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-rw-r--r--pkg/tcpip/transport/tcp/accept.go33
-rw-r--r--pkg/tcpip/transport/tcp/connect.go31
-rw-r--r--pkg/tcpip/transport/tcp/tcp_test.go267
3 files changed, 157 insertions, 174 deletions
diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index a32e20b06..d05259c0a 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -251,7 +251,7 @@ func (l *listenContext) createEndpointAndPerformHandshake(s *segment, opts *head
// Perform the 3-way handshake.
h := newHandshake(ep, l.rcvWnd)
- h.resetToSynRcvd(cookie, irs, opts, l.listenEP)
+ h.resetToSynRcvd(cookie, irs, opts)
if err := h.execute(); err != nil {
ep.stack.Stats().TCP.FailedConnectionAttempts.Increment()
ep.Close()
@@ -294,7 +294,6 @@ func (e *endpoint) handleSynSegment(ctx *listenContext, s *segment, opts *header
defer decSynRcvdCount()
defer e.decSynRcvdCount()
defer s.decRef()
-
n, err := ctx.createEndpointAndPerformHandshake(s, opts)
if err != nil {
e.stack.Stats().TCP.FailedConnectionAttempts.Increment()
@@ -306,7 +305,7 @@ func (e *endpoint) handleSynSegment(ctx *listenContext, s *segment, opts *header
func (e *endpoint) incSynRcvdCount() bool {
e.mu.Lock()
- if l, c := len(e.acceptedChan), cap(e.acceptedChan); l == c && e.synRcvdCount >= c {
+ if e.synRcvdCount >= cap(e.acceptedChan) {
e.mu.Unlock()
return false
}
@@ -321,6 +320,16 @@ func (e *endpoint) decSynRcvdCount() {
e.mu.Unlock()
}
+func (e *endpoint) acceptQueueIsFull() bool {
+ e.mu.Lock()
+ if l, c := len(e.acceptedChan)+e.synRcvdCount, cap(e.acceptedChan); l >= c {
+ e.mu.Unlock()
+ return true
+ }
+ e.mu.Unlock()
+ return false
+}
+
// handleListenSegment is called when a listening endpoint receives a segment
// and needs to handle it.
func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) {
@@ -328,17 +337,27 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) {
case header.TCPFlagSyn:
opts := parseSynSegmentOptions(s)
if incSynRcvdCount() {
- // Drop the SYN if the listen endpoint's accept queue is
- // overflowing.
- if e.incSynRcvdCount() {
+ // Only handle the syn if the following conditions hold
+ // - accept queue is not full.
+ // - number of connections in synRcvd state is less than the
+ // backlog.
+ if !e.acceptQueueIsFull() && e.incSynRcvdCount() {
s.incRef()
go e.handleSynSegment(ctx, s, &opts) // S/R-SAFE: synRcvdCount is the barrier.
return
}
+ decSynRcvdCount()
e.stack.Stats().TCP.ListenOverflowSynDrop.Increment()
e.stack.Stats().DroppedPackets.Increment()
return
} else {
+ // If cookies are in use but the endpoint accept queue
+ // is full then drop the syn.
+ if e.acceptQueueIsFull() {
+ e.stack.Stats().TCP.ListenOverflowSynDrop.Increment()
+ e.stack.Stats().DroppedPackets.Increment()
+ return
+ }
cookie := ctx.createCookie(s.id, s.sequenceNumber, encodeMSS(opts.MSS))
// Send SYN with window scaling because we currently
// dont't encode this information in the cookie.
@@ -356,7 +375,7 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) {
}
case header.TCPFlagAck:
- if len(e.acceptedChan) == cap(e.acceptedChan) {
+ if e.acceptQueueIsFull() {
// Silently drop the ack as the application can't accept
// the connection at this point. The ack will be
// retransmitted by the sender anyway and we can
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 0ad7bfb38..dd671f7ce 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -60,12 +60,11 @@ const (
// handshake holds the state used during a TCP 3-way handshake.
type handshake struct {
- ep *endpoint
- listenEP *endpoint // only non nil when doing passive connects.
