Remove impossible errors

Commit 25b5ec7 moved link address resolution out of the transport layer;
special handling of link address resolution is no longer necessary in tcp.

PiperOrigin-RevId: 351839254

3 files changed, 7 insertions, 63 deletions

diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index 9e8872fc9..6921de0f1 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -305,10 +305,7 @@ func (l *listenContext) startHandshake(s *segment, opts *header.TCPSynOptions, q
 
 	// Initialize and start the handshake.
 	h := ep.newPassiveHandshake(isn, irs, opts, deferAccept)
-	if err := h.start(); err != nil {
-		l.cleanupFailedHandshake(h)
-		return nil, err
-	}
+	h.start()
 	return h, nil
 }
 
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index f45d26a87..6cdbb8bee 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -53,7 +53,6 @@ const (
 	wakerForNotification = iota
 	wakerForNewSegment
 	wakerForResend
-	wakerForResolution
 )
 
 const (
@@ -460,9 +459,9 @@ func (h *handshake) processSegments() *tcpip.Error {
 	return nil
 }
 
-// start resolves the route if necessary and sends the first
-// SYN/SYN-ACK.
-func (h *handshake) start() *tcpip.Error {
+// start sends the first SYN/SYN-ACK. It does not block, even if link address
+// resolution is required.
+func (h *handshake) start() {
 	h.startTime = time.Now()
 	h.ep.amss = calculateAdvertisedMSS(h.ep.userMSS, h.ep.route)
 	var sackEnabled tcpip.TCPSACKEnabled
@@ -503,7 +502,6 @@ func (h *handshake) start() *tcpip.Error {
 		ack:    h.ackNum,
 		rcvWnd: h.rcvWnd,
 	}, synOpts)
-	return nil
 }
 
 // complete completes the TCP 3-way handshake initiated by h.start().
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index ddbed7e46..a4508e871 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -2325,68 +2325,17 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
 	}
 
 	if run {
-		if err := e.startMainLoop(handshake); err != nil {
-			return err
-		}
-	}
-
-	return tcpip.ErrConnectStarted
-}
-
-// startMainLoop sends the initial SYN and starts the main loop for the
-// endpoint.
-func (e *endpoint) startMainLoop(handshake bool) *tcpip.Error {
-	preloop := func() *tcpip.Error {
 		if handshake {
 			h := e.newHandshake()
 			e.setEndpointState(StateSynSent)
-			if err := h.start(); err != nil {
-				e.lastErrorMu.Lock()
-				e.lastError = err
-				e.lastErrorMu.Unlock()
-
-				e.setEndpointState(StateError)
-				e.hardError = err
-
-				// Call cleanupLocked to free up any reservations.
-				e.cleanupLocked()
-				return err
-			}
+			h.start()
 		}
 		e.stack.Stats().TCP.ActiveConnectionOpenings.Increment()
-		return nil
-	}
-
-	if e.route.IsResolutionRequired() {
-		// If the endpoint is closed between releasing e.mu and the goroutine below
-		// acquiring it, make sure that cleanup is deferred to the new goroutine.
 		e.workerRunning = true
-
-		// Sending the initial SYN may block due to route resolution; do it in a
-		// separate goroutine to avoid blocking the syscall goroutine.
-		go func() { // S/R-SAFE: will be drained before save.
-			e.mu.Lock()
-			if err := preloop(); err != nil {
-				e.workerRunning = false
-				e.mu.Unlock()
-				return
-			}
-			e.mu.Unlock()
-			_ = e.protocolMainLoop(handshake, nil)
-		}()
-		return nil
+		go e.protocolMainLoop(handshake, nil) // S/R-SAFE: will be drained before save.
 	}
 
-	// No route resolution is required, so we can send the initial SYN here without
-	// blocking. This will hopefully reduce overall latency by overlapping time
-	// spent waiting for a SYN-ACK and time spent spinning up a new goroutine
-	// for the main loop.
-	if err := preloop(); err != nil {
-		return err
-	}
-	e.workerRunning = true
-	go e.protocolMainLoop(handshake, nil) // S/R-SAFE: will be drained before save.
-	return nil
+	return tcpip.ErrConnectStarted
 }
 
 // ConnectEndpoint is not supported.