feat(s2n-quic-core): add null TLS provider for testing (#1834)

quic/s2n-quic-core/src/application/mod.rs

@@ -3,7 +3,7 @@
 
 pub mod error;
 #[cfg(feature = "alloc")]
-mod server_name;
+pub(crate) mod server_name;
 
 pub use error::Error;
 #[cfg(feature = "alloc")]

quic/s2n-quic-core/src/application/server_name.rs

@@ -23,9 +23,13 @@ use bytes::Bytes;
 /// - It can be converted into [`Bytes`] which supports zero-copy slicing and
 /// reference counting.
 /// - It can be accessed as `&str` so that applications can reason about the string value.
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub struct ServerName(Bytes);
 
+/// A static value for localhost
+#[allow(dead_code)] // this is used by conditional modules so don't warn
+pub(crate) static LOCALHOST: ServerName = ServerName(Bytes::from_static(b"localhost"));
+
 impl ServerName {
     #[inline]
     pub fn into_bytes(self) -> Bytes {

quic/s2n-quic-core/src/crypto/tls.rs

@@ -9,6 +9,9 @@ use zerocopy::{AsBytes, FromBytes, Unaligned};
 #[cfg(any(test, feature = "testing"))]
 pub mod testing;
 
+#[cfg(all(feature = "alloc", any(test, feature = "testing")))]
+pub mod null;
+
 /// Holds all application parameters which are exchanged within the TLS handshake.
 #[derive(Debug)]
 pub struct ApplicationParameters<'a> {