Re: [PATCH] IPv6: Fix Prefix Length of Link-local Addresses

On Tue, Oct 08, 2002 at 12:05:59AM +0900, YOSHIFUJI Hideaki / ?$B5HF#1QL@?(B wrote:

Hi,

Prefix length for link-local address should be 64, not 10.
This patch fixes prefix length of link-local address.

Following patch is against 2.4.19.

Huh?

Without reading the kernel routing table code a bit more,  I'm not certain
what that change does,  but it looks as if it might be changing the
connected route for a link local from fe80::/10 to fe80::/64.

I'd actually say that is wrong.

All link local's are currently supposed to have those top bits
('tween 10 and 64) zero'd,  however any address within the link local
prefix _is_ on link / connected and should go to the interface.

i.e. it's perfectly valid for me to assign a link local of fe80:1910::10
     to an interface and expect it to be work,  likewise for a packet
     destined to any link local address to trigger ND.

DF

In article [off-list ref] (at Wed, 9 Oct 2002 17:00:18 +0100), Derek Fawcus [off-list ref] says:

All link local's are currently supposed to have those top bits
('tween 10 and 64) zero'd,  however any address within the link local
prefix _is_ on link / connected and should go to the interface.

i.e. it's perfectly valid for me to assign a link local of fe80:1910::10
     to an interface and expect it to be work,  likewise for a packet
     destined to any link local address to trigger ND.

First of all, please don't use such addresses.

By spec, auto-configured link-local address is fe80::/64
and connected route should be /64.

If you do really want to use such addresses (like fe80:1920::10),
you can put another route by yourself, at your own risk.

We should not configure in such way by default.
and, we should even have to add "discard" route for them 
by default for safe.

--yoshfuji

On Thu, 10 Oct 2002, YOSHIFUJI Hideaki / [iso-2022-jp] $B5HF#1QL@(B wrote:

In article [off-list ref] (at Wed, 9 Oct 2002 17:00:18 +0100), Derek Fawcus [off-list ref] says:

quoted

All link local's are currently supposed to have those top bits
('tween 10 and 64) zero'd,  however any address within the link local
prefix _is_ on link / connected and should go to the interface.

i.e. it's perfectly valid for me to assign a link local of fe80:1910::10
     to an interface and expect it to be work,  likewise for a packet
     destined to any link local address to trigger ND.

First of all, please don't use such addresses.

By spec, auto-configured link-local address is fe80::/64
and connected route should be /64.

If you do really want to use such addresses (like fe80:1920::10),
you can put another route by yourself, at your own risk.

We should not configure in such way by default.
and, we should even have to add "discard" route for them 
by default for safe.

Personally I think the interfaces should be configured with a /64 but 
there should be a discard route for the whole /10.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

Hello!

Personally I think the interfaces should be configured with a /64 but 
there should be a discard route for the whole /10.

I agressively agree. :-)

Alexey

In article [off-list ref] (at Wed, 9 Oct 2002 23:03:29 +0400 (MSD)), kuznet@ms2.inr.ac.ru says:

quoted

Personally I think the interfaces should be configured with a /64 but 
there should be a discard route for the whole /10.

I agressively agree. :-)

How about this (against 2.4.19 / 2.4.20-pre10)?

Index: net/ipv6/addrconf.c
===================================================================
RCS file: /cvsroot/usagi/usagi-backport/linux24/net/ipv6/addrconf.c,v
retrieving revision 1.1.1.1.20.1
diff -u -r1.1.1.1.20.1 addrconf.c

--- net/ipv6/addrconf.c	2002/09/27 17:17:06	1.1.1.1.20.1
+++ net/ipv6/addrconf.c	2002/10/09 18:18:34

@@ -783,6 +783,7 @@
 	struct in6_addr addr;
 
 	ipv6_addr_set(&addr,  __constant_htonl(0xFE800000), 0, 0, 0);
+	addrconf_prefix_route(&addr, 10, dev, 0, RTF_ADDRCONF|RTF_REJECT);
 	addrconf_prefix_route(&addr, 64, dev, 0, RTF_ADDRCONF);
 }
 

-- 
Hideaki YOSHIFUJI @ USAGI Project <yoshfuji@linux-ipv6.org>
GPG FP: 9022 65EB 1ECF 3AD1 0BDF  80D8 4807 F894 E062 0EEA

Hello!

How about this (against 2.4.19 / 2.4.20-pre10)?

It can be made global added at ipv6_route_init, I think.

Alexey

At Wed, 9 Oct 2002 17:00:18 +0100,
Derek Fawcus [off-list ref] wrote:

Without reading the kernel routing table code a bit more,  I'm not certain
what that change does,  but it looks as if it might be changing the
connected route for a link local from fe80::/10 to fe80::/64.

Why do you want to use /10 prefix for link-local address ?
RFC2373 defines link-local address format as below.

   |   10     |
   |  bits    |        54 bits          |          64 bits           |
   +----------+-------------------------+----------------------------+
   |1111111010|           0             |       interface ID         |
   +----------+-------------------------+----------------------------+

All link local's are currently supposed to have those top bits
('tween 10 and 64) zero'd,  however any address within the link local
prefix _is_ on link / connected and should go to the interface.

If you wan to use /10 prefix for link-local address, you can add the
link-local address with /10 prefix to interfaces and routing table
manually at your own risk, but it should not  be a default behavior.

-- Yuji Sekiya