Re: Npcap 0.04 call for test

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

On Aug 24, 2015, at 6:08 AM, Yang Luo <hsluoyb () gmail com> wrote:

> I have looked at all occurrences of PCAP_IF_LOOPBACK in Npcap's wpcap.dll code at 
> https://github.com/nmap/npcap/search?utf8=%E2%9C%93&q=PCAP_IF_LOOPBACK, it seems that this property is never 
> effectively used inside wpcap.dll's code.

In fad-win32.c, pcap_add_if_win32() is used by pcap_findalldevs(), and pcap_add_if_win32() calls add_or_find_if() in 
inet.c, and add_or_find_if() uses PCAP_IF_LOOPBACK.

That shows up in the GitHub search done with the URL you specify.

> In Wireshark's WinPcap official trunk, it is totally unused except some prints. See: 
> https://github.com/wireshark/winpcap/search?utf8=%E2%9C%93&q=PCAP_IF_LOOPBACK.

That's because Wireshark's WinPcap official trunk only includes the WinPcap driver, the WinPcap packet.dll DLL, and the 
WinPcap routines that aren't already part of the official libpcap source - fad-win32.c and inet.c are both part of the 
official libpcap source:

        https://github.com/the-tcpdump-group/libpcap/blob/master/fad-win32.c

        https://github.com/the-tcpdump-group/libpcap/blob/master/inet.c

> So currently PCAP_IF_LOOPBACK is never set in any pcap_if_t struct for WinPcap and Npcap.

That should be fixed.

> And It seems to work fine without setting it. Where would Wireshark use this PCAP_IF_LOOPBACK  for?

1) WinPcap *itself* uses it to ensure that loopback interfaces sort after non-loopback interfaces, so that if a machine 
has both "real" and loopback interfaces active, the default interface won't end up being a loopback interface;

2) Wireshark uses it to flag interfaces as being loopback interfaces in some places (see the uses of the "loopback" 
flag in the if_info_t structure).
___________________________________________________________________________
Sent via:    Wireshark-dev mailing list <wireshark-dev () wireshark org>
Archives:    https://www.wireshark.org/lists/wireshark-dev
Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
             mailto:wireshark-dev-request () wireshark org?subject=unsubscribe