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ipv6: give an IPv6 dev to blackhole_netdev

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IPv6 addrconf notifiers wants the loopback device to
be the last device being dismantled at netns deletion.

This caused many limitations and work arounds.

Back in linux-5.3, Mahesh added a per host blackhole_netdev
that can be used whenever we need to make sure objects no longer
refer to a disappearing device.

If we attach to blackhole_netdev an ip6_ptr (allocate an idev),
then we can use this special device (which is never freed)
in place of the loopback_dev (which can be freed).

This will permit improvements in netdev_run_todo() and other parts
of the stack where had steps to make sure loopback_dev was
the last device to disappear.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2022-02-10 13:42:29 -08:00 committed by David S. Miller
parent 2d4feb2c1b
commit e5f80fcf86
2 changed files with 40 additions and 59 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

78
net/ipv6/addrconf.c
View file

@ -372,7 +372,7 @@ static struct inet6_dev *ipv6_add_dev(struct net_device *dev)
ASSERT_RTNL(); ASSERT_RTNL();
if (dev->mtu < IPV6_MIN_MTU) if (dev->mtu < IPV6_MIN_MTU && dev != blackhole_netdev)
return ERR_PTR(-EINVAL); return ERR_PTR(-EINVAL);
ndev = kzalloc(sizeof(struct inet6_dev), GFP_KERNEL); ndev = kzalloc(sizeof(struct inet6_dev), GFP_KERNEL);
@ -400,21 +400,22 @@ static struct inet6_dev *ipv6_add_dev(struct net_device *dev)
/* We refer to the device */ /* We refer to the device */
dev_hold_track(dev, &ndev->dev_tracker, GFP_KERNEL); dev_hold_track(dev, &ndev->dev_tracker, GFP_KERNEL);
if (snmp6_alloc_dev(ndev) < 0) { if (dev != blackhole_netdev) {
netdev_dbg(dev, "%s: cannot allocate memory for statistics\n", if (snmp6_alloc_dev(ndev) < 0) {
__func__); netdev_dbg(dev, "%s: cannot allocate memory for statistics\n",
neigh_parms_release(&nd_tbl, ndev->nd_parms); __func__);
dev_put_track(dev, &ndev->dev_tracker); neigh_parms_release(&nd_tbl, ndev->nd_parms);
kfree(ndev); dev_put_track(dev, &ndev->dev_tracker);
return ERR_PTR(err); kfree(ndev);
} return ERR_PTR(err);
}
if (snmp6_register_dev(ndev) < 0) { if (snmp6_register_dev(ndev) < 0) {
netdev_dbg(dev, "%s: cannot create /proc/net/dev_snmp6/%s\n", netdev_dbg(dev, "%s: cannot create /proc/net/dev_snmp6/%s\n",
__func__, dev->name); __func__, dev->name);
goto err_release; goto err_release;
}
} }
/* One reference from device. */ /* One reference from device. */
refcount_set(&ndev->refcnt, 1); refcount_set(&ndev->refcnt, 1);
@ -445,25 +446,28 @@ static struct inet6_dev *ipv6_add_dev(struct net_device *dev)
ipv6_mc_init_dev(ndev); ipv6_mc_init_dev(ndev);
ndev->tstamp = jiffies; ndev->tstamp = jiffies;
err = addrconf_sysctl_register(ndev); if (dev != blackhole_netdev) {
if (err) { err = addrconf_sysctl_register(ndev);
ipv6_mc_destroy_dev(ndev); if (err) {
snmp6_unregister_dev(ndev); ipv6_mc_destroy_dev(ndev);
goto err_release; snmp6_unregister_dev(ndev);
goto err_release;
}
} }
/* protected by rtnl_lock */ /* protected by rtnl_lock */
rcu_assign_pointer(dev->ip6_ptr, ndev); rcu_assign_pointer(dev->ip6_ptr, ndev);
/* Join interface-local all-node multicast group */ if (dev != blackhole_netdev) {
ipv6_dev_mc_inc(dev, &in6addr_interfacelocal_allnodes); /* Join interface-local all-node multicast group */
ipv6_dev_mc_inc(dev, &in6addr_interfacelocal_allnodes);
/* Join all-node multicast group */ /* Join all-node multicast group */
ipv6_dev_mc_inc(dev, &in6addr_linklocal_allnodes); ipv6_dev_mc_inc(dev, &in6addr_linklocal_allnodes);
/* Join all-router multicast group if forwarding is set */
if (ndev->cnf.forwarding && (dev->flags & IFF_MULTICAST))
ipv6_dev_mc_inc(dev, &in6addr_linklocal_allrouters);
/* Join all-router multicast group if forwarding is set */
if (ndev->cnf.forwarding && (dev->flags & IFF_MULTICAST))
ipv6_dev_mc_inc(dev, &in6addr_linklocal_allrouters);
}
return ndev; return ndev;
err_release: err_release:
@ -7233,26 +7237,8 @@ int __init addrconf_init(void)
goto out_nowq; goto out_nowq;
} }
/* The addrconf netdev notifier requires that loopback_dev
* has it's ipv6 private information allocated and setup
* before it can bring up and give link-local addresses
* to other devices which are up.
*
* Unfortunately, loopback_dev is not necessarily the first
* entry in the global dev_base list of net devices. In fact,
* it is likely to be the very last entry on that list.
* So this causes the notifier registry below to try and
* give link-local addresses to all devices besides loopback_dev
* first, then loopback_dev, which cases all the non-loopback_dev
* devices to fail to get a link-local address.
*
* So, as a temporary fix, allocate the ipv6 structure for
* loopback_dev first by hand.
* Longer term, all of the dependencies ipv6 has upon the loopback
* device and it being up should be removed.
*/
rtnl_lock(); rtnl_lock();
idev = ipv6_add_dev(init_net.loopback_dev); idev = ipv6_add_dev(blackhole_netdev);
rtnl_unlock(); rtnl_unlock();
if (IS_ERR(idev)) { if (IS_ERR(idev)) {
err = PTR_ERR(idev); err = PTR_ERR(idev);

