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Subject: Re: [OMPI devel] [OMPI svn] svn:open-mpi r17307
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-01-30 09:37:05


Is one possible solution to have Open MPI mark in the packet where the
incoming connection is coming from?

On Jan 30, 2008, at 9:20 AM, Tim Mattox wrote:

> Hello,
>
> On Jan 30, 2008 3:17 AM, Adrian Knoth <adi_at_[hidden]>
> wrote:
> [snip]
>> As mentioned earlier: it's very common to have multiple addresses per
>> interface, and it's the kernel who assigns the source address, so
>> there's nothing one could say about an incoming connection. Only
>> that it
>> could be any of all exported addresses. Any.
>>
>
> This is only partially correct. Yes, by default the Linux kernel will
> fill in the IP header with any of the IP addresses associated with
> the machine, regardless of which NIC the packet will be sent on.
> It was a never ending debate on the Linux Kernel Mailing list as to
> what was the right way to do things... are IP addresses "owned" by
> the machine, or are they "owned" by the NIC? The kernel defaults
> to the former definition (which is contrary to pretty much every
> other OS on the planet... but the relevant RFCs left both
> interpretations
> open). Anyway, there are ways to configure the networking stack of
> the Linux kernel to get the other behavior, so that a packet will be
> guaranteed to have one of the IP addresses associated with the NIC
> that it uses for egress.
> See Documentation/networking/ip-sysctl.txt in your Linux Kernel
> sources
> for a description of these relevant options:
> arp_filter, arp_announce, arp_ignore
> which are accessed on a live system here:
> /proc/sys/net/ipv4/conf/all/
>
> I guess if I put in the time, I could create a FAQ entry about it,
> and what values to use... though I am not familiar with any
> equivalent IPv6 settings (or if any exist).
> --
> Tim Mattox, Ph.D. - http://homepage.mac.com/tmattox/
> tmattox_at_[hidden] || timattox_at_[hidden]
> I'm a bright... http://www.the-brights.net/
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-- 
Jeff Squyres
Cisco Systems