- state handshakeState
- active bool
- flags uint8
- ackNum seqnum.Value
+ ep *endpoint
+ state handshakeState
+ active bool
+ flags uint8
+ ackNum seqnum.Value
// iss is the initial send sequence number, as defined in RFC 793.
iss seqnum.Value
@@ -142,7 +141,7 @@ func (h *handshake) effectiveRcvWndScale() uint8 {
// resetToSynRcvd resets the state of the handshake object to the SYN-RCVD
// state.
-func (h *handshake) resetToSynRcvd(iss seqnum.Value, irs seqnum.Value, opts *header.TCPSynOptions, listenEP *endpoint) {
+func (h *handshake) resetToSynRcvd(iss seqnum.Value, irs seqnum.Value, opts *header.TCPSynOptions) {
h.active = false
h.state = handshakeSynRcvd
h.flags = header.TCPFlagSyn | header.TCPFlagAck
@@ -150,7 +149,6 @@ func (h *handshake) resetToSynRcvd(iss seqnum.Value, irs seqnum.Value, opts *hea
h.ackNum = irs + 1
h.mss = opts.MSS
h.sndWndScale = opts.WS
- h.listenEP = listenEP
h.ep.mu.Lock()
h.ep.state = StateSynRecv
h.ep.mu.Unlock()
@@ -287,23 +285,6 @@ func (h *handshake) synRcvdState(s *segment) *tcpip.Error {
// We have previously received (and acknowledged) the peer's SYN. If the
// peer acknowledges our SYN, the handshake is completed.
if s.flagIsSet(header.TCPFlagAck) {
- // listenContext is also used by a tcp.Forwarder and in that
- // context we do not have a listening endpoint to check the
- // backlog. So skip this check if listenEP is nil.
- if h.listenEP != nil {
- h.listenEP.mu.Lock()
- if len(h.listenEP.acceptedChan) == cap(h.listenEP.acceptedChan) {
- h.listenEP.mu.Unlock()
- // If there is no space in the accept queue to accept
- // this endpoint then silently drop this ACK. The peer
- // will anyway resend the ack and we can complete the
- // connection the next time it's retransmitted.
- h.ep.stack.Stats().TCP.ListenOverflowAckDrop.Increment()
- h.ep.stack.Stats().DroppedPackets.Increment()
- return nil
- }
- h.listenEP.mu.Unlock()
- }
// If the timestamp option is negotiated and the segment does
// not carry a timestamp option then the segment must be dropped
// as per https://tools.ietf.org/html/rfc7323#section-3.2.
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index 56b490aaa..779ca8b76 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -3405,7 +3405,7 @@ func executeHandshake(t *testing.T, c *context.Context, srcPort uint16, synCooki
RcvWnd: 30000,
})
- // Receive the SYN-ACK reply.
+ // Receive the SYN-ACK reply.w
b := c.GetPacket()
tcp := header.TCP(header.IPv4(b).Payload())
iss = seqnum.Value(tcp.SequenceNumber())
@@ -3469,12 +3469,18 @@ func TestListenBacklogFull(t *testing.T) {
time.Sleep(50 * time.Millisecond)
- // Now execute one more handshake. This should not be completed and
- // delivered on an Accept() call as the backlog is full at this point.
- irs, iss := executeHandshake(t, c, context.TestPort+uint16(listenBacklog), false /* synCookieInUse */)
+ // Now execute send one more SYN. The stack should not respond as the backlog
+ // is full at this point.
+ c.SendPacket(nil, &context.Headers{
+ SrcPort: context.TestPort + 2,
+ DstPort: context.StackPort,
+ Flags: header.TCPFlagSyn,
+ SeqNum: seqnum.Value(789),
+ RcvWnd: 30000,
+ })
+ c.CheckNoPacketTimeout("unexpected packet received", 50*time.Millisecond)
- time.Sleep(50 * time.Millisecond)
- // Try to accept the connection.
+ // Try to accept the connections in the backlog.
we, ch := waiter.NewChannelEntry(nil)
c.WQ.EventRegister(&we, waiter.EventIn)
defer c.WQ.EventUnregister(&we)
@@ -3506,16 +3512,8 @@ func TestListenBacklogFull(t *testing.T) {
}
}
- // Now craft the ACK again and verify that the connection is now ready
- // to be accepted.
