Merge release-20210301.0-31-g2a888a106 (automated)

6 files changed, 30 insertions, 22 deletions

diff --git a/pkg/tcpip/header/tcp.go b/pkg/tcpip/header/tcp.go
index 4c6f808e5..adc835d30 100644
--- a/pkg/tcpip/header/tcp.go
+++ b/pkg/tcpip/header/tcp.go
@@ -45,9 +45,23 @@ const (
 	TCPMaxSACKBlocks = 4
 )
 
+// TCPFlags is the dedicated type for TCP flags.
+type TCPFlags uint8
+
+// String implements Stringer.String.
+func (f TCPFlags) String() string {
+	flagsStr := []byte("FSRPAU")
+	for i := range flagsStr {
+		if f&(1<<uint(i)) == 0 {
+			flagsStr[i] = ' '
+		}
+	}
+	return string(flagsStr)
+}
+
 // Flags that may be set in a TCP segment.
 const (
-	TCPFlagFin = 1 << iota
+	TCPFlagFin TCPFlags = 1 << iota
 	TCPFlagSyn
 	TCPFlagRst
 	TCPFlagPsh
@@ -94,7 +108,7 @@ type TCPFields struct {
 	DataOffset uint8
 
 	// Flags is the "flags" field of a TCP packet.
-	Flags uint8
+	Flags TCPFlags
 
 	// WindowSize is the "window size" field of a TCP packet.
 	WindowSize uint16
@@ -234,8 +248,8 @@ func (b TCP) Payload() []byte {
 }
 
 // Flags returns the flags field of the tcp header.
-func (b TCP) Flags() uint8 {
-	return b[TCPFlagsOffset]
+func (b TCP) Flags() TCPFlags {
+	return TCPFlags(b[TCPFlagsOffset])
 }
 
 // WindowSize returns the "window size" field of the tcp header.
@@ -319,10 +333,10 @@ func (b TCP) ParsedOptions() TCPOptions {
 	return ParseTCPOptions(b.Options())
 }
 
-func (b TCP) encodeSubset(seq, ack uint32, flags uint8, rcvwnd uint16) {
+func (b TCP) encodeSubset(seq, ack uint32, flags TCPFlags, rcvwnd uint16) {
 	binary.BigEndian.PutUint32(b[TCPSeqNumOffset:], seq)
 	binary.BigEndian.PutUint32(b[TCPAckNumOffset:], ack)
-	b[TCPFlagsOffset] = flags
+	b[TCPFlagsOffset] = uint8(flags)
 	binary.BigEndian.PutUint16(b[TCPWinSizeOffset:], rcvwnd)
 }
 
@@ -338,7 +352,7 @@ func (b TCP) Encode(t *TCPFields) {
 
 // EncodePartial updates a subset of the fields of the tcp header. It is useful
 // in cases when similar segments are produced.
-func (b TCP) EncodePartial(partialChecksum, length uint16, seqnum, acknum uint32, flags byte, rcvwnd uint16) {
+func (b TCP) EncodePartial(partialChecksum, length uint16, seqnum, acknum uint32, flags TCPFlags, rcvwnd uint16) {
 	// Add the total length and "flags" field contributions to the checksum.
 	// We don't use the flags field directly from the header because it's a
 	// one-byte field with an odd offset, so it would be accounted for
diff --git a/pkg/tcpip/link/sniffer/sniffer.go b/pkg/tcpip/link/sniffer/sniffer.go
index 84189bba5..7aaee3d13 100644
--- a/pkg/tcpip/link/sniffer/sniffer.go
+++ b/pkg/tcpip/link/sniffer/sniffer.go
@@ -398,13 +398,7 @@ func logPacket(prefix string, dir direction, protocol tcpip.NetworkProtocolNumbe
 
 			// Initialize the TCP flags.
 			flags := tcp.Flags()
-			flagsStr := []byte("FSRPAU")
-			for i := range flagsStr {
-				if flags&(1<<uint(i)) == 0 {
-					flagsStr[i] = ' '
-				}
-			}
-			details = fmt.Sprintf("flags:0x%02x (%s) seqnum: %d ack: %d win: %d xsum:0x%x", flags, string(flagsStr), tcp.SequenceNumber(), tcp.AckNumber(), tcp.WindowSize(), tcp.Checksum())
+			details = fmt.Sprintf("flags: %s seqnum: %d ack: %d win: %d xsum:0x%x", flags, tcp.SequenceNumber(), tcp.AckNumber(), tcp.WindowSize(), tcp.Checksum())
 			if flags&header.TCPFlagSyn != 0 {
 				details += fmt.Sprintf(" options: %+v", header.ParseSynOptions(tcp.Options(), flags&header.TCPFlagAck != 0))
 			} else {
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 61a173fbb..3404af6bb 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -68,7 +68,7 @@ type handshake struct {
 	ep     *endpoint
 	state  handshakeState
 	active bool
-	flags  uint8
+	flags  header.TCPFlags
 	ackNum seqnum.Value
 
