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Message-Id: <20220210214231.2420942-3-eric.dumazet@gmail.com>
Date: Thu, 10 Feb 2022 13:42:29 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Mahesh Bandewar <maheshb@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 2/4] ipv6: give an IPv6 dev to blackhole_netdev
From: Eric Dumazet <edumazet@...gle.com>
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@...gle.com>
Cc: Mahesh Bandewar <maheshb@...gle.com>
---
net/ipv6/addrconf.c | 78 +++++++++++++++++++--------------------------
net/ipv6/route.c | 21 +++++-------
2 files changed, 40 insertions(+), 59 deletions(-)
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 4f402bc38f056e08f3761e63a7bc7a51e54e9384..02d31d4fcab3b3d529c4fe3260216ecee1108e82 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -372,7 +372,7 @@ static struct inet6_dev *ipv6_add_dev(struct net_device *dev)
ASSERT_RTNL();
- if (dev->mtu < IPV6_MIN_MTU)
+ if (dev->mtu < IPV6_MIN_MTU && dev != blackhole_netdev)
return ERR_PTR(-EINVAL);
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 */
dev_hold_track(dev, &ndev->dev_tracker, GFP_KERNEL);
- if (snmp6_alloc_dev(ndev) < 0) {
- netdev_dbg(dev, "%s: cannot allocate memory for statistics\n",
- __func__);
- neigh_parms_release(&nd_tbl, ndev->nd_parms);
- dev_put_track(dev, &ndev->dev_tracker);
- kfree(ndev);
- return ERR_PTR(err);
- }
+ if (dev != blackhole_netdev) {
+ if (snmp6_alloc_dev(ndev) < 0) {
+ netdev_dbg(dev, "%s: cannot allocate memory for statistics\n",
+ __func__);
+ neigh_parms_release(&nd_tbl, ndev->nd_parms);
+ dev_put_track(dev, &ndev->dev_tracker);
+ kfree(ndev);
+ return ERR_PTR(err);
+ }
- if (snmp6_register_dev(ndev) < 0) {
- netdev_dbg(dev, "%s: cannot create /proc/net/dev_snmp6/%s\n",
- __func__, dev->name);
- goto err_release;
+ if (snmp6_register_dev(ndev) < 0) {
+ netdev_dbg(dev, "%s: cannot create /proc/net/dev_snmp6/%s\n",
+ __func__, dev->name);
+ goto err_release;
+ }
}
-
/* One reference from device. */
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);
ndev->tstamp = jiffies;
- err = addrconf_sysctl_register(ndev);
- if (err) {
- ipv6_mc_destroy_dev(ndev);
- snmp6_unregister_dev(ndev);
- goto err_release;
+ if (dev != blackhole_netdev) {
+ err = addrconf_sysctl_register(ndev);
+ if (err) {
+ ipv6_mc_destroy_dev(ndev);
+ snmp6_unregister_dev(ndev);
+ goto err_release;
+ }
}
/* protected by rtnl_lock */
rcu_assign_pointer(dev->ip6_ptr, ndev);
- /* Join interface-local all-node multicast group */
- ipv6_dev_mc_inc(dev, &in6addr_interfacelocal_allnodes);
+ if (dev != blackhole_netdev) {
+ /* Join interface-local all-node multicast group */
+ ipv6_dev_mc_inc(dev, &in6addr_interfacelocal_allnodes);
- /* Join all-node multicast group */
- 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-node multicast group */
+ 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);
+ }
return ndev;
err_release:
@@ -7233,26 +7237,8 @@ int __init addrconf_init(void)
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();
- idev = ipv6_add_dev(init_net.loopback_dev);
+ idev = ipv6_add_dev(blackhole_netdev);
rtnl_unlock();
if (IS_ERR(idev)) {
err = PTR_ERR(idev);
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 53acd1568ebcceb1a1697579ed505cefc7a35a65..5fc1a1de9481c859adc332746ccfcf237db6541f 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -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;
- if (dev == loopback_dev)
- return;
-
for_each_possible_cpu(cpu) {
struct uncached_list *ul = per_cpu_ptr(&rt6_uncached_list, cpu);
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;
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);
}
@@ -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 inet6_dev *idev = rt->rt6i_idev;
- struct net_device *loopback_dev =
- dev_net(dev)->loopback_dev;
- if (idev && idev->dev != loopback_dev) {
- struct inet6_dev *loopback_idev = in6_dev_get(loopback_dev);
- if (loopback_idev) {
- rt->rt6i_idev = loopback_idev;
+ if (idev && idev->dev != blackhole_netdev) {
+ struct inet6_dev *blackhole_idev = in6_dev_get(blackhole_netdev);
+
+ if (blackhole_idev) {
+ rt->rt6i_idev = blackhole_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)
{
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);
}
--
2.35.1.265.g69c8d7142f-goog
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