begin meek-webrtc signalling channel for client (issue #1)

client/meek-webrtc.go

@@ -0,0 +1,84 @@
+// Exchange WebRTC SessionDescriptions over meek.
+// Much of this source is extracted from meek-client.go.
+package main
+
+import (
+	"bytes"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+
+	"github.com/keroserene/go-webrtc"
+)
+
+// RequestInfo encapsulates all the configuration used for a request–response
+// roundtrip, including variables that may come from SOCKS args or from the
+// command line.
+type RequestInfo struct {
+	// What to put in the X-Session-ID header.
+	// SessionID string
+	// The URL to request.
+	URL *url.URL
+	// The Host header to put in the HTTP request (optional and may be
+	// different from the host name in URL).
+	Host string
+}
+
+func NewRequestInfo(meekUrl string, front string) *RequestInfo {
+	info := new(RequestInfo)
+	requestUrl, err := url.Parse(meekUrl)
+	if nil != err {
+		return nil
+	}
+	info.URL = requestUrl
+	info.Host = info.URL.Host
+	info.URL.Host = front
+	return info
+}
+
+// Meek Signalling Channel
+type MeekChannel struct {
+	info *RequestInfo
+	// Used to make all requests.
+	transport http.Transport
+}
+
+func NewMeekChannel(info *RequestInfo) *MeekChannel {
+	m := new(MeekChannel)
+	// We make a copy of DefaultTransport because we want the default Dial
+	// and TLSHandshakeTimeout settings. But we want to disable the default
+	// ProxyFromEnvironment setting. Proxy is overridden below if
+	// options.ProxyURL is set.
+	m.transport = *http.DefaultTransport.(*http.Transport)
+	m.transport.Proxy = nil
+	m.info = info
+	return m
+}
+
+// Do an HTTP roundtrip using the payload data in buf.
+func (m *MeekChannel) roundTripHTTP(buf []byte) (*http.Response, error) {
+	req, err := http.NewRequest("POST", m.info.URL.String(), bytes.NewReader(buf))
+	if nil != err {
+		return nil, err
+	}
+	if "" != m.info.Host {
+		req.Host = m.info.Host
+	}
+	// req.Header.Set("X-Session-Id", m.info.SessionID)
+	return m.transport.RoundTrip(req)
+}
+
+// Send an SDP offer to the meek facilitator, and wait for an SDP answer from
+// the assigned proxy in the response.
+func (m *MeekChannel) Negotiate(offer *webrtc.SessionDescription) (
+	*webrtc.SessionDescription, error) {
+	buf := []byte(offer.Serialize())
+	resp, err := m.roundTripHTTP(buf)
+	if nil != err {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	answer := webrtc.DeserializeSessionDescription(string(body))
+	return answer, nil
+}