No configuration to turn off dhcpv6 release on interface teardown

[timcoote]

Sometimes it's useful not to get a new ipv6 prefix every time the interface to the isp bounces. At least one ISP delivers a different prefix if the dhcpv6 release flag is sent. By default, tearing down an interface sends this flag.

odhcpv6 has a command line flag for this (-k) , and uci has a configuration flag to control invocation of this flag (norelease: default false), but I cannot see a way to set the flag from a hnetd configuration.