- c.SendPacket(nil, &context.Headers{
- SrcPort: context.TestPort + uint16(listenBacklog),
- DstPort: context.StackPort,
- Flags: header.TCPFlagAck,
- SeqNum: irs + 1,
- AckNum: iss + 1,
- RcvWnd: 30000,
- })
+ // Now a new handshake must succeed.
+ executeHandshake(t, c, context.TestPort+2, false /*synCookieInUse */)
newEP, _, err := c.EP.Accept()
if err == tcpip.ErrWouldBlock {
@@ -3531,6 +3529,7 @@ func TestListenBacklogFull(t *testing.T) {
t.Fatalf("Timed out waiting for accept")
}
}
+
// Now verify that the TCP socket is usable and in a connected state.
data := "Don't panic"
newEP.Write(tcpip.SlicePayload(buffer.NewViewFromBytes([]byte(data))), tcpip.WriteOptions{})
@@ -3541,13 +3540,7 @@ func TestListenBacklogFull(t *testing.T) {
}
}
-func TestListenBacklogFullSynCookieInUse(t *testing.T) {
- saved := tcp.SynRcvdCountThreshold
- defer func() {
- tcp.SynRcvdCountThreshold = saved
- }()
- tcp.SynRcvdCountThreshold = 1
-
+func TestListenSynRcvdQueueFull(t *testing.T) {
c := context.New(t, defaultMTU)
defer c.Cleanup()
@@ -3566,48 +3559,72 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
// Test acceptance.
// Start listening.
listenBacklog := 1
- portOffset := uint16(0)
if err := c.EP.Listen(listenBacklog); err != nil {
t.Fatalf("Listen failed: %v", err)
}
- executeHandshake(t, c, context.TestPort+portOffset, false)
- portOffset++
- // Wait for this to be delivered to the accept queue.
- time.Sleep(50 * time.Millisecond)
+ // Send two SYN's the first one should get a SYN-ACK, the
+ // second one should not get any response and is dropped as
+ // the synRcvd count will be equal to backlog.
+ irs := seqnum.Value(789)
+ c.SendPacket(nil, &context.Headers{
+ SrcPort: context.TestPort,
+ DstPort: context.StackPort,
+ Flags: header.TCPFlagSyn,
+ SeqNum: seqnum.Value(789),
+ RcvWnd: 30000,
+ })
- nonCookieIRS, nonCookieISS := executeHandshake(t, c, context.TestPort+portOffset, false)
+ // Receive the SYN-ACK reply.
+ b := c.GetPacket()
+ tcp := header.TCP(header.IPv4(b).Payload())
+ iss := seqnum.Value(tcp.SequenceNumber())
+ tcpCheckers := []checker.TransportChecker{
+ checker.SrcPort(context.StackPort),
+ checker.DstPort(context.TestPort),
+ checker.TCPFlags(header.TCPFlagAck | header.TCPFlagSyn),
+ checker.AckNum(uint32(irs) + 1),
+ }
+ checker.IPv4(t, b, checker.TCP(tcpCheckers...))
- // Since the backlog is full at this point this connection will not
- // transition out of handshake and ignore the ACK.
- //
- // At this point there should be 1 completed connection in the backlog
- // and one incomplete one pending for a final ACK and hence not ready to be
- // delivered to the endpoint.
+ // Now execute send one more SYN. The stack should not respond as the backlog
+ // is full at this point.
//
- // Now execute one more handshake. This should not be completed and
- // delivered on an Accept() call as the backlog is full at this point
- // and there is already 1 pending endpoint.
- //
- // This one should use a SYN cookie as the synRcvdCount is equal to the
- // SynRcvdCountThreshold.
- time.Sleep(50 * time.Millisecond)
- portOffset++
- irs, iss := executeHandshake(t, c, context.TestPort+portOffset, true)
+ // NOTE: we did not complete the handshake for the previous one so the
+ // accept backlog should be empty and there should be one connection in
+ // synRcvd state.
+ c.SendPacket(nil, &context.Headers{
+ SrcPort: context.TestPort + 1,
+ DstPort: context.StackPort,
+ Flags: header.TCPFlagSyn,
+ SeqNum: seqnum.Value(889),
+ RcvWnd: 30000,
+ })
+ c.CheckNoPacketTimeout("unexpected packet received", 50*time.Millisecond)
- time.Sleep(50 * time.Millisecond)
+ // Now complete the previous connection and verify that there is a connection
+ // to accept.
