[Xen-bugs] [Bug 950] New: network-bridge script does not cope with more than one default route

[bugzilla-daemon@xxxxxxxxxxxxxxxxxxx]

http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=950

           Summary: network-bridge script does not cope with more than one
                    default route
           Product: Xen
           Version: 3.0.3
          Platform: x86-64
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Tools
        AssignedTo: xen-bugs@xxxxxxxxxxxxxxxxxxx
        ReportedBy: yrvafhom@xxxxxxxxxxxxxx


Due to earlier experiments with networking stuff, I ended up with more than one
default route configured on my host machine.

    [root@leucine ~]# ip route list
    169.254.0.0/16 dev eth0  scope link 
    10.0.0.0/8 dev eth0  proto kernel  scope link  src 10.0.0.8 
    default via 10.0.0.1 dev eth0 
    default via 10.0.0.20 dev eth0  metric 1 

The network-bridge script uses the following code to determine the initial
interface number:

    vifnum=${vifnum:-$(ip route list | awk '/^default / { print $NF }' | sed
's/^[^0-9]*//')}
    vifnum=${vifnum:-0}
    bridge=${bridge:-xenbr${vifnum}}
    netdev=${netdev:-eth${vifnum}}
    antispoof=${antispoof:-no}

    pdev="p${netdev}"
    vdev="veth${vifnum}"
    vif0="vif0.${vifnum}"

The bug is in the first line of this section
    vifnum=${vifnum:-$(ip route list | awk '/^default / { print $NF }' | sed
's/^[^0-9]*//')}

If you have more than one default route listed, then
        ip route list | awk '/^default / { print $NF }'
will return more than one line

    [root@leucine ~]# ip route list | awk  '/^default / { print $NF }'
    eth0
    1

This means vifnum, pdev, vdev and vif0 all get corrupted values at the start of
the network-bridge script, effectively "0\n1", "peth0\n1" etc.

If this happens, the debug log contains a clue - the newline character is
output in the error message :

    Link veth0
    1 is missing.
    This may be because you have reached the limit of the number of interfaces
    ....

Quick fix - remove the second default route on the host system.
Long term - fix the script to detect more than one line, or change the error
message (nothing to do with limit on loopback addresses).


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