Re: Enable to send packets on if_loop via bpf

[Gert Doering <gert%greenie.muc.de@localhost>]

Hi,

On Wed, Nov 09, 2022 at 07:21:44AM -0500, Greg Troxel wrote:
> Looking at if_tun.c, I see DLT_NULL.  This should have the same ability
> to write.   I have forgotten the details of how tun encodes AF when
> transmitting, but I know you can have v4 or v6 inside, and tcpdump works
> now. so obviously I must be missing something.

On the user side of if_tun (not bpf), a 2-byte value consisting
of htonl(AF_INET6) / htonl(AF_INET) is prepended before the 
actual packet.

gert
-- 
"If was one thing all people took for granted, was conviction that if you 
 feed honest figures into a computer, honest figures come out. Never doubted 
 it myself till I met a computer with a sense of humor."
                             Robert A. Heinlein, The Moon is a Harsh Mistress

Gert Doering - Munich, Germany                             gert%greenie.muc.de@localhost