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

From: Stephan von Krawczynski (skraw_at_ithnet.com)
Date: 08/19/03

  • Next message: CaT: "Re: [PATCH 6/10] 2.6.0-t3: struct C99 initialiser conversion" 
    Date:	Tue, 19 Aug 2003 18:52:19 +0200
To: "David S. Miller" <davem@redhat.com>

    On Tue, 19 Aug 2003 08:57:17 -0700
    "David S. Miller" <davem@redhat.com> wrote:

    > On Tue, 19 Aug 2003 17:07:51 +0200
    > Stephan von Krawczynski <skraw@ithnet.com> wrote:
    >
    > > Hm, what rule is broken by the remote host, then?
    >
    > It means that systems (like Linux) that make IP addresses owned by the
    > host instead of specific interfaces cannot correctly interoperate with
    > such remote systems.
    >
    > It is also the case that a host cannot possibly be aware of all
    > subnets present on a given LAN, therefore is should be liberal in it's
    > replies to ARP requests.
    >
    > Finally, it violates the most basic rule of IP networking:
    >
    > "Be liberal in what you accept, and conservative in what you send"
    > -Jon Postel

    If I understood what Richard said in this thread Jon just shot you down. The
    conservative way to _request_ arp would definitely be to request it from the
    "correct" subnet, because as a sender you ought to give credit to knowing that
    "bad" boxes out there won't answer if you do otherwise. There can be no doubt
    what "conservative" means here.
    Additionally, the remote box is not really bad behaving:

    <quote RFC-985>
       A.3. ARP datagram

          An ARP reply is discarded if the destination IP address does not
          match the local host address. An ARP request is discarded if the
          source IP address is not in the same subnet. It is desirable that
          this test be overridden by a configuration parameter, in order to
          support the infrequent cases where more than one subnet may
          coexist on the same cable (see RFC-925 for examples).

    </quote>

    This means the remote box is completely ok if not answering to a request with
    source ip from another subnet.
    So from what I read here requesting arp should really only happen with a source
    ip from the same subnet.

    Regards,
    Stephan
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  • Next message: CaT: "Re: [PATCH 6/10] 2.6.0-t3: struct C99 initialiser conversion"

    Relevant Pages

    • Re: ARP request retransmitting
      ... >> requests except those made by the local host? ... > Just a random search for smart arp large, ... ARP broadcasts are flooded to all ports on a switch. ... Negative response to an ARP request ...
      (freebsd-arch)
    • Re: Cache coherency issues using AllocateCommonBuffer(..)
      ... we did put a scope on the remote system looked at the TLPs coming ... and so it seems like we are stuck with AllocateCommonBuffer. ... standard non-common buffer based DMA APIs. ... How soon do you read from the host memory after you believe the DMA ...
      (microsoft.public.development.device.drivers)
    • Re: Error messages for remote desktop connection attempt
      ... Did you enable Remote Desktop connections on the XP Pro host? ... have you checked the EventLog on the host? ... "The net logon service on the local computer started and then ...
      (microsoft.public.windows.terminal_services)
    • RE: How to access the current EventSource through Remoting
      ... my remote application) to check if the tracing is enabled ... Maybe I could pass a parameter from the client ... >The name of the request event source (i.e. ...
      (microsoft.public.vsnet.enterprise.tools)
    • Question about RSA1 vs DSA fingerprint
      ... I'm connecting to a solaris 8 box on a university LAN, ... This is the "remote" host. ... cygwin, via Sympatico ADSL, ssh version ...
      (comp.security.ssh)