runtime-rs: add validate method and refine the new method

We need first do validate the QmpSocket fields and make
them valid. And we'll pass QMP socket fd to Qemu cmdline
when launching qemu process.

Fixes: kata-containers#9603

Signed-off-by: Alex Lyn <alex.lyn@antgroup.com>

src/runtime-rs/crates/hypervisor/src/qemu/cmdline_generator.rs

@@ -8,10 +8,12 @@ use crate::{kernel_param::KernelParams, Address, HypervisorConfig};
 
 use anyhow::{anyhow, Context, Result};
 use async_trait::async_trait;
+use kata_types::config::KATA_PATH;
 use std::collections::HashMap;
 use std::fmt::Display;
 use std::fs::{read_to_string, File};
-use std::os::fd::AsRawFd;
+use std::os::fd::{AsRawFd, FromRawFd, IntoRawFd};
+use std::os::unix::net::UnixListener;
 use tokio;
 
 // These should have been called MiB and GiB for better readability but the
@@ -1238,16 +1240,44 @@ pub struct QmpSocket {
 }
 
 impl QmpSocket {
-    fn new(_sid: &str) -> Result<Self> {
+    fn new(sid: &str) -> Result<Self> {
+        let sock_path = [KATA_PATH, sid, QMP_SOCKET_FILE].join("/");
+        let listener = UnixListener::bind(sock_path).context("unix listener bind failed.")?;
+
+        let raw_fd = listener.into_raw_fd();
+        clear_cloexec(raw_fd).context("clearing unix listenser O_CLOEXEC failed")?;
+        let sock_file = unsafe { File::from_raw_fd(raw_fd) };
+
         Ok(QmpSocket {
             socket_type: QMP_SOCKET_TYPE.to_owned(),
             protocol: MonitorProtocol::new("qmp"),
-            fd: None,
+            fd: Some(sock_file),
             name: QMP_SOCKET_FILE.to_owned(),
             server: true,
             nowait: true,
         })
     }
+
+    // validate returns true if the QmpSocket structure is valid and complete.
+    #[allow(dead_code)]
+    fn validate(&self) -> bool {
+        if self.socket_type.as_str() != QMP_SOCKET_TYPE {
+            return false;
+        }
+
+        if self.name.is_empty() && self.fd.is_none() {
+            return false;
+        }
+
+        if self.protocol != MonitorProtocol::Hmp
+            && self.protocol != MonitorProtocol::Qmp
+            && self.protocol != MonitorProtocol::QmpPretty
+        {
+            return false;
+        }
+
+        true
+    }
 }
 
 #[async_trait]