Not sure if this is a bug! (btpd 0.16)
Brian Waters
something you guys even consider a bug.
I have an improperly-formatted .torrent file; specifically, the
"announce" key comes last in the top-level dictionary -- if it were
properly formatted, it would come first. (In a bencoded dictionary,
the keys are supposed to be in alphabetical order.) When I try to add
this torrent using bcli, I get an error:
error loading '[path]' (Invalid argument).
Clearly, the problem here is the badly-formatted .torrent file, but
other clients handle it fine, and the .torrent file does contain all
of the information that the daemon needs. If it were me, I would have
btpd accept this kind of bad input, but different projects have
different policies.
If it's better for me to file a real bug report, let me know and I'll
make it reproducible. I haven't looked too closely to see how much
work it would take to fix, but I'd be more than happy to submit a
patch.
Cheers,
- BW
Nemosoft Unv.
On Thursday 27 January 2011 00:26:02 Brian Waters wrote:
> Hi! This is not a full bug report, because I'm not sure if this is
> something you guys even consider a bug.
>
> I have an improperly-formatted .torrent file; specifically, the
> "announce" key comes last in the top-level dictionary -- if it were
> properly formatted, it would come first. (In a bencoded dictionary,
> the keys are supposed to be in alphabetical order.) When I try to add
> this torrent using bcli, I get an error:
>
> error loading '[path]' (Invalid argument).
>
> Clearly, the problem here is the badly-formatted .torrent file, but
> other clients handle it fine, and the .torrent file does contain all
> of the information that the daemon needs.
Indeed, btpd assumes the bencoded file to be in albetical order. In benc.c it
searches through the list of variables and stops if the target variable name
is smaller than the current one (see lines 236 and 237).
I suppose it shaves off a few microseconds of scanning through the list, but I
doubt it really makes that much of an impact.
> If it were me, I would have
> btpd accept this kind of bad input, but different projects have
> different policies.
That depends on two things. You wrote "keys are supposed to be in alpabetical
order", and various documents on the web agree with you. So basically it's a
wrong torrent file, but how strict do you (we) want to be? So far I've never
encountered such a torrent file, so yours seem to be the exception.
On the other hand, I fail to see the added value of storing bencoded keys
alphabetically; if you want to optimize searching throught the list there are
many ways to optimize this in memory (I'm assuming any torrent tool will parse
the file and stores it in some internal structure; sorting or adding a hash is
then a trivial task).
So is it a bug in btpd? No. Is it something we can accomodate easily? Yes. Do
we want to? I'm inclined to say no... In stead, my suggestion would be to
write a small tool or script to fix thoses broken torrents. Or prod the maker
of the torrent and tell him/her to use better tools.
- Nemo
Brian Waters
up with a good patch to change this behavior (only to accept
out-of-order keys, and nothing else), would you guys accept it?
Basically, when I found this out, I thought it would be a fun little
thing to fix, but I don't want to waste my time if it won't be
accepted anyway.
Thanks,
Brian Waters