mirror of
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake.git
synced 2025-10-14 14:11:23 -04:00
move CORS early return into the ServeHTTP wrapper, rename handlers
This commit is contained in:
Serene Han
parent
791f6925ec
commit
2ae6559001
2 changed files with 103 additions and 112 deletions
168
broker/broker.go
168
broker/broker.go
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@ -28,27 +28,34 @@ type BrokerContext struct {
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snowflakes *SnowflakeHeap
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// Map keeping track of snowflakeIDs required to match SDP answers from
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// the second http POST.
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snowflakeMap map[string]*Snowflake
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proxyPolls chan *ProxyPoll
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idToSnowflake map[string]*Snowflake
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proxyPolls chan *ProxyPoll
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}
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func NewBrokerContext() *BrokerContext {
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snowflakes := new(SnowflakeHeap)
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heap.Init(snowflakes)
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return &BrokerContext{
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snowflakes: snowflakes,
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snowflakeMap: make(map[string]*Snowflake),
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proxyPolls: make(chan *ProxyPoll),
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snowflakes: snowflakes,
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idToSnowflake: make(map[string]*Snowflake),
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proxyPolls: make(chan *ProxyPoll),
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}
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}
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// Implements the http.Handler interface
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type SnowflakeHandler struct {
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*BrokerContext
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h func(*BrokerContext, http.ResponseWriter, *http.Request)
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handle func(*BrokerContext, http.ResponseWriter, *http.Request)
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}
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func (sh SnowflakeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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sh.h(sh.BrokerContext, w, r)
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w.Header().Set("Access-Control-Allow-Origin", "*")
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w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID")
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// Return early if it's CORS preflight.
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if "OPTIONS" == r.Method {
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return
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}
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sh.handle(sh.BrokerContext, w, r)
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}
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// Proxies may poll for client offers concurrently.
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@ -69,12 +76,14 @@ func (ctx *BrokerContext) RequestOffer(id string) []byte {
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return offer
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}
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// goroutine which match proxies to clients.
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// goroutine which matches clients to proxies and sends SDP offers along.
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// Safely processes proxy requests, responding to them with either an available
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// client offer or nil on timeout / none are available.
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func (ctx *BrokerContext) Broker() {
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for request := range ctx.proxyPolls {
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snowflake := ctx.AddSnowflake(request.id)
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// defer heap.Remove(ctx.snowflakes, snowflake.index)
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// defer delete(ctx.idToSnowflake, snowflake.id)
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// Wait for a client to avail an offer to the snowflake.
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go func(request *ProxyPoll) {
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select {
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@ -83,8 +92,9 @@ func (ctx *BrokerContext) Broker() {
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request.offerChannel <- offer
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case <-time.After(time.Second * ProxyTimeout):
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// This snowflake is no longer available to serve clients.
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// TODO: Fix race using a delete channel
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heap.Remove(ctx.snowflakes, snowflake.index)
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delete(ctx.snowflakeMap, snowflake.id)
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delete(ctx.idToSnowflake, snowflake.id)
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request.offerChannel <- nil
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}
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}(request)
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@ -99,82 +109,14 @@ func (ctx *BrokerContext) AddSnowflake(id string) *Snowflake {
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snowflake.offerChannel = make(chan []byte)
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snowflake.answerChannel = make(chan []byte)
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heap.Push(ctx.snowflakes, snowflake)
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ctx.snowflakeMap[id] = snowflake
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ctx.idToSnowflake[id] = snowflake
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return snowflake
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}
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func robotsTxtHandler(w http.ResponseWriter, r *http.Request) {
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w.Header().Set("Content-Type", "text/plain; charset=utf-8")
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w.Write([]byte("User-agent: *\nDisallow:\n"))
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}
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func ipHandler(w http.ResponseWriter, r *http.Request) {
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remoteAddr := r.RemoteAddr
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if net.ParseIP(remoteAddr).To4() == nil {
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remoteAddr = "[" + remoteAddr + "]"
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}
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w.Header().Set("Content-Type", "text/plain; charset=utf-8")
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w.Write([]byte(remoteAddr))
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}
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// Return early if it's CORS preflight.
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func isPreflight(w http.ResponseWriter, r *http.Request) bool {
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w.Header().Set("Access-Control-Allow-Origin", "*")
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w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID")
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if "OPTIONS" == r.Method {
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return true
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}
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return false
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}
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/*
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Expects a WebRTC SDP offer in the Request to give to an assigned
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snowflake proxy, which responds with the SDP answer to be sent in
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the HTTP response back to the client.
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*/
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func clientHandler(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
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offer, err := ioutil.ReadAll(r.Body)
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if nil != err {
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log.Println("Invalid data.")
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w.WriteHeader(http.StatusBadRequest)
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return
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}
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w.Header().Set("Access-Control-Allow-Origin", "*")
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w.Header().Set("Access-Control-Allow-Headers", "X-Session-ID")
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// Find the most available snowflake proxy, and pass the offer to it.
