On Tuesday, October 12, 2010, 3:27:09 PM, Jeff Morriss wrote: > I think composite tvbuffs probably do work, but their use is hindered by > the fact that each tvb that you get (each time a frame is handed to your > dissector) is freed/reused after the packet is dissected. That is, > Wireshark does _not_ keep the entire capture file in memory. Because of > that, there's relatively little need/use for the composite functions and > it's why you need to allocate copies of whatever data you want to > reassemble.
This. I was digging into the RTMPT dissector again over the weekend, hoping I could move from allocating memory for every reassembled pdu to just creating composite tvbs overlaying the original packets. This would have been a big win memory-wise, since the reassembled packets have to live for the entire capture session (multiple non-contiguous chunks based on multiple prior TCP segments), but turns out not to be possible for the above reason. So it looks like it's necessary to either tvb_memdup from the original data, then add a tvb_new_real_data to a composite and use that, or se_alloc the entire buffer up front, tvb_memcpy into it and use a tvb_new_real_data from that which has a lower overhead in terms of tvbuff structures. (I have a concern that neither of those will free up the used memory. tvb_memdup uses g_malloc and there is no notification of when this is safe to free so AFAICS it is leaked. The se_alloced blocks will of course be freed once the capture is closed, but what of the extra tvb structures on top of them? I presume they are permanent rather than seasonal so ought to be tvb_freed at some point, but again I can't see any notification of when that should happen, so it doesn't.) John -- ___________________________________________________________________________ Sent via: Wireshark-dev mailing list <wireshark-dev@wireshark.org> Archives: http://www.wireshark.org/lists/wireshark-dev Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev mailto:wireshark-dev-requ...@wireshark.org?subject=unsubscribe
