Add separate client for dynamic relays (fixes #2368)

Did some manual tests in the playground, such as kicking off two clients in parallel, first connecting,
second one getting a message about already being connected, falling back to the second address.

lib/relay/relay.go

@@ -8,15 +8,13 @@ package relay
 
 import (
 	"crypto/tls"
-	"encoding/json"
-	"net/http"
+
 	"net/url"
 	"sort"
 	"time"
 
 	"github.com/syncthing/syncthing/lib/config"
 	"github.com/syncthing/syncthing/lib/events"
-	"github.com/syncthing/syncthing/lib/osutil"
 	"github.com/syncthing/syncthing/lib/relay/client"
 	"github.com/syncthing/syncthing/lib/relay/protocol"
 	"github.com/syncthing/syncthing/lib/sync"
@@ -34,7 +32,7 @@ type Svc struct {
 	tlsCfg *tls.Config
 
 	tokens      map[string]suture.ServiceToken
-	clients     map[string]*client.ProtocolClient
+	clients     map[string]client.RelayClient
 	mut         sync.RWMutex
 	invitations chan protocol.SessionInvitation
 	conns       chan *tls.Conn
@@ -56,7 +54,7 @@ func NewSvc(cfg *config.Wrapper, tlsCfg *tls.Config) *Svc {
 		tlsCfg: tlsCfg,
 
 		tokens:      make(map[string]suture.ServiceToken),
-		clients:     make(map[string]*client.ProtocolClient),
+		clients:     make(map[string]client.RelayClient),
 		mut:         sync.NewRWMutex(),
 		invitations: make(chan protocol.SessionInvitation),
 		conns:       conns,
@@ -106,61 +104,17 @@ func (s *Svc) CommitConfiguration(from, to config.Configuration) bool {
 		existing[uri.String()] = uri
 	}
 
-	// Query dynamic addresses, and pick the closest relay from the ones they provide.
-	for key, uri := range existing {
-		if uri.Scheme != "dynamic+http" && uri.Scheme != "dynamic+https" {
-			continue
-		}
-		delete(existing, key)
-
-		// Trim off the `dynamic+` prefix
-		uri.Scheme = uri.Scheme[8:]
-
-		l.Debugln("Looking up dynamic relays from", uri)
-
-		data, err := http.Get(uri.String())
-		if err != nil {
-			l.Debugln("Failed to lookup dynamic relays", err)
-			continue
-		}
-
-		var ann dynamicAnnouncement
-		err = json.NewDecoder(data.Body).Decode(&ann)
-		data.Body.Close()
-		if err != nil {
-			l.Debugln("Failed to lookup dynamic relays", err)
-			continue
-		}
-
-		var dynRelayAddrs []string
-		for _, relayAnn := range ann.Relays {
-			ruri, err := url.Parse(relayAnn.URL)
-			if err != nil {
-				l.Debugln("Failed to parse dynamic relay address", relayAnn.URL, err)
-				continue
-			}
-			l.Debugln("Found", ruri, "via", uri)
-			dynRelayAddrs = append(dynRelayAddrs, ruri.String())
-		}
-
-		if len(dynRelayAddrs) > 0 {
-			dynRelayAddrs = relayAddressesSortedByLatency(dynRelayAddrs)
-			closestRelay := dynRelayAddrs[0]
-			l.Debugln("Picking", closestRelay, "as closest dynamic relay from", uri)
-			ruri, _ := url.Parse(closestRelay)
-			existing[closestRelay] = ruri
-		} else {
-			l.Debugln("No dynamic relay found on", uri)
-		}
-	}
-
 	s.mut.Lock()
 
 	for key, uri := range existing {
 		_, ok := s.tokens[key]
 		if !ok {
 			l.Debugln("Connecting to relay", uri)
-			c := client.NewProtocolClient(uri, s.tlsCfg.Certificates, s.invitations)
+			c, err := client.NewClient(uri, s.tlsCfg.Certificates, s.invitations)
+			if err != nil {
+				l.Debugln("Failed to connect to relay", uri, err)
+				continue
+			}
 			s.tokens[key] = s.Add(c)
 			s.clients[key] = c
 		}
@@ -197,8 +151,8 @@ func (s *Svc) Relays() []string {
 
 	s.mut.RLock()
 	relays := make([]string, 0, len(s.clients))
-	for uri := range s.clients {
-		relays = append(relays, uri)
+	for _, client := range s.clients {
+		relays = append(relays, client.URI().String())
 	}
 	s.mut.RUnlock()
 
@@ -216,14 +170,14 @@ func (s *Svc) RelayStatus(uri string) (time.Duration, bool) {
 	}
 
 	s.mut.RLock()
-	client, ok := s.clients[uri]
+	for _, client := range s.clients {
+		if client.URI().String() == uri {
+			return client.Latency(), client.StatusOK()
+		}
+	}
 	s.mut.RUnlock()
 
-	if !ok || !client.StatusOK() {
-		return time.Hour, false
-	}
-
-	return client.Latency(), true
+	return time.Hour, false
 }
 
 // Accept returns a new *tls.Conn. The connection is already handshaken.
@@ -277,7 +231,7 @@ func (r *invitationReceiver) Stop() {
 // The eventBroadcaster sends a RelayStateChanged event when the relay status
 // changes. We need this somewhat ugly polling mechanism as there's currently
 // no way to get the event feed directly from the relay lib. This may be
-// somethign to revisit later, possibly.
+// something to revisit later, possibly.
 type eventBroadcaster struct {
 	svc  *Svc
 	stop chan struct{}
@@ -322,51 +276,3 @@ func (e *eventBroadcaster) Serve() {
 func (e *eventBroadcaster) Stop() {
 	close(e.stop)
 }
-
-// This is the announcement recieved from the relay server;
-// {"relays": [{"url": "relay://10.20.30.40:5060"}, ...]}
-type dynamicAnnouncement struct {
-	Relays []struct {
-		URL string
-	}
-}
-
-// relayAddressesSortedByLatency adds local latency to the relay, and sorts them
-// by sum latency, and returns the addresses.
-func relayAddressesSortedByLatency(input []string) []string {
-	relays := make(relayList, len(input))
-	for i, relay := range input {
-		if latency, err := osutil.GetLatencyForURL(relay); err == nil {
-			relays[i] = relayWithLatency{relay, int(latency / time.Millisecond)}
-		} else {
-			relays[i] = relayWithLatency{relay, int(time.Hour / time.Millisecond)}
-		}
-	}
-
-	sort.Sort(relays)
-
-	addresses := make([]string, len(relays))
-	for i, relay := range relays {
-		addresses[i] = relay.relay
-	}
-	return addresses
-}
-
-type relayWithLatency struct {
-	relay   string
-	latency int
-}
-
-type relayList []relayWithLatency
-
-func (l relayList) Len() int {
-	return len(l)
-}
-
-func (l relayList) Less(a, b int) bool {
-	return l[a].latency < l[b].latency
-}
-
-func (l relayList) Swap(a, b int) {
-	l[a], l[b] = l[b], l[a]
-}