kwboot : bug when board stops acking

[Pali Rohár]

Hello Stephane!

On Wednesday 08 January 2020 15:21:12 SC wrote:
> Hi list,
> 
> I think there's a bug in kwboot.
> I have a faulty board that stops acking xmodem frames after a certain number of packets and kwboot 
> instead of exiting continues to send frames up to 100%.
> With the one second retry timer it's very long! More than 2 hours :-(

I saw very similar bugs in kwboot and together with Marek we fixed lot
of issues in kwboot.

Could you test if last version of kwboot from U-Boot git master branch
has still same or similar issue?

> The bug is in the kwboot_xm_sendblock() fonction : 
> https://gitlab.denx.de/u-boot/u-boot/blob/master/tools/kwboot.c#L375
> kwboot_tty_recv detects the timeout but the return value is based on the last character received 
> (line 403)
> The variable c is not initialized so if it keeps the previous value which is ACK => rc=0 => infinite 
> loop
> 
> There are several ways to fix the bug:
> * Surround the "switch(c)" with a test:
>   if ( !((rc == -1) && (errno == ETIMEDOUT)) ) {
>          rc = -1;
>          switch (c) {
>          case ACK:
>              rc = 0;
>              break;
>          case NAK:
>              errno = EBADMSG;
>              break;
>          case CAN:
>              errno = ECANCELED;
>              break;
>          default:
>              errno = EPROTO;
>              break;
>          }
>      }
>      return rc;
> * In the case of a TIMEOUT set c to a specific value and add the case in the switch
> 
> Do you agree with my diagnosis?
> What is the best solution to fix this bug?
> Should I provide a patch?
> 
> Thank you,
> Stephane