Initial fork versioning (#934)

* Merge #913

* Correct release tests

* Completed release test corrections

* Initial work on upgrading discovery

* Updates discovery to latest version

* Update ENR initialisation logic

* Remove debug statements

* Shifts timing units to slots

* Initial work

* Add initial fork versioning and EnrForkId

* Correct linking for EnrForkId

eth2/types/src/enr_fork_id.rs

@@ -0,0 +1,36 @@
+use crate::test_utils::TestRandom;
+use crate::utils::{fork_from_hex_str, fork_to_hex_str};
+use crate::Epoch;
+
+use serde_derive::{Deserialize, Serialize};
+use ssz_derive::{Decode, Encode};
+use test_random_derive::TestRandom;
+use tree_hash_derive::TreeHash;
+
+/// Specifies a fork which allows nodes to identify each other on the network. This fork is used in
+/// a nodes local ENR.
+///
+/// Spec v0.11
+#[derive(
+    Debug, Clone, PartialEq, Default, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom,
+)]
+pub struct EnrForkId {
+    #[serde(
+        serialize_with = "fork_to_hex_str",
+        deserialize_with = "fork_from_hex_str"
+    )]
+    pub fork_digest: [u8; 4],
+    #[serde(
+        serialize_with = "fork_to_hex_str",
+        deserialize_with = "fork_from_hex_str"
+    )]
+    pub next_fork_version: [u8; 4],
+    pub next_fork_epoch: Epoch,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    ssz_and_tree_hash_tests!(EnrForkId);
+}

eth2/types/src/lib.rs

@@ -21,6 +21,7 @@ pub mod checkpoint;
 pub mod deposit;
 pub mod deposit_data;
 pub mod deposit_message;
+pub mod enr_fork_id;
 pub mod eth1_data;
 pub mod eth_spec;
 pub mod fork;
@@ -60,6 +61,7 @@ pub use crate::checkpoint::Checkpoint;
 pub use crate::deposit::{Deposit, DEPOSIT_TREE_DEPTH};
 pub use crate::deposit_data::DepositData;
 pub use crate::deposit_message::DepositMessage;
+pub use crate::enr_fork_id::EnrForkId;
 pub use crate::eth1_data::Eth1Data;
 pub use crate::fork::Fork;
 pub use crate::free_attestation::FreeAttestation;
@@ -72,7 +74,7 @@ pub use crate::signed_beacon_block::SignedBeaconBlock;
 pub use crate::signed_beacon_block_header::SignedBeaconBlockHeader;
 pub use crate::signed_voluntary_exit::SignedVoluntaryExit;
 pub use crate::signing_root::{SignedRoot, SigningRoot};
-pub use crate::slot_epoch::{Epoch, Slot};
+pub use crate::slot_epoch::{Epoch, Slot, FAR_FUTURE_EPOCH};
 pub use crate::subnet_id::SubnetId;
 pub use crate::validator::Validator;
 pub use crate::voluntary_exit::VoluntaryExit;

eth2/types/src/slot_epoch.rs

@@ -22,6 +22,8 @@ use std::hash::{Hash, Hasher};
 use std::iter::Iterator;
 use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Rem, Sub, SubAssign};
 
+pub const FAR_FUTURE_EPOCH: Epoch = Epoch(u64::max_value());
+
 #[derive(Eq, Debug, Clone, Copy, Default, Serialize, Deserialize)]
 #[serde(transparent)]
 pub struct Slot(u64);