webrtc/internal/stun/stun.go

package stun

import (
	"fmt"
	"net"
	"time"

	"github.com/pions/pkg/stun"
	"github.com/pions/webrtc/internal/ice"
	"github.com/pkg/errors"
)

// Allocate crafts and sends a STUN binding
// On success will return our XORMappedAddress
func Allocate(url *ice.URL) (*ice.CandidateSrflx, error) {
	// TODO Do we want the timeout to be configurable?
	proto := url.TransportType.String()
	client, err := stun.NewClient(proto, fmt.Sprintf("%s:%d", url.Host, url.Port), time.Second*5)
	if err != nil {
		return nil, errors.Wrapf(err, "Failed to create STUN client")
	}
	localAddr, ok := client.LocalAddr().(*net.UDPAddr)
	if !ok {
		return nil, errors.Errorf("Failed to cast STUN client to UDPAddr")
	}

	resp, err := client.Request()
	if err != nil {
		return nil, errors.Wrapf(err, "Failed to make STUN request")
	}

	if err = client.Close(); err != nil {
		return nil, errors.Wrapf(err, "Failed to close STUN client")
	}

	attr, ok := resp.GetOneAttribute(stun.AttrXORMappedAddress)
	if !ok {
		return nil, errors.Errorf("Got respond from STUN server that did not contain XORAddress")
	}

	var addr stun.XorAddress
	if err = addr.Unpack(resp, attr); err != nil {
		return nil, errors.Wrapf(err, "Failed to unpack STUN XorAddress response")
	}

	return &ice.CandidateSrflx{
		CandidateBase: ice.CandidateBase{
			Protocol: ice.TransportUDP,
			Address:  addr.IP.String(),
			Port:     addr.Port,
		},
		RemoteAddress: localAddr.IP.String(),
		RemotePort:    localAddr.Port,
	}, nil
}