 	// iss is the initial send sequence number, as defined in RFC 793.
@@ -700,7 +700,7 @@ type tcpFields struct {
 	id     stack.TransportEndpointID
 	ttl    uint8
 	tos    uint8
-	flags  byte
+	flags  header.TCPFlags
 	seq    seqnum.Value
 	ack    seqnum.Value
 	rcvWnd seqnum.Size
@@ -877,7 +877,7 @@ func (e *endpoint) makeOptions(sackBlocks []header.SACKBlock) []byte {
 }
 
 // sendRaw sends a TCP segment to the endpoint's peer.
-func (e *endpoint) sendRaw(data buffer.VectorisedView, flags byte, seq, ack seqnum.Value, rcvWnd seqnum.Size) tcpip.Error {
+func (e *endpoint) sendRaw(data buffer.VectorisedView, flags header.TCPFlags, seq, ack seqnum.Value, rcvWnd seqnum.Size) tcpip.Error {
 	var sackBlocks []header.SACKBlock
 	if e.EndpointState() == StateEstablished && e.rcv.pendingRcvdSegments.Len() > 0 && (flags&header.TCPFlagAck != 0) {
 		sackBlocks = e.sack.Blocks[:e.sack.NumBlocks]
diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
index 04012cd40..2a4667906 100644
--- a/pkg/tcpip/transport/tcp/protocol.go
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -226,7 +226,7 @@ func replyWithReset(stack *stack.Stack, s *segment, tos, ttl uint8) tcpip.Error
 	// Get the seqnum from the packet if the ack flag is set.
 	seq := seqnum.Value(0)
 	ack := seqnum.Value(0)
-	flags := byte(header.TCPFlagRst)
+	flags := header.TCPFlagRst
 	// As per RFC 793 page 35 (Reset Generation)
 	//   1.  If the connection does not exist (CLOSED) then a reset is sent
 	//   in response to any incoming segment except another reset.  In
diff --git a/pkg/tcpip/transport/tcp/segment.go b/pkg/tcpip/transport/tcp/segment.go
index 744382100..8edd6775b 100644
--- a/pkg/tcpip/transport/tcp/segment.go
+++ b/pkg/tcpip/transport/tcp/segment.go
@@ -62,7 +62,7 @@ type segment struct {
 	views          [8]buffer.View `state:"nosave"`
 	sequenceNumber seqnum.Value
 	ackNumber      seqnum.Value
-	flags          uint8
+	flags          header.TCPFlags
 	window         seqnum.Size
 	// csum is only populated for received segments.
 	csum uint16
@@ -141,12 +141,12 @@ func (s *segment) clone() *segment {
 }
 
 // flagIsSet checks if at least one flag in flags is set in s.flags.
-func (s *segment) flagIsSet(flags uint8) bool {
+func (s *segment) flagIsSet(flags header.TCPFlags) bool {
 	return s.flags&flags != 0
 }
 
 // flagsAreSet checks if all flags in flags are set in s.flags.
-func (s *segment) flagsAreSet(flags uint8) bool {
+func (s *segment) flagsAreSet(flags header.TCPFlags) bool {
 	return s.flags&flags == flags
 }
 
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index 83c8deb0e..18817029d 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -1613,7 +1613,7 @@ func (s *sender) sendSegment(seg *segment) tcpip.Error {
 
 // sendSegmentFromView sends a new segment containing the given payload, flags
 // and sequence number.
-func (s *sender) sendSegmentFromView(data buffer.VectorisedView, flags byte, seq seqnum.Value) tcpip.Error {
+func (s *sender) sendSegmentFromView(data buffer.VectorisedView, flags header.TCPFlags, seq seqnum.Value) tcpip.Error {
 	s.lastSendTime = time.Now()
 	if seq == s.rttMeasureSeqNum {
 		s.rttMeasureTime = s.lastSendTime