Route withdrawn via pipe to another kernel table causes segfault crash
Joel Mulkey
joelm at bigleaf.net
Wed Jun 12 07:21:53 CEST 2013
Hello,
We are running BIRD v1.3.10 and are seeing an issue that is causing BIRD to crash. In this setup we're running one "core" router that's using a single routing table, an OSPF protocol, and 2 BGP protocols. That core router connects to 2 remote routers that are running one OSPF protocol, one BGP protocol, and using 2 routing tables (main and one other). The routing tables are connected via pipe, and they are both connected to Linux tables via the kernel protocols.
The issue we're seeing is that when a route is withdrawn (we're only installing the default route) from the 2nd routing table on the remote routers it crashes BIRD with a segfault. This is typically caused by a loss in connectivity on the network that tears down the OSPF and BGP sessions.
We tried a number of things to prevent the issue from happening. If we prevent either the pipe or kernel protocols from exporting routes then the issue does not occur. We also tried setting the pipe to opaque mode and that immediately causes a segfault on start up. This appears to be a bug with the kernel or pipe protocol, but I'm certainly no expert and would love some guidance if there's a workaround or error in my config.
Below is the remote router config, and some snippits of the syslog with the segfaults.
Thanks,
Joel Mulkey
function infrastructure() {
if net = 10.99.0.4/32 then return true;
if net ~ [10.2.0.0/30+] then return true;
if net ~ [172.17.1.0/24+] then return true;
if net ~ [172.17.2.0/24+] then return true;
if net ~ [172.17.3.0/24+] then return true;
if net ~ [172.17.4.0/24+] then return true;
return false;
}
function default_only() {
return net = 0.0.0.0/0;
}
filter table2_out_filter {
if ! defined( krt_metric ) then accept;
if krt_metric > 1 then reject;
else accept;
}
filter ospf_out {
if infrastructure() then accept;
else reject;
}
filter bgp_out {
if infrastructure() then reject;
if ! defined( krt_metric ) then accept;
if krt_metric > 19 then {
bgp_local_pref = 90;
accept;
}
else accept;
}
table table2;
router id 10.99.0.4;
log syslog all;
debug protocols { states, routes, filters, interfaces };
protocol kernel kmain {
learn; # Learn all alien routes from the kernel
persist; # Don't remove routes on bird shutdown
scan time 2; # Scan kernel routing table every 10 seconds
import all; # Default is import all
export all; # Default is export none
preference 190;
}
protocol kernel ktable2 {
persist; # Don't remove routes on bird shutdown
scan time 2; # Scan kernel routing table every 2 seconds
import none; # Default is import all
export filter table2_out_filter; # Default is export none
kernel table 100; # Kernel table to synchronize with (default: main)
table table2; # connect to alternate BIRD table
}
# This pseudo-protocol watches all interface up/down events.
protocol device {
scan time 2; # Scan interfaces every 2 seconds
}
# Pipe protocol connects two routing tables... Beware of loops.
# Connect table2 to main
protocol pipe {
mode transparent;
peer table table2;
export all;
import none;
}
protocol ospf to_core_ospf {
debug { events };
export filter ospf_out;
import all;
area 0.0.0.0 {
stubnet 10.99.0.4/32;
interface 10.2.0.2 {
hello 1;
retransmit 2;
cost 10;
dead 5;
wait 4;
type broadcast;
};
};
}
protocol bgp bgp_peer_1 {
local as 64600;
export filter bgp_out;
import all;
source address 10.99.0.4;
next hop self;
neighbor 10.99.0.1 as 64600;
multihop 20;
hold time 12;
keepalive time 3;
startup hold time 10;
connect retry time 5;
start delay time 5;
error wait time 30, 120;
}
Jun 11 21:16:44 tunnel2 bird: bgp_peer_1: Error: Hold timer expired
Jun 11 21:16:44 tunnel2 bird: bgp_peer_1: State changed to flush
Jun 11 21:16:44 tunnel2 bird: bgp_peer_1 > removed [sole] 0.0.0.0/0 unreachable
Jun 11 21:16:44 tunnel2 bird: pipe1 < removed 0.0.0.0/0 unreachable
Jun 11 21:16:44 tunnel2 bird: pipe1 > removed [sole] 0.0.0.0/0 unreachable
Jun 11 21:16:44 tunnel2 bird: ktable2 < removed 0.0.0.0/0 unreachable
Jun 11 21:16:44 tunnel2 bird: kmain < removed 0.0.0.0/0 unreachable
Jun 11 21:16:44 tunnel2 kernel: [ 769.220353] bird[4516]: segfault at 18 ip 00007ff0e8e44e26 sp 00007fffc45719f0 error 4 in bird[7ff0e8e3a000+5e000]
Jun 11 21:27:09 tunnel2 bird: to_core_ospf: Scheduling routing table calculation
Jun 11 21:27:09 tunnel2 bird: to_core_ospf: Neighbor 10.2.0.1 changes state from " loading" to " full".