+ // Send ACK.
+ c.SendPacket(nil, &context.Headers{
+ SrcPort: context.TestPort,
+ DstPort: context.StackPort,
+ Flags: header.TCPFlagAck,
+ SeqNum: irs + 1,
+ AckNum: iss + 1,
+ RcvWnd: 30000,
+ })
- // Verify that there is only one acceptable connection at this point.
+ // Try to accept the connections in the backlog.
we, ch := waiter.NewChannelEntry(nil)
c.WQ.EventRegister(&we, waiter.EventIn)
defer c.WQ.EventUnregister(&we)
- _, _, err = c.EP.Accept()
+ newEP, _, err := c.EP.Accept()
if err == tcpip.ErrWouldBlock {
// Wait for connection to be established.
select {
case <-ch:
- _, _, err = c.EP.Accept()
+ newEP, _, err = c.EP.Accept()
if err != nil {
t.Fatalf("Accept failed: %v", err)
}
@@ -3617,27 +3634,68 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
}
}
- // Now verify that there are no more connections that can be accepted.
- _, _, err = c.EP.Accept()
- if err != tcpip.ErrWouldBlock {
- select {
- case <-ch:
- t.Fatalf("unexpected endpoint delivered on Accept: %+v", c.EP)
- case <-time.After(1 * time.Second):
- }
+ // Now verify that the TCP socket is usable and in a connected state.
+ data := "Don't panic"
+ newEP.Write(tcpip.SlicePayload(buffer.NewViewFromBytes([]byte(data))), tcpip.WriteOptions{})
+ pkt := c.GetPacket()
+ tcp = header.TCP(header.IPv4(pkt).Payload())
+ if string(tcp.Payload()) != data {
+ t.Fatalf("Unexpected data: got %v, want %v", string(tcp.Payload()), data)
}
+}
+
+func TestListenBacklogFullSynCookieInUse(t *testing.T) {
+ saved := tcp.SynRcvdCountThreshold
+ defer func() {
+ tcp.SynRcvdCountThreshold = saved
+ }()
+ tcp.SynRcvdCountThreshold = 1
+
+ c := context.New(t, defaultMTU)
+ defer c.Cleanup()
- // Now send an ACK for the half completed connection
+ // Create TCP endpoint.
+ var err *tcpip.Error
+ c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
+ if err != nil {
+ t.Fatalf("NewEndpoint failed: %v", err)
+ }
+
+ // Bind to wildcard.
+ if err := c.EP.Bind(tcpip.FullAddress{Port: context.StackPort}); err != nil {
+ t.Fatalf("Bind failed: %v", err)
+ }
+
+ // Test acceptance.
+ // Start listening.
+ listenBacklog := 1
+ portOffset := uint16(0)
+ if err := c.EP.Listen(listenBacklog); err != nil {
+ t.Fatalf("Listen failed: %v", err)
+ }
+
+ executeHandshake(t, c, context.TestPort+portOffset, false)
+ portOffset++
+ // Wait for this to be delivered to the accept queue.
+ time.Sleep(50 * time.Millisecond)
+
+ // Send a SYN request.
+ irs := seqnum.Value(789)
c.SendPacket(nil, &context.Headers{
- SrcPort: context.TestPort + portOffset - 1,
+ SrcPort: context.TestPort,
DstPort: context.StackPort,
- Flags: header.TCPFlagAck,
- SeqNum: nonCookieIRS + 1,
- AckNum: nonCookieISS + 1,
+ Flags: header.TCPFlagSyn,
+ SeqNum: irs,
RcvWnd: 30000,
})
+ // The Syn should be dropped as the endpoint's backlog is full.
+ c.CheckNoPacketTimeout("unexpected packet received", 50*time.Millisecond)
+
+ // Verify that there is only one acceptable connection at this point.
+ we, ch := waiter.NewChannelEntry(nil)
+ c.WQ.EventRegister(&we, waiter.EventIn)
+ defer c.WQ.EventUnregister(&we)
- // Verify that the connection is now delivered to the backlog.
