Remove useless cached state

Simplify some logic while I'm here.

PiperOrigin-RevId: 351491593

1 files changed, 77 insertions, 146 deletions

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index dcf898c0a..57f224120 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -309,11 +309,6 @@ type socketOpsCommon struct {
 
 	// readMu protects access to the below fields.
 	readMu sync.Mutex `state:"nosave"`
-	// readCM holds control message information for the last packet read
-	// from Endpoint.
-	readCM         socket.IPControlMessages
-	sender         tcpip.FullAddress
-	linkPacketInfo tcpip.LinkPacketInfo
 
 	// sockOptTimestamp corresponds to SO_TIMESTAMP. When true, timestamps
 	// of returned messages can be returned via control messages. When
@@ -368,25 +363,6 @@ func (s *socketOpsCommon) isPacketBased() bool {
 	return s.skType == linux.SOCK_DGRAM || s.skType == linux.SOCK_SEQPACKET || s.skType == linux.SOCK_RDM || s.skType == linux.SOCK_RAW
 }
 
-// Precondition: s.readMu must be held.
-func (s *socketOpsCommon) readLocked(dst io.Writer, count int, peek bool) (numRead, numTotal int, serr *syserr.Error) {
-	res, err := s.Endpoint.Read(dst, count, tcpip.ReadOptions{
-		Peek:               peek,
-		NeedRemoteAddr:     true,
-		NeedLinkPacketInfo: true,
-	})
-
-	// Assign these anyways.
-	s.readCM = socket.NewIPControlMessages(s.family, res.ControlMessages)
-	s.sender = res.RemoteAddr
-	s.linkPacketInfo = res.LinkPacketInfo
-
-	if err != nil {
-		return 0, 0, syserr.TranslateNetstackError(err)
-	}
-	return res.Count, res.Total, nil
-}
-
 // Release implements fs.FileOperations.Release.
 func (s *socketOpsCommon) Release(ctx context.Context) {
 	e, ch := waiter.NewChannelEntry(nil)
@@ -436,11 +412,13 @@ func (s *SocketOperations) WriteTo(ctx context.Context, _ *fs.File, dst io.Write
 	defer s.readMu.Unlock()
 
 	// This may return a blocking error.
-	n, _, err := s.readLocked(dst, int(count), dup /* peek */)
+	res, err := s.Endpoint.Read(dst, int(count), tcpip.ReadOptions{
+		Peek: dup,
+	})
 	if err != nil {
-		return 0, err.ToError()
+		return 0, syserr.TranslateNetstackError(err).ToError()
 	}
-	return int64(n), nil
+	return int64(res.Count), nil
 }
 
 // ioSequencePayload implements tcpip.Payload.
@@ -2557,22 +2535,6 @@ func (s *socketOpsCommon) GetPeerName(t *kernel.Task) (linux.SockAddr, uint32, *
 	return a, l, nil
 }
 
-// streamRead is the fast path for non-blocking, non-peek, stream-based socket.
-//
-// Precondition: s.readMu must be locked.
-func (s *socketOpsCommon) streamRead(ctx context.Context, dst io.Writer, count int) (int, *syserr.Error) {
-	// Always do at least one read, even if the number of bytes to read is 0.
-	var n int
-	n, _, err := s.readLocked(dst, count, false /* peek */)
-	if err != nil {
-		return 0, err
-	}
-	if n > 0 {
-		s.Endpoint.ModerateRecvBuf(n)
-	}
-	return n, nil
-}
-
 func (s *socketOpsCommon) fillCmsgInq(cmsg *socket.ControlMessages) {
 	if !s.sockOptInq {
 		return
@@ -2608,133 +2570,102 @@ func toLinuxPacketType(pktType tcpip.PacketType) uint8 {
 func (s *socketOpsCommon) nonBlockingRead(ctx context.Context, dst usermem.IOSequence, peek, trunc, senderRequested bool) (int, int, linux.SockAddr, uint32, socket.ControlMessages, *syserr.Error) {
 	isPacket := s.isPacketBased()
 
