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

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

control/controlclient/direct.go

@@ -449,6 +449,7 @@ func (c *Direct) PollNetMap(ctx context.Context, maxPolls int, cb func(*NetworkM
 
 	request := tailcfg.MapRequest{
 		Version:     4,
+		IncludeIPv6: true,
 		KeepAlive:   c.keepAlive,
 		NodeKey:     tailcfg.NodeKey(persist.PrivateNodeKey.Public()),
 		Endpoints:   ep,

tailcfg/tailcfg.go

@@ -395,7 +395,8 @@ type MapRequest struct {
 	Compress    string // "zstd" or "" (no compression)
 	KeepAlive   bool   // server sends keep-alives
 	NodeKey     NodeKey
-	Endpoints []string
+	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
 }

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)
 		}