fix: detect JetBrains running on local ipv6 (#11676)

agent/agentssh/portinspection_supported.go

@@ -3,6 +3,7 @@
 package agentssh
 
 import (
+	"errors"
 	"fmt"
 	"os"
 
@@ -11,24 +12,37 @@ import (
 )
 
 func getListeningPortProcessCmdline(port uint32) (string, error) {
-	tabs, err := netstat.TCPSocks(func(s *netstat.SockTabEntry) bool {
+	acceptFn := 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)
 	}
-	if len(tabs) == 0 {
-		return "", nil
+	tabs4, err4 := netstat.TCPSocks(acceptFn)
+	tabs6, err6 := netstat.TCP6Socks(acceptFn)
+
+	// In the common case, we want to check ipv4 listening addresses.  If this
+	// fails, we should return an error.  We also need to check ipv6.  The
+	// assumption is, if we have an err4, and 0 ipv6 addresses listed, then we are
+	// interested in the err4 (and vice versa).  So return both errors (at least 1
+	// is non-nil) if the other list is empty.
+	if (err4 != nil && len(tabs6) == 0) || (err6 != nil && len(tabs4) == 0) {
+		return "", xerrors.Errorf("inspect port %d: %w", port, errors.Join(err4, err6))
 	}
 
-	// Defensive check.
-	if tabs[0].Process == nil {
+	var proc *netstat.Process
+	if len(tabs4) > 0 {
+		proc = tabs4[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.
 		return "", nil
 	}
 
 	// The process name provided by go-netstat does not include the full command
 	// line so grab that instead.
-	pid := tabs[0].Process.Pid
+	pid := proc.Pid
 	data, err := os.ReadFile(fmt.Sprintf("/proc/%d/cmdline", pid))
 	if err != nil {
 		return "", xerrors.Errorf("read /proc/%d/cmdline: %w", pid, err)