Re: raw ethernet frames to loopback

[食肉大灰兔V5 <hsluoyz () gmail com>]

Hi Anders,

Npcap supports the feature to send and receive loopback packets. The readme
about this feature is here: https://github.com/nmap/npcap (the "For
softwares that use Npcap loopback feature" section).

For short, you should notice this:
1) In the Npcap installer, make sure the "Support loopback traffic ("Npcap
Loopback Adapter" will be created)" option is CHECKED, and "Use DLT_NULL as
the loopback interface' link layer protocol instead of DLT_EN10MB" is
UN-CHECKED. This selection is by default, so you don't need to change a
thing.
2) If you send packets to loopback interface, the src MAC and dst MAC
doesn't matter (can be anything you like). You only need to specify the MAC
type to IPv4 or IPv6.
3) If you receive packets from loopback interface, the received src MAC and
dst MAC is always ALL ZERO.
4) Don't try to send ARP requests or responses to loopback interface, they
will be ignored. And you will NOT receive any ARP packets from loopback
interface.
5) The MTU of the loopback interface is actually 65536 (even some softwares
and Windows told you it's only 1500, they are wrong), so feel free to
encapsulate some large data into it.

Let me know if you have any questions.


Cheers,
Yang



On Sun, Apr 24, 2016 at 12:46 AM, Anders Kallerdahl <anders () kallerdahl se>
wrote:

> To whom it concerns,
>
> i am developing a simulation tool (in c), where i need several
> Applications (processes) on windows 7 to communicate to each other using
> Raw ethernet frames, and using the loopback address (127.0.0.1)
> It is important for the project to use the raw ethernet frames, and not
> UDP or TCP. By raw ethernet frames i mean access to full payload of the
> ethernet frame.
>
> I tried to use the wincap drivers but understand now that it cannot access
> the loopback address.
>
> Can i use the Ncap libraries to send and receive raw ethernet frames via
> loopback (127.0.0.1)?
>
> hope i sent this mail to the right forum.
>
> regards,
> Anders Kallerdahl
>
> _______________________________________________
> Sent through the dev mailing list
> https://nmap.org/mailman/listinfo/dev
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