linux.git/net/core/dst.c, branch v4.12

Fix an intermittent pr_emerg warning about lo becoming free.

2017-06-09T16:27:28+00:00

It looks like this:

Message from syslogd@flamingo at Apr 26 00:45:00 ...
 kernel:unregister_netdevice: waiting for lo to become free. Usage count = 4

They seem to coincide with net namespace teardown.

The message is emitted by netdev_wait_allrefs().

Forced a kdump in netdev_run_todo, but found that the refcount on the lo
device was already 0 at the time we got to the panic.

Used bcc to check the blocking in netdev_run_todo.  The only places
where we're off cpu there are in the rcu_barrier() and msleep() calls.
That behavior is expected.  The msleep time coincides with the amount of
time we spend waiting for the refcount to reach zero; the rcu_barrier()
wait times are not excessive.

After looking through the list of callbacks that the netdevice notifiers
invoke in this path, it appears that the dst_dev_event is the most
interesting.  The dst_ifdown path places a hold on the loopback_dev as
part of releasing the dev associated with the original dst cache entry.
Most of our notifier callbacks are straight-forward, but this one a)
looks complex, and b) places a hold on the network interface in
question.

I constructed a new bcc script that watches various events in the
liftime of a dst cache entry.  Note that dst_ifdown will take a hold on
the loopback device until the invalidated dst entry gets freed.

[      __dst_free] on DST: ffff883ccabb7900 IF tap1008300eth0 invoked at 1282115677036183
    __dst_free
    rcu_nocb_kthread
    kthread
    ret_from_fork
Acked-by: Eric Dumazet 

Signed-off-by: David S. Miller

ipv4: add reference counting to metrics

2017-05-26T18:57:07+00:00

Andrey Konovalov reported crashes in ipv4_mtu()

I could reproduce the issue with KASAN kernels, between
10.246.7.151 and 10.246.7.152 :

1) 20 concurrent netperf -t TCP_RR -H 10.246.7.152 -l 1000 &

2) At the same time run following loop :
while :
do
 ip ro add 10.246.7.152 dev eth0 src 10.246.7.151 mtu 1500
 ip ro del 10.246.7.152 dev eth0 src 10.246.7.151 mtu 1500
done

Cong Wang attempted to add back rt->fi in commit
82486aa6f1b9 ("ipv4: restore rt->fi for reference counting")
but this proved to add some issues that were complex to solve.

Instead, I suggested to add a refcount to the metrics themselves,
being a standalone object (in particular, no reference to other objects)

I tried to make this patch as small as possible to ease its backport,
instead of being super clean. Note that we believe that only ipv4 dst
need to take care of the metric refcount. But if this is wrong,
this patch adds the basic infrastructure to extend this to other
families.

Many thanks to Julian Anastasov for reviewing this patch, and Cong Wang
for his efforts on this problem.

Fixes: 2860583fe840 ("ipv4: Kill rt->fi")
Signed-off-by: Eric Dumazet 
Reported-by: Andrey Konovalov 
Reviewed-by: Julian Anastasov 
Acked-by: Cong Wang 
Signed-off-by: David S. Miller

net: pending_confirm is not used anymore

2017-02-07T18:07:47+00:00

When same struct dst_entry can be used for many different
neighbours we can not use it for pending confirmations.
As last step, we can remove the pending_confirm flag.

Reported-by: YueHaibing 
Fixes: 5110effee8fd ("net: Do delayed neigh confirmation.")
Fixes: f2bb4bedf35d ("ipv4: Cache output routes in fib_info nexthops.")
Signed-off-by: Julian Anastasov 
Acked-by: Eric Dumazet 
Signed-off-by: David S. Miller

net: add dst_cache to ovs vxlan lwtunnel

2016-02-17T01:21:48+00:00

In case of UDP traffic with datagram length
below MTU this give about 2% performance increase
when tunneling over ipv4 and about 60% when tunneling
over ipv6

Signed-off-by: Paolo Abeni 
Suggested-and-acked-by: Hannes Frederic Sowa 
Signed-off-by: David S. Miller

net: possible use after free in dst_release

2016-01-06T20:00:27+00:00

dst_release should not access dst->flags after decrementing
__refcnt to 0. The dst_entry may be in dst_busy_list and
dst_gc_task may dst_destroy it before dst_release gets a chance
to access dst->flags.

