Wireshark · Wireshark-dev: Re: [Wireshark-dev] Adding pcap-ng pipe support to dumpcap

[Guy Harris <guy@xxxxxxxxxxxx>]

On Aug 31, 2017, at 3:37 AM, Ed Beroset <beroset@xxxxxxxxxxxxxx> wrote:

> On 08/30/2017 09:31 PM, Guy Harris wrote:
>> On Aug 30, 2017, at 6:00 PM, Ed Beroset <beroset@xxxxxxxxxxxxxx> wrote:
>>> One problem is that as dumpcap is currently written, it treats files and pipes very differently.
>> *Files* and pipes, or *capture devices* and pipes?
> 
> Actually, I meant to say pipes and sockets.

That's because

	1) UN*Xes tend to support select()/poll()/epoll()/kqueues/etc. on just about all descriptors

while

	2) Windows doesn't support the WaitFor APIs on all handles, and pipes are different from sockets.

>>> but I can't help but think that the general approach you describe is the better long term strategy.
>> Probably.  It means that the interface between *shark and extcap programs would be different - but, while having extcap programs behave like dumpcap might complicate the extcap programs (although some of the code to do that could be in a library used by dumpcap and by extcap programs), it might simplify the Wireshark capture code path.
> 
> I'm not sure that the interface between dumpcap and Wireshark/tshark would need to change to accommodate a wider variety of inputs via pipes.

It wouldn't.

The interface between *extcap programs* and Wireshark/tshark would need to change if we want to have extcap programs work like dumpcap, so that they talk directly to Wireshark/tshark, and write directly to a capture file, rather than talking to dumpcap by sending packets over a pipe.  That was Stephen's suggestion, and I think it's worth considering.