[tcpdump-workers] Handling "-x" and "-xx" if the "link-layer header type" includes metadata
guy at alum.mit.edu
Fri Apr 3 19:45:35 EDT 2015
Somebody got confused by tcpdump on OS X Yosemite defaulting to capturing on all devices simultaneously, meaning that it got PKTAP metadata headers:
and asked about this on SuperUser because the "tcpdump -x" and "tcpdump -xx" output wasn't what they expected, as they weren't getting Ethernet headers:
I think a case can be made that "tcpdump -x" should skip both metadata headers and link-layer headers; I don't see any issues with doing that.
A case can also be made that "tcpdump -xx" should at least skip metadata headers, although there *might* be scripts, for example, that expect to see radiotap headers dumped in hex with "tcpdump -xx", for example.
My inclination would be to have:
-x mean "skip metadata and link-layer headers";
-xx mean "skip metadata headers";
-xxx mean "dump the entire payload, skipping nothing.
Does that seem reasonable?
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