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// TODO: Needs improvement - maybe shouldn't immediately fail?
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if ctx.snowflakes.Len() <= 0 {
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log.Println("Client: No snowflake proxies available.")
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w.WriteHeader(http.StatusServiceUnavailable)
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return
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}
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snowflake := heap.Pop(ctx.snowflakes).(*Snowflake)
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snowflake.offerChannel <- offer
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// Wait for the answer to be returned on the channel.
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select {
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case answer := <-snowflake.answerChannel:
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log.Println("Client: Retrieving answer")
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w.Write(answer)
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case <-time.After(time.Second * ClientTimeout):
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log.Println("Client: Timed out.")
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w.WriteHeader(http.StatusGatewayTimeout)
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w.Write([]byte("timed out waiting for answer!"))
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}
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// Remove from the snowflake map whether answer was sent or not, because
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// this client request is now over.
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delete(ctx.snowflakeMap, snowflake.id)
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}
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/*
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For snowflake proxies to request a client from the Broker.
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*/
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func proxyHandler(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
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if isPreflight(w, r) {
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return
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}
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func proxyPolls(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
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id := r.Header.Get("X-Session-ID")
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body, err := ioutil.ReadAll(r.Body)
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if nil != err {
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@ -197,20 +139,54 @@ func proxyHandler(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
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w.Write(offer)
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}
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/*
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Expects a WebRTC SDP offer in the Request to give to an assigned
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snowflake proxy, which responds with the SDP answer to be sent in
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the HTTP response back to the client.
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*/
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func clientOffers(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
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offer, err := ioutil.ReadAll(r.Body)
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if nil != err {
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log.Println("Invalid data.")
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w.WriteHeader(http.StatusBadRequest)
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return
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}
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// Find the most available snowflake proxy, and pass the offer to it.
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// TODO: Needs improvement - maybe shouldn't immediately fail?
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if ctx.snowflakes.Len() <= 0 {
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log.Println("Client: No snowflake proxies available.")
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w.WriteHeader(http.StatusServiceUnavailable)
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return
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}
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snowflake := heap.Pop(ctx.snowflakes).(*Snowflake)
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defer delete(ctx.idToSnowflake, snowflake.id)
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snowflake.offerChannel <- offer
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// Wait for the answer to be returned on the channel.
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select {
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case answer := <-snowflake.answerChannel:
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log.Println("Client: Retrieving answer")
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w.Write(answer)
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case <-time.After(time.Second * ClientTimeout):
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log.Println("Client: Timed out.")
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w.WriteHeader(http.StatusGatewayTimeout)
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w.Write([]byte("timed out waiting for answer!"))
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}
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}
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/*
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Expects snowflake proxes which have previously successfully received
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an offer from proxyHandler to respond with an answer in an HTTP POST,
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which the broker will pass back to the original client.
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*/
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func answerHandler(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
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if isPreflight(w, r) {
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return
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}
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func proxyAnswers(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
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id := r.Header.Get("X-Session-ID")
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snowflake, ok := ctx.snowflakeMap[id]
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snowflake, ok := ctx.idToSnowflake[id]
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if !ok || nil == snowflake {
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// The snowflake took too long to respond with an answer,
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// and the designated client is no longer around / recognized by the Broker.
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// The snowflake took too long to respond with an answer, so its client
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// disappeared / the snowflake is no longer recognized by the Broker.
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w.WriteHeader(http.StatusGone)
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return
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}
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@ -229,6 +205,20 @@ func debugHandler(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
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w.Write([]byte(s))
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}
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func robotsTxtHandler(w http.ResponseWriter, r *http.Request) {
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w.Header().Set("Content-Type", "text/plain; charset=utf-8")
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w.Write([]byte("User-agent: *\nDisallow:\n"))
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}
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func ipHandler(w http.ResponseWriter, r *http.Request) {
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remoteAddr := r.RemoteAddr
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if net.ParseIP(remoteAddr).To4() == nil {
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remoteAddr = "[" + remoteAddr + "]"
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}
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w.Header().Set("Content-Type", "text/plain; charset=utf-8")
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w.Write([]byte(remoteAddr))
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}
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func init() {
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ctx := NewBrokerContext()
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@ -237,8 +227,8 @@ func init() {
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http.HandleFunc("/robots.txt", robotsTxtHandler)
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http.HandleFunc("/ip", ipHandler)
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http.Handle("/client", SnowflakeHandler{ctx, clientHandler})
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http.Handle("/proxy", SnowflakeHandler{ctx, proxyHandler})
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http.Handle("/answer", SnowflakeHandler{ctx, answerHandler})
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http.Handle("/proxy", SnowflakeHandler{ctx, proxyPolls})
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http.Handle("/client", SnowflakeHandler{ctx, clientOffers})
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http.Handle("/answer", SnowflakeHandler{ctx, proxyAnswers})
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http.Handle("/debug", SnowflakeHandler{ctx, debugHandler})
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}
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