Unable to fetch route from tunnel device

14 Feb 2012

      I'm trying to set up an OpenVPN server that routes for multiple sites and
I'm having a bit of trouble getting Bird to add the routes that go through
the tun0 device. I've configured Bird to import routes from both the OS and
tun0, but filter out any routes that don't go through the tun0 IP (I only
want to advertise routes that go through my OpenVPN tunnel). I'm running
Bird 1.3.6. On startup, I receive messages like these:
...
...
...
KRT: Received route 172.24.1.16/28 with strange next-hop 172.16.254.1
Netlink: File exists
Netlink: File exists
OSPF: Socket error: Operation not permitted
This appears to be coming from this section of code:
sysdep/linux/netlink/netlink.c: 846

      if (!ng || (ng->scope == SCOPE_HOST))
        {
          log(L_ERR "KRT: Received route %I/%d with strange next-hop %I",
          net->n.prefix, net->n.pxlen, ra.gw);
          return;
        }

My network setup is as follows:
Local IP of tun0 on OpenVPN server: 172.16.254.1/24
IP of tun0 on remote server: 172.24.1.28/28

Routes (from ip route) on OpenVPN server:
172.16.254.1 dev tun0  proto bird
172.24.1.0/28 via 172.16.254.1 dev tun0
172.24.1.16/28 via 172.16.254.1 dev tun0

Routes (from ip route) on OpenVPN client:
172.16.0.0/24 via 172.24.1.28 dev tun0

Bird config:
log syslog { debug, trace, info, remote, warning, error, auth, fatal, bug };
filter no_local
prefix set local_nets;
ip tun0;
{
    local_nets = [ 172.16.0.0/16+ , 192.168.0.0/16+ , 10.0.0.0/8+ ];
    tun0 = 172.16.254.1;
    printn "gw: ", gw;
    if gw = tun0 then accept "accept: gw is ",gw;
    reject "reject: gw is ", gw;
}
protocol kernel {
    learn;            # Learn all alien routes from the kernel
    persist;        # Don't remove routes on bird shutdown
    scan time 10;        # Scan kernel routing table every 20 seconds
    device routes on;   # this is on so we can accept routes with local
nexthop
    import filter no_local; # don't import "local" networks
    import none;        # Default is import all
    export all;        # Default is export none
}
protocol device {
    scan time 10;        # Scan interfaces every 10 seconds
}
protocol static {
}
protocol direct {
    interface "tun0";
}
protocol ospf MFOSPF {
    export all;
    area 172.16.0.0 {
        interface "eth4" {
            type broadcast;
            authentication none;
            neighbors { 10.19.7.11; };
        };
        interface "tun0" {
            type ptmp;
            authentication none;
        };
    };
}

Any ideas about what I'm doing wrong here? The network configuration (aside
from Bird) works as I can ping from another IP, 172.16.1.11, through the
OpenVPN server and out to 172.24.1.28. Is there a way to get Bird to
advertise a route via OSPF that goes through a local IP (for a tun device)
that is not on the same subnet as the remote network?

Thanks much!

--dlloyd

Unable to fetch route from tunnel device

Dave Lloyd