contest: virtio: improve v6 address config

nodad to reliably avoid waits, and don't flush on down.
Otherwise destructive tests flush the addresses for everyone.

Signed-off-by: Jakub Kicinski <[email protected]>

Author: kuba-moo

contest/scripts/vm-virtio-loop.sh

@@ -24,9 +24,12 @@ ip -netns ns-remote addr add dev eth1 192.0.2.2/24
 export  LOCAL_V4=192.0.2.1
 export REMOTE_V4=192.0.2.2
 
-ip                  addr add dev eth0 2001:db8::1/64
-ip -netns ns-remote addr add dev eth1 2001:db8::2/64
+ip                  addr add dev eth0 2001:db8::1/64 nodad
+ip -netns ns-remote addr add dev eth1 2001:db8::2/64 nodad
 export  LOCAL_V6=2001:db8::1
 export REMOTE_V6=2001:db8::2
 
-sleep 2
+sysctl -w net.ipv6.conf.eth0.keep_addr_on_down=1
+# We don't bring remote down, it'd break remote via SSH
+
+sleep 1