Re: How does dumpcap.c communicate linktype when pushing packets into the rest of Wireshark?

[Guy Harris <guy () alum mit edu>]

On May 10, 2012, at 6:49 PM, Richard Sharpe wrote:

> If I forcibly set the linktype to 1 when reading the first header (the
> SHB) during pcap_live_open, then things work as I expect.

1 is LINKTYPE_ETHERNET.  Does it still work if you forcibly set the linktype to 1 and send down the pipe a capture 
where the first interface *isn't* supplying Ethernet headers?

(And, as per my mail, what happens if you send down the pipe a capture where the first interface supplies 802.11 
headers and the second interface supplies USB headers, for example?  In that case, there *is* no linktype, there's more 
than one linktype.)

> Now to figure out the communication between dumpcap and Wireshark et al.

Note that, as per my mail, dumpcap communicates the link-layer type in the pcap file header's "linktype" field if it's 
writing a pcap file and communicates the link-layer types (plural!) in the pcap-ng file's IDBs if it's writing a 
pcap-ng file; Wireshark just incrementally reads the capture file.

The messages from dumpcap to Wireshark on the sync pipe just say things such as "there are N more packets to read from 
the capture file" or "I've stopped writing to that capture file and am now writing to a capture file with this 
pathname"; they do not say "this capture has link-layer header type XXX", or even "this capture has a new interface 
with link-layer header type XXX" (given that "this capture has link-layer type XXX" is insufficient to fully support 
capturing on multiple interfaces, which 1.7.x supports).
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