Re: possible bug on ppp_async

On Wed, Jun 11, 2008 at 5:55 PM, Gustavo Fernando Padovan
<gfpadovan <at> gmail.com> wrote:
> On Mon, Jun 9, 2008 at 6:03 PM, Alan Cox <alan <at> redhat.com> wrote:
>> On Mon, Jun 09, 2008 at 03:23:33PM -0300, Gustavo Fernando Padovan wrote:
>>> The problem occurs when the execution enters on switch's default case
>>> and call tty_mode_ioctl() and the cmd is not TCGETS or cmd is not
>>> TCGETA. I don't know why this happens, but happens. On kernel 2.6.23
>>
>> Which ioctl is making it go silly ?
>>
>>> tty_mode_ioctl(). This is the unique real change between the two
>>> versions, the others are only code restructuring. Then I made this
>>> patch to revert part of changes and make modem works again. I don't
>>> know if this is correct. I just put the modem to work.
>>
>> It's very useful as we now know what change has had the effect, but not
>> what your pppd is doing which is breaking it (and thus where the real bug
>> may lie)
>>
>>> --- a/drivers/net/ppp_async.c.     2008-06-09 13:12:25.000000000 -0300
>>> +++ b/drivers/net/ppp_async.c      2008-06-09 13:15:57.000000000 -0300
>>>  <at>  <at>  -309,6 +309,11  <at>  <at> 
>>>                 err = 0;
>>>                 break;
>>>
>>> +       case TCGETS:
>>> +       case TCGETA:
>>> +               err = tty_mode_ioctl(tty, file, cmd, arg);
>>> +               break;
>>> +
>>>         case TCFLSH:
>>>                 /* flush our buffers and the serial port's buffer */
>>>                 if (arg == TCIOFLUSH || arg == TCOFLUSH)
>>>  <at>  <at>  -324,8 +329,7  <at>  <at> 
>>>                 break;
>>>
>>>         default:
>>> -               /* Try the various mode ioctls */
>>> -               err = tty_mode_ioctl(tty, file, cmd, arg);
>>> +               err = -ENOIOCTLCMD;
>>
>> Can you add a printk to log which ioctl calls end up here and what they
>> return (both with/without the patch). That should give the needed info to
>> identify what is being done and returned which then breaks it.
>
> I made two tries to connect with and without the patch. The tries are
> separated by a blank line.
>
> Debug without the patch:
>  [ 5955.465357] cmd = 21506 (TCSETS)
>  [ 5955.465369] err = 0
>  [ 5955.465372] ----------
>
>  [ 5987.058871] TCGETS
>  [ 5987.059094] err = 0
>  [ 5987.059276] ----------
>  [ 5987.059645] TCGETS
>  [ 5987.059786] err = 0
>  [ 5987.059863] ----------
>  [ 5987.060008] cmd = 21534 (TIOCGSERIAL)
>  [ 5987.060117] err = -515     (-ENOIOCTLCML)
>  [ 5987.060194] ----------
>  [ 5987.060283] cmd = 21506
>  [ 5987.060371] err = 0
>  [ 5987.060444] ----------
>  [ 5987.110619] cmd = 21506
>  [ 5987.110760] err = 0
>  [ 5987.110836] ----------
>  [ 5987.110949] cmd = 21506
>  [ 5987.111037] err = 0
>  [ 5987.111109] ----------
>  [ 5987.111192] TCGETS
>  [ 5987.111272] err = 0
>  [ 5987.111345] ----------
>  [ 6000.334483] cmd = 21506
>  [ 6000.334494] err = 0
>  [ 6000.334496] ----------
>
> Debug with the patch:
> [ 8207.865204] cmd = 21506 (TCSETS)
> [ 8207.865213] err = -515
> [ 8207.865215] ----------
>
> [ 8866.939075] cmd = 21506
> [ 8866.939084] err = -515
> [ 8866.939086] ----------
>
> The problem seems the ioctl TCSETS, with the patch (and on kernel
> 2.6.23) it returns immediately, and on kernel 2.6.24 (without the
> patch) it goes to tty_mode_ioctl().

This patch also resolves the 'bug'. It intercepts TCSETS on
switch(cmd) and return -ENOIOCTLCMD;

--- a/drivers/net/ppp_async.c        2008-06-13 11:59:10.000000000 -0300
+++ b/drivers/net/ppp_async.c     2008-06-13 11:58:34.000000000 -0300
 <at>  <at>  -323,6 +323,10  <at>  <at> 
                err = 0;
                break;

+    case TCSETS:
+        err = -ENOIOCTLCMD;
+        break;
+
        default:
                /* Try the various mode ioctls */
                err = tty_mode_ioctl(tty, file, cmd, arg);

>
>>
>> From that I can work out what is going on and what the right fix may be.
>>
>> Alan
>>
>>
>
>
>
> --
> ----------------------------------------------
> Gustavo Fernando Padovan
> Engenharia de Computação 2006
> LAS - Laboratório de Administração e Segurança de Sistemas
> Instituto de Computação - UNICAMP
>
> gfpadovan <at> gmail.com
> ra061316 <at> students.ic.unicamp.br
> pao <at> jabber.org
> -------------------------------------------
>
> Seja Livre, use Software Livre
>

--

-- 
----------------------------------------------
Gustavo Fernando Padovan
Engenharia de Computação 2006
LAS - Laboratório de Administração e Segurança de Sistemas
Instituto de Computação - UNICAMP

gfpadovan <at> gmail.com
ra061316 <at> students.ic.unicamp.br
pao <at> jabber.org
-------------------------------------------

Seja Livre, use Software Livre
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