IPv6 prefix length error

[Mark Andrews]

In message <F80B214C2304C641B917B47051D743C407F0297A23 at HQ-MB-08.ba.ad.ssa.gov>,
 "Khuu, Linh Contractor" writes:
> Thanks Mark for your recommendation!!!
> 
> However, in the ifconfig -a output, I have:
> 
> lo0: flags=3De08084b<UP,BROADCAST,LOOPBACK,RUNNING,SIMPLEX,MULTICAST,GROUPR=
> T,64BIT>
>         inet 127.0.0.1 netmask 0xff000000 broadcast 127.255.255.255
>         inet6 ::1/128
> 
> But I still see the error in the log "28-Apr-2011 23:58:02.935 general: pre=
> fix length for ::1 is unknown (assume 128)"
> 
> As for the prefix length of the IPv6 address of the interface, we have 2001=
> :1930:e03::e/48, but the log still show the error of (assume 128).
> 
> Will this error cause any problem with named to resolve IPv6 addresses?
> 
> Linh Khuu
> Network Security Specialist
> MicroTech ESS Contract
> Office: 410-966-0798
> Pager: 410-232-2350
> Email: Linh.Khuu at ssa.gov

Please go talk to your OS vendor.  There are 1/2 a dozen different
way OS vendors do this and most of them are very poorly documented.
There is sysctl(), ioctl() 2 or 3 variants, getifaddrs() and
/proc/net/if_inet6.  Every OS vendor seemed to invent their own
method which is a pain for anyone trying to write portable code.

The fix is likely to be a couple of lines of code to retrieve the
value but without access to the correct documentation or kernel
source code its hard to work out how to fix it.

Mark
 
> -----Original Message-----
> From: Mark Andrews [mailto:marka at isc.org]=20
> Sent: Thursday, April 28, 2011 7:53 PM
> To: Khuu, Linh Contractor
> Cc: 'bind-users at lists.isc.org'
> Subject: Re: IPv6 prefix length error
> 
> 
> In message <F80B214C2304C641B917B47051D743C407F0297937 at HQ-MB-08.ba.ad.ssa.g=
> ov>,
>  "Khuu, Linh Contractor" writes:
> > Hello,
> >=20
> > We just added the IPv6 address on our DNS servers. When we started named,=
>  w=3D
> > e see these errors in the log:
> >=20
> > prefix length for 2001:1930:e03::e is unknown (assume 128)
> > prefix length for ::1 is unknown (assume 128)
> >=20
> > So far, named is still running fine... I can't find any information to co=
> rr=3D
> > ect these errors.
> >=20
> > Thanks,
> > Linh Khuu
> 
> These are reported because named was unable to determine the prefix
> length associated with the address.  Usually because no one has
> documented the OS specicif method for doing this or it is write
> only.
> 
> Please contact your OS vendor so they can address the issue.
> 
> The major implication of not having this information is that the builtin
> "localnets" acl will not be complete.  Instead of 2001:1930:e03::/64,
> assuming it is a /64, it will have 2001:1930:e03::e/128.
> 
> Mark
> --=20
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org