fix RTT for specific platforms

pkg/interfaces/tcp_linux.go

@@ -0,0 +1,32 @@
+//go:build linux
+// +build linux
+
+package interfaces
+
+import (
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+func platformGetRTT(fd uintptr) time.Duration {
+	var info syscall.TCPInfo
+	size := uint32(syscall.SizeofTCPInfo)
+
+	_, _, err := syscall.Syscall6(
+		syscall.SYS_GETSOCKOPT,
+		fd,
+		syscall.SOL_TCP,
+		syscall.TCP_INFO,
+		uintptr(unsafe.Pointer(&info)),
+		uintptr(unsafe.Pointer(&size)),
+		0,
+	)
+
+	if err != 0 {
+		return 0
+	}
+
+	// RTT is in microseconds, convert to Duration
+	return time.Duration(info.Rtt) * time.Microsecond
+}