tailcfg, controlclient, magicsock: request IPv6 endpoints, but ignore them

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/direct.go

@@ -448,12 +448,13 @@ func (c *Direct) PollNetMap(ctx context.Context, maxPolls int, cb func(*NetworkM
 	c.logf("PollNetMap: stream=%v :%v %v\n", maxPolls, localPort, ep)
 
 	request := tailcfg.MapRequest{
-		Version:   4,
-		KeepAlive: c.keepAlive,
-		NodeKey:   tailcfg.NodeKey(persist.PrivateNodeKey.Public()),
-		Endpoints: ep,
-		Stream:    allowStream,
-		Hostinfo:  hostinfo,
+		Version:     4,
+		IncludeIPv6: true,
+		KeepAlive:   c.keepAlive,
+		NodeKey:     tailcfg.NodeKey(persist.PrivateNodeKey.Public()),
+		Endpoints:   ep,
+		Stream:      allowStream,
+		Hostinfo:    hostinfo,
 	}
 	if c.newDecompressor != nil {
 		request.Compress = "zstd"

tailcfg/tailcfg.go

@@ -391,13 +391,14 @@ type RegisterResponse struct {
 // using the local machine key, and sent to:
 //	https://login.tailscale.com/machine/<mkey hex>/map
 type MapRequest struct {
-	Version   int    // current version is 4
-	Compress  string // "zstd" or "" (no compression)
-	KeepAlive bool   // server sends keep-alives
-	NodeKey   NodeKey
-	Endpoints []string
-	Stream    bool // if true, multiple MapResponse objects are returned
-	Hostinfo  *Hostinfo
+	Version     int    // current version is 4
+	Compress    string // "zstd" or "" (no compression)
+	KeepAlive   bool   // server sends keep-alives
+	NodeKey     NodeKey
+	Endpoints   []string // caller's endpoints (IPv4 or IPv6)
+	IncludeIPv6 bool     // include IPv6 endpoints in returned Node Endpoints
+	Stream      bool     // if true, multiple MapResponse objects are returned
+	Hostinfo    *Hostinfo
 }
 
 type MapResponse struct {

wgengine/magicsock/magicsock.go

@@ -1456,6 +1456,10 @@ func (c *Conn) CreateEndpoint(key [32]byte, addrs string) (conn.Endpoint, error)
 			}
 			if ip4 := addr.IP.To4(); ip4 != nil {
 				addr.IP = ip4
+			} else {
+				// TODO(bradfitz): stop skipping IPv6 ones for now.
+				c.logf("magicsock: CreateEndpoint: ignoring IPv6 addr %v for now", addr)
+				continue
 			}
 			a.addrs = append(a.addrs, *addr)
 		}