On 18 October 2017 at 11:08, Pascal Quantin <[email protected]>
wrote:

>
>
> 2017-10-18 11:54 GMT+02:00 Graham Bloice <[email protected]>:
>
>>
>>
>> On 18 October 2017 at 09:45, Pascal Quantin <[email protected]>
>> wrote:
>>
>>> Hi list,
>>>
>>> when we introduced Npcap support back in 2015/2016, we decided that
>>> WinPcap driver should have higher precedence due to its known stability
>>> (and despite issues with newer Windows versions).  By that time, you could
>>> get a BSoD with Npcap.
>>>
>>> Time has elapsed since, and Npcap is now bundled with Nmap. The number
>>> of commits in Npcap repository (https://github.com/nmap/npcap/) have
>>> also decreased, which hopefully means that the product is more mature (the
>>> list of opened issues can be found here: https://github.com/nmap/nmap/i
>>> ssues?q=is%3Aissue+is%3Aopen+label%3ANpcap).
>>>
>>> Nmap team filled bug 14134 regarding a library loading issue they
>>> spotted. We are gonna fix it, but it raises the question of which capture
>>> driver (between WinPcap and Npcap) should be attempted to be loaded first.
>>> Note that for now I do not want to change the driver bundled with our
>>> Windows installers (the Npcap license restriction must be solved before
>>> even thinking about it). So this only concerns people having installed both
>>> WinPcap and Npap. Moreover, if we agree on the change, I would suggest to
>>> apply it only in development branch.
>>>
>>> Thoughts?
>>>
>>> Regards,
>>> Pascal.
>>>
>>>
>> I'm generally in agreement with all the above, but I'm torn on
>> hard-coding a preference for one capture library over another.  If a system
>> has both, who are we to say which one will be used to the exclusion of the
>> other.
>>
>> I guess I'm implying we should expose a preference to allow the user to
>> choose which is definitely more work but does give control back.
>>
>
> Unfortunately a Wireshark preference is not doable, as wpcap.dll is also
> loaded by dumpcap that does not use our preferences module. A registry key
> might do the trick. Presumably tshark should also have a command flag
> allowing you to configure it.
> I guess the underlying question is: what kind of power users would have
> both Npcap and WinPcap installed? Either it's a personal choice because
> Npcap features are required (and in that case it would make sense to favor
> it), or you have Nmap installed (or any other software that migth rely on
> it). And if it works for Nmap, any reason it would fail for Wireshark?
>
>
Presumably dumpcap could also have a command flag to select which to use.


> Note also that when both are installed but you are uwing WinPcap, you can
> see Npcap loopback interface in the list but if you select it no packets
> are capture at all. A bit confusing.
>

Thinking about my own workflow, when capturing "oddities" occur, and Npcap
is installed, a remedial option is to uninstall it.  Having a switch in
Wireshark would make life easier.

-- 
Graham Bloice
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