Hello,

Another workaround might be setting a metric different from system's routes in kernel protocol
to prevent system from rewriting existing routes.

Zhang Xun
 
From: Bastien Durel
Date: 2021-09-29 15:35
To: bird-users
Subject: OSPF on OpenBSD
Hello,
 
I'm trying to use bird to replace ospfd on OpenBSD, but it seems to
have a strange effect on the networking stack :(
 
I've tried multiple times, from OpenBSD 6.6 to 6.9, with bird2 (2.0.8
now)
 
Here is my bird config:
 
openbsd-test# cat /etc/bird.conf|grep -v ^#|grep -v '^$'
log "/var/log/bird.log" { debug, trace, info, remote, warning, error,
auth, fatal, bug };
router id 10.42.42.69;
debug protocols all;
protocol device {
}
protocol direct {
        disabled;               # Disable by default
        ipv4;                   # Connect to default IPv4 table
        ipv6;                   # ... and to default IPv6 table
}
protocol kernel {
        ipv4 {                  # Connect protocol to IPv4 table by
channel
              export all;       # Export to protocol. default is export
none
        };
}
protocol kernel {
        ipv6 { export all; };
}
protocol static {
        ipv4;                   # Again, IPv4 channel with default
options
}
protocol ospf v2 ospfv2 {
        rfc1583compat yes;
        tick 2;
        ipv4 {};
        area 0 {
             interface "em0" { cost 5; };
        };
}
 
And the em0 config:
em0:
flags=248843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,AUTOCONF6TEMP,AUTOC
ONF6> mtu 1500
        lladdr 08:00:27:d6:6e:dd
        index 1 priority 0 llprio 3
        groups: egress
        media: Ethernet autoselect (1000baseT full-duplex)
        status: active
        inet6 fe80::a00:27ff:fed6:6edd%em0 prefixlen 64 scopeid 0x1
        inet 10.42.42.69 netmask 0xffffff00 broadcast 10.42.42.255
 
Before starting bird, I have a simple routing table :
 
openbsd-test# route -n show -
inet                                                                   
                                                                       
                                                            
Routing tables
 
Internet:
Destination        Gateway            Flags   Refs      Use   Mtu  Prio
Iface
default            10.42.42.1         UGS        6       12     -     8
em0 
224/4              127.0.0.1          URS        0        0 32768     8
lo0 
10.42.42/24        10.42.42.69        UCn        2        0     -     4
em0 
10.42.42.1         40:62:31:07:55:11  UHLch      1        2     -     3
em0 
10.42.42.21        00:25:22:1e:0b:b7  UHLc       0        1     -     3
em0 
10.42.42.69        08:00:27:d6:6e:dd  UHLl       0        4     -     1
em0 
10.42.42.255       10.42.42.69        UHb        0        0     -     1
em0 
127/8              127.0.0.1          UGRS       0        0 32768     8
lo0 
127.0.0.1          127.0.0.1          UHhl       1        2 32768     1
lo0 
 
When bird is started, it inserts routes as intended:
 
openbsd-test# route -n show -inet
Routing tables
 
Internet:
Destination        Gateway            Flags   Refs      Use   Mtu  Prio
Iface
default            10.42.42.1         UGS        5      314     -     8
em0 
default            10.42.42.1         UG1        0        0     -    56
em0 
224/4              127.0.0.1          URS        0       19 32768     8
lo0 
5.39.65.35         10.42.42.1         UGH1       0        0     -    56
em0 
10.0.42.21         10.42.42.21        UGH1       0        0     -    56
em0 
10.2.0/24          10.42.42.1         UG1        0        0     -    56
em0 
10.42.0/24         10.42.42.1         UG1        0        0     -    56
em0 
10.42.1.56/30      10.42.42.21        UG1        0        0     -    56
em0 
10.42.1.64/30      10.42.42.21        UG1        0        0     -    56
em0  
10.42.7.6          10.42.42.21        UGH1       0        0     -    56
em0 
10.42.7.7          10.42.42.21        UGH1       0        0     -    56
em0 
10.42.7.53         10.42.42.21        UGH1       0        0     -    56
em0 
10.42.42/24        10.42.42.69        U1h       66      193     -    56
em0 
10.42.42.69        08:00:27:d6:6e:dd  UHLl       0      104     -     1
em0 
10.42.42.255       10.42.42.69        UHb        0       13     -     1
em0 
10.60.77.5         10.42.42.1         UGH1       0        0     -    56
em0 
[...]
 
But after that, the box cannot join anythin with IPv4. Established
connections (eg. ssh) over IPv4 fails. Even the gateway is unreachable:
 
openbsd-test# ping 10.42.42.1
PING 10.42.42.1 (10.42.42.1): 56 data bytes
ping: sendmsg: Invalid argument
ping: wrote 10.42.42.1 64 chars, ret=-1
ping: sendmsg: Invalid argument
ping: wrote 10.42.42.1 64 chars, ret=-1
^C
--- 10.42.42.1 ping statistics ---
2 packets transmitted, 0 packets received, 100.0% packet loss
 
With no ospfv3 configured, ipv6 connections are not lost
 
dmesg returns theses messages :
 
arp_rtrequest: bad gateway value: em0
arpresolve: 10.42.42.1: route contains no arp information
arpresolve: 10.42.42.0: route contains no arp information
arpresolve: 10.42.42.1: route contains no arp information
 
The last ones beeing flooded when the box tries to send packets
 
Whatever bird makes to the networking stack persists even if bird is
shut down. A reboot is necessary to recover.
 
On OpenBSD mailing list, someone said the problem may be bird
overwriting the 10.42.42/24 route (which was directly connected) by
another (the flags changed from UCn to U1h)
 
After stopping bird, flags and prios are not restored (10.42.42/24 gets
U1 / prio 56), and the default route kept is the one bird inserted
 
openbsd-test# route -n show -inet 
Routing tables
 
Internet:
Destination        Gateway            Flags   Refs      Use   Mtu  Prio
Iface
default            10.42.42.1         UG1        2        2     -    56
em0 
224/4              127.0.0.1          URS        0       13 32768     8
lo0 
10.42.42/24        10.42.42.69        U1         0       76     -    56
em0 
10.42.42.69        08:00:27:d6:6e:dd  UHLl       0       23     -     1
em0 
10.42.42.255       10.42.42.69        UHb        0        6     -     1
em0 
127/8              127.0.0.1          UGRS       0        0 32768     8
lo0 
127.0.0.1          127.0.0.1          UHhl       1        2 32768     1
lo0 
 
Do you know how to prevent that ?
 
Thanks,
 
 
--
Bastien