Groups > comp.os.linux.development.system > #782

Re: ioctl SIOCGARP failed! errno: 6

From	Rainer Weikusat <rweikusat@talktalk.net>
Newsgroups	comp.os.linux.development.system
Subject	Re: ioctl SIOCGARP failed! errno: 6
Date	2018-06-10 17:54 +0100
Message-ID	<877en67fb6.fsf@doppelsaurus.mobileactivedefense.com> (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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Ohm Trivedi <ohmtrivedi@gmail.com> writes:
> 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.

The bozo who wrote this presumably read somewhere that "ARP queries"
would be used to determine the MAC address associated with an IP
address. He then apparently 'concluded' that this would be the same as
querying the neighbour cache in the kernel for entries (the purpose of
the SIOCGARP ioctl).

There is no such thing as "an IP packet". That's called a datagram. As
IP is a protocol for internetworking, IP datagrams don't include any
link-layer headers, hence, link-layer addresses are not used when
constructing IP datagrams.

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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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