Allow access to a Connection's boring::ssl::SslRef

We would like to modify extension data in an SslRef to
support async callbacks. To do so we need access to a
Connection's `SslRef`.

quiche/src/lib.rs

@@ -7438,6 +7438,13 @@ impl Connection {
     }
 }
 
+#[cfg(feature = "boringssl-boring-crate")]
+impl AsMut<boring::ssl::SslRef> for Connection {
+    fn as_mut(&mut self) -> &mut boring::ssl::SslRef {
+        self.handshake.ssl_mut()
+    }
+}
+
 /// Maps an `Error` to `Error::Done`, or itself.
 ///
 /// When a received packet that hasn't yet been authenticated triggers a failure

quiche/src/tls.rs

@@ -898,6 +898,13 @@ impl Handshake {
             }
         }
     }
+
+    #[cfg(feature = "boringssl-boring-crate")]
+    pub(crate) fn ssl_mut(&mut self) -> &mut boring::ssl::SslRef {
+        use foreign_types_shared::ForeignTypeRef;
+
+        unsafe { boring::ssl::SslRef::from_ptr_mut(self.as_mut_ptr() as _ ) }
+    }
 }
 
 // NOTE: These traits are not automatically implemented for Handshake due to the