Add gossipsub as a Lighthouse behaviour (#5066)

* Move gossipsub as a lighthouse behaviour

* Update dependencies, pin to corrected libp2p version

* Merge latest unstable

* Fix test

* Remove unused dep

* Fix cargo.lock

* Re-order behaviour, pin upstream libp2p

* Pin discv5 to latest version

beacon_node/lighthouse_network/src/gossipsub/transform.rs

@@ -0,0 +1,72 @@
+// Copyright 2020 Sigma Prime Pty Ltd.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+//! This trait allows of extended user-level decoding that can apply to message-data before a
+//! message-id is calculated.
+//!
+//! This is primarily designed to allow applications to implement their own custom compression
+//! algorithms that can be topic-specific. Once the raw data is transformed the message-id is then
+//! calculated, allowing for applications to employ message-id functions post compression.
+
+use crate::gossipsub::{Message, RawMessage, TopicHash};
+
+/// A general trait of transforming a [`RawMessage`] into a [`Message`]. The
+/// [`RawMessage`] is obtained from the wire and the [`Message`] is used to
+/// calculate the [`crate::gossipsub::MessageId`] of the message and is what is sent to the application.
+///
+/// The inbound/outbound transforms must be inverses. Applying the inbound transform and then the
+/// outbound transform MUST leave the underlying data un-modified.
+///
+/// By default, this is the identity transform for all fields in [`Message`].
+pub trait DataTransform {
+    /// Takes a [`RawMessage`] received and converts it to a [`Message`].
+    fn inbound_transform(&self, raw_message: RawMessage) -> Result<Message, std::io::Error>;
+
+    /// Takes the data to be published (a topic and associated data) transforms the data. The
+    /// transformed data will then be used to create a [`crate::gossipsub::RawMessage`] to be sent to peers.
+    fn outbound_transform(
+        &self,
+        topic: &TopicHash,
+        data: Vec<u8>,
+    ) -> Result<Vec<u8>, std::io::Error>;
+}
+
+/// The default transform, the raw data is propagated as is to the application layer gossipsub.
+#[derive(Default, Clone)]
+pub struct IdentityTransform;
+
+impl DataTransform for IdentityTransform {
+    fn inbound_transform(&self, raw_message: RawMessage) -> Result<Message, std::io::Error> {
+        Ok(Message {
+            source: raw_message.source,
+            data: raw_message.data,
+            sequence_number: raw_message.sequence_number,
+            topic: raw_message.topic,
+        })
+    }
+
+    fn outbound_transform(
+        &self,
+        _topic: &TopicHash,
+        data: Vec<u8>,
+    ) -> Result<Vec<u8>, std::io::Error> {
+        Ok(data)
+    }
+}