ACK: [F/OEM-5.6][SRU][PATCH 0/1] l2tp: remove skb_dst_set() from l2tp_xmit_skb()

Stefan Bader stefan.bader at canonical.com
Thu Mar 18 08:42:02 UTC 2021


On 16.03.21 12:06, Po-Hsu Lin wrote:
> [Impact]
> While debugging bug 1880631, I found that this l2tp.sh test from
> kselftest/net will cause the dmesg output on Focal OEM 5.6 kernel
> flooded with:
> "unregister_netdevice: waiting for eth0 to become free. Usage count = 1"
> for about every 10 seconds.
> 
> Test log:
> $ sudo ./l2tp.sh
> TEST: IPv4 basic L2TP tunnel                                        [ OK ]
> TEST: IPv4 route through L2TP tunnel                                [ OK ]
> TEST: IPv6 basic L2TP tunnel                                        [ OK ]
> TEST: IPv6 route through L2TP tunnel                                [ OK ]
> TEST: IPv4 basic L2TP tunnel - with IPsec                           [ OK ]
> TEST: IPv4 route through L2TP tunnel - with IPsec                   [ OK ]
> TEST: IPv6 basic L2TP tunnel - with IPsec                           [ OK ]
> TEST: IPv6 route through L2TP tunnel - with IPsec                   [ OK ]
> TEST: IPv4 basic L2TP tunnel                                        [ OK ]
> TEST: IPv4 route through L2TP tunnel                                [ OK ]
> TEST: IPv6 basic L2TP tunnel - with IPsec                           [ OK ]
> TEST: IPv6 route through L2TP tunnel - with IPsec                   [ OK ]
> TEST: IPv4 basic L2TP tunnel - after IPsec teardown                 [ OK ]
> TEST: IPv4 route through L2TP tunnel - after IPsec teardown         [ OK ]
> TEST: IPv6 basic L2TP tunnel - after IPsec teardown                 [ OK ]
> TEST: IPv6 route through L2TP tunnel - after IPsec teardown         [ OK ]
> 
> Tests passed:  16
> Tests failed:   0
> 
> dmesg output:
> $ dmesg
> [  708.560589] eth1: renamed from tmp
> [  708.587396] IPv6: ADDRCONF(NETDEV_CHANGE): eth1: link becomes ready
> [  708.587472] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
> [  708.616950] eth2: renamed from tmp
> [  708.643341] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
> [  708.687057] l2tp_core: L2TP core driver, V2.0
> [  708.689380] l2tp_netlink: L2TP netlink interface
> [  708.695479] l2tp_ip: L2TP IP encapsulation support (L2TPv3)
> [  708.700061] l2tp_eth: L2TP ethernet pseudowire support (L2TPv3)
> [  708.726295] l2tp_ip6: L2TP IP encapsulation support for IPv6 (L2TPv3)
> [  708.788973] Initializing XFRM netlink socket
> [  719.448364] unregister_netdevice: waiting for eth0 to become free. Usage count = 1
> [  729.528359] unregister_netdevice: waiting for eth0 to become free. Usage count = 1
> [  739.608359] unregister_netdevice: waiting for eth0 to become free. Usage count = 1
> 
> [Fix]
> * 27d53323664c54 ("l2tp: remove skb_dst_set() from l2tp_xmit_skb()")
> 
> We have this patch in all of our generic kernels and OEM-5.10, thus
> for now I can see just OEM-5.6 is affected. For which this patch can
> be cherry-picked.
> 
> [Test Case]
> This can tested with the l2tp.sh script in the kernel tree:
> # sh ./tools/testing/selftests/net/l2tp.sh
> 
> With the patched kernel, it won't get flooded with that
> unregister_netdevice message anymore.
> 
> Also, I have it tested with ubuntu_stress_smoke_tests as well, to
> ensure the sctp stressor won't trigger any issue like in bug 1854968.
> 
> A test kernel can be found here:
> https://people.canonical.com/~phlin/kernel/lp-1919277-l2tp/
> 
> [Where problems could occur]
> This change is testable. A quick search didn't show any know issue
> regarding this patch. And with the same fix running in different
> generic kernel for a while I think the regression potential can be
> considered as low.
> 
> Xin Long (1):
>    l2tp: remove skb_dst_set() from l2tp_xmit_skb()
> 
>   net/l2tp/l2tp_core.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
> 
Acked-by: Stefan Bader <stefan.bader at canonical.com>

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