buglwIP - A Lightweight TCP/IP stack - Bugs: bug #48162, Off-link RA prefix with bit A set...

 
 

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bug #48162: Off-link RA prefix with bit A set is ignored resulting in no address

Submitter:  Jan Breuer <jan_breuer>
Submitted:  Tue 07 Jun 2016 12:10:03 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:  git head

Wed 11 Jan 2017 07:28:06 AM UTC, comment #4: 

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

Dirk Ziegelmeier <dziegel>
Group administrator
Thu 29 Dec 2016 11:30:58 PM UTC, comment #3: 

I'm testing a fix for this (and #47923) at the moment, please stay tuned..

David van Moolenbroek <dcvmoole>
Wed 03 Aug 2016 10:44:41 AM UTC, comment #2: 

please note Verison wireless send RA with A=1 , L=0.
( so a device using LWIP will not have IPv6 address, while a device using Linux will have one)

as a workaround (till this issue resolve) should we ignore the L bit as follows:


$ p4 diff2 src/core/ipv6/nd6.c#2 src/core/ipv6/nd6.c#1
==== src/core/ipv6/nd6.c#2 (text) - src/core/ipv6/nd6.c#1 (text) ==== content

481,483c474,475
<         /* since VZW configure A=1,L=0 . it is better to ignore the L bit
<         if (prefix_opt->flags & ND6_PREFIX_FLAG_ON_LINK) {*/
<         {
---

>
>         if (prefix_opt->flags & ND6_PREFIX_FLAG_ON_LINK) {



Izik goldraich <izikgo>
Tue 07 Jun 2016 04:10:44 PM UTC, comment #1: 

It seems to be much deeper problem. More reading in RFC 5942.

Bit L tells if the prefix is on-link or not. ip6_route should look on prefix_list and not address list to determine, if it can send a packet directly to that interface or not.

Bit A tells that there can be done address autoconfiguration using this prefix but it is completely independent from bit L.

So the interface can have
- address using off-link prefix
- different on-link prefix without address
and this configuration is completely legal.

Sending packet matching on-link prefix must be done directly.
Sending packet matching off-link prefix must be done using router.

LwIP assumes that all Prefix Information Options ar used with both L and A bits set and all other combinations are ignored. This cause two bugs
 - off-link prefixes are not used for addres autoconfiguration
 - on-link prefixes without address are not used for direct communication


---------

Off-link prefix can be used in environment, where you need to isolate all nodes and you need to force all nodes to use router. Every communication is done by the router and it determines whether you are allowed to communicate with another node or not.

Jan Breuer <jan_breuer>
Tue 07 Jun 2016 12:10:03 PM UTC, original submission:  

Device should generate its address for all prefixes with bit A set but it is only done for On-link prefixes. Off-link prefixes are ignored preventing the device to communicate in such networks.

Jan Breuer <jan_breuer>

 

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    Follow 2 latest changes.

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

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