_, _, err = c.EP.Accept()
if err == tcpip.ErrWouldBlock {
// Wait for connection to be established.
@@ -3653,41 +3711,15 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
}
}
- // Finally send an ACK for the connection that used a cookie and verify that
- // it's also completed and delivered.
- c.SendPacket(nil, &context.Headers{
- SrcPort: context.TestPort + portOffset,
- DstPort: context.StackPort,
- Flags: header.TCPFlagAck,
- SeqNum: irs,
- AckNum: iss,
- RcvWnd: 30000,
- })
-
- time.Sleep(50 * time.Millisecond)
- newEP, _, err := c.EP.Accept()
- if err == tcpip.ErrWouldBlock {
- // Wait for connection to be established.
+ // Now verify that there are no more connections that can be accepted.
+ _, _, err = c.EP.Accept()
+ if err != tcpip.ErrWouldBlock {
select {
case <-ch:
- newEP, _, err = c.EP.Accept()
- if err != nil {
- t.Fatalf("Accept failed: %v", err)
- }
-
+ t.Fatalf("unexpected endpoint delivered on Accept: %+v", c.EP)
case <-time.After(1 * time.Second):
- t.Fatalf("Timed out waiting for accept")
}
}
-
- // Now verify that the TCP socket is usable and in a connected state.
- data := "Don't panic"
- newEP.Write(tcpip.SlicePayload(buffer.NewViewFromBytes([]byte(data))), tcpip.WriteOptions{})
- b := c.GetPacket()
- tcp := header.TCP(header.IPv4(b).Payload())
- if string(tcp.Payload()) != data {
- t.Fatalf("Unexpected data: got %v, want %v", string(tcp.Payload()), data)
- }
}
func TestPassiveConnectionAttemptIncrement(t *testing.T) {
@@ -3761,18 +3793,12 @@ func TestPassiveFailedConnectionAttemptIncrement(t *testing.T) {
}
srcPort := uint16(context.TestPort)
- // Now attempt 3 handshakes, the first two will fill up the accept and the SYN-RCVD
- // queue for the endpoint.
+ // Now attempt a handshakes it will fill up the accept backlog.
executeHandshake(t, c, srcPort, false)
// Give time for the final ACK to be processed as otherwise the next handshake could
// get accepted before the previous one based on goroutine scheduling.
time.Sleep(50 * time.Millisecond)
- irs, iss := executeHandshake(t, c, srcPort+1, false)
-
- // Wait for a short while for the accepted connection to be delivered to
- // the channel before trying to send the 3rd SYN.
- time.Sleep(40 * time.Millisecond)
want := stats.TCP.ListenOverflowSynDrop.Value() + 1
@@ -3810,49 +3836,6 @@ func TestPassiveFailedConnectionAttemptIncrement(t *testing.T) {
t.Fatalf("Timed out waiting for accept")
}
}
-
- // Now complete the next connection in SYN-RCVD state as it should
- // have dropped the final ACK to the handshake due to accept queue
- // being full.
- c.SendPacket(nil, &context.Headers{
- SrcPort: srcPort + 1,
- DstPort: context.StackPort,
- Flags: header.TCPFlagAck,
- SeqNum: irs + 1,
- AckNum: iss + 1,
- RcvWnd: 30000,
- })
-
- // Now check that there is one more acceptable connections.
- _, _, err = c.EP.Accept()
- if err == tcpip.ErrWouldBlock {
- // Wait for connection to be established.
- select {
- case <-ch:
- _, _, err = c.EP.Accept()
- if err != nil {
- t.Fatalf("Accept failed: %v", err)
- }
-
- case <-time.After(1 * time.Second):
- t.Fatalf("Timed out waiting for accept")
- }
- }
-
- // Try and accept a 3rd one this should fail.
- _, _, err = c.EP.Accept()
- if err == tcpip.ErrWouldBlock {
- // Wait for connection to be established.
- select {
- case <-ch:
- ep, _, err = c.EP.Accept()
- if err == nil {
- t.Fatalf("Accept succeeded when it should have failed got: %+v", ep)
- }
-
- case <-time.After(1 * time.Second):
- }
- }
}
func TestEndpointBindListenAcceptState(t *testing.T) {
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-25 00:50:40 +0000