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

Breaks something deep in wireguard or magicsock's brainstem, no packets at all
can flow. All received packets fail decryption with "invalid mac1".

This reverts commit 94024355edd563473345e28f9d441e46fd14c70f.

Signed-off-by: David Anderson <dave@natulte.net>

control/controlclient/direct.go

@@ -449,7 +449,6 @@ 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

@@ -395,8 +395,7 @@ type MapRequest struct {
 	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
+	Endpoints []string
 	Stream    bool // if true, multiple MapResponse objects are returned
 	Hostinfo  *Hostinfo
 }

wgengine/magicsock/magicsock.go

@@ -1456,10 +1456,6 @@ 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)
 		}