Split listening port argument at the rightmost colon, allows binding to specific IPv6 addresses. From OpenWRT, https://dev.openwrt.org/browser/trunk/package/dropbear/patches/300-ipv6_addr_port_split.patch

#!/bin/bash
if cvs log $1 >/dev/null 2>/dev/null; then exit 0; else echo "$1 shouldn't be here" ; exit 1; fi