// Creates a port mapping. The mapping process is continually attempted and
// maintained in the background, but the Mapping interface is returned
// immediately without blocking.
//
// As the mapping is attempted asynchronously in the background, the mapping
// will not be active when this function returns. Use the Mapping interface
// returned to determine when the mapping becomes active.
//
// A successful mapping is not guaranteed.
//
// See the Config struct and the Mapping interface for more information.
func New(cfg Config) (Mapping, error) {
if IsGloballyRoutable() {
return nil, ErrGlobalIP
}
gwa, err := gateway.GetIPs()
if err != nil {
return nil, err
}
if cfg.Lifetime == 0 {
cfg.Lifetime = DefaultLifetime
}
m := &mapping{
cfg: cfg,
abortChan: make(chan struct{}),
notifyChan: make(chan struct{}, 1),
}
ssdp.Start()
go m.portMappingLoop(gwa)
return m, nil
}
// Attempt to obtain the external IP address from the default gateway.
//
// If the host has a globally routable IP, returns that IP.
//
// Currently this only tries NAT-PMP and does not attempt to learn the external
// IP address via UPnP.
//
// This function is not very useful because the IP address returned may still
// be an RFC1918 address, due to the possibility of a double NAT setup. There
// are better solutions for obtaining one's public IP address, such as STUN.
func ExternalAddr() (net.IP, error) {
if gr, ip := isGloballyRoutable(); gr {
return ip, nil
}
gwa, err := gateway.GetIPs()
if err != nil {
return nil, err
}
var extaddr net.IP
for _, gw := range gwa {
extaddr, err = natpmp.GetExternalAddr(gw)
if err == nil {
return extaddr, nil
}
}
return nil, err
}