21
net/ipv6/route.c
View file

@ -156,14 +156,10 @@ void rt6_uncached_list_del(struct rt6_info *rt)
} }
} }
static void rt6_uncached_list_flush_dev(struct net *net, struct net_device *dev) static void rt6_uncached_list_flush_dev(struct net_device *dev)
{ {
struct net_device *loopback_dev = net->loopback_dev;
int cpu; int cpu;
if (dev == loopback_dev)
return;
for_each_possible_cpu(cpu) { for_each_possible_cpu(cpu) {
struct uncached_list *ul = per_cpu_ptr(&rt6_uncached_list, cpu); struct uncached_list *ul = per_cpu_ptr(&rt6_uncached_list, cpu);
struct rt6_info *rt; struct rt6_info *rt;
@ -174,7 +170,7 @@ static void rt6_uncached_list_flush_dev(struct net *net, struct net_device *dev)
struct net_device *rt_dev = rt->dst.dev; struct net_device *rt_dev = rt->dst.dev;
if (rt_idev->dev == dev) { if (rt_idev->dev == dev) {
rt->rt6i_idev = in6_dev_get(loopback_dev); rt->rt6i_idev = in6_dev_get(blackhole_netdev);
in6_dev_put(rt_idev); in6_dev_put(rt_idev);
} }
@ -371,13 +367,12 @@ static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
{ {
struct rt6_info *rt = (struct rt6_info *)dst; struct rt6_info *rt = (struct rt6_info *)dst;
struct inet6_dev *idev = rt->rt6i_idev; struct inet6_dev *idev = rt->rt6i_idev;
struct net_device *loopback_dev =
dev_net(dev)->loopback_dev;
if (idev && idev->dev != loopback_dev) { if (idev && idev->dev != blackhole_netdev) {
struct inet6_dev *loopback_idev = in6_dev_get(loopback_dev); struct inet6_dev *blackhole_idev = in6_dev_get(blackhole_netdev);
if (loopback_idev) {
rt->rt6i_idev = loopback_idev; if (blackhole_idev) {
rt->rt6i_idev = blackhole_idev;
in6_dev_put(idev); in6_dev_put(idev);
} }
} }
@ -4892,7 +4887,7 @@ void rt6_sync_down_dev(struct net_device *dev, unsigned long event)
void rt6_disable_ip(struct net_device *dev, unsigned long event) void rt6_disable_ip(struct net_device *dev, unsigned long event)
{ {
rt6_sync_down_dev(dev, event); rt6_sync_down_dev(dev, event);
rt6_uncached_list_flush_dev(dev_net(dev), dev); rt6_uncached_list_flush_dev(dev);
neigh_ifdown(&nd_tbl, dev); neigh_ifdown(&nd_tbl, dev);
} }