mirror of
https://github.com/soypat/lneto.git
synced 2026-08-16 12:53:26 +00:00
rewrite tests to capture more finwait2 receive segment expected functionality
This commit is contained in:
Patricio Whittingslow
+94
-98
@@ -590,112 +590,108 @@ func TestIssue19(t *testing.T) {
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}
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}
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// TestRcvFinWait2_BareACK reproduces the bug where rcvFinWait2 rejects any segment
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// without both FIN and ACK flags. Per RFC 9293 §3.10.7.4, FIN-WAIT-2 should:
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// - Silently accept bare ACKs (duplicate ACKs, window updates)
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// - Accept incoming data (remote hasn't sent FIN yet)
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// - Transition to TIME-WAIT only when FIN is received
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//
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// The overly strict check causes connections to get stuck in FIN-WAIT-2 until timeout,
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// exhausting the connection pool when multiple clients are affected.
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func TestRcvFinWait2_BareACK(t *testing.T) {
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var tcb tcp.ControlBlock
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// TestRcvFinWait2 tests rcvFinWait2 behavior per RFC 9293 §3.10.7.4.
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// In FIN-WAIT-2, the local side has sent FIN and received its ACK.
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// The remote side has NOT closed yet and may still send data or ACKs.
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func TestRcvFinWait2(t *testing.T) {
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const windowA, windowB = 1000, 1000
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const issA, issB = 100, 300
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tcb.HelperInitState(tcp.StateEstablished, issA, issA, windowA)
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tcb.HelperInitRcv(issB, issB, windowB)
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assertState := func(want tcp.State) {
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// enterFinWait2 returns a ControlBlock in FIN-WAIT-2 with no pending flags.
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// Simulates: A sent FIN|ACK, B acknowledged it, A drained pending ACK.
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enterFinWait2 := func(t *testing.T) tcp.ControlBlock {
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t.Helper()
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if tcb.State() != want {
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t.Fatalf("want state %s; got %s", want, tcb.State())
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var tcb tcp.ControlBlock
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tcb.HelperInitState(tcp.StateEstablished, issA, issA, windowA)
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tcb.HelperInitRcv(issB, issB, windowB)
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if err := tcb.Close(); err != nil {
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t.Fatal(err)
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}
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seg, _ := tcb.PendingSegment(0)
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if err := tcb.Send(seg); err != nil {
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t.Fatal(err)
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}
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if err := tcb.Recv(tcp.Segment{SEQ: issB, ACK: issA + 1, Flags: tcp.FlagACK, WND: windowB}); err != nil {
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t.Fatal(err)
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}
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if tcb.State() != tcp.StateFinWait2 {
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t.Fatalf("setup: want FIN-WAIT-2; got %s", tcb.State())
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}
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// Drain pending ACK left from rcvFinWait1 so subtests start clean.
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if seg, ok := tcb.PendingSegment(0); ok {
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if err := tcb.Send(seg); err != nil {
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t.Fatal(err)
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}
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}
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return tcb
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}
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// A initiates close → sends FIN|ACK.
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err := tcb.Close()
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if err != nil {
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t.Fatal(err)
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}
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seg, ok := tcb.PendingSegment(0)
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if !ok || !seg.Flags.HasAll(FINACK) {
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t.Fatalf("expected FIN|ACK pending; got %+v (ok=%v)", seg, ok)
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}
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err = tcb.Send(seg)
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if err != nil {
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t.Fatal(err)
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}
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assertState(tcp.StateFinWait1)
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// Bare ACK: no state change, no pending flags generated.
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t.Run("BareACK", func(t *testing.T) {
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tcb := enterFinWait2(t)
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err := tcb.Recv(tcp.Segment{SEQ: issB, ACK: issA + 1, Flags: tcp.FlagACK, WND: windowB})
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if err != nil {
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t.Fatalf("bare ACK rejected: %v", err)
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}
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if tcb.State() != tcp.StateFinWait2 {
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t.Fatalf("want FIN-WAIT-2; got %s", tcb.State())
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}
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checkNoPending(t, &tcb)
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})
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// A receives ACK for its FIN → FIN-WAIT-2.
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err = tcb.Recv(tcp.Segment{SEQ: issB, ACK: issA + 1, Flags: tcp.FlagACK, WND: windowB})
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if err != nil {
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t.Fatal(err)
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}
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assertState(tcp.StateFinWait2)
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// In-window data: ACK generated, RCV.NXT advanced by payload length.
