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

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Message-ID: <Ya6bj2nplJ57JPml@lunn.ch>
Date:   Tue, 7 Dec 2021 00:23:59 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v3 net-next 00/23] net: add preliminary netdev refcount
 tracking

On Sat, Dec 04, 2021 at 08:21:54PM -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> 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/

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.

Any ideas?

Thanks
	Andrew