BIRD - iBGP between RS over IPv6 lead to crash (segfault)

[Javor Kliachev]

Hello Ondrej, 

Many thanks for the advise. 

We have upgraded BIRD to the latest 1.6.8 version. 
In this version seems the crash issue is resolved but the second issue with 
- iBGP between RS-RS over IPv6 still exists. This BGP session is not able to establish yet. 

In my LAB I have successfully replicated the issue. Both Route Servers are on BIRD with latest version 1.6.8. They have the following IPv6 addresses configured: 

RS1 IPv6 - 2001:67c:29f0::A:1:234:4 
RS2 IPv6 - 2001:67c:29f0::A:1:234:5 

Here is the config fo each RS 

RS1 output: 
# birdc6 show proto 
BIRD 1.6.8 ready. 
name proto table state since info 
device1 Device master up 2021-07-20 10:50:21 
P1234 Pipe master up 2021-07-20 10:50:21 => T1234 
R1234x5 BGP T1234 start 2021-07-20 10:58:33 Connect 
direct1 Direct master down 2021-07-20 11:09:51 
kernel1 Kernel master down 2021-07-20 11:09:51 

# cat AS1234 
table T1234 

protocol pipe P1234 from iBGP_PIPES { 
description "RS"; 
peer table T1234; 
export all; 
} 

protocol bgp R1234x5 { 
description "iBGP_RS2"; 
source address 2001:67c:29f0::A:1:234:4; 
neighbor 2001:67c:29f0::A:1:234:5 as 1234; 
local as myas; 
prefer older on; 
missing lladdr ignore; 
import none; 
export none; 
passive off; 
table T1234; 
# add paths on; 
# direct; 
} 

=============================================================================== 

RS2 output: 
# birdc6 show proto 
BIRD 1.6.8 ready. 
name proto table state since info 
device1 Device master up 2021-07-20 10:52:23 
P1234 Pipe master up 2021-07-20 10:52:23 => T1234 
R1234x4 BGP T1234 start 2021-07-20 10:58:46 Connect 
direct1 Direct master down 2021-07-20 11:09:21 
kernel1 Kernel master down 2021-07-20 11:09:21 

# cat AS1234 
table T1234 

protocol pipe P1234 from iBGP_PIPES { 
description "RS"; 
peer table T1234; 
export all; 
} 

protocol bgp R1234x4 { 
description "iBGP_RS1"; 
source address 2001:67c:29f0::A:1:234:5; 
neighbor 2001:67c:29f0::A:1:234:4 as 1234; 
local as myas; 
prefer older on; 
missing lladdr ignore; 
import none; 
export none; 
passive off; 
table T1234; 
# add paths on; 
# direct; 
} 

Seems the issue happens when remote peer is also BIRD. When remote peer is router ( Cisco, Juniper, Quagga etc... ) the session is successfully established. 
On IPv4 iBGP between both RS works fine. So the issue related only with IPv6 stack. 

I appreciate any kind of help. 

Best~ 


Javor Kliachev 
Senior Engineer IP Services 
office: +359 2 974 33 11 
mobile: +359 885 98 84 95 
[ http://www.neterra.net/ | www.neterra.net ] [ https://bg.linkedin.com/pub/javor-kliachev/11/b46/843 | 
                                                                                                      ] 


From: "Ondrej Zajicek" <santiago at crfreenet.org> 
To: "Javor Kliachev" <jkliachev at neterra.net> 
Cc: "bird-users" <bird-users at network.cz>, "inmt-ip" <inmt-ip at neterra.net> 
Sent: Friday, 9 July, 2021 16:33:20 
Subject: Re: BIRD - iBGP between RS over IPv6 lead to crash (segfault) 

On Fri, Jul 09, 2021 at 11:43:53AM +0300, Javor Kliachev wrote: 


Hello, 

We're using BIRD 1.6.4 as Route Server. 

Recently we have decided to establish an internal BGP session between both RS over IPv6 

But when we added our config in BIRD then it has crashed immediately with the following error: 
[35878512.553496] bird6[2545]: segfault at 0 ip 000055f60242c331 sp 00007ffd43689460 error 4 in bird6[55f60240a000+86000] 
Another more strange: 

Initially before the crash we have added the following config below and RS was stable but session was not able to establish. 
We have made a capture of the traffic during the attempt of session establishment and seems TCP handshake works but then not procced futher. 

... 

Could someone BIRD developer to suggest some solution for fixing this issue? 
We highly appreciate any kind of support. 



Hello 

Well, first upgrade and try latest legacy version (1.6.8). Version 1.6.4 
is too old and not worth to us to check whether it was already fixed or 
not. 

-- 
Elen sila lumenn' omentielvo 

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org) 
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net) 
"To err is human -- to blame it on a computer is even more so." 
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