probing

ipn/ipnlocal/local.go

@@ -5920,19 +5920,24 @@ func (b *LocalBackend) SuggestExitNode() (*tailcfg.StableNodeID, error) {
 		return nil, errors.New("no netmap")
 	}
 	peers := netMap.Peers
-	lastReport := b.MagicConn().GetLastNetcheckReport()
+	lastReport := b.MagicConn().GetLastNetcheckReport(b.ctx)
 	var fastestRegionLatency = time.Duration(math.MaxInt64)
 	var preferredExitNodeID tailcfg.StableNodeID
 	peerRegionMap := make(map[int][]tailcfg.NodeView)
+	b.logf("preferred self node derp %v", lastReport.PreferredDERP)
+	b.logf("preferred self node derp name %v", netMap.DERPMap.Regions[lastReport.PreferredDERP])
+	var mullvadCandidates []*tailcfg.NodeView
 	for _, peer := range peers {
 		if online := peer.Online(); online != nil && !*online {
 			continue
 		}
-		if peer.Hostinfo().Location() != nil {
-			b.logf("location %v %v", peer.Hostinfo().Location().Longitude, peer.Hostinfo().Location().Latitude)
-		}
 		if tsaddr.ContainsExitRoutes(peer.AllowedIPs()) {
 			ipp, _ := netip.ParseAddrPort(peer.DERP())
+			if peer.DERP() == "" {
+				if peer.Hostinfo().Location().Country == "USA" {
+					mullvadCandidates = append(mullvadCandidates, &peer)
+				}
+			}
 			regionID := int(ipp.Port())
 			regionLatency, ok := lastReport.RegionLatency[regionID]
 			peerRegionMap[regionID] = append(peerRegionMap[regionID], peer)
@@ -5948,6 +5953,8 @@ func (b *LocalBackend) SuggestExitNode() (*tailcfg.StableNodeID, error) {
 		}
 	}
 	b.logf("self derp %v", b.netMap.SelfNode.DERP())
+	result := b.MagicConn().MeasureNodeICMPLatency(b.ctx, mullvadCandidates)
+	b.logf("result %v", result)
 	ipp, _ := netip.ParseAddrPort(netMap.SelfNode.DERP())
 	selfDerpRegionID := int(ipp.Port())
 	b.logf("self derp region id %v", selfDerpRegionID)

net/netcheck/netcheck.go

@@ -1730,3 +1730,48 @@ func conciseOptBool(b opt.Bool, trueVal string) string {
 	metricSTUNRecv6 = clientmetric.NewCounter("netcheck_stun_recv_ipv6")
 	metricHTTPSend  = clientmetric.NewCounter("netcheck_https_measure")
 )
+
+func (c *Client) MeasureICMPLatency(ctx context.Context, candidates []*tailcfg.NodeView) map[*tailcfg.NodeView]time.Duration {
+	p := ping.New(ctx, c.logf, netns.Listener(c.logf, c.NetMon))
+	defer p.Close()
+	var wg sync.WaitGroup
+	var results map[*tailcfg.NodeView]time.Duration
+	wg.Add(len(candidates))
+	for _, candidate := range candidates {
+		go func(candidate *tailcfg.NodeView) {
+			defer wg.Done()
+			if d, err := c.measureNodeICMPLatency(ctx, candidate, p); err != nil {
+				c.logf("error %v node %v", err, candidate.Name())
+			} else {
+				results[candidate] = d
+				c.logf("results %v", results)
+			}
+		}(candidate)
+	}
+
+	wg.Wait()
+	return results
+}
+
+func (c *Client) measureNodeICMPLatency(ctx context.Context, node *tailcfg.NodeView, p *ping.Pinger) (time.Duration, error) {
+	// Get the IPAddr by asking for the UDP address that we would use for
+	// STUN and then using that IP.
+	//
+	// TODO(andrew-d): this is a bit ugly
+	var nodeAddr netip.Addr
+	for i := range node.Addresses().LenIter() {
+		p := node.Addresses().At(i)
+		if p.Addr().Is4() {
+			nodeAddr = p.Addr()
+			break
+		}
+	}
+
+	addr := &net.IPAddr{
+		IP:   net.IP(nodeAddr.AsSlice()),
+		Zone: nodeAddr.Zone(),
+	}
+	// Use the unique node.Name field as the packet data to reduce the
+	// likelihood that we get a mismatched echo response.
+	return p.Send(ctx, addr, []byte(node.Name()))
+}

wgengine/magicsock/magicsock.go

@@ -3009,7 +3009,15 @@ func getPeerMTUsProbedMetric(mtu tstun.WireMTU) *clientmetric.Metric {
 	return mm
 }
 
-func (c *Conn) GetLastNetcheckReport() *netcheck.Report {
-	report, _ := c.updateNetInfo(c.connCtx)
-	return report
+func (c *Conn) GetLastNetcheckReport(ctx context.Context) *netcheck.Report {
+	nr, err := c.updateNetInfo(ctx)
+	if err != nil {
+		c.logf("magicsock.Conn.determineEndpoints: updateNetInfo: %v", err)
+		return nil
+	}
+	return nr
+}
+
+func (c *Conn) MeasureNodeICMPLatency(ctx context.Context, candidates []*tailcfg.NodeView) map[*tailcfg.NodeView]time.Duration {
+	return c.netChecker.MeasureICMPLatency(ctx, candidates)
 }