suppress ipv6 noise between veth interfaces

tools/setup_bridge_capture.sh

@@ -68,6 +68,8 @@ fi
 
 ip link set "$MIRROR_IF" up
 ip link set "$CAPTURE_IF" up
+sysctl -q -w "net.ipv6.conf.$MIRROR_IF.disable_ipv6=1" >/dev/null || true
+sysctl -q -w "net.ipv6.conf.$CAPTURE_IF.disable_ipv6=1" >/dev/null || true
 
 mapfile -t PORTS < <(bridge link show master "$BRIDGE" | awk -F': ' '{print $2}' | awk '{print $1}')
 if [[ ${#PORTS[@]} -eq 0 ]]; then