[Xorp-users] Wrong IP address used for GRE interface

[Andriy Senkovych]

Hello, xorp-users!

I'm using Xorp 1.8.3 package on Debian for PIM-SM over GRE/IPSec. I
used slightly modified default config. I use such tunnels to access
both worker machines and data provider:

The config file has the following interfaces section:

interfaces {
    restore-original-config-on-shutdown: false
    interface cme-gw {
        description: "Tunnel interface to data provider"
        disable: false
        default-system-config
    }

    interface cme-dev {
        description: "Tunnel interface to worker machine"
        disable: false
        default-system-config
    }
}

As a result I get the following interfaces configuration:

> show interfaces
cme-dev/cme-dev: Flags:<ENABLED,MULTICAST,POINTTOPOINT> mtu 1476 speed unknown
        inet 10.145.0.129 subnet 10.145.0.129/32 --> 10.145.129.63
        inet 10.145.2.122 subnet 10.145.2.120/30 --> 10.145.2.122
        physical index 5
cme-gw/cme-gw: Flags:<ENABLED,MULTICAST,POINTTOPOINT> mtu 1476 speed unknown
        inet 10.145.0.129 subnet 10.145.0.129/32 --> 10.145.254.1
        inet 10.145.2.222 subnet 10.145.2.220/30 --> 10.145.2.222
        physical index 4

My actual configuration for these interfaces is:

$ ip a l
4: cme-gw: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1476 qdisc
noqueue state UNKNOWN
    link/gre 10.145.0.129 peer 10.145.254.1
    inet 10.145.2.222/30 scope global cme-gw
5: cme-dev: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1476 qdisc
noqueue state UNKNOWN
    link/gre 10.145.0.129 peer 10.145.129.63
    inet 10.145.2.122/30 scope global cme-dev

Using config above I get the following pim interfaces configuration:

> show pim interface
Interface    State    Mode   V PIMstate Priority DRaddr          Neighbors
cme-dev      UP       Sparse 2 DR              1 10.145.0.129            0
cme-gw       UP       Sparse 2 DR              1 10.145.0.129            0

And PIM_HELLO packets are sent with wrong parameters:

[ 2011/12/28 13:07:18.8664 TRACE xorp_pimsm4 PIM ] pim_send: TX
PIM_HELLO from 10.145.0.129 to 224.0.0.13 on vif cme-gw
[ 2011/12/28 13:07:20.817323 TRACE xorp_pimsm4 PIM ] pim_send: TX
PIM_HELLO from 10.145.0.129 to 224.0.0.13 on vif cme-dev

Here you can see that xorp has chosen wrong IP address to send the
packets (10.145.0.129 instead of 10.145.2.222 for cme-gw and
10.145.2.122 for cme-dev)

I have similar(but working) environment to get data from another data
provider. Its interfaces settings are:

$ ip a l
4: tun247102: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1476 qdisc
noqueue state UNKNOWN
    link/gre 192.168.247.29 peer 192.168.0.84
    inet 10.100.247.102/30 scope global tun247102
5: rts-dev: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1476 qdisc
noqueue state UNKNOWN
    link/gre 192.168.247.29 peer 192.168.133.10
    inet 10.100.133.14/30 scope global rts-dev

> show interfaces
rts-dev/rts-dev: Flags:<ENABLED,MULTICAST,POINTTOPOINT> mtu 1476 speed unknown
        inet 10.100.133.14 subnet 10.100.133.12/30 --> 10.100.133.14
        inet 192.168.247.29 subnet 192.168.247.29/32 --> 192.168.133.10
        physical index 5
tun247102/tun247102: Flags:<ENABLED,MULTICAST,POINTTOPOINT> mtu 1476
speed unknown
        inet 10.100.247.102 subnet 10.100.247.100/30 --> 10.100.247.102
        inet 192.168.247.29 subnet 192.168.247.29/32 --> 192.168.0.84
        physical index 4

> show pim interfaces
Interface    State    Mode   V PIMstate Priority DRaddr          Neighbors
rts-dev      UP       Sparse 2 DR              1 10.100.133.14           0
tun247102    UP       Sparse 2 DR              1 10.100.247.102          1

>From this I make the conclusion that xorp takes the first available
configuration and uses is as a default. However as you can see this
will work only when IP address of GRE tunnel is smaller than local IP
address used to setup this GRE tunnel.

I tried both using default-system-config and manual interfaces
configuration but this didn't help.

Is there any solution for this problem?

-- 
WBR, Andriy Senkovych