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Re: Have I misunderstood an ipchains concept?

Quoting Noah L. Meyerhans (frodo@morgul.net):
> On Thu, 21 Sep 2000, Christian Pernegger wrote:
> > > What they are saying is that a machine *should* never recieve a packet that
> > > has originated from outside the machine, yet claims (by way of the source
> > > IP) to have originated from that machine?
> > 
> > Exactly. A packet arriving on an eth interface comes from outside.
> > I always thought that a packet destined to the host itself would
> > arrive on the loopback interface, no matter what.
> Volume 1 of Rich Stevens' TCP/IP Illustrated indicates that your thinking
> is correct.  It's in section 2.7, where the book discusses the loopback
> interface.  I'll quote from the book for bit here:
> ___
> Datagrams sent to a broadcast address or a multicast addresss are copied
> to the loopback interface and sent out on the Ethernet.  This is because
> the definition of broadcasting and multicasting includes the sending host.
> - ---
> So, were we to take the Stevens book as gospel, then it seems like Linux
> is doing something wrong here.

Surely a bit early to say that. If this is a fault in the Linux kernel
(which one, by the way?), it ought to be replicatable on other systems.
The original posting had "eth?". What are these cards connected to?

It should be relatively easy to make a packet broadcast from a host
arrive back at that host. For example, a mis-configured router, a
missing termination, ...


Email:  d.wright@open.ac.uk   Tel: +44 1908 653 739  Fax: +44 1908 655 151
Snail:  David Wright, Earth Science Dept., Milton Keynes, England, MK7 6AA
Disclaimer:   These addresses are only for reaching me, and do not signify
official stationery. Views expressed here are either my own or plagiarised.

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