[linux-dvb] Re: WANTED : KaxTV testers

[Christophe Thommeret <hftom@free.fr>]

Le Dimanche 02 Janvier 2005 12:08, Jim Darby a écrit :
> Thanks for the fix Christophe.
>
> Just a quick update from this end. I replaced the EIT parsing code with
> some really simple stuff that just checked to see if the length field in
> the EIT header matched the actual amount of received data. After having
> recorded MANY hours of stuff over Xmas and the New Year this never
> tripped. Looks like the at least this bit is correct. This is also a
> pretty clear indication that the crashing problem was with the EIT
> parser.
>
> I've just had a quick look at your code and noticed that your safe
> buffer check checks to see if we've gone over the maximum possible
> length rather than the actual length of the buffer. This should stop
> crashing but might not stop all possible corruptions.

of course, you can still get garbage, but some events are nothing more :)

> Would you like me to have a go at writing a really ultra-robust EIT
> parser? I was thinking along the lines of writing code of the sort I'd
> write for web sites and the such like that assume that the incoming data
> is malicious. If it finds a dubious EIT it could then dump/print it and
> we can then analyse them at our leisure and see what we can find.
> Basically I think we just have to assume that the incoming EIT (and
> indeed most other data) is not merely potentially corrupt but probably
> fresh from some virus writing who has seen the source of kaxtv and has
> managed to get broadcasters to send out bad EITs specifically crafted to
> crash the code! This might not actually be true, but it's a good working
> start.

Go on, Jim. Just keep in mind that it's common to get hundreds of events per 
second, so don't eat too much cpu cycles that could be helpfull for tvtime 
deinterlacer :)

-- 
Christophe Thommeret