add ring

soypat · Nov 18, 2023 · 87fcde4 · 87fcde4
1 parent 0d337c9
commit 87fcde4
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Showing 2 changed files with 152 additions and 7 deletions.
diff --git a/stack/socket_tcp.go b/stack/socket_tcp.go
@@ -1,6 +1,8 @@
 package stack
 
 import (
+	"errors"
+	"io"
 	"net/netip"
 	"time"
 
@@ -11,19 +13,31 @@ type tcp struct {
 	stack     *PortStack
 	scb       seqs.ControlBlock
 	localPort uint16
-	iss       seqs.Value
-	wnd       seqs.Size
 	lastTx    time.Time
 	lastRx    time.Time
 	// Remote fields discovered during an active open.
 	remote    netip.AddrPort
 	remoteMAC [6]byte
+	tx        ring
 }
 
 func (t *tcp) State() seqs.State {
 	return t.scb.State()
 }
 
+func (t *tcp) Send(b []byte) error {
+	if t.tx.buf == nil {
+		t.tx = ring{
+			buf: make([]byte, 2048),
+		}
+	}
+	_, err := t.tx.Write(b)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
 // DialTCP opens an active TCP connection to the given remote address.
 func DialTCP(stack *PortStack, localPort uint16, remoteMAC [6]byte, remote netip.AddrPort, iss seqs.Value, window seqs.Size) (*tcp, error) {
 	t := tcp{
@@ -147,8 +161,6 @@ func (t *tcp) mustSendSyn() bool {
 
 func (t *tcp) close() {
 	t.remote = netip.AddrPort{}
-	t.wnd = 0
-	t.iss = 0
 	t.scb = seqs.ControlBlock{}
 	t.lastTx = time.Time{}
 	t.lastRx = time.Time{}
@@ -162,3 +174,89 @@ func (t *tcp) synsentSegment() seqs.Segment {
 		WND:   t.scb.RecvWindow(),
 	}
 }
+
+type ring struct {
+	buf []byte
+	off int
+	end int
+}
+
+func (r *ring) Write(b []byte) (int, error) {
+	free := r.Free()
+	if len(b) > free {
+		return 0, errors.New("no more space")
+	}
+	midFree := r.midFree()
+	if midFree > 0 {
+		n := copy(r.buf[r.end:], b)
+		r.end += n
+		return n, nil
+	}
+
+	n := copy(r.buf[r.end:], b)
+	r.end = n
+	if n < len(b) {
+		n2 := copy(r.buf, b[n:])
+		r.end = n2
+		n += n2
+	}
+	return n, nil
+}
+
+func (r *ring) Read(b []byte) (int, error) {
+	if r.Buffered() == 0 {
+		return 0, io.EOF
+	}
+
+	if r.end >= r.off {
+		// start       off       end      len(buf)
+		//   |  sfree   |  used   |  efree   |
+		n := copy(b, r.buf[r.off:])
+		r.off += n
+		r.onReadEnd()
+		return n, nil
+	}
+	// start     end       off     len(buf)
+	//   |  used  |  mfree  |  used  |
+	n := copy(b, r.buf[r.off:])
+	r.off += n
+	if n < len(b) {
+		n2 := copy(b[n:], r.buf)
+		r.off = n2
+		n += n2
+	}
+	r.onReadEnd()
+	return n, nil
+}
+
+func (r *ring) Buffered() int {
+	return len(r.buf) - r.Free()
+}
+
+func (r *ring) Free() int {
+	if r.end >= r.off {
+		// start       off       end      len(buf)
+		//   |  sfree   |  used   |  efree   |
+		startFree := r.off
+		endFree := len(r.buf) - r.end
+		return startFree + endFree
+	}
+	// start     end       off     len(buf)
+	//   |  used  |  mfree  |  used  |
+	return r.off - r.end
+}
+
+func (r *ring) midFree() int {
+	if r.end >= r.off {
+		return 0
+	}
+	return r.off - r.end
+}
+
+func (r *ring) onReadEnd() {
+	if r.off == r.end {
+		// We read everything, reset.
+		r.off = 0
+		r.end = 0
+	}
+}
diff --git a/stack/stack_test.go b/stack/stack_test.go
@@ -58,10 +58,9 @@ func TestStackEstablish(t *testing.T) {
 	if numBytesSent < expectedData {
 		t.Error("too little data exchanged", numBytesSent, " want>=", expectedData)
 	}
-	if txDone >= 4 {
+	if txDone >= 3 {
 		t.Error("too many exchanges for a 3 way handshake")
-	}
-	if txDone <= 1 {
+	} else if txDone <= 1 {
 		t.Error("too few exchanges for a 3 way handshake")
 	}
 	if clientTCP.State() != seqs.StateEstablished {
@@ -72,6 +71,54 @@ func TestStackEstablish(t *testing.T) {
 	}
 }
 
+func TestStackSendReceive(t *testing.T) {
+	const (
+		clientISS = 100
+		clientWND = 1000
+
+		serverISS = 300
+		serverWND = 1300
+	)
+
+	var (
+		macClient = [6]byte{0x01, 0x00, 0x00, 0x00, 0x00, 0x00}
+		ipClient  = netip.MustParseAddrPort("192.168.1.1:1025")
+		macServer = [6]byte{0x02, 0x00, 0x00, 0x00, 0x00, 0x00}
+		ipServer  = netip.MustParseAddrPort("192.168.1.2:80")
+	)
+
+	Client := stack.NewPortStack(stack.PortStackConfig{
+		MAC:             macClient[:],
+		IP:              ipClient.Addr(),
+		MaxOpenPortsTCP: 1,
+	})
+	clientTCP, err := stack.DialTCP(Client, ipClient.Port(), macServer, ipServer, clientISS, clientWND)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = Client.FlagTCPPending(ipClient.Port())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	Server := stack.NewPortStack(stack.PortStackConfig{
+		MAC:             macServer[:],
+		IP:              ipServer.Addr(),
+		MaxOpenPortsTCP: 1,
+	})
+	serverTCP, err := stack.ListenTCP(Server, ipServer.Port(), serverISS, serverWND)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// 3 way handshake needs2 exchanges to complete.
+	txStacks(t, 2, Client, Server)
+	if clientTCP.State() != seqs.StateEstablished || serverTCP.State() != seqs.StateEstablished {
+		t.Fatal("not established")
+	}
+
+}
+
 func isDroppedPacket(err error) bool {
 	return err != nil && (errors.Is(err, stack.ErrDroppedPacket) || strings.HasPrefix(err.Error(), "drop"))
 }