feat(test-utils): add fixture to set gw name

Adds a fixture so that we can annotate tests such that
we make sure that the gateway name is seen as set from
those tests. Sample:

    #[test]
    #[wrap(with_gw_name())]
    fn test_potato() {
        let gw_name = get_gw_name().unwrap();
        println!("Hello {gw_name}");
    }

This is Daniel's.

Signed-off-by: Fredi Raspall <[email protected]>

Author: Fredi-raspall

test-utils/src/lib.rs

@@ -4,6 +4,7 @@
 //! Testing utilities for the dataplane
 
 use caps::{CapSet, Capability};
+use gwname::set_gw_name;
 use rtnetlink::NetworkNamespace;
 use std::panic::{RefUnwindSafe, UnwindSafe, catch_unwind};
 use tracing::error;
@@ -126,6 +127,16 @@ pub fn with_caps<F: UnwindSafe + FnOnce() -> T, T>(
     }
 }
 
+/// Fixture which sets the static gateway name to a known value common to all tests.
+pub fn with_gw_name<F: FnOnce() -> T, T>() -> impl FnOnce(F) -> T {
+    move |f: F| {
+        const TEST_GW_NAME: &str = "test-gw";
+        println!("Setting gateway name to {TEST_GW_NAME}");
+        set_gw_name(TEST_GW_NAME).unwrap();
+        f()
+    }
+}
+
 /// Run an (async) function or closure in another network namespace.
 ///
 /// This method will spawn a new thread and create a thread local tokio runtime to execute the