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Wireshark-dev: Re: [Wireshark-dev] [Wireshark-users] tshark or dumpcap ring buffer limitations

From: Jeff Morriss <jeff.morriss.ws@xxxxxxxxx>
Date: Thu, 20 May 2010 12:05:09 -0400

[Redirecting to -dev for this question.]

Jaap Keuter wrote:
On 05/19/2010 07:38 PM, Joseph Laibach wrote:
All,

I�m running a continuous capture of data. I�m trying to use a ring
buffer of 25000 files with an 8mb file size. The problem is that the
ring buffer starts overwriting after 10000 files. I�ve tried it with
dumpcap and tshark. The command is using the �b files:25000 �b
filesize:8192. Is there a limitation to the size of the ring buffer for
dumpcap and/or tshark?

[...]

That's a fixed limit:

jaap@host:~/src/wireshark/trunk$ grep RINGBUFFER_MAX_NUM_FILES *.h
ringbuffer.h:#define RINGBUFFER_MAX_NUM_FILES 10000

Hmmm, actually, it's not: if you specify a value of 0 you get "unlimited" files. (I just tried it and killed dumpcap after it created 26,492 files.)

Why have an "upper limit" at all if we also allow unlimited files?

This appeared in rev 7912 and it appears that the max # of files limit was there originally because *ethereal kept the old files open so we would (prior to that commit) run out of fds.

Any reason not to just take this constant out and let users specify any number?