Add support for kTLS

Reference: https://gitlab.com/go-extension/tls

common/ktls/ktls_write.go

@@ -0,0 +1,154 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux && go1.25 && !without_badtls
+
+package ktls
+
+import (
+	"crypto/cipher"
+	"crypto/tls"
+	"errors"
+	"net"
+)
+
+func (c *Conn) Write(b []byte) (int, error) {
+	if !c.kernelTx {
+		return c.Conn.Write(b)
+	}
+	// interlock with Close below
+	for {
+		x := c.rawConn.ActiveCall.Load()
+		if x&1 != 0 {
+			return 0, net.ErrClosed
+		}
+		if c.rawConn.ActiveCall.CompareAndSwap(x, x+2) {
+			break
+		}
+	}
+	defer c.rawConn.ActiveCall.Add(-2)
+
+	//if err := c.Conn.HandshakeContext(context.Background()); err != nil {
+	//	return 0, err
+	//}
+
+	c.rawConn.Out.Lock()
+	defer c.rawConn.Out.Unlock()
+
+	if err := *c.rawConn.Out.Err; err != nil {
+		return 0, err
+	}
+
+	if !c.rawConn.IsHandshakeComplete.Load() {
+		return 0, tls.AlertError(alertInternalError)
+	}
+
+	if *c.rawConn.CloseNotifySent {
+		// return 0, errShutdown
+		return 0, errors.New("tls: protocol is shutdown")
+	}
+
+	// TLS 1.0 is susceptible to a chosen-plaintext
+	// attack when using block mode ciphers due to predictable IVs.
+	// This can be prevented by splitting each Application Data
+	// record into two records, effectively randomizing the RawIV.
+	//
+	// https://www.openssl.org/~bodo/tls-cbc.txt
+	// https://bugzilla.mozilla.org/show_bug.cgi?id=665814
+	// https://www.imperialviolet.org/2012/01/15/beastfollowup.html
+
+	var m int
+	if len(b) > 1 && *c.rawConn.Vers == tls.VersionTLS10 {
+		if _, ok := (*c.rawConn.Out.Cipher).(cipher.BlockMode); ok {
+			n, err := c.writeRecordLocked(recordTypeApplicationData, b[:1])
+			if err != nil {
+				return n, c.rawConn.Out.SetErrorLocked(err)
+			}
+			m, b = 1, b[1:]
+		}
+	}
+
+	n, err := c.writeRecordLocked(recordTypeApplicationData, b)
+	return n + m, c.rawConn.Out.SetErrorLocked(err)
+}
+
+func (c *Conn) writeRecordLocked(typ uint16, data []byte) (n int, err error) {
+	if !c.kernelTx {
+		return c.rawConn.WriteRecordLocked(typ, data)
+	}
+	/*for len(data) > 0 {
+		m := len(data)
+		if maxPayload := c.maxPayloadSizeForWrite(typ); m > maxPayload {
+			m = maxPayload
+		}
+		_, err = c.writeKernelRecord(typ, data[:m])
+		if err != nil {
+			return
+		}
+		n += m
+		data = data[m:]
+	}*/
+	return c.writeKernelRecord(typ, data)
+}
+
+const (
+	// tcpMSSEstimate is a conservative estimate of the TCP maximum segment
+	// size (MSS). A constant is used, rather than querying the kernel for
+	// the actual MSS, to avoid complexity. The value here is the IPv6
+	// minimum MTU (1280 bytes) minus the overhead of an IPv6 header (40
+	// bytes) and a TCP header with timestamps (32 bytes).
+	tcpMSSEstimate = 1208
+
+	// recordSizeBoostThreshold is the number of bytes of application data
+	// sent after which the TLS record size will be increased to the
+	// maximum.
+	recordSizeBoostThreshold = 128 * 1024
+)
+
+func (c *Conn) maxPayloadSizeForWrite(typ uint16) int {
+	if /*c.config.DynamicRecordSizingDisabled ||*/ typ != recordTypeApplicationData {
+		return maxPlaintext
+	}
+
+	if *c.rawConn.PacketsSent >= recordSizeBoostThreshold {
+		return maxPlaintext
+	}
+
+	// Subtract TLS overheads to get the maximum payload size.
+	payloadBytes := tcpMSSEstimate - recordHeaderLen - c.rawConn.Out.ExplicitNonceLen()
+	if rawCipher := *c.rawConn.Out.Cipher; rawCipher != nil {
+		switch ciph := rawCipher.(type) {
+		case cipher.Stream:
+			payloadBytes -= (*c.rawConn.Out.Mac).Size()
+		case cipher.AEAD:
+			payloadBytes -= ciph.Overhead()
+		/*case cbcMode:
+		blockSize := ciph.BlockSize()
+		// The payload must fit in a multiple of blockSize, with
+		// room for at least one padding byte.
+		payloadBytes = (payloadBytes & ^(blockSize - 1)) - 1
+		// The RawMac is appended before padding so affects the
+		// payload size directly.
+		payloadBytes -= c.out.mac.Size()*/
+		default:
+			panic("unknown cipher type")
+		}
+	}
+	if *c.rawConn.Vers == tls.VersionTLS13 {
+		payloadBytes-- // encrypted ContentType
+	}
+
+	// Allow packet growth in arithmetic progression up to max.
+	pkt := *c.rawConn.PacketsSent
+	*c.rawConn.PacketsSent++
+	if pkt > 1000 {
+		return maxPlaintext // avoid overflow in multiply below
+	}
+
+	n := payloadBytes * int(pkt+1)
+	if n > maxPlaintext {
+		n = maxPlaintext
+	}
+	return n
+}