// NewMapping attemps to construct a mapping on protocol and internal port
// It will also periodically renew the mapping until the returned Mapping
// -- or its parent NAT -- is Closed.
//
// May not succeed, and mappings may change over time;
// NAT devices may not respect our port requests, and even lie.
// Clients should not store the mapped results, but rather always
// poll our object for the latest mappings.
func (nat *NAT) NewMapping(maddr ma.Multiaddr) (Mapping, error) {
if nat == nil {
return nil, fmt.Errorf("no nat available")
}
network, addr, err := manet.DialArgs(maddr)
if err != nil {
return nil, fmt.Errorf("DialArgs failed on addr:", maddr.String())
}
switch network {
case "tcp", "tcp4", "tcp6":
network = "tcp"
case "udp", "udp4", "udp6":
network = "udp"
default:
return nil, fmt.Errorf("transport not supported by NAT: %s", network)
}
intports := strings.Split(addr, ":")[1]
intport, err := strconv.Atoi(intports)
if err != nil {
return nil, err
}
m := &mapping{
nat: nat,
proto: network,
intport: intport,
intaddr: maddr,
}
m.proc = goprocess.WithTeardown(func() error {
nat.rmMapping(m)
return nil
})
nat.addMapping(m)
m.proc.AddChild(periodic.Every(MappingDuration/3, func(worker goprocess.Process) {
nat.establishMapping(m)
}))
// do it once synchronously, so first mapping is done right away, and before exiting,
// allowing users -- in the optimistic case -- to use results right after.
nat.establishMapping(m)
return m, nil
}
func ExampleEvery() {
tock := make(chan struct{})
i := 0
p := periodicproc.Every(time.Second, func(proc goprocess.Process) {
tock <- struct{}{}
fmt.Printf("hello %d\n", i)
i++
})
<-tock
<-tock
<-tock
p.Close()
// Output:
// hello 0
// hello 1
// hello 2
}