tests: send SIGTERM to kill GuestCommand

Killing CLH by SIGKILL will cause inaccurate code coverage
 information. This patch changes the signal to SIGTERM.

Fixes: #6507

Signed-off-by: Songqian Li <sionli@tencent.com>

test_infra/Cargo.toml

@@ -8,6 +8,7 @@ version = "0.1.0"
 dirs = "5.0.1"
 epoll = "4.3.3"
 libc = "0.2.153"
+nix = { version = "0.29.0", features = ["signal"] }
 once_cell = "1.19.0"
 serde = { version = "1.0.197", features = ["rc", "derive"] }
 serde_json = "1.0.115"

test_infra/src/lib.rs

@@ -5,6 +5,8 @@
 
 #![allow(clippy::undocumented_unsafe_blocks)]
 
+use nix::sys::signal::{kill, Signal};
+use nix::unistd::Pid;
 use once_cell::sync::Lazy;
 use serde_json::Value;
 use ssh2::Session;
@@ -798,6 +800,22 @@ pub fn check_matched_lines_count(input: &str, keywords: Vec<&str>, line_count: u
     }
 }
 
+pub fn kill_child(child: &Child) {
+    let pid = Pid::from_raw(child.id() as i32);
+    match kill(pid, Signal::SIGTERM) {
+        Ok(_) => {}
+        Err(e) => {
+            eprintln!("Failed to kill child with SIGTERM: {:?}", e);
+            kill(pid, Signal::SIGKILL)
+                .map_err(|e| {
+                    eprintln!("Failed to kill child with SIGKILL: {:?}", e);
+                    e
+                })
+                .unwrap();
+        }
+    }
+}
+
 pub const PIPE_SIZE: i32 = 32 << 20;
 
 static NEXT_VM_ID: Lazy<Mutex<u8>> = Lazy::new(|| Mutex::new(1));