buglwIP - A Lightweight TCP/IP stack - Bugs: bug #47923, on-link prefix cancellation issue

 
 

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bug #47923: on-link prefix cancellation issue

Submitter:  abhishek ambure <abhiambure>
Submitted:  Sat 14 May 2016 06:17:37 PM UTC
   
 
Category:  IPv6 Severity:  3 - Normal
Item Group:  Faulty Behaviour Status:  Fixed
Privacy:  Public Assigned to:  None
Open/Closed:  Closed Planned Release:  None
lwIP version:  1.4.1

Wed 11 Jan 2017 07:27:25 AM UTC, comment #5: 

Fixed by David van Moolenbroek in commit "nd6: improve address autoconfiguration support" (e0c5e1988fd267f216c4cc9c74e7d1be9b50fe61)

Dirk Ziegelmeier <dziegel>
Group administrator
Tue 03 Jan 2017 04:46:25 PM UTC, comment #4: 

Just to make this bug report slightly more accurate.. from comment #2, after (2) "the following changes":

"on-link flag :- set
router lifetime :- 0"

should be..

"autonomous flag :- clear
validation time :- 0"

The L flag was already set. Without clearing the A flag though, the address would also be deprecated (although not removed). Moreover, the "Lifetime" referred to in RFC 4861 Sec. 6.3.4 is the prefix's lifetime, which is the same as the Valid Lifetime (= validation time). Changing the Router Lifetime should and does not have the same effect (Sec. 4.2).

David van Moolenbroek <dcvmoole>
Tue 07 Jun 2016 04:33:06 PM UTC, comment #3: 

This is very similar issue to mine #47923 There is also some reading in RFC 5942.

There must be completely separate entities - address and prefix - Using prefixes for routing and addresses for addressing.

Current implementation uses address for everything causing strange issues.

1) Address must be deleted, because there is no way to just delete the prefix and cause off-link efect. this bug #47923

2) There is no way to have only off-link address. bug #47923

3) There is no way to route according to on-link prefix without address

Jan Breuer <jan_breuer>
Tue 24 May 2016 06:01:53 AM UTC, comment #2: 

i am currently working on this, so patch is not ready now. will send you as it gets ready.

scenario:-
1) we got RA with prefix options as follows and process it for SLAAC
     prefix :- 2001:a8b0::
     prefix length :- 64
     on-link flag:- set
     router life time :- 19000
     validation time :- 2000
     autonomus flag :- set.

   upon this information we had SLAAC, and our ipv6 address will be 2001:a8b0::EUI-64/64 valid for 2000 seconds.

2) but before 19000 seconds router wants to change this prefix to off link it will advertise the same prefix with following changes
    on-link flag :- set
    router lifetime :- 0

on the receipt of (2) message our on-link prefix entry gets removed that is fine, but with that the IPv6 (SLAAC) address also gets removed by putting its state to INVALID.

So this must not happen even though prefix changes state to off-link. SLAAC ipv6 address must be valid up to its validation time and as prefix entry is removed, packets to this prefix destination should go through default router entry.

abhishek ambure <abhiambure>
Mon 23 May 2016 08:43:41 PM UTC, comment #1: 

Here too, I'd be very happy if you could provide a patch to show what you mean :-)

Simon Goldschmidt <goldsimon>
Group administrator
Sat 14 May 2016 06:17:37 PM UTC, original submission:  

according to RFC 4861 section 6.3.4, routers advertises prefix to cancel a previous on-link indication by advertising that prefix with the L-bit set and the Lifetime set to zero. But in LWIP implementation on receipt of such "on-link cancellation" RA, it sets previously configured ipv6 address(SLAAC) to invalid state.

abhishek ambure <abhiambure>

 

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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2017-01-11 dziegel Open/ClosedOpen Closed
    2017-01-11 dziegel StatusNone Fixed

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