Jun 11 21:27:09 tunnel2 bird: to_core_ospf: Scheduling router-LSA origination for area 0.0.0.0
Jun 11 21:27:09 tunnel2 bird: to_core_ospf: Scheduling network-LSA origination for iface eth0
Jun 11 21:27:10 tunnel2 bird: bgp_peer_1: Error: Hold timer expired
Jun 11 21:27:10 tunnel2 bird: bgp_peer_1: State changed to flush
Jun 11 21:27:10 tunnel2 bird: to_core_ospf: Originating network-LSA for iface eth0
Jun 11 21:27:10 tunnel2 kernel: [ 1395.215433] bird[5318]: segfault at 18 ip 00007f6232c2ae26 sp 00007fff05713ea0 error 4 in bird[7f6232c20000+5e000]
mode opaque causing immediate segfault on restart
Jun 11 21:44:05 tunnel1 bird: kmain: Initializing
Jun 11 21:44:05 tunnel1 bird: ktable2: Initializing
Jun 11 21:44:05 tunnel1 bird: device1: Initializing
Jun 11 21:44:05 tunnel1 bird: pipe1: Initializing
Jun 11 21:44:05 tunnel1 bird: bgp_peer_1: Initializing
Jun 11 21:44:05 tunnel1 bird: device1: Starting
Jun 11 21:44:05 tunnel1 bird: device1: Connected to table master
Jun 11 21:44:05 tunnel1 bird: device1: State changed to feed
Jun 11 21:44:05 tunnel1 bird: kmain: Starting
Jun 11 21:44:05 tunnel1 bird: kmain: Connected to table master
Jun 11 21:44:05 tunnel1 bird: kmain: State changed to feed
Jun 11 21:44:05 tunnel1 bird: ktable2: Starting
Jun 11 21:44:05 tunnel1 bird: ktable2: Connected to table table2
Jun 11 21:44:05 tunnel1 bird: ktable2: State changed to feed
Jun 11 21:44:05 tunnel1 bird: pipe1: Starting
Jun 11 21:44:05 tunnel1 bird: pipe1: Connected to table master
Jun 11 21:44:05 tunnel1 bird: pipe1: Connected to table table2
Jun 11 21:44:05 tunnel1 bird: pipe1: State changed to feed
Jun 11 21:44:05 tunnel1 bird: to_core_ospf: Adding area 0.0.0.0
Jun 11 21:44:05 tunnel1 bird: bgp_peer_1: Starting
Jun 11 21:44:05 tunnel1 bird: Started
Jun 11 21:44:05 tunnel1 bird: device1: State changed to up
Jun 11 21:44:05 tunnel1 bird: kmain: State changed to up
Jun 11 21:44:05 tunnel1 bird: ktable2: State changed to up
Jun 11 21:44:05 tunnel1 bird: pipe1: State changed to up
Jun 11 21:44:05 tunnel1 bird: to_core_ospf: Adding interface eth0 (10.1.0.0/30) to area 0.0.0.0
Jun 11 21:44:05 tunnel1 bird: kmain > added [best] 172.16.4.0/24 via 172.16.4.2 on tun4
Jun 11 21:44:05 tunnel1 bird: kmain < rejected by protocol 172.16.4.0/24 via 172.16.4.2 on tun4
Jun 11 21:44:05 tunnel1 bird: pipe1 < added 172.16.4.0/24 via 172.16.4.2 on tun4
Jun 11 21:44:05 tunnel1 bird: pipe1 > added [best] 172.16.4.0/24 via 172.16.4.2 on tun4
Jun 11 21:44:05 tunnel1 bird: kvpn_output < added 172.16.4.0/24 via 172.16.4.2 on tun4
Jun 11 21:44:05 tunnel1 bird: pipe1 < rejected by protocol 172.16.4.0/24 via 172.16.4.2 on tun4
Jun 11 21:44:05 tunnel1 kernel: [ 2403.848692] bird[5450]: segfault at 18 ip 00007f0cc629f277 sp 00007fff33e14ed8 error 4 in bird[7f0cc6271000+5e000]
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