Revert "fix: detect JetBrains running on local ipv6 (#11653)" (#11664)

This reverts commit 2d61d5332a.

agent/agent_test.go

@@ -214,59 +214,46 @@ func TestAgent_Stats_Magic(t *testing.T) {
 		_, b, _, ok := runtime.Caller(0)
 		require.True(t, ok)
 		dir := filepath.Join(filepath.Dir(b), "../scripts/echoserver/main.go")
+		echoServerCmd := exec.Command("go", "run", dir,
+			"-D", agentssh.MagicProcessCmdlineJetBrains)
+		stdout, err := echoServerCmd.StdoutPipe()
+		require.NoError(t, err)
+		err = echoServerCmd.Start()
+		require.NoError(t, err)
+		defer echoServerCmd.Process.Kill()
 
-		spawnServer := func(network string) (string, *exec.Cmd) {
-			echoServerCmd := exec.Command("go", "run", dir,
-				network, "-D", agentssh.MagicProcessCmdlineJetBrains)
-			stdout, err := echoServerCmd.StdoutPipe()
-			require.NoError(t, err)
-			err = echoServerCmd.Start()
-			require.NoError(t, err)
-			t.Cleanup(func() {
-				echoServerCmd.Process.Kill()
-			})
-
-			// The echo server prints its port as the first line.
-			sc := bufio.NewScanner(stdout)
-			sc.Scan()
-			return sc.Text(), echoServerCmd
-		}
-
-		port4, cmd4 := spawnServer("tcp4")
-		port6, cmd6 := spawnServer("tcp6")
+		// The echo server prints its port as the first line.
+		sc := bufio.NewScanner(stdout)
+		sc.Scan()
+		remotePort := sc.Text()
 
 		//nolint:dogsled
 		conn, _, stats, _, _ := setupAgent(t, agentsdk.Manifest{}, 0)
-		defer conn.Close()
-
 		sshClient, err := conn.SSHClient(ctx)
 		require.NoError(t, err)
 
-		tunnel4, err := sshClient.Dial("tcp4", fmt.Sprintf("127.0.0.1:%s", port4))
+		tunneledConn, err := sshClient.Dial("tcp", fmt.Sprintf("127.0.0.1:%s", remotePort))
 		require.NoError(t, err)
-		defer tunnel4.Close()
-
-		tunnel6, err := sshClient.Dial("tcp6", fmt.Sprintf("[::]:%s", port6))
-		require.NoError(t, err)
-		defer tunnel6.Close()
+		t.Cleanup(func() {
+			// always close on failure of test
+			_ = conn.Close()
+			_ = tunneledConn.Close()
+		})
 
 		require.Eventuallyf(t, func() bool {
 			s, ok := <-stats
 			t.Logf("got stats with conn open: ok=%t, ConnectionCount=%d, SessionCountJetBrains=%d",
 				ok, s.ConnectionCount, s.SessionCountJetBrains)
 			return ok && s.ConnectionCount > 0 &&
-				s.SessionCountJetBrains == 2
+				s.SessionCountJetBrains == 1
 		}, testutil.WaitLong, testutil.IntervalFast,
 			"never saw stats with conn open",
 		)
 
 		// Kill the server and connection after checking for the echo.
-		requireEcho(t, tunnel4)
-		requireEcho(t, tunnel6)
-		_ = cmd4.Process.Kill()
-		_ = cmd6.Process.Kill()
-		_ = tunnel4.Close()
-		_ = tunnel6.Close()
+		requireEcho(t, tunneledConn)
+		_ = echoServerCmd.Process.Kill()
+		_ = tunneledConn.Close()
 
 		require.Eventuallyf(t, func() bool {
 			s, ok := <-stats

agent/agentssh/portinspection_supported.go

@@ -3,7 +3,6 @@
 package agentssh
 
 import (
-	"errors"
 	"fmt"
 	"os"
 
@@ -12,33 +11,24 @@ import (
 )
 
 func getListeningPortProcessCmdline(port uint32) (string, error) {
-	acceptFn := func(s *netstat.SockTabEntry) bool {
+	tabs, err := netstat.TCPSocks(func(s *netstat.SockTabEntry) bool {
 		return s.LocalAddr != nil && uint32(s.LocalAddr.Port) == port
+	})
+	if err != nil {
+		return "", xerrors.Errorf("inspect port %d: %w", port, err)
 	}
-	tabs, err := netstat.TCPSocks(acceptFn)
-	tabs6, err6 := netstat.TCP6Socks(acceptFn)
-
-	// Only return the error if the other method found nothing.
-	if (err != nil && len(tabs6) == 0) || (err6 != nil && len(tabs) == 0) {
-		return "", xerrors.Errorf("inspect port %d: %w", port, errors.Join(err, err6))
+	if len(tabs) == 0 {
+		return "", nil
 	}
 
-	var proc *netstat.Process
-	if len(tabs) > 0 {
-		proc = tabs[0].Process
-	} else if len(tabs6) > 0 {
-		proc = tabs6[0].Process
-	}
-	if proc == nil {
-		// Either nothing is listening on this port or we were unable to read the
-		// process details (permission issues reading /proc/$pid/* potentially).
-		// Or, perhaps /proc/net/tcp{,6} is not listing the port for some reason.
+	// Defensive check.
+	if tabs[0].Process == nil {
 		return "", nil
 	}
 
 	// The process name provided by go-netstat does not include the full command
 	// line so grab that instead.
-	pid := proc.Pid
+	pid := tabs[0].Process.Pid
 	data, err := os.ReadFile(fmt.Sprintf("/proc/%d/cmdline", pid))
 	if err != nil {
 		return "", xerrors.Errorf("read /proc/%d/cmdline: %w", pid, err)

scripts/echoserver/main.go

@@ -9,21 +9,10 @@ import (
 	"io"
 	"log"
 	"net"
-	"os"
 )
 
 func main() {
-	network := os.Args[1]
-	var address string
-	switch network {
-	case "tcp4":
-		address = "127.0.0.1"
-	case "tcp6":
-		address = "[::]"
-	default:
-		log.Fatalf("invalid network: %s", network)
-	}
-	l, err := net.Listen(network, address+":0")
+	l, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
 		log.Fatalf("listen error: err=%s", err)
 	}