inetinfo.go

// InetInfo gathers information about different net interfaces and their
// IP addresses and returns that as a string for debug purposes.
// Returns an error string if errors occurred.
func InetInfo() string {
    // Loop over all the interfaces
    ifaces, err := net.Interfaces()
    if err != nil {
        return fmt.Sprintf("Error retrieving interfaces: %v", err.Error())
    }

    // This will map interface name to textual representations of its
    // IP addresses
    addrMap := map[string][]string{}

    for _, i := range ifaces {
        // Loop over all addresses for that interface
        addrs, err := i.Addrs()
        if err != nil {
            return fmt.Sprintf("Error retrieving addresses: %v", err.Error())
        }

        addrList := make([]string, 0)

        for _, addr := range addrs {
            var ip net.IP
            switch v := addr.(type) {
            case *net.IPAddr:
                ip = v.IP
            case *net.IPNet:
                ip = v.IP
            default:
                // Skip others
                continue
            }

            addr := ""
            if ipv4 := ip.To4(); ipv4 != nil {
                addr = fmt.Sprintf("  IPv4 addr: %v", ip.String())
            } else {
                addr = fmt.Sprintf("  IPv6 addr: %v", ip.String())
            }
            addrList = append(addrList, addr)
        }

        if len(addrList) > 0 {
            addrMap[i.Name] = addrList
        }
    }

    s := ""
    for ifName, addrList := range addrMap {
        s += fmt.Sprintf("\n\nInterface: %v", ifName)
        for _, a := range addrList {
            s += fmt.Sprintf("\n  %v", a)
        }
    }

    return strings.TrimLeft(s, "\n ")
}