On Tue, Jan 26, 2016 at 4:46 AM, Guy Harris <g...@alum.mit.edu> wrote:
> On Jan 24, 2016, at 7:47 PM, Yang Luo <hslu...@gmail.com> wrote: > > > My ubuntu 14.04 shows the lines below, so I think it doesn't support > IFF_LOOPBACK. > > root@ly-controller:~# ifconfig lo > > lo Link encap:Local Loopback > > > > inet addr:127.0.0.1 Mask:255.0.0.0 > > inet6 addr: ::1/128 Scope:Host > > UP LOOPBACK RUNNING MTU:65536 Metric:1 > ^^^^^^^^^ > > RX packets:10580846 errors:0 dropped:0 overruns:0 frame:0 > > TX packets:10580846 errors:0 dropped:0 overruns:0 carrier:0 > > collisions:0 txqueuelen:0 > > RX bytes:2877631654 (2.8 GB) TX bytes:2877631654 (2.8 GB) > > No, it *does* support it. > > > However Windows supports it. > > Yes, there's an IFF_LOOPBACK flag in Winsock: > > > https://msdn.microsoft.com/en-us/library/windows/desktop/ms738568(v=vs.85).aspx > > But is it actually set for any interface, or is it just provided for > source compatibility with various UN*Xes? I think maybe IFF_LOOPBACK in Windows means the Windows-way loopback, like "Windows Loopback Adapter". So the same definition, not the same meaning with lo. > > > <image.png> > > > > I have analyzed the code related to me. Currently my code is in > inet.c----add_or_find_if. It has curdev->flags and this must be set. What > pcap-win32.c has is pcap_create and pcap_activate_win32, called by > pcap_open_live which is called by add_or_find_if. If I make the change in > pcap-win32.c, the code would be very ugly. > > In the current version of the code on the trunk, which I just checked in, > add_or_find_if() takes PCAP_IF_ flags, rather than IFF_ flags, as arguments. > I saw your commit. add_or_find_if() has been moved to fad-helpers.c and flags is PCAP_IF_ type. > > In pcap_add_if_win32(), check whether the interface is a loopback > interface and, if it is, pass PCAP_IF_LOOPBACK to add_or_find_if(), > otherwise pass 0. > I think calling PacketIsLoopbackAdapter requires the adapter to be opened first (like calling PacketOpenAdapter in pcap_open_live call). But before calling add_or_find_if() the adapter is not ever opened. I don't think it's good to open it twice. Also the function name add_or_find_if() suggests that the "if" can be found if it's already in the list, no opening in this condition. So I don't feel good to open it in another place. The solution: I think I will just move the registry code from packet.dll to libpcap's fad-win32.c's pcap_add_if_win32() as you said, so no need to call PacketIsLoopbackAdapter and no need to open the adapter, and no need to dynamically load PacketIsLoopbackAdapter using LoadLibrary and GetProcAddress APIs. BTW, before I do this, I think I need to have a workable build of libpcap on Windows. > > (There appear to be OIDs that will determine whether the interface is > "working" or not, but 1) they appear to be different in NDIS 5 and NDIS 6 > and 2) they don't separate "up" and "running", so you could only use them > to determine whether to pass PCAP_IF_UP|PCAP_IF_RUNNING, possibly combined > with PCAP_IF_LOOPBACK, or just 0, possibly combined with PCAP_IF_LOOPBACK.) > > > Maybe I should just put my code in inet.c and wrap it with #ifdef WIN32 > macro? > > No - see above. _______________________________________________ tcpdump-workers mailing list tcpdump-workers@lists.tcpdump.org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
