Subject: Linux implementation (zcip)

From: Brad Hards <[email-masked]>
Date: Wed, 13 Mar 2002 13:22:30 +1100

I've been looking at the zcip implementation, and have a couple of questions, 
a comment, and a request. The questions are about how the IETF draft is 
supposed to be implemented, so this is at least partly on-topic.

These questions are against the zcip-1 code that I recently got off a 
kernel.org mirror. They may not represent the current state of the code

Q1. The zcip code doesn't support multi-homing (aka IP aliasing, having more 
than one virtual interface (including IP) on a single physical network device 
yet, but I'd like to make it work in the near future. Which of the section 3 
choices (link local on one interface, shared link-local address, unique 
link-local address on all interfaces) is expected?

Q2. I am worried about existing interoperability problems. Is it expected that 
major vendors (especially Microsoft) will release service packs or patches to 
ensure conformance? Or is it worth adding a non-default option to defend more 
agressively?

C1. For people who tried running zcip-1, and had the "infinite fast loop" 
problem, where zcip seemed to find immediate conflicts on every address, you 
need to configure your kernel to support packet filtering (CONFIG_FILTER) in 
the networking options area. Then rebuild. Vendor kernels seem to have this 
turned on, and Linus kernels have it turned off.

R1. Could the author of zcip get in contact with me? I have a patch adding 
documentation and some minor code changes that I'd like to get incorporated.

Brad Hards

---

From: Sebastian Kuzminsky <[email-masked]>
Date: Tue, 12 Mar 2002 18:37:44 -0800

Brad Hards <[email-masked]> wrote:
] These questions are against the zcip-1 code that I recently got off a 
] kernel.org mirror. They may not represent the current state of the code

Hi, i'm the author of zcip.  Sorry there's no contact info in the
zcip tarball, i'm still waiting for the mailing list to be set up on
kernel.org.  Version 1 is the current top of tree.

] Q1. The zcip code doesn't support multi-homing (aka IP aliasing, having more 
] than one virtual interface (including IP) on a single physical network device 
] yet, but I'd like to make it work in the near future. Which of the section 3 
] choices (link local on one interface, shared link-local address, unique 
] link-local address on all interfaces) is expected?

I think "multi-homed" is used in the draft to mean a host with multiple
physical network interfaces, not a host with multiple IP addresses on
a single physical interface.  See figures 1 and 2.

] Q2. I am worried about existing interoperability problems. Is it expected that 
] major vendors (especially Microsoft) will release service packs or patches to 
] ensure conformance? Or is it worth adding a non-default option to defend more 
] agressively?

I dont know what Microsoft's plans are.

I assume you're talking about the W2K/WXP aggressive claim behavior?
It would probably make sense to observe a pair of W2K/WXP hosts collide
and see how they defend the claim, then add a flag to mimic that behavior.

If someone sends me this information i'll add the "defend from WXP"
flag to zcip.

] C1. For people who tried running zcip-1, and had the "infinite fast loop" 
] problem, where zcip seemed to find immediate conflicts on every address, you 
] need to configure your kernel to support packet filtering (CONFIG_FILTER) in 
] the networking options area. Then rebuild. Vendor kernels seem to have this 
] turned on, and Linus kernels have it turned off.

Cool, that's what going on.  I'll add a check for this kernel feature
and print an informative error message if it's missing.

] R1. Could the author of zcip get in contact with me? I have a patch adding 
] documentation and some minor code changes that I'd like to get incorporated.

I'd be pleased to receive your patches.

Sebastian

---

From: Brad Hards <[email-masked]>
Date: Wed, 13 Mar 2002 14:15:51 +1100

> Brad Hards <[email-masked]> wrote:
<snip>
> ] Q1. The zcip code doesn't support multi-homing (aka IP aliasing, having
> more ] than one virtual interface (including IP) on a single physical
> network device ] yet, but I'd like to make it work in the near future.
> Which of the section 3 ] choices (link local on one interface, shared
> link-local address, unique ] link-local address on all interfaces) is
> expected?
>
Mea culpa :-(. Ignore the multi-home reference, and go with the "having
more than one virtual interface (including IP) on a single physical
network device" description. 

<snip>
> and see how they defend the claim, then add a flag to mimic that behavior.
I only know of it from your README, but am philosphically opposed to having 
anyone beat up on my Linux box :-)
<snip>

Patch provided off-list.

Thanks for the fast response!

Brad