Add no_security security context

Author: Johannes Draaijer

src/mac/frame/security/mod.rs

@@ -161,6 +161,8 @@ mod auxiliary_security_header;
 pub mod default;
 mod security_control;
 
+use self::default::Unimplemented;
+
 use super::{FooterMode, Frame, Header};
 use crate::mac::{Address, FrameType, FrameVersion};
 use byte::BytesExt;
@@ -275,6 +277,18 @@ where
     }
 }
 
+impl SecurityContext<Unimplemented, Unimplemented> {
+    /// A security context that is not actually capable of providing any security
+    pub fn no_security() -> Self {
+        Self {
+            euid: 0,
+            frame_counter: 0,
+            key_provider: Unimplemented {},
+            phantom_data: PhantomData,
+        }
+    }
+}
+
 fn calculate_nonce(source_addr: u64, frame_counter: u32, sec_level: SecurityLevel) -> [u8; 13] {
     let mut output = [0u8; 13];
     for i in 0..8 {