-	// Fast path for regular reads from stream (e.g., TCP) endpoints. Note
-	// that senderRequested is ignored for stream sockets.
-	if !peek && !isPacket {
-		// TCP sockets discard the data if MSG_TRUNC is set.
-		//
-		// This behavior is documented in man 7 tcp:
-		// Since version 2.4, Linux supports the use of MSG_TRUNC in the flags
-		// argument of recv(2) (and recvmsg(2)). This flag causes the received
-		// bytes of data to be discarded, rather than passed back in a
-		// caller-supplied  buffer.
-		s.readMu.Lock()
-
-		var w io.Writer
-		if trunc {
-			w = ioutil.Discard
-		} else {
-			w = dst.Writer(ctx)
-		}
-
-		n, err := s.streamRead(ctx, w, int(dst.NumBytes()))
-
-		if err == nil && !trunc {
-			// Set the control message, even if 0 bytes were read.
-			s.updateTimestamp()
-		}
-
-		cmsg := s.controlMessages()
-		s.fillCmsgInq(&cmsg)
-		s.readMu.Unlock()
-		return n, 0, nil, 0, cmsg, err
+	readOptions := tcpip.ReadOptions{
+		Peek:               peek,
+		NeedRemoteAddr:     senderRequested,
+		NeedLinkPacketInfo: isPacket,
 	}
 
-	s.readMu.Lock()
-	defer s.readMu.Unlock()
-
-	// MSG_TRUNC with MSG_PEEK on a TCP socket returns the
-	// amount that could be read, and does not write to buffer.
-	isTCPPeekTrunc := !isPacket && peek && trunc
-
+	// TCP sockets discard the data if MSG_TRUNC is set.
+	//
+	// This behavior is documented in man 7 tcp:
+	// Since version 2.4, Linux supports the use of MSG_TRUNC in the flags
+	// argument of recv(2) (and recvmsg(2)). This flag causes the received
+	// bytes of data to be discarded, rather than passed back in a
+	// caller-supplied  buffer.
 	var w io.Writer
-	if isTCPPeekTrunc {
+	if !isPacket && trunc {
 		w = ioutil.Discard
 	} else {
 		w = dst.Writer(ctx)
 	}
 
-	var numRead, numTotal int
-	var err *syserr.Error
-	numRead, numTotal, err = s.readLocked(w, int(dst.NumBytes()), peek)
-	if err != nil {
-		return 0, 0, nil, 0, socket.ControlMessages{}, err
-	}
+	s.readMu.Lock()
+	defer s.readMu.Unlock()
 
-	if isTCPPeekTrunc {
-		// TCP endpoint does not return the total bytes in buffer as numTotal.
-		// We need to query it from socket option.
-		rql, err := s.Endpoint.GetSockOptInt(tcpip.ReceiveQueueSizeOption)
-		if err != nil {
-			return 0, 0, nil, 0, socket.ControlMessages{}, syserr.TranslateNetstackError(err)
-		}
-		available := int(rql)
-		bufLen := int(dst.NumBytes())
-		if available < bufLen {
-			return available, 0, nil, 0, socket.ControlMessages{}, nil
-		}
-		return bufLen, 0, nil, 0, socket.ControlMessages{}, nil
+	res, err := s.Endpoint.Read(w, int(dst.NumBytes()), readOptions)
+	if err != nil {
+		return 0, 0, nil, 0, socket.ControlMessages{}, syserr.TranslateNetstackError(err)
 	}
-
 	// Set the control message, even if 0 bytes were read.
-	s.updateTimestamp()
+	s.updateTimestamp(res.ControlMessages)
 
-	var addr linux.SockAddr
-	var addrLen uint32
-	if isPacket && senderRequested {
-		addr, addrLen = socket.ConvertAddress(s.family, s.sender)
-		switch v := addr.(type) {
-		case *linux.SockAddrLink:
-			v.Protocol = socket.Htons(uint16(s.linkPacketInfo.Protocol))
-			v.PacketType = toLinuxPacketType(s.linkPacketInfo.PktType)
+	if isPacket {
+		var addr linux.SockAddr
+		var addrLen uint32
+		if senderRequested {
+			addr, addrLen = socket.ConvertAddress(s.family, res.RemoteAddr)
+			switch v := addr.(type) {
+			case *linux.SockAddrLink:
+				v.Protocol = socket.Htons(uint16(res.LinkPacketInfo.Protocol))
+				v.PacketType = toLinuxPacketType(res.LinkPacketInfo.PktType)
+			}
 		}
-	}
 
