"Address in use error" when starting IPv6 listener on port with started IPv4 listener

[lleachii]

@FischC

Someone else observing this beahviour? Any advice if I'm doing something wrong?

@jow

the TCP6 listen spec. Without it, the IPv6 listener socket will be dual stack, supporting IPv4 clients through v6 mapped addresses.

More information:

@lleachii

• https://lwn.net/Articles/688462/
• https://unix.stackexchange.com/questions/152612/netstat-why-are-ipv4-daemons-listening-to-ports-listed-only-in-a-inet6

For the whole system:

@lleachii

root@OpenWrt:~# sysctl net.ipv6.bindv6only
net.ipv6.bindv6only = 0