agent: check command before do test_ip_tables

test_ip_tables test depends on iptables tools. But we can't
ensure these tools are exist. it's better to skip the test
if there is no such tools.

Fixes: #5697
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>

src/agent/Cargo.lock

@@ -696,6 +696,7 @@ dependencies = [
  "tracing-subscriber",
  "ttrpc",
  "vsock-exporter",
+ "which",
 ]
 
 [[package]]
@@ -2184,13 +2185,13 @@ checksum = "6a89911bd99e5f3659ec4acf9c4d93b0a90fe4a2a11f15328472058edc5261be"
 
 [[package]]
 name = "which"
-version = "4.2.5"
+version = "4.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5c4fb54e6113b6a8772ee41c3404fb0301ac79604489467e0a9ce1f3e97c24ae"
+checksum = "1c831fbbee9e129a8cf93e7747a82da9d95ba8e16621cae60ec2cdc849bacb7b"
 dependencies = [
  "either",
- "lazy_static",
  "libc",
+ "once_cell",
 ]
 
 [[package]]

src/agent/Cargo.toml

@@ -69,6 +69,7 @@ clap = { version = "3.0.1", features = ["derive"] }
 [dev-dependencies]
 tempfile = "3.1.0"
 test-utils = { path = "../libs/test-utils" }
+which = "4.3.0"
 
 [workspace]
 members = [

src/agent/src/rpc.rs

@@ -2032,6 +2032,11 @@ mod tests {
     use tempfile::{tempdir, TempDir};
     use test_utils::{assert_result, skip_if_not_root};
     use ttrpc::{r#async::TtrpcContext, MessageHeader};
+    use which::which;
+
+    fn check_command(cmd: &str) -> bool {
+        which(cmd).is_ok()
+    }
 
     fn mk_ttrpc_context() -> TtrpcContext {
         TtrpcContext {
@@ -2751,6 +2756,18 @@ OtherField:other
     async fn test_ip_tables() {
         skip_if_not_root!();
 
+        if !check_command(IPTABLES_SAVE)
+            || !check_command(IPTABLES_RESTORE)
+            || !check_command(IP6TABLES_SAVE)
+            || !check_command(IP6TABLES_RESTORE)
+        {
+            warn!(
+                sl!(),
+                "one or more commands for ip tables test are missing, skip it"
+            );
+            return;
+        }
+
         let logger = slog::Logger::root(slog::Discard, o!());
         let sandbox = Sandbox::new(&logger).unwrap();
         let agent_service = Box::new(AgentService {