🧮 conn: unify socket control message buffer size calculation

Always use the maximum possible size.

Author: database64128

conn/cmsg_darwin.go

@@ -9,7 +9,7 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-const socketControlMessageBufferSize = unix.SizeofCmsghdr + alignedSizeofInet6Pktinfo
+const socketControlMessageBufferSize = unix.SizeofCmsghdr + max(alignedSizeofInet4Pktinfo, alignedSizeofInet6Pktinfo)
 
 const cmsgAlignTo = 4
 

conn/cmsg_linux.go

@@ -9,8 +9,9 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-const socketControlMessageBufferSize = unix.SizeofCmsghdr + alignedSizeofInet6Pktinfo +
-	unix.SizeofCmsghdr + alignedSizeofGROSegmentSize
+const socketControlMessageBufferSize = unix.SizeofCmsghdr + max(alignedSizeofInet4Pktinfo, alignedSizeofInet6Pktinfo) +
+	unix.SizeofCmsghdr + max(alignedSizeofSockaddrInet4, alignedSizeofSockaddrInet6) +
+	unix.SizeofCmsghdr + max(alignedSizeofGSOSegmentSize, alignedSizeofGROSegmentSize)
 
 const (
 	sizeofGSOSegmentSize = 2 // int(unsafe.Sizeof(uint16(0)))
@@ -89,6 +90,8 @@ func parseSocketControlMessage(cmsg []byte) (m SocketControlMessage, err error)
 const (
 	alignedSizeofInet4Pktinfo   = (unix.SizeofInet4Pktinfo + unix.SizeofPtr - 1) & ^(unix.SizeofPtr - 1)
 	alignedSizeofInet6Pktinfo   = (unix.SizeofInet6Pktinfo + unix.SizeofPtr - 1) & ^(unix.SizeofPtr - 1)
+	alignedSizeofSockaddrInet4  = (unix.SizeofSockaddrInet4 + unix.SizeofPtr - 1) & ^(unix.SizeofPtr - 1)
+	alignedSizeofSockaddrInet6  = (unix.SizeofSockaddrInet6 + unix.SizeofPtr - 1) & ^(unix.SizeofPtr - 1)
 	alignedSizeofGSOSegmentSize = (sizeofGSOSegmentSize + unix.SizeofPtr - 1) & ^(unix.SizeofPtr - 1)
 	alignedSizeofGROSegmentSize = (sizeofGROSegmentSize + unix.SizeofPtr - 1) & ^(unix.SizeofPtr - 1)
 )

conn/cmsg_windows.go

@@ -9,8 +9,8 @@ import (
 	"golang.org/x/sys/windows"
 )
 
-const socketControlMessageBufferSize = sizeofCmsghdr + alignedSizeofInet6Pktinfo +
-	sizeofCmsghdr + alignedSizeofCoalescedInfo
+const socketControlMessageBufferSize = sizeofCmsghdr + max(alignedSizeofInet4Pktinfo, alignedSizeofInet6Pktinfo) +
+	sizeofCmsghdr + max(alignedSizeofSendMsgSize, alignedSizeofCoalescedInfo)
 
 const (
 	sizeofPtr           = int(unsafe.Sizeof(uintptr(0)))

conn/conn_linux.go

@@ -6,9 +6,6 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// TransparentSocketControlMessageBufferSize specifies the buffer size for receiving IPV6_RECVORIGDSTADDR socket control messages.
-const TransparentSocketControlMessageBufferSize = unix.SizeofCmsghdr + (unix.SizeofSockaddrInet6+unix.SizeofPtr-1) & ^(unix.SizeofPtr-1)
-
 func setSendBufferSize(fd, size int) error {
 	if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_SNDBUF, size); err != nil {
 		return fmt.Errorf("failed to set socket option SO_SNDBUF: %w", err)

service/udp_transparent_linux.go

@@ -164,7 +164,7 @@ func (s *UDPTransparentRelay) recvFromServerConnRecvmmsg(ctx context.Context, ln
 	msgvec := make([]conn.Mmsghdr, n)
 
 	for i := range msgvec {
-		cmsgBuf := make([]byte, conn.TransparentSocketControlMessageBufferSize)
+		cmsgBuf := make([]byte, conn.SocketControlMessageBufferSize)
 		cmsgvec[i] = cmsgBuf
 		msgvec[i].Msghdr.Name = (*byte)(unsafe.Pointer(&namevec[i]))
 		msgvec[i].Msghdr.Namelen = unix.SizeofSockaddrInet6
@@ -187,7 +187,7 @@ func (s *UDPTransparentRelay) recvFromServerConnRecvmmsg(ctx context.Context, ln
 			qpvec[i] = queuedPacket
 			iovec[i].Base = &queuedPacket.buf[s.packetBufFrontHeadroom]
 			iovec[i].SetLen(s.packetBufRecvSize)
-			msgvec[i].Msghdr.SetControllen(conn.TransparentSocketControlMessageBufferSize)
+			msgvec[i].Msghdr.SetControllen(conn.SocketControlMessageBufferSize)
 		}
 
 		n, err = serverConn.ReadMsgs(msgvec, 0)