Re: [PATCH v3 net-next 00/23] net: add preliminary netdev refcount tracking

On Mon, Dec 06, 2021 at 04:04:19PM -0800, Eric Dumazet wrote:

On Mon, Dec 6, 2021 at 4:00 PM Andrew Lunn [off-list ref] wrote:

quoted

On Mon, Dec 06, 2021 at 03:44:57PM -0800, Eric Dumazet wrote:

quoted

On Mon, Dec 6, 2021 at 3:24 PM Andrew Lunn [off-list ref] wrote:

quoted

On Sat, Dec 04, 2021 at 08:21:54PM -0800, Eric Dumazet wrote:

quoted

From: Eric Dumazet <redacted>

Two first patches add a generic infrastructure, that will be used
to get tracking of refcount increments/decrements.

Hi Eric

Using this i found:

[  774.108901] unregister_netdevice: waiting for eth0 to become free. Usage count = 4
[  774.110864] leaked reference.
[  774.110874]  dst_alloc+0x7a/0x180
[  774.110887]  ip6_dst_alloc+0x27/0x90
[  774.110894]  ip6_pol_route+0x257/0x430
[  774.110900]  ip6_pol_route_output+0x19/0x20
[  774.110905]  fib6_rule_lookup+0x18b/0x270
[  774.110914]  ip6_route_output_flags_noref+0xaa/0x110
[  774.110918]  ip6_route_output_flags+0x32/0xa0
[  774.110922]  ip6_dst_lookup_tail.constprop.0+0x181/0x240
[  774.110929]  ip6_dst_lookup_flow+0x43/0xa0
[  774.110934]  inet6_csk_route_socket+0x166/0x200
[  774.110943]  inet6_csk_xmit+0x56/0x130
[  774.110946]  __tcp_transmit_skb+0x53b/0xc30
[  774.110953]  __tcp_send_ack.part.0+0xc6/0x1a0
[  774.110958]  tcp_send_ack+0x1c/0x20
[  774.110964]  __tcp_ack_snd_check+0x42/0x200
[  774.110968]  tcp_rcv_established+0x27a/0x6f0
[  774.110973] leaked reference.
[  774.110975]  ipv6_add_dev+0x13e/0x4f0
[  774.110982]  addrconf_notify+0x2ca/0x950
[  774.110989]  raw_notifier_call_chain+0x49/0x60
[  774.111000]  call_netdevice_notifiers_info+0x50/0x90
[  774.111007]  __dev_change_net_namespace+0x30d/0x6c0
[  774.111016]  do_setlink+0xdc/0x10b0
[  774.111024]  __rtnl_newlink+0x608/0xa10
[  774.111031]  rtnl_newlink+0x49/0x70
[  774.111038]  rtnetlink_rcv_msg+0x14f/0x380
[  774.111046]  netlink_rcv_skb+0x55/0x100
[  774.111053]  rtnetlink_rcv+0x15/0x20
[  774.111059]  netlink_unicast+0x230/0x340
[  774.111064]  netlink_sendmsg+0x252/0x4b0
[  774.111075]  sock_sendmsg+0x65/0x70
[  774.111080]  ____sys_sendmsg+0x24e/0x290
[  774.111084]  ___sys_sendmsg+0x81/0xc0

I'm using GNS3 to simulate a network topology. So a collection of veth
pairs, bridges and tap interfaces spread over a few namespaces. The
network being simulated uses Segment Routing. And traceroute might also
involved in this somehow. I have 3 patches applied, to make traceroute
actually work when SRv6 is being used. You can find v3 here:

https://lore.kernel.org/netdev/20211203162926.3680281-3-andrew@lunn.ch/T/ (local)

I'm not sure if these patches are part of the problem or not. None of
the traces i've seen are directly on the ICMP path. traceroute is
using udp, and one of the traces above is for tcp, and the other looks
like it is moving an interface into a different namespace?

This is net-next from today.

I do not understand, net-next does not contain this stuff yet ?

Hi Eric

I'm getting warnings like:

unregister_netdevice: waiting for eth0 to become free. Usage count = 4

which is what your patchset is supposed to help fix. So i applied what
has been posted so far, in the hope it would find the issue. It is
reporting something...

I thought you were telling me that you got these new reports after the
patch set being applied ?

Hi Eric

No. I applied them.

Or were they happening because of your other changes ?

Hard to say. It looks like some sort of race condition. Sometimes when
i shut down the GNS3 simulation, i get the issues, sometimes not. I
don't have a good enough feeling to say either way, is it an existing
problem, or it is my code which is triggering it.

quoted

quoted

I have other patches, this work is still in progress.

Is what is currently posted usable? Do these traces above point at the
real problem i have, or because there are more patches, i should not
trust the output?

I think I have not worked yet on the XFRM side in patch set 1.
Are you using XFRM ?

I don't think SRv6 uses XFRM.

  Andrew