5 files changed, 19 insertions, 25 deletions
diff --git a/pkg/tcpip/transport/tcp/BUILD b/pkg/tcpip/transport/tcp/BUILD
index f2aa69069..f38eb6833 100644
--- a/pkg/tcpip/transport/tcp/BUILD
+++ b/pkg/tcpip/transport/tcp/BUILD
@@ -115,7 +115,7 @@ go_test(
     size = "small",
     srcs = ["rcv_test.go"],
     deps = [
-        ":tcp",
+        "//pkg/tcpip/header",
         "//pkg/tcpip/seqnum",
     ],
 )
diff --git a/pkg/tcpip/transport/tcp/rcv.go b/pkg/tcpip/transport/tcp/rcv.go
index a4b73b588..6fe97fefd 100644
--- a/pkg/tcpip/transport/tcp/rcv.go
+++ b/pkg/tcpip/transport/tcp/rcv.go
@@ -70,24 +70,7 @@ func newReceiver(ep *endpoint, irs seqnum.Value, rcvWnd seqnum.Size, rcvWndScale
 // acceptable checks if the segment sequence number range is acceptable
 // according to the table on page 26 of RFC 793.
 func (r *receiver) acceptable(segSeq seqnum.Value, segLen seqnum.Size) bool {
-	return Acceptable(segSeq, segLen, r.rcvNxt, r.rcvAcc)
-}
-
-// Acceptable checks if a segment that starts at segSeq and has length segLen is
-// "acceptable" for arriving in a receive window that starts at rcvNxt and ends
-// before rcvAcc, according to the table on page 26 and 69 of RFC 793.
-func Acceptable(segSeq seqnum.Value, segLen seqnum.Size, rcvNxt, rcvAcc seqnum.Value) bool {
-	if rcvNxt == rcvAcc {
-		return segLen == 0 && segSeq == rcvNxt
-	}
-	if segLen == 0 {
-		// rcvWnd is incremented by 1 because that is Linux's behavior despite the
-		// RFC.
-		return segSeq.InRange(rcvNxt, rcvAcc.Add(1))
-	}
-	// Page 70 of RFC 793 allows packets that can be made "acceptable" by trimming
-	// the payload, so we'll accept any payload that overlaps the receieve window.
-	return rcvNxt.LessThan(segSeq.Add(segLen)) && segSeq.LessThan(rcvAcc)
+	return header.Acceptable(segSeq, segLen, r.rcvNxt, r.rcvAcc)
 }
 
 // getSendParams returns the parameters needed by the sender when building
diff --git a/pkg/tcpip/transport/tcp/rcv_test.go b/pkg/tcpip/transport/tcp/rcv_test.go
index dc02729ce..c9eeff935 100644
--- a/pkg/tcpip/transport/tcp/rcv_test.go
+++ b/pkg/tcpip/transport/tcp/rcv_test.go
@@ -17,8 +17,8 @@ package rcv_test
 import (
 	"testing"
 
+	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
-	"gvisor.dev/gvisor/pkg/tcpip/transport/tcp"
 )
 
 func TestAcceptable(t *testing.T) {
@@ -67,8 +67,8 @@ func TestAcceptable(t *testing.T) {
 		{105, 2, 108, 108, false},
 		{105, 2, 109, 109, false},
 	} {
-		if got := tcp.Acceptable(tt.segSeq, tt.segLen, tt.rcvNxt, tt.rcvAcc); got != tt.want {
-			t.Errorf("tcp.Acceptable(%d, %d, %d, %d) = %t, want %t", tt.segSeq, tt.segLen, tt.rcvNxt, tt.rcvAcc, got, tt.want)
+		if got := header.Acceptable(tt.segSeq, tt.segLen, tt.rcvNxt, tt.rcvAcc); got != tt.want {
+			t.Errorf("header.Acceptable(%d, %d, %d, %d) = %t, want %t", tt.segSeq, tt.segLen, tt.rcvNxt, tt.rcvAcc, got, tt.want)
 		}
 	}
 }
diff --git a/pkg/tcpip/transport/tcpconntrack/BUILD b/pkg/tcpip/transport/tcpconntrack/BUILD
index 2025ff757..3ad6994a7 100644
--- a/pkg/tcpip/transport/tcpconntrack/BUILD
+++ b/pkg/tcpip/transport/tcpconntrack/BUILD
@@ -9,7 +9,6 @@ go_library(
     deps = [
         "//pkg/tcpip/header",
         "//pkg/tcpip/seqnum",
-        "//pkg/tcpip/transport/tcp",
     ],
 )
 
diff --git a/pkg/tcpip/transport/tcpconntrack/tcp_conntrack.go b/pkg/tcpip/transport/tcpconntrack/tcp_conntrack.go
index 30d05200f..12bc1b5b5 100644
--- a/pkg/tcpip/transport/tcpconntrack/tcp_conntrack.go
+++ b/pkg/tcpip/transport/tcpconntrack/tcp_conntrack.go
@@ -20,7 +20,6 @@ package tcpconntrack
 import (
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
-	"gvisor.dev/gvisor/pkg/tcpip/transport/tcp"
 )
 
 // Result is returned when the state of a TCB is updated in response to an
@@ -312,7 +311,7 @@ type stream struct {
 // the window is zero, if it's a packet with no payload and sequence number
 // equal to una.
 func (s *stream) acceptable(segSeq seqnum.Value, segLen seqnum.Size) bool {
-	return tcp.Acceptable(segSeq, segLen, s.una, s.end)
+	return header.Acceptable(segSeq, segLen, s.una, s.end)
 }
 
 // closed determines if the stream has already been closed. This happens when
@@ -338,3 +337,16 @@ func logicalLen(tcp header.TCP) seqnum.Size {
 	}
 	return l
 }
+
+// IsEmpty returns true if tcb is not initialized.
+func (t *TCB) IsEmpty() bool {
+	if t.inbound != (stream{}) || t.outbound != (stream{}) {
+		return false
+	}
+
+	if t.firstFin != nil || t.state != ResultDrop {
+		return false
+	}
+
+	return true
+}