crypto/tls: add QUICConfig.ClientHelloInfoConn

Fixes #77363.

Change-Id: I28ec5cdd16e96bae13f495a904006845dfbf3a2e
Reviewed-on: https://go-review.googlesource.com/c/go/+/745720
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>

handshake_server.go

@@ -1007,6 +1007,10 @@ func clientHelloInfo(ctx context.Context, c *Conn, clientHello *clientHelloMsg)
 		supportedVersions = supportedVersionsFromMax(clientHello.vers)
 	}
 
+	conn := c.conn
+	if c.quic != nil {
+		conn = c.quic.clientHelloInfoConn
+	}
 	return &ClientHelloInfo{
 		CipherSuites:      clientHello.cipherSuites,
 		ServerName:        clientHello.serverName,
@@ -1016,7 +1020,7 @@ func clientHelloInfo(ctx context.Context, c *Conn, clientHello *clientHelloMsg)
 		SupportedProtos:   clientHello.alpnProtocols,
 		SupportedVersions: supportedVersions,
 		Extensions:        clientHello.extensions,
-		Conn:              c.conn,
+		Conn:              conn,
 		HelloRetryRequest: c.didHRR,
 		config:            c.config,
 		ctx:               ctx,

quic.go

@@ -8,6 +8,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"net"
 )
 
 // QUICEncryptionLevel represents a QUIC encryption level used to transmit
@@ -56,6 +57,9 @@ type QUICConfig struct {
 	// stored in the client session cache.
 	// The application should use [QUICConn.StoreSession] to store sessions.
 	EnableSessionEvents bool
+
+	// ClientHelloInfoConn is the net.Conn to use for the ClientHelloInfo.Conn field.
+	ClientHelloInfoConn net.Conn
 }
 
 // A QUICEventKind is a type of operation on a QUIC connection.
@@ -176,6 +180,7 @@ type quicState struct {
 	transportParams []byte // to send to the peer
 
 	enableSessionEvents bool
+	clientHelloInfoConn net.Conn
 }
 
 // QUICClient returns a new TLS client side connection using QUICTransport as the
@@ -200,6 +205,7 @@ func newQUICConn(conn *Conn, config *QUICConfig) *QUICConn {
 		signalc:             make(chan struct{}),
 		blockedc:            make(chan struct{}),
 		enableSessionEvents: config.EnableSessionEvents,
+		clientHelloInfoConn: config.ClientHelloInfoConn,
 	}
 	conn.quic.events = conn.quic.eventArr[:0]
 	return &QUICConn{