segfault when adding OSPF virtual link on Bird 1.6.4

[Cybertinus]

Hello Ondrej,

I think I found the root cause of the messages on my console/log: I 
think I managed to run bird twice from the same config at the same time. 
This would cause horrible things to happen. When I killed Bird on all my 
routers (VMs) and started everything in an orderly manner, the messages 
were gone.

I had an error in my config, which prevented the virtual link to start, 
but when I fixed that (I had defined all the connections between three 
routers in area 1 as pointopoint links, which doesn't work off course) 
the virtual link came up and everything works now, as can be seen in the 
output I've attached to this e-mail in the file bird_output.txt

To be absolutely clear: thanks for the patch, this fixes the original 
segfault issue.

Kind regards,
Cybertinus

On 2018-12-10 21:17, Cybertinus wrote:
> Hello Ondrej,
> 
> Thanks for the quick response and patch! I just applied it on a stock
> 1.6.4 source, compiled it on my CentOS 7.6 testmachines (with
> ./configure --prefix=/ --enable-debug; make; make install) and loaded
> my config with it.
> My console/logfile is now being flooded with messages like:
> bird: ospf1: Bad DBDES packet from nbr 2.2.2.2 on enp0s8 - MS-bit 
> mismatch (7)
> bird: ospf1: Bad DBDES packet from nbr 2.2.2.2 on enp0s8 - DD sequence
> number mismatch (4281812757)
> bird: ospf1: Bad DBDES packet from nbr 2.2.2.2 on enp0s8 - DD sequence
> number mismatch (4177508748)
> bird: ospf1: Bad DBDES packet from nbr 2.2.2.2 on enp0s8 - MS-bit 
> mismatch (7)
> bird: ospf1: Bad DBDES packet from nbr 2.2.2.2 on enp0s8 - too late
> for DD exchange (7)
> 
> But I suspect that this is because I have something wrong in my Bird
> config (it is a test network for a reason off course ;) ).
> 
> Will this patch be included in a 1.6.5 release? And do you know when
> such a version will be available?
> Does 2.0.x have the same problem and can this patch fix the issue there 
> too?
> 
> Kind regards,
> Cybertinus
> 
> On 2018-12-10 02:04, Ondrej Zajicek wrote:
>> On Sat, Dec 08, 2018 at 09:48:52PM +0100, Cybertinus wrote:
>>> Hello everybody,
>>> 
>>> Today I was experimenting with a Bird setup. All the Bird machines 
>>> are
>>> CentOS 7.6 VMs running in Virtualbox on my laptop. When I add an OSPF
>>> virtual link to hook up two area 0's together I get a segfault of 
>>> Bird 1.6.4
>>> itself. All the links between the VMs are defined as "Internal 
>>> Network"
>>> links. Each connection between routers got it's own internal network, 
>>> so
>>> there should be no overlap between those connections.
>> 
>> Hello
>> 
>> Thanks for the thorough bugreport, the attached patch should fix the 
>> issue.
>> 
>>> Steps to reproduce:
>>> 1. Create a bird.conf with the following contents specified in the 
>>> attached
>>> bird.conf
>>> 2. Start Bird
>>> 3. Add the following line to the area 1 config:
>>>        virtual link 2.2.2.2;
>>> 4. Run `birdc configure`
>>> 5. Observe the following error in your syslog:
>>> Dec  8 21:01:35 r3 kernel: bird[3469]: segfault at 32 ip 
>>> 0000000000429fe0 sp
>>> 00007fff599d3350 error 4 in bird[400000+73
>> 
>> Technically it would crash during reconfiguration when vlink is 
>> already
>> defined, even if the reconfiguration changes nothing.
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