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Re: ioctl SIOCGARP failed! errno: 6

From	Jorgen Grahn <grahn+nntp@snipabacken.se>
Newsgroups	comp.os.linux.development.system
Subject	Re: ioctl SIOCGARP failed! errno: 6
Date	2018-06-10 06:05 +0000
Message-ID	<slrnphpfu7.31ka.grahn+nntp@frailea.sa.invalid> (permalink)
References	<5341a907-dabd-43e6-bdb8-2725edb893ad@googlegroups.com> <slrnphln20.31ka.grahn+nntp@frailea.sa.invalid> <004f2c98-fe4c-480f-8f04-497112b8c835@googlegroups.com> <slrnphn055.31ka.grahn+nntp@frailea.sa.invalid> <1c8732ce-f5b0-47e3-8475-e32522cd7a6d@googlegroups.com>

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On Sun, 2018-06-10, Ohm Trivedi wrote:
> On Saturday, June 9, 2018 at 3:24:25 AM UTC-4, Jorgen Grahn wrote:
...
>> BTW (and this should have occurred to me much earlier) it's odd that
>> ARP comes into the picture.  ARP can only reach hosts on a local,
>> switched network, unlike IP which can reach all of the Internet.
>
> The tool in question creates IP packets to send to a target. So in
> the process of creating IP packet, it uses ARP for getting the MAC
> address. That's my understanding so far.

I suppose it's like this:

- You can use the mechanisms in raw(7) to send an IP message, but there are
  limits to how mmuch you can manipulate the header.

- Alternatively, you can send raw link-layer frames using pcap_inject()
  or something.  Then, if it's Ethernet, you have to:
  - know the relevant next-hop's MAC.  Might be the destination's MAC,
    but only if it's on the same network as you.
  - know your interface and its MAC

/Jorgen

-- 
  // Jorgen Grahn <grahn@  Oo  o.   .     .
\X/     snipabacken.se>   O  o   .

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Thread

ioctl SIOCGARP failed! errno: 6 Ohm Trivedi <ohmtrivedi@gmail.com> - 2018-06-08 10:24 -0700
  Re: ioctl SIOCGARP failed! errno: 6 Rainer Weikusat <rweikusat@talktalk.net> - 2018-06-08 20:32 +0100
  Re: ioctl SIOCGARP failed! errno: 6 Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-06-08 19:42 +0000
    Re: ioctl SIOCGARP failed! errno: 6 Ohm Trivedi <ohmtrivedi@gmail.com> - 2018-06-08 13:48 -0700
      Re: ioctl SIOCGARP failed! errno: 6 Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-06-09 07:24 +0000
        Re: ioctl SIOCGARP failed! errno: 6 Ohm Trivedi <ohmtrivedi@gmail.com> - 2018-06-09 18:53 -0700
          Re: ioctl SIOCGARP failed! errno: 6 Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-06-10 06:05 +0000
          Re: ioctl SIOCGARP failed! errno: 6 Rainer Weikusat <rweikusat@talktalk.net> - 2018-06-10 17:54 +0100
  Re: ioctl SIOCGARP failed! errno: 6 Ohm Trivedi <ohmtrivedi@gmail.com> - 2018-06-08 13:45 -0700
    Re: ioctl SIOCGARP failed! errno: 6 Rainer Weikusat <rweikusat@talktalk.net> - 2018-06-08 22:24 +0100

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