chore: import upstream snapshot with attribution

examples/k8s_resolver_check.rs

@@ -0,0 +1,54 @@
+//! Smoke-test binary: takes a PID on the command line, runs the Kubernetes
+//! resolver against `/proc/<pid>/cgroup`, and prints the resolver's view.
+//! Intended for running inside a `hostPID: true` pod on a Kubernetes node:
+//!
+//!     cargo build --release --features kubernetes --example k8s_resolver_check
+//!     ./k8s_resolver_check $(pidof nginx | awk '{print $1}')
+
+#[cfg(feature = "kubernetes")]
+fn main() {
+    let pid: u32 = std::env::args()
+        .nth(1)
+        .expect("usage: k8s_resolver_check <pid>")
+        .parse()
+        .expect("PID must be an integer");
+
+    let path = format!("/proc/{pid}/cgroup");
+    let raw = std::fs::read_to_string(&path).unwrap_or_else(|e| {
+        eprintln!("read {path}: {e}");
+        std::process::exit(2);
+    });
+    println!("--- /proc/{pid}/cgroup ---");
+    println!("{raw}");
+
+    let resolver = rustnet_monitor::network::kubernetes::KubernetesResolver::new();
+    match resolver.enrich(pid) {
+        Some(info) => {
+            println!("--- resolver output ---");
+            println!("{info:#?}");
+            // Mirror the JSON shape that log_connection_event would emit.
+            let mut obj = serde_json::Map::new();
+            if let Some(v) = info.pod_uid {
+                obj.insert("pod_uid".into(), serde_json::json!(v));
+            }
+            if let Some(v) = info.container_id {
+                obj.insert("container_id".into(), serde_json::json!(v));
+            }
+            if let Some(v) = info.cgroup_path {
+                obj.insert("cgroup_path".into(), serde_json::json!(v));
+            }
+            println!("--- JSONL 'kubernetes' block ---");
+            println!("{}", serde_json::to_string(&obj).unwrap());
+        }
+        None => {
+            println!("--- resolver returned None (no kubepods cgroup) ---");
+            std::process::exit(1);
+        }
+    }
+}
+
+#[cfg(not(feature = "kubernetes"))]
+fn main() {
+    eprintln!("Build with --features kubernetes");
+    std::process::exit(2);
+}