Fixes: d69bbf88c8d0 ("net: fix a race in dst_release()")
Fixes: 27b75c95f10d ("net: avoid RCU for NOCACHE dst")
Signed-off-by: Francesco Ruggeri 
Acked-by: Eric Dumazet 
Signed-off-by: David S. Miller

net: fix a race in dst_release()

2015-11-10T02:55:48+00:00

Only cpu seeing dst refcount going to 0 can safely
dereference dst->flags.

Otherwise an other cpu might already have freed the dst.

Fixes: 27b75c95f10d ("net: avoid RCU for NOCACHE dst")
Reported-by: Greg Thelen 
Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

dst: Pass net into dst->output

2015-10-08T11:27:03+00:00

The network namespace is already passed into dst_output pass it into
dst->output lwt->output and friends.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: David S. Miller

tun_dst: Remove opts_size

2015-09-01T04:23:42+00:00

opts_size is only written and never read. Following patch
removes this unused variable.

Signed-off-by: Pravin B Shelar 
Signed-off-by: David S. Miller

route: fix a use-after-free

2015-08-25T21:29:19+00:00

This patch fixes the following crash:

 general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC
 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.2.0-rc7+ #166
 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
 task: ffff88010656d280 ti: ffff880106570000 task.ti: ffff880106570000
 RIP: 0010:[]  [] dst_destroy+0xa6/0xef
 RSP: 0018:ffff880107603e38  EFLAGS: 00010202
 RAX: 0000000000000001 RBX: ffff8800d225a000 RCX: ffffffff82250fd0
 RDX: 0000000000000001 RSI: ffffffff82250fd0 RDI: 6b6b6b6b6b6b6b6b
 RBP: ffff880107603e58 R08: 0000000000000001 R09: 0000000000000001
 R10: 000000000000b530 R11: ffff880107609000 R12: 0000000000000000
 R13: ffffffff82343c40 R14: 0000000000000000 R15: ffffffff8182fb4f
 FS:  0000000000000000(0000) GS:ffff880107600000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
 CR2: 00007fcabd9d3000 CR3: 00000000d7279000 CR4: 00000000000006e0
 Stack:
  ffffffff82250fd0 ffff8801077d6f00 ffffffff82253c40 ffff8800d225a000
  ffff880107603e68 ffffffff8182fb5d ffff880107603f08 ffffffff810d795e
  ffffffff810d7648 ffff880106574000 ffff88010656d280 ffff88010656d280
 Call Trace:
  
  [] dst_destroy_rcu+0xe/0x1d
  [] rcu_process_callbacks+0x618/0x7eb
  [] ? rcu_process_callbacks+0x302/0x7eb
  [] ? dst_gc_task+0x1eb/0x1eb
  [] __do_softirq+0x178/0x39f
  [] irq_exit+0x41/0x95
  [] smp_apic_timer_interrupt+0x34/0x40
  [] apic_timer_interrupt+0x6d/0x80
  
  [] ? default_idle+0x21/0x32
  [] ? default_idle+0x1f/0x32
  [] arch_cpu_idle+0xf/0x11
  [] default_idle_call+0x1f/0x21
  [] cpu_startup_entry+0x1ad/0x273
  [] start_secondary+0x135/0x156

dst is freed right before lwtstate_put(), this is not correct...

Fixes: 61adedf3e3f1 ("route: move lwtunnel state to dst_entry")
Acked-by: Jiri Benc 
Signed-off-by: Cong Wang 
Signed-off-by: Cong Wang 
Signed-off-by: David S. Miller

route: move lwtunnel state to dst_entry

2015-08-20T22:42:36+00:00

Currently, the lwtunnel state resides in per-protocol data. This is
a problem if we encapsulate ipv6 traffic in an ipv4 tunnel (or vice versa).
The xmit function of the tunnel does not know whether the packet has been
routed to it by ipv4 or ipv6, yet it needs the lwtstate data. Moving the
lwtstate data to dst_entry makes such inter-protocol tunneling possible.

As a bonus, this brings a nice diffstat.

Signed-off-by: Jiri Benc 
Acked-by: Roopa Prabhu 
Acked-by: Thomas Graf 
Signed-off-by: David S. Miller