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t.Run("InWindowData", func(t *testing.T) {
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tcb := enterFinWait2(t)
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rcvNxtBefore := tcb.RecvNext()
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const dataLen = 50
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err := tcb.Recv(tcp.Segment{SEQ: issB, ACK: issA + 1, Flags: PSHACK, WND: windowB, DATALEN: dataLen})
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if err != nil {
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t.Fatalf("in-window data rejected: %v", err)
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}
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if tcb.State() != tcp.StateFinWait2 {
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t.Fatalf("want FIN-WAIT-2; got %s", tcb.State())
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}
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seg, ok := tcb.PendingSegment(0)
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if !ok {
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t.Fatal("expected ACK pending for received data")
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}
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if !seg.Flags.HasAll(tcp.FlagACK) {
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t.Fatalf("pending flags: want ACK; got %s", seg.Flags)
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}
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if seg.ACK != rcvNxtBefore+dataLen {
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t.Fatalf("pending ACK: want %d; got %d", rcvNxtBefore+dataLen, seg.ACK)
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}
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if tcb.RecvNext() != rcvNxtBefore+dataLen {
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t.Fatalf("RCV.NXT: want %d; got %d", rcvNxtBefore+dataLen, tcb.RecvNext())
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}
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})
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// A receives bare ACK (duplicate/window update) in FIN-WAIT-2.
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// RFC 9293: this should be silently accepted, NOT rejected.
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err = tcb.Recv(tcp.Segment{SEQ: issB, ACK: issA + 1, Flags: tcp.FlagACK, WND: windowB})
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if err != nil {
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t.Fatalf("bare ACK in FIN-WAIT-2 rejected: %v", err)
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}
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assertState(tcp.StateFinWait2)
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// A receives FIN|ACK → TIME-WAIT.
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err = tcb.Recv(tcp.Segment{SEQ: issB, ACK: issA + 1, Flags: FINACK, WND: windowB})
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if err != nil {
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t.Fatal(err)
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}
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assertState(tcp.StateTimeWait)
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}
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// TestRcvFinWait2_DataFromRemote tests that data segments are accepted in FIN-WAIT-2.
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// The remote side has not sent FIN yet and may still send data per RFC 9293 §3.10.7.4.
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func TestRcvFinWait2_DataFromRemote(t *testing.T) {
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var tcb tcp.ControlBlock
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const windowA, windowB = 1000, 1000
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const issA, issB = 100, 300
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tcb.HelperInitState(tcp.StateEstablished, issA, issA, windowA)
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tcb.HelperInitRcv(issB, issB, windowB)
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// A sends FIN|ACK → FIN-WAIT-1.
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err := tcb.Close()
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if err != nil {
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t.Fatal(err)
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}
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seg, _ := tcb.PendingSegment(0)
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err = tcb.Send(seg)
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if err != nil {
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t.Fatal(err)
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}
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// A receives ACK → FIN-WAIT-2.
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err = tcb.Recv(tcp.Segment{SEQ: issB, ACK: issA + 1, Flags: tcp.FlagACK, WND: windowB})
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if err != nil {
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t.Fatal(err)
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}
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if tcb.State() != tcp.StateFinWait2 {
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t.Fatalf("want FIN-WAIT-2; got %s", tcb.State())
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}
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// A receives data from remote (remote hasn't closed yet).
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const dataLen = 50
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err = tcb.Recv(tcp.Segment{SEQ: issB, ACK: issA + 1, Flags: PSHACK, WND: windowB, DATALEN: dataLen})
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if err != nil {
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t.Fatalf("data in FIN-WAIT-2 rejected: %v", err)
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}
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if tcb.State() != tcp.StateFinWait2 {
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t.Fatalf("want FIN-WAIT-2 after data; got %s", tcb.State())
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}
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// A receives FIN|ACK → TIME-WAIT.
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err = tcb.Recv(tcp.Segment{SEQ: issB + dataLen, ACK: issA + 1, Flags: FINACK, WND: windowB})
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if err != nil {
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t.Fatal(err)
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}
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if tcb.State() != tcp.StateTimeWait {
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t.Fatalf("want TIME-WAIT; got %s", tcb.State())
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}
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// FIN (without ACK): transition to TIME-WAIT, ACK generated, RCV.NXT advanced by 1.
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t.Run("FIN", func(t *testing.T) {
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tcb := enterFinWait2(t)
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rcvNxtBefore := tcb.RecvNext()
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// Bare FIN without ACK — tests that HasAny(FlagFIN) is used, not HasAll(finack).
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err := tcb.Recv(tcp.Segment{SEQ: issB, Flags: tcp.FlagFIN, WND: windowB})
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if err != nil {
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t.Fatalf("FIN rejected: %v", err)
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}
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if tcb.State() != tcp.StateTimeWait {
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t.Fatalf("want TIME-WAIT; got %s", tcb.State())
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}
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seg, ok := tcb.PendingSegment(0)
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if !ok {
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t.Fatal("expected ACK pending for FIN")
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}
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if !seg.Flags.HasAll(tcp.FlagACK) {
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t.Fatalf("pending flags: want ACK; got %s", seg.Flags)
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}
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if seg.ACK != rcvNxtBefore+1 {
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t.Fatalf("pending ACK: want %d; got %d", rcvNxtBefore+1, seg.ACK)
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}
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if tcb.RecvNext() != rcvNxtBefore+1 {
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t.Fatalf("RCV.NXT: want %d; got %d", rcvNxtBefore+1, tcb.RecvNext())
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}
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})
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}
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func FuzzTCBActions(f *testing.F) {
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