Update dependencies

vendor/tailscale.com/derp/derp.go

@@ -18,6 +18,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"net"
 	"time"
 )
 
@@ -79,8 +80,7 @@ const (
 	// framePeerGone to B so B can forget that a reverse path
 	// exists on that connection to get back to A. It is also sent
 	// if A tries to send a CallMeMaybe to B and the server has no
-	// record of B (which currently would only happen if there was
-	// a bug).
+	// record of B
 	framePeerGone = frameType(0x08) // 32B pub key of peer that's gone + 1 byte reason
 
 	// framePeerPresent is like framePeerGone, but for other members of the DERP
@@ -131,8 +131,8 @@ const (
 type PeerGoneReasonType byte
 
 const (
-	PeerGoneReasonDisconnected  = PeerGoneReasonType(0x00) // peer disconnected from this server
-	PeerGoneReasonNotHere       = PeerGoneReasonType(0x01) // server doesn't know about this peer, unexpected
+	PeerGoneReasonDisconnected  = PeerGoneReasonType(0x00) // is only sent when a peer disconnects from this server
+	PeerGoneReasonNotHere       = PeerGoneReasonType(0x01) // server doesn't know about this peer
 	PeerGoneReasonMeshConnBroke = PeerGoneReasonType(0xf0) // invented by Client.RunWatchConnectionLoop on disconnect; not sent on the wire
 )
 
@@ -147,6 +147,7 @@ const (
 	PeerPresentIsRegular  = 1 << 0
 	PeerPresentIsMeshPeer = 1 << 1
 	PeerPresentIsProber   = 1 << 2
+	PeerPresentNotIdeal   = 1 << 3 // client said derp server is not its Region.Nodes[0] ideal node
 )
 
 var bin = binary.BigEndian
@@ -254,3 +255,14 @@ func writeFrame(bw *bufio.Writer, t frameType, b []byte) error {
 	}
 	return bw.Flush()
 }
+
+// Conn is the subset of the underlying net.Conn the DERP Server needs.
+// It is a defined type so that non-net connections can be used.
+type Conn interface {
+	io.WriteCloser
+	LocalAddr() net.Addr
+	// The *Deadline methods follow the semantics of net.Conn.
+	SetDeadline(time.Time) error
+	SetReadDeadline(time.Time) error
+	SetWriteDeadline(time.Time) error
+}