RE: [2.4 PATCH] bugfix: ARP respond on all devices

From: Richard Underwood
Date: Wed Aug 20 2003 - 04:08:55 EST


David S. Miller wrote:
>
> Indeed, would people stop quoting from RFC 985 and
> RFC 826.

In case anyone missed it, the following message was posted to
linux-net and netdev. This is currently a draft standard, but anyone
implementing IPv6 should be following it. It clearly states that the the
source address for the equivalent of the ARP request should be the INTERFACE
address.

While it doesn't directly apply to IPv4 (except for David's claim
that IPv4 ARP is based on IPv6 ARP) it does clarify the situation nicely.

I, for one, will be glad when (!) we all migrade to IPv6 and we can
once and all be done with this nonsense, unless Linux plans to deviate from
the standard?

Thanks,

Richard

-----Original Message-----
From: Steven Blake [mailto:slblake@xxxxxxxxxxxxxx]
Sent: 20 August 2003 05:58
To: David S. Miller
Cc: netdev@xxxxxxxxxxx; linux-net@xxxxxxxxxxxxxxx
Subject: Re: [2.4 PATCH] bugfix: ARP respond on all devices


On Tue, 2003-08-19 at 13:53, David S. Miller wrote:

> BTW, this ARP source address algorithm we use comes from
> ipv6, it would be instructive to go and see why they do
> things the way they do.

Are you sure? See below:

========================================================================

RFC 2461 Neighbor Discovery for IPv6 December 1998


4.3. Neighbor Solicitation Message Format

Nodes send Neighbor Solicitations to request the link-layer address
of a target node while also providing their own link-layer address to
the target. Neighbor Solicitations are multicast when the node needs
to resolve an address and unicast when the node seeks to verify the
reachability of a neighbor.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Target Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-

IP Fields:

Source Address
Either an address assigned to the interface from
which this message is sent or (if Duplicate Address
Detection is in progress [ADDRCONF]) the
unspecified address.

Destination Address
Either the solicited-node multicast address
corresponding to the target address, or the target
address.

Hop Limit 255

Authentication Header
If a Security Association for the IP Authentication
Header exists between the sender and the
destination address, then the sender SHOULD include
this header.





Narten, et. al. Standards Track [Page 21]

========================================================================


Regards,

// Steve
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