ops;
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err = register_netdevice(dev_dummy);
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if (err < 0)
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goto err;
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return 0;
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err:
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free_netdev(dev_dummy);
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return err;
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}
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static int __init dummy_init_module(void)
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{
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int i, err = 0;
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rtnl_lock();
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err = __rtnl_link_register(&dummy_link_ops);
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if (err < 0)
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goto out;
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for (i = 0; i < numdummies && !err; i++) {
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err = dummy_init_one();
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cond_resched();
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}
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if (err < 0)
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__rtnl_link_unregister(&dummy_link_ops);
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out:
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rtnl_unlock();
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return err;
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}
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static void __exit dummy_cleanup_module(void)
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{
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rtnl_link_unregister(&dummy_link_ops);
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}
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module_init(dummy_init_module);
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module_exit(dummy_cleanup_module);
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_RTNL_LINK("dummy");
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