netdev - Re: Urgent Bug report: PPPoE ioctl(PPPIOCCONNECT): Transport endpoint is not connected

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Date:   Wed, 11 Aug 2021 18:40:01 +0200
From:   Guillaume Nault <gnault@...hat.com>
To:     Martin Zaharinov <micron10@...il.com>
Cc:     Pali Rohár <pali@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: Urgent  Bug report: PPPoE ioctl(PPPIOCCONNECT): Transport
 endpoint is not connected

On Tue, Aug 10, 2021 at 09:27:14PM +0300, Martin Zaharinov wrote:
> Add Guillaume Nault
> 
> > On 9 Aug 2021, at 18:15, Pali Rohár <pali@...nel.org> wrote:
> > 
> > On Sunday 08 August 2021 18:29:30 Martin Zaharinov wrote:
> >>>>>> [2021-08-05 13:52:05.294] vlan912: 24b205903d09718e: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:05.298] vlan912: 24b205903d097162: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:05.626] vlan641: 24b205903d09711b: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:11.000] vlan912: 24b205903d097105: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:17.852] vlan912: 24b205903d0971ae: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:21.113] vlan641: 24b205903d09715b: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:27.963] vlan912: 24b205903d09718d: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:30.249] vlan496: 24b205903d097184: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:30.992] vlan420: 24b205903d09718a: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:33.937] vlan640: 24b205903d0971cd: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:40.032] vlan912: 24b205903d097182: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:40.420] vlan912: 24b205903d0971d5: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:42.799] vlan912: 24b205903d09713a: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:42.799] vlan614: 24b205903d0971e5: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:43.102] vlan912: 24b205903d097190: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:43.850] vlan479: 24b205903d097153: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:43.850] vlan479: 24b205903d097141: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:43.852] vlan912: 24b205903d097198: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:43.977] vlan637: 24b205903d097148: ioctl(PPPIOCCONNECT): Transport endpoint is not connected
> >>>>>> [2021-08-05 13:52:44.528] vlan637: 24b205903d0971c3: ioctl(PPPIOCCONNECT): Transport endpoint is not connected

The PPPIOCCONNECT ioctl returns -ENOTCONN if the ppp channel has been
unregistered.

>From a user space point of view, this means that accel-ppp establishes
PPPoE sessions, starts negociating PPP connection parameters on top of
them (LCP and authentication) and finally the PPPoE sessions get
disconnected before accel-ppp connects them to ppp units (units are
roughly the "pppX" network devices).

Unregistration of PPPoE channels can happen for the following reasons:

  * Changing some parameters of the network interface used by the
    PPPoE connection: MAC address, MTU, bringing the device down.

  * Reception of a PADT (PPPoE disconnection message sent from the peer).

  * Closing the PPPoE socket.

  * Re-connecting a PPPoE socket with a different session ID (this
    unregisters the previous channel and creates a new one, so that
    shouldn't be the problem you're facing here).

Given that this seems to affect all PPPoE connections, I guess
something happened to the underlying network interface (1st bullet
point).