[RFC][BUGFIX][vif-route] vif-route script exits early when deleting vifs

[Reiner Sailer <sailer@us.ibm.com>]

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I have experienced that the vif-route script does not work as expected 
when deleting a virtual interface (Redhat FC5). Both of the commands 
"ifdown" and "ip route" cause an early vif-route script exit and 
therefore will cause skipping of the later script commands (such as 
cleaning up iptables entries for the default 'antispoof'). The vif-route 
script creates the following syslog error entry: 
"/etc/xen/scripts/vif-route failed; error detected."

It appears that both of the problematic commands are actually redundant 
when destroying domains:
1. the interface is already gone (I assume because the domain frontend 
is gone already)  --> ifdown does not do anything
2. the route is gone as well since the interface has disappeared --> ip 
route del does not do anything

Executing those redundant commands with "do_without_error" ensures that 
the script completes and cleans up iptables rules. The attached 
RFC-patch only masks those commands when bringing down an interface, so 
that domain creation continues to fail in case of vif setup problems 
(intended behavior).

Having the iptables cleanup called correctly by vif-route is important 
to keep the iptables rule-set clean, otherwise antispoof rules 
accumulate with every vif creation..

Comments welcome.

Reiner

Signed-off by: Reiner Sailer <sailer@us.ibm.com>


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---
 tools/examples/vif-route |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Index: xen-unstable.hg_test/tools/examples/vif-route
===================================================================
--- xen-unstable.hg_test.orig/tools/examples/vif-route
+++ xen-unstable.hg_test/tools/examples/vif-route
@@ -30,10 +30,12 @@ case "$command" in
         ifconfig ${vif} ${main_ip} netmask 255.255.255.255 up
         echo 1 >/proc/sys/net/ipv4/conf/${vif}/proxy_arp
         ipcmd='add'
+        cmdprefix=''
         ;;
     offline)
-        ifdown ${vif}
+        do_without_error ifdown ${vif}
         ipcmd='del'
+        cmdprefix='do_without_error'
         ;;
 esac
 
@@ -41,7 +43,7 @@ if [ "${ip}" ] ; then
     # If we've been given a list of IP addresses, then add routes from dom0 to
     # the guest using those addresses.
     for addr in ${ip} ; do
-      ip route ${ipcmd} ${addr} dev ${vif} src ${main_ip}
+      ${cmdprefix} ip route ${ipcmd} ${addr} dev ${vif} src ${main_ip}
     done 
 fi
 

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