func (m *mapping) tryNATPMPGW(gw net.IP, destroy bool) bool {
var externalPort uint16
var actualLifetime time.Duration
var err error
var preferredLifetime time.Duration
if destroy && !m.lIsActive() {
// no point destroying if we're not active
return true
} else if !destroy {
// lifetime is zero if we're destroying
preferredLifetime = m.cfg.Lifetime
}
// attempt mapping
externalPort, actualLifetime, err = natpmp.Map(gw,
natpmp.Protocol(m.cfg.Protocol), m.cfg.InternalPort, m.cfg.ExternalPort, preferredLifetime)
if err != nil {
log.Infof("NAT-PMP failed: %v", err)
return false
}
m.mutex.Lock()
m.cfg.ExternalPort = externalPort
m.cfg.Lifetime = actualLifetime
m.mutex.Unlock()
if preferredLifetime == 0 {
// we have finished tearing down the mapping by mapping it with a
// lifetime of zero, so return
return true
}
expireTime := time.Now().Add(actualLifetime)
// Now attempt to get the external IP.
extIP, err := natpmp.GetExternalAddr(gw)
m.mutex.Lock()
defer m.mutex.Unlock()
// update external address
if err == nil {
m.externalAddr = extIP.String()
}
m.expireTime = expireTime
return true
}
// 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
}