-	if peek {
-		if trunc && numTotal > numRead {
-			// isPacket must be true.
-			return numTotal, linux.MSG_TRUNC, addr, addrLen, s.controlMessages(), nil
+		msgLen := res.Count
+		if trunc {
+			msgLen = res.Total
 		}
-		return numRead, 0, nil, 0, s.controlMessages(), nil
-	}
 
-	var msgLen int
-	if isPacket {
-		msgLen = numTotal
-	} else {
-		msgLen = numRead
-	}
+		var flags int
+		if res.Total > res.Count {
+			flags |= linux.MSG_TRUNC
+		}
 
-	var flags int
-	if msgLen > numRead {
-		flags |= linux.MSG_TRUNC
+		return msgLen, flags, addr, addrLen, s.controlMessages(res.ControlMessages), nil
 	}
 
-	n := numRead
-	if trunc {
-		n = msgLen
+	if peek {
+		// MSG_TRUNC with MSG_PEEK on a TCP socket returns the
+		// amount that could be read, and does not write to buffer.
+		if trunc {
+			// TCP endpoint does not return the total bytes in buffer as numTotal.
+			// We need to query it from socket option.
+			rql, err := s.Endpoint.GetSockOptInt(tcpip.ReceiveQueueSizeOption)
+			if err != nil {
+				return 0, 0, nil, 0, socket.ControlMessages{}, syserr.TranslateNetstackError(err)
+			}
+			msgLen := int(dst.NumBytes())
+			if msgLen > rql {
+				msgLen = rql
+			}
+			return msgLen, 0, nil, 0, socket.ControlMessages{}, nil
+		}
+	} else if n := res.Count; n != 0 {
+		s.Endpoint.ModerateRecvBuf(n)
 	}
 
-	cmsg := s.controlMessages()
+	cmsg := s.controlMessages(res.ControlMessages)
 	s.fillCmsgInq(&cmsg)
-	return n, flags, addr, addrLen, cmsg, nil
+	return res.Count, 0, nil, 0, cmsg, syserr.TranslateNetstackError(err)
 }
 
-func (s *socketOpsCommon) controlMessages() socket.ControlMessages {
+func (s *socketOpsCommon) controlMessages(cm tcpip.ControlMessages) socket.ControlMessages {
+	readCM := socket.NewIPControlMessages(s.family, cm)
 	return socket.ControlMessages{
 		IP: socket.IPControlMessages{
-			HasTimestamp:       s.readCM.HasTimestamp && s.sockOptTimestamp,
-			Timestamp:          s.readCM.Timestamp,
-			HasInq:             s.readCM.HasInq,
-			Inq:                s.readCM.Inq,
-			HasTOS:             s.readCM.HasTOS,
-			TOS:                s.readCM.TOS,
-			HasTClass:          s.readCM.HasTClass,
-			TClass:             s.readCM.TClass,
-			HasIPPacketInfo:    s.readCM.HasIPPacketInfo,
-			PacketInfo:         s.readCM.PacketInfo,
-			OriginalDstAddress: s.readCM.OriginalDstAddress,
-			SockErr:            s.readCM.SockErr,
+			HasTimestamp:       readCM.HasTimestamp && s.sockOptTimestamp,
+			Timestamp:          readCM.Timestamp,
+			HasInq:             readCM.HasInq,
+			Inq:                readCM.Inq,
+			HasTOS:             readCM.HasTOS,
+			TOS:                readCM.TOS,
+			HasTClass:          readCM.HasTClass,
+			TClass:             readCM.TClass,
+			HasIPPacketInfo:    readCM.HasIPPacketInfo,
+			PacketInfo:         readCM.PacketInfo,
+			OriginalDstAddress: readCM.OriginalDstAddress,
+			SockErr:            readCM.SockErr,
 		},
 	}
 }
@@ -2743,11 +2674,11 @@ func (s *socketOpsCommon) controlMessages() socket.ControlMessages {
 // successfully writing packet data out to userspace.
 //
 // Precondition: s.readMu must be locked.
-func (s *socketOpsCommon) updateTimestamp() {
+func (s *socketOpsCommon) updateTimestamp(cm tcpip.ControlMessages) {
 	// Save the SIOCGSTAMP timestamp only if SO_TIMESTAMP is disabled.
 	if !s.sockOptTimestamp {
 		s.timestampValid = true
-		s.timestampNS = s.readCM.Timestamp
+		s.timestampNS = cm.Timestamp
 	}
 }