<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<p><font face="Gentium">Hello!</font></p>
<p><font face="Gentium">We'll try to reproduce it locally (which
should be trivial) and fix this corner case. If any additional
information is needed, we'll follow up.<br>
</font></p>
<p><font face="Gentium">Thank you for your report.<br>
Maria<br>
</font></p>
<p></p>
<div class="moz-cite-prefix">On 6/22/23 14:52, Kobayashi_Bairuo via
Bird-users wrote:<br>
</div>
<blockquote type="cite"
cite="mid:005301d9a508$6ea2ba60$4be82f20$@tohunet.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="Generator" content="Microsoft Word 15 (filtered
medium)">
<style>@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}@font-face
{font-family:DengXian;
panose-1:2 1 6 0 3 1 1 1 1 1;}@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}@font-face
{font-family:DengXian;
panose-1:2 1 6 0 3 1 1 1 1 1;}p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
text-align:justify;
font-size:10.5pt;
font-family:DengXian;}.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;
mso-ligatures:none;}div.WordSection1
{page:WordSection1;}</style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
<div class="WordSection1">
<p class="MsoNormal"><span lang="EN-US">Hello Bird Development
Team:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">We are AS140731, aka
TOHUNET, we use bird as our routing program, we have a
problem that may be related to the memory address of bird. <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Here are the problem
details:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">We designed a function
for anycast to balance the unequal length ASPATH between
different upstreams and different nodes, it has this
structure:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">function anycast(int
AS;int Region;int Country;int NodeID) {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> if net ~
[2406:840:eb8c::/48] then<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> case
NodeID {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> 1:
{<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">
case AS {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">
6939:
{bgp_path.prepend(140731);bgp_path.prepend(140731);}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">
}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Among them, AS
represents the peer AS of this session, and NodeID
represents the ID of this node. After the conditional
statement in the case matches the peer AS, as you can see,
it will execute bgp_path.prepend, and it works well when the
curly braces of the conditional statement are not empty. But
the aspath of some of our nodes is long enough that they
don't need to be prepend, so we have the following
configuration:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">function anycast(int
AS;int Region;int Country;int NodeID) {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> if net ~
[2406:840:eb8c::/48] then<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> case
NodeID {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> 1:
{<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">
case AS {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">
6939: {}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">
}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Then the problem
occurred. In our example, when the Session at 6939 was
established, the conditional statement matched 6939, but the
content in the curly braces was empty. At this time, bird
will be automatically killed and restarted by Linux due to a
memory segment fault. The following is the information we
get in journalctl:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">kernel: bird[11433]:
segfault at 0 ip 0000559bb2900c28 sp 00007ffcd21d1fc0 error
4 in bird[559bb2886000+9d000]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">kernel: Code: 8b 7b 04
83 03 01 41 8d 4f ff 0f 1f 84 00 00 00 00 00 89 cd 48 8d 44
6d 00 48 8d 14 c3 4c 8b a2 08 80 01 00 8b 82 10 80 01 00
<41> 3b 04 24 0f ><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">systemd[1]:
bird.service: Main process exited, code=killed,
status=11/SEGV<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The version number we
are currently using is: v2.13-5-gf8ba8280 debian11, but we
have tried to roll back to v2.13 and update to
v2.13-10-gf8bcb037, these problems still exist.<o:p></o:p></span></p>
</div>
</blockquote>
<pre class="moz-signature" cols="72">--
Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.</pre>
</body>
</html>