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Subject: Re: Urgent: BUG: PPP ioctl Transport endpoint is not connected
From:   Martin Zaharinov <micron10@gmail.com>
In-Reply-To: <20201209181033.GB21199@linux.home>
Date:   Thu, 10 Dec 2020 09:16:24 +0200
Cc:     "linux-kernel@vger kernel. org" <linux-kernel@vger.kernel.org>,
        Eric Dumazet <eric.dumazet@gmail.com>, netdev@vger.kernel.org
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Message-Id: <FDF5FB97-DB82-4DFD-AC05-28F60C6D166F@gmail.com>
References: <83C781EB-5D66-426E-A216-E1B846A3EC8A@gmail.com>
 <20201209164013.GA21199@linux.home>
 <1E49F9F8-0325-439E-B200-17C8CB6A3CBE@gmail.com>
 <20201209181033.GB21199@linux.home>
To:     Guillaume Nault <gnault@redhat.com>
Precedence: bulk

And one other=20
=46rom other mailing I see you send patch to Denys Fedoryshchenko this =
patch is :=20

diff --git a/drivers/net/ppp/ppp_generic.c=20
b/drivers/net/ppp/ppp_generic.c

index 255a5def56e9..2acf4b0eabd1 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -3161,6 +3161,15 @@ ppp_connect_channel(struct channel *pch, int=20
unit)

goto outl;

ppp_lock(ppp);
+   spin_lock_bh(>downl);
+   if (!pch->chan) {
+   /* Don't connect unregistered channels */
+   ppp_unlock(ppp);
+   spin_unlock_bh(>downl);
+   ret =3D -ENOTCONN;
+   goto outl;
+   }
+   spin_unlock_bh(>downl);
if (pch->file.hdrlen > ppp->file.hdrlen)
ppp->file.hdrlen =3D pch->file.hdrlen;
hdrlen =3D pch->file.hdrlen + 2;   /* for protocol bytes */


But in official stable kernel three In ppp_generic.c is this :=20

spin_lock_bh(&pch->downl);=20
	if (!pch->chan) {=20
	/* Don't connect unregistered channels */=20
	spin_unlock_bh(&pch->downl);=20
	ppp_unlock(ppp);=20
	ret =3D -ENOTCONN;=20
	goto outl; }
	spin_unlock_bh(&pch->downl);=09


It is  normal to unlock ppp after spin_unlock ?
shouldn't it be as you wrote it?
In your patch first :

+   ppp_unlock(ppp);
+   spin_unlock_bh(>downl);

But in stable kernel is :=20

spin_unlock_bh(&pch->downl);=20
	ppp_unlock(ppp);=20


> On 9 Dec 2020, at 20:10, Guillaume Nault <gnault@redhat.com> wrote:
>=20
> On Wed, Dec 09, 2020 at 06:57:44PM +0200, Martin Zaharinov wrote:
>>> On 9 Dec 2020, at 18:40, Guillaume Nault <gnault@redhat.com> wrote:
>>> On Wed, Dec 09, 2020 at 04:47:52PM +0200, Martin Zaharinov wrote:
>>>> Hi All
>>>>=20
>>>> I have problem with latest kernel release=20
>>>> And the problem is base on this late problem :
>>>>=20
>>>>=20
>>>> =
https://www.mail-archive.com/search?l=3Dnetdev@vger.kernel.org&q=3Dsubject=
:%22Re%5C%3A+ppp%5C%2Fpppoe%2C+still+panic+4.15.3+in+ppp_push%22&o=3Dnewes=
t&f=3D1
>>>>=20
>>>> I have same problem in kernel 5.6 > now I use kernel 5.9.13 and =
have same problem.
>>>>=20
>>>>=20
>>>> In kernel 5.9.13 now don=E2=80=99t have any crashes in dimes but in =
one moment accel service stop with defunct and in log have many of this =
line :
>>>>=20
>>>>=20
>>>> error: vlan608: ioctl(PPPIOCCONNECT): Transport endpoint is not =
connected
>>>> error: vlan617: ioctl(PPPIOCCONNECT): Transport endpoint is not =
connected
>>>> error: vlan679: ioctl(PPPIOCCONNECT): Transport endpoint is not =
connected
>>>>=20
>>>> In one moment connected user bump double or triple and after that =
service defunct and need wait to drop all session to start .
>>>>=20
>>>> I talk with accel-ppp team and they said this is kernel related =
problem and to back to kernel 4.14 there is not this problem.
>>>>=20
>>>> Problem is come after kernel 4.15 > and not have solution to this =
moment.
>>>=20
>>> I'm sorry, I don't understand.
>>> Do you mean that v4.14 worked fine (no crash, no ioctl() error)?
>>> Did the problem start appearing in v4.15? Or did v4.15 work and the
>>> problem appeared in v4.16?
>>=20
>> In Telegram group I talk with Sergey and Dimka and told my the =
problem is come after changes from 4.14 to 4.15=20
>> Sergey write this : "as I know, there was a similar issue in kernel =
4.15 so maybe it is still not fixed"
>=20
> Ok, but what is your experience? Do you have a kernel version where
> accel-ppp reports no ioctl() error and doesn't crash the kernel?
>=20
> There wasn't a lot of changes between 4.14 and 4.15 for PPP.
> The only PPP patch I can see that might have been risky is commit
> 0171c4183559 ("ppp: unlock all_ppp_mutex before registering device").
>=20
>> I don=E2=80=99t have options to test with this old kernel 4.14.xxx i =
don=E2=80=99t have support for them.
>>=20
>>=20
>>>=20
>>>> Please help to find the problem.
>>>>=20
>>>> Last time in link I see is make changes in ppp_generic.c=20
>>>>=20
>>>> ppp_lock(ppp);
>>>>       spin_lock_bh(&pch->downl);
>>>>       if (!pch->chan) {
>>>>               /* Don't connect unregistered channels */
>>>>               spin_unlock_bh(&pch->downl);
>>>>               ppp_unlock(ppp);
>>>>               ret =3D -ENOTCONN;
>>>>               goto outl;
>>>>       }
>>>>       spin_unlock_bh(&pch->downl);
>>>>=20
>>>>=20
>>>> But this fix only to don=E2=80=99t display error and freeze system=20=

>>>> The problem is stay and is to big.
>>>=20
>>> Do you use accel-ppp's unit-cache option? Does the problem go away =
if
>>> you stop using it?
>>>=20
>>=20
>> No I don=E2=80=99t use unit-cache , if I set unit-cache accel-ppp =
defunct same but user Is connect and disconnet more fast.
>>=20
>> The problem is same with unit and without .=20
>> Only after this patch I don=E2=80=99t see error in dimes but this is =
not solution.
>=20
> Soryy, what's "in dimes"?
> Do you mean that reverting commit 77f840e3e5f0 ("ppp: prevent
> unregistered channels from connecting to PPP units") fixes your =
problem?
>=20
>> In network have customer what have power cut problem, when drop 600 =
user and back Is normal but in this moment kernel is locking and start =
to make this :=20
>> sessions:
>>  starting: 4235
>>  active: 3882
>>  finishing: 378
>> The problem is starting session is not real user normal user in this =
server is ~4k customers .
>=20
> What type of session is it? L2TP, PPPoE, PPTP?
>=20
>> I use pppd_compat .
>>=20
>> Any idea ?
>>=20
>>>>=20
>>>> Please help to fix.
>> Martin