This question has probably been asked before, so I thought I'd at least put a 
Tennyson twist on it.

I started getting more serious about converting dissectors to the "new style".  
I submitted a bunch of patches where it was obvious that the dissectors fell 
into the "give me everything" category.  My biggest worry is the comment made 
by Guy in bug 11134 
(https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=11134#c13), that some 
dissectors want to "accept" a tvb (packet) as their own, but don't actually 
parse any bytes (so it appears that they would "return 0" with the new style).  
So the remaining ones I'm taking more slowly (with the attitude of unsure means 
leave as old style) and if anyone know of protocols that behave this way, feel 
free to convert them (or send me a note)

The case I keep coming across that I'm not sure how to deal with is dissectors 
that get a few bytes in (and have already created trees/items for a few 
fields), and then decide they aren't going to dissect anymore because of a 
"bad" field value (most commonly "version" or "length").  Should we apply a 
consistent rule for this?  Like if you're not going to dissect "versions" you 
don't support, check before making trees and just not bother with expert info 
saying "version isn't supported" while ceasing dissection.  Or dissect as 
"latest version" (or at least "a" version), but with the expert info applied 
that the version is unknown.  I'm not sure which scenario users would 
appreciate more, but I'd like to see it applied as consistently as possible. I 
believe my preference is for using expert info, but continuing dissection.
Are such rules more critical for popular protocols like Ethernet, IP and 
TCP/UDP where there are possibly "shared" values for a subdissector identifier?

Also, should we clean up a tree if a new-style dissector returns 0 (within the 
functions in epan/packet.c)?  I think the expert info would be harder to clean 
up, but I'm also not sure of the difficult of the trees either.

Opinions welcome, but I'd like to see the "new" style be the "only" style by 
the 2.2 release.
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