Ulf Lamping wrote:
> However, if noone is going to solve the current situation, tshark will 
> keep the limitations that it currently has - I don't plan to spend any 
> more effort on this topic ... if someone is seriously going to improve 
> the current situation, I'm really willing to explain devel things, but 
> not on the current level of discussion.

Of course; that's fair enough! I didn't mean to imply by anything I said 
that you should be responsible for any more work here - as I said, I 
think the work you've already done is excellent. I only wanted to 
understand if you thought there were intractable issues here.

> WHY NOT SIMPLY USE A PIPE BETWEEN DUMPCAP AND TSHARK?
> 
> Because it just won't work.
> 
> Sending everything through a pipe is not a portability issue, but has a 
> different problem: pipes are pretty limited in the amount of bytes they 
> can store. If there's a network burst coming in and dumpcap pushes the 
> packets into the pipe very fast, the receiving side of the pipe probably 
> can't process the packets in the required very, very short time (which 
> is *very* likely), packet loss is the result.

Yup; fair enough. A temporary file, with a ringbuffer for long-running 
captures, is a good solution.

> WHY IS STDOUT NOT POSSIBLE?
> 
> Well, it's possible but just not implemented.
> 
> The current implementation simply passes the filename from tshark to 
> dumpcap, which then will mess up it's own stdout with the event messages 
> and packet data.

Yeah - the problem here is that of tshark passing the filename straight 
down: thus breaking both read filters and writing to stdout.

> It's no vodoo magic to make it work again, but someone (but not me) has 
> to made the changes.

Sure. I'll have a look at this in the next week or so if someone else 
doesn't beat me to it.

> BUT READ FILTERS SHOULDN'T BE A PROBLEM?
> 
> Not in the sense of a read filter - as before. The read filter "deletes" 
> the packets before they are written to disk. As dumpcap doesn't know 
> about read filters it will write all packets to disk, so this feature is 
> "gone forever".

Yup: it's fair that they are "gone forever" from dumpcap, but not so 
much that they are gone from tshark.

> However, if someone implements stdout for tshark (as mentioned above), 
> there is a workaround for this. For capturing, you'll use ringbuffer 
> files to keep the size of files to a reasonable size. Now you can use 
> tshark read filters (as before) to "stdout" only the packets you're 
> interested in.

Agreed.

> Again, I'm not a tshark expert. To be honest, I'm tired to support stuff 
> that I'm not interested in. So if you want to see any improvements here, 
> you might need to do it yourself ...

Basically, I think this is an important enough feature that it shouldn't 
be thrown away. I /hope/ to have the time to update it myself...

Cheers

Rich
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