add an AddrVerified field to the ClientHelloInfo (#4360)

* add an AddressVerified field to the ClientHelloInfo

* rename ClientHelloInfo.AddressVerififed to ClientHelloInfo.AddrVerififed

interface.go

@@ -333,8 +333,15 @@ type Config struct {
 	Tracer          func(context.Context, logging.Perspective, ConnectionID) *logging.ConnectionTracer
 }
 
+// ClientHelloInfo contains information about an incoming connection attempt.
 type ClientHelloInfo struct {
+	// RemoteAddr is the remote address on the Initial packet.
+	// Unless AddrVerified is set, the address is not yet verified, and could be a spoofed IP address.
 	RemoteAddr net.Addr
+	// AddrVerified says if the remote address was verified using QUIC's Retry mechanism.
+	// Note that the Retry mechanism costs one network roundtrip,
+	// and is not performed unless Transport.MaxUnvalidatedHandshakes is surpassed.
+	AddrVerified bool
 }
 
 // ConnectionState records basic details about a QUIC connection