net: inaccurate docs about announcing or listening on all local addresses

[mikioh]

The current documentation says:

func Listen, ListenPacket, Listen{TCP,UDP,UP}

Listen listens on all available interfaces instead of just the interface with the given
host address. 

I think it provides inaccurate information. What happens when you move an interface address on network interface X to another? Does it break your application? (Please consider that how VRRP or CARP works) Actually it announcing or listening on all local addresses.

[quentinmit]

I don't understand the question. I read the docs as saying "Listen without a host address listens on all possible addresses on all interfaces". I think it's unspecified whether it picks up changes to the host's interfaces after startup - on *nix I expect that it would, but I don't think we guarantee that.

[mikioh]

@quentinmit,

From architectural point of view, an IP address is basically assigned to a link (or an interface or network interface which is an attachment to the link), agree. But practically, there are implementations that have addresses not assigned to link or interface; for example, 127.0.0.1/8 or IPv6 loopback address. I personally don't want to see an issue like "the Addr method of net.Interface doesn't show 127.0.0.1/8 but net.Listen("tcp", "127.0.0.1:0") works perfectly. Is this a bug?"

[gopherbot]

CL https://golang.org/cl/34876 mentions this issue.