use default ip for advertise URL

[heyitsanthony]

Fixes #2858

[gyuho]

Is there anyway that I can try GetDefaultHost? In my linux machine, I get

could not find default route

[heyitsanthony]

@gyuho huh, works on my machine. Is it failing to get defaultNlMsg or is it failing to find the RTA_PREFSRC? I'll see if it works on my ubuntu machine...

[gyuho]

@heyitsanthony It's returning here

...
    for _, attr := range attrs {
        if attr.Attr.Type == syscall.RTA_PREFSRC {
            return net.IP(attr.Value).String(), nil
        }
    }

    // returns here
    return "", errNoDefaultRoute
}

go version go1.7rc6 linux/amd64

Linux gyuho 4.4.0-34-generic #53-Ubuntu SMP Wed Jul 27 16:06:39 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

[heyitsanthony]

@gyuho OK, could reproduce on my ubuntu machine; can work around. Thanks for giving this a spin!

[heyitsanthony]

had to query the iface to get the address on ubuntu /cc @gyuho

[gyuho]

Ok works now. Mine is

10.0.0.30

LGTM. /cc @xiang90

[xiang90]

i do not think we should listen on wide by default even if we found the default host for security reasons. by finding default adv url, users do not need to set avd ulrs themselves but not listen url I think.

[heyitsanthony]

ok

[heyitsanthony]

@xiang90 all fixed up

[xiang90]

using detected default host

[xiang90]

lgtm